FISHERY BULLETIN: VOL. 73, NO. 4 



terns in sunfish. In F. similis, short photoperiods 

 promote fattening whereas long photoperiods 

 result in lipid depletion (de Vlaming, Sage, Charl- 

 ton, and Tiegs; de Vlaming et al. in press). Other 

 than these studies, little is known concerning the 

 potential role of daylength in controlling fatten- 

 ing cycles in teleosts. 



The results presented here on temperature and 

 photoperiod effects on fat storage are consistent 

 with environmental data. Lipid levels are lowest in 

 Notemigoniis collected during July, August and 

 early September; environmental temperatures are 

 high during this time and daylength is decreasing. 

 From mid-September through December 

 daylength and temperature continue to decrease. 

 Fat stores increase progressively during this time. 

 Beginning in mid or late February, lipid reserves 

 are progressively depleted until late June or July. 

 During this time, daylength and temperature are 

 increasing. 



A progressive decrease in body fat reserves was 

 observed in Notemigonus collected during the 

 preparatory, prespawning and spawning seasons 

 respectively. These data indicate that there may 

 be a relationship between lipid stores and 

 reproduction. Other investigators presented 

 evidence of body fat depletion associated with 

 increasing gonadal activity (Lovern 1934; Liih- 

 mann 1953; Idler and Bitners 1960; Woodhead 

 1960; Wilkins 1967; Lasker 1970). A long photo- 

 period, in combination with warm temperatures, is 

 required for final gonadal maturation and spawn- 

 ing in Notemigonus (de Vlaming 1975). These 

 conditions result in depletion of fat stores in this 

 species. The fat depleted from body storage sites 

 could possibly be utilized for the energy demands 

 of reproduction; in females, some of the body lipids 

 may also be converted to yolk precursors and 

 transported to the developing oocytes. So gonadal 

 activation by long photoperiod-warm tempera- 

 tures regimes may result in mobilization of body 

 lipid reserves. Possibly, however, gonadal ma- 

 turation may depend on the prior activation of 

 lipid mobilization enzyme systems by long pho- 

 toperiod-warm temperature regimes. The former 

 hypothesis gains some support from observations 

 of several investigators (e.g., Kobayashi 1953; 

 Egami 1955; Oguro 1956) which indicate that sex 

 steroids stimulate lipid synthesis in fishes. In vitro 

 studies with Notemigonus liver preparations 

 imply that estradiol-17^ stimulates synthesis and 

 transport of lipid by this tissue (Shing and de 

 Vlaming unpubl. data). My intention is not to 



imply that only sex steroids are involved in 

 regulation of lipid metabolism. Indeed, other hor- 

 mones such as insulin (de Vlaming and Pardo 1975) 

 and prolactin (see below) have distinct effects on 

 fat metabolism in Notemigonus. 



Low temperatures, regardless of photoperiod, 

 maintain vitellogenesis and spermatocyte 

 proliferation in Notemigonus, but will not 

 stimulate final ovarian or testicular maturation 

 (de Vlaming 1975). Low temperatures also main- 

 tain or increase body lipid reserves in this species. 

 These observations lend further support to the 

 suggestion that fat stores are in some way related 

 to reproductive activity. 



Short photoperiod-warm temperature regimes 

 cause gonadal regression in Notemigonus (de 

 Vlaming 1975). Body fat depletion also occurs 

 under these conditions. Obviously this fat deple- 

 tion is not associated with increased gametogenic 

 activity. Body lipid reserves also decreased in fish 

 maintained on long photoperiod-warm tempera- 

 ture regimes. Therefore, depletion of body fats 

 may be primarily associated with increased 

 energy requirements at high temperatures. In 

 Notemigonus, however, there is some indication 

 that sex steroid secretion is stimulated or remains 

 high in fish maintained on a short photoperiod- 

 warm temperature regime. Specifically, fish ex- 

 posed to these conditions either develop or main- 

 tain nuptial coloration. If such is the case, sex 

 steroids may be involved in mobilization and/or 

 utilization of lipid reserves. 



In a majority of the experiments reported here, 

 pinealectomy had a pronounced effect on body fat 

 reserves in Notemigonus. The effects of pinealec- 

 tomy on fat metabolism depend on the pho- 

 toperiod-temperature regime to which the 

 experimental animals are exposed. In all three 

 experiments, body lipid levels were significantly 

 lower in pinealectomized than in sham operated 

 females exposed to the long photoperiod-warm 

 temperature regime; similar results were obtained 

 with males in one experiment. Body lipid content 

 was significantly greater in pinealectomized than 

 in sham operated females in two of the three 

 experiments where fish were exposed to a short 

 photoperiod-warm temperature regime; similar 

 results were obtained in only one experiment with 

 males. These data indicate that, in fish maintained 

 at warm temperatures, the effects of pinealec- 

 tomy depend on photoperiod conditions. During 

 the prespawning and spawning seasons, pinealec- 

 tomy reversed the effects of photoperiod on fish 



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