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Diseases of Aquatic Organisms

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DAO 43:233-239 (2000)  -  doi:10.3354/dao043233

A new shell disease in the mud crab Scylla serrata from Port Curtis, Queensland (Australia)

Leonie E. Andersen1,*, John H. Norton2, Naomi H. Levy2

1Centre for Environmental Management, Central Queensland University, Gladstone Campus, PO Box 1319, Gladstone, Queensland 4680, Australia
2Queensland Department of Primary Industries, Oonoonba Veterinary Laboratory, PO Box 1085, Townsville, Queensland 4810, Australia

ABSTRACT: In 1994 a previously unreported rust spot shell disease was seen in mud crabs Scylla serrata‹Forskal from Port Curtis, central Queensland, Australia. Of 673 crabs surveyed, 21.7% had shell lesions. Of these, 82.9% had rust spot lesions on the carapace. The majority of rust spot-affected crabs (78.8%) were female. Rust spot lesions were predominantly non-perforated (89.4%) and 54.8% were bilaterally symmetrical. There was also a gender difference in the areas of the carapace most commonly affected. The main histological features of the rust spot lesion included: a cavity in the upper endocuticle; indentation of the endocuticle below the cavity; remains of muscle attachment adhesive epithelium within the cavity; fibrous connective tissue between the damaged carapace and the attached muscle; and islands of endocuticle in this fibrous connective tissue. Histopathology of the internal organs failed to find evidence of an infectious or parasitic cause of the rust spot lesions. The cause(s) of the syndrome appear(s) to be non-infectious.

KEY WORDS: Shell disease · Scylla serrata · Cuticle · Crustacea · Decapoda · Mud crab · Carapace

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