3.OVIPARY, OVOVIVIPARY, VIVIPARY – terms used to describe what happens when future offspring separates from parent OVIPARY – eggs are released and develop outside body of female, fertilisation internal or external, egg yolk only nutrition. OVOVIVIPARY – Internal fertilisation, egg shell soft, eggs hatch inside body, appears to be born alive, egg yolk nutrition, mother for protection. VIVIPARY – fertilisation internal, no egg shell, nutrition via placenta. Lorraine Kuun, July 2011

OVIPARY in aquatic conditions Most fish, amphibians and lower aquatic forms. Needs large numbers of eggs. Larval stage self-sufficient; don’t compete with parents – use different food sources. Eggs and larvae easily dispersed. Lorraine Kuun, July 2011

OVIPARY in terrestrial (land) environments – maximising reproduction Invertebrates produce large numbers of eggs to ensure survival (no or little parental care). Protective shell prevents embryo from drying out. Fewer eggs in e.g. birds and reptiles – energy can be used for more food in egg (yolk and albumin), hatching and protection, parental care. Development of amnion important factor in success. Lorraine Kuun, July 2011

Hard shell good protection for developing embryo; prevents embryo from drying out. Lorraine Kuun, July 2011

Shark egg pouch with yolk clearly visible Lorraine Kuun, July 2011

OVOVIVIPARY – how is reproduction maximised? Fewer eggs needed – higher survival rate of offspring. Developing embryo much less vulnerable to predators. Developing embryo not subject to environmental changes e.g. temperature. Young born fully developed, can feed and escape predators more easily. Occurs in some invertebrates, fish and reptiles. Lorraine Kuun, July 2011

Dogfish embryo with yolk sac Lorraine Kuun, July 2011

Lorraine Kuun, July 2011

Young puff adder being “born alive” after hatching inside mother; note position of cloaca. Lorraine Kuun, July 2011

VIVIPARY maximising reproduction Occurs in placental mammals, some sharks and scorpions Fertilisation internal, no shell Placenta responsible for nutrition – young born alive 1. fewer eggs necessary 2. energy available for nourishment and protection of embryo, as well as parental care Lorraine Kuun, July 2011

Lorraine Kuun, July 2011

4. Precocial vs. Altricial development Born or hatched when not well-developed Young hatch or born when almost fully developed Often naked, lacking hair or down Open eyes, hair or down Cannot walk or fly Confined to nest or burrow Active or mobile Not confined to nests Energy goes into parental care after birth Energy goes into prenatal development ALTRICIAL Lorraine Kuun, July 2011

PRECOCIAL ANIMALS Ground-nesting birds e.g. Penguins, domestic poultry, ostriches Large mammals e.g. Elephants, species of antelope, horses etc Allows young to fend for itself, feed and stay warm Stay with herd for protection against predators Learn from older individuals in herds OFFSPRING HAS GOOD CHANCE OF SURVIVAL Lorraine Kuun, July 2011

Left: Penguin chick and Above: foal, both mobile soon after birth Lorraine Kuun, July 2011

ALTRICIAL ANIMALS Small animals that produce big litters e.g. mice, rats, cats, dogs Tree-nesting birds that have nests away from predation Humans (see human reproduction) Altricial species need parental care for a long time – usually female that does the caring, male sometimes involved. Birds usually have mouth-lining or gape-edge Mammals small and immature brains Lorraine Kuun, July 2011

Altricial bird – see mouth-lining that attracts mother Lorraine Kuun, July 2011

cared for by mother (left); Kittens born weak and totally Mice survive in broods, cared for by mother (left); Kittens born weak and totally dependent on mother (below) Lorraine Kuun, July 2011

5. The Amniotic egg Adaptation of later vertebrates; can lay eggs in terrestrial environment. Amniotic egg has fluid-filled, extra-embryonic membranes that prevents embryo from drying out. Earlier vertebrates lay eggs in water; need to return to water/live in water to reproduce. Amniotic egg lessens dependence on water for reproduction. Lorraine Kuun, July 2011

The Amniotic egg Fertilisation is internal. Extra-embryonic (not part of embryo) membranes only develop after fertilisation. Membranes are: Amnion Allantois Yolk sac Chorion Major evolutionary development; allowed first reptiles to colonise land! Lorraine Kuun, July 2011

The Amniotic egg Lorraine Kuun, July 2011

How does the amniotic egg maximise reproduction? The fluid-filled amnion surrounds and protects the embryo, especially against dehydration and shock. Allantois acts as reservoir for nitrogenous waste in birds and reptiles. Yolk sac holds nutritious food for development of embryo. Chorion surrounds all other membranes: in birds it allows for gaseous exchange; in mammals it forms the placenta (taking over functions of allantois and yolk sac, amongst others (see human reproduction). Lorraine Kuun, July 2011

Amniotic egg as seen in human embryonic development Lorraine Kuun, July 2011

6. Parental care Any pattern of behaviour in which parent spends time or energy to improve the 1survival, 2condition and 3future reproductive success of offspring. Care can be given at any stage: Prenatal – guarding eggs, building nests, carrying broods, incubating eggs and placental nourishing. Post-natal – providing food, protecting offspring, teaching offspring. Lorraine Kuun, July 2011

Little or no parental care Little or no parental care means a low reproductive effort. Reproductive energy put into producing masses of eggs. High mortality rate amongst eggs as well as young. Few individuals survive to reproductive age. E.g. Most fish, amphibians, insects, most reptiles Lorraine Kuun, July 2011

When parental care is given Few eggs or young produced. Low mortality rate amongst eggs or young. High reproductive effort. Reproductive energy goes into parental care after birth (post-natal). Most offspring survive to reproductive age. E.g. Mammals, birds, some reptiles, exceptions amongst fish and Arthropods. Lorraine Kuun, July 2011

Right: chicken laying egg, mother feeding young Left: Midwife toad

Left: Male seahorse with young emerging from breeding pouch Ovovivipary type of parental care Left: Male seahorse with young emerging from breeding pouch Lorraine Kuun, July 2011

Lorraine Kuun, July 2011