A checklist of halacarid and pontarachnid mites ( Acari : Halacaridae and Pontarachnidae ) associated with mangroves

This paper is a compilation of the records for halacarid and pontarachnid mite species associated with mangroves. A total of 23 halacarid species (Acari: Halacaridae) belonging to the five genera Acarothrix, Agauopsis, Copidognathus, Isobactrus and Rhombognathus and six pontarachnid species (Acari: Pontarachnidae) belonging to the genus Litarachna are associated with various microhabitats of mangroves. Mites are found mainly in the algae and sediment covering pneumatophores and aerial roots.

In the present paper, a checklist of halacarid and pontarachnid mites associated with mangroves is presented.

Discussion
Halacarid mites live in a variety of substrata including within tufts of algae, on large fronds, in and on colonies of sponges, hydrozoans, bryozoans, barnacles, mussels and polychaetes, in interstices of coarse sediment or flocculent ooze, and in intertidal sand and turf growing on mangrove pneumatophores.Halacarids are also known to dwell on the rough and hairy body surfaces of crustaceans and gastropods, adjacent to gill chambers of crustaceans and mollusks and between the spines and in the gut of echinoderms.More than 1000 species of halacarids are currently recognized of which only 23 species have thus far been found to be associated with mangroves.Among the diverse mangrove microhabitats of mangroves (turf growing on pneumatophores, turf growing on small lower branches touching the sediment or water level, mud flats, litter falls), halacarids are mostly found on turf growing on mangrove aerial roots and pneumatophores and on turf growing on the small lower branches which touch the sediment or the water surface.
While individual halacarid species have been recorded only from mangrove habitats, no halacarid genera have thus far been found to be exclusively associated with mangroves (although majority of Acarothrix seems to occur mainly here).Extensive sampling in other habitats may prove that some apparent mangrove specialists may be found elsewhere, as well.
The Pontarachnidae Koenike, 1910 is the only family of water mites (Hydrachnidia) that is adapted to marine waters.Pontarachnids have been reported from both tropical and temperate littoral habitats.Most species live in the marine littoral zone; a few species have been described from freshwater, but these species have been found to occur only in estuaries or in locations near the sea (Smit 2009).The family is represented by two genera, Pontarachna Philippi, 1840 and Litarachna Walter, 1925 and 45 described species.Six species of Litarachna are known to be associated with mangroves, while none of the 24 known species of Pontarachna have been found in mangrove habitats.
Our current knowledge of the diversity of mangrove-associated halacarid and pontarachnid mites is far from complete.Future investigations of the mangrove milieu are expected to reveal many more species.