COLLETTE and CHAO: SYSTEMATICS AND MORPHOLOGY OF THE BONITOS (SARDINI) 



Orcynopsis. The gall bladder, an elongate tubular 

 sac which is usually green in color, arises from the 

 right lobe of the liver and usually lies along the 

 intestine on the right hand side. The stomach ex- 

 tends further posteriorly and is more prominent in 

 ventral view when it is full. The mature ovary is 

 sometimes large enough to cover the stomach 

 ventrally. A swim bladder is absent in all bonitos 

 except Gymnosarda. 



Specific Characters.— The bonitos are divided 

 into three groups based on the shape of the liver 

 (Figure 4). Sarda and Gymnosarda have three 

 distinct liver lobes; both lateral lobes are elongate 

 and much longer than the middle lobe; the right 

 lateral lobe is always longer than the left lateral 

 lobe. All three lobes in Gymnosarda are visible 

 ventrally if the dissection extends far enough 

 laterally. In addition, the connection of middle and 

 left lobes is visible ante rove ntrally in Sarda. Or- 

 cynopsis and Cyhiosarda have an elongate right 



lateral lobe and a very short left lateral lobe which 

 tends to fuse with the middle lobe. Allothunnus 

 differs from the other genera in having three 

 subequal lobes, as in the bluefin tuna group of 

 species of Thunnus. 



The bonitos can be divided into three groups 

 based on the relative length of the caecal mass. 

 Allothunnus has the longest caecal mass (71-81% 

 of body cavity length, x 76.4%) of any of the boni- 

 tos followed by Cyhiosarda (65-72%, x 69.2%) and 

 Orcynopsis (46-59%, x 56.3%). Gymnosarda has the 

 shortest caecal mass (22-30%, x25.2%). The species 

 of Sarda are intermediate between these two 

 groups, most having the caecal mass about half the 

 length of the body cavity (S. australis 44-55%, x 

 49.7; S. sarda 38-58%, x 48.3; and S. orientalis 41- 

 50%, ^46.7). There is significant geographic varia- 

 tion in the fourth species, S. chiliensis. Three 

 northeast Pacific specimens have a distinctly 

 longer caecal mass (61-65%, x 62.3) than six 

 southeast Pacific specimens (40-53%, x 48.5). This 



CYBIOSARDD 



ORCYNOPSIS 



ALLOTHUNNUS 



GYMNOSARDA 



australis 



SARDA 



chiliensis 



orientalis 



sordo 



FiGUKE 4.- Ventral view of excised livers of eight species of Sardini. Spleen shown in black for Cj^noaarda and Orcynopsis. 



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