Abstract

A group of photosynthetic clams experienced pale white foci on their mantles following arrival at a research setting. The white foci increased in numbers and size during a 7- to 10-day period, resulting in large pale areas representing up to approximately 85% of the mantle surface of some animals. Animals displaying the most rapid and extensive bleaching had a reduced mantle response to stimuli, and several died or were profoundly moribund. Animals with less extensive mantle pallor which tended to be more delayed in onset were more likely to survive. Histopathology and ultrastructural examination revealed a reduction in the number of viable zooxanthellae within the mantle tissues of the host. The pathologic changes and characterization of the degenerating and necrotic zooxanthellae is described for this event. The symbiotic relationship between photosynthetic hosts and their zooxanthellae alga is complex and essential for the host survival. Although bleaching events are well-documented in corals residing in coral reef habitats, bleaching in photosynthetic clam hosts has not been described.^1-3

Acknowledgements

The author wishes to thank Paul Kuipers and Karen Kelley at the University of Florida for their technical contributions.

References

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