Two Astyanax tetras described from Bahia


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Brazilian scientists have described two new species of tetra of the genus Astyanax from northeastern Brazil.

The two species are named Astyanax epiagos and Astyanax jacobinae by Angela Zanata and Priscila Camelier in a recent issue of the journal Zootaxa.

Astyanax epiagos, from the Paraguau River drainage, differs from all Astyanax known to occur in northeastern Brazilian drainages by the reduced number of branched anal-fin rays (usually 14-16), and a combination of a vertically elongated humeral blotch, a conspicuous dark blotch over caudal peduncle, conspicuous midlateral dark stripe absent, body deepest around the vertical through the midlength of the pectoral-fin, scales over anal-fin base absent, and a broad naked space between the infraorbitals and preopercle.

Astyanax epiagos was collected exclusively in dark water streams, running over rocky bottom at elevate altitudes (899"934 m), in environment characterized by relatively small rocky pools (0.5 m deep and 1.5 m wide) connected by extremely shallow stretches of water or small rapids.

The species occurs above (but not below) the Cachoeira do Ferro Doido, a 98-metre high waterfall; the species is named after its unusual habitat (from the Greek epi, meaning above and agos, meaning rocky cleft).

An analysis of the gut contents revealed filamentous algae, fragments of vascular plants, adults and larvae of Diptera (Chironomidae), adults of Hemiptera and Coleoptera (Chrysomelidae), fragments of Hymenoptera and of other unidentified arthropods.

Astyanax jacobinae, from the Itapicuru River drainage, differs from all congeners in having a large eye, three maxillary teeth, a vertically elongated humeral blotch, both a conspicuous dark midlateral stripe and a conspicuous spot over caudal peduncle absent, and a broad naked space between the infraorbitals and preopercle absent. Astyanax jacobinae is named after its type locality (municpio de Jacobina, Bahia State, Brazil) and the type locality is a dark headwater stream with mild water current running over pebbles, rocks and sand.

Stream depth in the area sampled varied between 0.3"0.5 m and average width was around 2.0 m. Trees, palm trees, and grasses represented the marginal vegetation.

An analysis of gut contents revealed larvae of Diptera (Chironomidae), larvae of Trichoptera, fragments of adults of Diptera and unidentified fragments of arthropods.

For more information, see the paper: Zanata, AM and P Camelier (2008) Two new species of Astyanax (Characiformes: Characidae) from upper rio Paraguau and rio Itapicuru basins, Chapada Diamantina, Bahia, Brazil. Zootaxa 1908, pp. 28"40.