Halocaridina
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| Halocaridina rubra Holthuis, 1963 |
Halocaridina rubra is a small red shrimp of the family Atyidae, with the common Hawaiian name Ōpae'ula (Hawaiian etymology: meaning "red shrimp").
It is a small red shrimp, rarely longer than 1.5 cm in length, typically found in brackish water pools near the seashore, sometimes in large numbers. Such pools are referred to as anchialine pools (from the greek anchialos = near the sea).
'Ōpae'ula are herbivorous and detritivorous shrimp occupying both hypogeal (subterranean) and epigeal (surface) anchialine waters. They are endemic to the Hawaiian islands, and most commonly found in anchialine pools in fresh lava substrates on Hawai'i and Maui Island, but have been found in limestone karst pools and hypogeal habitats in limestone on older islands, such as O'ahu.
Typical food of 'ōpae'ula is algal and bacterial mats on the surface of rocks and other substrates in anchialine pools. Chelipeds are adapted for scraping and filtering of algal-bacterial layers. See, for example:
The Hawaiian endemic shrimp Halocaridina rubra holthuis currently inhabits anchialine pools on Maui, Kaho'olawe, O'ahu, Moloka'i, and Hawai'i islands. Information is presented on the feeding, reproductive, and sensory biology of these shrimp. Feeding cheliped setae are of two types, serrated setae that scrape the substrate surface and filamentous setae that collect the loosened food materials or act as filters. The shrimp are primarily microphagous grazers that scrape the surface of the algal-cyanobacterial crust on pool substrates. This grazing activity is essential in maintaining the integrity of the crust, an actively growing matrix of plants, bacteria, diatoms, protozoans, and underlying siliceous and carbonate materials. Filter feeding is only observed in pools with dense phytoplankton blooms. The first and second pleopods of male and female shrimp are illustrated, and reproduction in captive populations from Hawai'i and O'ahu locations is described. Sense organs examined include the eye, aesthetasc hairs, campaniform sensilla, ringed setae, and abdominal pits with flared setae. The anchialine shrimp H. rubra appears to be a generalist, feeds as a microphagous grazer or filter feeder, is well adapted to the epigeal-hypogeal habitat in the pools, reproduces in the subterranean portion of the habitat, and is equipped with sensory structures that detect motion and chemical changes in the environment. Survival of this endemic species is dependent upon the continued integrity of its habitat, which is unique and sparsely represented on five of the eight high Hawaiian Islands.
Recent popularity of 'ōpae'ula as a low-maintenance pet in Hawai'i and elsewhere has brought this otherwise obscure decapod crustacean into popular consciousness. A long-lived species, 'ōpae'ula have been known to live for as long as 20 years in captivity. Sexes are difficult to distinguish, but gravid females carry clusters of red/maroon eggs under their pleopods, and early larvae are planktonic filter-feeders.
[edit] References
- Bailey-Brock, J. H. & R. E. Brock. 1993. Feeding, reproduction, and sense organs of the Hawaiian anchialine shrimp Halocaridina rubra (Atyidae). Pacific Science 47(4): 338.355.
