Seasonal Fluctuations in Pituitary Gland and Plasma Levels of Gonadotropic Hormones inRana

Kim, Jung Won; Im, Wook‐Bin; Choi, Han H.; Ishii, Susumu; Kwon, Ho

doi:10.1006/gcen.1997.6992

Cited by 35 publications

(18 citation statements)

References 18 publications

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“…LH, luteinizing hormone and FSH, follicle-stimulating hormone), which affect both amplexing behavior and muscle morphology (Itoh and Ishii, 1990). In Rana esculenta, amplexing males exhibit higher levels of testosterone and lower levels of estradiol than non-amplexing individuals (Gobbetti and Zerani, 1999), and in Rana pipiens testosterone increases forelimb muscle dry mass by more than 150% under experimental conditions (Kim et al, 1998). Testosterone treatment of castrated male Xenopus laevis frogs leads to increases in muscle size, force and twitch relaxation times in flexor carpi radialis, yet this treatment has little effect on the Mating success of individual male frogs within explosive breeding species can depend on their ability to compete for a mate and to hold onto that mate during amplexus.…”

Section: Introductionmentioning

confidence: 99%

Sexual dimorphism of extensor carpi radialis muscle size, isometric force, relaxation rate and stamina during the breeding season of the frogRana temporariaLinnaeus 1758

Navas

James

2007

Journal of Experimental Biology

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and length were greater (tenfold and 1.4-fold, respectively), absolute tetanic muscle force and relative tetanic force (stress) were greater (16-fold and 2.2-fold, respectively) and relaxation times were slower in males than in females. Male ECR muscles incompletely relaxed during fatigue tests and showed less fatigue than female muscles. These sex differences are likely to be beneficial to the male frogs in allowing them to produce relatively high absolute muscle forces for prolonged periods of time to hold onto their mate during amplexus.

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Section: Introductionmentioning

confidence: 99%

Sexual dimorphism of extensor carpi radialis muscle size, isometric force, relaxation rate and stamina during the breeding season of the frogRana temporariaLinnaeus 1758

Navas

James

2007

Journal of Experimental Biology

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“…The present observations indicate the elevation in testicular androgen synthesis by increasing the environmental temperature even during hibernation. Both plasma FSH and LH are the key regulating hormones for activities of Δ 5 , 3β‐HSD and 17β‐HSD in toads [Biswas, 1969; Canosa et al, 2002, 2003; Kim et al, 1998]. This experiment demonstrates that the gonadotrophin secretion in this group of animals is temperature dependent and is independent of the breeding cycle.…”

Section: Discussionmentioning

confidence: 79%

“…During winter (December–January), their reproductive activity is remarkably reduced and they enter into hibernation [Mondal and Basu, 1960; Saxena and Lal, 1981]. Most of the reports indicate that the hibernating cycle is an endogenous type and the reproductive cycle synchronizes with hibernation [Jansky et al, 1980; Kim et al, 1998; Tanaka et al, 2004]. In contrast, the reproductive activities of hamster and ground squirrel decrease during hibernation and are controlled by environmental temperature [Reiter, 1975; Heller and Poulson, 1990; Saidapur, 1989].…”

Section: Introductionmentioning

confidence: 99%

Effect of an increase in environmental temperature on testicular androgenesis and spermatogenesis in toad (Bufo melanostictus) during hibernating season

Mondal¹,

Debnath

Ghosh

2010

Zoo Biology

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Activities of key testicular androgenic enzymes [Δ(5), 3β-hydroxysteroid dehydrogenase (Δ(5), 3β-HSD) and 17β-hydroxysteroid dehydrogenase (17β-HSD)], plasma levels of testosterone, and testicular gametogenic activities were studied in heat-exposed adult male toads during hibernating season for two consecutive years. Exposure of toads to an elevated environmental temperature for 14 and 21 days resulted in significant elevation of testicular Δ(5), 3β-HSD and 17β-HSD activities, along with plasma levels of testosterone. Testicular gametogenic activity, by means of quantity of all stages of spermatogenic cycle, were elevated significantly at the same experimental schedule, but 7 days of heat exposure resulted in significant elevation only in stage IV. The results indicated that environmental temperature is an important modulator of breeding activities of male toads. It also demonstrated that testicular activities in seasonally breeding toads are probably not linked to hibernating cycle.

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“…High temperatures can inhibit oogenesis, and a period of low temperatures (hibernation) may be required for ovulation (Kim et al 1998). Jørgensen (1975Jørgensen ( , 1982 has shown that high feed levels increase recruitment of FGP oocytes to SGP vitellogenic oocytes before and after hibernation.…”

Section: Amphibian Endocrine Systemmentioning

confidence: 99%

Reproduction and Larval Rearing of Amphibians

Browne¹,

Zippel²

2007

ILAR Journal

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Reproduction technologies for amphibians are increasingly used for the in vitro treatment of ovulation, spermiation, oocytes, eggs, sperm, and larvae. Recent advances in these reproduction technologies have been driven by (1) difficulties with achieving reliable reproduction of threatened species in captive breeding programs, (2) the need for the efficient reproduction of laboratory model species, and (3) the cost of maintaining increasing numbers of amphibian gene lines for both research and conservation. Many amphibians are particularly well suited to the use of reproduction technologies due to external fertilization and development. However, due to limitations in our knowledge of reproductive mechanisms, it is still necessary to reproduce many species in captivity by the simulation of natural reproductive cues. Recent advances in reproduction technologies for amphibians include improved hormonal induction of oocytes and sperm, storage of sperm and oocytes, artificial fertilization, and high-density rearing of larvae to metamorphosis. The storage of sperm in particular can both increase the security and reduce the cost of maintaining genetic diversity. It is possible to cryopreserve sperm for millennia, or store it unfrozen for weeks in refrigerators. The storage of sperm can enable multiple parentages of individual females' clutches of eggs and reduce the need to transport animals. Cryopreserved sperm can maintain the gene pool indefinitely, reduce the optimum number of males in captive breeding programs, and usher in new generations of Xenopus spp. germ lines for research. Improved in vitro fertilization using genetic diversity from stored sperm means that investigators need the oocytes from only a few females to produce genetically diverse progeny. In both research and captive breeding programs, it is necessary to provide suitable conditions for the rearing of large numbers of a diverse range of species. Compared with traditional systems, the raising of larvae at high densities has the potential to produce these large numbers of larvae in smaller spaces and to reduce costs.

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Seasonal Fluctuations in Pituitary Gland and Plasma Levels of Gonadotropic Hormones inRana

Cited by 35 publications

References 18 publications

Sexual dimorphism of extensor carpi radialis muscle size, isometric force, relaxation rate and stamina during the breeding season of the frogRana temporariaLinnaeus 1758

Sexual dimorphism of extensor carpi radialis muscle size, isometric force, relaxation rate and stamina during the breeding season of the frogRana temporariaLinnaeus 1758

Effect of an increase in environmental temperature on testicular androgenesis and spermatogenesis in toad (Bufo melanostictus) during hibernating season

Reproduction and Larval Rearing of Amphibians

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