Development of a haemolymph profile as an aid for assessing the health status of the American lobster Homarus americanus (H. Milne Edwards)

The North American lobster (Homarus americanus) fishery is valued at hundreds of millions of dollars annually. It is important to assess health status when lobsters are first caught and during storage in lobster pounds as this information can be used in marketing and management decisions. Five haemolymph parameters (total haemocyte count (THC), differential haemocyte count (DHC), plasma phenoloxidase activity, heat precipitatable plasma protein (HHP) and haemolymph total solids (TS) concentration) were evaluated to identify those which could be incorporated into a haemolymph health profile for H. americanus. Experimental infection models of gaffkemia, caused by the Gram positive bacterium Aerococcus viridans, and bumper car disease, caused by the scuticociliate Anophryoides haemophila, were used to assess these parameters.; Haemocytopenia (THC <10 × 109 cells/L) was a consistent finding in the terminal stages of bumper car disease. THCs ranged from <0.1 to 1.5 × 109 cells/L and preceded detection of the ciliate by light microscopic examination of haemolymph. Haemocytopenia was not a consistent finding in the terminal stages of gaffkemia; THCs ranged from 3.6 to 29.4 × 109 cells/L.; After cytocentrifuge preparations of diluted haemolymph were stained with modified Wright-Giemsa, 11 haemocyte types could be identified using the colour, size, shape and number of cytoplasmic granules, nuclear chromatin pattern and nuclear: cytoplasmic ratios as classification criteria. A maturation scheme was proposed based on haemocyte morphology and results of DHCs of lobsters with gaffkemia. The appearance of immature haemocytes in the circulation in the later stages of gaffkemia when numbers of mature haemocytes were decreasing resembled a type of vertebrate inflammatory response.; Phenoloxidase activity was only detected in plasma samples after activation with trypsin and was consequently reported as plasma prophenoloxidase (proPO) activity. A reference interval of <10 milli Optical Density (mOD) units/min was established for plasma proPO in hard shell lobsters. Three lobsters with naturally acquired An. haemophila infections had significantly increased (21.6–81.2 mOD/min) plasma proPO activity. Plasma proPO was increased in the late stages of An. haemophila infection in only three of six lobsters experimentally infected with a laboratory strain of the parasite. (Abstract shortened by UMI.)...