Abstract
ABSTRACT Callichthyidae comprises the subfamilies Callichthyinae and Corydoradinae, both of which are morphologically distinct and monophyletic. Although there is consensus regarding the monophyly of the family, the relationships of about 80% of its species, currently included in the genus Corydoras, remain poorly known. Despite the vast amount of osteological information for Teleostei, knowledge regarding the phylogenetic implications of encephalon anatomy is sparse and represents a poorly explored source of potential characters. The present study aims to describe the encephalon morphology in members of the Callichthyidae in order to propose new characters that may help address phylogenetic questions regarding this group. In addition to representatives of Callichthyidae, specimens belonging to the Nematogenyidae, Trichomycteridae, Scoloplacidae, Astroblepidae and Loricariidae were dissected for comparative purposes. Head dissection revealed information on the structure of the medulla spinalis, rhombencephalon, mesencephalon, diencephalon and telencephalon. The conditions observed on the encephalons examined suggest that representatives of Callichthyidae have great taste perception and processing, while Corydoradinae stand out for visual acuity and Callichthyinae for mechanoreception processing subunits. Our results also indicate that the encephalon has important features for systematic studies of the family bringing greater resolution to current phylogenetic hypotheses.
Highlights
Species of Callichthyidae are recognized by the presence of a series of lateral bony plates along the body and a pair of barbels at the junction of the lips (Reis, 1998)
Investigations on the neuroanatomy of Siluriformes date to the end of the 19th century and probably the first attempt to understand the encephalon is the work of Herrick, Herrick (1891) on some species of Ictaluridae
The anterior margin of the lobus vagus is not continuous with lobus facialis in Callichthyidae and has an anterior angular expansion positioned above the posterior portion of lobus facialis in Corydoradinae (Fig. 1, arrow), and is adjacent rather than dorsal to this lobe in Callichthyinae (Fig. 2)
Summary
Species of Callichthyidae are recognized by the presence of a series of lateral bony plates along the body and a pair of barbels at the junction of the lips (Reis, 1998). They are grouped into eight genera (Ferraris, 2007) distributed throughout all major cis-Andean watersheds, as well as some trans-Andean drainages. Studies focused on phylogenetic relationships within Callichthyidae agree with its monophyly and the recognition of two main lineages among its representatives, i.e., Callichthyinae and Corydoradinae (Reis, 1998; Britto, 2003; Shimabukuro-Dias et al, 2004; Alexandrou et al, 2011) Knowledge about their encephalon morphology remains unknown.
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