DAO 109:223-230 (2014)  -  DOI: https://doi.org/10.3354/dao02764

Fusarium solani species complex associated with carapace lesions and branchitis in captive American horseshoe crabs Limulus polyphemus

Kathryn A. Tuxbury1,5,*, Gillian C. Shaw2,*, Richard J. Montali2, Leigh Ann Clayton1, Nicole P. Kwiatkowski3, Michael J. Dykstra4, Joseph L. Mankowski2,3,**

1National Aquarium, Department of Animal Health, 501 East Pratt Street, Baltimore, Maryland 21202, USA
2Johns Hopkins University, Department of Molecular and Comparative Pathobiology, 733 N. Broadway, Baltimore, Maryland 21205, USA
3Johns Hopkins Microbiology Laboratory, Department of Pathology, Johns Hopkins University School of Medicine, 600 N. Wolfe Street, Baltimore, Maryland 21287, USA
4North Carolina State University, College of Veterinary Medicine, 1060 William Moore Drive, Raleigh, North Carolina 27607, USA
5Present address: New England Aquarium, 1 Central Wharf, Boston, Massachusetts 02110, USA
*Co-primary authors**Corresponding author:

ABSTRACT: Captive American horseshoe crabs Limulus polyphemus housed at the National Aquarium presented with a variety of shell and gill lesions over a 3 yr period. Carapace lesions were located on both the dorsal and ventral prosoma and opisthosoma and included multifocal circular areas of tan discoloration, ulcerations, and/or pitting lesions, extending from superficial to full thickness. Gill lesions involved both the book gill cover (operculum) and individual book gill leaflets and included multifocal circular areas of tan discoloration, tan to off-white opaque proliferative lesions, and/or areas of black discoloration. Histopathology revealed fungal hyphae, with variable morphology throughout the thickened and irregular cuticle of the carapace and occasionally penetrating into subcuticular tissues, with associated amebocytic inflammation. Book gill leaflets were infiltrated by fungal hyphae and contained necrotic debris and amebocytes. Thirty-eight of 39 animals (97%) evaluated via histopathological examination had intralesional fungal hyphae. Fungal cultures of carapace and gill lesions were attempted in 26 tissue samples from 15 individuals and were positive in 13 samples (50%), with 10 cultures (77%) yielding identification to genus. Fusarium sp. was identified in 8 of the 10 cultures (80%) via culture morphology. The Fusarium solani species complex was confirmed in 6 of these 8 (75%) via polymerase chain reaction amplification of 2 different ribosomal-specific sequences of isolated fungal DNA. Ante-mortem systemic and topical treatments were performed on some affected individuals, but no appreciable change in lesions was observed. Mycotic dermatitis and branchitis are serious health issues for captive American horseshoe crabs.


KEY WORDS: Limulus polyphemus · Fusarium solani · Branchitis · Carapace · Fusariosis


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Cite this article as: Tuxbury KA, Shaw GC, Montali RJ, Clayton LA, Kwiatkowski NP, Dykstra MJ, Mankowski JL (2014) Fusarium solani species complex associated with carapace lesions and branchitis in captive American horseshoe crabs Limulus polyphemus. Dis Aquat Org 109:223-230. https://doi.org/10.3354/dao02764

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