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Mechanisms causing size differences of the land hermit crab Coenobita rugosus among eco-islands in Southern Taiwan

Numerous environmental factors can influence body size. Comparing populations in different ecological contexts is one potential approach to elucidating the most critical of such factors. In the current study, we found that the body size of the land hermit crab Coenobita rugosus was significantly lar...

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Autores principales: Hsu, Chia-Hsuan, Soong, Keryea
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5384810/
https://www.ncbi.nlm.nih.gov/pubmed/28388638
http://dx.doi.org/10.1371/journal.pone.0174319
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author Hsu, Chia-Hsuan
Soong, Keryea
author_facet Hsu, Chia-Hsuan
Soong, Keryea
author_sort Hsu, Chia-Hsuan
collection PubMed
description Numerous environmental factors can influence body size. Comparing populations in different ecological contexts is one potential approach to elucidating the most critical of such factors. In the current study, we found that the body size of the land hermit crab Coenobita rugosus was significantly larger on Dongsha Island in the South China Sea than on other eco-islands around Southern Taiwan. We hypothesized that this could be due to differences in (1) shell resources, (2) parasite impact, (3) competition, (4) predation, and (5) food. We found no supporting evidence for the first three hypotheses; the shells used by the hermit crabs on Dongsha were in poorer condition than were those used elsewhere, extremely few individuals in the region had ectoparasites, and the density of hermit crabs varied considerably among localities within each island. However, significantly higher percentages of C. rugosus reached age 3 years on Dongsha than at Siziwan bay in Taiwan. Two growth rate indices inferred from size structures suggested faster growth on Dongsha than at Siziwan. The condition index (i.e., the body mass/shield length ratio of C. rugosus) was also greater on Dongsha than at Siziwan. Therefore, Dongsha hermit crabs seem to have superior diet and growth performance. Seagrass debris accumulation at the shore of Dongsha was considerable, whereas none was observed at Siziwan or on the other islands, where dicot leaves were the dominant food item for the vegetarian hermit crabs. We then experimentally evaluated the possible role of seagrass as food for C. rugosus. The crabs on Dongsha preferred seagrass to dicot leaves, and their growth increment was faster when they fed on seagrass than when they fed on dicot leaves; no such differences were found in the Siziwan hermit crabs. The aforementioned results are compatible with the food hypothesis explaining the size differences among the islands. The predator hypothesis could explain the greater life span but not the other findings. Populations of C. rugosus on islands with seagrass debris piles probably contribute more to the gene pool of the species because higher proportions of these populations could achieve high fecundity. The fate of these terrestrial hermit crabs may rely on the health of underwater seagrass ecosystems that are under threat from global change.
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spelling pubmed-53848102017-05-03 Mechanisms causing size differences of the land hermit crab Coenobita rugosus among eco-islands in Southern Taiwan Hsu, Chia-Hsuan Soong, Keryea PLoS One Research Article Numerous environmental factors can influence body size. Comparing populations in different ecological contexts is one potential approach to elucidating the most critical of such factors. In the current study, we found that the body size of the land hermit crab Coenobita rugosus was significantly larger on Dongsha Island in the South China Sea than on other eco-islands around Southern Taiwan. We hypothesized that this could be due to differences in (1) shell resources, (2) parasite impact, (3) competition, (4) predation, and (5) food. We found no supporting evidence for the first three hypotheses; the shells used by the hermit crabs on Dongsha were in poorer condition than were those used elsewhere, extremely few individuals in the region had ectoparasites, and the density of hermit crabs varied considerably among localities within each island. However, significantly higher percentages of C. rugosus reached age 3 years on Dongsha than at Siziwan bay in Taiwan. Two growth rate indices inferred from size structures suggested faster growth on Dongsha than at Siziwan. The condition index (i.e., the body mass/shield length ratio of C. rugosus) was also greater on Dongsha than at Siziwan. Therefore, Dongsha hermit crabs seem to have superior diet and growth performance. Seagrass debris accumulation at the shore of Dongsha was considerable, whereas none was observed at Siziwan or on the other islands, where dicot leaves were the dominant food item for the vegetarian hermit crabs. We then experimentally evaluated the possible role of seagrass as food for C. rugosus. The crabs on Dongsha preferred seagrass to dicot leaves, and their growth increment was faster when they fed on seagrass than when they fed on dicot leaves; no such differences were found in the Siziwan hermit crabs. The aforementioned results are compatible with the food hypothesis explaining the size differences among the islands. The predator hypothesis could explain the greater life span but not the other findings. Populations of C. rugosus on islands with seagrass debris piles probably contribute more to the gene pool of the species because higher proportions of these populations could achieve high fecundity. The fate of these terrestrial hermit crabs may rely on the health of underwater seagrass ecosystems that are under threat from global change. Public Library of Science 2017-04-07 /pmc/articles/PMC5384810/ /pubmed/28388638 http://dx.doi.org/10.1371/journal.pone.0174319 Text en © 2017 Hsu, Soong http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Research Article
Hsu, Chia-Hsuan
Soong, Keryea
Mechanisms causing size differences of the land hermit crab Coenobita rugosus among eco-islands in Southern Taiwan
title Mechanisms causing size differences of the land hermit crab Coenobita rugosus among eco-islands in Southern Taiwan
title_full Mechanisms causing size differences of the land hermit crab Coenobita rugosus among eco-islands in Southern Taiwan
title_fullStr Mechanisms causing size differences of the land hermit crab Coenobita rugosus among eco-islands in Southern Taiwan
title_full_unstemmed Mechanisms causing size differences of the land hermit crab Coenobita rugosus among eco-islands in Southern Taiwan
title_short Mechanisms causing size differences of the land hermit crab Coenobita rugosus among eco-islands in Southern Taiwan
title_sort mechanisms causing size differences of the land hermit crab coenobita rugosus among eco-islands in southern taiwan
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5384810/
https://www.ncbi.nlm.nih.gov/pubmed/28388638
http://dx.doi.org/10.1371/journal.pone.0174319
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