DAO prepress abstract  -  doi: 10.3354/dao01888

ABSTRACT: Morbidity and mortality was observed in a group of 30 reef clams Tridacna crocea that were imported to Florida U.S.A. from a Vietnamese culture facility and held in research facility aquaria. Clinical signs included an incompletely extended mantle, slow mantle responses to stimuli, and sloughing of byssal tissue beginning 2-5 days prior to death. Necropsy findings included emaciation, visceral mass edema, and rare multifocal 1 mm off-white to light tan gill nodules. Histopathology revealed marked inflammation and necrosis within the visceral mass and gills with interstitial edema and atrophy of glandular, gonadal, and muscular tissues. Inflamed tissues contained large numbers of 10-15 µm extracellular round organisms consistent with Perkinsus sp. trophozoites. The organisms often formed clusters of 1-4 cells and were surrounded by a 1-3 µm rim of eosinophilic material variably forming a radiating corona pattern and 3-4 host haemocytes with dense round nuclei. Polymerase chain reaction (PCR) assays indicated the presence of Perkinsus sp. DNA in these animals and species-specific assays indicated the presence of P. olseni, and possibly other Perkinsus sp. but not P. marinus. Identification of Perkinsus sp. other than P. marinus in T. crocea imported from Vietnam confirms that importation of untested and unquarantined ornamental reef clams has possibly allowed incursion of P. olseni into the U.S.A.