Pleuroncodes planipes

Pleuroncodes planipes, sometimes called the pelagic red crab (or simply "red crab"), tuna crab or langostilla, is a species of squat lobster from the eastern Pacific Ocean.

Description

Pleuroncodes planipes is a bright red animal, up to 13 centimetres (5.1 in) long.^[1] It resembles a lobster, but has a shorter abdomen.^[2]

Taxonomic history

Pleuroncodes planipes was first described by William Stimpson in 1860.^[3] In his description, Stimpson noted that P. planipes was very close to P. monodon,^[4] the only other species in the genus.^[3]

Distribution

Pleuroncodes planipes lives on the continental shelf west of Mexico, and is unusual among members of the Galatheidae in that it lives in shallow water.^[5] It is usually found only south-west of San Diego,^[1] but in warmer years, its range may extend northwards into California.^[5] This is usually indicative of an El Niño event.^[6] Large numbers occasionally wash up on beaches,^[5] possibly after the animals have been swarming in order to mate.^[7] The southern limit of the species' range is in Chile.^[8]

Life cycle

The life cycle of Pleuroncodes planipes appeared for a long time to form a paradox: while an adult population was maintained along the south-western coast of the United States, the planktonic larvae they released were immediately swept by the California Current thousands of miles out to sea. A solution was proposed whereby the larvae use an opposing undercurrent at a lower depth to return to the continental shelf, and this hypothesis was confirmed by sampling different depths of water with a plankton recorder.^[9]

Ecology

Pleuroncodes planipes usually feeds on protists and zooplankton, but will feed by filtering blooms of diatoms.^[10]

As the most abundant species of micronekton in the California Current, Pleuroncodes planipes fills an important ecological niche converting primary production into energy that larger organisms can use.^[11] P. planipes is accordingly an important food item for many species of birds, marine mammals and fish. It is favoured by tuna, leading to one of the species' common names – "tuna crab".^[1] Other fish known to feed on P. planipes include billfishes, yellowtail amberjack, sharks^[12] and Epinephelus analogus.^[13] The diets of gray whales,^[14] Bryde's whales,^[15] blue whales^[15] and sea otters^[16] all include P. planipes. The Mexican endemic bat Myotis vivesi also feeds on P. planipes at some times of the year.^[17] Off Baja California, the stomachs of some loggerhead sea turtles have been observed to contain only P. planipes.^[18] Since P. planipes may be washed ashore in large numbers, it can be a valuable addition to the diets of seabirds such as the herring gull (Larus argentuatus), whose food supply is usually diminished in El Niño years.^[19]

References