Two New Species of Acestridium Haseman, 1911 (Loricariidae: Hypoptopomatinae) from the Rio Madeira Basin, Brazil

Acestridium gymnogaster and A. scutatum are described as new from small tributaries to the middle Rio Madeira, Amazonas, Brazil. Acestridium gymnogaster is most similar to A. discus from which it differs in the number of medial unpaired predorsal plates, the arrangement of chromatophores in predorsal area, and the absence of contact midventrally between the lateral abdominal plates. Acestridium scutatum is most similar to A. triplax from which it differs in having a longer snout and by the shape of the preanal plate. A key to the species of Acestridium is provided.

Acestridium gymnogaster e Acestridium scutatum, espécies novas, são descritas de pequenos rios tributários do médio Rio Madeira, Estado do Amazonas, Brasil. Acestridium gymnogaster é mais semelhante à A. discus, de quem difere pelo número de placas ímpares médias pré-dorsais, arranjo dos cromatóforos na área pré-dorsal, e a ausência de contato entre as placas laterais abdominais na linha media. Acestridium scutatum é mais semelhante à A. triplax, de quem difere por ter o focinho mais longo e pela forma da placa pré-anal. Uma chave para as espécies de Acestridium é apresentada.

Fig. 1

Acestridium gymnogaster, MCP 43199, holotype, 59.1 mm SL, female, Rio Traira, ca 35 km E of Rio Madeira on Trans-Amazonica road, 7°35′33″S, 62°44′45″W, Humaitá, Amazonas, Brazil.

Fig. 2

Distribution of Acestridium gymnogaster (dot) and A. scutatum (triangle). Symbols represent more than one locality.

Fig. 3

Acestridium scutatum, MCP 43198, holotype, 62.7 mm SL, female, Rio Traira, ca 35 km E of Rio Madeira on Trans-Amazonica road, 7°35′33″S, 62°44′45″W, Humaitá, Amazonas, Brazil.

Fig. 4

Preanal plate of species of Acestridium: (A) A. scutatum, MCP 43198; and (B) A. triplax, MPEG 12467. Scale bar: 1 mm.

Fig. 5

Predorsal region of species of Acestridium: (A) A. martini, MZUSP 74275; (B) A. scutatum, MCP 37785; and (C) A. gymnogaster, MCP 37784. CP = compound pterotic, NP = nuchal plate, PNP = prenuchal plates, PPP = paired predorsal plates, SOC = supraoccipital. Scale bar: 5 mm.

Fig. 6

Abdominal plates of species of Acestridium: (A) A. discus, MZUSP 85322; (B) A. gymnogaster, MCP 37784; and (C) A. scutatum, MCP 43198. CL = cleithrum, CO = coracoid, LAP = lateral abdominal plate, MAP = middle abdominal plate, PAP = preanal plate. Scale bar: 5 mm.

Fig. 7

Spatulate projection of snout of species of Acestridium: (A) A. triplax, MCP 41746; (B) A. discus, MZUSP 85322; and (C) A. martini, MZUSP 74275. RP = rostral plates, PRP = postrostral plate. Scale bar: 1 mm.

Contributor Notes

Associate Editor: C. J. Ferraris.

¹ Laboratório de Sistemática de Vertebrados, Pontifícia Universidade Católica do Rio Grande do Sul, P.O. Box 1429, 90619-900 Porto Alegre, RS, Brazil; E-mail: (RER) reis@pucrs.br; and (PLA) lehmanncatfish@gmail.com. Send reprint requests to RER.

Received: 26 Aug 2008

Accepted: 30 Jan 2009