5 resultados para venomous snakes

em CentAUR: Central Archive University of Reading - UK


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Although it is well known that Lucan’s Libya is a wild and threatening place, its threat is not restricted to indigenous people, places and things, such as Hannibal, Cleopatra, the Syrtes, or the desert with its catalogue of horrifying snakes. He also associates Libya with anti-Republican Romans, above all Julius Caesar, who endangers the Republic with his excessive, animalistic energy and resembles the continent where he is trapped in the final book. Although the gods as characters are removed from the world of the Bellum Civile, Lucan allows supernatural traces to linger in particular locations such as the Gallic grove in Book 3 or Thessaly in Book 6. Libya is by far the greatest of these reservoirs of frightening myth and fantasy, which do violence to the historical credibility of the narrative, just as Libya itself is presented as the origin or conduit of a number of historical characters who assault Italy and Europe. Lucan’s two mythic narratives (Antaeus in Book 4 and Medusa in Book 9) are essential parts of the hostile Libyan landscape, but in very different ways. The male Antaeus, associated with lions, is connected with a region of solid rock where he was destroyed. The female Medusa, associated with snakes, is connected with a region of shifting sands where she left a deadly, everlasting legacy. To complicate matters further, even though Medusa’s snakes represent the annihilation of the Republican self, the logic of the narrative is undermined and there is even a sympathetic subtext. As part of Libya’s historical and mythical legacy, these stories reveal that for Lucan, historical epic is linked with Republicanism, but mythical epic is in the service of dictatorship.

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The regional population of the Grey-headed Fish-Eagle (Ichthyophaga ichthyaetus) in Southeast Asia is thought to be in recent decline and its conservation status Linder threat. We undertook a systematic survey in a flooded swamp forest at the Tonle Sap Lake in Cambodia and recorded 32 pairs of eagles in an area of approximately 80 km(2). Three species of water snakes were identified as eagle prey items, previously unrecorded for this species. We suggest that this eagle population has significant regional importance and discuss potential anthropogenic threats to population stability, such as water snake harvesting and construction Of upstream hydropower dams.

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Adaptive radiations often follow the evolution of key traits, such as the origin of the amniotic egg and the subsequent radiation of terrestrial vertebrates. The mechanism by which a species determines the sex of its offspring has been linked to critical ecological and life-history traits(1-3) but not to major adaptive radiations, in part because sex-determining mechanisms do not fossilize. Here we establish a previously unknown coevolutionary relationship in 94 amniote species between sex-determining mechanism and whether a species bears live young or lays eggs. We use that relationship to predict the sex-determining mechanism in three independent lineages of extinct Mesozoic marine reptiles (mosasaurs, sauropterygians and ichthyosaurs), each of which is known from fossils to have evolved live birth(4-7). Our results indicate that each lineage evolved genotypic sex determination before acquiring live birth. This enabled their pelagic radiations, where the relatively stable temperatures of the open ocean constrain temperature-dependent sex determination in amniote species. Freed from the need to move and nest on land(4,5,8), extreme physical adaptations to a pelagic lifestyle evolved in each group, such as the fluked tails, dorsal fins and wing-shaped limbs of ichthyosaurs. With the inclusion of ichthyosaurs, mosasaurs and sauropterygians, genotypic sex determination is present in all known fully pelagic amniote groups (sea snakes, sirenians and cetaceans), suggesting that this mode of sex determination and the subsequent evolution of live birth are key traits required for marine adaptive radiations in amniote lineages.

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