Institute of Marine Biology, College of Life Sciences, National Taiwan Ocean University, Keelung, Taiwan.
Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung, Taiwan.
PLoS One. 2020 Mar 26;15(3):e0230742. doi: 10.1371/journal.pone.0230742. eCollection 2020.
The sulphur-rich and acidic vent waters of a shallow hydrothermal vent field next to Kueishan Island in Taiwan provide a specific and generally toxic environment. Among only a few aquatic organisms able to survive there, the grapsoid crab Xenograpsus testudinatus is the dominant species with a high population density in the vent area. Here we study the gender-specific distribution, morphological traits, and relationship of wet weight vs. carapace width of this crab. A total of 1120 individuals including 831 male and 289 female (included 15 ovigerous) were examined during August and September in 2011 and May and September in 2012. Except in August 2011, there are no significant differences in the distribution of X. testudinatus in the hydrothermal vent area from the vent spout during most months. Among crabs, the weight of male (6.87 ± 2.90 g) was significantly heavier than that of females (4.17 ± 1.25 g) (p < 0.001, Student's t-test). As for the wet weight of crabs, significant differences were noted in both the length of chela and the width of carapace between males and females. Sexual dimorphism of X. testudinatus is evident in three morphological traits. Pearson's correlation showed a significant and positive correlation (p < 0.001) of wet weight, width of carapace and length of chela of the two sexes. Ovigerous crabs (shortest carapace width: 1.93 cm) were present in the specimen collected from August 2011 and May 2012. The ovigerous crabs were not found in the samples collected from September in both years 2011 and 2012, indicating that reproduction may have ceased during the period of sampling. The present results suggested that the reproductive period of X. testudinatus was before September. The distribution pattern and sexual dimorphism of X. testudinatus provided a better understanding of the idiobiology of this dominant metazoan in the hydrothermal vent area.
台湾龟山岛附近浅水热液喷口场富含硫和酸性的喷口水域提供了一个特殊且普遍有毒的环境。在少数能够在那里生存的水生生物中，掠食性蟹 Xenograpsus testudinatus 是优势物种，在喷口区具有高密度的种群。在这里，我们研究了这种蟹的性别特异性分布、形态特征以及湿重与甲壳宽度的关系。在 2011 年 8 月至 9 月和 2012 年 5 月至 9 月期间，共检查了 1120 只个体，其中包括 831 只雄性和 289 只雌性（包括 15 只抱卵）。除 2011 年 8 月外，在大多数月份，Xenograpsus testudinatus 在热液喷口区的分布与喷口喷口没有明显差异。在螃蟹中，雄性（6.87 ± 2.90 g）的体重明显重于雌性（4.17 ± 1.25 g）（p < 0.001，学生 t 检验）。至于螃蟹的湿重，雄性和雌性的螯长和甲壳宽度都有显著差异。Xenograpsus testudinatus 的性二型性在三个形态特征上表现明显。Pearson 相关分析显示，两性湿重、甲壳宽度和螯长之间存在显著正相关（p < 0.001）。在 2011 年 8 月和 2012 年 5 月采集的样本中发现了抱卵蟹（最短甲壳宽度：1.93 cm）。在 2011 年和 2012 年 9 月的样本中均未发现抱卵蟹，表明繁殖可能在采样期间停止。本研究结果表明，Xenograpsus testudinatus 的繁殖期在 9 月之前。Xenograpsus testudinatus 的分布模式和性二型性为了解这种在热液喷口区占优势的后生动物的生活史生物学提供了更好的认识。
