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The marine fish spot, Leiostomus xanthurus, was collected from five sites in the lower Chesapeake Bay system representing a gradient of sediment polycyclic aromatic hydrocarbon (PAH) concentrations. The proliferative responses to mitogens by anterior kidney lymphocytes were assessed using [3H]-thymidine uptake by replicating DNA. The data shows two different mitogen-dependent lymphocytic responses as the sediment PAH levels increase at the sampling sites; a suppression of the response to the T cell mitogens, concanavalin A (Con A) and phytohemagglutinin, and a sharp augmentation of the response to B cell mitogen, lipopolysaccharide (LPS), as well as to poke weed mitogen and peanut agglutinin. The magnitude of the lymphoproliferative responses correlated strongly with the total sediment PAH concentrations (r2 greater than 0.8). A similar correlation was also observed with 15 selected individual PAH compounds regardless of their molecular weights. By maintaining the fish in clean York River water for up to 24 weeks, it was possible to reverse the augmented proliferative responses to LPS of fish from all sampling sites and to increase the reduced responses to Con A, in fish from three sites, and partially in two sites where sediments were highly contaminated with PAH. These results suggest that the proliferative responses of fish lymphocytes to mitogens may be a potentially sensitive biomarker of exposure to, and effects of xenobiotics.

In the marine aquaculture industry, photobacteriosis caused by the Photobacterium damselae subspecies piscicida, Phdp is a globally significant disease. A number of clinical photobacteriosis outbreaks among yearling cultured and broodstocks of gilthead sea bream were sampled and submitted to our laboratory during the summer and autumn of 2013. The tissues of infected fish were subjected to an ordinary bacteriological identification and were analyzed using the polymerase chain reaction (PCR) and immunohistochemistry techniques. The results indicated that the selective primers that have been designed for detecting the gene encoding the apoptotic-induced protein, AIP56, represent a powerful tool for sensitive and specific detection of virulent strains of Phdp. AIP56 toxin triggers apoptosis of host macrophages and neutrophils, contributing to the lesions observed during the pathological investigation. Immunohistochemistry allows bacterial identification and antigen expression to be directly correlated to the disease; the immune-positive bacteria were detected in gills, liver, kidneys, spleen, and brain tissues in acute photobacteriosis. These also appeared in the necrotic areas of the granulomas of chronically infected fish. Molecular and immunohistochemical methods were useful as research and diagnostic tools in different stages of the disease; moreover, they appear to have enormous potential in retrospective epidemiological investigations.Photobacteriosis, formerly known as Pasteurellosis, is one of the most threatening bacterial diseases affecting both wild and cultured marine fish species in Europe, Japan, and the Mediterranean region (Andreoni and Magnani 2014) and is caused by Photobacterium damselae subspecies piscicida, Phdp. A variety of temperate marine fish species are affected by this disease, including yellowtail, Seriola quinqueradiata; flounder, Paralichthys olivaceous; red spotted grouper, Epinephelus akaara; striped bass, Morone saxatilis; black sea bream, Mylio

ABSTRACThis study was carried out on 476 wild marine Dusky Grouper (Epinephelus guaza), captured from the West North shore of Mediterranean Sea at Matrouh Governorate from Sept. 2005 to Sept. 2006. The total prevalence of microsporidia among wild Epinephelus guaza fish was found to be 301 (63.23 %). The investigated fish, revealed the presence of cyst-like nodules ( xenomas, 2-4 mm. in diameter) in the gill arches. Each gill arch was infected with (1-5) xenomas and up to 30 nodules per fish. The recovered spores of Glugea anomala appeared as thick walled, uni-nucleated, pear-oval in shape with large vacuole. They measured (3-4 µm) in width and (5-6 µm) in length. The highest prevalence (82.9%) was recorded in summer, while the lowest one (30.33%) was recorded in winter. Presently, the highest infection rate (88.8%) with Glugea anomala was recorded among fish with 200-250g body weight, while the lowest one (43.3%) was recorded among fish of 100-150g body weight. The main histopathological alteration in gills was destruction of gill filaments with degenerative changes and infiltration of mononuclear leukocytes. The water parameters revealed the highest pH (7.3), chloride value (240 mg/L) and the total hardness (290 mg/L) in summer, while the lowest pH (5.7) and the total hardness (217mg/L) were recorded in winter, but the lowest chloride value (122 mg/L) was recorded in autumn.

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