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UROGENITAL SYSTEM 



The only references to the anatomy of the 

 urogenital system are those of Kishinouye (1923) 

 on Sarda orientalis and Godsil (1954, 1955) on S. 

 cn-ientalis and S. chiliensis. 



General Description. -The paired gonads lie 

 along the dorsolateral body wall and are visible in 

 ventral view in mature adults. The kidney lies 

 dorsal to the layer of fibrous connective tissue 

 which forms the dorsal layer of the peritoneum. 

 Anteriorly, the kidney divides into a pair of 

 narrow projections which extend along the sides of 

 the parasphenoid and usually reach the posterior 

 end of the "mid-ridge" of the prootic. The anterior 

 ends of the kidney surround the origins of the 

 pharyngeal muscles on the vertebral column and 

 usually separate along the middle of the vertebral 

 column. The kidney may be absent in the area 

 between the vertebrae and where the epibranchial 

 arteries join to form the aorta. In some cases in 

 each species, the kidney is well developed dorsal to 

 this area and even covers the posterior end of the 

 parasphenoid. In the vicinity of the esophagus, the 

 kidney expands laterally and forms two projec- 

 tions which may reach anteriorly to the upper end 

 of the gill slits. Posteriorly, near the posterior fifth 

 of the body cavity, the kidney narrows to an elon- 

 gate triangle (Figure 7). The branches of the 

 ureter join to form a common trunk which leads to 

 the urinary bladder between the gonads. The dis- 

 tance between the junction of the ureters and the 

 urinary bladder and the size of ureters varies in- 

 traspecifically. The urinary bladders appear 

 similar in all the bonitos, but no detailed study was 

 made of them. 



OLFACTORY ORGAN 



General Description. — Kishinouye (1923) 

 provided a generalized account of the olfactory 

 organ of several scombrids. More detailed studies 

 have been made on Scomber scombrus (Burne 

 1909), Sarda sarda (Tretiakov 1939), Allothunnus 

 fallai (Nakamura and Mori 1966), Katsuwonus 

 pelamis (Gooding 1963), and Thunnus (Iwai and 

 Nakamura 1964b; Gibbs and CoUette 1967). As in 

 other scombrids, the olfactory cavity in bonitos has 

 a small anterior naris and a slitlike posterior naris. 

 No information on the supplementary sacs, or 

 accessary olfactory cavity (Iwai and Nakamura 

 1964b), was obtained from the present study com- 



parable to that of Tretiakov (1939), who described 

 three supplementary sacs (middle, maxillary, and 

 rostral sacs) in S. sarda. The central axis of the 

 olfactory rosette is located beneath the anterior 

 naris. Leaflike laminae radiate from the central 

 axis and occupy the anterior dorsal third of the 

 olfactory cavity. Gooding (1963) studied the 

 morphology and histology of the olfactory organ 

 of Katsuwonus pelamis and found olfactory cells 

 on the olfactory epithelium of the laminae. Iwai 

 and Nakamura (1964b) were the first to use the 

 number of laminae to distinguish species of 

 scombrids, but Gibbs and Collette (1967:91) felt 

 additional material was necessary to validate the 

 character in Thunnus. 



We counted the number of olfactory laminae (by 

 averaging both sides and rounding upward) in 

 bonitos and found a rather wide range of variation 

 (Table 3). Gooding (1963) also found a wide varia- 

 tion in Katsuwonus: 38-47 laminae per rosette in 

 38 skipjack olfactory rosettes. The number of 

 laminae increases from small specimens to adults 

 but does not appear to change after a certain size 

 is reached. For example, 15 specimens of Or- 

 cynopsis unicolor (242-645 mm FL) had 25-28 

 laminae, a 178-mm specimen had 22, and a 164-mm 

 specimen had 23. Twelve Gymnosarda unicolor 

 (400-940 mm FL) had 48-56 laminae; a 306-mm 

 specimen, 45; a 215-mm specimen, 43; and a 71.6- 

 mm specimen, 27. Looking only at adults and 

 subadults (Table 3), Gymnosarda has the highest 

 number of olfactory laminae (48-56) and is 

 completely separated from the other bonitos 

 (21-39) in this character. Orcynopsis, Cybiosarda, 

 and Sarda australis form a series with increasing 

 numbers of laminae. 



The pigmentation of the olfactory rosette 

 varied in preserved specimens. In S. australis and 

 Orcynopsis the dorsal margins of the olfactory 

 laminae were pigmented and gave a radial pig- 

 mentation to the olfactory rosette. Black spots 

 were found on the laminae of a specimen of 

 Cybiosarda (Figure 8a). The fleshy ring of S. sarda 

 showed grayish pigmentation in large specimens. 

 No specific pigmentation was noted in other 

 species of bonitos. The morphology of each olfac- 

 tory lamina (Figure 8) is similar in each olfactory 

 rosette, but decreased in size anteriorly. The ol- 

 factory cavity and accessary cavity are similar in 

 all bonitos, except in Cybiosarda where the open- 

 ing of the accessary sac was more dorsally located 

 and led interiorly rather than interior-ventrally as 

 in other bonitos. 



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