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.
Immune status of the spiny lobster Jasus edwardsii with tail fan necrosis.
Tail fan necrosis (TFN), a disorder commonly found in some populations of commercially fished and cultured lobsters, is thought to be initiated by injuries caused by handling and containment. The unsightly appearance of affected lobster tails significantly lowers their commercial value. Knowledge about TFN is limited. In this study we describe the morphological features of TFN and apply 6 common methods for evaluating the immune status of wild-caught Australasian red spiny lobsters Jasus edwardsii with and without TFN. The disease was more frequent in uropods than in telsons of the tail fan, and more extensive on the ventral versus the dorsal surfaces of the tail fan. Missing appendages (i.e. antenna, pereiopod or pleopod) were significantly more common and greater in number for individual lobsters affected with TFN versus those without, possibly as a result of handling in the fishery or as an indirect effect of the disease. Two immune parameters, total haemocyte count and phenoloxidase activity in the haemocyte lysate supernatant (HLS), were significantly compromised in lobsters with TFN. No differences were found in the other immune parameters, i.e. haemocyte viability, haemolymph bacterial count and the protein content of haemolymph plasma and HLS. The results are consistent with injury sustained during prior capture and handling that initiates TFN in these natural caught lobsters. These results raise some potential concerns about the fitness of lobsters in natural populations that are affected by TFN, and some potential solutions are proposed.
Turbulent buoyant jets into stratified or flowing ambient fluids
Theoretical and experimental studies were made on two classes of buoyant jet problems, namely: 1) an inclined, round buoyant yet in a stagnant environment with linear density-stratification; 2) a round buoyant jet in a uniform cross stream of homogenous density. Using the integral technique of analysis, assuming similarity, predictions can be made for jet trajectory, widths, and dilution ratios, in a density-stratified or flowing environment. Such information is of great importance in the design of disposal systems for sewage effluent into the ocean or waste gases into the atmosphere. The present study of a buoyant jet in a stagnant environment has extended the Morton type of analysis to cover the effect of the initial angle of discharge. Numerical solutions have been presented for a range of initial conditions. Laboratory experiments were conducted for photographic observations of the trajectories of dyed jets. In general the observed jet forms agreed well with the calculated trajectories and nominal half widths when the value of the entrainment coefficient was taken to be α = 0.082, as previously suggested by Morton. The problem of a buoyant jet in a uniform cross stream was analyzed by assuming an entrainment mechanism based upon the vector difference between the characteristic jet velocity and the ambient velocity. The effect of the unbalanced pressure field on the sides of the jet flow was approximated by a gross drag term. Laboratory flume experiments with sinking jets which are directly analogous to buoyant jets were performed. Salt solutions were injected into fresh water at the free surface in a flume. The jet trajectories, dilution ratios and jet half widths were determined by conductivity measurements. The entrainment coefficient, α, and drag coefficient, Cd, were found from the observed jet trajectories and dilution ratios. In the ten cases studied where jet Froude number ranged from 10 to 80 and velocity ratio (jet: current) K from 4 to 16, α varied from 0.4 to 0.5 and Cd from 1.7 to 0.1. The jet mixing motion for distance within 250D was found to be dominated by the self-generated turbulence, rather than the free-stream turbulence. Similarity of concentration profiles has also been discussed.