摘要:

AbstractWe estimated age at attainment of sexual maturity and examined reproductive seasonality for male spotted dolphins,Stenella attenuata, from the eastern tropical Pacific Ocean. Maturity was determined by histological examination of testes. Average age at sexual maturation was 14.7 yr (the mean of two readers' age estimates). Testis and epididymis weight and seminiferous tubule diameters were reliable indicators of maturity, whereas age, length and color phase were less reliable. Seasonality was determined by changes in testis and epididymis weight, relative quantity of spermatids and spermatozoa, and lumen diameter, as well as an index of testis development (weight of the right testis and epididymis divided by length of the right testis). Testis and epididymis weights and index values peaked in July and August, midway between two predicted mating seasons for the northern offshore stock, but spermatozoa levels were elevated during the predicted breeding seasons.

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00016.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractFetal and maternal heart rates were studied in unrestrained, pregnant harbor seals during the last third of gestation. Heart rates were recorded while the mothers were resting on land or performing trained simulated dives of up to 2.25 min. Data from resting mothers showed the development of a bimodal or two‐speed fetal heart rate pattern during late gestation. The mean faster and slower fetal heart rates at term were 125 ± 3.7 and 79 ± 3.1 (mean + SEM) respectively. The amount of fetal bradycardia observed increased steadily towards term, and fetal heart rate changes were not correlated with changes in maternal heart rate or maternal respiration. The bimodal fetal heart rate was also seen during the simulated dives, and no decrease in either the faster or slower heart rate was found. Heart rates from resting, unrestrained harbor seal pups were also studied. The pups displayed a bimodal heart rate similar to the fetuses' with the slower rate occurring during breath‐holds. The bradycardia in the pups was equivalent to the slower fetal heart rate. These findings suggest that the regulatory mechanism that determines the apneic bradycardia in young harbor seals during non‐stressful conditions develops in the last quarter of ge

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00017.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractA total of 326 humpback whales(Megaptera novaeangliae)were individually identified in southeastern Alaska during five summer seasons (July to September) and four late seasons (November to February) spanning the years 1979 to 1983. Peak numbers of whales were found late in August or early in September. Whales arrived 1–2 wk later in 1982 than in 1981. Whales sighted in both the summer and late seasons of 1981 and 1982 remained about 3.7 mo and one whale remained for at least 4.9 mo. Humpback whales from southeastern Alaska wintered in Hawaiian or Mexican waters, but generally did not travel to other feeding regions. The most rapid migratory transit between Hawaii and southeastern Alaska was 79 d. Based on mark‐recapture analyses of the photographic data, we estimate a population of 270–372 whales in the southeastern Alaska feeding

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00018.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractIn view of the supposition that a dolphin can swim faster than would be predicted based on its physical features and presumed muscle power potential, studies were initiated to reevaluate the assumptions made in reaching these conclusions. Several previous studies have shown that the architectural and histochemical properties of a skeletal muscle dictate its force, velocity and displacement properties. This study examined the muscle fiber lengths and tendon arrangements of the dorsal and ventral axial muscles in dolphins (Tursiops truncatus). Fiber type and fiber size distributions were determined to reflect the general biochemical characteristics of the musculature. The dorsal muscles had a higher mean fiber length (167Vs.90 mm) and the range within and across different dorsal muscles was less (141–199vs.37–185 mm) than in the ventral muscles. Both the dorsal and ventral muscles consisted of an overall mean of 50 percent slow twitch and 50 percent fast twitch fiber types. The fast twitch fibers were 67 percent larger (2,200vs.1,317 μm2) than the slow twitch fibers in the ventral and 38 percent larger (1,213Vs.879 μm2) in the dorsal muscles. In addition, the mean cross sectional area of the fibers in the ventral muscles was approximately 65 percent greater (1,750vs.1,072 μm2) than those in the dorsal muscles. The shorter, larger‐diameter fibers of the ventral musculature give it a greater potential for force production for a given amount of muscle mass. In contrast, the dorsal muscles appear to be designed to optimize velocity and displacement, (i.e., longer fibers). These findings contribute to the information necessary for the determination of the power potential of the musculature of the

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00019.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00020.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00022.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Book reviews in this article:AntarcitcEcology. R. M. Laws (ed.).SealsOfTheWorld. J. E. King.ReproductionInWhales, Dolphins andPorpoises. W. F. Perrin, R. L. Brownell, Jr., and D. P. DeMaster, eds.EvolutionInTheGalapagosIslands. R. J. Berry (ed.).HistoricalWhalingRecords. M. F. Tillman and G. P. Donovan (eds.).Diving andAsphyxia, A ComparativeStudyOfAnimals andMan. R. Elsner and B. Gooden.

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00023.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY