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Hormone is a chemical messenger secreted by a specific endocrinegland of the body, transported by body fluids, producing specificeffect on a target tissue or organ in the body.

Many intricate neuroendocrine feedback systems control theproduction & release of hormone in the organism.A number of hormones like MSH, ACTH, Vasopressin, Oxytocinetc. affect the behaviour of the organism.A new branch called ehavioural Endocrinology orPsychoendocrinologyhas developed, which deals with the hormones

and behaviour in animals.Generally hormones show various effects or behavioural changes inanimals which affects social life of animal and adaptation.Natural selectionis better seen when comes to behaviour as the more

powerful an animal is can survive worthly.

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In order to understand the role of hormones in ourbehaviour scientists have conducted fundamentalresearch using laboratory animals. Frank Beach isgenerally considered to be the founding father ofthe study of the effects of hormones on behaviour- an area of scientific investigation that is knowntoday as behavioural endocrinology orpsychoendocrinology. His first book, Hormonesand Behavior (1948), summarizes all that wasknown at the time and organized the field for allsubsequent investigators. FRANK BEACH

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Adaptive

behaviour

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It has been that in several animals male androgensare responsible for aggressiveness.Sevenster & Wilz (1961) performed an experimenton stickleback fishes. It had been observed malestickleback due to aggressiveness kill other males bybiting when injected high level of testosterone.Wilz (1970) confirmed that even when the deadmales are removed from that particular site aggressivemale starts killing female ones.The main hormone responsible for the aggressivebehaviour of an animal is high level of testosteroneand low level of serotonin.This is the reason males are more aggressive thanfemales.

Stickleback

Eagles fighting with each other

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Dolphins

Koel

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Beach (1971) divided female behaviour (in rats )into thefollowing three phases-Receptivity: the females ability to copulate.Proceptivity:describes the female's eagerness to copulate witha male. This can be assessed by recording the extent to whichfemales approach and spend time with males, and emit femalesexual behaviours.Attractiveness: a measure of how attractive a female is to amale.Sexual behaviour in male rats consists of three behaviours:Mount:the animal assumes the copulatory position on top ofthe female but does not insert his penis into the female's vaginaIntromission: the male mounts the female and briefly (200-300 milliseconds) inserts his penis. Semen is not released duringintromissions or mounts.After 10 to 12 intromissions spaced 20-30 seconds apart, therat ejaculates semen.The main hormone responsible for sexual behaviour in femaleare high level of estrogens and androgens in male.LHRFreleased from the hypothalamus have direct effects oncopulatory behaviour (Moss and McCann, 1973) in vertebrates.

Lordosisin female mouse is a reflexwhich usually occurs when a male

grasps the female's flanks

Female stickleback laying eggs

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Sexual Behaviour In Female AndThe Release Of Hormone During Estrus Cycle-

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Maternal behaviour is elicited in theabsence of certain hormones.Lisk (1971) has observed that estrogenand progesterone work in synergy instimulating maternal nest building.During parturition, oxytocinlevel is highwhich affects the behaviour of mother.Experimentally injections of oxytocininfluence maternal behaviour.Various hormone like progesterone,oxytocin, relaxin, estrogen, prolactin etc.complete maternity of female.

Maternal care in monkey

Spider building web

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In only 6 mammalian species, including humans,the father plays a significant role in caring for hisyoung.An increase in levels ofoxytocin, glucocorticoids, estrogenand prolactin occur in the paternal brain. Thesehormonal changes occur through the father'sinteraction with the mother and his offspring.Oxytocin levels are positively correlated with theamount of affection the father displays towards thechild.Marmoset fathers have enhanced dendritic spinedensity in the prefrontal cortex. This increasecorrelates with increase is vasopressin receptors in thisarea of the paternal brain.

Silvery hair Marmosetwith baby marmoset

Baby penguin under thecare of father

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It is a form of animal social structure in which alinear or nearly linear ranking exists, with each animaldominant over those below it and submissive to thoseabove it in the hierarchy.Dominance hierarchies are best known in socialmammals, such as baboons and wolves, and in birds,notably chickens.A dominant animal is one whose sexual, feeding,aggressive and other behavior patterns subsequentlyoccur with relatively little influence of the othergroup members. Subordinate animals are opposite;their behavior can be relatively easily influenced orinhibited by other group members.It have been observed that male hormones mainlytestosterone and androgen are responsible for thisbehaviour.

Fighting for dominance

Best example can be seen in

Lions for dominance hierarchy

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In ethology, the term territory refers to any sociographical areathat an animal of a particular species consistently defendsagainst conspecifics.The ultimate function of animals inhabiting and defending aterritory is to increase the individual fitness or inclusive fitness ofthe animals expressing the behaviour. Fitness in this biologicalsense relates to the ability of an animal to survive and raise young.Most commonly, this is accomplished by depositing strong-smelling substances contained in the urine, faeces, or, fromspecialized scent glands located on various areas of the body.This type of marking includes pheromones in insects anddischarge of typical scent through urine or sweat glands.Males and female ring-tailed lemurs (Lemur catta) scent-markboth vertical and horizontal surfaces at the overlaps in their homeranges using their anogenital scent glands.

Typical marking like release

of scent or pheromones is

done by animals and insects

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Several long term research projects have captured a gooddeal of attention. These include ape-language experimentssuch as the Washoe project and Project Nim.Several studies have shown that performance is better on,for example, a color discrimination (e.g. blue vs. green)after the animal has learned another color discrimination(e.g. red vs. orange) than it is after training on a differentdimension such as an X shape versus and O shape. Thereverse effect happens after training on forms. Thus, theearlier learning appears to affect which dimension, color orform, the animal will attend to.Memory has been widely investigated in foraginghoneybees, pis mellifera, which use both transient short-term working memory that is non-feeder specific and afeeder specific long-term reference memory.ACTH and MSH are responsible for learning capabilityof an animal.

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Neoteny also called juvenilization, is one of thethree ways by which paedomorphism can arise.Paedomorphism or paedomorphosis is the retentionby adults of traits previously seen only in juveniles,and is a subject studied in the field of developmentalbiology.In Neoteny, the physiological(or somatic)development of an organism (typically an animal) isslowed or delayed.In contrast, in paedogenesis, sexual developmentoccurs faster. Both processes result inpaedomorphism. Ultimately this process results in theretention, in the adults of a species, of juvenilephysical characteristics well into maturity andpaedogenesis, the reproduction in a neotenized state.Growth hormones are responsible for this process.

Ambystoma

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The occurrence of different forms, stages, ortypes in individual organisms or in organisms ofthe same species, independent of sexual variationsis called polymorphism.In bees, the presence of queen, worker, anddrone is an example of polymorphism. Differencesbetween the sexes and between breeds ofdomesticated animals are not considered examplesof polymorphism.The occurrence of several forms or colors in onespecies of insect is also an example ofpolymorphism.The hormones responsible for polymorphism aremainly Juvenile hormone and MSH

Polymorphism in bugs

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Molting or ecdysis, is the manner inwhich an animal routinely casts off a partof its body (often, but not always, anouter layer or covering), either at specifictimes of the year, or at specific points inits life cycle.Brain releases ecdysiotropinwhichstimulates release of molting hormone(MH) from Prothoracic Gland inarthropodsGrowth hormones are responsible formolting in vertebrates.

Molting in pupa

Molting can be seen in snakes

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When male frog croaks, it has beenseen the female starts attracting towardsthem. This is due inducing ofgonadotropin releasing hormone(GnRH)and there aftergonadotropinsin female are released.Also in other animals like parrot,whenever male starts singing the femaleswings with the tune and is attracted tomale due to induced action in it for therelease of gonadotropin.

Parrot singing and

frog croaking

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Adaptive behavior is a typeof behavior that is used to adjust toanother type of behavior or situation.This is often characterized by a kind ofbehavior that allows an individual tochange an unconstructive or disruptivebehavior to something more constructive.These behaviors are most often socialor personal behaviors.Vasopressin and ACTH areresponsible for adaptive behaviour.

All animals adjust according toenvironment for survival

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ggressive behaviour High level of testosterone and low level ofserotoninSexual behaviour Estrogens and androgensMaternal behaviour Estrogen, progesterone & oxytocinPaternal behaviour Glucocorticoids increase in paternal brain

Dominance hierarchy Testosterone and androgenTerritorial marking PheromonesFood gathering Low level of testosterone and estrogenLearning capability ACTH and MSHNeoteny & paedogenesis Growth hormonesPolymorphism Juvenile hormone and MSHMolting Growth hormonesInducing hormone of other Inducing of gonadotropins in femaleAdaptive behaviour Vasopressin and ACTH

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