Pit structure and trophic relationship of the coral pit crab Cryptochirus coralliodytes |
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Authors: | N Simon-Blecher A Chemedanov N Eden Y Achituv |
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Institution: | (1) Department of Life Sciences, Bar Ilan University, Ramat-Gan 52900, Israel, IL |
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Abstract: | Individuals of the pit crabs Cryptochirus coralliodytes Heller inhabit massive corals of the family Faviidae. Their pit walls were observed to be covered by blue-green algae and
fungi. We suggest that the crabs enhance the growth of these algae and fungi with their metabolic excretions, which contain
ammonium. The endolithic algae and the fungi may facilitate the abrasion of the coral skeleton by the crabs, by perforating
it and thus weakening the skeletal structure. Computerized tomography analysis revealed dense skeletal material around the
pits. Transverse sections showed that the calcification around the pit was similar to other parts of the colony, whereas the
macro-architecture was different. Such a difference is the result of the crabs' influence on the corals' living tissue, possibly
on the calicoblast which deposits the coenosteum. Crabs, which were exposed to carbon-labeled corals for 1, 7 and 18 d, accumulated
labeled carbon, indicating transfer of carbon from the coral tissue to the crabs. Histochemical examination of the stomach
and gut of crabs revealed the presence of mucopolysaccharids in the gut, supporting the hypothesis that the crabs eat coral
products. The findings of this study provide additional evidence that C. coralliodytes are parasites and support the general hypothesis that a nutritional relationship may have served as a basis for selection.
Received: 20 October 1998 / Accepted: 29 April 1999 |
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