For a long time, it has been thought that egg-laying sharks have two different breeding methods:
1) Single oviparity - where one egg-case is held in the oviduct for a short period and then released
2) Multiple oviparity - where multiple egg-cases are held for a longer period and released when the embryos in the case have developed to a larger size
The Sarawak swellshark Cephaloscyllium sarawakensis has recently been discovered to have a new method called 'sustained single oviparity' that combines both methods - a single egg-case is held for a long period and released once the embryo has grown to within 50-80% of its hatching size. While this reduces the fecundity of the swellshark, it allows the young sharks to reach maturity quicker.
Much more interesting, personally speaking, is that the species also produces a unique egg-case. While other egg-laying sharks have camouflaged cases of green or brown, the egg-cases of the Sarawak swellshark are glass-like and transparent, even after being released. The embryo has vivid polka-dot patterns when inside the case, possibly to camouflage it.
The paper is included below:
Discovery of a new mode of oviparous reproduction in sharks and its evolutionary implications | Scientific Reports
1) Single oviparity - where one egg-case is held in the oviduct for a short period and then released
2) Multiple oviparity - where multiple egg-cases are held for a longer period and released when the embryos in the case have developed to a larger size
The Sarawak swellshark Cephaloscyllium sarawakensis has recently been discovered to have a new method called 'sustained single oviparity' that combines both methods - a single egg-case is held for a long period and released once the embryo has grown to within 50-80% of its hatching size. While this reduces the fecundity of the swellshark, it allows the young sharks to reach maturity quicker.
Much more interesting, personally speaking, is that the species also produces a unique egg-case. While other egg-laying sharks have camouflaged cases of green or brown, the egg-cases of the Sarawak swellshark are glass-like and transparent, even after being released. The embryo has vivid polka-dot patterns when inside the case, possibly to camouflage it.
The paper is included below:
Discovery of a new mode of oviparous reproduction in sharks and its evolutionary implications | Scientific Reports