A novel hypothesis for the adaptive maintenance of environmental sex determination in a turtle

Temperature-dependent sex determination (TSD) is widespread in reptiles, yet its adaptive significance and mechanisms for its maintenance remain obscure and controversial. Comparative analyses identify an ancient origin of TSD in turtles, crocodiles and tuatara, suggesting that this trait should be advantageous in order to persist. Based on this assumption, researchers primarily, and with minimal success, have employed a model to examine sex-specific variation in hatchling phenotypes and fitness generated by different incubation conditions. The unwavering focus on different incubation conditions may be misplaced at least in the many turtle species in which hatchlings overwinter in the natal nest. If overwintering temperatures differentially affect fitness of male and female hatchlings, TSD might be maintained adaptively by enabling embryos to develop as the sex best suited to those overwintering conditions. We test this novel hypothesis using the painted turtle (Chrysemys picta), a species with TSD in which eggs hatch in late summer and hatchlings remain within nests until the following spring. We used a split-clutch design to expose field-incubated hatchlings to warm and cool overwintering (autumn–winter–spring) regimes in the laboratory and measured metabolic rates, energy use, body size and mortality of male and female hatchlings. While overall mortality rates were low, males exposed to warmer overwintering regimes had significantly higher metabolic rates and used more residual yolk than females, whereas the reverse occurred in the cool temperature regime. Hatchlings from mixed-sex nests exhibited similar sex-specific trends and, crucially, they were less energy efficient and grew less than same-sex hatchlings that originated from single-sex clutches. Such sex- and incubation-specific physiological adaptation to winter temperatures may enhance fitness and even extend the northern range of many species that overwinter terrestrially.     

Surfacers change their dive tactics depending on the aim of the dive: evidence from simultaneous measurements of breaths and energy expenditure

Air-breathing divers are assumed to have evolved to apportion their time between surface and underwater periods to maximize the benefit gained from diving activities. However, whether they change their time allocation depending on the aim of the dive is still unknown. This may be particularly crucial for ‘surfacers’ because they dive for various purposes in addition to foraging. In this study, we counted breath events at the surface and estimated oxygen consumption during resting, foraging and other dives in 11 green turtles (Chelonia mydas) in the wild. Breath events were counted by a head-mounted acceleration logger or direct observation based on an animal-borne video logger, and oxygen consumption was estimated by measuring overall dynamic body acceleration. Our results indicate that green turtles maximized their submerged time, following this with five to seven breaths to replenish oxygen for resting dives. However, they changed their dive tactic during foraging and other dives; they surfaced without depleting their estimated stores of oxygen, followed by only a few breaths for effective foraging and locomotion. These dichotomous surfacing tactics would be the result of behavioural modifications by turtles depending on the aim of each dive.     

草鱼、中华鳖IL-2活性影响因素的研究

结果显示:当年草鱼种和中华鳖脾细胞培养上清液中能检测出IL-2活性,而且1龄以上草鱼、中华鳖的IL-2活性高于当年孵化的草鱼和中华鳖.草鱼、中华鳖脾细胞在25℃培养温度条件下,其上清液中IL-2活性最高,35℃次之,15℃最低.因此,草鱼、中华鳖IL-2活性在一定范围内是随着年龄增加而增强和依赖温度的.通过小鼠胸腺细胞增殖和对小鼠L929细胞杀伤率的实验表明37℃比25℃检测温度下所测的IL-2活性高,而中华鳖胸腺细胞增殖实验却显示25℃检测温度下IL-2活性高于37℃.本文讨论了年龄、温度对免疫反应影响的机理.       

Accumulation of trace metals in eggs and hatchlings of Chelonia mydas

BackgroundThe objective of this study was to verify the accumulation of trace metals in eggs and hatchlings of Chelonia mydas, evaluating if metal accumulation is originated from maternal transfer and/or from the incubation environment. Other assessments were also performed, as metal distribution in different tissues (blood, kidney, liver, muscle, and turtle shells) of newly hatched turtles, and genotoxic analysis, to verify possible damages caused by the presence of metals.MethodsThe assessments were carried out by quantifying Cd, Ni, Pb, Mn and Fe in egg sample collected during laying time (eggshells (ELT) and egg content (EC)), eggshells from newly hatched turtles (ENH), hatchlings tissues (H - blood, kidney, liver, muscle, and shell)) (n = 18 for each biological sample - 3 of each nest) and nest sediments (n = 6, one of each nest). Comparative analysis were made between ELT and ENH, as well as between egg content (EC) and the sum of tissue samples from hatchlings, using Mann-Whitney hypothesis test (p < 0,05). The amount of metals in different hatchling was quantified and followed by the Dunn post-test. A principal component analysis (PCA) was also employed.ResultsMetals studied were found in all investigated samples. The concentration of a great amount of investigated metals was significantly higher (P=<0.001) in eggshells from ENH than in ELT. An increase in Cd (2.16-fold), Pb (3.47-fold), Fe (6.83-fold) and Mn (195.57-fold) concentration was noticed in ENH. We also observed an increase in Fe (1.59-fold), Mn (1.74-fold) and Ni (1.59-fold) concentration in hatchling, when compared with EC, due to transfer from nest sediments. In relation to the hatchling’s tissues, blood was shown to accumulate higher concentrations of Ni and Pb, while shells accumulated more Cd and Fe, and Mn is more associated with liver and kidney. Fe was the highest accumulated metal in both tissues, and muscles presented discrete concentrations of Ni, Mn, and Pb. A mean concentration of 1.25‰ MN was obtained in C. mydas hatchlings, indicating that the accumulation of metals in hatchlings didn’t cause toxicology effects.ConclusionHatchlings accumulate metals through the maternal and sediment transfer, although the levels of metal accumulation were not enough to cause genotoxic damage.     

Seasonality and numbers of green turtles Chelonia mydas nesting on the Pitcairn Islands

During 1991 and 1992 the first regular field observations of green turtles, Chelonia mydas , on the Pitcairn Islands (South Pacific) revealed that nesting occurs only on Henderson where about 10 females laid eggs (c. 1% of the French Polynesian population). Substrates on Pitcairn and Ducie Atoll are unsuitable for nesting and no signs of nesting were found on Oeno Atoll where the terrain appears suitable.     

鳖源胶原蛋白提取纯化及在生物材料中的应用

近年来,胶原蛋白因其良好的生物学性能在生物材料应用中得到越来越多的关注,为了建立一种快速高效的鳖源胶原蛋白纯化方法和探究其在生物材料中的应用价值,首先用Van Gieson染色法和苦味酸-天狼星红染色法观察裙边胶原纤维组织结构,发现裙边胶原纤维含量非常高且类型主要是Ⅰ型。采用不同截留分子量的透析袋对裙边胶原蛋白粗提液进行直接透析纯化,发现截留分子量为100 k Da的透析袋在透析48 h后对裙边胶原蛋白的纯化效果最好,SDS-PAGE检验显示几乎没有杂带。对裙边胶原蛋白生物学性能包括吸水性、体外降解性进行考察,其吸水力和持水力分别高达12.06 g/g和98.21%,且在72 h后被完全降解;对裙边胶原蛋白海绵的溶血性、皮肤致敏性、肝部创伤止血性、促创伤皮肤愈合性进行了研究,并和交联胶原进行比较,发现裙边胶原蛋白和交联胶原均不会造成SD大鼠溶血和皮肤过敏,二者均具有良好的止血效果,且裙边胶原蛋白能显著缩短创伤皮肤愈合时间,具有良好的促创伤皮肤愈合性,而交联胶原效果欠佳。本研究表明裙边胶原蛋白表现出了优良的生物学性能,在生物材料领域具有很大应用价值。     

Projected changes in climatic suitability for Kinosternon turtles by 2050 and 2070

Chelonians are expected to be negatively impacted by climate change due to limited vagility and temperature‐dependent sex determination. However, few studies have examined how freshwater turtle distributions may shift under different climate change scenarios. We used a maximum entropy approach to model the distribution of five widespread North American Kinosternon species (K. baurii, K. flavescens, K. hirtipes, K. sonoriense, and K. subrubrum) under four climate change scenarios. We found that areas with suitable climatic conditions for K. baurii and K. hirtipes are expected to decline substantially during the 21st century. In contrast, the area with suitable climate for K. sonoriense will remain essentially unchanged, while areas suitable for K. flavescens and K. subrubrum are expected to substantially increase. The centroid for the distribution of four of the five species shifted northward, while the centroid for K. sonoriense shifted slightly southward. Overall, centroids shifted at a median rate of 37.5 km per decade across all scenarios. Given the limited dispersal ability of turtles, it appears unlikely that range shifts will occur rapidly enough to keep pace with climate change during the 21st century. The ability of chelonians to modify behavioral and physiological responses in response to unfavorable conditions may allow turtles to persist for a time in areas that have become increasingly unsuitable, but this plasticity will likely only delay local extinctions.     

Initiation and ultrastructure of a reptilian fibroblast cell line obtained from cutaneous fibropapillomas of the green turtle,Chelonia mydas

Summary Two fibroblastic cell lines were established from explants of fibropapillomas of each of two different green turtles (Chelonia mydas). These cells, designated GTFP (Green Turtle Fibropapilloma), were subcultured approximately 30 times at 30°C in Eagle’s minimal essential media supplemented with 2 to 10% fetal bovine serum. The ultrastructural morphology of the cultured fibroblasts is described. The cells contained abundant rough endoplasmic reticulum, polyribosomes, and mitochondria; collagen fibrils were visible in the extracellular space. No viruslike particles or evidence of other pathogenic agents could be demonstrated by electron microscopy in any of the cultured cells examined. Supported in part by a grant from Sea World Research Institute, Hubbs Marine Research Center, San Diego, California 92109, and the Chelonia Institute, Arlington, Virginia 22209. Published as University of Florida, College of Veterinary Medicine, Journal Series no. 192.