Abergasilus
Encyclopedia
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.
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
. Both sexes have an average length of 0.5 mm.
, 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.
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
endemic to euryhaline
Euryhaline
Euryhaline organisms are able to adapt to a wide range of salinities. An example of a euryhaline fish is the molly which can live in fresh, brackish, or salt water. The European shore crab is an example of a euryhaline invertebrate that can live in salt and brackish water...
habitats in New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. It is currently the only known species in the genus Abergasilus.
Description
This species is unique among ergasilidsErgasilidae
Ergasilidae is a widespread family of copepods and comprises many species. The type genus is Ergasilus. With a few doubtful exceptions all ergasilids are parasitic on fishes.-Biology:...
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
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
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
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
. Both sexes have an average length of 0.5 mm.
Hosts
The main host appears to be Anguilla australis: in Lake EllesmereLake Ellesmere
Lake Ellesmere / Te Waihora is located in the Canterbury Region of the South Island of New Zealand. It is actually a broad, shallow lagoon located directly to the west of Banks Peninsula, separated from the Pacific Ocean by a long narrow sandy spit called Kaitorete Spit, or more correctly Kaitorete...
, 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.