Food composition of crinoids (Crinoidea: Echinodermata) in relation to stalk length and fan density: their paleoecological implications |
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Authors: | Kota Kitazawa Tatsuo Oji Michinari Sunamura |
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Institution: | (1) Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan |
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Abstract: | Crinoids have been diverse organisms in marine epifaunal filter feeding communities at any level of tiering above the substrate
since they appeared in the Ordovician. Feeding is regarded as the most important factor in producing the crinoid tiering,
which is primarily defined by stalk length. The gut contents of five sympatric crinoid species (three isocrines and two comatulids)
were observed, and these were compared with the stalk length and the fan density. We have classified these crinoid species
into four groups based on the stalk length and fan density, e.g., long stalk with low fan density, long stalk with high fan
density, short stalk with low fan density, and short stalk with high fan density. In the gut contents, diatom crusts were
found mainly from species with longer stalks, and chlorophyll-like fluorescent material were only detected from the groups
with a shorter or no stalk. The group with lower fan density contained more inorganic particles than the group with higher
fan density. Therefore, the gut contents and their amounts depend on their stalk lengths and their fan densities. The results
imply that diversified morphologies in the crinoids have evolved through adaptations to different ecological factors such
as difference in their diets. |
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Keywords: | |
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