Geophagus Heckel

Hernan López-Fernández & Donald C. Taphorn, 2004, Geophagus abalios, G. dicrozoster and G. winemilleri (Perciformes: Cichlidae), three new species from Venezuela., Zootaxa 439, pp. 1-27 : 23-24

[[ Geophagus Heckel ]]

Discussion

We describe three species of Geophagus from the “surinamensis complex” , elevating the described species in the genus to fourteen, and the known Venezuelan species to six. The new species Geophagus abalios , G. dicrozoster and G. winemilleri are diagnosable from species outside the G. surinamensis complex by the lack of a complete infraorbital stripe (Figs. 1, 2), which can be absent ( G. abalios ) or reduced to a preopercular mark ( G. dicrozoster , G. winemilleri ). The combination of coloration and squamation characters distinguishes the three species from each other, and from the other seven described species within the G. surinamensis complex (Fig. 2). Lateral bar patterns have been used as diagnostic characters in other genera of Neotropical cichlids, notably Mesonauta (Kullander & Silfvergrip 1991; Schindler 1998) and Apistogramma (e.g. Kullander 1980). It is clear from the present paper that some species of Geophagus present well-defined and stable patterns of lateral bars, and these can be used as diagnostic characters. Color photographs of aquarium specimens suggest that double-bar patterns and the lack of a preopercular mark, as observed in G. abalios n. sp., occur together in yet undescribed species (e.g. Weidner 2000, Geophagus sp. “Maicuru” , G. sp. “Porto Franco” , G. sp. “ Tapajos Orange Head” ). This apparent consistency may reflect underlying phylogenetic relationships within Geophagus , and may provide useful sets of characters for future phylogenetic analysis within the genus.

Although little is known of the ecology of Geophagus abalios and G. dicrozoster , it appears that they share many essential aspects of their biology. Field observations in the Río Cinaruco (south-western Venezuelan llanos) indicate that both species are mouthbrooders(HLF unpubl). Both species are among the most abundant in samples from lagoon, or to a lesser extent, channel habitats over bare sandy bottoms, although they can be abundant in structured habitats with submerged wood or rocks (Arrington, 2002). On at least one occasion, G. dicrozoster was captured in rapids near the headwaters of the Río Negro (K. Winemiller et al. unpubl.). Preliminary diet analyses indicate that, at least qualitatively, both species share a diet of benthic insect larvae dominated by chironomids (Diptera), trichopterans and ephemeropterans (HLF unpubl.). Given the great similarity of these species in overall morphology, color patterns, feeding modes, and probably reproductive behavior, it is remarkable that they seem to share the same habitats in an extensive manner. The ecology of G. winemilleri is almost entirely unknown: all of our available records and observations indicate that it inhabits black waters with sandy bottoms, and it probably is a “larvophilous” mouth brooder (Weidner 2000).

Geophagus abalios and G. dicrozoster are sympatric in most of their known distribution, and frequently are found in the same habitats, particularly in the Cinaruco river, southern Apure State (HLF unpubl.). Their syntopy will probably be shown to be more extensive once they are distinguished in collections, where they are commonly referred to as G. surinamensis or G. altifrons (e.g. Mago-Leccia 1970; Machado-Allison 1987; 1993; Royero et al. 1992). The broad distribution of both species in the Orinoco basin suggests they should be as common in Colombia as they are in the Venezuelan portion of the basin. It is not clear from our current distributional knowledge whether the range of G. abalios and G. dicrozoster extends further south than the headwaters of the Río Negro. The known distribution of G. winemilleri is restricted to the lower Casiquiare and the upper Río Negro, but the species may be present in the Río Ventuari drainage of the middle Orinoco basin (DCT and C. Montaña unpubl.). The fish diversity of the middle Orinoco and its tributaries is poorly known, and further collections are needed to clarify whether G. winemilleri is present in the upper Casiquiare and upper-middle Orinoco region. G. winemilleri is known to occur in the middle Río Negro (HLF pers. obs.). Weidner (2000) indicates that all aquarium imports come from the Río Negro and refers to a case in which the species was caught in the Archipelago das Anavilhanas, just north of Manaus. Further taxonomic, phylogenetic and distributional studies in the Río Negro will be necessary before a fruitful discussion of the biogeographic history of Geophagus in this region is possible.