Systematics of the Neotropical Fish Subfamily Glandulocaudinae (Teleostei: Characiformes: Characidae)
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Neotropical Ichthyology, 7(3):295-370, 2009 Copyright © 2009 Sociedade Brasileira de Ictiologia Systematics of the Neotropical fish subfamily Glandulocaudinae (Teleostei: Characiformes: Characidae) Naércio A. Menezes¹ and Stanley H. Weitzman² The systematics of the Glandulocaudinae is reviewed in detail and justification for the recognition of the group as a subfamily is discussed. The subfamily Glandulocaudinae consists of three genera: Lophiobrycon with one species plesiomorphic in some anatomical features but some others exclusively derived relative to the species in the other genera; Glandulocauda with two species intermediate in phylogenetic derivation; and Mimagoniates with seven species (one new), all more phylogenetically derived concerning their pheromone producing caudal-fin organs and with other anatomical characters presumably more derived than in the species of the other genera. Glandulocauda melanogenys Eigenmann, 1911, is considered a junior synonym of Hyphessobrycon melanopleurus Ellis, 1911. A replacement name, Glandulocauda caerulea Menezes & Weitzman, is proposed for G. melanopleura Eigenmann, 1911. Gland cells found in the caudal-fin organs of all species are histologically indistinguishable from club cells and probably secrete a pheromone during courtship. The club cells are associated with somewhat modified to highly derived caudal scales forming a pheromone pumping organ in the more derived genera and species. This subfamily is distributed in freshwaters of eastern and southern Brazil, Paraguay, and northeastern Uruguay. A sistemática de Glandulocaudinae é revista e a justificativa para o reconhecimento do grupo como subfamília discutida. A subfamília Glandulocaudinae consiste de três gêneros: Lophiobrycon, com uma espécie plesiomórfica com relação a alguns caracteres anatômicos, mas outros derivados e exclusivos em relação às espécies dos outros dois gêneros; Glandulocauda, com duas espécies intermediárias quanto à condição dos caracteres derivados; e Mimagoniates, com sete espécies (uma nova), todas filogeneticamente mais avançadas quanto às características dos órgãos da nadadeira caudal produtores de feromônio e outras características anatômicas presumivelmente mais derivadas do que nas espécies dos outros gêneros. Glandulocauda melanogenys Eigenmann, 1911, é considerado sinônimo junior de Hyphessobrycon melanopleurus Ellis, 1911. O nome Glandulocauda caerulea Menezes & Weitzman, é proposto em substiutição para G. melanopleura Eigenmann, 1911. Células glandulares encontradas nos órgãos da caudal são histologicamente indistinguíveis de “células club” e provavelmente secretam algum tipo de feromônio durante a corte. As “células club” são associadas a escamas da caudal pouco ou inteiramente modificadas e fazendo parte dos órgãos bombeadores de feromônio nas espécies e gêneros mais derivados. Esta subfamília distribui-se em ambientes de água doce do leste e sul do Brasil, no Paraguai e nordeste do Uruguai. Key words: South America, Lophiobrycon, Glandulocauda, Mimagoniates, Taxonomy, Biogeography. Introduction apparently adapted to narrowly restricted habitats, and limited in distribution by ecology. Some species may be threatened The species of the Glandulocaudinae are distributed in with extinction and one may already be extinct due to relatively parts of eastern and southern Brazil, Paraguay, and recent habitat alterations, primarily deforestation, by man. northeastern Uruguay. They are all attractively colored, We comment on these problems in the species accounts and relatively small fishes, usually about 28-60 mm in standard summarize them in a general section on conservation and length as adults. None qualify as miniatures as defined by ecology of the species of the subfamily. Weitzman & Vari (1988: 450), even though some species begin The subfamily Glandulocaudinae Eigenmann (1914) as maturation at the relatively small size of about 24 mm in recognized by Weitzman & Menezes (1998: 171) and Weitzman standard length. Some of the ten species of the subfamily are (2003: 222) was discussed by Weitzman et al. (2005: 332-333) 1Museu de Zoologia, Universidade de São Paulo, Caixa Postal 42494, 04218-970 São Paulo, SP, Brazil. [email protected] 2Smithsonian Institution, Division of Fishes, MRC 159, PO Box 37012 Washington DC, 20013-7102, USA. [email protected] 295 296 Systematics of the Neotropical fish subfamily Glandulocaudinae and split into two inseminating characid subfamilies, the Glandulocaudinae and Stevardiinae. Glandulocaudinae and Stevardiinae Gill (1858). The reasons Many previous authors dealing with systematics of the for Weitzman et al. (2005) decision were based on new Glandulocaudinae had to face many difficulties not only evidence for a somewhat different phylogenetic arrangement related to the poor preservation of type-specimens, but also related to the recognition of inseminating and non- to non-availability in collections of mature male specimens inseminating Clade A characids of Malabarba & Weitzman active at time of preservation. Thus few phylogenetically (2003). In part Weitzman et al. (2005) utilized the very different informative information is available. Here we provide comparative developmental and mature male caudal-fin organ phylogenetic data about the subfamily in an attempt to explain gross anatomies that separate the Glandulocaudinae and our nomenclatural decisions based on our hypothesis of the Stevardiinae as initially outlined in a discussion and key to phylogeny of these fishes. the species of the then recognized tribe Glandulocaudini The phylogeny presented here is mostly based on an (Menezes & Weitzman, 1990: 380-387). Weitzman et al. (2005: analysis of primary and especially secondary sexual characters 344) also noted that the glandular cells of the male caudal of the males and recent collections were necessary to address organs of these two subfamilies are entirely different. In the many of the phylogenetic issues. When utilizing primary and Glandulocaudinae they are histologically indistinguishable secondary sexual characters of glandulocaudine fishes for from club cells (alarm substance cells) whereas they and phylogenetic studies, it is absolutely necessary to examine consist of modified mucous cells in the Stevardiinae. From fully sexually active mature males because the males of the this it appears that the Glandulocaudinae and Stevardiinae more distally located species in the cladogram have their caudal may have evolved independently from inseminating Clade A organ and its accompanying osteological structures in a less characids that lack male caudal organs. Here we further outline complex state during earlier stages of maturation and sexual the differences in the derived caudal organs of these two maturity. These stages in these species are similar to those of Clade A characid subfamilies. Mirande (2009) based fully adult males of more basal species, a serious source of exclusively on the analysis of osteological characters confusion regarding identification and employment of these introduced all the members of clade A characids including the features for phylogenetic study. The only way to recognize Glandulocaudinae as subgroups of a large subfamily named that males of a given population sample have fully adult Stevardiinae. Since he did not use in his analysis insemination, secondary sexual characteristics is to examine males with fully histological structures of caudal organs and of gonads we active testes. Even then, it appears that some males acquire think the classification he proposed is not consistent with all active testes before the caudal organ reaches full development. the morphological evidences currently available for the characid groups involved and is not herein accepted. Material and Methods The subfamily Glandulocaudinae (= the Glandulocaudini of Menezes & Weitzman, 1990) consists of three genera, Counts and measurements follow Fink & Weitzman (1974: Lophiobrycon Castro et al. (2003: 13) with one species, 1-2) and Menezes & Weitzman (1990: 382-383). For counts Glandulocauda Eigenmann (1911b: 168) with two species, recorded in the descriptions, the range is given first followed and Mimagoniates Regan (1907: 402) with seven species. in parentheses by counts of the holotype, the mean, and total Lophiobrycon weitzmani Castro, Ribeiro, Benine & Melo number of specimens counted. Total vertebral counts include (2003) was assigned by its authors as a basal species related the four vertebrae of the Weberian apparatus complex. The to all others within the Glandulocaudini of the former terminal “half centrum” hypural bones and associated vertebral Glandulocaudinae. elements, usually designated as PU1+U1, but not necessarily The Glandulocaudinae of this study was diagnosed by consisting only of those elements were counted as one vertebral Weitzman & Menezes (1998: 183) as a tribe, Glandulocaudini. element. Vertebral counts were taken from radiographs and from All species of the Glandulocaudinae have various forms of a cleared alizarin red and alcian blue stained preparations. These male caudal-fin organ that apparently secretes one or more preparations are called “cleared and stained” in the text or pheromones during courtship. In the more basal species in abbreviated c&s in lists of specimens. Lophiobrycon and Glandulocauda this organ consists of All measurements other than standard length (SL) are beaded lines of glandular tissue consisting of club cells at expressed as percentage of SL except for subunits of the the surface of the skin arranged along