While exploring along Pichincho Wall at depth ranges of 250-366 meters (820-1,200 feet) during the Océano Profundo 2018 expedition, we encountered this embryonic cat shark and egg case attached to an octocoral colony.
Sharks that are “oviparous” lay eggs outside the mother’s body and provide no parental care to the next generation. A yolk sac inside the egg case provides the embryo with all the nutrients necessary for its development. Egg cases are attached to invertebrates or algae via long strands that coil around a solid base during the few months until hatching. After completing its development, the shark pup will emerge from the case and be ready to swim in order to maximize its survival chances.
While we’d seen these cases on previous expedition dives, they had all been empty. The fact that we saw this one, alive and directly linked to a coral colony, tells us a lot about how important deep-sea corals are as nursery habitats for fishes and other organisms.
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Video courtesy of the NOAA Office of Ocean Exploration and Research, Exploring Deep-sea Habitats off Puerto Rico and the U.S. Virgin Islands.