pneumatic duct with a well-defined lumen still 

 appeared to form a connection between the gut 

 and the gas bladder. However, in the older larvae 

 of this group, the lumen of the pneumatic duct 

 was smaller. In some sections, the openings be- 

 tween the pneumatic duct and the gut and the 

 pneumatic duct and the gas bladder were not 

 plainly visible, indicating that the pneumatic 

 duct was beginning to atrophy. 



We examined 14- and 21-day-old striped bass 

 larvae without inflated gas bladders, and 24- 

 day-old larvae with and without inflated gas 

 bladders. In 14-, 21-, and 24-day-old larvae that 

 had noninflated gas bladders, a well-developed 

 rete mirabile still ran ventral and parallel to the 

 gas bladder, turning dorsally to make a medial 

 connection. The retail capillary network was de- 

 veloped, distending the overlaying connective tis- 

 sue into a villuslike structure which was bor- 

 dered by the ventral, columnar (secretory) 

 epithelium of the gas bladder. The villuslike pro- 

 jections occupied most of the internal volume of 

 the gas bladder. The pneumatic duct was well 

 defined and continued to connect the gut with the 

 gas bladder. 



In 24-day-old striped bass larvae that had 

 inflated gas bladders the pneumatic duct was ab- 

 sent. Unfortunately, we did not collect any 

 striped bass larvae with inflated gas bladders be- 

 tween day 8 and day 24. We were thus unable to 

 accurately describe the atrophication of the 

 pneumatic duct, which seemingly occurs after 

 inflation of the gas bladder. The rete mirabile was 

 connected to a narrow band of cuboidal 

 epithelium at the ventromedial wall of the gas 

 bladder. 



Discussion 



Striped bass larvae possess an open pneumatic 

 duct. An experiment designed to determine if 

 striped bass have to gulp surface air to initiate 

 gas bladder inflation was inconclusive, as was a 

 similar experiment conducted by Doroshev and 

 Cornacchia (1979). However, allowing striped 

 bass larvae unobstructed access to the surface did 

 not guarantee inflation in either study. 



In our study, the pneumatic duct had atrophied 

 in 24-day-old larvae which had inflated their gas 

 bladders, but an open pneumatic duct was still 

 present in 24-day-old larvae which had not 

 inflated their gas bladders. This suggests that 

 inflation of the gas bladder stimulates the at- 



rophication of the pneumatic tube in striped bass. 

 Johnston (1953) observed a similar phenomenon 

 in the largemouth bass, Micropterus salmoides. 



The rete mirabile, or gas gland, is developed 

 before initial inflation of the gas bladder in larval 

 striped bass. Since the gas gland concentrates 

 gases within the gas bladders of many adult 

 fishes, it is reasonable to assume that the gas 

 gland plays a role in achieving initial inflation of 

 the gas bladder in larval striped bass. The con- 

 tinued presence of a gas gland, and the prolonged 

 retention of an open pneumatic duct in striped 

 bass larvae that had not achieved initial inflation 

 of the gas bladder within 24 days suggests that 

 initial inflation may occur over an extended period 

 of time. 



Other workers have indicated that failure to 

 initiate inflation of the gas bladder may lead to 

 slower growth rates (Tait 1960), a higher per- 

 centage of morphological abnormalties (Baker^), 

 and an increased susceptibility to stress (Lewis et 

 al.''). Studies designed to define the stimuli re- 

 sponsible for the initiation of gas bladder infla- 

 tion in striped bass, an important sport fish 

 species that is often cultured, would be beneficial. 



Literature Cited 



Doroshev, S. I., and J. W. Cornacchia. 



1979. Initial swim bladder inflation in the larvae of 

 Tilapia mossambica (Peters) and Morone saxatilis (Wal- 

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 GUNTHER.A. C. L. G. 



1880. An introduction to the study of fishes. Adams and 

 Charles Black, Edinb., 720 p. 



Johnston, p. m. 



1953. The embryonic development of the swim bladder of 

 the largemouth black bass Micropterus salmoides sal- 

 moides (Lacepedel. J. Morphol. 93:45-67. 



Lagler, k. F, J. E. Bardach, and r. r. Miller. 



1962 Ichthyology. Wiley,N.Y.,545p. 

 McEWEN.R. S. 



1940. The early development of the swim bladder and cer- 

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 POWERS, E. B. 



1932. The relation of respiration of fishes to environ- 

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 SCHWARZ, A. 



1971 , Swimbladder development and function in the had- 



^Baker, J. F. 1975. The rearing of Hudson River striped 

 bass at the Edenton National Fish Report prepared for 

 Consolidated Edison Company of New York, Inc.. 30 p. 



^Lewis. W. M., R. C Heidinger, and B. L. Tetzlaff. 

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