Reconstruction of paternal genotypes over multiple breeding seasons reveals male green turtles do not breed annually

For species of conservation concern, knowledge of key life-history and demographic components, such as the number and sex ratio of breeding adults, is essential for accurate assessments of population viability. Species with temperature-dependent sex determination can produce heavily biased primary sex ratios, and there is concern that adult sex ratios may be similarly skewed or will become so as a result of climate warming. Prediction and mitigation of such impacts are difficult when life-history information is lacking. In marine turtles, owing to the difficultly in observing males at sea, the breeding interval of males is unknown. It has been suggested that male breeding periodicity may be shorter than that of females, which could help to compensate for generally female-biased sex ratios. Here we outline how the use of molecular-based paternity analysis has allowed us, for the first time, to assess the breeding interval of male marine turtles across multiple breeding seasons. In our study rookery of green turtles (Chelonia mydas), 97% of males were assigned offspring in only one breeding season within the 3-year study period, strongly suggesting that male breeding intervals are frequently longer than 1year at this site. Our results also reveal a sex ratio of breeding adults of at least 1.3 males to each female. This study illustrates the utility of molecular-based parentage inference using reconstruction of parental genotypes as a method for monitoring the number and sex ratio of breeders in species where direct observations or capture are difficult.     

Turtle mating patterns buffer against disruptive effects of climate change

For organisms with temperature-dependent sex determination (TSD), skewed offspring sex ratios are common. However, climate warming poses the unique threat of producing extreme sex ratio biases that could ultimately lead to population extinctions. In marine turtles, highly female-skewed hatchling sex ratios already occur and predicted increases in global temperatures are expected to exacerbate this trend, unless species can adapt. However, it is not known whether offspring sex ratios persist into adulthood, or whether variation in male mating success intensifies the impact of a shortage of males on effective population size. Here, we use parentage analysis to show that in a rookery of the endangered green turtle (Chelonia mydas), despite an offspring sex ratio of 95 per cent females, there were at least 1.4 reproductive males to every breeding female. Our results suggest that male reproductive intervals may be shorter than the 2-4 years typical for females, and/or that males move between aggregations of receptive females, an inference supported by our satellite tracking, which shows that male turtles may visit multiple rookeries. We suggest that male mating patterns have the potential to buffer the disruptive effects of climate change on marine turtle populations, many of which are already seriously threatened.     

Thermal control of hatchling emergence patterns in marine turtles

The emergence patterns of green turtle (Chelonia mydas) hatchlings on two beaches on Ascension Island, South Atlantic were monitored and related to thermal patterns in the sand at 10, 20, 30 and 40 cm depth. A total of 6001 hatchlings were recorded emerging on Long Beach, and 3171 emerged on North East Bay during the study period. No significant difference was observed in the temporal pattern of hatchling emergence among nights, or between the two beaches. Hatchling emergence predominantly occurred at night with over 93% of hatchlings emerging during the hours of darkness. Almost all hatchlings emerging in daylight suffer predation by the Ascension frigatebird (Fregata aquila). Counts of frigatebirds both above the study beaches and offshore were highest just after sunrise, with a smaller peak prior to sunset, when frigatebirds were found to predate hatchlings emerging, crawling down the beach or detected in inshore waters. The likely thermal cues controlling hatchling emergence were investigated (temperature at different depths, thermal gradients in the sand and temperature change). The most plausible thermal factor appears to be the change of temperature at superficial sand depths, with hatchling emergence inhibited when subsurface sand temperatures were increasing. This simple mechanism is likely to ensure predominantly nocturnal hatchling emergence regardless of sand albedo, seasonality or latitude as long as night is relatively cooler than day.     

慢性氨暴露对中华鳖幼鳖血浆总氨氮、皮质酮浓度及组织氨代谢酶活性的影响

本文观测了慢性氨暴露对中华鳖(Pelodiscussinensis)幼鳖血浆总氨氮、皮质酮浓度及与氨代谢有关的酶活性的影响。将中华鳖暴露在总氨氮(TAN)浓度为32.4、57.6、83.5mg/L(分别记为1、2、3组)的水环境中饲养42d,以自然晾晒脱氯自来水饲养组为对照(记为0组),pH值控制在7.80-7.85。检测氨暴露2、4、8、24、48h、42d后血浆TAN与8、24、48h、42d后皮质酮浓度,42d后肝、肌肉与脑中谷氨酰胺合成酶(Glutaminesynthetase,GS)、谷氨酸脱氢酶(Glutamatedehydrogenase,GDH)的活性以及特定生长率(Specificgrowthrate,SGR)的变化。结果表明:0、1组血浆TAN随时间没有明显变化,2、3组血浆TAN随时间呈现先增加后降低的趋势,分别在8h和48h达到峰值,42d时各组间血浆TAN没有显著差异。氨暴露显著影响暴露初期血浆皮质酮水平,暴露后24h,1、3组血浆皮质酮水平显著高于对照组;42d后除2组外其他组间无显著差异。4组之间肝、肌肉和脑中GS活性均没有显著差异,肝和肌肉GDH(氨化和去氨化方向)活性也没有显著差异。各暴露组脑GDH活性和对照组相比差异不明显,但各处理组间氨化和去氨化方向脑GDH酶活差异显著。42d饲养期间各处理组SGR没有显著差异。     

Turtle groups or turtle soup: dispersal patterns of hawksbill turtles in the Caribbean

Despite intense interest in conservation of marine turtles, spatial ecology during the oceanic juvenile phase remains relatively unknown. Here, we used mixed stock analysis and examination of oceanic drift to elucidate movements of hawksbill turtles (Eretmochelys imbricata) and address management implications within the Caribbean. Among samples collected from 92 neritic juvenile hawksbills in the Cayman Islands we detected 11 mtDNA control region haplotypes. To estimate contributions to the aggregation, we performed ‘many‐to‐many’ mixed stock analysis, incorporating published hawksbill genetic and population data. The Cayman Islands aggregation represents a diverse mixed stock: potentially contributing source rookeries spanned the Caribbean basin, delineating a scale of recruitment of 200–2500 km. As hawksbills undergo an extended phase of oceanic dispersal, ocean currents may drive patterns of genetic diversity observed on foraging aggregations. Therefore, using high‐resolution Aviso ocean current data, we modelled movement of particles representing passively drifting oceanic juvenile hawksbills. Putative distribution patterns varied markedly by origin: particles from many rookeries were broadly distributed across the region, while others would appear to become entrained in local gyres. Overall, we detected a significant correlation between genetic profiles of foraging aggregations and patterns of particle distribution produced by a hatchling drift model (Mantel test, r = 0.77, P < 0.001; linear regression, r = 0.83, P < 0.001). Our results indicate that although there is a high degree of mixing across the Caribbean (a ‘turtle soup’), current patterns play a substantial role in determining genetic structure of foraging aggregations (forming turtle groups). Thus, for marine turtles and other widely distributed marine species, integration of genetic and oceanographic data may enhance understanding of population connectivity and management requirements.     

中华鳖转“全鱼”生长激素基因研究

自首例快速生长转基因鱼在我围诞生以来[1],世界上很多试验室相继开展了转基因鱼研究,以期获得快速生长[2,3]、抗逆[4,5]的养殖新品系.与传统的杂交选育方法相比,转基因育种方法摆脱了物种间遗传壁垒的桎梏,基于对目的基因功能的认识和把握,定向培育优良养殖品种,大幅缩短育种周期.     

Characterization of polymorphic microsatellite markers for the green turtle (Chelonia mydas)

We describe primers and polymerase chain reaction conditions to amplify 12 microsatellite loci from the green turtle (Chelonia mydas), including one dinucleotide, four trinucleotide and seven tetranucleotide loci. The primers were tested on 78 individuals from a Pacific population nesting in the Hawaiian Islands. The primer pairs developed in this study yielded an average of 8.33 alleles per locus (range of 3-15 alleles), an average observed heterozygosity of 0.668 (range 0.309-0.910), and an average polymorphic information content of 0.647 (range 0.287-0.894).     

温度对黄喉拟水龟性别决定的影响

研究了不同孵育温度对黄喉拟水龟(MauremysmuticaCantor)性别决定的影响,同时分析了孵育温度对胚胎发育及成活率的影响。实验设置的3个孵化温度为(25±0.5)℃,(29±0.5)℃和(33±0.5)℃。每一温度指标下设置40枚受精卵。在实验温度内,胚胎的发育速度随着孵化温度的升高而加快,所用的孵育时间也越来越短。孵化累积温度CTUs在25℃时最高,在29℃时最低,而33℃时则居中,在25℃和29℃时,孵化成活率较高,均达到97.5%。在33℃时孵化成活率只有67.5%,而在孵出的稚龟中亦有一定数量的畸形龟,累积孵化温度也高于29℃时的CTUs,说明33℃的孵育温度对胚胎发育有不利影响,预示33℃已临近其胚胎发育的存活阈(Survivalthreshold)。在25℃时,雄性子代占优势,雌性率为23.7%;在33℃时,雌性子代占绝对优势,雌性率为94.7%;在29℃时,性比达到平衡,雌性率为50%。经X2检验,在25℃及33℃时的性比与依赖概率估计的性比(1∶1)有极显著的差异(p<0.005),这种显著的偏离说明黄喉拟水龟的性别决定属于TSD机制,而且可能属于其中的TSDⅠ型,即高温产生雌性子代,低温产生雄性子代。而29℃可能是黄喉拟水龟性别决定的临界温度。     

Mechanism and cost of synchronous hatching

1. Synchrony in the timing of births is thought to have evolved as a general predator avoidance strategy. In turtles, synchronous hatching may facilitate group emergence from the nest, which in turn, may limit predation by diluting an individual's risk of predation or by simply swamping predators upon emergence. However, synchronizing hatching should not be easily achieved in natural nests because of thermal gradients affecting developmental rates.
2. We evaluated pipping synchrony in the painted turtle ( Chrysemys picta ), where the drive to hatch synchronously may be reduced, because in many populations, hatching and emergence are dissociated through hatchlings overwintering within a nest.
3. We also assessed developmental mechanisms through which synchrony occurs and explored potential trade-offs between pipping synchrony and individual fitness by determining potential short and long-term neuromuscular developmental costs to hatching prematurely. These data were also used to develop a theoretical model to determine how differential embryonic maturation rates affect hatching synchrony.
4. Underdeveloped embryos pipped much earlier than expected and at similar times to their more advanced sibs. In addition, a trade-off between hatching synchronously and neuromuscular development (motility) was evident several days after hatching and up to 9 months later, after the overwintering period.
5. Synchronous hatching is an ancestral trait in turtles, but its relevance today is not solely for predator avoidance in all species.
6. Abiotic factors during incubation (e.g. temperature regime and moisture) have long-term effects on reptiles during ontogeny but it is also clear that incubation behaviour is major factor for the persistence of these developmental costs.     

The Complete Amino Acid Sequence of Green Turtle (Chelonia mydas) Egg White Ribonuclease

Egg white ribonuclease was first found in green turtle eggs. This enzyme has been purified by CM-toyopearl cation exchange. Two isoforms (GTRNase-1 and GTRNase-2) were further separated by RP-HPLC, with the same M.W. (13 kDa) and activity. These isoforms carried one amino acid exchange of Ser and Leu at the position 37. The N-terminal sequence, ETRYEKF, was determined for the transblotted protein. Internal sequences were analyzed by protein sequencer and ESI-Q-TOF mass spectrometry for tryptic peptides (Ts). The overlapping sequences were obtained from chymotryptic peptides, CNBr fragments and ISD-MS/MS analysis. The C-terminal Ile was identified by CPase-Y. The established sequence composed of 119 residues with the molecular mass of 12,942.1 Da for GTRNase-1 and 12,967.8 Da for GTRNase-2. The comparison of sequence with known pancreatic RNases, 27 positions including catalytic residues at the position 11 and 114 were conserved. Also basic residues contributed to phosphate binding residues were conserved with the exception of Lys 66. One insertion at the position 14, and 3 deletions at the position-1, between position 64–65, and 110 and 111 were found. Two Cys residues at position 65 and 72 that form a disulfide bond in mammalian RNase were deleted and exchanged. All these difference in the sequence were similar to reptile pancreatic RNase.Data deposition: The sequence reported in this paper has been submitted to the UniProt Knowledgebase under accession No. P84844.