''Abergasilus amplexus'' is a species of parasitic copepod

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 euryhaline habitats in

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

. It is the only known species in the genus ''Abergasilus''.

Description

This species is unique among ergasilids in that it only has three pairs of legs: the fourth and fifth pairs are reduced to single spines or are completely absent. The second antenna is very distinctive, hooks on the last and penultimate segments creating an obviously claw-like structure, more obvious in the female. The male is free-living, forming part of the

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 ...

. Both sexes have an average length of 0.5 mm.

Hosts

The main host appears to be ''

Anguilla australis The short-finned eel (''Anguilla australis''), also known as the shortfin eel, is one of the 15 species of eel in the family Anguillidae. It is native to the lakes, dams and coastal rivers of south-eastern Australia, New Zealand, and much of th ...

'': in Lake Ellesmere, infestation rates on this eel approach 100%, sometimes with over 100 parasites on the gills of a single fish. Other recorded host species include '' Anguilla dieffenbachii'', '' Arripis trutta'', ''

Carassius auratus The goldfish (''Carassius auratus'') is a freshwater fish in the family Cyprinidae of order Cypriniformes. It is commonly kept as a pet in indoor aquariums, and is one of the most popular aquarium fish. Goldfish released into the wild have ...

'', ''

Galaxias maculatus The common galaxias (''Galaxias maculatus'') or inanga (from the Māori ''īnanga'') is a very widespread Southern Hemisphere fish in the family Galaxiidae. It is a slim, narrow fish with a forked tail and a mottled, spotty pattern, typically a ...

'', ''

Perca fluviatilis The European perch (''Perca fluviatilis''), also known as the common perch, redfin perch, big-scaled redfin, English perch, Euro perch, Eurasian perch, Eurasian river perch, Hatch, poor man’s rockfish or in Anglophone parts of Europe, simply th ...

'', '' Pseudophycis bachus'', '' Retropinna retropinna'', '' Rhombosolea leporina'', '' Rhombosolea plebeia'' and '' Rhombosolea retiaria''.

References

{{Taxonbar, from=Q18591905, from2=Q4667083 Poecilostomatoida Monotypic crustacean genera Freshwater crustaceans of New Zealand Endemic fauna of New Zealand Animal parasites of fish Endemic crustaceans of New Zealand