< . 137 



remarks that they or associates had observed spawning in Ageneiosus sp. and 

 Auchenipterichthys, respectively, but neither author gave details about the 

 behavioral events following spawning. ., ' : ',,..•; -Ti .:'. 



Unfortunately, as evident from a paucity of detailed information available in 

 the above studies, our knowledge of the reproductive biology of these fishes is 

 extremely limited. At present, gross morphological descriptions of sexually 

 dimorphic structures are the only available criteria for systematic comparisons. In 

 spite of the lack of information about these structures in many taxa, however, they 

 appear to have considerable potential for future analysis. In addition, studies of the 

 ecology and behavior of these fishes will undoubtedly have implications in future 

 taxonomic studies. 



External S exual Dimorphism of the Ageneiosid^ p. 



External dimorphism in ageneiosids involves seasonal modifications in males 

 of the maxillary barbels, the nuchal region, the dorsal fin, the anal fin, and possibly 

 pigmentary differences. The morphological details of these differences are 

 presented in the anatomical descriptions given above, and are only briefly reviewed 

 here. 



. During the height of the breeding period, the maxillary barbels of males 

 become stiffened and elongated, relative to their size during immaturity or 

 reproductive inactivity. Enlargement of the maxillary barbel is due to 

 hyperossification of the maxilla, which extends from its normal basal position above 

 the upper lip, as a single, long bony projection into the core of the barbel (Fig. 16). 

 The surface of the barbel retains its epidermal integrity, confluent with the skin on 

 the surface of the upper Up. In breeding md\Q Ageneiosus, the barbels develop a 

 variable number of irregular, sharp, recurved odontodes along the dorsomedial and 

 dorsolateral margin (Fig. 16). In TetranemaHchthys and a number of auchenipterids. 



m 



