Human overexploitation and extinction risk correlates of Chinese snakes

China is one of the countries with the richest snake biodiversity in the world. However, about one‐third of all 236 species are now considered threatened, partially due to the intense human overexploitation. Despite that, to date, no study has explicitly investigated the patterns and processes of extinction and threats of Chinese snakes, or between human exploited and unexploited snake subgroups. We addressed the following three questions: 1) which snake families proportionally include more human exploited species than expected by chance? 2) Which species traits and extrinsic factors are correlated with their extinction risk? 3) Are there differences between human exploited and unexploited species in terms of patterns and processes of extinction? We found that the family Elapidae contained a significantly higher number of exploited species. Considering eight species traits and four extrinsic factors, we performed phylogenetic correlation tests, finding that small geographic range size, large body length, oviparous reproduction, diurnal activity and high human exploitation were important in determining the extinction risk of all Chinese snakes. Moreover, human exploited snakes had a higher percentage of threatened species and large‐bodied species than unexploited snakes. Extinction risk of human exploited species was related to body length, reproduction mode and activity period, whereas that of human unexploited species were associated with geographic range size, microhabitat and annual temperature. Overall, we highlight the phylogenetic non‐random exploitation of snakes, and different factors underlying species response to human overexploitation. We suggest that conservation priority should be given to exploitation‐prone families and species with extinction‐prone traits, as identified in this study. Moreover, human exploited and unexploited species should be managed considering different strategies since their extinction risk was associated with different ecological traits. Conservation actions should also focus on preventing human threats, such as human overexploitation and habitat loss, for the effective preservation of Chinese snakes.     

SPERM COMPETITION AND REPRODUCTIVE MODE INFLUENCE SPERM DIMENSIONS AND STRUCTURE AMONG SNAKES

The role of sperm competition in increasing sperm length is a controversial issue, because findings from different taxa seem contradictory. We present a comparative study of 25 species of snakes with different levels of sperm competition to test whether it influences the size and structure of different sperm components. We show that, as levels of sperm competition increase, so does sperm length, and that this elongation is largely explained by increases in midpiece length. In snakes, the midpiece is comparatively large and it contains structures, which in other taxa are present in the rest of the flagellum, suggesting that it may integrate some of its functions. Thus, increases in sperm midpiece size would result in more energy as well as greater propulsion force. Sperm competition also increases the area occupied by the fibrous sheath and outer dense fibers within the sperm midpiece, revealing for the first time an effect upon structural elements within the sperm. Finally, differences in male–male encounter rates between oviparous and viviparous species seem to lead to differences in levels of sperm competition. We conclude that the influence of sperm competition upon different sperm components varies between taxa, because their structure and function is different.     

黑龙江省蛇类物种多样性调查及保护

通过多年的野外调查和采集,共在黑龙江省31个县（市、区）获得蛇类标本592号.结合有关资料记载,证实黑龙江省蛇类隶属2科6属11种,约占我国蛇类总数的5.42%,均属于古北界物种,与国内其他省相比黑龙江省蛇类物种多样性水平较低,种群数量较少.建议加强对蛇类保护生物学的研究及其生境的保护,合理开发利用蛇类资源.     

Uncoupling ecological innovation and speciation in sea snakes (Elapidae, Hydrophiinae, Hydrophiini)

The viviparous sea snakes (Hydrophiini) are by far the most successful living marine reptiles, with ～ 60 species that comprise a prominent component of shallow-water marine ecosystems throughout the Indo-West Pacific. Phylogenetically nested within the ～ 100 species of terrestrial Australo-Melanesian elapids (Hydrophiinae), molecular timescales suggest that the Hydrophiini are also very young, perhaps only ～ 8-13 Myr old. Here, we use likelihood-based analyses of combined phylogenetic and taxonomic data for Hydrophiinae to show that the initial invasion of marine habitats was not accompanied by elevated diversification rates. Rather, a dramatic three to six-fold increase in diversification rates occurred at least 3-5 Myr after this transition, in a single nested clade: the Hydrophis group accounts for ～ 80% of species richness in Hydrophiini and ～ 35% of species richness in (terrestrial and marine) Hydrophiinae. Furthermore, other co-distributed lineages of viviparous sea snakes (and marine Laticauda, Acrochordus and homalopsid snakes) are not especially species rich. Invasion of the oceans has not (by itself) accelerated diversification in Hydrophiini; novelties characterizing the Hydrophis group alone must have contributed to its evolutionary and ecological success.     

鲁西地区蛇类的分布格局

以山东聊城分布的7种蛇类作为研究对象,探讨了鲁西平原区蛇类的群落结构和分布格局.结果 表明,该区蛇类平均分布密度较高的是白条锦蛇Elaphe dione、赤链蛇Dinodon rufozonatum和虎斑颈槽蛇大陆亚种Rhabdophis tigrina lateralis.多数蛇类倾向于选择湿地周边、边缘富有灌草丛的农田区以及有丰富草被的居民区等为栖息地,该区蛇类的栖息地选择有着显著的不重叠性.     

Snake communities of moist rainforest and derived savanna sites of Nigeria: biodiversity patterns and conservation priorities

The taxonomic composition and the abundance of two communities of snakes were studied in two different areas of southern Nigeria. One community was studied in a derived savanna area (environs of Ejule, 06°54N, 07°23E), and one community was studied in a moist rainforest area (environs of Eket, 04°50N, 07°59E). Both the specific diversity and the mean frequency of observation of snakes were significantly higher in the forest area than in the savanna area, and the dominance index was higher in the savanna than in the forest site. However, most of the species were found in only one of the two areas, depending on their habitat requirements (e.g. Gastropyxis smaragdina, Dispholidus typus, Thelotornis kirtlandii, Dendroaspis jamesoni, Bitis nasicornis, Causus maculatus, etc). The forest community housed a significant number of arboreal and semiaquatic taxa, but in both sites most of the species were terrestrial. The commonest species in the forest area was an oviparous, semiaquatic, batracophagous natricine snake (Afronatrix anoscopus), whereas the commonest species in the savanna area was an oviparous terrestrial lacertophagous psammophine snake (Psammophis phillipsi). Some conservation implications of our biodiversity analyses are presented. It is suggested that the moist rainforest represents a critically endangered habitat, and should deserve special attention by the international scientific community. Oil industry activity is especially dangerous for snake communities, especially in the southernmost regions of Nigeria.     

Angiostatin-like molecules are generated by snake venom metalloproteinases

Angiostatin is a plasminogen-derived anti-angiogenic factor composed of its first four kringle structures. This molecule is generated by proteolytic cleavage of plasminogen by some proteolytic enzymes in vitro. Since venoms of viper snakes are a rich source of both serine- and metalloproteinase, we hypothesized that angiostatin-like polypeptides could be generated during the envenomation after snake bites and play a pathophysiological role in the local tissue damage and regeneration. Our results showed that crude venoms from several species of Bothrops snakes were able to generate angiostatin-like polypeptides and purified metalloproteinases but not serine proteinases from Bothrops jararaca and Bothrops moojeni venoms were responsible for their generation in vitro. The putative plasminogen cleavage sites by the crude venoms and purified proteinases were determined by N-terminal amino acid sequencing of the angiostatin-like molecules. Angiostatin-like peptides derived from human plasminogen digestion by jararhagin, a metalloproteinase isolated from B. jararaca venom, inhibited endothelial cell proliferation in vitro. These results indicate that angiostatin-like molecules can be generated upon snakebite envenomations and may account for the poor and incomplete regenerative response observed in the damaged tissue.     

Time course analyses of the thermoregulatory responses to melatonin and chlorpromazine in bull snakes (Pituophis melanoleucus)

Intraperitoneal injections of either melatonin (MEL) or chlorpromazine (CPZ) significantly lowered preferred body temperature (T_b) of bullsnakes, Pituophis melanoleucus. Multiple comparison procedures showed that T_b for both MEL and CPZ treatments differed significantly from both the injected and non-injected control groups. However, T_b for MEL treatments did not differ from those of CPZ treatments (t=0.471; df=12; P=0.646), indicating that each drug has a similar effect on thermal selection. Our results obtained from time-course experiments support earlier experiments where a repeated measures design was used to test treatment effects of MEL and CPZ on thermal selection. However, we further show that injected controls (saline and ethanol injection) do not differ from non-injected controls (no injection) for both MEL and CPZ experiments. Although there are no differences between T_b of snakes receiving MEL or CPZ, time-course analyses indicate that the duration of thermoregulatory responses differ between MEL and CPZ treatments. This indicates that CPZ treatments may be more effective in increasing the amount of time required for individuals to return to normal preferred T_b or set temperature (T_set). The initial duration of thermoregulatory responses to the first injection of MEL differed significantly from the second injection. There were no differences in the duration of thermoregulatory responses between the first and second injections of CPZ. There are no data for the metabolic half-life of MEL in ectothermic vertebrates. Our study provides some information regarding the time-course of thermoregulatory responses to elevated levels of MEL via intraperitoneal injections of either MEL or CPZ, a metabolic antagonist of MEL.