Characterization of chitinolytic bacteria and histological aspects of Shell Disease Syndrome in European spiny lobsters (Palinurus elephas) (Fabricius 1787).
The present research reports the first description of Shell Disease Syndrome in European spiny lobsters Palinurus elephas (Fabricius 1787), which occurred in an experimental aquaculture facility in Sicily (Italy). Both bacterial characterization and histopathological examination of the exoskeleton at site of lesions was carried out. Infected specimens showed tail fan erosions, and in one case uropod ulceration and complete loss of periods. Identified species included: Listonella anguillarum 50.5%, Vibrio parahaemolyticus 27.5% and Vibrio alginolyticus 22%. Microscopic evaluation of lesions indicate the presence of inflammatory responses, which include melanization and pseudomembrane formation, similar to those described for other crustaceans affected by SDS.
Pathology of tail fan necrosis in the spiny lobster, Jasus edwardsii.
Tail fan necrosis (TFN) is the bacterial infection of the tail fan of spiny lobsters which leads to melanosis and erosion of the tail fan tissues. The condition is commonly found among spiny lobsters in aquaculture and commercial fisheries, and greatly reduces their commercial value. This study describes the pathology of TFN by examining the tail fans (telson, uropods) and internal organs (mid-gut, hepatopancreas, heart and gill) of 29 affected wild spiny lobsters (Jasus edwardsii) and 14 unaffected in New Zealand. Initial signs of TFN were observed around the margins of lacerations to the tail fan, with more extensive signs extending from these presumptive sites of initiation. The establishment of the condition at points of injury is consistent with the penetration of TFN through the cuticle and tissue layers of the affected tail fans, which is rarely seen in other forms of shell disease. Entry into these tissues was characterised initially by caseous necrosis and haemocyte accumulation, followed by the spread of these responses together with melanisation. Additional pathological changes to the tail fans included pseudomembrane formation, detachment of epidermis or cuticle, clotted haemolymph and fibrosis. Among internal organs, pathological changes were found in a total of two mid-gut, four heart and two gill samples from eight lobsters with TFN, while no suspected changes were found in the organs of lobsters without TFN. The causes of internal organ pathology associated with TFN in spiny lobsters warrants more detailed research.
A histological study of shell disease syndrome in the edible crab Cancer pagurus.
Shell disease syndrome is characterised by the external manifestation of black spot lesions in the exoskeletons of crustaceans. In the present study, gills, hepatopancreas and hearts from healthy (<0.05% black spot coverage) and diseased (5 to 15% coverage) edible crabs, Cancer pagurus, were examined histologically to determine whether this disease can cause internal damage to such crabs. There was clear evidence of cuticular damage in the gills of diseased crabs leading to the formation of haemocyte plugs termed nodules. Nephrocytes found within the branchial septa of the gills showed an increase in the accumulation of dark material in their vacuoles in response to disease. In the hepatopancreas, various stages of tubular degradation were apparent that correlated with the severity of external disease. Similarly, there was a positive correlation between the number of viable bacteria in the haemolymph and the degree of shell disease severity. Approximately 21% of the haemolymph-isolated bacteria displayed chitinolytic activity. Overall, these findings suggest that shell disease syndrome should not be considered as a disease of the cuticle alone. Furthermore, it shows that in wild populations of crabs shell perforations may lead to limited septicaemia potentially resulting in damage of internal tissues. Whether such natural infections lead to significant fatalities in crabs is still uncertain.