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We describe seasonal changes in the physiology of reproductive organs of Saker Falcons electrocuted on an electricity power line in Mongolia. Macroscopic examination of the gonads revealed asymmetry in testes size, with bias to the left body side. This asymmetry declined with seasonal increase in testes size during the main egg-laying period of the breeding season. In females, 91% possessed both left and right ovaries (N = 161); there was no visible oviduct associated with the right ovary and it was smaller than the functional left ovary. Both ovaries showed seasonal development in size, becoming larger during the peak egg-laying period. Hierarchical preovulatory follicular development was recorded in two females, with ca. 5 mm difference in the diameter of sequential follicles. Both sexes developed brood patches during the main incubation period, with adults more likely to exhibit brood patches than juveniles. Among juveniles, at least 82% of females and 91% of males were non-breeders without brood patches. The high electrocution rate at our studied power line provided a rare opportunity to examine the non-breeding component of the Saker population. Juveniles predominated in the non-breeding population during the main egg-laying period (89%, N = 65), with the proportion of adults electrocuted being significantly lower among females. Only a small proportion of juvenile females exhibited gonadal evidence of breeding, consistent with the low observed frequency of juvenile breeders at nests. The demographic composition of the non-breeding population is consistent with female mortality rates exceeding that of males, and potentially indicates incipient population decline. [ABSTRACT FROM AUTHOR]

The aim of the study was to examine seasonal variations in the estradiol-17β (E 2 ) and testosterone (T) levels in the gonad of Mytilus coruscus in relation to the reproductive cycle. M. coruscus individuals were obtained from March 2012 to February 2013 and gonadal tissue was studied by histological analysis and transmission electron microscopy. Histological data revealed that gametogenesis occurs from autumn to winter (i.e., from September to January) when the water temperature is lower than the rest of the year, and spawning occurs in spring (i.e., March onwards). In this study, we used enzyme-linked immunosorbent assay (ELISA) to measure the estradiol (E 2 ) and testosterone (T) concentrations in Mytilus coruscus . The E 2 level ranged from 109.59 to 412.31 pg/g wet weight and from 81.45 to 356.05 pg/g wet weight throughout the year. Furthermore, there was a positive correlation between the E 2 level and mean oocyte diameter during the study period, indicating that E 2 plays a role in sexual maturation in M. coruscus females and males. Thus, E 2 and T may be endogenous modulators in sex determination and in the development and maturation of M. coruscus . [ABSTRACT FROM AUTHOR]

Abstract: In the present study, tyrosine hydroxylase (TH, the rate-limiting enzyme in catecholamine synthesis) activity was demonstrated in the ovary of the catfish to elucidate the possible physiological role of catecholamines in the gonad. The ovary is innervated by seven pairs of nerves, originating from the paired sympathetic chain lying dorsal to the posterior kidney. Ovarian TH activity showed a significant annual variation (P <0.001, one-way ANOVA), correlating with gonado-somatic index. Activity was low from December to February (resting phase), increased from March to July (recrudescent phase) and then decreased in post-spawning phase (August–November). The annual pattern was similar to that of the brain. An intraperitoneal injection of 100IU hCG/fish induced significant periovulatory changes in TH activity with the peak rise at 16h, and the activity decreased after egg-stripping (P <0.001, one-way ANOVA). Brain TH activity showed similar periovulatory changes. The results suggest that catecholamine synthesis is increased during both ovarian recrudescence and spawning of the annual reproductive cycle, implying a functional role in ovarian growth, maturation and ovulation. [Copyright &y& Elsevier]