Browsing by Author "Muze, Siphiwe Elizabeth"

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    Students on the Ratio and Polymorphism in Hyperolius Puncticulatus (VFR) Rhacophorida eat Amani, Tanzania.
    (University of Dar es Salaam, 1976) Muze, Siphiwe Elizabeth
    Hyporoliuspuncticulatus (Rhacophoridae), were sampled from a man-made lake at Amani, in the Eastern Usambara Mountains, Tanzania. This sampling formed the basis of an ecological and genetical study, carried out between April and October, 1975.The primary sex ratio was found to fit with the normal 1:1 expectation, whereas the sex ratio in the adult population was found to be almost 9:1 in favors of males. The proportion of males to females did not remain constant from month to month as fluctuations were evident during the peak of the reproductive season and when young males returned to the lake from the forest peripheral to the lake. Several factors have been suggested as contributing, at least in part, to the sex ratio disparity. First, the females migrate from the lake to the peripheral forest more than the males. Second, there is evidence of selective predation accentuated by the dimorphic nature of the species. Third, there could be differential mortality between the sexes. The ecological and genetical significance of distorted sex ratios have also been discussed.The analysis of polymorphism in Hy-peroliuspuncticulatus has confirmed that, like most of the Hyperolius species, itis highly polymorphic with five distinct morphs identified and named substriatus, choloensis, maculztus, and reticular. The males are more polymorphic than female since the maculatus form consists of only males. The morph frequencies show that the most abundantand probably the most successful morph is substriatus, 60% of the total sampled population. The implications of polymorphism in this species are that it maximizes protection from a variety of predators under variable textural and seasonal conditions. Natural selection, therefore, is most influential in such polymorphisrns. Apostatic selection, Gene flow and possibly genetic constitution of the individual frogs have been suggested as major factors which may be maintaining polymorphism inH. puncticulatus at Amani. Apostatic selection has,however, been emphasized mainly because of the nature ofH. puncticulatus predators (snakes, birds, spiders) and their searchimage formation. The mimicry relationship of the spider and frog suggest a well-developed predation pressure situation. Some aspects of the genetics of these frogs have been elucidated, though inconclusively, due to the high mortality in the reared crosses. However, sex-linkage, sex-limited gene effects and differential selective advantage have been suggested as major factors which may be operating in maintaining some of the morphs. For example, the abundance of the all-male maculatus morph, especially in the light ofthe evident assortative matings in these frogs, implies that it has some selective advantages over the other morphs.Capture - recapture data analysis has revealed thatL. puncticulatus population at Amani is fairly large. The implication of a large population as an indication of stable gene frequencies has been stressed.The reproductive behaviour of these frogs was investigated and it has been shown. that the eggs are laid all at once in batches of c. 130 eggs, enclosed in a gelatinous mass and partially submerged in water. The ability of these eggs to develop in submerged and exposed conditions has been suggested to be evolutionarily significant for the survival of this species, especially in rapidly changing environmental conditions which H.puncticulatus may face. The growth rates of larvae using weights and lengths showed an initial rapid growth, which slowed down at metamorphosis. The post-metamorphosis juveniles show a uniform phenotype with characteristic cantho-dorsolateral and middorsal lines. The uniformity in phenotype and the migratory behaviour of these juveniles appear to play a major role in protecting the species against predators and against intraspecific competition, respectively.