''Idiomysis'' is a genus of small

mysids Mysida is an order of small, shrimp-like crustaceans in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch or "marsupium" in females. The fact that the larvae are reared in this ...

found in warm, shallow waters of Indian Ocean (including Red Sea) and Pacific.

Anatomy

Mysids from the genus ''Idiomysis'' are just few millimeters length; their

cephalothorax The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...

is gibbous and robust whereas the abdomen is characteristically curled up behind. When compared with other mysids, ''Idiomysis'' has short antennae, relatively big eyes and small, usually unarmed telson, however a single species, ''I. diadema'', possesses a pair of short terminal spines.

Systematics

There are six species described so far in the genus: * ''

Idiomysis diadema ''Idiomysis'' is a genus of small mysids found in warm, shallow waters of Indian Ocean (including Red Sea) and Pacific. Anatomy Mysids from the genus ''Idiomysis'' are just few millimeters length; their cephalothorax is gibbous and robust ...

'' Wittmann, 2016 * ''

Idiomysis inermis ''Idiomysis'' is a genus of small mysids found in warm, shallow waters of Indian Ocean (including Red Sea) and Pacific. Anatomy Mysids from the genus ''Idiomysis'' are just few millimeters length; their cephalothorax is gibbous and robust ...

'' W. Tattersall, 1922 * '' Idiomysis japonica'' Murano, 1978 * '' Idiomysis mozambica'' Deprez, Wooldridge & Mees, 2001 * '' Idiomysis robusta'' Connell, 2008 * ''

Idiomysis tsurnamali ''Idiomysis'' is a genus of small mysids found in warm, shallow waters of Indian Ocean (including Red Sea) and Pacific. Anatomy Mysids from the genus ''Idiomysis'' are just few millimeters length; their cephalothorax is gibbous and robust ...

'' Bacescu, 1973.

Ecology

''Idiomysis'' live in the small groups (called swarms) of 5 to more than 40 individuals, which hover over sea bottom during a day and probably feed on the seafloor on the nighttime. All known species are found in the shallow coastal waters, however they inhabit different niches and can be found on coral reefs, seaweeds, rocks or sandy bottoms. Two species – ''I. inermis'' and ''I. tsurnamali'' – are known for commensal relationship with the

sea anemone Sea anemones are a group of predation, predatory marine invertebrates of the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemones are classifi ...

s, whereas ''I. diadema'' is associated with the sea urchin '' Diadema''. There are also reports of ''Idiomysis'' hovering above upside-down jellyfish, Cassiopea. Possibly mysids gain protection and/or food supply from this relationship, however the exact nature of the relation has not been studied.

Distribution

The described species are known from Red Sea (''I. diadema'' and ''I. tsurnamali''), Mozambique Channel (''I. mozambica''), Gulf of Mannar (''I. inermis''), western coast of

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

(''I. inermis''),

East China Sea The East China Sea is an arm of the Western Pacific Ocean, located directly offshore from East China. It covers an area of roughly . The sea’s northern extension between mainland China and the Korean Peninsula is the Yellow Sea, separated b ...

(''I. japonica'') and western coast of South Africa (''I. robusta'').

References

External links

Movies of swarming ''Idiomysis'' on realmonstrosities.com.
{{Taxonbar, from=Q4513446 Mysida