Diplomystes is a genus of the family Diplomystidae (velvet catfishes), a primitive family of catfishes (order Siluriformes). Diplomystes is particularly interesting as a basal group of catfishes.
In traditional schemes, Diplomystidae is the basal, primitive sister group to all other catfishes (Siluroidei). This is well supported by morphological evidence. However, it has been hypothesized that a clade called Loricarioidei is the most basal group of catfishes, which is sister to a clade including Diplomystidae and the rest of the catfishes; however, the traditional hypothesis could not be rejected.
Diplomystids retain more plesiomorphic characteristics than any other siluriforms, recent or fossil, including aspects of the maxillary bone, barbels, nares, otic capsule, anterior pterygoid bones, Weberian complex centra, caudal skeleton and fin rays, and pectoral girdle. Monophyly for Diplomystes is well supported by synapomorphies of the vomerine and palatine shapes, cranial articulation of the hyomandibula, and heavily papillose skin.
Olivaichthys is a genus erected by Arratia in 1987. However, many recent authors synonymize this genus with Diplomystes. A molecular analysis has proposed the that 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.
Half of the species occur west of the Andes in south central Chile. The trans-Andean species are D. chilensis from rivers near Valparaíso and Santiago, D. nahuelbutaensis from the Bío Bío basin, and D. camposensis from the Valdivia region. Three other species occur east of the Andes in southern Argentina. The cis-Andean species are D. viedmensis from the Río Negro system, D. cuyanus from the Río Colorado and the Desaguadero-Salado basin, and D. mesembrinus known only from relatively few specimens from Chubut and Senguerr Rivers.
Diplomystes species are the only extant catfish family with teeth on a well-developed maxilla (although this is also true of the extinct genus Hypsidoris). Diplomystes possess maxillary barbels. The dorsal and pectoral fins have spines. The largest species reaches 32 centimetres (13 in).
Relatively little is known of the habits and life history of Diplomystes species. In Chile, Diplomystes are mostly found to be benthic in fast moving streams, and D. camposensis also occurs in lakes. D. viedmensis has been taken from rivers near sea level to about 1,900 metres.
Diplomystids are generalized carnivores that consume annelids, mollusks, and arthropods. Specimens of D. nahuelbutaensis from fast flowing moderate elevation (370–520 m) tributaries of the Río Bío Bío 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.
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.
1. ^ a b c Nelson, Joseph S. (2006). Fishes of the World. John Wiley & Sons, Inc. ISBN 0-471-25031-7.
Source: Wikipedia, Wikispecies: All text is available under the terms of the GNU Free Documentation License