Meeting Abstract
51.8 Saturday, Jan. 5 Early development of Ancistrus cf. triradiatus and Corydoras aeneus: a case study for understanding the role of ontogenetic patterning in loricarioid evolution. HUYSENTRUYT, F.*; GEERINCKX, T.; ADRIAENS, D.; Ghent University, Gent, Belgium frank.huysentruyt@ugent.be
The Neotropical fauna is one of the most diverse and least known; understanding this diversity and the specific processes of speciation and radiation is one of the greatest challenges in modern biology. In this context, the Amazon-basin houses the over 2000 known teleosts, half of which belong to the Loricarioidea. In this superfamily, an evolutionary trend exists which has led to the presence of a suckermouth in the families Astroblepidae and Loricariidae. Additionally, in loricariids, this has led to the formation of a highly specialized feeding mechanism (i.e., for algae-scraping). Implications of this specialization involve tilted lower jaws and new muscle configurations, coupled to an increased jaw mobility. In this evolutionary lineage, this is established through decoupling of structures with subsequent functional shifts and neoformations of muscle bundles, mainly in the jaw and opercular apparatus. Callichthyidae have a basal position in this lineage, with a ventrally placed mouth already present but without a sucking disc or a algae-scraping feeding apparatus. In this context, the morphology and its ontogenetic transformations in both a highly specialized (A. cf. triradiatus) and basal (C. aeneus) representative were studied in detail, and compared. Results showed ontogenetic patterns in both species to be highly comparable at the level of formation sequence of anatomical structures. The relative timing of these structures, both in relation to other functional units as well as to important early life history events, however differed significantly. A possible basis for this could very well be a prolonged egg stage in A. cf. triradiatus, providing the necessary time for the decoupling and novel acquisition of key features in the evolution of algae scraping.
