de VLAMING: CONTROL OF REPRODUCTION IN GILLICHTHYS 



Table 4. — Effect of various high temperature and photoperiod treatments on ovarian weight in Gillichthys mirabilis. 



Experi- 



menf 



number 



Length of 



treatment 



(Days) 



Temper- 

 ature 

 (°C) 



Photo- 

 period 



Weight of ovaries (mg) 

 (X ± SE) 



Initial controls 



♦Significantly less [P < 0.05) than initiail controls. 

 "♦Significantly less {P < 0.01) than initial controls. 



After treatment 



(n) 



of the May controls were in active spermatogen- 

 esis (Stage 3) or in the prespawning conditions 

 (Stage 4) ; ovaries of the May controls were in 

 active vitellogenesis (Stage III). The testes of 

 six of the eight fish at the short photoperiod, 

 however, were regressing (Stage 0); ovaries in 

 this group were regressing (Stage I) or in the 

 quiescent phase (Stage II). 



In contrast to the effects of short photoperiod 

 at 22°C, a long photoperiod (in May) did not 

 initiate testicular regression. Although testic- 

 ular weights in this group were significantly less 

 (P < 0.05) than those of the initial May con- 

 trols, the testes of all fish were in active sper- 

 matogenesis (Stage 3). Ovarian weights of fish 

 at a long photoperiod were also significantly low- 

 er (P < 0.01) than those of the initial May con- 

 trols; ovarian regression (Stage I) was occur- 

 ring in all fish. 



Beginning in September, 26-day exposure to 

 a short photoperiod (10L/14D) at 21°C stim- 

 ulated a significant increase (P < 0.05) in ovar- 



ian and testicular weights when compared to 

 gonadal weights in the initial controls (Exper- 

 iment 12 — Table 5). In contrast, neither ovar- 

 ian nor testicular weights in the long photope- 

 riod group were significantly altered. The testes 

 of the September controls were in Stage 2, and 

 the ovaries of this group were in early stages 

 of vitellogenesis ( Stage III ) . After short photo- 

 period treatment, the gonads of all fish were in 

 the meiotic phase of spermatogenesis (Stage 3) 

 or vitellogenesis (Stage III) ; the long photope- 

 riod, however, did not stimulate spermatogen- 

 esis (testes in this group were in Stage 1) and 

 caused ovarian regression (Stage I). 



Beginning in November (Experiment 13), 

 testicular weights were maintained at the initial 

 level for 21 days at 22°C and a short photoperiod 

 (10L/14D) ; testes of the initial controls and the 

 experimental fish were in Stage 3 or 4. A long 

 photoperiod at 22°C, however, caused the initi- 

 ation of testicular regression (Stage 0); testic- 

 ular weights in this group were significantly 



Table 5. — Effect of 21° and 22°C treatments on testicular and ovarian weight in Gillichthys mirabilis. 



Experi- 

 ment 

 number 



10 

 11 



11 



12 



12 



13 

 13 



Beginning 

 data 



April 

 May 



May 



September 



September 



November 

 November 



Length of 



treatment 



(Days) 



17 

 30 



30 



26 



26 



21 

 21 



Tempera- 

 ture 

 (°C) 



Photo- 

 period 



Gonadal v>/eight (mg) 

 (x ± SE) 



Initial 

 controls 



After 

 treatment 



(n) 



•Significantly different {P < 0.05) from initial controls. 

 •'Significantly different (P < 0.01) from initial controls. 



1145 



