Blood lipids in Antarctic and in temperate-water fish species.

Antarctic fish live in very cold water and have adapted to this exceptional environment. Hemoglobin is absent or very low; yet these fish still have erythrocytes, and from these we prepared ghost-like membranes. We studied for the first time the lipid composition of ghost membranes and of plasma in Antarctic fish (C. hamatus and T. bernacchii) and compared our results with those obtained for temperate-water fish (C. auratus and A. anguilla taken from Lake Trasimeno, Perugia, Italy). The membranes of Antarctic fish were richer in glycerophospholipid (especially phosphatidylethanolamine), whereas the membranes of temperate-water fish were richer in sphingomyelin. Unsaturated fatty acids were particularly abundant in Antarctic fish: C. hamatus had long-chain unsaturated fatty acid (especially C22:6 omega-3), whereas T. bernacchii had shorter unsaturated fatty acyl chains (c16:1, omega-7). On the other hand, C. auratus and A. anguilla were particularly rich in C16:0, which constituted more than one-half of the total fatty acid. Plasma lipids (both phospholipid and cholesterol) were much more abundant in temperate-water fish. The differences in phospholipid content were mainly due to choline glycerolipids. Measures of membrane fluidity inferred from the fluorescence anisotropy of DPH indicated that the membranes from Antarctic fish were more fluid at any measured temperature than those obtained from fish living in temperate waters. The ability to live in a very cold environment has therefore been achieved by the two Antarctic species tested in this paper by different strategies, but with the same results on fluidity.

Inflammatory response to Dentitruncus truttae (Acanthocephala) in the intestine of brown trout.

Brown trout, Salmo trutta L., were infected with the acanthocephalan Dentitruncus truttae with the most affected areas being the anterior (near the pyloric caeca) and middle intestine. The parasite attached with a proboscis which usually penetrated the mucosa, lamina propria, stratum compactum, stratum granulosum and, sometimes, the muscularis layer. Around the parasite's body was an area of inflammatory tissue. At the point of attachment the lamina propria was thickened and the stratum compactum, stratum granulosum and muscularis layer were disrupted by proboscis penetration. Rodlet cells were more numerous in infected fish (P<0.01), and were found in the epithelial layer away from the worm. Infected intestines had larger numbers of mast cells (P<0.01), often in close proximity to, and inside, the blood capillaries and associated with fibroblasts of the muscularis layer and the stratum granulosum. Their migration toward the site of infection was suggested. Intense degranulation of mast cells was encountered in all intestinal layers especially near the parasite's body. Immunohistochemical tests were conducted on sections of intestinal tissue of uninfected and infected fish revealing the presence of met-enkephalin and serotonin (5-HT) in immuno-related cells of the intestine wall. Infected trout had larger numbers of elements positive to met-enkephalin and serotonin antisera. These data provided evidence for the role of the immune system of brown trout in the modulation of the inflammatory response to D. truttae. Results are discussed with respect to host immune response to an intestinal helminth.

Ultrastructural study on the body surface of the acanthocephalan parasite Dentitruncus truttae in brown trout.

Scanning electron microscope (SEM) investigations on the holdfast elements, proboscis hooks, and trunk spines of Dentitruncus truttae (Acanthocephala, Palaeacanthocephala), an endoparasite of Salmo trutta (brown trout), provide more data about the surface of these taxonomic relevant structures. In both acanthocephalan sexes, the fully everted cylindrical proboscis possessed 18 longitudinal rows of hooks with 18 hooks per row (rarely 19-20). Hook length varied according to position on the proboscis; apical hooks were 40-52 microm long, middle hooks were 31.7-36.6 microm, and basal hooks were 38.1-40 microm. Starting from the anterior end of the metasoma, numerous cuticular spines (26.7-30 microm in length) were visible and their number progressively decreased posteriorly. SEM observations of D. truttae hooks and spines revealed the presence of many surface striations on each proboscis hook. These surface striations were absent from trunk spines. From the base of the hook, the striations ran parallel toward the point of convergence. Additionally, survey of longitudinal and transversal sections of the hook using transmission electron microscope confirmed that the hook surface was not smooth. SEM comparison with the hooks of several palaeacanthocephalan species, as well as with the hooks of species belonging to Eoacanthocephala and Polyacanthocephala, indicated that the striations are currently exclusive to D. truttae proboscis hooks.