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Full-Text Articles in Life Sciences
Aspects Of The Reproductive Biology And Growth Of The Mississippi Silvery Minnow, Hybognathus Nuchalis (Agassiz, 1855) (Teleostei: Cyprinidae) From The Pearl River, Louisiana., Arely Ramírez-García, Kyle R. Piller
Aspects Of The Reproductive Biology And Growth Of The Mississippi Silvery Minnow, Hybognathus Nuchalis (Agassiz, 1855) (Teleostei: Cyprinidae) From The Pearl River, Louisiana., Arely Ramírez-García, Kyle R. Piller
Southeastern Fishes Council Proceedings
The reproductive biology and growth of the Mississippi Silvery Minnow, Hybognathus nuchalis, is described from multiple sites in the Pearl River, Louisiana. Individuals were collected from August 2011 to August 2012. Ovarian weights, expressed as a percentage of body weights, peaked in December. Size structure ranged from 29.0 to 60.0 mm SL for females and 25.0 to 56.0 mm SL for males. Mature ova were found from November to January. Females reached first maturity (L50) at 37.0 mm SL and L50 for males is at 41.0 mm SL. Sex ratio (females:males) is biased towards females (X2= 18.57 p …
Predators Modify The Temperature Dependence Of Life-History Trade-Offs, Thomas M. Luhring, Janna M. Vavra, Clayton E. Cressler, John Delong
Predators Modify The Temperature Dependence Of Life-History Trade-Offs, Thomas M. Luhring, Janna M. Vavra, Clayton E. Cressler, John Delong
School of Biological Sciences: Faculty Publications
Although life histories are shaped by temperature and predation, their joint influence on the interdependence of life-history traits is poorly understood. Shifts in one life-history trait often necessitate shifts in another—structured in some cases by trade-offs— leading to differing life-history strategies among environments. The offspring size–number trade-off connects three traits whereby a constant reproductive allocation (R) constrains how the number (O) and size (S) of offspring change. Increasing temperature and size-independent predation decrease size at and time to reproduction which can lower R through reduced time for resource accrual or size-constrained fecundity. We investigated how O, S, and R in …
Do Seasonal Glucocorticoid Changes Depend On Reproductive Investment? A Comparative Approach In Birds, S. Casagrande, L. Z. Garamszegi, W. Goymann, Jeremy W. Donald, C. D. Francis, M. J. Fuxjager, Jerry F. Husak, Michele A. Johnson, Bonnie K. Kircher, R. Knapp, L. B. Martin, E. T. Miller, L. A. Schoenle, Maren N. Vitousek, T. D. Williams, M. Hau
Do Seasonal Glucocorticoid Changes Depend On Reproductive Investment? A Comparative Approach In Birds, S. Casagrande, L. Z. Garamszegi, W. Goymann, Jeremy W. Donald, C. D. Francis, M. J. Fuxjager, Jerry F. Husak, Michele A. Johnson, Bonnie K. Kircher, R. Knapp, L. B. Martin, E. T. Miller, L. A. Schoenle, Maren N. Vitousek, T. D. Williams, M. Hau
Biology Faculty Research
Animals go through different life history stages such as reproduction, moult, or migration, of which some are more energy-demanding than others. Baseline concentrations of glucocorticoid hormones increase during moderate, predictable challenges and thus are expected to be higher when seasonal energy demands increase, such as during reproduction. By contrast, stress-induced glucocorticoids prioritize a survival mode that includes reproductive inhibition. Thus, many species down-regulate stress-induced glucocorticoid concentrations during the breeding season. Interspecific variation in glucocorticoid levels during reproduction has been successfully mapped onto reproductive investment, with species investing strongly in current reproduction (fast pace of life) showing higher baseline and lower …
Reproductive Correlates Of A Perineal Gland In The Hispid Cotton Rat, Robert K. Rose, Julie A. Winchell
Reproductive Correlates Of A Perineal Gland In The Hispid Cotton Rat, Robert K. Rose, Julie A. Winchell
Virginia Journal of Science
During studies of the annual cycle of reproduction in the hispid cotton rat (Sigmodon hispidus) in southeastern Virginia, we discovered an anal (more specifically, perineal) gland that is present only in males during the breeding season. The perineal gland encircles the lower end of the rectum and has ductal connections to the urethra, through which its secretions likely are delivered. This fatty gland is highly developed in breeding males but, like the testes and seminal vesicles, regresses during the winter non-breeding season. The prominence and cyclicity of the perineal gland suggests that it somehow facilitates normal reproduction. The …