Mysids from the genus Idiomysis are just few millimeters length; their cephalothorax is gibbous and robust whereas the abdomen is characteristically curled up behindШаблон:R.[2] When compared with other mysids, Idiomysis has short antennae, relatively big eyes and small, usually unarmed telsonШаблон:R, however a single species, I. diadema, possesses a pair of short terminal spinesШаблон:R.
Systematics
There are six species described so far in the genusШаблон:R:
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.[3] 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 bottomsШаблон:R. Two species – I. inermis and I. tsurnamali – are known for commensal relationship with the sea anemonesШаблон:R, whereas I. diadema is associated with the sea urchin DiademaШаблон:R. There are also reports of Idiomysis hovering above upside-down jellyfish, CassiopeaШаблон:R. Possibly mysids gain protection and/or food supply from this relationship, however the exact nature of the relation has not been studiedШаблон:R.