SOME EXPERIMENTS ON THE RELATION OF THE EXTERNAL ENVIRONMENT TO THE SPERMATOGENETIC CYCLE OF FUNDULUS HETEROCLITUS (L.)

Abstract

No differences in the velocity of the spermatogenetic cycle were found between control and exptl. fish subject to the following photoperiodic manipulations provided adequate nutrition was furnished and provided the water temp. (variable between 11[degree] and 18[degree] C) was the same for both groups. The photoperiodic manipulations were a) 21 days of decreased lighting between June 30 and July 22, b) 37 days of increased lighting between July 22 and Aug. 27 to fish previously treated as in (a), c) 68 days of increased lighting between Oct. 29 and Jan. 4. Sexually inactive fish which received no more than 1 1/2 hrs. of light per day rapidly formed when kept in water whose temp. ranged between 14[degree] and 20[degree] C. Fish similarly treated remained sexually inactive when kept in water of 6-10[degree] C. The temp. of the water is evidently the primary factor of the external environment that influences the spermatogenetic cycle. Light as light seems incapable of effecting this cycle.