ABSTRACT The marginal populations of the Sahara blue-eyed pond turtle, Mauremys leprosa saharica, in the southern-most species distribution range in the pre-Saharan areas of north-west Africa, are faced with extreme environmental conditions of arid climate and anthropogenic and climate change mediated water and land salinisation. In the current study, we investigated a small and isolated population of M. l. saharica at Sidi El Mehdaoui oasis in the Lower Draa River, southern Morocco, in order to assess its osmo- and iono-regulatory abilities and tolerance to salinity and dehydration. Upon capture, turtles were weighed and measured for shell dimensions and blood and voided urine were taken. Tests of exposure to different levels of water salinity (0%, 35%, and 50% seawater) and maintenance out of water (estivation simulation) were carried out. Osmolalities and Na+, Cl−, K+, and urea concentrations were determined in plasma and voided urine, and glycaemia was measured in blood, before and after tests. Turtles were able to survive in brackish waters with a salinity as high as 24% seawater (8.4 ppt). Their voided urine was hypotonic to plasma, which indicated that they could use their bladder water reserves for osmo- and iono-regulation until the iso-osmocity level beyond which osmotic and ionic anhomeostasy can occur. Experimental tests showed that the osmo- and iono-regulatory capacities of these turtles are relatively limited, and not enough effective to allow them to survive for long-term periods in brackish/saline waters or out of water, because of dehydration indicated by progressive weight loss to a critical threshold. The increased drought, water salinisation and habitat fragmentation related to anthropogenic activities and climate change, represent great threats that can create habitats exceeding the species’ threshold for a long-term persistence of the vulnerable small marginal populations of the Saharan pond turtle. So, conservation measures of these populations and their habitats are urgently needed.

中文翻译：

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来自摩洛哥南部下德拉盆地半咸水池塘的撒哈拉沙漠蓝眼龟 Mauremys leprosa saharica (Testudines: Geoemydidae) 对盐分和脱水的耐受性

摘要 位于非洲西北部前撒哈拉地区最南端物种分布范围内的撒哈拉蓝眼塘龟 Mauremys leprosa saharica 的边缘种群面临着干旱气候和人为和气候的极端环境条件。变化介导的水和土地盐碱化。在目前的研究中，我们调查了 M. l. 摩洛哥南部德拉河下游 Sidi El Mehdaoui 绿洲的 saharica，以评估其渗透和离子调节能力以及对盐度和脱水的耐受性。捕获后，海龟被称重并测量贝壳尺寸，并采集血液和排泄的尿液。进行了暴露于不同水盐度（0%、35% 和 50% 海水）和水外维护（估算模拟）的测试。在测试前后测定血浆和排尿中的渗透压和 Na+、Cl-、K+ 和尿素浓度，并在血液中测量血糖。海龟能够在海水盐度高达 24% (8.4 ppt) 的咸水中生存。他们排尿的尿液对血浆是低渗的，这表明他们可以利用膀胱水储备进行渗透和离子调节，直到等渗水平超过该水平，渗透和离子稳态就会发生。实验测试表明，这些海龟的渗透和离子调节能力相对有限，不足以让它们在微咸水/咸水或缺水的环境中长期生存，因为体重逐渐增加表明脱水损失到临界阈值。干旱加剧，与人为活动和气候变化相关的水盐碱化和栖息地破碎化，构成了巨大的威胁，可以创造超过物种阈值的栖息地，从而使撒哈拉池塘龟的脆弱小边缘种群长期存在。因此，迫切需要对这些种群及其栖息地采取保护措施。