de VLAMING: CONTROL OF FATTENING IN NOTEMIGONUS 



under these same conditions body lipid levels were 

 also significantly lower in pinealectomized than in 

 sham operated fish. Ovarian GSI was significantly 

 higher in the pinealectomized than in sham 

 operated group exposed to the 9L/15D-12°C 

 regime; however, body fat levels were sig- 

 nificantly lower in pinealectomized than in sham 

 operated fish under these conditions. These data 

 imply that the effects of pinealectomy on lipid 

 deposition do not necessarily depend on the effects 

 of this organ on reproductive activity. 



Prespawning Season 



The effects of pinealectomy on body fat 

 reserves were examined again during the pre- 

 spawning season (Table 2). 



Regardless of photoperiod, low temperature 

 treatment of both sexes of sham operated 

 Notemigonus resulted in a significant increase in 

 body fatness, compared to the initial March con- 

 trols. Warm temperature treatment, however, 

 caused a depletion of body lipids in sham operated 

 fish compared to the initial controls; this fat 

 depletion was observed in both photoperiod 

 groups. 



Body fatness (in females) was significantly 

 greater in sham operated control fish exposed to 

 the 9L/15D-12°C regime than in animals main- 

 tained on the 15.5L/8.5D-12°C regime. These data 

 further confirm the suggestion that short 

 daylengths compliment the effects of low 

 temperatures on fattening. Body lipid levels (both 

 sexes) were significantly lower in sham operated 

 animals maintained on the short photoperiod- 

 warm temperature regime than in sham operated 

 fish exposed to the long photoperiod-warm 

 temperature regime. The lipid depletion which oc- 

 curs at warm temperatures is thus accentuated by 

 short daylengths. 



Body fat levels (both sexes) were significantly 

 lower in the pinealectomized group than in the 

 sham operated group maintained on the 

 15.5L/8.5D-25°C regime. In animals maintained 

 on a long photoperiod-low temperature regime, 

 body lipid levels were significantly greater in the 

 pmealectomized fish than in the shams. Pinealec- 

 tomized females contained significantly more fat 

 than sham operated females exposed to the short 

 photoperiod-warm temperature regime. In con- 

 trast, body lipid levels (both sexes) were sig- 

 nificantly lower in pinealectomized than in sham 

 operated fish maintained on the 9L/15D-12°C 



Table 2.-The effects of pinealectomy on body lipid reserves in 

 Notemigonus maintained on various photoperiod-temperature 

 regimes during the prespawning season (21-day treatment). 



'Dry lipid index = mg lipid, less gonadal lipids/g dry body wt. 

 ^Gonosomatic index = wt of gonads (g)/g body wt x 100. 

 'Significantly (P<0.05) different than sham operated controls 

 maintained under same photoperiod-temperature regime. 



regime. At a low temperature, pinealectomy in- 

 terferes with the complimentary effects of short 

 photoperiods on lipid deposition. At d warm 

 temperature, however, pinealectomy reverses the 

 accentuating effects of short photoperiods on body 

 lipid depletion. 



Interestingly, body lipid levels in pinealec- 

 tomized females maintained on the 9L/15D-12°C 

 regime did not differ significantly from fat levels 

 in sham operated females exposed to the 

 15.5L/8.5D-12°C regime. Fat levels were not sig- 

 nificantly different in pinealectomized females on 

 the 15.5L/8.5D-12°C regime and sham operated 

 females on the 9L/15D-12°C regime. Similarly, 

 body fat levels in pinealectomized fish (both sexes) 

 exposed to the 9L/15D-25°C regime did not differ 

 significantly from lipid levels in shams maintained 

 on the 15.5L/8.5D-25°C regime. These data in- 

 dicate that pinealectomy reverses the effects that 

 photoperiod has on lipid levels at a given 

 temperature. 



Pinealectomy reverses the stimulatory effects 

 of a long photoperiod-warm temperature regime, 

 causing gonadal regression (de Vlaming 1975); 

 under these conditions body lipid levels in 

 pinealectomized animals are lower than in shams. 

 Short photoperiods in combination with warm 



769 



