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William M. Cowan, Caroline R. Croom, Kirk S. These small clams ranging from 0. The ectosymbiotic crab Dissodactylus mellitae Rathbun, is commonly found on the oral surface of M. This figure appears in colour in the online version of Journal of Molluscan Studies. To answer these questions, we collected a total of sand dollars at three sites on St Catherines Island: North Beach, the Ramp and South Beach described in Prezant et al. St Catherines Island is a barrier island on the coast of Georgia and these sites are spread across about 12 km of coastline.
All collecting was done at low tide in 1—2 m of water. For each sand dollar we recorded the width of the sand dollar, the number of D. We also recorded where on the sand dollar each clam was attached on the fringe, in a lunule, on the aboral surface or on the oral surface. All data were recorded in the field, immediately after lifting the sand dollar from the substrate. This was important as our preliminary observations revealed that the clams released their attachment if the sand dollar was placed in a container and transported any significant distance.
We found a total of clams on sand dollars. Twenty-seven per cent of sand dollars had one or more clams, with a maximum of nine clams observed on one sand dollar. We found a total of D. Sixty-eight per cent of sand dollars had one or more crabs, with a maximum of seven crabs per sand dollar.
Dissodactylus mellitae were found almost exclusively on the oral surface of sand dollars. As clams were rarely observed on the oral surface, the clams and crabs may not have an opportunity to interact. We found no evidence that D. Based on their distinctive overlapping valves Fig.
Adult A. To confirm this hypothesis we sequenced a portion of the mitochondrial cytochrome c oxidase I COI gene from two adult A. Across a bp alignment of these seven sequences, six nucleotide positions were variable. One adult A. The maximum divergence between specimens was 1. Prior to this study there were no A. The closest match was to A. Given the morphological and genetic similarity between these juvenile clams and adult A. We answered the three questions posed above: juvenile clams were commonly found on the fringe and in the lunules of Mellita isometra , their presence was not obviously influenced by the presence of the ectosymbiotic crab Dissodactylus mellitae , and the clams were juvenile Anadara brasiliana.
In Georgia, A. Growth rates of juvenile A. This is consistent with juvenile growth curves for other species of Anadara e. Muthiah et al. Mellita isometra are deposit feeders that move slowly along or just below the surface of sandy substrates. The attachment of juvenile clams to sand dollars may help them avoid burial under shifting sands due to waves and tides. As the sand dollars move laterally across the sand, attachment along the fringe or in a lunule might provide protection from friction with the substrate.
Alternatively, M. It is not clear whether these clams settle onto sand dollars or attach to sand dollars post-settlement.
Further study at different times of the year could identify when this association begins and how long it persists, and close examination of sand dollars in other locations should reveal whether this association is common. Keith-Lucas for supporting our work on St Catherines Island.
Two reviewers provided helpful comments on the manuscript. Google Scholar. Google Preview. Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account. Sign In. Advanced Search. Search Menu. Article Navigation.
Close mobile search navigation Article Navigation. Volume Oxford Academic. Caroline R. Kirk S. Correspondence: K. Zigler; e-mail: kzigler sewanee. Cite Cite William M. Select Format Select format. Permissions Icon Permissions. Open in new tab Download slide. DNA primers for amplification of mitochondrial cytochrome c oxidase subunit I from diverse metazoan invertebrates.
Google Scholar PubMed. The ectosymbiont crab Dissodactylus mellitae -sand dollar Mellita isometra relationship. Google Scholar Crossref. Search ADS. Systematics, phylogeny and biogeography of the genus Mellita Echinoidea: Clypeasteroida.
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A new model of podial deposit feeding in the sand dollar, Mellita quinquiesperforata Leske : the sieve hypothesis challenged. Survey of Ark, Anadara ovalis , Anadara brasiliana and Noetia ponderosa populations in coastal Georgia. Issue Section:. Download all figures. View Metrics. Email alerts Article activity alert. Advance article alerts. New issue alert. Receive exclusive offers and updates from Oxford Academic.
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Anadara brasiliana (Lamarck, 1819)