Diplomystidae, the velvet catfishes, are a family of

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catfishes endemic to freshwater habitats in Argentina and Chile in southern South America. It currently contains six species in two genera.

Taxonomy

In traditional schemes, the family Diplomystidae is the

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, primitive

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

to all other catfishes (Siluroidei). This is well supported by morphological evidence. Almost all molecular estimates of catfish phylogeny, by contrast, find Diplomystidae sister to Siluroidei, with Loricarioidei (the armoured catfish and relatives) the most basal group; though this may be an artifact of rapid evolution in loricarioids. Diplomystids retain more

plesiomorphic In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, and ...

characteristics than any other siluriforms, recent or fossil, including aspects of the maxillary bones, barbels, nares,

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, anterior pterygoid bones, Weberian complex centra, caudal skeleton, and fin rays, and pectoral girdle. Monophyly for Diplomystidae is well supported by

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

of the vomerine and palatine shapes, cranial articulation of the hyomandibula, and heavily papillose skin. ''Olivaichthys'' is a genus erected by Gloria Arratia in 1987. However, many recent authors synonymize this genus with ''Diplomystes''. A molecular analysis has proposed that the trans- Andean ''Diplomystes'' and the cis-Andean ''Olivaichthys'' are so closely related (in addition to the close morphological similarity), that ''Olivaichthys'' should not be recognized. However, this is strange, as recent divergence is unlikely with the species on either side of the Andes.

Description

Diplomystids are the only

extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...

catfish family with teeth on a well-developed maxilla (although this is also true of the extinct genus '' Hypsidoris''). Diplomystids possess maxillary barbels. The dorsal and pectoral fins have

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s. The largest species reaches .

Ecology

Relatively little is known of the habits and life history of diplomystids. In Chile, diplomystids are mostly found to be

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

in fast-moving streams, and ''D. camposensis'' also occurs in lakes. ''O. viedmensis'' has been taken from rivers near sea level to about 1,900 m. Diplomystids are generalized carnivores that consume

annelid The annelids (Annelida , from Latin ', "little ring"), also known as the segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecol ...

s, mollusks, and arthropods. Specimens of ''D. nahuelbutaensis'' from fast-flowing, moderate-elevation (370–520 m) tributaries of the Bío Bío River had eaten aquatic insect larvae, especially chironomids, and the relatively large decapod crustacean '' Aegla''. Reproduction occurs at least during the austral summer based on captures of females with maturing eggs, and the juveniles reported here were collected in December.

Conservation

All diplomystids are considered to be potentially or actually threatened or endangered due to habitat deterioration and predation or competition by introduced trout, '' Oncorhynchus mykiss'' and '' Salmo trutta''. ''D. chilensis'' may be extinct.

References

* {{Taxonbar, from=Q1572186 Catfish families Taxa named by Carl H. Eigenmann