''Amphizoa'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of aquatic

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 ...

s in the suborder Adephaga, placed in its own monogeneric

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

, Amphizoidae.''Amphizoa'' LeConte 1853.
Illinois Natural History Survey. There are five known species of ''Amphizoa'', three in western North America and two in the eastern Palearctic.Nilsson, Anders N., and Bernhard J. van Vondel (2005), World Catalogue of Insects. Volume 7: Amphizoidae, Aspidytidae, Haliplidae, Noteridae and Paelobiidae (Coleoptera, Adephaga) They are sometimes referred to by the common name troutstream beetles.

Description

Troutstream beetles have a characteristic appearance. They are relatively large, oval, slightly convex, dull black to piceus. Body length ranges between . The head is broad with a quadrate shape and small round eyes. The antenna is filiform, rather short with 11 segments. The pronotum is significantly narrower than the elytra and with lateral margins slightly crenulated; the prosternal processes are broad and flat, rounded to truncate at the apex; the

elytra An elytron (; ; , ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometimes alterna ...

are vaguely striate and have a series of short spines of unknown function.Kavanaugh, D. H. (1986) A systematic review of amphizoid beetles (Amphizoidae: Coleoptera) and their phylogenetic relationships to other Adephaga. ''Proceedings of the California Academy of Sciences'', vol. 44, no. 6 The legs are not well adapted for swimming, and lack long swimming setae. The hind coxae extend to the lateral margin of the abdomen and the

tarsal formula Tarsal formula is the number of segments of the tarsi, which has 3 numbers a-b-c, starting with the fore leg (a), then the middle leg (b), then the hind leg (c). For example, a tarsal formula of "5-5-4" as found in the Trictenotomidae means the ...

is 5-5-5.Dettner, K. 2005: 7.4. Amphizoidae LeConte, 1853. Pp. 81-85 in: Beutel, R.G.; Leschen, R.A.B. (volume eds.) Coleoptera, beetles. Volume 1: Morphology and systematics (Archostemata, Adephaga, Myxophaga, Polyphaga partim). In: Kristensen, N.P. & Beutel, R.G. (eds.) ''Handbook of Zoology. A Natural History of the Phyla of the Animal Kingdom. Volume IV. Arthropoda: Insecta. Part 38. Berlin, New York: Walter de Gruyter. Amphizoagenitalia

Known species of ''Amphizoa''

The genus ''Amphizoa'' contains the following known species: *'' Amphizoa davidis'' *''

Amphizoa insolens ''Amphizoa insolens'' is a species of aquatic beetles. It is found in North America from Alaska to southern California.Nilsson, Anders N., and Bernhard J. van Vondel (2005), World Catalogue of Insects. Volume 7: Amphizoidae, Aspidytidae, Halipli ...

'' *'' Amphizoa lecontei'' *'' Amphizoa sinica'' *'' Amphizoa striata''

Biology

Troutstream beetles can be found in streams and rivers in mountain regions of China, North Korea and western North America. Streams are often cold and medium to fast flowing, and the beetles can be found clinging to rocks, woody debris or at margins. Both adults and larvae are predators, especially on stonefly larvae but occasionally on other aquatic insects. Larvae may also scavenge dead insects.''ITIS: The Integrated Taxonomic Information System''. Orrell T. (custodian), 2011-04-26 When disturbed, adults exude a yellowish fluid from the anus, with an odor described as that of

cantaloupe The cantaloupe, rockmelon (Australia and New Zealand, although cantaloupe is used in some states of Australia), sweet melon, or spanspek (Southern Africa) is a melon that is a variety of the muskmelon species (''Cucumis melo'') from the fami ...

or decaying wood, probably as a defense mechanism against predators like

frog A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" ''Triadobatrachus'' is ...

s and

toad Toad is a common name for certain frogs, especially of the family Bufonidae, that are characterized by dry, leathery skin, short legs, and large bumps covering the parotoid glands. A distinction between frogs and toads is not made in scient ...

Phylogeny and evolution

Amphizoidae share some plesiomorphic features with

Carabidae Ground beetles are a large, cosmopolitan family of beetles, the Carabidae, with more than 40,000 species worldwide, around 2,000 of which are found in North America and 2,700 in Europe. As of 2015, it is one of the 10 most species-rich animal fami ...

, such as slender ambulatory legs, and other characteristics with

Dytiscidae The Dytiscidae – based on the Greek ''dytikos'' (δυτικός), "able to dive" – are the predaceous diving beetles, a family of water beetles. They occur in virtually any freshwater habitat around the world, but a few species live ...

, such as large sensorial lobes on the

epipharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its struct ...

. In an analysis based on the genes

18S rRNA 18S may refer to: *18S ribosomal RNA *18S rRNA (adenine1779-N6/adenine1780-N6)-dimethyltransferase *18SEH The Family II is a straight-4 piston engine that was originally developed by Opel in the 1970s, debuting in 1979. Available in a wide range ...

16S rRNA 16S rRNA may refer to: * 16S ribosomal RNA 16 S ribosomal RNA (or 16 S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome ( SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure. The g ...

and cytochrome oxidase I, Amphizoidae was placed as a sister group of a clade comprising the newly described family

Aspidytidae Aspidytidae is a family of aquatic beetles of the suborder Adephaga, described in 2002 from specimens in South Africa and China. There are only two known species in the family and these were originally described in the genus '' Aspidytes,''Beutel ...

, Paelobiidae(=Hygrobiidae) and Dysticidae.Ribera, I., Hogan, J. H. & Vogler, A. P. 2002. Phylogeny of Hydradephagan water beetles inferred from 18S rDNA sequences. ''Mol. Phyl. Evol''. 23, 43–62. An analysis based on a morphological character matrix also came to this conclusion.Beutel, R., Balke, M., and Steiner, W. E. 2006. The systematic position of Meruidae (Coleoptera, Adephaga) and the phylogeny of the smaller aquatic adephagan beetle families. ''Cladistics'' 22(2) 102–131. However, two other studies with more genes have placed Amphizoidae as sister group to Aspidytidae.Balke, M., et al. 2008. Systematic placement of the recently discovered beetle family Meruidae (Coleoptera: Dytiscoidea) based on molecular data. ''Zoologica Scripta'', 37, 647–650.Balke, M., Ribera, I. & Beutel, R. G. 2005. The systematic position of Aspidytidae, the diversification of Dytiscoidea (Coleoptera, Adephaga) and the phylogenetic signal of third codon positions. ''Journal of Zoological Systematics and Evolutionary Research'' 43 (3): 223-242 With Aspidytidae and Amphizoa share the same morphology of the apical part of the pro-sternal process and the mesocoxal cavities. The phylogeny within Amphizoa has been analysed in two studies based on morphological characters and they suggested that ''A. davidis'' is an isolated species and sister to the remaining four species as follows (''A davidis'', (''A. insolens'', (''A. striata'', (''A. sinica'' & ''A. lecontei'')))).Edwards, J. G. 1951. Amphizoidae (Coleoptera) of the World. ''The Wasmann Journal of Biology'' vol. 8, no. 3Peiyu, Y. & Stork, N. E. (1991) New evidence on the phylogeny and biogeography of the Amphizoidae: discovery of a new species from China (Coleoptera), ''Systematic Entomology'', vol. 16, no. 2

References

External links