. 134 



dimorphism between the sexes involving the dorsal profile of the head, size of the 

 eye, and pigmentation of the caudal fin, , ^ ,v -" " 



The above references are the principal studies that addressed, to any 

 significant extent, sexually dimorphic characters in species of ageneiosids. In 

 addition to the above sources, a few other early studies included remarks about 

 sexual dimorphism in various auchenipterids, as summarized by Vari et al. (1984) 

 and Ferraris (1988). 



The first paper that explicitly impHcated the functional significance of 

 sexually dimorphic characters in a doradoid catfish was that of Ihering (1937). 

 Therein, he described the gross morphology, gametogenesis, and internal 

 fertilization of the auchenipterid Trachycorystes striatulus (= Trachefyopterus 

 striatulus, possibly synonymous with T.galeatus according to Ferraris 1988). Ihering 

 gave a relatively detailed account of the gross anatomy of the gonad of both sexes, 

 and described the general appearance of the gametes in ripe individuals. He did not 

 observe courtship or copulation behavior, but Ihering provided evidence of internal 

 fertilization in this species on the basis of the unique anal fin and testes morphology 

 in males, and direct observation of spermatozoa suspended in a gelatinous plug 

 within the oviducts of gravid females. Females apparently retain sperm within their 

 reproductive tracts for at least four months, and fertilization was believed to occur 

 at the time of oviposition. Ihering briefly summarized previous classification 

 schemes of various auchenipterids, and, based on observations of a "pseudopenis" in 

 some and speculation of its occurrence in others, divided the family into two 

 subfamilies on the presumed presence or absence of "oviducal" (internal) 

 fertilization in the group; he further suggested that no less than 30 species (in his 

 subfamily Trachycoristinae) probably had internal fertihzation. 



Ihering's (1937) study went largely unnoticed until the work of Miranda- 

 Ribeiro (1968a, 1968b), who provided additional illustrations of external, sexually 

 dimorphic characters in several species. Miranda-Ribeiro presented no additional 



