Abstract

Individuals of the terrestrial hermit crab Coenobita clypeatus Fabricius, 1787 use different gastropod shells for shelter during their life span. Availability of shells affects population traits, including density and size structure, influencing their fitness and survival. Locality and human presence can induce variation in the diversity and size of gastropod shells, influencing available shells for hermit crabs. We assessed how the diversity, size, and abundance of the occupied species of gastropod shells affect the density and demography of C. clypeatus in two marine protected areas (MPA) with different recreational use in Puerto Rico, Manatí (high) and Mona Island (low). We also evaluated the relationship between three shell traits (length, width, and aperture length) and the length of the crab chela as a size proxy. We did not find differences in the sex ratio. The density and median chela sizes were higher in crabs from Manatí. In Mona, however, they reached larger sizes. The diversity of occupied shell species was higher in Manatí than in Mona. Dimensions of occupied shells differed between genera and between study sites, and they scaled positively with hermit crab size. Differences in shells diversity, sizes, and abundance between MPAs might cause differences in density and demography of C. clypeatus. We only found large shells of Cittarium pica (Linnaeus, 1758), the only species occupied by larger individuals, occupied by hermit crabs in Mona. The low abundance of C. pica shells in Manatí might have affected the size of hermit crabs in this locality. Our in situ findings suggest that hermit crabs need larger shells to reach larger sizes as previously shown, and that location and the degree of human intervention might influence the availability of gastropod shells. Our study is the first attempt to characterize the demography and gastropod shells used by hermit crabs in Puerto Rico.

中文翻译：

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1787年波多黎各两个海洋保护区的陆生寄居蟹Coenobita clypeatus Fabricius（人口十足目：Anomura：Coenobitidae）的人口统计数据和贝壳使用

摘要

1787年陆地寄居蟹Coenobita clypeatus Fabricius的个体在其寿命期间使用不同的腹足动物贝壳作为庇护所。贝壳的可利用性会影响种群的性状，包括密度和大小结构，从而影响其适应性和生存能力。地点和人类的存在会导致腹足纲动物壳的多样性和大小发生变化，从而影响寄居蟹的可用壳。我们评估了腹足动物贝壳所占物种的多样性，大小和丰度如何影响C. clypeatus的密度和人口统计学在波多黎各的两个海洋保护区（MPA）中，它们的娱乐用途不同，马纳蒂（高）和莫纳岛（低）。我们还评估了三个壳特征（长度，宽度和孔径长度）与蟹螯虾的长度之间的关系，以作为大小替代。我们没有发现性别比例有差异。马纳蒂蟹的密度和中位螯虾大小较高。但是，在莫娜（Mona），它们达到了更大的尺寸。马纳蒂的被占领贝壳物种的多样性高于莫娜。虫壳的大小在属之间和研究地点之间都不同，并且与寄居蟹的大小成正比。MPA之间壳的多样性，大小和丰度的差异可能导致C. clypeatus的密度和人口统计学差异。我们只发现了Cittarium pica（Linnaeus，1758）是蒙纳州唯一被较大个体占据，被寄居蟹占据的物种。马纳蒂（Manatí）的C. pica贝壳数量少，可能已经影响了该地区寄居蟹的大小。我们的原位研究结果表明，寄居蟹需要更大的贝壳才能达到更大的尺寸，如先前所示，而且人为干预的位置和程度可能会影响腹足动物贝壳的可利用性。我们的研究是表征波多黎各寄居蟹所使用的人口统计学和腹足纲贝壳的首次尝试。