PARENTAL CARE By Dr Rashmi Kohli DEFINATION n

PARENTAL CARE By: Dr. Rashmi Kohli

DEFINATION n n Looking after the eggs or the young until they are independent to defend themselves from predator is known as parental care Animals exhibit a great diversity in care of their eggs and young during development.

What is included in parental care? n n n n n Construction/maintenance of nest Burying eggs once deposited Chasing away potential predators Fanning or splashing eggs (oxygen/cleaning) Removal of dead/diseased eggs Carrying eggs (mouth, brood pouch, head) Coiling around eggs to prevent desiccation Accompanying fry to forage Providing first food (mucus) Teaching feeding techniques

Distribution of parental care in vertebrates n Teleost fishes = 21% of families show PC n n Amphibians = 71% show PC n n 50: 50 maternal : paternal Birds = 100% show PC n n 61% have male parental care Usually bi parental, sometimes one sex Mammals = 100% show PC n Usually maternal, sometimes biparental

PARENTAL CARE IN FISHES n Fish show all grades of parental care behavior from random spawning and from deposition of large number of uncared eggs to the protection of young.

Two general types of variation in parental care behavior exist among fishes n n First either both parents or one alone cares for the offspring. Thus there are paternal, maternal and biparental species. Second the eggs and newly hatched young are either maintained on the substrate- that is on plant , under stones, in excavated pits and so on. n Substrate brooder n Mouth brooders

Scattering eggs over aquatic plants n In some fishes such as pikes esox lucius, carps, carrassius aurates etc, eggs are scattered usually over aquatic plants to which they are attached.

Laying of eggs at suitable places n They dig excavation in gravel substrate lay their eggs in the pits , cover them with gravel and desert them.

Nest building n n n Only a few fishes construct nest which may be complex like that of birds or simple Male of many species such as darters, sunfishes and cichlids prepare a shallow basin –like nest. The male remains on guard till the young ones are hatched.

Coiling round the eggs n The butter fish rolls all eggs into a ball and curls around it.

Egg brooding in the mouth and intestine. n n n The female tilapia mossambica broods the fertilized eggs in her mouth. She allows the young to take refuge in her buccal cavity at the time of danger. During this period the brooder fish do not take any food thus exhibiting great degree of self sacrifice.

Brood pouches n n The male sea horse and pipe fishes carry eggs in a brood pouch on the abdomen. In sea horse fertilized eggs are transferred by the female into the brood pouch on the belly on the male.

Attachment of eggs to body: n The male nursery fish (kurtus) of new guinea, carries eggs held in a cephalic hook

By putting eggs in integument cups n In siluriods (aspredo and platystacus ) the eggs are pressed into soft and spongy skin of female and carried about.

Feeding the young n n Like birds, some fishes help young in feeding. As the young reach free swimming fry stage of development, they begin to graze on the mucous on their parents’ sides. Mucus producing cells in the adult’s epidermis are most numerous at this stage of the reproductive cycle.

Teaching feeding techniques

Viviparity (true internal incubation) n Viviparity descries the highest degree of parental care and provides maximum protection to the young ones. In viviparous elasmobranches (e. g scolidon , mustelus) eggs develop in the uterus. Each embryo receives nourishment from the uterine tissue through the yolk-sac placenta.

Parental care in Amphibians n n Perhaps no group shows more diversity in parental care than do the amphibian. Anurans show much greater diversity than urodeles and apodans. The method of parental care by amphibians generally fall under two broad categories: n n Protection by nests, nurseries or shelters. Direct caring by parents

n n In apodans and salamanders, parental care consists only of attendance of the eggs, mostly by the female. In anurans the eggs are usually guarded by the male and the parental care involves transportation of eggs and larvae also.

A. Protection by nests, nurseries or shelter: Amphibians have evolved various curios methods of giving protection to their defenseless egg and larvae from the predators: n Selection of site n Defending eggs or territories n Direct development n Defending the larvae n Foam nest n Mud nest

Selection of site n n n Many amphibians lay eggs in protected site most of which are on land. Many tree frog lay their eggs not on land but on leaves and branches overhanging water. Many tropical frogs and toad lay eggs on land near water.

Defending eggs or territories n n In urodela, males of cryptobranchus and hynobius drive away all enemies expect ripe female of own species. Andrias japonius shakes the eggs for proper aeration.

Direct development n In some terrestrial or tree frogs, such as eleutherdactylus, arthroleptis, hylodes and hyla nebulosa , the eggs hatch directly in to little frogs thus avoiding larval motility. In red backed salamander plethodon cinereus, the hatching are miniature of the adults.

Mud nest (nurseries) n In the Brazilian tree frog, hyla fabre, the male digs a little crater like or nursery in mud in shallow water, in which the female lays her eggs. Tadpoles hatch within these mud nest and develop up to a stage when they are large enough to fend themselves.

Foam nest n Many amphibians convert copious mocous secretion in to nests for their young. In Japanese tree frog rhacophorus schlegeli , the mating couple dig a hole or tunel in to which eggs are left in a frothy mass to avoid desiccation.

B. Direct caring by parents Coiling around eggs: The apodans such ichthyophis glutinosa lays eggs in a shallow hole near the water and coils herself around the gelatinous egg mass. The attendent female eats the infected eggs aand thus saves other eggs from infection n

Eggs glued to body n Many amphibians carry the eggs glued to their body. In the dusky salamander, desmognathus fuscus, female carries the string of eggs coiled around her neck until they hatches.

Eggs in back pouches n In one group of tree frogs, called marsupial frogs or toads, the female carries the eggs on her back , either in a open oval depression , a closed pouch or in back.

Organs of brooding pouches n Males of terrestial south american darwins’s frog rhinoderma darwinii, pushes at least two fertilized eggs into his relatively large vocal sacs. Tadpoles complete their development and are metamorphosed in the vocal sacs and come out as a mini frogs.

n The only known cse of gastric incubation/ brooding in vertebrates is found in the australian frog rheobatrachus silius. The female keeps the eggs in her stomach. The tadpoles are expelled through mouth after metamorphosis.

Feeding of larvae n n Denbrobates is the only amphibian known to feed their young's Viviparity: some anurans are ovoviviparous. They retain eggs in the oviduct and the females give birth to living young African toads nectophrynoids and pseudophyryne give bith to little toad. The European salamander salamandra salamamdra a produce 20 or more small young while alpine salamander S. atra gives birth to one or two fully developed young.

Parental care in reptiles n Internal fertilization and terrestrial reproduction are fully developed among reptiles. Few eggs well supplied with yolk may be carried in side the mother’s body until they hatch or they may be placed in nest buried in the ground and given little subsequent care. Crocodiles are the exception in reptiles. They actively defend the nest and young for a considerable period of time.

Parental care in birds n 1. 2. 3. 4. Parental care behavior of birds includes the following activities: Nest construction Incubation of eggs Care of young's Feeding the young ones

Nest construction n n Most bird species build nest that is a structure in which the eggs are laid and then incubated. A majority of species of birds true nest which range in complexity from simple collection of sticks to those requiring varying degrees of care and precision in the formation of completed nest cups.

Types of nests n n A nest may be a mere pit in sand. (ostrich) A loose framework of twigs (Dove) A cup woven of plant materials (many song birds) A hanging retort completely woven of strips of coarse saw edge grass and paddy (weaver nest)

Incubation of eggs n n n Incubation is the process by which the heat necessary for embryonic development is applied to an egg after it has been laid. This done by sitting on the eggs. The incubating of eggs is almost always necessary in birds. Because birds are warm-blooded , the embryo will die if the egg is allowed to cool for long. The duration of incubation is in general related to the size of the bird. It varies from 12 to 14 days for smaller birds and from 40 to 50 days for large birds.

n n Eggs of the royal albatross have the longest incubation period about 80 days. Some birds such as hawk, owl, etc incubates eggs as soon as each is laid. This produce “stair step” family.

n n n In many small, active song birds the incubating birds may leave the nest twice an hour or even often. In some gallinaceous birds (turkey, pheasants and quails) the birds may leave the nest once a day. In albatrosses , the attentive periods of each parent may last several days, during which time the sitting bird fasts completely. In some parrots the female incubates almost continuously being fed by the male. The emperor penguin, the male alone incubates continuously for the whole 60 day period and eats nothing. ( shows sacrifice)

Care of the young n n n The young birds at the time of hatching are of two types : Precocial: Such as quail, fowl and duck are covered with down (feathers) at hatching and can run or swim as soon as their plumage dries up. Altricial: such as swift are naked, blind and helpless at hatching and remain the nest for a week or more.

Feeding the young ones n n The chief avian method of parental feeding of the young are carrying food to the nest in the bill and placing it in the open mouth of nestling. The pigeon is unique in feeding its young with pigeon’s milk, which is come out from lining of crop.

n The specialized form of parental protective behavior known as “ injury feigning” is common among shore birds and water fowl, where its chief function is probably to distract predator from eggs or juvenile birds.

Parental care in mammals n Parental care in prototheria : female duck -bill or platypus is oviparous. Eggs are large with much yolk and plastic shells. There occurs no uterine gestation. Eggs are incubated by mother and newly hatched youngs are very immature. They are fed on milk in abdominal pouch till fully developed.

Parental care in metatheria n n Female metatherians are viviparous. Gestation period is small , two weeks in opossum and five weeks in kangaroo. The baby reaches the pouch of the mother and take a nipple of the mammary gland in the mouth.

Parental care in eutheria n Eutherians, like their closest relatives the marsupials, give birth to live young. In eutherians, however, the young are nurtured within the body of the mother by the placenta, which allows nutrients to pass from the blood of the mother almost directly into the blood of the young. The placenta also allows oxygen to reach the developing young, thereby making more energy available than in marsupials

n n The young animals will remain with their mothers until they are between four and five years old, even if their mother has given birth to a new infant Spider monkey mothers exhibit a behavior called 'bridge-gapping' in which they form a bridge with their bodies between two trees and allow their juvenile offspring to climb across them between trees. The females use their prehensile tails, adept grasping feet, and hands to form a stable bridge for the young spider monkeys to cross and aid them in crossing distances that are too large for the young animals to navigate on their own

n After a gestation period of around 110 days, a lioness gives birth to between two and four cubs in a den away from the pride. She will not introduce them to the pride until they are around six weeks old. After this, cubs are raised communally, suckling from any lioness who is lactating

n All the mothers in this study were observed to feed the pups by regurgitation. For the first 2 weeks immediately after parturition, the lactating females were observed to be more aggressive to protect the pups. The four males (male parents) were in contact with the litters as ‘guard’ dogs for the first 6– 8 weeks of litters’ life. In absence of the mothers, they were observed to prevent the approach of strangers by vocalizations or even by physical attacks. Moreover, one male fed the litter by regurgitation showing the existence of paternal care in free-roaming domestic dogs.

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