Green algal infection of American horseshoe crab (Limulus polyphemus) exoskeletal structures

Degenerative lesions in the dorsum of the horseshoe crab (Limulus polyphemus) exoskeleton, eyes, arthrodial membrane, and base of the telson were documented in a population of wild caught laboratory animals. The disease can lead to loss of tissue structure and function, deformed shells, abnormal molting, loss of ocular structures, erosion of interskeletal membranes, and cardiac hemorrhage. Microscopy, histopathology, and in vitro culture confirmed the causative agent to be a green algae of the family Ulvaceae. Further research may explain how green algae overcome horseshoe crab innate immunity leading to external and internal damage.

Graphical abstractThe normal chitinous exoskeletal architecture (Ch) of an American horseshoe crab (Limulus polyphemus) is being displaced by columns of green algal cells (A).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Degenerative lesions caused by a green algae are documented in the horseshoe crab (Limulus polyphemus). ► The disease can lead to loss of tissue structure and function. ► Further research may explain how green algae overcome horseshoe crab immunity.