Description of new putative multicomponent courtship signal for mate recognition in Rachoviscus crassiceps (Characiformes: Acestrorhamphidae)

Abstract Males of Rachoviscus crassiceps have two small longitudinal black marks on pectoral-fin rays associated to hard and thick tissues that develop in the dorsal surface of the first and second branched pectoral-fin rays, covered dorsally with pheromone secretion club cells. Besides that, the interradial membrane between the second and third and sometimes that between the third and fourth branched pectoral fin rays are thicker than between other contiguous rays, and covered ventrally with hypertrophied mucous cells. Courtship signaling is essential for mate recognition and is frequently multimodal. Courtship signals are apparently essential for mate recognition in inseminating characiform species of the families Characidae and Stevardiidae, that show more conspicuous or more developed courtship signals than in external fertilization species. We propose the pectoral fin organ in the inseminating acestrorhamphid R. crassiceps of the subfamily Thayeriinae constitutes a putative multicomponent courtship signal, including chemical (pheromones) and visual signals (black mark on pectoral fin).