Glossary

embryo

A young, unborn or unhatched organism in the process of development.

Used in 11 species profiles

chondrocranium
Primitive, cartilaginous skeletal structure enclosing the brain and inner ear formed in the embryo and usally becoming ossified at a later stage. Retained as cartilage throughout life in some fishes.
egg
Object laid by a female bird, reptile, fish, or invertebrate, normally roun or oval-shaped and containing a developing embryo surrounded by nutrient material and a protective case or shell; a female gamete; an ovum.
eyed egg
A fish egg within which the embryo has developed to a point whereby the eyes are visible through the external membrane.
lecithotrophy
Literally, 'feeding on yolk'. A form of development in which an embryo receives no nutrition other than the yolk contained within its egg.
matrotrophy
Reproductive strategy in which the embryo is supplied with additional nutrition from the mother, applied to some viviparous fishes.
ontogeny
The origin and development of an individual from embryo to adult.
ovoviviparity
Reproductive strategy in which fertilisation occurs internally and the eggs develop inside the body of the mother until hatched, at which point live offspring are born. There is no placental connection between mother and embryo unlike in viviparous species.
yolk
Substance in an animal egg consisting of protein and fat that nourishes the developing embryo.
yolk sac
A membranous sac containing yolk attached to the ventral surface of embryos and early larvae in some fishes. Retained for a period post-hatching in those species which form yolk sac larvae.