STRIATA 



GEORGE I 



BRUCEI 



STEWARTI 



Figure 4. — Co-occurrence of four species of Argentina in 

 the western Atlantic. Solid lines connect species talien 

 from the same trawl. A clotted line connects species 

 taken In different trawls at the same or closely adjacent 

 localities. 



and he, tlierefore, used the character taxonomi- 

 cally, although always in company with other 

 characters. We here point out errors in Cohen's 

 observations and comment on the variability of 

 this character. In his key to the species of Argen- 

 tina and in his diagnosis of A. striata Cohen stated 

 that A. striata lacked a silvery-pigmented swim- 

 bladder. We have exammed the swimbladders of 

 150 specimens of A. striata from tliroughout the 

 range of the species and find that most, though not 

 all of them, have definite silvery pigment. Cohen 

 probably based his 1958 statement on examples of 

 one or more of the other three species of Argentina 

 from the -western Atlantic. 



The swimbladder of A. striata may have any 

 one of four patterns of pigmentation. In one, the 

 entire out«r part of the organ is heavily coated 

 with guanine (fig. 5) ; in the second, the anterior 

 and posterior quarters of the bladders are pig- 

 mented with guanine, but the intervening segment 

 lacks silvery pigment (fig. 5) ; in the third, only 

 the posterior segment is pigmented with guanine; 

 in the fourth and rarest type, the outer layer is 



faintly iridescent or appears to lack any impregna- 

 tion of guanine. 



In all but two instances, all specimens of A. 

 brucei lack silvery pigment on the swimbladder 

 (fig. 5). In a collection of six specimens from 

 Venezuela (UF 5237), five individuals have irides- 

 cent to silvery pigment on each swimbladder, and 

 a single individual lacks pigment completely. Also, 

 one of three specimens from Honduras (FMNH 

 74571) has a silvery swimbladder. 



All specimens examined of A. stewarti lack 

 definite silvery pigment (fig. 5) ; however, one 

 had a slightly iridescent swimbladder. A few 

 examples of A. georgei have slightly iridescent 

 swimbladders. 



The specimens of A. australiae^ eloivgata, and 

 hagosMmae listed by Cohen (1958) were reex- 

 amined. The bladders were iridescent in australiae; 

 pigment was lacking in the other two species. 



The swimbladder pigmentation patterns dis- 

 cussed in this paper are valid only in preserved 

 specimens. 



Fiinge (1958) has suggested that guanine might 

 help to keep gases in the bladder. It would be in- 

 teresting to test the diffusion rate of gases through 

 the swimbladder walls of pigmented and unpig- 

 mented species of Argentina. In this respect we 

 note that the small posterior chamber of the 

 Argentina swimbladder, first described by Cohen 

 (1958) and shown by Fahlen (1965) to have a re- 

 sorbent function, invariably lacks silvery pigment. 



According to Cohen (1958), argentinine fishes 

 are physoclists that lack a rete mirabile. Such 

 a condition is, of course, highly improbable unless 

 there is some unknown methofl of gas being se- 

 creted into and maintained in the swimbladder. 

 Argentina does in fact have a rete, which has been 

 described for A. silus by Fiinge (1958). He noted 

 that it is a unique stnicture, different from the 

 rete of other kinds of fishes. Marshall (1960) 

 named it a micro-rete and described it in several 

 other genera of argentinoid fishes. 



KEY TO SPECIES OF ARGENTINA 



la. Branchiostegal rays 6, scales with spines ^_ 



lb. Branchiostegal rays 5, scales lacking spines S. 



2a. Lateral line scales 52 (50-54); gill rakers on lower arm of first arch 8 (7-10) A. sphyraena. 



2b. Lateral line scales 67 (64-69); gill rakers on lower arm of first arch 13 (11-17).. A. sUm. 

 3a. Gill rakers on lower arm of first arch 14-21; jaw relatively large, snout to max- 

 illary tip distance usually less than 5 in head 4. 



ADDITIONS TO A REVISION OF ARGENTININE FISHES 



17 



