Two new species and a review of the inseminating freshwater fish genus Monotocheirodon (Characiformes: Characidae) from Peru and Bolivia

Two new species of inseminating freshwater fishes of the genus Monotocheirodon, family Characidae, are described from Peru. Males and females of both new species have an external, visually obvious urogenital papilla that was not detected in the females in previous studies, with this longer in males, which use it as an inseminating organ. A third inseminating species from Bolivia, Monotocheirodon pearsoni, unstudied in any detail since its original description in 1924, is redescribed. This latter species lacks an inseminating organ. Monotocheirodon is redescribed, its phylogenetic relationships are briefly discussed and it is suggested that it is possibly related to the stevardiin genera Ceratobranchia, Othonocheirodus, and Odontostoechus.

Duas espécies novas de peixes inseminadores de água doce do Peru do gênero Monotocheirodon são descritas. Machos e fêmeas destas espécies têm uma papila urogenital bem visível externamente, não detectada nas fêmeas em estudos prévios, alongada e usada pelos machos como órgão inseminador. Uma terceira espécie inseminadora descrita da Bolívia, Monotocheirodon pearsoni, pouco estudada em detalhe desde sua descrição original em 1924, é redescrita. Esta última não possui órgão inseminador. O gênero Monotocheirodon é redescrito, suas relações filogenéticas com os demais gêneros incluídcos em Stevardiinae são brevemente discutidas, sugerindo-se que o mesmo possa estar relacionado com os gêneros Ceratobranchia, Otonocheirodus e Odontostoechus.

The authors thank Tamara Clark for preparing Figs. 1, 2, 5, 6, 9, 10, 12, 13 and 14 with support from the Herbert R. and Evelyn Axelrod Chair in Systematic Ichthyology in the Division of Fishes, NMNH, which also provided funds for a trip of NAM to NMNH. The Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) supported research work of NAM in MZUSP and NMNH through a research fellowship. Lisa Palmer (NMNH) prepared radiographs and provided general curatorial assistance. Luiz Malabarba and Richard Vari supplied valuable input regarding discussions of inseminating characid fishes. Richard Vari provided assistance and working space to the senior author during his visit to USNM to study material of Monotocheirodon, read the manuscript, added useful suggestions and helped to improve the English version. Hernán Ortega (MUSM) and Jeffrey Clayton (NMNH) greatly contributed to this study by providing museum catalog numbers, loan of specimens, locality information and specimen data. Eduardo G. Baena (MZUSP) completed some drawings and provided computer assistance. José Birindelli, André Luiz Netto-Ferreira and Manoela Maria F. Marinho (MZUSP) helped with computer programs. Two anonymous reviewers provided valuable comments on the manuscript. We are gratefully indebted to all.