caa a22 4500 477116000 CHVBK 20180405111622.0 cr unu---uuuuu 170330e19960301xx s 000 0 eng 10.1007/BF00003096 doi (NATIONALLICENCE)springer-10.1007/BF00003096 Effects of photoperiod and temperature on sexual recrudescence in the male weakfish, Cynoscion regalis [Elektronische Daten] [Martin Connaughton, Malcolm Taylor] Synopsis: Male weakfish,Cynoscion regalis, were collected in the south-west portion of Delaware Bay from April through August of 1992. Histological examination of testes collected from these specimens was used as a baseline for comparison with laboratory data. Weakfish testes were found to be of the unrestricted, continuous spermatogenic type and spermatogenesis was apparently prenuptial. The effects of photoperiod and temperature on gonadal maturation were studied in the laboratory using fish collected in June and July 1991. These fish were exposed to two months of simulated winter conditions prior to assignment to one of four experimental photoperiod/temperature regimes. The treatments included combinations of long day (LD,15 h light) or short day (SD, 9 h light) and high (HT, 20° C) or low (LT, 13° C) water temperatures. The four treatment groups were LD/HT, LD/LT, SD/HT, SD/LT. The LD/HT group was the only one to mature fully, expressing increased plasma androgen levels, increased gonadosomatic index (GSI) and advanced spermatogenesis, as well as hypertrophy of the sonic muscles, a seasonally expressed secondary sexual characteristic of male weakfish. High temperatures promoted the later stages of spermatogenesis, which were apparently inhibited by low temperatures. The presence of an endogenous annual cycle is suggested by the partial maturation of the testes and sonic muscles in all treatment groups, regardless of photoperiod/temperature regime. Kluwer Academic Publishers, 1996 Sonic muscles nationallicence Testosterone nationallicence 11-ketotestosterone nationallicence Spermatogenesis nationallicence Sciaenidae nationallicence Connaughton Martin College of Marine Studies and School of Life and Health Sciences, University of Delaware, 19717, Newark, DE, U.S.A. aut Taylor Malcolm College of Marine Studies and School of Life and Health Sciences, University of Delaware, 19717, Newark, DE, U.S.A. aut Environmental Biology of Fishes Kluwer Academic Publishers 45/3(1996-03-01), 273-281 0378-1909 45:3<273 1996 45 10641 https://doi.org/10.1007/BF00003096 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00003096 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Connaughton Martin College of Marine Studies and School of Life and Health Sciences, University of Delaware, 19717, Newark, DE, U.S.A aut NATIONALLICENCE 700 1- Taylor Malcolm College of Marine Studies and School of Life and Health Sciences, University of Delaware, 19717, Newark, DE, U.S.A aut NATIONALLICENCE 773 0- Environmental Biology of Fishes Kluwer Academic Publishers 45/3(1996-03-01), 273-281 0378-1909 45:3<273 1996 45 10641 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer