In our last blog we featured the picture here as a hint about what is coming to the Lab – were you able to guess what it is? If not, here’s a hint: what you’re seeing is actually an egg case. The dark round spot in the photo is a yolk sac and attached to that is a special type of fish that will be living with us here at the Lab until it grows too large to be responsibly housed here. The fish itself is a type of elasmobranch – a cartilaginous fish. Elasmobranchs include sharks, skates, and rays and what you are seeing in the picture is a baby shark developing in its egg case!
This particular shark is a member of the Genus Chiloscyllium which includes cat or bamboo sharks. This particular egg case is most likely a Chiloscyllium punctatum or banded cat shark. The time in the egg case is a critical time for these sharks as they are developing and growing until such time as they are large enough to make their way out by squeezing through the end of the egg case. It can take these sharks anywhere from 6 weeks to 4 months to hatch depending on conditions and their rate of growth. When these sharks hatch they are only about 5” long and must learn to fend for themselves. These sharks are benthic which means that they spend most of their time on the seafloor. They are also nocturnal and spend most of the day hiding in dark caves or crevices in the rocks. They come out at night to hunt their prey which is mostly invertebrates such as mollusks and crustaceans, returning to shelter after they have eaten. Unlike some of their more famous cousins, these sharks have very small teeth and use them like molars in that they use their teeth to crush their prey and break through any shells or exoskeletons they may have rather than sawing through them like pelagic sharks.
Cat or bamboo sharks, two of the common names for this Genus of shark, are very docile creatures and don’t actively swim, spending the majority of their time being sedentary. These benthic sharks are often seen “walking” across the sand using their pectoral and anal fins as feet. This does not mean that they cannot swim, however, and if frightened, they can dart away very quickly using their powerful bodies. These sharks also stay relatively small, reaching lengths of only around 4’ in length, although these will most likely not reach that size in captivity.In addition to our banded cat shark which hatched in the Spring, we also have two egg cases which have developing sharks. One of these is likely to hatchsometime this summer. The second one is still very early in its development and, although it has more than tripled in size since we brought it to the Lab, it is still not much bigger than a small section of a USB cable!
Check back soon…everyone’s favorite fish arriving soon!