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Full-Text Articles in Life Sciences
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 …
The Population Dynamics Of Two Rodents In Two Coastal Marshes In Virginia, Robert K. Rose, John A. March
The Population Dynamics Of Two Rodents In Two Coastal Marshes In Virginia, Robert K. Rose, John A. March
Virginia Journal of Science
The communities of small mammals were evaluated for 13 months with capture-mark-recapture methods in two Spartina-Juncus marshes of the Atlantic coast in Northampton County, Virginia. Small mammals were trapped for three days each month using live traps placed on floats on two study grids. Two rodents were numerically dominant (~90% of small mammals) there: marsh rice rat, Oryzomys palustris, and meadow vole, Microtus pennsylvanicus. Monthly estimates of population density were greater for rice rats (peak: 45/ha) than for those of meadow voles (peak: 30/ha). Survival rates were generally low, especially for rice rats, indicating highly vagile populations. Both …
Reproduction Of Black Drum, Pogonias Cromis, From The Chesapeake Bay Region, Brian K. Wells, Cynthia M. Jones
Reproduction Of Black Drum, Pogonias Cromis, From The Chesapeake Bay Region, Brian K. Wells, Cynthia M. Jones
Virginia Journal of Science
Ovaries of black drum, Pogonias cromis, collected from the Chesapeake Bay region in 1992, were used to describe reproductive strategy and fecundity. Histological examination showed that black drum spawn in the Chesapeake Bay region from April through early June. Distributions of oocyte diameter showed distinct oocyte-developmental groups indicating that Chesapeake Bay black drum are group-synchronous batch spawners. Female black drum are extremely fecund ranging from 414,000 to 3,736,000 hydrated oocytes (mean = 1,389,000) per batch with a spawning periodicity of 3.8 days. Estimates of spawning strategy, spawning periodicity, and batch fecundity for black drum from the Chesapeake Bay region …
Reproductive Differences Among Delmarva Grass Shrimp (Palaemonetes Pugio And P. Vulgaris) Populations, Holly H. Ganz, Robert E. Knowlton
Reproductive Differences Among Delmarva Grass Shrimp (Palaemonetes Pugio And P. Vulgaris) Populations, Holly H. Ganz, Robert E. Knowlton
Virginia Journal of Science
Populations of female grass shrimps (Palaemonetes pugio and P. vulgaris) were sampled from five coastal embayments in Delaware, Maryland, and Virginia (Delmarva) and compared with respect to reproductive and life history attributes. We observed interspecific differences in timing of reproduction, carapace length, ratio of carapace length to total body length, body weight, clutch weight, clutch size, and egg volume. Onset of reproduction in P. vulgaris lagged behind P. pugio. Although there was no difference in the relationship between clutch size and carapace length for the two species, carapace length/total body length in P. pugio was greater than …