Day 318#: Velvet Belly Lanternshark
Today's animal of the day is the Velvet Belly Lanternshark (Etmopterus spinax)!
Photo credit: Andy Murch
Also sometimes referred to as simply velvet bellies, this small species of deep-sea shark can commonly be found in the northeastern region of the Atlantic Ocean at depths of around 66 to 8,169 feet! They are members of the order Squaliform, which is known as the dogfish order of sharks. While not the smallest species of deep-sea shark, they are still quite small and are usually no more than 18 inches long, with females usually being slightly larger than the males. Their name comes not from the texture of their bellies, but due to the black color of their undersides, which really stands out against the rest of their grayish-brown bodies.
Photo credit: Viktor V. Grøtan
Like other species of lanternsharks in the family Etmopteridae, the velvet belly has little bioluminescent patches on its flanks and abdomen, which make it resemble a school of smaller fish when in the dark. This helps the shark hide from larger predators who don't want to bother catching super tiny fish, as well as sneak up on unsuspecting prey. Speaking of prey, velvet bellies feed mostly on krill and small fish when they are younger, but as they grow and venture into deeper waters, their diet starts to change to larger shrimp and squids.
Photo credit: Vsevolod Rudyi
In addition to their bioluminescent patches, these sharks have several other adaptations to help them survive in the deep sea. They have incredibly large livers that take up around 17% of their body mass. This helps them filter out the various toxins and heavy metals that are common in the bodies of deep-sea creatures that they eat. However, their livers can't help protect them from parasites, which these sharks are especially prone to getting. This includes internal parasites like tapeworms and nematodes, as well as external parasites like barnacles that attach themselves to their gills, dorsal spines, and even their genitals.
Photo credit: Viktor V. Grøtan
Velvet bellies can be found both by themselves and in large schools. They are fairly common throughout their range, with a much higher percentage of females being observed compared to males. While they aren't often purposely caught by humans, deep-sea trawlers often catch them as bycatch while on the hunt for deep-sea shrimp and lobsters. When this happens, the velvet bellies are almost always thrown back, but still end up dying most of the time due to the pressure change. Because of this, and their slow reproductive rate, their population has decreased by almost 20%, and the species has been reclassified from Least Concern to Near Threatened.
