New tetra described in Roeboides revision

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A new species of scale-eating tetra has been described from northeastern Brazil.

The paper by Carlos de Lucena and published in the latest issue of the journal Iheringia, Srie Zoologia, describes the new species as part of a taxonomic revision of the members of the Roeboides affinis species complex.

The genus Roeboides consists of small- to medium-sized translucent South American tetras known for their lepidophagous (scale-eating) habits, with the members of the R. affinis species complex recognised externally by an average of 69"83 lateral line scales and the presence of transverse bands of vermiculations on the scales.

The revision recognizes seven species within the complex: R. affinis, R. biserialis, R. descalvadensis, R. numerosus, R. oligistos, R. sazimai and R. xenodon, with R. sazimai being described as the new species.

Roeboides affinisThis species differs from other members of the genus in having 69"87 lateral line scales, 15"23 scale rows above and 12"19 scale rows below the lateral line, a single row of teeth on the dentary, 8"11 gill rakers on the lower branch of the first gill arch, and 42"54 branched anal-fin rays.

Roeboides affinis is known from the Amazon, Orinoco, Paran-Paraguay and Tocantins-Araguaia river drainages, and the rivers of Guyana and Suriname.

Roeboides biserialisThis species, known from the Amazon River drainage, differs from other members of the genus in having 58"64 lateral line scales and two rows of teeth in the dentary.

Roeboides descalvadensisThis species is known from the Amazon and Paran-Paraguay river drainages. It differs from other members of the genus in having 60"71 lateral line scales, 12"16 scale rows above the lateral line, a single row of teeth on the dentary, 10"11 gill rakers on the lower branch of the first gill arch, 42"52 branched anal-fin rays, a convex snout profile, and the presence of humeral and caudal spots.

Roeboides numerosusThis species differs from other members of the genus in having 12"14 gill rakers on the lower branch of the first gill arch. It is known from the Orinoco River drainage.

Roeboides oligistosThis species is restricted to the Amazon River drainage. It differs from other members of the genus in having 63"72 lateral line scales, a single row of teeth on the dentary, 38"44 branched anal-fin rays and the absence of humeral and caudal spots.

Roeboides sazimaiThis new species, named after the Brazilian ichthyologist Ivan Sazima for his studies on the scale-eating habits of the genus and the Brazilian ichthyofauna in general, is known from the Parnaba and Pindar-Mearim river drainages in northeastern Brazil.

It differs from other members of the genus in having 64"70 lateral line scales, 10"11 gill rakers on the lower branch of the first gill arch, 42"48 branched anal-fin rays, a single row of teeth on the dentary, and a straight snout profile.

Roeboides xenodonThis species is restricted to the So Francisco River drainage. It differs from other members of the genus in having a small bony protrusion on the anteroventral region of the cleithrum, 7"8 gill rakers on the lower branch of the first gill arch, 69"87 lateral line scales, a single row of teeth on the dentary and a vertically elongate humeral spot.

For more information, see the paper: Lucena, CAS de (2007) Reviso taxonmica das espcies do gnero Roeboides grupo-affinis (Ostariophysi, Characiformes, Characidae) Iheriniga, Srie Zoologia 97, 117"136 .