Deep-sea emarginate snailfishCareproctus furcellus, raised at the Primorsky Aquarium, have joined the other inhabitants of the Polar World exhibit.
This story began in late 2024, when Mikhail Vakula, an employee of the crab harvesting Russian Crab Company Group, discovered some egg masses deposited inside the gill cavities of golden king crabs (Lithodes aquispinus) during an expedition to the Sea of Okhotsk. He delivered the egg samples to the Primorsky Aquarium, where biologists managed to incubate and hatch the eggs. Later, they determined the new inhabitants of the Aquarium as the emarginate snailfish Careproctus furcellus. This deep-sea species is found in the northern Pacific Ocean (along the coast of Japan, in the Sea of Okhotsk and in the Bering Sea) at depths from 100 to over 1000 meters. The fish grows up to 50 cm in length and lives on the seabed.
At the Primorsky Aquarium, the juvenile fish were reared for a year before being moved to the exhibit. After hatching, the fry were fed live nauplii — brine shrimp (Artemia) larvae. Six months later, frozen mysis shrimp were added to their diet. Now, mysids constitute the main food of the fish. The newcomers belong to one of the most unusual and understudied fish family — snailfishes (Liparidae). The family includes approximately 32 genera and at least 450 species, found in oceans worldwide. Snailfishes hold the record for the deepest-dwelling fish: some species of the family have been filmed by robotic submersibles at a depth of more than 8000 meters underwater.
Adult snailfish. Photo by A.V. Chernyshev. 2005, R/V Akademik Oparin’s voyage to the Kuril Islands.
They are distinguished by a disc on their belly that allows them hold on tight to rocks. The disc is absent in about half of the snailfish species, those living in the pelagic zone, which helps them actively move in the water.
Many liparid fishes lay their eggs inside the gill cavity of crabs or in other invertebrates, which they use as shelter Unwitting host invertebrates provide protected habitat for the developing eggs, thereby significantly increasing their survival. This reproductive strategy was first described by Japanese scientists in the early 20th century and repeatedly validated by Russian and international studies starting from the 1950s.
Assistant Director for Biology of the Primorsky Aquarium, Dr. Dmitry Pitruk, highlighted the scientific importance of the research. “We are the first in the world to have reared emarginate snailfish in captivity,” said Dr. Pitruk, who has been studying the liparids or many years. “Unique data on Careproctus furcellus development and growthwill be used in research papers on snailfish”.
The unusual creatures are on display at the Polar World exhibit, in an aquarium located next to a life-sized polar bear sculpture. Another species of snailfish, Agassiz’s snailfish (Liparis agassizii), which inhabits the coastal waters of the Northwestern Pacific, is featured in the Bering Sea and Sea of Okhotsk exhibit.
