Shark oviparity is characterised by the
production of relatively large egg cases, encapsulation of
fertilised embryos in structurally complex and remarkably durable
shells, and an incubation period lasting months to over a year (Hamlett, 1999).
Following insemination and storage of sperm, egg capsules are
laid at daily to weekly intervals for periods of several months (Mellinger,
1983). Enough
evidence exists to suggest that females select sites to lay eggs and
attach them to suitable substrata, perhaps returning to these places
year after year. After
laying the eggs, embryonic development proceeds without further
maternal contributions.
Essentially all of the nutrients necessary for development to
hatching are contained in the egg itself, although water, minerals
and possibly other solutes may be sequestered from the environment.
Approximately 40% of all shark species and all known skates
employ oviparity of this type, however, no rays are known to be
oviparous (Hamlett, 1999).
Video below shows the hatching of a bamboo shark, filmed by SOS.