Subterranean Fishes of the World

5547

2018

The Neotropical South American catfish Cetopsidae is a family of Siluriformes that includes five genera and 43valid species distributed over a large portion of northern and central regions of South America, on both sides of the Andean cordilleras. The monophyly of the family is supported by several previous studies, based on both morphological and molecular characters. Despite the scarcity of evolutionary studies on the nervous system of neotropical catfishes, that complex shows great variation potentially informative for phylogenetic inference. In order to test the significance of neurological traits in a phylogenetic framework, the gross morphology of brain subdivisions in the catfish family Cetopsidae is described, illustrated and interpreted. In addition, comparative analyzes of the development of this complex were carried out in Helogenes marmoratus and Cetopsis gobioidesin order to establish homologies and ontogenetic transformations. Characters were delimited and tested separately in phylogenetic analyzes and later combined with other morphological and molecular characters with different methods of analysis. The volume of major brain subdivision was calculated by an ellipsoid model. A comprehensive comparison based on shape, relative position, and volume of the main brain subdivisions is presented for representative species of all genera and most available species in the family. The same comparisons were also made throughout the development of Helogenes marmoratus and Cetopsis gobioides. Comparisons with other phylogenetically related siluriform families provide a broader context for the understanding of the main evolutionary transformations which shaped the cetopsid brain. Phylogenetic analyzes of all morphological characters were first conducted separately, and later in matrices concatenated under the Parsimony criterion. Bayesian analyzes of three aligned and concatenated mitochondrial gene sequences (COI, 16S and Cytb) were implemented. Analyzes of all the data combined were conducted under both Parsimony and Bayesian criteria. Profoundly distinct morphological patterns are identified for each of the two main cetopsid subdivisions, subfamilies Helogeninae and Cetopsinae. Little intraspecific variation on major subdivisions of the brain exists in species examined herein. The modifications observed throughout the development of the brain inHelogenes marmoratus and Cetopsis gobioides were used for the correct delimitation xiv of characters and their states. The monophyly of all genera is supported by putative neuroanatomic characters. Phylogenetic mapping reveals recurrent morphological patterns suggestive of an association with specific feeding specializations and other life-history traits. Morphological and molecular characters were highly congruent in phylogenetic hypotheses, with inconsistencies restricted to the tribe Cetopsini. All analyzes recovered Helogeninae as thesister group toall remaining cetopsids, followed by Cetopsidiini, Denticetopsini and Cetopsini as successive sister groups. Results of the present study support the idea that large and concatenated analyzes of morphological and molecular characters result in robust well-supported hypotheses of relationships. Neuroanatomical characters are highly informative for phylogenetic inferenceand area promising field to be explored in understanding the evolution of Otophysi.

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