Physiological and biochemical alterations in Littorina saxatilis infected with larval trematodes were investigated and compared with the metabolism of non-parasitized snails. Oxygen consumption rates of infected snails differed from those of non-infected controls in medium sized individuals (30 to 130 mg) but not in very large infected individuals (> 200 mg). Small snails (0.5 to 8.5 mg) were seldom infected by parasites, and this size-class consisted only of non-infected specimens. The specific oxygen consumption rate of infected snails was not dependent on their mass and remained constant over the size ranges investigated. Alterations in the snail metabolism appeared to be connected to injuries to digestive gland tissues caused by the parasites. The glycogen concentration and fatty acids of neutral lipids and phospholipids in the digestive gland were determined. Infected snails differed from uninfected snails in the complete absence of glycogen in digestive gland and had proportionally higher quantities of eicosenoic (20:1) acid in the total phospholipids. It remains unclear whether infection by trematodes activates enzymes in the snail's digestive gland to synthesize eicosenoic (20:1) acid, or whether the sporocysts themselves possess these enzymes. The role of phospholipid fatty acids in the regulation and maintenance of the parasite's metabolism is briefly considered. Biochemical alterations observed in the fatty acid composition may have an adaptive significance, by helping to stabilize the host-parasite system. KEY WORDS: Littorina saxatilis · Metabolism · Trematodes · Digestive gland · Phospholipids · Fatty acids Resale or republication not permitted without written consent of the publisherDis Aquat Org 60: [223][224][225][226][227][228][229][230][231] 2004 tems of Lymnaea stagnalis and cause castration and gigantism in this species (De Jong-Brink 1995). Trematode parasitism does not have a significant effect on the growth rate of Littorina saxatilis but stunts growth in Littorina obtusata, and enhances growth rate and size at maturity in Onoba aculeus (Gorbushin & Levakin 1999). Infected Littorina littorea either show reduced growth, or the parasites do not effect growth rates (Mouritsen et al. 1999). Co-adaptivity within the host-parasite system has been suggested as an explanation for gigantism in parasitized individuals of longlived snail species (Minchella 1985). According to Curtis et al. (2000), however, the oversized snails in long-lived Ilyanassa obsoleta were the result of greater age rather than of faster growth induced by parasites. Thus it is probable that the co-adaptivity theory is not always valid. Most likely, parasites have different effects on growth rate in different species.With regards to energy metabolism, several studies have shown that alterations in oxygen consumption rates in poikilothermic animals induced by parasitic invasion are inconsistent. For example,the presence of larval trematodes in Physa occidentalis induced higher requirements for oxygen in the host (H...

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Abstract— Fatty acid and long‐chain base composition of gangliosides from brains of animals belonging to various vertebrate classes (fishes, amphibia, reptiles, birds and mammals) was studied by gas‐liquid chromatography. Stearic acid was found to be the main fatty acid everywhere. Brain gangliosides of cold‐blooded animals contain lesser amounts of stearic and higher amounts of palmitic and monoenoic acids as compared to those of mammals. Long‐chain bases were separated as trimethylsilyl derivatives. Large amounts (23‐48 per cent) of long chain bases with 20 carbon atoms were found in brain gangliosides of mammals while in those of cold‐blooded animals they constitute 3‐12 per cent of the total. The comparison of the composition of gangliosides with that of cerebrosides and sulphatides indicates, that the fatty acid and long chain base composition of gangliosides from mammalian brain differs from that of other glycosphingolipids, whereas in brains of cold‐blooded animals they are much more similar.

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