168 

 ARGENTINIDAE 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



MICROSTOMATIDAE BATHYLACIDAE OPISTHOPROCTIDAE 



3,4,5,6,7, 

 (13), (14) 



Fig. 88. Cladogram showing the distribution of character states in four nominal families of argentinoid fishes. Numbers refer to characters in 

 Tables 42 and 43. Parentheses mdicate character reversals. 



and in the gut region there is pigment above the terminal section 

 and ventral to the liver. Head pigment is confined to the lower 

 jaw. The pigment pattern of Rhynchohyalus as described by 

 Bertelsen et al. (1965) consists of a series of four dusky bars 

 beginning at the pelvic fin and ending at the caudal fin base. 

 Embedded beneath these is a layer of diffuse melanophores 

 which becomes denser toward the caudal. The pectoral fin bases 

 are pigmented and in the ventral region there are melanophores 

 on the isthmus and gut. The anal light organ is covered with a 

 melanistic sheath. The late larval specimen of Opisthoproctus 

 grimaldii illustrated by Schmidt (1918) shows a diffuse covering 

 of melanophores over the body and a dusky bar extending down 

 from the dorsal fin. A 10 mm larva of O. so/eat us in our col- 

 lection has a pigment pattern similar to Macropuma, with a 

 series of slanted melanophores on the hypaxial myomeres, 

 embedded blotches at the pelvic and caudal fin bases, pigment 

 at the liver and ventrally at the angles of the lower jaw. 



Transformation stage 



In argentinids transformation from larva to demersal juvenile 

 is a prolonged process and pelagic juveniles with the retained 

 larval pigment blotches or bars have been reported many times 

 (see Cohen, 1958; Nishimura, 1966). Morphological changes 

 (e.g., deepening of the body, prolongation of the snout, eye 

 enlargement) and the masking of the larval pigment occur grad- 

 ually. The beginning of this stage may be defined by the folding 

 of the anterior gut region to form a stomach. This occurs at 25- 



30 mm in Argentina sialis, but has not been documented for 

 other species. Pelagic juveniles of Glossanodon and A. sialis 

 develop a silvery stripe at the lateral line region. This has not 

 been reported for pelagic juveniles of A. silus and A. sphyraena 

 and may afford an additional character for separating Argentina 

 into two groups. The end of the pelagic juvenile stage, marked 

 by the development of scales and silvery integument, is attained 



Table 43. Distribution of Char.acter States in Folir Nominal 

 F.MHILIES OF Argentinoid Fishes. Direction of transformation A * B. 



