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I was studying about parental care behavior. There seems a pattern present in this behavior in case of vertebrates. The more evolutionary advanced class the animal belongs to, the greater effort an animal gives to care its off spring?
Is it a real pattern?
My current thinking is that if the pattern is indeed real, it is because the more complex an animal is, it takes more time to get fit with the environment, so it takes more effort for parents to get them ready for the environment. Am I close?
Animal Behavior - Raising Offspring
Do you ever wonder why your parents worry so much about you? Why do they get angry when you do fun things like skateboard in the street and ride shopping carts down hills? Well, they would say its because they love you and just want to protect you. That may be true, but subconsciously, they really just want you to survive so you can pass on their genes. It is not their fault, exactly—it is their genes talking.
You and any siblings you have are the only descendants of your parents, and therefore the only ones that can keep the genetic line alive. Since your parents have invested a lot of time in raising you already, they want to keep you alive and are going to try to control that as much as possible. If you were a cockroach, your parents wouldn’t care so much since they would have tons of offspring. They probably wouldn’t even remember your name. See, you don’t have it so bad after all.
Different animals invest different amounts of effort into raising their offspring. Animals that make lots and lots of babies, like many insects, fish, and reptiles, usually do not exhibit much parental care. Many of these animals do not have high survival rates as babies. For example, sea turtles lay 1000 eggs but only 1 out of 1000 baby sea turtles will survive past the first few weeks of life. Predatory sea birds and other ocean life will claim the lives of the other ones. Sea turtles have high mortality, or death rate, early in life. Animals that live like this—making lots of offspring with high risk of dying—are called r-selected. This means their lives emphasize reproduction over ensuring that their offspring survive. If they make enough babies, at least a few will survive. This type of reproductive strategy is useful in unstable environments, where food is possibly scarce and conditions might change quickly.
Sea turtle eggs. There are more where those came from.
In contrast to r-selected species, some animals have only one or two babies at a time, and then take care of the babies until they are old enough to live on their own. This is called parental care basically, one or both parents care for the offspring. Humans and elephants use this strategy, which has a much higher rate of survival of offspring. In this situation, most mortality occurs later in life. In human society, old people die a lot more frequently than young people. This type of reproductive strategy, where parents produce a few offspring and have a lot of parental care, is called K-selected. K-selected species typically live in stable environments.
The point of all this is that some animals invest a lot of time and energy in raising offspring, and some animals are on their own from birth. If you are dealing with an animal that does exhibit parental care, you do NOT want to get in between a mother and her baby. This is especially critical if the animal has claws and sharp teeth, like a bear or crocodile. Crocodiles are unusual reptiles because the mother takes care of her babies.
Killer whales are mama’s boys. Male orcas whose mothers die, even when the male is fully-grown, are much more likely to die in the following year than orcas with living mothers. The daughters of killer whales do not need their mothers around in the same way, and do not show the same pattern.
Mothers' behavior influences bonding hormone oxytocin in babies
Oxytocin is an extremely important hormone, involved in social interaction and bonding in mammals, including humans. It helps us relate to others. It strengthens trust, closeness in relationships, and can be triggered by eye contact, empathy, or pleasant touch. It's well known that a new mother's oxytocin levels can influence her behavior and as a result, the bond she makes with her baby. A new epigenetic study by Kathleen Krol and Jessica Connelly from the University of Virginia and Tobias Grossmann from the Max Planck Institute for Human Cognitive and Brain Sciences now suggests that mothers' behavior can also have a substantial impact on their children's developing oxytocin systems.
Childhood marks a dynamic and malleable phase of postnatal development. Many bodily systems are coming online, maturing, or getting tweaked, often setting our psychological and behavioral trajectories well into adulthood. Nature plays an obvious role, shaping us through our genes. But we are also heavily influenced by our interactions, with other people and with our environment. "It is well known that oxytocin is actively involved in early social, perceptual, and cognitive processes, and, that it influences complex social behaviors," says Tobias Grossmann. "However, in this study we ask whether the mother's behavior might also have a decisive influence on the development of the baby's oxytocin system itself. Advances in molecular biology, epigenetics in particular, have recently made it possible to investigate the interaction of nature and nurture, in this case infant care, in fine detail. That is exactly what we've done here."
The scientists observed a free play interaction between mothers and their five-month-old children. "We collected saliva samples from both the mother and the infant during the visit and then a year later, when the child was 18 months old. We were interested in exploring whether the involvement of the mother, in the original play session, would have an influence on the oxytocin receptor gene of the child, a year later. The oxytocin receptor is essential for the hormone oxytocin to exert its effects and the gene can determine how many are produced," explains Kathleen Krol, a Hartwell postdoctoral fellow in Connelly's Lab at the University of Virginia who conducted the study together with Tobias Grossmann at MPI CBS in Leipzig.
"We found that epigenetic changes had occurred in infant's DNA, and that this change was predicted by the quality of the mother's involvement in the play session. If mothers were particularly involved in the game with their children, there was a greater reduction in DNA methylation of the oxytocin receptor gene one year later. Decreased DNA methylation in this region has previously been associated with increased expression of the oxytocin receptor gene. Thus, greater maternal involvement seems to have the potential to upregulate the oxytocin system in human offspring," explains the scientist. "Importantly, we also found that the DNA methylation levels reflected infant temperament, which was reported to us by the parents. The children with higher methylation levels at 18-months, and presumably lower levels of oxytocin receptor, were also more temperamental and less well balanced."
The results of this study provide a striking example of how we are not simply bound by our genes but are rather the products of a delicate interplay between our blue prints and experiences. Early social interaction with our caregivers, certainly not excluding fathers, can influence our biological and psychological development through epigenetic changes to the oxytocin system. These and related findings highlight the importance of parenting in promoting cross-generational health.
Survivorship curve type 2
Organisms with a type two survivorship curve show s moderate changes with nearly uniform death rates thought out the life. This type of curve is generally shown by organisms that live under continuous predator pressure. Individuals are lost mostly due to accidents and predation. The species with type II survivorship curve includes small mammals, many birds, and some annual plants as well. The individuals in this type of curve are not born as fit as type I nor as fragile as type III survivorship curve.
The numbers of progeny produce are moderate and not as large as the type III survivorship curve showing individuals.
What are the examples of survivorship curve 2
Examples of Type II survivorship curve are butterfly ( important for CSIR NET EXAM), birds, mice, rabbits, and most of the holometabolous insects (in case if you don’t know: Holometabolism, also called complete metamorphosis, is a form of insect development which includes four life stages: egg, larva, pupa, and imago or adult.)
Pattern in parental care behaviour from lower to higher animals? - Biology
Animal behavior is the bridge between the molecular and physiological aspects of biology and the ecological. Behavior is the link between organisms and environment and between the nervous system, and the ecosystem. Behavior is one of the most important properties of animal life. Behavior plays a critical role in biological adaptations. Behavior is how we humans define our own lives. Behavior is that part of an organism by which it interacts with its environment. Behavior is as much a part of an organisms as its coat, wings etc. The beauty of an animal includes its behavioral attributes.
For the same reasons that we study the universe and subatomic particles there is intrinsic interest in the study of animals. In view of the amount of time that television devotes to animal films and the amount of money that people spend on nature books there is much more public interest in animal behavior than in neutrons and neurons. If human curiosity drives research, then animal behavior should be near the top of our priorities.
Research on animal behavior and behavioral ecology has been burgeoning in recent years despite below inflation increases (and often decreases) in research funding. Two of our journals Animal Behaviour and Behavior Ecology and Sociobiology rank in the top six behavioral science AND zoological journals in terms of impact as measured by the Science Citation Index. From 1985 to 1990 Animal Behaviour has grown from quarterly to monthly publication and its page budget has more than doubled. Many related journals have increased their size and frequency of publication in the same period. Ours is an active and vital field.
While the study of animal behavior is important as a scientific field on its own, our science has made important contributions to other disciplines with applications to the study of human behavior, to the neurosciences, to the environment and resource management, to the study of animal welfare and to the education of future generations of scientists.
A. ANIMAL BEHAVIOR AND HUMAN SOCIETY
- Many problems in human society are often related to the interaction of environment and behavior or genetics and behavior. The fields of socioecology and animal behavior deal with the issue of environment behavioral interactions both at an evolutionary level and a proximate level. Increasingly social scientists are turning to animal behavior as a framework in which to interpret human society and to understand possible causes of societal problems. (e.g. Daly and Wilson's book on human homicide is based on an evolutionary analysis from animal research. Many studies on child abuse utilize theory and data from studies on infanticide in animals.)
- Research by de Waal on chimpanzees and monkeys has illustrated the importance of cooperation and reconciliation in social groups. This work provides new perspectives by which to view and ameliorate aggressive behavior among human beings.
- The methodology applied to study animal behavior has had a tremendous impact in psychology and the social sciences. Jean Piaget began his career with the study of snails, and he extended the use of careful behavioral observations and descriptions to his landmark studies on human cognitive development. J. B. Watson began his study of behavior by observing gulls. Aspects of experimental design, observation techniques, attention to nonverbal communication signals were often developed in animal behavior studies before their application to studies of human behavior. The behavioral study of humans would be much diminished today without the influence of animal research.
- Charles Darwin's work on emotional expression in animals has had an important influence on many psychologists, such as Paul Ekman, who study human emotional behavior.
- Harry Harlow's work on social development in rhesus monkeys has been of major importance to theories of child development and to psychiatry. The work of Overmier, Maier and Seligman on learned helplessness has had a similar effect on child development and psychiatry.
- The comparative study of behavior over a wide range of species can provide insights into influences affecting human behavior. For example, the woolly spider monkey in Brazil displays no overt aggressive behavior among group members. We might learn how to minimize human aggression if we understood how this species of monkey avoids aggression. If we want to have human fathers be more involved in infant care, we can study the conditions under which paternal care has appeared in other species like the California mouse or in marmosets and tamarins. Studies of various models of the ontogeny of communication in birds and mammals have had direct influence on the development of theories and the research directions in the study of child language. The richness of developmental processes in behavior, including multiple sources and the consequences of experience are significant in understanding processes of human development.
- Understanding the differences in adaptability between species that can live in a variety of habitats versus those that are restricted to limited habitats can lead to an understanding of how we might improve human adaptability as our environments change.
- Research by animal behaviorists on animal sensory systems has led to practical applications for extending human sensory systems. Griffin's demonstrations on how bats use sonar to locate objects has led directly to the use of sonar techniques in a wide array of applications from the military to fetal diagnostics.
- Studies of chimpanzees using language analogues have led to new technology (computer keyboards using arbitrary symbols) that have been applied successfully to teaching language to disadvantaged human populations.
- Basic research on circadian and other endogenous rhythms in animals has led to research relevant to human factors and productivity in areas such as coping with jet-lag or changing from one shift to another.
- Research on animals has developed many of the important concepts relating to coping with stress, for example studies of the importance of prediction and control on coping behavior.
B. ANIMAL BEHAVIOR AND NEUROBIOLOGY
- Sir Charles Sherrington, an early Nobel Prize winner, developed a model for the structure and function of the nervous system based only on close behavioral observation and deduction. Seventy years of subsequent neurobiological research has completely supported the inferences Sherrington made from behavioral observation.
- Neuroethology, the integration of animal behavior and the neurosciences, provides important frameworks for hypothesizing neural mechanisms. Careful behavioral data allow neurobiologists to narrow the scope of their studies and to focus on relevant input stimuli and attend to relevant responses. In many case the use of species specific natural stimuli has led to new insights about neural structure and function that contrast with results obtained using non-relevant stimuli.
- Recent work in animal behavior has demonstrated a downward influence of behavior and social organization on physiological and cellular processes. Variations in social environment can inhibit or stimulate ovulation, produce menstrual synchrony, induce miscarriages and so on. Other animal studies show that the quality of the social and behavioral environment have a direct effect on immune system functioning. Researchers in physiology and immunology need to be guided by these behavioral and social influences to properly control their own studies.
C. ANIMAL BEHAVIOR AND THE ENVIRONMENT, CONSERVATION AND RESOURCE MANAGEMENT
- The behavior of animals often provides the first clues or early warning signs of environmental degradation. Changes in sexual and other behavior occur much sooner and at lower levels of environmental disruption than changes in reproductive outcomes and population size. If we wait to see if numbers of animal populations are declining, it may be too late to take measures to save the environment. Studies of natural behavior in the field are vital to provide baseline data for future environmental monitoring. For example, the Environmental Protection Agency uses disruptions in swimming behavior of minnows as an index of possible pesticide pollution.
- Basic research on how salmon migrate back to their home streams started more than 40 years ago by Arthur Hasler has taught us much about the mechanisms of migration. This information has also been valuable in preserving the salmon industry in the Pacific Northwest and applications of Hasler's results has led to the development of a salmon fishing industry in the Great Lakes. Basic animal behavior research can have important economic implications.
- Animal behaviorists have described variables involved in insect reproduction and host plant location leading to the development of non-toxic pheromones for insect pest control that avoid the need for toxic pesticides. Understanding of predator prey relationships can lead to the introduction of natural predators on prey species.
- Knowledge of honeybee foraging behavior can be applied to mechanisms of pollination which in turn is important for plant breeding and propagation.
- An understanding of foraging behavior in animals can lead to an understanding of forest regeneration. Many animals serve as seed dispersers and are thus essential for the propagation of tree species and essential for habitat preservation.
- The conservation of endangered species requires that we know enough about natural behavior (migratory patterns, home range size, interactions with other groups, foraging demands, reproductive behavior, communication, etc) in order to develop effective reserves and effective protection measures. Relocation or reintroduction of animals (such as the golden lion tamarin) is not possible without detailed knowledge of a species' natural history. With the increasing importance of environmental programs and human management of populations of rare species, both in captivity and in the natural habitat, animal behavior research becomes increasingly important. Many of the world's leading conservationists have a background in animal behavior or behavioral ecology.
- Basic behavioral studies on reproductive behavior have led to improved captive breeding methods for whooping cranes, golden lion tamarins, cotton-top tamarins, and many other endangered species. Captive breeders who were ignorant of the species' natural reproductive behavior were generally unsuccessful.
D. ANIMAL BEHAVIOR AND ANIMAL WELFARE
- Our society has placed increased emphasis on the welfare of research and exhibit animals. US law now requires attending to exercise requirements for dogs and the psychological well-being of nonhuman primates. Animal welfare without knowledge is impossible. Animal behavior researchers look at the behavior and well-being of animals in lab and field. We have provided expert testimony to bring about reasonable and effective standards for the care and well-being of research animals.
- Further developments in animal welfare will require input from animal behavior specialists. Improved conditions for farm animals, breeding of endangered species, proper care of companion animals all require a strong behavioral data base.
E. ANIMAL BEHAVIOR AND SCIENCE EDUCATION
For many students, especially females, these courses are their first introduction to behavioral biology. Many female undergraduates approach us to discuss graduate school and research careers after taking these courses. 75% or more of our graduate applicants are female. A good proportion of students enrolled in animal behavior courses become motivated for research careers, but there is little hope to offer them that they will actually be able to become practicing scientists when they finish due to severe limitations on research funding.
Horse Breeding Behavior
Puberty is the attainment of sexual maturity. In fillies, this is usually at 12 to 15 months of age, but it can be as early as 9 to 10 months. Stallions are 15 months or older before they can successfully breed. Research has noted that both stallions and, to a lesser degree, fillies may exhibit sexual display before their reproductive tracts are physiologically mature. Pregnancy cannot occur until the respective reproductive tract matures at the time of puberty. Conversely, some fillies may cycle but not exhibit signs of estrus.
Estrus, or heat, is the period of the reproductive cycle when the mare ovulates and, if bred, is likely to conceive. Estrus is also the time when the mare is receptive and will accept the stallion. The average length of the estrous cycle, or the period from heat period to the next heat period, is 21 days, but the estrous cycle can vary from 19 to 26 days. The duration of estrus is five to seven days (actually about six days), but it can vary from two to 10 days. The first heat following foaling is referred to as foal heat. Foal heat typically occurs six to nine days after foaling, but it may be as early as five days or as late as 15 days.
It is important to recognize the behavioral signs of estrus. Some signs are general, including restlessness, hyperactivity, less time devoted to eating and resting, and more time “running the fences.” Other signs more descriptive of estrus are frequent urination, straddling (squatting) posture, and clitoral “winking.” Mares exhibiting strong heat will actually lay against a fence or teasing partition when exposed to the teaser, a stallion used to make mares exhibit estrus. Most mares will not exhibit overt signs of estrus without the presence of a stallion.
Courtship and Mating
Horses are referred to as “long-day breeders” because they come into heat as the days increase in length in the spring. Mares are also “seasonally polyestrous,” meaning they have multiple estrous cycling throughout the spring and summer. The natural breeding season for horses in the Northern Hemisphere is the spring or summer. Light is the controlling factor in causing mares to come into heat in early spring. Most studies have indicated a tendency toward anestrus (not cycling) in the winter months however, some mares may cycle during this time as well.
Mares will cycle several times during the breeding season if they do not conceive and become pregnant. The most intense estrus behavior occurs when the mare is most sexually receptive to the stallion. Intense estrus behavior lasts about three days.
A mare in heat may actively seek out and attempt to stay in the vicinity of a stallion. During the peak of estrus, the mare may sniff, lick, or nuzzle the stallion. A mare in heat will also urinate frequently, particularly if a stallion is teasing her to test her receptiveness. She is also likely to raise her tail and assume a breeding stance. The classic behavioral display of the stallion when it “checks” a mare is to lift its nose into the air and curl his upper lip. This is called the Flehmen response. The stallion will often be impatient, alert, hyperactive, and restless. Vocalization is common. The stallion will frequently nudge the mare, apparently to signal readiness and to assess her “firm stance” response. In addition to nudges, some stallions may smell and bite over the mare’s body. Most behavioralists consider this display to be more important in the courtship process than odor recognition.
Dominance patterns are very much a part of breeding behavior, particularly in wild horses. Dominance patterns are not as easily seen on most modern stud farms, where stallions are not allowed to run in groups with bands of mares. In a natural environment, one stallion will typically dominate the breeding of a band of mares, and competing stallions will be banished to form their own separate band. At some point, one of the banished stallions will become old enough, brave enough, or tough enough to defeat the dominant stallion. In modern breeding establishments with numerous, separately stalled breeding stallions, all the stallions are used for breeding. Dominance, nevertheless, is in evidence. Most breeding barn managers can tell you which stallion is dominant, or “the boss.”
Libido is the term used to denote sexual drive or the degree of sexual urge in animals. A stallion with a high libido will exhibit an eagerness to mount and attempt to breed a mare. In natural situations, stallions exhibit a wide range of libido levels, from zero activity to extreme aggressiveness. Some stallions will have such a strong libido that they will sacrifice all other pursuits in favor of searching for and breeding mares in heat. An extremely high or low libido may cause problems. Young stallions are more likely to exhibit a wide range of libido. Young stallions with extremely low libido are hard to breed and require patience from those handling them. Young horses with very high libido require extreme caution by the handler and those working the breeding shed.
Pattern in parental care behaviour from lower to higher animals? - Biology
Many different standardized behavior tests exist in rodent research. For best results, investigators should familiarize themselves with the intent and methodology of a test before committing to using it in their reseach protocols. Behavioral tests must be adequately described and justified in your IACUC protocol prior to approval for use.
A short description and basic guidelines for some commonly used behavioral tests are included on this page. PI's may use this information to assist them in completing their IACUC protocol and for guidance in planning their experimental procedures.
Paddling Pool Task
Synonyms: Oxford Paddling Pool test
The paddling pool task (PPT) has been shown to be a less averse, mouse specific spatial cognition test that combines aspects of the Morris water and Barnes mazes. This test is used to assess hippocampus-based learning in mice. The PPT, compared to the Morris water maze, minimizes anxiety, exhaustion and hypothermia which are known to be significant interfering factors in mouse performance in the Morris water maze.
In the PPT the test mouse is placed in a circular tank filled with cold water (i.e., 18° +/- 1°C) to a depth of 2 cm. The tank has 12 escape holes located around the periphery (‘clockmaze’). One hole is open (true exit) to a dry escape corridor and the other 11 holes are blocked. Specific objects (visual cues) are placed around the outside of the tank. The mouse can use the visual cues to find the true exit more quickly each time it completes a trial. Mice undergo a period of pre-training to gain familiarity with the apparatus. For the test itself, the mouse is given a series of learning trials in the tank in which they can paddle (walking in the water) until they find the true exit. Each learning trial lasts a specific amount of time and the time between trials must also be specified. Parameters measured during the learning trials include escape latency and number of errors (blocked exits visited). Following this, a “probe trial” may be run in which all escape holes are blocked and the time the animal spends near the previously open exit is measured. Animals that have learned the position of the true exit will spend most of their time in the area where it was located. Animals that are poor learners will search other areas of the tank.
See this link for photos of the PPT.
Species used: This test was developed for mice. Special consideration must be given to the use of this test in mouse strains or genotypes with reduced ability to navigate using spatial cues, e.g., visual impairments.
As with all behavioral tests, transportation of animals and set up of the experimental area must be carefully planned to limit exposure of test mice to unnecessary light, vibrations, noise, or other stressful events that can influence behavior. Behavioral tests are frequently done during the dark phase of the light cycle and mice should not be exposed to bright light prior to the testing period (e.g., during transport to the testing room). Animals benefit from prior acclimatization to handling and pre-test training to familiarize the mice to the apparatus is important.
- The tank water for the PPT must be cold enough to stimulate the mice to actively explore the tank. Published temperatures range from 18-21°C. Water temperature must be monitored continuously ice cubes may be added to keep it cold. If water temperatures are too high, mice may remain immobile in the center of the pool.
- The water depth is usually 2 cm. Mice must be able to constantly touch the floor of the pool.
- Twelve escape holes are arranged equidistantly around the tank perimeter. The lower edge of each hole must be at mouse head level. Escape hole diameter is usually 40-50 mm. Mice may be reluctant to enter holes that are too large or small. During the test, eleven of the escape holes are sealed to prevent mouse entry. Hole plugs should be flush with the internal pool surface and look like the open escape hole. Plugs should be the same color (e.g., black) as the open escape hole which is attached to a black plastic pipe.
- Tap water is used to fill the PPT tank. The floor of the tank may be colored white to increase aversiveness and encourage escape.
- Urine and fecal material will accumulate in the water and contribute to bacterial contamination and growth. The tank should be drained and disinfected after each day's trials. Partial water changes between mice may reduce the accumulation of urine/fecal material. Fecal material may be removed after each animal with a small mesh net.
- After completing a trial, the mouse may be placed in a clean plastic cage under a heat lamp for a few minutes to dry. Towel or blow drying is not recommended.
- Quickly release the mouse just above water level in the center of the pool. Slowly releasing the mouse may lead to struggling and can impair initial orientation.
- Maximum trial length is 60 seconds. The mouse is gently guided toward the exit if the trial time is exceeded.
- Inter-trial intervals are 15-20 minutes with up to 4 trials per day for 3-4 days.
Deacon, R. M. J. Shallow Water (Paddling) Variants of Water Maze Tests in Mice. J. Vis. Exp. (76), e2608, doi:10.3791/2608 (2013).
Morris Water Maze
Synonyms: (submerged platform) water escape task, Morris water escape task, Morris water navigation task.
The purpose of this test is to evaluate spatial memory. In this test the animal is required to swim in a tank of opaque water until it finds a submerged platform that it can mount to escape the water. Presumably, the animal uses specific visual cues placed around the outside of the tank to learn where the platform is located. An animal that is able to remember the cues will find the platform more quickly each time it completes a trial swim. Animals are initially given a series of “learning trials” in which they are allowed to swim in the tank until they find the platform. Each learning trial lasts a specific amount of time and the time between trials must also be specified. Following this, a “probe trial” is run in which the submerged platform is removed and the time the animal spends swimming in the quadrant of the tank where the platform was previously located is measured. Animals that have learned the position of the platform will spend most of their time in the quadrant where the platform was previously located. Animals that are poor learners will spend time searching other areas of the tank.
See this link for an illustration 1 of the Morris water maze.
Species used: Rats and mice. This task was developed for use in rats (generally good swimmers). In mice, performance in this test is highly dependent on genetic background. Special consideration must be given to the use of this test in mouse strains or genotypes with reduced ability to navigate using spatial cues or to swim, e.g., visual or musculoskeletal impairments. In addition, mice with other physiological or behavioral traits such as impaired thermogenesis or high anxiety levels may also perform poorly in this test 1 .
- Size (diameter) and depth of the tank (varies with species). Water depth of 15-20 cm is adequate for mice. Rats are larger and may dive to the bottom so require deeper water.
- Size of platform in relation to the diameter of the tank (task difficulty increases with decreasing size of the platform).
- A round shape is recommended for the escape platform (provides the same tactile cues on all sides) 3 . The platform surface should be textured so the animal can maintain a secure grip and close enough to the water surface so the majority of the animal’s body is out of the water when on top of the platform (e.g., mice ≤0.5 cm below water surface).
- Mice are more susceptible to hypothermia than rats. Hypothermia risk can be lessened by increasing the water temperature and/or increasing the inter-trial interval. Water temperatures < 20⁰C can lead to hypothermia. Temperatures that are too warm may discourage active swimming/searching. Animals should be allowed to dry in a warm environment after removal from the tank. Absorbent towel(s) may be placed in the holding cage to collect water dripping off the animal and a heating source directed over or underneath the cage may provide warmth. Do not attempt to towel- or blow -dry animals as this is stressful and rough handling can cause injury.
- Substances used to make the water opaque must be edible and nontoxic because animals will consume the substance when grooming after each trial. Tempera paint is recommended 3 . Milk supports bacterial growth, especially in warm water and lime or chalk may be toxic. Alternatives that may allow the use of clear water include using a clear Plexiglas platform or using a platform the same color as the tank surface.
- Cleaning schedule for the tank (water changes). Urine and fecal material will accumulate in the water and contribute to bacterial contamination and growth. The tank should be drained and disinfected after each day’s trials. Partial water changes between mice can reduce the accumulation of urine/fecal material. Fecal material may be removed after each animal with a small mesh net 3 .
- Trials should not exceed 2 minutes.
- Inter-trial intervals should be long enough to prevent the development of hypothermia and fatigue over repeated trials. It is recommended that intervals be at least 10-15 minutes, especially in mice 5 .
- Animals must be observed continuously while in the tank and removed from the water if their head sinks below the surface 4 .
- Two to four trials per day are generally adequate for training.
Alternative tests for spatial learning and memory: Paddling Pool Task, Radial arm maze, Barnes circular platform maze
- Terry AV Jr. Spatial Navigation (Water Maze) Tasks. In: Buccafusco JJ, editor. Methods of Behavior Analysis in Neuroscience. 2nd edition. Boca Raton (FL): CRC Press 2009. Chapter 13. Available from: http://www.ncbi.nlm.nih.gov/books/NBK5217/
- Crawley JN. What’s Wrong With My Mouse? Behavioral Phenotyping of Transgenic and Knockout Mice, 2 nd ed. Hoboken (NJ): Wiley 2007.
- Wahlsten D. Mouse Behavioral Testing: How to use Mice in Behavioral Neuroscience. Amsterdam: Elsevier 2011.
- Guidelines for the Care and Use of Mammals in Neuroscience and Behavioral Research. Washington, DC: The National Academies Press, 2003.
- Iivonen H, Nurminen L, Harri M, Tanila H, Puolivali J (2003). Hypothermia in mice tested in Morris Water Maze. Behav Brain Res 141: 207-213.
Porsolt Forced Swim Test
Purpose: The Porsolt swim test (PST) was developed as a rodent screening test for potential (human) antidepressant drugs. It is based on the assumption that an animal will try to escape an aversive (stressful) stimulus. If escape is impossible, the animal eventually stops trying and gives up. In the PST, the animal is placed in a cylindrical container of water from which it cannot escape. Most animals will attempt to escape by actively swimming. When the animal stops swimming and floats on the surface of the water it is considered to have “given up”. An animal that gives up relatively quickly is thought to be displaying characteristics similar to human depression. The validity of this test stems from the finding that physical or psychological stress (which can induce depression in humans) administered prior to the test causes animals to give up sooner and treatment with an antidepressant drug will increase the time an animal spends in escape attempts.
Species used: Rats and mice. Impaired swimming ability due to musculoskeletal or other abnormalities will affect performance in this test.
- The water must be deep enough so the animal cannot touch the bottom with its tail or feet. A depth of 30 cm is commonly recommended, although less depth may be adequate for mice. Water temperature should be 24-30⁰C 2 .
- Animals should be allowed to dry in a warm environment after removal from the water. Absorbent towel(s) may be placed in the holding cage to collect water dripping off the animal and a heating source directed over or underneath the cage may provide warmth. Do not attempt to towel- or blow-dry animals as this is stressful and rough handling can cause injury.
- Water changes: Urine and fecal material will accumulate in the water and contribute to bacterial contamination and growth. The container should be emptied and disinfected after each day’s tests. Fecal material may be removed after each animal with a small mesh net.
- Test procedures: A wide range of test session durations have been reported (4-20 minutes) 1 . Animals must be observed continuously during the swim test. Any animal that sinks below the surface should be removed from the water immediately 2 .
Alternative tests: Tail-suspension test and others 1,2,3 .
- Crawley JN. What’s Wrong With My Mouse? Behavioral Phenotyping of Transgenic and Knockout Mice, 2 nd ed. Hoboken (NJ): Wiley 2007.
- Guidelines for the Care and Use of Mammals in Neuroscience and Behavioral Research. Washington, DC: The National Academies Press 2003. Available from: http://www.ncbi.nlm.nih.gov/books/NBK43327/
- Castagne V, Moser P, Porsolt RD. Behavioral Assessment of Antidepressant Activity in Rodents. In: Buccafusco JJ, editor. Methods of Behavior Analysis in Neuroscience. 2nd edition. Boca Raton (FL): CRC Press, 2009. Chapter 6. Available from: http://www.ncbi.nlm.nih.gov/books/NBK5222/
Tail Suspension Test
Purpose: The tail suspension test (TST) was developed as a rodent screening test for potential (human) antidepressant drugs. It is based on the assumption that an animal will actively try to escape an aversive (stressful) stimulus. If escape is impossible, the animal will eventually stop trying ("give up"). In the TST a mouse is suspended by the tail so that its body dangles in the air, facing downward. The test lasts for six or more minutes and may be repeated multiple times. Mice initially struggle to face upward and climb to a solid surface. When the animal stops struggling and hangs immobile it is considered to have “given up”. Longer periods of immobility are characteristic of a depressive-like state. The validity of this test stems from the finding that treatment with an antidepressant drug will decrease the time the animal spends immobile.
Species used: mice
- Mice are suspended (a variable distance) above a solid surface by the use of adhesive tape applied to the tail. If the tape is incorrectly applied or fails, the mouse will fall. The use of a “cushioned” surface below the TST may be needed to help prevent injury to the animal. Mice that experience a fall should be removed from the experiment 1 .
- Vinyl or medical adhesive tape is recommended. Duct tape is too adhesive and will tear hair and skin when removed 1 . The tape should be applied in a consistent position ¾ of the distance from the base of the mouse’s tail 2 . If the tape is applied too near the tip of the tail it may pull off the skin of the tail tip and the mouse will fall.
- Some strains (e.g., C57BL/6J) may not perform well in the TST due to tail climbing behavior. Strains with vestibular deficits may show an abnormal spinning phenotype and should not be used in the TST. Other mouse phenotypes that display neurological abnormalities that lead to unusual leg clasping behavior or that influence immobility times may also not be appropriate models for this test 1 .
Alternative tests: Porsolt swim test and others 2 .
- CL Bergner, AN Smolinsky, PC Hart, BD Dufour, RJ Egan, JL LaPorte, AV Kalueff. 2010. Mouse Models for Studying Depression-Like States and Antidepressant Drugs. In: Mouse Models for Drug Discovery, Methods in Molecular Biology 602: 267-282.
- Castagné V, Moser P, Porsolt RD. Behavioral Assessment of Antidepressant Activity in Rodents. In: Buccafusco JJ, editor. Methods of Behavior Analysis in Neuroscience. 2nd edition. Boca Raton (FL): CRC Press 2009. Chapter 6. Available from: http://www.ncbi.nlm.nih.gov/books/NBK5222/
- B Thierry, L Steru, P Simon, RD Porsolt. 1986. The tail suspension test: Ethical considerations. Psychopharmacology 90: 284-285.
Use of Electric Shock in Research Animals
Purpose: Electric shock is used as an aversive stimulus in behavioral testing with humans and other animals, including invertebrates. Aversive stimuli function as a type of negative reinforcement: The frequency of a measured behavior increases in order to end or avoid the aversive stimulus. Electric shock is favored as an aversive stimulus because it is easily quantifiable can be manipulated to have discrete or gradual onset and offset and (at levels typically used in research) does not cause physical damage to the subject. The disadvantage of electric shock includes the fact that it can be painful and is an “unnatural” stimulus (i.e., not normally experienced outside the laboratory). Electric shock stimulates uncontrolled muscle contractions and will result in (increasing) pain as intensity increases.
Species used: Many species although rodents are most commonly used. Impaired motor coordination due to musculoskeletal or other abnormalities will affect performance if animals are expected to coordinate movements to escape the electric shock.
- The level of shock intensity used must be sufficient to elicit a reaction in the animal but not enough to injure or create unnecessary pain or distress.
- The investigator must be familiar with the capacity of their equipment and the shock levels typically applied in the species under study. Devices designed for larger animals (e.g., rats) may not be suitable for mice.
- Some authors recommend that the shock intensity being used be evaluated daily by placing a hand onto the electric grid while the shock is being delivered. No more than a “mild tingling” should be felt 1 .
- Shock delivered in pulses provides for “shock-free intervals” that allow more effective escape attempts by the animal 2 .
- Water decreases the electrical resistance of skin and other tissues. The presence of urine or other sources of moisture will increase the shock intensity experienced by the animal.
- Electric current delivered to a small area of skin is perceived as more aversive than the same current applied to a larger area 2 . An animal standing on a rough surface may perceive greater shock intensity than one standing on a smooth surface.
- Species, genetic background and other intrinsic variables may influence an animal’s degree of sensitivity and type of response to shock and must be considered 2 . Please consult the references listed at the end of this section for additional information on how to design and set up experiments using electric shock (in rodents).
- Do not require animals to perform complex or skilled maneuvers to escape shock 2 .
- Mice show two primary reactions to electric shock: Jumping and running. Genotype will influence which reaction predominates in a strain. Investigators may want to consider the typical reaction pattern of the strain(s) they are using when planning what type of escape response will be required by the animal (e.g., a strain that responds to shock by running may have difficulty learning to escape if jumping is required to leave the shock chamber) 2 .
- If animals can retreat to non-electrified areas within the apparatus (e.g., chamber edges) they may be able to avoid the shock. This is more likely to occur when tasks are too difficult and cannot be learned quickly 2 .
Alternative types of aversive stimuli or methodology: Air puffs, loud noises, bright lights or ultrasonic tones. Alternative training methods include the use of a reward (e.g., preferred food) for correct responses instead of punishment (electric shock) for incorrect responses.
For more information on test procedures and experimental design please consult the following references:
- Graham JH and Buccafusco JJ (2001). Inhibitory Avoidance Behavior and Memory Assessment. In Buccafusco JJ (ed.), Methods of Behavior Analysis in Neuroscience, p.141-151. Boca Raton: CRC Press.
- Wahlsten D (2011). Mouse Behavioral Testing: How to Use Mice in Behavioral Neuroscience. London: Academic Press.
Social, Maternal and Aggressive Behaviors in Rodents
Many standard behavioral tests exist for the study of interactive behavior in mice and rats. In order to choose the most appropriate test for a research study it is important to understand something about the range of rodent social behaviors and what, specifically, behavioral tests are attempting to measure. Rodent social behavior may be classified into general categories such as aggression and social dominance behavior parental and maternal behavior and social recognition and approach behavior. Specific tests are designed to investigate behavioral differences in each of these categories.
Rats and mice used in research are considered social species, meaning, in general, they prefer some form of group living. Species that live together must interact and so have evolved various behaviors that allow and facilitate group living. Environmental conditions and individual characteristics (e.g., sex, age, reproductive status, genetic background, etc…) are important in determining the form and amount of social interaction that occur within a group. In addition, sensory and motor abilities and health status can influence the expression of social behavior in individual animals. For example, an animal may be less willing to interact with others if it is ill or in pain. In another example, the sense of smell (olfaction) is extremely important in mouse communication and mice with olfactory deficiencies may behave quite differently than normal mice.
Before performing behavioral tests on rodents, especially when using unfamiliar strains or mutants, investigators must evaluate overall health and specific sensory and motor capabilities of the animals to avoid biased and inaccurate interpretations of the role of genetics in behavior.
Aggression and Social Dominance Behavior
Specific tests include the standard opponent test, isolation-induced fighting, resident-intruder test, and tube-test for social dominance. These tests are described below.
Aggressive behaviors are usually related to either territorial or maternal defensive actions or the establishment and maintenance of social status within a group. Males tend to show more territorial and social dominance behaviors than females but there are exceptions. Predatory behaviors (behavior oriented toward catching and killing of prey) are not included in this category. Rodents who bite humans are also not displaying true aggressive behavior but rather, fear induced defensive behavior.
Rats and mice differ in their social organization and use of aggressive behaviors. Male mice are territorial and do not tolerate unfamiliar males within their home range (or cage). Females may establish territories but tend not to defend them with aggressive behavior. Male (and female) mice mark territorial boundaries with urine this is an important method of avoiding unnecessary aggression and its consequences in this species. In contrast, rats have evolved to live in multi-male/multi-female groups and tend to coexist peacefully if group composition is stable.
Although both mice and rats establish social dominance hierarchies within groups, they differ in important characteristics. Male social hierarchies in stable rat groups tend to stay the same despite changes in weight and/or size of individuals. In these types of groups, age may be the best predictor of social status. Male mice also establish social dominance hierarchies in a group but they will continuously compete for dominance. This often results in fighting and subsequent injuries. Changes in group composition, the presence of female mice in the room (olfactory stimulation) or manipulation of the mice (e.g., cage changing, temporary removal for experimental procedures) may increase fighting. If multiple mice are in the cage, removal of the dominant mouse will not necessarily stop the injuries, as the remaining mice will fight to reestablish a social order. Female mice and rats also establish social dominance hierarchies but tend not to fight. This makes it easier to group house them but harder to study social organization.
Standard Opponent Test
This test evaluates male aggression and social dominance in a test animal placed with an unfamiliar conspecific in a neutral area. The test subject is confined with a ‘standard opponent’ partner for a specific time in an unfamiliar cage or other defined space.
Important considerations for this test:
- The standard opponent(s) males are selected for highly replicable behavior as either submissive or dominant males in repeated tests with other males. Standard opponent partners are usually chosen from mouse strains known for either high or low levels of aggression. The selected mice are then used as standard opponent test partners in pairings with experimental mice.
- Differences in weight, age and size between the test mouse and the standard opponent may also influence test results.
- Keep in mind that it will be necessary to keep track of which mouse is the test subject and which is the ‘standard opponent’ during the test session. Mice with different coat colors will make this easier to do.
- Test sessions are often 5 minutes in length but are terminated early if attacks and biting are severe.
- The presence of humans can influence animal behavior during the test. The observer should be screened from the animals and/or the mice may be videotaped for scoring later.
- The frequencies of specific (predetermined) behaviors are scored. Examples of behaviors include body and anogenital sniffing sniffing, following and chasing, number and location of bites and tail rattling.
More information on standard opponent testing may be found in this and other references:
Crawley, JN. What’s Wrong With My Mouse? Behavioral Phenotyping of Transgenic and Knockout Mice, 2 nd ed. Wiley-Interscience, 2007.
This is a modification of the standard opponent test in which male mice are singly housed for a specific time period (e.g., four weeks) prior to placement with an unfamiliar male mouse into a test arena or cage. Isolation of male mice tends to increase the frequency of fighting and attack behaviors.
Another modification of the standard opponent test, the resident-intruder test is conducted in the home cage of the test mouse. The unfamiliar male mouse is the ‘intruder’. The test mouse (‘resident’) will attempt to defend its home cage from the intruder. Isolation is not needed prior to this test. Aggression in the resident mouse will be higher if he is living with a female and her litter (sired by him). However, the female and her pups must be separated from the fighting area, as the female will also display aggression toward the intruder (maternal defense).
Tube-Test for Social Dominance
This test measures dominant/submissive behavior in mice without allowing them to fight and injure each other. Both male and female mice may be tested with the Tube-Test. In the test, two mice of the same gender are placed at opposite ends of a clear, cylindrical tube and allowed to explore toward the tube center. At the point where the mice meet, the submissive mouse will tend to back up as the dominant mouse continues moving forward. The mouse that leaves the tube first (‘pushed out’) is the loser and the other mouse (dominant) is the winner. Automated equipment for this test exists that can measure additional parameters such as duration of match, latency to enter the tube, etc… This test can be used for determining social dominance relationships within a group of mice.
Rat and Mouse Parental and Maternal Behavior
Parental behaviors can be classified as direct (having an immediate physical impact on offspring and their survival) or indirect ((behaviors that do not involve physical contact but still affect offspring survival). Examples of direct behaviors include nursing, grooming or licking, retrieving and huddling. Some direct behaviors may be performed by males (i.e., the sire). Examples of indirect behaviors include nest building, defense against conspecifics or predators, acquiring and defending critical resources and care for pregnant or lactating females. Indirect behaviors may be performed by either parent and by other (non-parent) adults, which is referred to as alloparental care.
Although some laboratory studies indicate that adult male mice and rats are capable of parental behaviors, these occur at a low level and care of the young is primarily left to the female. Studies of wild mice and rats have shown that males are not involved in care of the young and will kill young that are not their own. Males will also kill unrelated or unfamiliar young under laboratory conditions. While the presence of the male sire in the breeding cage is generally not harmful to pups, there is no evidence that the male benefits pup growth and development. Adult males other than the sire, however, should not have access to young other than their own. See references 1 and 2 below for more information.
Maternal behavior typically refers to all aspects of behavior of the dam between parturition and weaning of the offspring and includes both direct and indirect behaviors. Some aspects of maternal behavior (e.g., nestbuilding) may begin prior to birth of the young. Laboratory studies with rodents have shown that hormonal changes (e.g., oxytocin) are important triggers for onset of maternal behavior. As hormonal influence decreases after parturition, infant stimulation increases in importance in this regard. Stimuli from pups, including ultrasonic vocalizations (USV), are needed to maintain maternal care after about 5 days postpartum (2, 3, 4). Infant rats and mice emit a variety of sonic and ultrasonic vocalizations that attract the dam’s attention. In mice, inbred strain differences in hearing ability and the number of USV emitted by pups have been found. USV have been extensively studied in rodents and various protocols for are available for experimental research (2,4).
In rats and mice, a postpartum estrus occurs within 24 hours after parturition. Laboratory studies have suggested that postpartum mating activities are shorter in duration than during normal estrus periods and do not significantly reduce maternal time spent with the litter (2). After the postpartum estrus period the female will not come into estrus again until after the pups are weaned. If she mated and conceived during the postpartum estrus, the second gestation may be prolonged by a week or more.
Young rats and mice are altricial, which means they are born in a relatively undeveloped state and cannot move, maintain body heat, see or hear on their own. Extensive maternal care is required for the young to survive. Rats and mice have evolved specific behaviors that contribute to the survival of altricial offspring. Both rats and mice will actively build nests in which to rear their young. These nests are built by the female and may be complex, multi-entrance enclosures if the dams are provided with appropriate building material. Significant strain differences in nest building skills have been shown in mice.
Both rats and mice will nest communally (multiple females rear their young in the same nest) and nurse offspring that are not their own. Laboratory studies have indicated that pup survival to weaning is higher for rats who rear their litters alone rather than in a communal nest. The opposite may be true in mice. Multiple studies have shown that mouse pups reared in communal nests had higher growth rates and better survival than pups reared alone with their dam (4). However, communal nesting/nursing may not be successful if the age difference between litters is greater than 5-7 days. In this situation, dams may be aggressive toward pups that are not their own.
Lactating females will display aggressive behavior to defend their offspring from others of their own species. The presence of pups appears to be the primary trigger for female postpartum aggression. The presence of unfamiliar male or female conspecifics will provoke maternal aggression although the likelihood and expression of maternal aggression varies with strain, individual and location (e.g., home cage versus test arena) (2,4).
There are a number of events and experiences that will influence the behavior of both the mother and the pups. These include the effects of handling of the dam and/or pups and disturbance of the cage environment by the researcher. Depending on the experimental objective these could be confounding factors and must be considered. Maternal behavior during lactation will also be affected by changes in the pups as they grow and mature and by the evolving physiological state of the dam.
Laboratory studies have shown that the main components of rodent maternal behavior (nursing, licking and grooming, pup retrieval and nest building) are present at high levels in almost all rats and mice after giving birth (2,4). Time spent in these behaviors typically declines gradually during the first two weeks of lactation and then decreases further or disappears during the third or fourth week after parturition. Consumption of food and water by the dam increases dramatically over the first two weeks of lactation and may influence the amount of time spent on maternal behaviors. Although commonly used as experimental measures of maternal behavior, nest building and pup retrieval do not normally occur at high frequencies in undisturbed conditions. Mice and rats build nests if material is available but once made, the nest is not rebuilt from scratch unless disturbed. Pup retrieval is also infrequently necessary under normal conditions.
Rat and mouse pups start eating solid food around 15-17 days of age and nursing by the dam ends by four weeks after gestation. Weaning of a litter is normally a gradual process that can stretch well beyond the third week. The typical abrupt weaning that takes place in the laboratory when the pups are 3-4 weeks of age provides another example of experimental manipulation influencing normal behavior.
Why is consumer behavior important?
Studying consumer behavior is important because it helps marketers understand what influences consumers’ buying decisions.
By understanding how consumers decide on a product, they can fill in the gap in the market and identify the products that are needed and the products that are obsolete.
Studying consumer behavior also helps marketers decide how to present their products in a way that generates a maximum impact on consumers. Understanding consumer buying behavior is the key secret to reaching and engaging your clients, and converting them to purchase from you.
A consumer behavior analysis should reveal:
- What consumers think and how they feel about various alternatives (brands, products, etc.)
- What influences consumers to choose between various options
- Consumers’ behavior while researching and shopping
- How consumers’ environment (friends, family, media, etc.) influences their behavior.
Consumer behavior is often influenced by different factors. Marketers should study consumer purchase patterns and figure out buyer trends.
In most cases, brands influence consumer behavior only with the things they can control think about how IKEA seems to compel you to spend more than what you intended to every time you walk into the store.
So what are the factors that influence consumers to say yes? There are three categories of factors that influence consumer behavior:
- Personal factors: an individual’s interests and opinions can be influenced by demographics (age, gender, culture, etc.).
- Psychological factors: an individual’s response to a marketing message will depend on their perceptions and attitudes.
- Social factors: family, friends, education level, social media, income, all influence consumers’ behavior.
Evaluating Water Quality to Prevent Future Disasters
B. DeCourten , . S. Brander , in Separation Science and Technology , 2019
7 Transgenerational and Epigenetic Effects
It is now established that nongenetic inheritance, sometimes induced by rapid environmental changes such as those associated with GCC or anthropogenic pollution, can facilitate relatively rapid phenotypic change ( Bonduriansky et al., 2012 Shama and Wegner, 2014 Thor and Dupont, 2015 ). This rapid change may allow organisms to adapt to longer-term changes in abiotic conditions, such as increasing temperature or acidification ( Munday, 2014 ), or to evolve tolerance to other related stressors ( De Schamphelaere et al., 2010 ). However, shorter term or stochastic changes may result in having offspring with maladaptive phenotypes or reduced genetic diversity ( Day and Bonduriansky, 2011 Ward and Robinson, 2009 ), and to date there is limited evidence of anticipatory parental effects that increase the survival of offspring ( Uller et al., 2013 ). Although studies on the transgenerational effects of co-exposure to GCC-related stressors and EDCs are limited, several investigations have been completed. Recent studies indicate that parental exposure to environmentally detected levels (low ng/L) of EDCs such as bifenthrin and ethinylestradiol at higher temperatures, results in organism-level impacts on embryonic development and skewed sex ratio in indirectly exposed offspring in vertebrates with TSD. Furthermore, in the same study, co-exposure to increased temperature and EDCs caused a reduction in fecundity (fewer viable offspring), as well as increased developmental deformities in the indirectly exposed generation and alterations in gene expression ( DeCourten and Brander, 2017 DeCourten et al., 2019 ).
Notably, organisms with environmentally mediated sex determination (TSD, such as certain reptile and fish species, appear to be markedly sensitive to altered temperatures associated with GCC ( Consuegra and Rodríguez López, 2016 ), as well as co-exposure to EDCs and climate change-related factors ( Brown et al., 2015 ). In invertebrates such as Siphonaria autralis, co-exposure to increased temperature, UVB light coupled, and aqueous copper resulted in reduced embryonic viability ( Kessel and Phillips, 2018 ). Alternatively, parental conditioning, defined as exposure during gametogenesis in invertebrates and most fish species, could enhance transgenerational plasticity and allow for transgenerational acclimation ( Munday, 2014 ), allowing organisms to rapidly adapt to environmental change, as was observed recently with sea urchins in response to upwelling conditions associated with GCC ( Wong et al., 2018 ). However, it remains to be seen how effective this adaptive tendency in organisms exposed to multiple simultaneous stressors.
The transgenerational effects described thus far may be attributable to the direct exposure of the primordial germ cells within parents, which produce the F1 generation, to combined stressors. However, there may also be changes in DNA structure and regulation contributing to observed responses. Epigenetic tags, such as methyl or acetyl groups, modify the structure of DNA. Epigenetic modifications are vital during embryonic development with regards to cellular differentiation, but epigenetic modifiers also respond to environmental stress ( Brander et al., 2017 Head et al., 2012 ). Such tags are now known to play a pivotal role in controlling the expression of genes. A number of recent papers highlight the importance of epigenetics in terms of evaluating responses to aquatic pollutants and demonstrate that epigenetic mechanisms are important both within the lifetime of an organisms as well as in subsequent generations, since epigenetic modifications to gametes can be inherited through multiple generations ( Bhandari, 2016 Corrales et al., 2014 Head, 2014 Voisin et al., 2016 ). Findings from these initial multigenerational studies highlight the importance of evaluating effects within and across generations when it comes to multiple stressors related to GCC, particularly since the effects of low-dose exposures in parents may not be observed until the F1 or F2 generation and may be carried through to subsequent generations. It has become evident that considerations of effects across generations must begin to be incorporated into risk assessment ( Shaw et al., 2017 ).
Moral and Philosophical Criticisms
As mentioned earlier, certain theories that propagated both nature and nurture respectively led to socio-moral problems like racial discrimination, stereotyping, and construction of a reality based on facts that fit our train of beliefs. On the other hand, philosophers questioned the very idea of the existence of ‘traits’ and what it all really stood for. Also, if we are who we are because of something that is predetermined like genetics or an influence of environmental factors, then where is our own free will?
These controversies and debates regarding the influence of heredity and environment on our development started centuries ago, and with every new discovery, will come another challenge based on scientific, moral, socio-political, and philosophical grounds. So for now we will rest our case with the fact that we need both to survive and thrive and can’t ignore the existence of one in favor of the other.