The Laterosensory Canal System in Epigean and Subterranean Ituglanis (Siluriformes: Trichomycteridae), With Comments About Troglomorphism and the Phylogeny of the Genus

Abstract

The laterosensory system is a mechanosensory modality involved in many aspects of fish biology and behavior. Laterosensory perception may be crucial for individual survival, especially in habitats where other sensory modalities are generally useless, such as the permanently aphotic subterranean environment. In the present study, we describe the laterosensory canal system of epigean and subterranean species of the genus Ituglanis (Siluriformes: Trichomycteridae). With seven independent colonizations of the subterranean environment in a limited geographical range coupled with a high diversity of epigean forms, the genus is an excellent model for the study of morphological specialization to hypogean life. The comparison between epigean and subterranean species reveals a trend toward reduction of the laterosensory canal system in the subterranean species, coupled with higher intraspecific variability and asymmetry. This trend is mirrored in other subterranean fishes and in species living in different confined spaces, like the interstitial environment. Therefore, we propose that the reduction of the laterosensory canal system should be regarded as a troglomorphic (= cave-related) character for subterranean fishes. We also comment about the patterns of the laterosensory canal system in trichomycterids and use the diversity of this system among species of Ituglanis to infer phylogenetic relationships within the genus. J. Morphol. 278:4-28, 2017. ©© 2016 Wiley Periodicals,Inc.

A new species of Ituglanis (Siluriformes: Trichomycteridae) from the rio Uruguai basin, southern Brazil

“…Recently, Rizzato, Bichuette (2016) conducted a complete analysis of the laterosensory canal system within Ituglanis and discussed the previous hypotheses of groupings inside the genus (i.e. de Pinna, Keith, 2003;Rizzato, Bichuette, 2014).…”

“…According to an updated list presented by Rizzato, Bichuette (2016), this group should include all species occurring in the drainages inside the Amazon forest plus two species from Paraná-Paraguai basin (I. eichhorniarum and I. herberti). Rizzato, Bichuette (2016) named the latter the "northwestern South America group", in contrast to the "southeastern group", which should comprise the remaining species of the genus.…”

“…According to an updated list presented by Rizzato, Bichuette (2016), this group should include all species occurring in the drainages inside the Amazon forest plus two species from Paraná-Paraguai basin (I. eichhorniarum and I. herberti). Rizzato, Bichuette (2016) named the latter the "northwestern South America group", in contrast to the "southeastern group", which should comprise the remaining species of the genus. Ituglanis inusitatus has less than three ribs and inhabits tributaries of the left bank of the rio Uruguai (southern Brazil), a drainage encompassed by the rio Paraná-Paraguai basin (Reis et al, 2016), thus contrasting with the biogeographical distribution of the groups proposed by de Pinna, Keith (2003) and Rizzato, Bichuette (2016).…”

“…Nomenclature of bones and cartilages follows Bockmann et al (2004). Nomenclature of laterosensory canal system and associated pores follows Rizzato, Bichuette (2016). Number of branchiostegal rays, odontodes, procurrent rays, basal radials, ribs, teeth, vertebrae and unsegmented rays were counted in one cleared and counter-stained specimen prepared according to the protocol of Taylor, Van Dyke (1985).…”

“…(1912); Miranda Ribeiro, P. (1940Ribeiro, P. ( , 1944Dahl (1960);de Pinna, Keith (2003); Datovo, Landim (2005); Wosiacki et al (2012); Datovo (2014) ;Castro, Wosiacki (2017) -with additional data provided by Canto (2009) andde Pinna (2013). Information about the number of pair of ribs in other species of Ituglanis was obtained from Rizzato, Bichuette (2016), plus Castro, Wosiacki (2017) for I. compactus. The numbering of undescribed species in the discussion and in the comparative material (Ituglanis sp.…”