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Halacaridae
Family of mites that is mostly marine From Wikipedia, the free encyclopedia
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Halacaridae is a family of meiobenthic mites found in marine, brackish, and freshwater habitats around the world. It includes more than 1100 described species belonging to 64 genera [1][2] It is the largest marine radiation of arachnids.[3]
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Description and life cycle
Summarize
Perspective
Halacarids have four pairs of legs (as adults and nymphs; see below), of which the first two pairs point forwards and the last two pairs point backwards. This is a synapomorphy of the group. Another synapomorphy are four plates on the dorsal surface of the body, except for several genera with reduction of certain plates.[4]
The life cycle of halacarids consists of egg, larva, 1-3 nymphal stages (protonymph->deutonymph->tritonymph) and adult. Additionally, between each of the free-living stages (i.e. except for the egg) is a quiescent pupal stage.[5]
- Eggs are usually deposited by an adult female in a substrate, with the help of an ovipositor.
- Larvae have three pairs of legs, with each leg five-segmented, and lack a genital plate.
- Protonymphs have four pairs of legs (as do all following stages), of which the fourth pair is five-segmented, and they usually have a distinct genital plate.
- Deutonymphs and tritonymphs have each leg six-segmented.
- Adults are often similar to the last nymphal stage, but they have an ovipositor (if female) or spermatopositor (if male).
Like mites in general, halacarids have a pair of palps. The palps usually have four segments each, but they are three-segmented in Simognathus and just two-segmented in Acaromantis.[3]
Halacarids of subfamily Copidognathinae have just a single nymphal stage. Additionally, the number of genital papillae is reduced to a single pair.[3]
The subfamily Rhombognathinae, which is algivorous, can be recognised by the dark green or almost black pigment inside their digestive system. This pigment is partially digested chlorophyll from algae.[3]
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Ecology
Halacaridae occur in various habitats including sandy beaches, tidal sediment, interstitial spaces, hydrothermal vents, mangroves, salt marshes and on larger animals.[2][6] They spend their entire lives on a substrate such as attached algae or sand.[3]
Most species and genera are predators, though Rhombognathinae are instead algivores.[3] In freshwater halacarids, some species are restricted to crayfish gill chambers, implying a parasitic lifestyle, while Lobohalacarus weberi is a scavenger that feeds on dead nematodes and oligochaetes but not on live ones.[7]
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Phylogeny
Recent analyses place Halacaridae as the sister group to Parasitengona.[8][9] Within the group, algivorous Rhombognathinae consists of two lineages (Rhombognathus+Isobactrus and Rhombognathides+Metarhombognathus), meaning the habit of algivory has evolved two independent times.[3]
Genera
- Acanthohalacarus Bartsch, 2001
- Acanthopalpus Makarova, 1978
- Acarochelopodia Angelier, 1954
- Acaromantis Trouessart & Neumann, 1893
- Acarothrix Bartsch, 1990
- Actacarus Schulz, 1937
- Agaue Lohmann, 1889
- Agauides Bartsch, 1988
- Agauopsis Viets, 1927
- Anomalohalacarus Newell, 1949
- Arhodeoporus Newell, 1947
- Astacopsiphagus Viets, 1931
- Bathyhalacarus Sokolov & Jankovskaja, 1968
- Bradyagaue Newell, 1971
- Camactognathus Newell, 1984
- Coloboceras Trouessart, 1889
- Colobocerasides Viets, 1950
- Copidognathides Bartsch, 1976
- Copidognathus Trouessart, 1888
- Corallihalacarus Otto, 1999
- Enterohalacarus Viets, 1938
- Halacarellus Viets, 1927
- Halacaroides Bartsch, 1981
- Halacaropsis Bartsch, 1996
- Halacarus Gosse, 1855
- Halixodes Brucker & Trouessart, 1899
- Hamohalacarus Walter, 1931
- Himejacarus Imamura, 1957
- Isobactrus Newell, 1947
- Limnohalacarus Walter, 1917
- Lobohalacarus Viets, 1939
- Lohmannella Trouessart, 1901
- Metarhombognathus
- Mictognathus Newell, 1984
- Parasoldanellonyx Viets, 1929
- Parhalixodes Laubier, 1960
- Pelacarus Bartsch, 1986
- Peregrinacarus Bartsch, 1999
- Plegadognathus Morselli, 1981
- Porohalacarus Thor, 1922
- Porolohmannella Viets, 1933
- Rhombognathides Viets, 1927
- Rhombognathus Trouessart, 1888
- Ropohalacarus Bartsch, 1989
- Scaptognathides Monniot, 1972
- Scaptognathus Trouessart, 1889
- Simognathus Trouessart, 1889
- Soldanellonyx Walter, 1917
- Spongihalacarus Otto, 2000
- Stygohalacarus Viets, 1934
- Thalassacarus Newell, 1949
- Thalassarachna Packard, 1871
- Thalassophthirius Bartsch, 1988
- Troglohalacarus Viets, 1937
- Tropihalacarus Otto & Bartsch, 1999
- Werthella Lohmann, 1907
- Werthelloides Bartsch, 1986
- Winlundia Newell, 1984
- Xenohalacarus Otto, 2000
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References
Further reading
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