El Niño Southern Oscillation (ENSO) linked climate has been known to be associated with several rodent species, but its effects on rodent community at both spatial and temporal scales are not well studied. In this study, we investigated the possible causal chain relating ENSO, precipitation, temperature, and vegetation index (normalized difference vegetation index, NDVI) to rodent abundance for 14 sympatric rodent species in 21 counties of semiarid grasslands in Inner Mongolia, China, from 1982 to 2006. We found that both precipitation and temperature showed a generally direct positive effect on rodent abundance in many species in the current year, but indirect effects that operate through NDVI in the current or following year could have a reverse effect on abundance. We described one ENSO-linked precipitation bottom-up chain and three ENSO-linked temperature bottom-up chains. These observed bottom-up links reveal that in El Niño years, or 1 year after La Niña years, or 2 years after El Niño years, ENSO-driven climate or vegetation factors tend to increase population abundances of many sympatric rodent species in this region. We also found time-lag effects and the life-history strategy (i.e., functional groups of hibernating behavior, activity rhythm, or food habits) also contribute to the observed complicated effects of SOI on precipitation, temperature, NDVI, and ultimately rodent abundance.

To assess the potential roles of sex steroids in modulating reproductive processes in the Zhikong scallop (Chlamys farreri (Jones and Preston, 1904)), variations in estradiol-17␤ (E2) and testosterone (T) levels in gonads were examined monthly from January to December 2012 by enzyme-linked immunosorbent assay (ELISA). The mean concentrations of E2 and T in gonads ranged from 75.07 to 666.24 pg/g and from 91.09 to 506.28 pg/g, respectively. Concentrations of E2 were significantly higher in ovaries than in testes, while T concentrations were higher in testes than in ovaries during gametogenesis. Concentrations of E2 in females and T in males increased with development and maturation of gonad, attained the highest value before spawning, and decreased rapidly after spawning. A positive correlation between E2 levels and oocyte diameters (r = 0.743, P < 0.05, n = 25) was observed, suggesting that E2 may play a role in oogenesis. These findings indicate that E2 and T, which are highly correlated with the reproductive cycle, may play an important role in sex determination, sex differentiation, gametogenesis, and spawning in C. farreri.Résumé : Afin d'évaluer les rôles possibles des stéroïdes sexuels dans la modulation des processus de reproduction chez le pétoncle farreri (Chlamys farreri (Jones et Preston, 1904)), les variations des concentrations d'estradiol-17␤ (E2) et de testostérone (T) dans les gonades ont été examinées mensuellement de janvier à décembre 2012 par l'analyse immunoenzymatique ELISA. Les concentrations moyennes d'E2 et de T dans les gonades allaient de 75,07 à 666,24 pg/g et de 91,09 à 506,28 pg/g, respectivement.Les concentrations d'E2 étaient significativement plus élevées dans les ovaires que dans les testicules, alors que les concentrations de T étaient plus élevées dans les testicules que dans les ovaires durant la gamétogénèse. Les concentrations d'E2 chez les femelles et de T chez les mâles augmentaient au fil du développement et de la maturation des gonades, atteignaient leurs maximums avant le frai et diminuaient rapidement par la suite. Une corrélation positive observée entre les concentrations d'E2 et le diamètre des oocytes (r = 0,743, P < 0,05, n = 25) donne à penser que l'E2 pourrait jouer un rôle dans l'ovogénèse. Ces résultats indiquent que l'E2 et la T, qui sont fortement corrélés au cycle de reproduction, pourraient jouer un rôle important dans la détermination du sexe, la différenciation sexuelle, la gamétogénèse et le frai chez C. farreri. [Traduit par la Rédaction]