title: First cytogenetic analysis ofIchthyoelephas humeralis(Günther, 1860) by conventional and molecular methods with comments on the karyotypic evolution in Prochilodontidae.
abstract: We used conventional cytogenetic techniques (Giemsa, C-banding, Ag-NOR), and fluorescentin situhybridization (FISH) with 5S and 18S rDNA probes to investigate the karyotype and cytogenetic characteristics ofIchthyoelephas humeralis(Günther, 1860) from Ecuador. The specimens studied have a karyotype with 2n=54 biarmed chromosomes (32 M + 22 SM) and C-positive heterochromatin located on the centromeric, pericentromeric, interstitial, and terminal regions of some chromosomes. The nucleolus organizer regions occurred terminally on the long arm of chromosome pair 2. FISH confirmed the presence of only one 18S rDNA cluster with nonsyntenic localization with the 5S rDNA. Cytogenetic data allow us to refute the earlier morphological hypothesis of a sister relationship betweenSemaprochilodusFowler, 1941 andIchthyoelephasPosada Arango, 1909 and support the molecular proposal thatIchthyoelephasis a sister group to the monophyletic clade containingProchilodusAgassiz, 1829 andSemaprochilodus.
authors.affiliation: Universidad Técnica de Machala, Facultad de Ciencias Agropecuarias, Av. Panamericana Km 51/2, Vía Machala Pasaje, El Oro, Ecuador; Universidad de Oriente, Escuela de Ciencias Aplicadas del Mar, Boca de Río, Península de Macanao, Estado Nueva Esparta, Venezuela.
authors.forename: Mauro Nirchio
authors.initials: MN
authors.lastname: Tursellino
authors.affiliation: Laboratório de Biologia e Genética de Peixes, Instituto de Biociências de Botucatu, Universidade Estadual Paulista (UNESP), Departamento de Morfologia, Distrito de Rubião Junior, Botucatu, São Paulo, Brazil. CEP: 18618-689.
authors.forename: Duílio Mazzoni Zerbinato de Andrade
authors.initials: DM
authors.lastname: Silva
authors.affiliation: Universidad Técnica de Machala, Facultad de Ciencias Agropecuarias, Av. Panamericana Km 51/2, Vía Machala Pasaje, El Oro, Ecuador.
authors.forename: César Quezada
authors.initials: CQ
authors.lastname: Abad
authors.affiliation: Universidad Técnica de Machala, Facultad de Ciencias Agropecuarias, Av. Panamericana Km 51/2, Vía Machala Pasaje, El Oro, Ecuador.
authors.forename: Wilmer Arnoldo Moreira
authors.initials: WA
authors.lastname: Blacio
authors.affiliation: Universidad Técnica de Machala, Facultad de Ciencias Agropecuarias, Av. Panamericana Km 51/2, Vía Machala Pasaje, El Oro, Ecuador.
authors.forename: Omar Rogerio Sánchez
authors.initials: OR
authors.lastname: Romero
authors.affiliation: Laboratório de Biologia e Genética de Peixes, Instituto de Biociências de Botucatu, Universidade Estadual Paulista (UNESP), Departamento de Morfologia, Distrito de Rubião Junior, Botucatu, São Paulo, Brazil. CEP: 18618-689.
authors.forename: Claudio
authors.initials: C
authors.lastname: Oliveira
keywords: Fluorescent in situ hybridization; Karyotype; NORs; Prochilodontidae; evolution