FISHERY BULLETIN: VOL. 73, NO. 1 



Table 3. ^-Surface area of the gas gland (mm^) and length of the rete mirabile (mm) relative to swim-bladder volume (mm^ or ml) or 

 dimension (length x width, in mm) in the European eel, certain shallow-sea and deep-sea fishes, and in 12 species of stromateoids. 

 Total capillary length (m) = retial length x number of retial capillaries. Retial lengths of stromateoids are means of individuals for 

 each species. 



Species 



European eel' 



Anguilla anguilla 

 Shallow-sea (epipelagic):' 



Cypsilurus cyanopterus 



Danichthys rondeletll 



Exocoetus volitans 



Petalichthys capensis 



Hyporhamphus sp. 



Scomberesox saurus 



Gadus minutus 



Capros aper 

 Deep-sea:' 



Gonostoma denudatum 



Pollichthys mauli 



Bonapartia pedaliota 



Vinciguerria attenuata 



Vinciguerria nimbaria 



Argyropelecus aculeatus 



Polyipnus laternatus 



Astronesthes niger 



Astronesthes similis 



Myctophum punctatum 



Benthosema suborbitale 



Lampanyctus guntheri 



Diaphus rafinesquei 



Melamphaes megalops 



Stephanoberyx monae 



Chiasmodon niger 

 Sfromateoids: 



Hyperoglyphe antarctica 



Schedophilus medusophagus 



Icichthys lockingtoni 



Seriolella violacea 



Stromateus fiatola 



Peprilus triacanthus 



Amarsipus carlsbergi 



Cubiceps gracilis 



Nomeus gronovii 



Psenes cyanoplirys 



Tetragonurus cuvieri 



Ariomma bondi 



'Data from Marshall (1960). 



gradual process which makes difficult the 

 determination of the exact time of loss of function. 

 Several stages are recognizable in the process 

 although they vary in appearance, and both the 

 stages and the overall regression vary in duration 

 among and within species. Estimated ranges of 

 fish size during which regression occurs in nine 

 stromateoid species are given in Table 4. 



Early in the regression the gas gland contracts 

 and thickens and the sac begins to decrease in size. 

 Later the gas gland and retia mirabilia become 

 atrophied as the cells and capillaries lose integrity 

 (Figure 7). A yellowish-white material, possibly 

 lipid, frequently invests the gas gland. Finally, 

 the swim-bladder wall is resorbed, and the gas 

 secreting and absorbing complexes become indis- 

 tinct. A large stromateoid (> 100-200 mm SL, see 

 Table 4) may have either a small irregularly 



shaped mass of yellowish-white material lying in 

 the dorsal mesentery (Figure 7) as the only 

 remnant of the swim bladder or no visible trace at 

 all of the organ. 



DISCUSSION 



Relative Dimensions and Capabilities 

 of the Swim Bladder 



Volume 



Mean percentage volumes were relatively 

 small, 0.6-3.4% (Table 2), and generally below the 

 3.1-5.7 range for the swim bladder calculated by 

 Alexander (1966) to be necessary for neutral 

 buoyancy in seawater. A number of mid-water 

 fishes also have swim bladders of low volume 



102 



