HORN: SWIM-BLADDER STATE AND STRUCTURE 



RESULTS 



Swim-Bladder Structure 



The stromateoid swim bladder is of the 

 physoclistous, two-chambered type usually found 

 in perciform fishes (Horn 1970a) (Figure 1). The 

 delicate, thin-walled sac lies in the upper part of 

 the body cavity above the gut and below the 

 kidney and is closely invested by the dorsal 

 peritoneum. A muscular diaphragm (not always 

 visible) divides the bladder into anterior and 



posterior chambers (Figures 1, 2), the latter of 

 which serves a gas-resorbing function (a 

 euphysoclistous condition). The gas gland, as- 

 sociated with the anterior chamber, typically 

 forms a U-shape and may be single or divided into 

 two or more lobes (Figure 1). Cells composing the 

 gland are cuboidal to irregular in shape and 

 usually in two or more layers (Figures 2-5). Some 

 cells appear to be either syncytial or of the giant 

 type found widely distributed in marine euphysoc- 

 lists (Fange 1953) and in some deep-sea fishes 

 (Marshall 1960). The retia mirabilia are unipolar, 



Figure 1. — Ventral view of the swim bladder of 11 species of stroma teoids (all drawn to same scale), gg, gas gland (slightly flattened 

 and expanded); rm, rete mirabile; ra and rv, retial artery and retial vein; ac, anterior chamber; d, diaphragm; pc, posterior chamber. 

 A, Ariomma bondi, 24.2 mm SL; B,Centrolophus maoricus, 15.1 mmSL; C, Tetragonurus cuvieri , 28.8 mmSL; D, Seriolella violacea , 

 12.8 mm SL; E,Cubiceps gracilis, 30.5 mm SL; F, Schedophilus medusophagus , 17.4 mm SL (lateral and ventral view); G, Psenes 

 cyanophrys ,11.5 mm SL; H, Nomeus gronovii ,26.4 mm SL; I, Stromateus fiatola , 34. 1 mm SL; J, Icichthys lockingtoni ,16.3 mm SL; K, 

 Hyperoglyphe antarctica, 34.9 mm SL. 



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