''Protognathia'' is a genus of marine

isopods Isopoda is an Order (biology), order of crustaceans. Members of this group are called isopods and include both Aquatic animal, aquatic species and Terrestrial animal, terrestrial species such as woodlice. All have rigid, segmented exoskeletons ...

belonging to the monotypic family Protognathiidae. The species of this genus are found in southernmost South Hemisphere, more specifically in the

Weddell Sea The Weddell Sea is part of the Southern Ocean and contains the Weddell Gyre. Its land boundaries are defined by the bay formed from the coasts of Coats Land and the Antarctic Peninsula. The easternmost point is Cape Norvegia at Princess Martha C ...

, where the type specimen was found at a water depth from 410 to 245 meters.

Species

The Genus contains the following species: *'' Protognathia bathypelagica'' *'' Protognathia waegeli''

Description

Isopods of this family (and genus respectively) are a morphologic intermediate between members of

Gnathiidae The Gnathiidae are a family of isopod crustaceans. They occur in a wide range of depths, from the littoral zone to the deep sea. The adults are associated with sponges and may not feed. The juvenile form is known as a 'praniza', and it is a temp ...

and Cirolanidae, which is why the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, ''Protognathia bathypelagica'', was at first misidentified as ''Cirolana bathypelagica''. Their pleonites are not fused. Pereonites four to six are larger than the remaining segments, and the seventh pereonite is about as large as a pleonite. The seventh pereopod is absent. The

uropods Uropods are posterior appendages found on a wide variety of crustaceans. They typically have functions in locomotion. Definition Uropods are often defined as the appendages of the last body segment of a crustacean. An alternative definition sugge ...

are flat and slender, almost as long as the

pleotelson The telson () is the hindmost division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on account of ...

. Members of this genus have a tail fan and lack eyes. All pleopods have similar outlines, with large branches.

Ecology

While its mandibles resemble those of cirolanid isopods, it is not used as a cutting instrument, as they have a pronounced point probably used for stinging. This then suggests a bloodsucking,

ectoparasitic Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The en ...

ecology.

References

Isopod genera Cymothoida {{isopod-stub