Scientists have described a new species of translucent tetra from the central Amazon River drainage.
The new tetra is named Hemigrammus geisleri by Axel Zarske and Jacques Gry in a paper published in the most recent issue of the journal Vertebrate Zoology.
Hemigrammus geisleri is named after Rolf Geisler, who first collected this species, and can be distinguished from other members of the genus in having the following set of characters: two to four tri- to quincuspid teeth in the external row of the premaxilla, five (rarely six) quincuspid teeth in the internal row of the premaxilla, one to two (rarely three) maxillary teeth, 16"18 (mostly 17) branched anal-fin rays, 29"31 longitudinal scales, 8"14 pored scales in the lateral line, 4/1/3"3.5 transverse scales predorsally, 32"33 vertebrae and a dark oval spot at the base of the caudal fin.
Hemigrammus geisleri closely resembles H. mimus, a sympatric species which is hypothesized to be the most closely related to it (and which is also redescribed in this paper).
However, the two species differs in the number and shape of the premaxillary and maxillary teeth, and in numbers of branched anal-fin rays and longitudinal scales.
It is also externally similar to Hyphessobrycon scutulatus, another recently-described tetra species, but differs in the number and shape of the premaxillary and maxillary teeth, and in numbers of branched anal-fin rays, scales and vertebrae.
The localities where the type series were collected were streams with clear brown water, water temperatures of about 25 degrees C and pH of about 5.0.
Other species of fish collected with the new tetra include Bryconops sp., Carnegiella strigata, Crenuchus spilurus, Hyphessobrycon bentosi, Corydoras sp., loricariid catfishes, Apistogramma sp., and Hypselacara cf. coryphaenoides.
For more inofrmation, see the paper: Zarske, A and Gry, J (2007) Hemigrammus geisleri sp. n. " ein neueur Glasssalmler aus dem zentralen Amazonasgebiet, mit einer ergnzenden Beschreibung von Hemigrammus mimus Bhlke, 1955 (Teleostei: Characiformes: Characidae . Vertebrate Zoology 57, 5"14.