maintained a standard respiratory rate of ap- 

 proximately 200 mmVg/hr. 



On removing these fish from the apparatus, 

 their behavior was seen to be very different from 

 control animals kept in 30-liter aquaria and sim- 

 ilar to the previously described behavior of fish 

 treated with thyroxine (Sage, 1968). Thus all 

 fish jumped during a 15-min period after trans- 

 fer from the respirometer to a 50 X 25 cm aquar- 

 ium with a depth of 2.5 cm of water while only 

 179r of control animals jumped (Table 2). Sim- 

 ilarly all fish kept for 7 days in 500-ml contain- 

 ers and fed ad libitum jumped when transferred 

 to shallow water. The response was therefore 

 to the restricted containers and not to the abnor- 

 mal once-per-day feeding regime imposed in the 

 respirometer. 



Table 2. — Effect of maintenance conditions or thyroxine 

 on frequency of jumping. 



Percenlage jumping 

 (number of individuals) 



Sections through the proximal pars distalis 

 showed a degranulation of the TSH cells in the 

 pituitary glands of both groups of fish that had 

 been kept in restricted environments. This was 

 not seen in control animals. Stimulation of the 

 thyroid gland is thus a probable cause of the 

 observed changes in behavior and may also ac- 

 count for the respiratory changes. A fall in 

 standard respiratory rate has been previously 

 observed and attributed to progressive starva- 

 tion (Fry, 1957). This cannot explain the pres- 

 ent results since all respiratory measurements 

 were made an equal time after a feed. 



The responses reported here were obtained 

 with container to fish volume ratios of 100 and 

 500: 1. These are larger than the chambers used 

 in most fish respiration studies. Thus Geyer and 

 Mann (1939) suggested a ratio of at least 10:1 

 for Perca. 



The present observations indicate that accli- 

 mating fish to a restricting apparatus may stim- 

 ulate the TSH cells and thyroid and produce 



changes in behavior and respiration. This may 

 be particularly confusing where seasonal changes 

 are being investigated since thyroxine has been 

 implicated in processes of acclimation (Hoar, 



1959) and seasonal changes in fish thyroid ac- 

 tivity are widespread (Matty, 1960; Swift, 



1960) and may be related to seasonal changes 

 in respiratory rate (Fisher, 1958). 



Literature Cited 



Bbiggs, R., G. V. Dyke, and G. Knowles. 



1958. Use of the wide-bore dropping-mercury elec- 

 trode for long-period recording of concentrations 

 of dissolved oxygen. Analyst 83: 304-311. 



Fisher, K. C. 



1958. An approach to the organ and cellular phy- 

 siology of adaptation to temperature in fish and 

 small mammals. In C. L. Prosser (editor). Phys- 

 iological adaptation, p. 3-49. American Physio- 

 logical Society, Washington, D.C. 



Fox, H. M., AND C. A. WiNGFIELD. 



1938. A portable apparatus for the determination 

 of oxygen dissolved in a small volume of water. 

 J. Exp. Biol. 15: 437-445. 



Fry, F. E. J. 



1957. The aquatic respiration of fish. In M. E. 

 Brown (editor). The physiology of fishes, vol. 1, 

 p. 1-63. Academic Press, New York. 



Geyer, F., and H. Mann. 



1939. Beitrage zur Atmung der Fi.sche. IV. Die 

 Bedeutung der Grosse der Atemkammer fiir den 

 Sauerstoffverbraueh in fliessendem Wasser. Z. 

 vgl. Physiol. 27: 443-444. 



Hoar, W. S. 



1959. Endocrine factors in the ecological adapta- 

 tion of fishes. In A. Gorbman (editor). Compar- 

 ative endocrinology, p. 1-23. Wiley, New York. 



Matty, A. J. 



1960. Thyroid cycles in fish. Symp. Zool. Soc. 

 London 2: 1-15. 



Sage, M. 



1968. Respiratory and behavioral responses of 

 Poecilia to treatment with thyroxine and thiourea. 

 Gen Comp. Endocrinol. 10: 304-309. 

 Swift, D. R. 



1960. Cyclical activity in the thyroid gland of fish 

 in relation to environmental changes. Symp. 

 Zool. Soc. London 2: 17-27. 



Martin Sage 



University of Texas 

 Marine Science Institute 

 Port Aransas, Tex. TS373 



880 



