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Geology topics

G. Gee

Publications and source records attributed to G. Gee.

6 recordsLinked to original sources
USGS2008

Osmotic tolerance of avian spermatozoa: Influence of time, temperature, cryoprotectant and membrane ion pump function on sperm viability

Potential factors influencing sperm survival under hypertonic conditions were evaluated in the Sandhill crane (Grus canadensis) and turkey (Meleagridis gallopavo). Sperm osmotolerance (300-3000 mOsm/kg) was evaluated after: (1) equilibration times of 2, 10, 45 and 60 min at 4 ?C versus 21 ?C; (2) pre-equilibrating with dimethylacetamide (DMA) or dimethylsulfoxide (Me2SO) at either 4 ?C or 21 ?C; and (3) inhibition of the Na+/K+ and the Na+/H+ antiporter membrane ionic pumps. Sperm viability was assessed using the eosin-nigrosin live/dead stain. Species-specific differences occurred in response to hypertonic conditions with crane sperm remaining viable under extreme hypertonicity (3000 mOsm/kg), whereas turkey sperm viability was compromised with only slightly hypertonic (500 mOsm/kg) conditions. The timing of spermolysis under hypertonic conditions was also species-specific, with a shorter interval for turkey (2 min) than crane (10 min) sperm. Turkey sperm osmotolerance was slightly improved by lowering the incubation temperature from 21 to 4 ?C. Pre-equilibrating sperm with DMA reduced the incidence of hypertonic spermolysis only in the crane, at both room and refrigeration temperature. Inhibiting the Na+/K+ and the Na+/H+ antiporter membrane ion pumps did not impair resistance of crane and turkey spermatozoa to hypertonic stress; pump inhibition actually increased turkey sperm survival compared to control sperm. Results demonstrate marked species specificity in osmotolerance between crane and turkey sperm, as well as in the way temperature and time of exposure affect sperm survival under hypertonic conditions. Differences are independent of the role of osmotic pumps in these species.

Cryobiology↗
USGS2000

Species variation in osmotic, cryoprotectant, and cooling rate tolerance in poultry, eagle, and Peregrine Falcon spermatozoa

Potential factors influencing spermatozoa survival to cryopreservation and thawing were analyzed across a range of the following avian species: domestic chicken ( Gallus domesticus ), domestic turkey ( Meleagris gallopavo ), golden eagle ( Aquila chrysaetos ), Bonelli’s eagle ( Hieraaetus fasciatus ), imperial eagle ( Aquila adalberti ), and peregrine falcon ( Falco peregrinus ). Studies focused on spermatozoa tolerance to the following: 1) osmotic stress, 2) different extracellular concentrations of the cryoprotectant dimethylacetamide (DMA), 3) equilibration times of 1 versus 4 h, 4) equilibration temperature of 4 versus 21°C, and 5) rapid versus slow cooling before cryopreservation and standard thawing. Sperm viability was assessed with the live/dead stain (SYBR-14/propidium iodine). Sperm viability at osmolalities ≥800 mOsm was higher ( P < 0.05) in raptor than poultry semen. Return to isotonicity after exposure to hypertonicity (3000 mOsm) decreased ( P < 0.05) number of viable spermatozoa in chicken, turkey, and golden and Bonelli’s eagle spermatozoa but not in imperial eagle or peregrine falcon spermatozoa. Differences were found in spermatozoa resistance to hypotonic conditions, with eagle species demonstrating the most tolerance. Semen, equilibrated for 1 h (4°C) in diluent containing DMA (≥2.06 M), experienced decreased ( P < 0.05) spermatozoa survival in all species, except the golden eagle and peregrine falcon. Number of surviving spermatozoa diminished progressively with increasing DMA concentrations in all species. Increased equilibration temperature (from 4 to 21°C) markedly reduced ( P < 0.05) spermatozoa survival in all species except the Bonelli’s eagle and turkey. Rapid cooling was detrimental ( P < 0.05) to spermatozoa from all species except the imperial eagle and the chicken. These results demonstrate that avian spermatozoa differ remarkably in response to osmotic changes, DMA concentrations, equilibration time, temperature, and survival after fast or slow freezing. These differences emphasize the need for species-specific studies in the development and enhancement of assisted breeding for poultry and endangered species.

Biology of Reproduction↗
USGS2000

The status of masked bobwhite recovery in the United States and Mexico

The masked bobwhite (Colinus virginianus ridgwayi) is an endangered species currently numbering < 1500 individuals and restricted to 2 locales in southeastern Arizona and northcentral Sonora, Mexico. The subspecies' endangered status is attributed to overgrazing of Sonora savanna grassland that began during the late 1880's and continued well into the 20th century. This overgrazing resulted in the conversion of many native grass pastures to the exotic bufflegrass (Cenchrus ciliaris). The Arizona masked bobwhite population was extirpated around the turn of the century, and the Sonoran population was thought to have disappeared during the 1940's until a small remnant population was discovered on a ranch near Benjamin Hill, Sonora, in 1964. Masked bobwhite recovery efforts have a dynamic, long history of nearly six decades. Current masked bobwhite recovery efforts focus on reestablishing a self-sustainlng population on the Buenos Aires National Wildlife Refuge (BANWR) in the United States, as well as 2 remnant wild populations located on privately owned ranches in northcentral Sonora.

Book chapter↗
USGS2000

Releasing captive-reared masked bobwhite for population recovery: A review

Efforts to re-establish the endangered masked bobwhite (Colinus virginianus ridgwayi) to it's former southern Arizona range have been ongoing since establishment of the Buenos Aires National Wildlife Refuge in 1986. Pre-release conditioning techniques developed prior to Refuge establishment continued to be utilized in an effort to improve post-release survival of captive-reared masked bobwhite chicks. Foremost among these techniques was the use of wild Texas bobwhite (C. v. texanus) males as foster parents which were paired with all broods released on the Refuge. The efficacy of this technique was evaluated using radio telemetry in 1994, and the results indicated that the use of foster Texas males was not as effective as had been presumed because post-release chick survival was poor. Therefore, in 1995 pre-release conditioning protocol were modified in an effort to improve post-release survival. The primary intent of these modifications was to emphasize wild behavior among chicks prior to release. Modifications to established protocol included imprinting chicks to adult bobwhites immediately after eggs hatched and exposing 1-to-2 day old chicks to natural foods (insects and seeds) while they were in brooder units. Foster parents and their respective broods were then placed in flight pens that mimicked the natural conditions that would confront broods upon release. Family groups were held in flight pens for several weeks for acclimatization purposes and then transported to temporary enclosures erected at release sites where they were held for a week and then released. Finally all releases were conducted during fall after covey formation was apparent to ensure that foster parents and released chicks remained with a group of birds. Preliminary results indicated that post-release chick survival was higher than what was observed in 1994. Pre-conditioning research will continue in an effort to further quantify post-release survival of masked bobwhite chicks. Although the results of this research project are preliminary, it is possible that pre-release conditioning techniques developed for masked bobwhites will prove useful to quail reestablishment efforts throughout North America.

Book chapter↗
USGS1992

Karyotype and identification of sex in two endangered crane species

A laboratory procedure for sex identification of monomorphic birds was developed using modern cytological methods of detecting chromosome abnormalities in human amniotic fluid samples. A pin feather is taken from a pre-fledging bird for tissue culture and karyotype analysis. Through this method, the sex was identified and the karyotype described of the whooping crane (Grus americana) and the Mississippi sandhill crane (G. canadensis pulla). Giemsa-stained karyotypes of these species showed an identical chromosome constitution with 2n = 78 + 2. However, differences in the amount of centromeric heterochromatin were observed in the Mississippi sandhill crane when compared to the whooping crane C-banded karyotype.

Book chapter↗