Ž. A spectrophotometric nitroblue tetrazolium NBT reduction assay was used to demonstrate the Ž y . production of superoxide anions O by haemocytes of the white shrimp Penaeus Õannamei. It 2 was found that haemocytes, without receiving an experimental stimulant, showed a rather high Ž background activity. Therefore, optimal parameters number of haemocytes, type of incubation . medium, type and concentration of stimulants were first established, in order to obtain a reliable and reproducible quantitative assay. With this optimized assay, and using specific inhibitors, it was shown that it is indeed the production of O y that was measured. Activities varied strongly 2 among individual shrimp specimens. Live bacteria, among these Vibrio strains, induced O y 2 production in the haemocytes, in a dose-dependent manner. Whereas Vibrio anguillarum and a probiotic strain of V. alginolyticus evoked clear reactions, a pathogenic strain of V. harÕeyi failed to elicit O y production in the haemocytes. It is discussed that this may explain this strain's 2 capability of evading the host's oxidative microbicidal activity, which would be a virulence factor in these bacteria. Heat-killed bacteria hardly induced NBT reduction in the cells. The fungicide propiconazole or Tilt w , found as a pollutant in the aquatic environment where the shrimp are reared, was tested for its effect on NBT reduction by the haemocytes. In haemocytes that did not receive an experimental stimulant, Tilt w induced the reduction of NBT in a dose-dependent manner. In experimentally stimulated haemocytes, however, Tilt w strongly reduced the reaction upon the stimulant PMA. Probable explanations for these seemingly controversial effects of Tilt w are discussed, as are possible consequences of this sort of pollutants for shrimp aquaculture. This easy to perform and relatively cheap and simple quantitative assay for measuring the activity of an oxidative microbicidal mechanism in shrimp haemocytes, appears quite reliable and may therefore prove to be a valuable tool for monitoring shrimp health and immunologic status. q

Mosquitoes, just as other insects produced for the sterile insect technique (SIT), are subjected to several unnatural processes including laboratory colonisation and large-scale factory production. After these processes, sterile male mosquitoes must perform the natural task of locating and mating with wild females. Therefore, the colonisation and production processes must preserve characters necessary for these functions. Fortunately, in contrast to natural selection which favours a suite of characteristics that improve overall fitness, colonisation and production practices for SIT strive to maximize only the few qualities that are necessary to effectively control populations.However, there is considerable uncertainty about some of the appropriate characteristics due to the lack of data. Development of biological products for other applications suggest that it is possible to identify and modify competitiveness characteristics in order to produce competitive mass produced sterile mosquitoes. This goal has been pursued -and sometimes achieved -by mosquito colonisation, production, and studies that have linked these characteristics to field performance. Parallels are drawn to studies in other insect SIT programmes and aquaculture which serve as vital technical reference points for mass-production of mosquitoes, most of whose development occurs -and characteristics of which are determined -in an aquatic environment. Poorly understood areas that require further study are numerous: diet, mass handling and genetic and physiological factors that influence mating competitiveness. Compromises in such traits due to demands to increase numbers or reduce costs, should be carefully considered in light of the desired field performance.

Microbicidal phagocytic function and oxidative metabolism of the hemocytes of 2 oyster species, Ostrea edulis and Crassostrea gigas, were investigated using a luminol-enhanced chemiluminescence (CL) technique. First, experimental parameters adapted to marine bivalve hemocytes were established on hemolymph pools of C. gigas in order to obtain qualitatively and quantitatively homogeneous samples and so to perform statistically comparable assays. The use of Modified Alsever Solution (MAS) allowed hemocytes to b e kept non-aggregated and in a non-stimulated state until starting the assays. A number of aliquots of 2 X lo5 hemocytes with a n MAS final concentration of 3.5 % showed high chemiluminescent response after stimulation by zymosan particles A partic1e:hemocyte ratio of 80:1 gave optimal CL activity. Activity was inhibited by cytochalasin B, a phagocyt~c inhibitor, and by sodlum azide, the latter indicating the involvement of oxygen products. Having thus defined suitable parameter values, the CL protocol was then applled to 0. edulis for qualitative a n d quantitative analyses of respiratory burst capacity at the species and individual levels. Results suggested inter-and intra-specific variability of CL responses. Under the same experimental conditions, 0. eduhs hemocytes generally displayed higher CL activities than C. gigas. Moreover, clear individual vanabllity was demonstrated. The same experimental number of hemocytes showed great differences in CL responses between individuals suggesting a posslble correlation with hemogram characteristics such a s cell type percentages.

No abstract

ABSTRACT. A branchial infection of Pecten maximus is histologically and ultrastructurally described. Gill epithelia1 cells were heavily infected with colonies of procaryotes, believed to belong to the Rickettsiales.In March 1987, a mass mortality (ca 40 O/O) of Pecten maximus from St Brieuc, N Brittany, France, was reported. Collections were made at this site in order to conduct an anatomopathological study, which revealed a procaryotic infection of gill endothelial cells.Materials and Methods. Adult and juvenile scallops were collected by dredging at St Brieuc. Tissues were fixed either in Carson's fixative for light microscopy or in glutaraldehyde 1.25 %/paraformaldehyde 2 % in 0.1 M sodium cacodylate/HCl buffer pH 7.4, followed by 1 % osmium tetraoxide in the same buffer, for transmission electron microscopy (TEM). Osmolarity was raised to 1100 mosm with sucrose (primary fixative) or with sodium chloride (secondary fixative). For light microscopy, samples of gills, digestive gland, mantle, kidney and muscle of a first set of 25 individuals were processed and embedded in paraffin; 3 pm sections were stained with hematoxylin and eosin. A second set of 50 individuals was treated as above except that only gills and digestive gland were examined.For TEM, gill tissues were prepared using an automatic processor and embedded in LX 112. Sections (60 to 90 nm) were contrasted with lead citrate and aqueous uranyl acetate by means of the LKB Ultrostainer. Grids were examined with a Jeol 1200 CX electron microscope.