by Martha Nizinski, NOAA/NMFS National Systematics Laboratory, National Museum of Natural History
June 22, 2018
Through images shared by NOAA Ship Okeanos Explorer’s eye in the deep sea, the remotely operated vehicle Deep Discoverer, we have been treated to amazing insights into the lives and behaviors of a variety of deep-sea decapod crustaceans. Most of us are familiar with the 10-legged creatures that show up on our dinner plates, but more than 15,000 species of decapods, many of which inhabit the deep sea, have been described to date. About two thirds of these species are crabs (true crabs and anomuran crabs combined). Expeditions to new and unexplored areas in the deep oceans continue to reveal species new to science.
Given the remoteness of their habitats, we very seldom have opportunities to see deep-sea organisms in their natural environment, so we know very little about their life history and behavior. On this particular day, we were provided a glimpse into the secret lives of two types of deep-sea crabs, Neolithodes sp. and Chaceon sp.
Two species of Neolithodes likely occur in the region. These crabs, related to the frequently consumed king crab, belong to the family Lithodidae. The carapace and walking legs are covered in long spines, giving this crab a distinctive appearance and justification for its common name, “porcupine crab.” Most large crabs, including these lithodids, are scavengers or predators, but few specifics on what the porcupine crab eats are known. One claw is larger than the other, and this is probably used for crushing prey, while the smaller claw is likely used for handling and manipulating prey prior to consumption. Our observations during this dive revealed that this neolithodid crab eats other decapod crustaceans.
More is known about the other large crabs, the deep-sea red crab (Chaceon quinquidens) and its relative the golden crab (C. fenneri), that occur in this region. These species occur in sufficient abundance to support small commercial fisheries. Chaceonid crabs are reported to be opportunistic feeders, eating a variety of benthic infauna and epifauna, including mollusks and polychaete worms. Demersal fishes are also sometimes on the menu, as well as squid and larger crustaceans, as we observed during this dive. Reports of sponges and hydroids in their diets suggest that these crabs eat fauna attached to hard surfaces such as canyon walls or other exposed hard substrata. They also scavenge dead falls. Another study reported that red crabs do not stop feeding during mating, an unusual behavior that may be an adaptation to the uncertainty of the timing of the next meal and an extended coupling period. The amount of time a male “cages” the female can be several weeks.