Meeting Abstract
50.1 Jan. 6 Morphology and mechanism of the opercular spine locking apparatus in haematophagous candiru catfish ADRIAENS, D*; BEKAERT, K; Ghent University, Belgium; Ghent University, Belgium Dominique.Adriaens@ugent.be
During early evolution of actinopterygian fishes, mouth opening enabled by the hyoid system became assisted by the opercular linkage system, coupling opercular rotation to lower jaw depression. This coupling remained quite stable during teleostean evolution, with some variation on what is linked to what. However, in some special cases, a decoupling of the opercular system from the lower jaw occurred, thereby creating the possibility for a novel function to arise. This evolved at least two times independently in the Neotropical loricarioid catfishes, i.e. within the Trichomycteridae and the Scoloplacidae-Astroblepidae-Loricariidae clade. This presentation focuses on the opercular apparatus in the trichomycterid clade, especially with the structural innovations that arose within the haematophagous candiru lineage of Vandelliinae. These so-called parasitic catfishes are known to use an erectile apparatus with spines to anchor themselves in gill cavities of large fishes (or other unfavourable cavities). These spines, born by the opercular and interopercular bone, however, are not to be considered an adaptation to their specialised feeding behaviour as they are present in all trichomycterids. However, structural innovations of a basal trichomycterids condition did occur of which it is hypothesised that they assist the opercular system for locking their spines in gill cavities during feeding. A detailed morphological study, relying on graphical 3D-reconstructions, allowed recognising several innovations in Vandellia, which are not present in Trichomycterus (basal trichomycterid). Modelling of the graphical reconstructions, and taking into account the observed structural couplings and articulations, was done to hypothesis the movements of the components involved during spine erection.
