''Halocaridina rubra'', the Hawaiian red shrimp or volcano shrimp is a small red shrimp of the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Atyidae Atyidae is a family of shrimp, present in all tropical and most temperate waters of the world. Adults of this family are almost always confined to fresh water. This is the only family in the superfamily Atyoidea. Genera and species The followin ...

, with the common Hawaiian name (meaning "red shrimp").

Description and distribution

It is a small red shrimp, rarely longer than in length, typically found in

brackish water Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

pools near the sea shore, sometimes in large numbers. Such pools are referred to as anchialine pools (from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

' = near the sea). ''Halocaridina rubra'' is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to the Hawaiian islands, and most commonly found in anchialine pools in fresh

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

substrates on

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only state ...

and Maui Island; it has also been found in limestone karst pools and hypogeal habitats in limestone on older islands, such as

Oahu Oahu () ( Hawaiian: ''Oʻahu'' ()), also known as "The Gathering Place", is the third-largest of the Hawaiian Islands. It is home to roughly one million people—over two-thirds of the population of the U.S. state of Hawaii. The island of O� ...

. Its habitat is unique and sparsely represented on five of the eight high Hawaiian Islands (Maui, Kahoolawe, Oahu, Molokai and Hawaii).

Ecology

are

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...

and detritivorous shrimp occupying both hypogeal (subterranean) and epigeal (surface) anchialine waters. Typical food of is

alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

l and

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...

l mats on the surface of rocks and other substrates in anchialine pools.

Cheliped A chela ()also called a claw, nipper, or pinceris a pincer-like organ at the end of certain limbs of some arthropods. The name comes from Ancient Greek , through New Latin '. The plural form is chelae. Legs bearing a chela are called chelipeds. ...

s are adapted for scraping and filtering of algal-bacterial layers. Serrated setae scrape the substrate surface, and filamentous setae collect the loosened food materials. The latter can also act as filters for

filter feeding Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

during phytoplankton blooms. The grazing activity of this shrimp is essential in maintaining the integrity of the crust, an actively growing matrix of plants, bacteria, diatoms, protozoans, and underlying siliceous and carbonate materials. ''Halocaridina'' is well adapted to the epigeal-hypogeal habitat in the pools. It reproduces in the subterranean portion of the habitat.

Aquaria

Recent popularity of as a low-maintenance pet in Hawaii and elsewhere has brought this otherwise obscure decapod crustacean into popular consciousness. A long-lived species, have been known to live for as long as 20 years in captivity. Sexes are difficult to distinguish, but

gravid In biology and human medicine, gravidity and parity are the number of times a woman is or has been pregnant (gravidity) and carried the pregnancies to a viable gestational age (parity). These terms are usually coupled, sometimes with additional t ...

females carry clusters of red/maroon eggs under their pleopods, and early larvae are

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...

ic filter-feeders. They occasionally molt their shells, which can be seen as silvery exoskeletons at the bottom of the tank. There may be some evidence that mate after molting, or that molting and mating may be related. Stressed ʻōpaeʻula tend to hide, though if given plenty of places to hide they are more likely to venture into open spaces. are social creatures and are rarely seen fighting, in fact when unstressed they often cluster together while eating or sunbathing. Shrimp in tanks can also be seen cleaning themselves or swimming slow laps. The shrimp is the animal element of the Ecosphere closed-system aquarium.

Description and distribution

Ecology

Aquaria

References

Further reading