''Georissus'', also called minute mud-loving beetles, is the only genus in the
beetle
Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...
family Georissidae (or Georyssidae). They are tiny insects living in wet soil, often near water. They are found on every continent except Antarctica.
Characteristics
Georissidae are small beetles (length 1–2 mm). They have a broadly oval body whose outline is more or less interrupted between the
pronotum
The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum ( dorsal), the prosternum (ventral), and the propleuron (lateral) on e ...
and the
elytra. The head and pronotum are granulate, the
prosternum
The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum ( dorsal), the prosternum (ventral), and the propleuron (lateral) on e ...
is rudimentary, without intercoxal processes. The anterior
coxae and
trochanters are fused. The basal ventrite is very large.
Ecology
Species are generally found within mud and sand at the periphery of rivers and streams, but also occur in tropical rainforest
leaf litter
Plant litter (also leaf litter, tree litter, soil litter, litterfall or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that have fallen to the ground. This detritus or dead organic material and its constituent ...
. Species of ''Georissus'' are predators on invertebrates, and under laboratory conditions sometimes engage in
cannibalism
Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, b ...
. Species within the genus are known for their habit of
psammophory
Psammophory is a method by which certain plants armor themselves with sand on their body parts making chances less for them to be eaten by animals. Over 200 species of plants hailing from 88 genera in 34 families have been identified as psammorpho ...
(actively covering their elytra with sand or mud) which helps protect them against predators.
Systematics and evolution
There are about 75 living species, including:
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Georissus australis''
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Georissus babai''
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Georissus bipartitus''
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Georissus caelatus''
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Georissus californicus''
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Georissus canalifer''
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Georissus capitatus''
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Georissus coelosternus''
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Georissus costatus''
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Georissus crenulatus''
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Georissus formosanus''
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Georissus fusicornis''
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Georissus granulosus''
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Georissus instabilis''
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Georissus japonicus''
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Georissus kingii''
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Georissus kurosawai''
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Georissus laesicollis''
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Georissus minusculus''
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Georissus occidentalis''
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Georissus pusillus''
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Georissus sakaii''
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Georissus septemcostatus''
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Georissus substriatus''
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Georissus trifossulatus''
The genus is divided into three subgenera (''Georissus'', ''Neogeorissus'' and ''Nipponogeorissus''). Formerly it was included within the family
Hydrophilidae. Recent
molecular
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bio ...
data indicate, that they belong to a clade comprising the small groups of
Hydrophiloidea -
Epimetopidae
Epimetopidae is a family of semi-aquatic beetles belonging to the Hydrophiloidea. They are found in sand and gravel at the edges of streams, rivers and shallow freshwater ponds. These beetles are shorter than half a centimeter long and have a pr ...
,
Hydrochidae,
Helophoridae and Georissidae.
[D.Bernhard et al., From terrestrial to aquatic habitats and back again — molecular insights into the evolution and phylogeny of Hydrophiloidea (Coleoptera) using multigene analyses. Zoologica Scripta 35 (6), 597–606, 2006]
References
Hydrophiloidea
Staphyliniformia genera
Taxa named by Pierre André Latreille
{{Hydrophiloidea-stub