COLLETTE and RUSSO: SPANISH MACKERELS 



stomach. At this point the main branches of the 

 pyloric caeca join the intestine. The caeca branch 

 and form a dense dendritic conglomeration, the 

 caeca] mass. Cells in the pyloric caeca are histo- 

 logically similar to those in the intestine and 

 produce enzymes such as lipase, maltase, trypsin, 

 and pepsin (Mota Alves and Tome 1970). The 

 intestine continues posteriorly and its course 

 appears to be species-specific. The intestine may 

 be a simple straight tube from stomach to anus, 

 have two descending and one ascending arm, or 

 have four bends with three descending and two 

 ascending arms. The spleen is prominent in ven- 

 tral view in most species but is hidden in others. 

 The gall bladder, an elongate tubular sac which 

 is usually green, arises from the right lobe of the 

 liver and usually lies along the first descending 

 arm of the intestine on the right side. A swim 

 bladder is present in Grammatorcynus , Acantho- 

 cybium, and S. sinensis (Fig. 5) but is absent in 

 the other 17 species of Scomberomorus. 



The Spanish mackerels can be divided into 

 three groups based on the number of folds in 

 the intestine. Grammatorcynus , Acanthocybium 

 (Fig. 2b, c), and S. niphonius (Fig. 3k) have a 

 straight gut not folded back on itself. Scomber- 

 omorus koreanus (Fig. 3f) has four folds and five 

 distinct arms. The other species all have two folds 

 and three long arms (Fig. 3). Collette and Russo 

 (1980) used this character to differentiate S. 

 munroi from the North Pacific S. niphonius. 



The spleen is large and centrally located in 

 ventral view in four species: guttatus, koreanus, 

 munroi, and plurilineatus. The spleen is smaller 

 and distinctly on the left side in ventral view in 

 seven species: brasiliensis , commerson, lineola- 

 tus, maculatus, multiradiatus , queenslandicus , 

 and sinensis. It is not visible in ventral view in 

 Grammatorcynus, Acanthocybium, and seven 

 species of Scomberomorus: cavalla, concolor, ni- 

 phonius, regalis, semifasciatus , sierra, and tri- 

 tor. 



VASCULAR SYSTEM 



The only published work on the vascular sys- 

 tem of the Spanish mackerels is on Japanese 

 species by Kishinouye (1923). No specialized sub- 

 cutaneous vascular system and no cutaneous ar- 

 teries or veins are present as they are in the 

 higher tunas, Thunnini, Auxis to Thunnus (Col- 

 lette 1979). Therefore, this description will be 

 confined to the anterior portion of the dorsal 

 aorta and the postcardinal vein. 



The efferent branchial (epibranchial) arteries 

 and coeliaco-mesenteric artery form a unit at the 

 anterior end of the dorsal aorta (Figs. 6, 7). Two 

 anterior epibranchials on each side unite to form 

 a common trunk, and these trunks join as the "Y" 

 of the aorta beneath the posterior part of the 

 skull or the first or second vertebra. The posterior 

 two epibranchials of each side unite immediately 

 before they join the aorta, usually ventral to the 

 second or third vertebra. As the aorta proceeds 

 posteriorly, it gives rise to the large coeliaco- 

 mesenteric artery on the right side ventral to 

 the second to fourth vertebrae. The coeliaco- 

 mesenteric artery has two or three main branches 

 which lead to the liver and other viscera. 



The postcardinal vein runs along the ventral 

 surface of the kidney (Fig. 8) from the vicinity 

 of the first complete haemal arch anteriorly in 

 the median line to the pectoral region. There it 

 curves to the right and discharges into the right 

 Cuvierian duct. Posteriorly, the postcardinal re- 

 ceives a pair of small veins at the level of each 

 vertebra. The postcardinal is composed of two 

 main branches that join anterior to the Y of the 

 ureter. The main branch leaves the haemal arch 

 dorsally and the small branch runs under the 

 surface of the kidney from the urogenital area. 



Five species of Scomberomorus (brasiliensis, 

 concolor, maculatus, regalis, and sierra) have 

 unique specializations of the right and/or left 

 fourth epibranchial arteries (Fig. 7c-g). Each of 

 these species has an artery arising from the 

 fourth left epibranchial artery. Other species of 

 the genus (e.g., S. guttatus and S. tritor, Fig. 7a, 

 b) lack these specializations. In S. concolor and 

 S. brasiliensis this branch is small and goes into 

 the muscular tissue surrounding the left dorsal 

 portion of the esophagus (Fig. 7d, 0. In S. macu- 

 latus and S. sierra, this branch is large and 

 becomes the dorsal left gastric artery (Fig. 7c, e). 

 In S. regalis this branch goes into the left lobe of 

 the liver (Fig. 7g, hepatic branch). Scomberomo- 

 rus maculatus and S. sierra have lost the connec- 

 tion between the dorsal left gastric artery and the 

 coeliaco-mesenteric artery. It is replaced by a 

 connection to the fourth left epibranchial artery. 

 In S. regalis, the left dorsal gastric artery seems 

 to have been reduced. 



Scomberomorus brasiliensis, S. sierra, and S. 

 regalis share a specialization of the right fourth 

 epibranchial artery. In these species an artery 

 connects the fourth right epibranchial artery 

 with a branch of the coeliaco-mesenteric artery 

 (coeliaco-mesenteric shunt, Fig. 7e-g). 



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