Author
Robert Barnes
Bio: Robert Barnes is an academic researcher. The author has contributed to research in topics: Gonadotropin & Gonadotropin-releasing hormone. The author has an hindex of 3, co-authored 3 publications receiving 369 citations.
Papers
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TL;DR: In this article, a 5-year study was conducted on male and female bullfrogs in central California over a period of five years, and the results showed that levels of plasma gonadotropins and steroids are highly labile and particularly sensitive to the effects of captivity, especially in males.
301 citations
TL;DR: Two synthetic analogs of gonadotropin releasing hormone (Gn-RH), a potent agonist, (imBzld-His6, Pro9-NEt)-GnRH, and an antagonist (Ac-dehydro-Pro1, pCl-d-Phe2, d-Trp3,6)-Nα-MeLeu7-Gn RH, were demonstrated to possess actions in the bullfrog Rana catesbeiana similar to those exhibited in mammals as mentioned in this paper.
55 citations
TL;DR: In a recent study, this article found no evidence of a feedback effect of ovarian steroids on the pituitary responsiveness to acute gonadotropin-releasing hormone (GnRH stimulation in the frog as has been demonstrated in mammals.
14 citations
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TL;DR: This review examines the growing evidence that GC concentrations in free-living reptiles, amphibians, and birds, but not mammals, are commonly elevated during the breeding season and test three hypotheses with different focuses on GC's energetic or behavioral effects, as well as onGC's role in preparing the animal for subsequent stressors.
1,042 citations
TL;DR: It is suggested that several ecologically based ideas, such as variability in the length of the breeding season and lifetime reproductive opportunities, can be used to explain the utility of adrenocortical modulation in amphibian and reptilian species.
504 citations
TL;DR: There is probably not a single cause for global amphibian declines and the role of pathogens in inducing diseases that cause death is profoundly affected by four other ultimate factors: atmospheric change, environmental pollutants, habitat modification and invasive species.
Abstract: Greater than 70% of the world's amphibian species are in decline. We propose that there is probably not a single cause for global amphibian declines and present a three-tiered hierarchical approach that addresses interactions among and between ultimate and proximate factors that contribute to amphibian declines. There are two immediate (proximate) causes of amphibian declines: death and decreased recruitment (reproductive failure). Although much attention has focused on death, few studies have addressed factors that contribute to declines as a result of failed recruitment. Further, a great deal of attention has focused on the role of pathogens in inducing diseases that cause death, but we suggest that pathogen success is profoundly affected by four other ultimate factors: atmospheric change, environmental pollutants, habitat modification and invasive species. Environmental pollutants arise as likely important factors in amphibian declines because they have realized potential to affect recruitment. Further, many studies have documented immunosuppressive effects of pesticides, suggesting a role for environmental contaminants in increased pathogen virulence and disease rates. Increased attention to recruitment and ultimate factors that interact with pathogens is important in addressing this global crisis.
361 citations
TL;DR: Stress reduces the quality of gametes produced by rainbow trout, and exposure of rainbow trout to repeated acute stress during reproductive development resulted in a significant delay in ovulation and reduced egg size in females, significantly lower sperm counts in males, and, perhaps most importantly, significantlyLower survival rates for progeny from stressed fish compared to progenyFrom unstressed control fish.
Abstract: In this study we have used the rainbow trout as a model animal to study the biological consequences of stress in terms of gamete quality and quantity. Groups of 30 mature male and female rainbow trout were subjected to repeated acute stress during the 9 mo prior to spawning. Time of ovulation, fecundity, and egg size were recorded in mature females, and sperm counts were carried out on the milt from the male fish, from both the stressed and control groups. Eggs from ovulated females were fertilized with milt from males subjected to the same treatment regime. Approximately 300 eggs from each female were fertilized with a sperm dilution of 10-3 in diluent. Subsequent development of the fertilized eggs was then monitored. There were no differences in somatic weight or length between the two groups at the end of the experiment, but exposure of rainbow trout to repeated acute stress during reproductive development resulted in a significant delay in ovulation and reduced egg size in females, significantly lower sperm counts in males, and, perhaps most importantly, significantly lower survival rates for progeny from stressed fish compared to progeny from unstressed control fish. Hence, stress reduces the quality of gametes produced by rainbow trout.
351 citations
TL;DR: A link between a classical neuroh hormonal stress pathway (involving corticotropin-releasing hormone, CRH) and the developmental response to habitat desiccation is demonstrated and support a central role for CRH as a neurohormonal transducer of environmental stimuli into the endocrine response which modulates the rate of metamorphosis.
334 citations