the barbels are much longer and lack any sharp recurved odontondes, although they 

 may be rugose or weakly tuberculate on their dorsal margin. 



The dorsal fin of nuptial males is curved and much longer than in females or 

 nonbreeding males, and is armed along its anterior margin with numerous sharp 

 odontodes (Fig. 23). The anterior part of the base of the fin is swollen, and the 

 spine can be thrust and locked in position above the head. The nuchal region in 

 nuptial males is also enlarged, and has a much more acute angle behind the 

 supraoccipital than is present in females or nonbreeding males. The swollen 

 appearance of the nape is apparently due to osteological changes (Ferraris 1988), as 

 well as an increase in the mass of the musculature encircling the base of the dorsal 

 fin (personal observation). , - . ' ,s 



The anal fin is modified into an intromittent organ, formed from thickened 

 and elongated anterior rays, and displacement of the gonopore to the distal tip of 

 the swollen rays (Figs. 29, 31). The interradial membranes and the inclinator and 

 erector muscles surrounding the gonopodium are enlarged. s ■ 



The sexual dimorphism exhibited by ageneiosids is paralleled by dimorphism 

 in a number of auchenipterids. There are significant morphological differences 

 among the various genera for which there are available data (Ferraris 1988). 

 Nevertheless, from the nature of these differences and the observations and 

 photographs pubUshed in Burgess (1982) and Kopke (1986), it appears that males 

 use the barbels and dorsal fin spine to court and manipulate females, accompanied 

 by spawning or copulation, in which the gonopodium is either closely apposed or 

 inserted into the gonopore of the female. v,,^ 



■ s" ■■■-':»' 



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Gonad Anatomy of the Ageneiosidae 



There has been no previous study of the soft anatomy of the reproductive 

 system in any of the sexually dimorphic doradoids. Ihering (1937) examined the 



