Saturday, July 23, 2016

Baby chain dogfish ((cat) sharks

Chain dogfish Scyliorhinus retifer are more accurately catsharks, a large group of demersal sharks that have several characteristics not usually associated with "sharks": they spend most of their time resting still on the bottom because they are generally relatively poor swimmers; most are small (under 2 feet) and lay eggs in cases that look similar to those of skates, commonly called "mermaids' purses". 
Juvenile chain dogfish in its case

Juvenile dogfish the day it emerged 

After an incubation period of about 9 months (here at the VLM) or up to a year depending upon water temperature, the young sharks emerge from the cases fully formed, as do skates.

A just lain Little skate Raja erinacea egg case

A pair of week old Little skates

The mated pairs of chain dogfish are currently on exhibit and continually produce egg cases at a rate of about one every two weeks. Females will wrap the tendrils of the egg cases around structure to anchor them during incubation, but it also helps her literally pull the case out of her body. In the exhibit, she expertly wraps the cases around a display box in which we display developing embryos. 

The egg cases are anchored by strands that the female wraps around a solid object

We will keep the juveniles in a holding system until they are large enough to display with the adults. 





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