The youngsters of many marine organisms, both
those with and without backbones, lead a life and conduct their
survival, their feeding, their locomotion and their growth processes
in a completely different way to their sexually mature adult forms.
Invariably of course they are much smaller than the adults. Technically
most are called larvae, because before they achieve adulthood they
undertake such a fundamental change or series of changes that, just
as a caterpillar becomes a pupa and then a moth, or a tadpole becomes
a frog, so they too metamorphose from larval design and habit into
adult, or at least juvenile, design and habit.
Many are born as eggs, some as live larval
forms, some eggs are retained, hidden, disguised or fixed, others
are shed into the surface waters and are therefore called pelagic
eggs. From all the eggs, hatch pelagic larval forms or “water babies”.