| Thalassina | |
|---|---|
 | |
| Thalassina anomala | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Malacostraca |
| Order: | Decapoda |
| Suborder: | Pleocyemata |
| (unranked): | Reptantia |
| Infraorder: | Gebiidea |
| Family: | Thalassinidae Latreille, 1831 |
| Genus: | Thalassina Latreille, 1806 |
| Type species | |
| Thalassina scorpionides Latreille, 1806 | |
| Species | |
11 extant, 1 fossil species (seetext) | |
Thalassina is agenus ofmud lobsters found in themangrove swamps of theIndian Ocean and westernPacific Ocean. Its nocturnal burrowing is important for therecycling of nutrients in the mangrove ecosystem, although it is sometimes considered a pest offish andprawn farms.
Thalassina is alobster-like animal which grows up to 30 centimetres (12 in) long,[1] but is more typically 6–20 cm (2.4–7.9 in) long. Its colour ranges from pale to dark brown and brownish green.[2] Thecarapace is tall and ovoid, extends over less than one third of the animal's length, and projects forward into a shortrostrum.[3] The tail is long and thin, and, like many burrowing decapods, theuropods are reduced in form, and do not form a functionaltail fan with thetelson.[4] Various rows ofsetae on thelegs andgills are used to prevent sediment from reaching the gills and for expelling any which does reach them.Thalassina also makes use of "respiratory reversal" to keep the gills free of dirt.[5]
Thalassina is found along the coast of theAsian mainland fromKerala,India toVietnam, includingSri Lanka and theAndaman and Nicobar Islands. It is also found throughout most ofMaritime Southeast Asia and theRyukyu Islands, and its range extends south to most ofAustralia's north coast (from theNorth West Cape inWestern Australia toCentral Queensland), and east toFiji andSamoa.[3]
Thalassina lives inburrows up to 2 m (6.6 ft) deep, and isactive at night.[6] Its burrowing fulfils an important rôle in the mangroveecosystem bringingorganic matter up from deep sediments. The animal's output forms largevolcano-like mounds which can reach heights of 3 m (10 ft) and are vital to many other species such asOdontomachus malignus (anant),Episesarma singaporense (acrab),Wolffogebia phuketensis (anothermud shrimp),Idioctis littoralis (aspider),Acrochordus granulatus (asnake),Excoecaria agallocha (amangrove) andtermites. The burrowing activity can causeT. anomala to be seen as a pest where it weakened thebunding that surroundsprawn farms orfish farms.[1] Thesmall-eyed goby, a species of herbivorousgoby specialising in feeding on seagrass, shares the burrows of mud lobsters of the genusThalassina.[7]
In parts of its range, includingIndonesia,Philippines,New Guinea andFiji, theclaws ofThalassina are eaten, but the meat is bland and it is never very popular. Inpowdered form orsteeped inalcohol, it is used inThailand as a remedy forasthma.[3]
Fossils ofThalassina are encountered "in countless numbers",[8] and extend back as far as theMiocene. They are generally preserved in a hardphosphatic nodule which is believed to be the animal'smoulting position.Storms may trap the animals in their burrows, and themineral-rich nature of thesediments leads to very rapid fossilisation.[9] The presence ofThalassina, together with other warm-water species in the Miocene ofJapan (outside the current range of the species) is taken as confirmation of a period of increased temperatures16 million years ago.[10]
Thalassina is the only genus in the familyThalassinidae (=ScorpionoidaeHaworth, 1825).[11][3] For many years, only a single species,Thalassina anomala, was recognised, but a 2009 revision by Nguyen Ngoc-Ho andMichèle de Saint Laurent increased the number of extant species to eight, including one fossil species.[12] Thalassinidae is classified in the infraorderGebiidea, alongside the familiesUpogebiidae,Axianassidae andLaomediidae.[13][14]
The extant species are:[13]
The fossil species,Thalassina emerii, is known from northern Australia, Papua New Guinea and Indonesia.[12]
Subgroups of orderDecapoda | |||||||||||||||||||||||||
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| Dendrobranchiata | 
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| Pleocyemata |
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