lighting conditions were reported to alter the 

 secretory activity in the glandular appearing 

 pineals of Gambusia affinis and Sijmphodus 

 melops (Cheze and Lahaye 1969; Cheze 1970). Pos- 

 sibly then, the pineal in some teleost species may 

 function as a neuroendocrine transducer of pho- 

 toperiod information. If the pineal is a neuroen- 

 docrine organ, melatonin could conceivably be one 

 of the hormones produced by this organ. Although 

 the pineal of Notemigonus does seem to be in- 

 volved in photoreception, available evidence does 

 not allow one to conclusively state that this organ 

 is neuroendocrine in nature or that pineal- 

 produced melatonin functions as a chemical mes- 

 senger. 



The pineal may modify fat stores in 

 Notemigonus by influencing hypothalamic and/or 

 pituitary function. Indeed, de Vlaming and 

 Vodicnik (in press) showed that pinealectomy 

 alters hypothalamic gonadotropin releasing ac- 

 tivity and pituitary gonadotropin levels. Several 

 investigators reported that prolactin has a 

 pronounced affect on lipid metabolism in teleost 

 fishes (Lee and Meier 1967; Meier 1969; Mehrle and 

 Fleming 1970; Joseph and Meier 1971; Meier et al. 

 1971; de Vlaming and Sage 1972; Sage and de 

 Vlaming 1973; de Vlaming et al. in press; Pardo 

 and de Vlaming in press). Furthermore, melatonin 

 treatment significantly reduces pituitary prolac- 

 tin activity in F. similis (de Vlaming, Sage, 

 Charlton, and Tiegs 1974). These authors suggest- 

 ed that the effects of melatonin on lipid me- 

 tabolism in this species may be due in part to the 

 effects of this indolamine on pituitary prolactin 

 release. Whether pinealectomy alters pituitary 

 prolactin secretion is not presently known. Inves- 

 tigations are presently in progress to examine this 

 possibility. Prolactin does stimulate lipid deple- 

 tion from in vitro liver preparations of 

 Notemigonus incubated at high temperatures and 

 promotes fat synthesis in liver preparations in- 

 cubated at low temperatures (Pardo and de Vlam- 

 ing in press). 



The effects of pinealectomy on lipid reserves in 

 Notemigonus may result from changes in 

 reproductive activity. This suggestion seems 

 rather unlikely since pinealectomy frequently 

 resulted in significant changes in body fat levels 

 without appreciably altering gonadal activity. 



The data presented here favor the view that the 

 pineal is a photoreceptor or integrates light infor- 

 mation and plays an important role in regulating 

 physiological processes in teleost fishes. 



FISHERY BULLETIN: VOL. 73, NO. 4 



ACKNOWLEDGMENTS 



I am grateful to J. Flanagan, M. J. Vodicnik and 

 R. J. Pardo for technical assistance. This work was 

 supported by NSF Grant GB-41338. 



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