Sciliorhinus hachijoensis
Carcharhiniformes:
Scyliorhinus hachijoensis in Shimoda floating aquarium. Source: 出羽雀台, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons.
It’s summer. That time of year when we return to the beach for some sun and fun, and when Peter Benchley’s contribution to western civilization, the novel and movie “Jaws,” returns to our front of mind. Recent shark attacks on Long Island, and National Geographic’s Sharkfest, are reminders of our uneasy fascination with, and primordial fear of, these fierce predators of the deep. And Charlie the tuna feels a sense of redemption, as we reveal ourselves to be the true chickens of the sea. What better time to celebrate these amazing animals… and the fact that we continue to discover sharks that we didn’t know existed?
There is so much interest in these creatures that even the discovery of small sharks is big news. Scyliorhinus hachijoensis is a recently discovered catshark from the Izu Islands of southeastern Japan. It differs from its closest relatives by coloration, proportional height of its anal fin, shape of its pectoral and pelvic fins, dermal denticles, and molecular sequence data. When an animal name ends in “-ensis,” it is named for a geographic place, generally the place where it was first discovered. In this case, the specific epithet refers to Hachijojima Island.
The genus Scyliorhinus includes 16 known species, ranging from about a foot in length to nearly seventeen inches. They are found in temperate and tropical waters, generally in water less than 500 meters deep, from the coast to the upper continental shelf.
Catsharks have elongated eyes that have been described as cat-like, and a pair of small dorsal fins set far back on their body. Most are small-sized sharks, under three feet, although the nursehound shark can be over five feet in length. Catsharks are noted for their impressive colorful patterns, whether spots, stripes, patches or saddles. Most have restricted geographic ranges, although the chain dogfish can be found in Atlantic waters from Massachusetts south to Nicaragua. Found in waters from shoreline to more than 6000 feet, most catsharks are associated with shallow water. They are bottom feeders, eating small-sized fish and various invertebrates, and unlike species, like the great white of the Jaws nightmare, they are no threat to swimmers. Resting in crevices during the day, they emerge at night to hunt.
A few catsharks are popular as pets among aquarium enthusiasts, such as the Australian marbled catshark, that rarely exceeds two feet in length, and the commonly kept coral catshark. To each his own.
Many catsharks deposit eggs on the sea floor in mermaid’s purses: leathery cases with curly tendrils at each end. In some species, eggs may take nearly a year to hatch. Rather than leaving them exposed on the sea bed for so long, they may hold on to them until a few months before they are due to hatch. There are also catsharks that are ovoviviparous, that is, they retain eggs with developing embryos until they are fully developed, then give live birth to baby sharks.
In all, the common name catshark applies to about 160 species in 17 genera, making the catshark family the most species-rich of all shark families. In total, there are more than 500 living species of sharks, no doubt including species yet to be discovered. Fossil scales are the earliest evidence of the existence of shark-like species about 430 million years ago. The largest living sharks are about thirty feet in length. For reference, the yellow school buses we are all familiar with are about 45 feet long. Until about three and a half million years ago, earth’s oceans were also home to Megalodon sharks, females of which could reach 58 feet! Experts assure us that shark attacks are rare, so I’m sure that tickle on your toes is just seaweed.
I’ll see you on the beach. Oh, and remember to bring your running shoes.
Further Reading
Ito, Nanami, Fujii, Miho, Nohara, Kenji, and Sho Tanaka (2022) Scyliorhinus hachijoensis, a new species of catshark from the Izu Islands, Japan (Carcharhiniformes: Scyliorhinidae). Zootaxa 5092: 331-349. https://doi.org/10.11646/zootaxa.5092.3.5