Abergasilus

Abergasilus amplexus
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Crustacea
Class:	Maxillopoda
Subclass:	Copepoda
Order:	Poecilostomatoida
Family:	Ergasilidae
Genus:	Abergasilus
Species:	A. amplexus
Binomial name
Abergasilus amplexus Hewitt, 1978

Abergasilus amplexus is a species of parasitic copepod endemic to euryhaline habitats in New Zealand. It is currently the only known species in the genus Abergasilus. The main host appears to be Anguilla australis: 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, Galaxias maculatus, Perca fluviatilis, Pseudophycis bachus, Retropinna retropinna, Rhombosolea leporina, Rhombosolea plebeia and Rhombosolea retiaria.

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 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. Both sexes have an average length of 0.5 mm.

References

• G. C. Hewitt (1978). "Abergasilus amplexus gen. et sp. nov. (Ergasilidae; parasitic Copepoda) from fishes in Lake Ellesmere, New Zealand". New Zealand Journal of Marine and Freshwater Research. 12 (2): 173–177. {{cite journal}}: Unknown parameter |quotes= ignored (help)
• J. B. Jones (1981). "Abergasilus amplexus Hewitt, 1978 (Ergasilidae: Copepoda) from New Zealand, with a description of the male". New Zealand Journal of Marine and Freshwater Research. 15: 275–278. {{cite journal}}: Unknown parameter |quotes= ignored (help)