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51.
DELAYED COSTS OF AN INDUCED DEFENSE IN TADPOLES? MORPHOLOGY,HOPPING, AND DEVELOPMENT RATE AT METAMORPHOSIS 总被引:5,自引:0,他引:5
Models for the evolution of plasticity predict that individuals having phenotypes induced by exposure to enemies should experience relatively low fitness when enemies are absent. However, costs of induced phenotypes have been difficult to find in both plants and animals, perhaps because costs are expressed at later stages in the life cycle. We searched for delayed costs of an induced defense in larvae of the water frog Rana ridibunda, which exhibits strong phenotypic responses to predators. Tadpoles grew to metamorphosis in outdoor artificial ponds, in either the presence or absence of Aeshna dragonfly larvae confined within cages. We collected metamorphs at forelimb emergence, estimated their development rate until tail resorption was complete, and measured their body and leg shape and hopping performance. Development rate through metamorphosis reflects the duration of a transitional period during which metamorphs are especially vulnerable to predators, and hopping performance may reflect ability to escape predators. Froglets from the dragonfly treatment lost mass through metamorphosis significantly faster than those from predator-free ponds, but they resorbed their tails at about the same rate, despite the fact that their tails were relatively large to begin with. Froglets developing from predator-induced tadpoles had shorter, more muscular legs, and hopped 5% longer distances (difference not significant). Therefore, producing an induced defense against insect predators during the tadpole stage did not exact a cost during or immediately after metamorphosis; if anything, tadpoles with the predator-induced phenotype gave rise to more vigorous froglets. These results focus attention on other costs of the induced phenotype, as well as alternative explanations for plasticity that do not rely on direct fitness trade-offs. 相似文献
52.
This study tested whether low genetic diversity in remnant populations of a declining amphibian is best explained by recent bottlenecks or by a history of being peripheral. We compared diversity from eight microsatellite loci in historical and extant populations from the interior and former periphery of the species' range. We found that historic peripheral populations already had reduced levels of genetic variation before the range contraction. Therefore, low diversity in remnants could not be ascribed to recent range contractions. This study shows that a common conservation strategy for rescuing genetically depauperate populations, artificial gene flow, may often be unwarranted and detrimental to evolutionarily important peripheral populations. 相似文献
53.
Genetic diversity across a vertebrate species' range: a test of the central-peripheral hypothesis 总被引:1,自引:0,他引:1
Although it has been long presumed that population genetic variability should decrease as a species' range margin is approached, results of empirical investigations remain ambiguous. Sampling strategies employed by many of these studies have not adequately sampled the entire range. Here we present the results of an investigation of population genetic diversity in a vertebrate species, the Italian agile frog, Rana latastei, sampled comprehensively across its entire range. Our results show that genetic variability is not correlated with population location with respect to the range periphery. Instead, the model that best explains the genetic variation detectable across the range is based on an east-to-west gradient of declining diversity. Although we cannot state definitively what has led to this distribution, the most likely explanation is that the range of Rana latastei expanded postglacially from a Balkan refugium. 相似文献
54.
Longevity and age at sexual maturity in an Italian population ofRana latastei were studied by skeletochronology performed on the phalanges. Frogs collected in 1998 and 1999 by drift fences and pitfall
traps were marked by toe-clipping. After marking, individuals were released and the cut phalanges were processed for skeletochronological
analysis. The maximum age so far recorded was 3 years in males and 4 years in females. The smallest male and female that were
sexually mature on the basis of histological analysis of the gonads were 36 and 35 mm snout vent length (SVL), respectively.
In both sexes, most individuals were estimated to breed shortly after emergence from their first overwintering. Among the
European Brown Frogs,Rana latastei appears to be one of the shortest-lived and one of the first to reach sexual maturity. 相似文献
55.
Di Berardino MA McKinnell RG Wolf DP 《Differentiation; research in biological diversity》2003,71(7):398-401
May 2002 marked the golden anniversary of the first cloned tadpoles. We celebrate this anniversary, as nuclear transplantation of frog cells into enucleated eggs became the prototype for cloning insects, fish, and mammals. We briefly review the salient results from amphibian cloning. Extension of these studies to mammalian species led to cloning adult cells, important advances in understanding nuclear reprogramming, and the construction of transgenic clones for biomedical applications. In addition, murine cloning clarified two problems unresolved in frog cloning: the unequivocal demonstration that nuclei of fully differentiated cells can direct the formation of fertile adults, and that abnormal expression of genes was responsible for the endoderm and neural syndromes in Rana clones. 相似文献
56.
In freeze tolerant wood frog Rana sylvatica, the freeze-induced liberation of glucose plays a critical role in survival in response to sub-zero temperature exposure. We have shown that the glycaemic response is linked to selective changes in the expression of hepatic adrenergic receptors through which catecholamines act to produce their hepatic glycogenolytic effects. The purpose of the present study was to determine if skeletal muscle, another catecholamine-sensitive tissue with glycogenolytic potential, displayed similar or different changes. In order to achieve these objectives, skeletal muscle derived from Rana sylvatica was studied in control, frozen and thawed states. In isolated sarcolemmal fractions, freezing effected an 88% decrease in beta(2)-adrenergic receptor expression but was without effect on the calcium pump; while thawing resulted in a recovery of the beta(2)-adrenergic receptor to 60% of control levels and a 2.4-fold increase in calcium transport. In isolated sarcoplasmic reticular fractions, freezing effected a 52% decrease in calcium binding and a 92% decrease in oxalate-stimulated calcium uptake; while thawing elicited partial normalization to control levels to 70% with respect to calcium binding and to 47% with respect to calcium uptake. Freezing and thawing were associated with increases and decreases, receptively, in blood glucose levels but were without effect on skeletal muscle glycogen content. Thus these muscle changes in Rana sylvatica in freezing and thawing are not linked to glycogen breakdown, are different from those previously seen in liver, and may provide a role in recovery of muscle function during thawing by protecting glycogen stores for contraction and maximizing extracellular calcium for excitation-contraction coupling in the frozen state. The involvement of thyroid hormone in triggering these muscle changes is discussed. 相似文献
57.
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59.
Anssi Laurila 《Freshwater Biology》2000,43(2):161-174
- 1 I examined the competitive ability of larval common frogs (Rana temporaria) and common toads (Bufo bufo) in a laboratory experiment by manipulating the number and size of Rana and the number of Bufo.
- 2 Bufo was the most active tadpole type, whereas small Rana was more active than large Rana.
- 3 Especially at high food availability, the growth rate of large Rana at metamorphosis was reduced in the presence of small Rana, whereas that of small Rana was not affected by larger conspecifics.
- 4 Both size classes of Rana were negatively affected by the presence of Bufo. Size at metamorphosis of Bufo was greater when large Rana was present. These results suggest that activity level is important in determining competitive ability.
- 5 To study competition in the field, tadpoles of Bufo were introduced to small rock‐pools that did not support Bufo naturally, but were with or without Rana.
- 6 In the experimental pools, there were no interspecific effects on the growth rate of either species. However, the growth rate of Bufo was lower in the experimental pools than in pools inhabited naturally. Futher, survival of Bufo was low in small pools. Lower food availability or physical factors associated with small pools, rather than interspecific competition, may be the reason why Bufo avoids breeding in small rock‐pools.
60.
金线蛙入蛰时几项生理常数间的关系研究 总被引:1,自引:0,他引:1
本文经统计学分析处理,表明金钱蛙(Ranaplancyi)入蛰时的体长与体重、胴体重和体重与肝重、脂肪体重、生殖腺重之间均存在非常显著的线性相关关系。 相似文献