Brazilian ichthyologists have described four new species of miniature plecs in the genus Hisonotus from southeastern South America.
Publishing the descriptions of Hisonotus iota, H. leucophrys, H. megaloplax and H. montanus in a recent issue of the journal Zootaxa, Tiago Carvalho and Roberto Reis also review the Hisonotus species found in the Uruguay River drainage (from where all the new species were found).
Hisonotus iota
Hisonotus iota is distinguished from congeners except H. hungy in having fewer lateral plates and vertebrae.
It differs from Hisonotus hungy by the morphology of the laterosensory canals below the eye.
This species was collected from amongst submerged vegetation in a clear, fast-flowing stream with a rocky bottom.
Hisonotus iota is named after its small size (Greek iota=something very small).
Hisonotus leucophrys
Hisonotus leucophrys is distinguished from congeners except H. montanus in having broader pale stripes on the top and the sides of the head.
It differs from H. montanus in having the snout completely covered by odontodes and the morphology of the laterosensory canals below the eye.
According to the authors, This species inhabits median to fast flowing watercourses of clear water, with stones and sand on the bottom, and are found in aquatic, partially submersed, vegetation islands composed by grass.
Hisonotus leucophrys is named after the pale stripes on the head above the eye (Greek leucos=white and ophrys=eyebrow).
Hisonotus megaloplax
Hisonotus megaloplax is distinguished from congeners by the arrangement of the abdominal plates.
This species is found in marginal submerged vegetation of grass in a slow- to moderate-flowing stream with clear to brown water over a substrate of stones, sand and leaf litter.
Hisonotus megaloplax is named after its large lateral abdominal plate series (Greek megalos=big and plax=plate).
Hisonotus montanus
Hisonotus montanus is distinguished from congeners except for H. aky and H. iota by the morphology of the laterosensory canals below the eye.
It differs from H. aky and H. iota in having broader pale bands and the presence of white patches on top of the head.
This species inhabits higher elevations (850 m above sea level), being associated with marginal vegetation in moderately-flowing streams with clear water and a bottom of sand and rock.
Hisonotus montanus is named after the high altitude where it occurs (Latin montanus=of mountains).
Epactionotus aky
The authors also recognize two additional species of Hisonotus in the Uruguay River drainage in their review: H. aky (this distinctively bright green miniature plec was previously placed in the genus Epactionotus) and H. ringueleti (with H. candombe as a junior synonym).
For more information, see the paper: Carvalho, TP and RE Reis (2009) Four new species of Hisonotus (Siluriformes: Loricariidae) from the upper rio Uruguay, southeastern South America, with a review of the genus in the rio Uruguay basin. Zootaxa 2113, pp. 1"40.