Fatty acid compositions of phospholipids and triacylglycerols from selected terrestrial arthropods

Omega-3 polyunsaturated fatty acids in the brain and visual system: Focus on invertebrates

A critical role of omega-3 polyunsaturated fatty acids (PUFA), mainly docosahexaenoic acid 22:6ω3 (DHA), in the development and function of the brain and visual system is well established. DHA, the most abundant omega-3 PUFA in the vertebrate brain, contributes to neuro- and synaptogenesis, neuronal differentiation, synaptic transmission and plasticity, neuronal network formation, memory and behaviour formation. Based on these data, the unique importance of DHA and its irreplaceability in neural and retinal tissues has been postulated. In this review, we consider omega-3 PUFA composition in the brain and retina of various invertebrates, and show that DHA has only been found in marine mollusks and crustaceans. A gradual decrease in the DHA content until its disappearance can be observed in the brain lipids of the series marine-freshwater-terrestrial crustaceans and marine-terrestrial mollusks, suggesting that the transition to the land lifestyle in the evolution of invertebrates, but not vertebrates, was accompanied by a loss of DHA. As with terrestrial crustaceans and mollusks, DHA was not found in insects, either terrestrial or aquatic, or in nematodes. We show that the nervous and visual systems of various DHA-free invertebrates can be highly enriched in alpha-linolenic acid 18:3ω3 or eicosapentaenoic acid 20:5ω3, which affect neurological and visual function, stimulating synaptogenesis, synaptic transmission, visual processing, learning and even cognition. The review data show that, in animals at different levels of organization, omega-3 PUFA are required for the functioning of the nervous and visual systems and that their specific needs can be met by various omega-3 PUFA.

First study on lipid dynamics during the female reproductive cycle of Polybetes pythagoricus (Araneae: Sparassidae)

Spiders are valuable to humans, not only for their role in health but also as biologic pest controllers. In oviparous species, lipids are the main energy source for embryo development and the growth and survival of larvae. Using the spider Polybetes pythagoricus (Holmberg, 1875) as an experimental model, we studied the fluctuations in lipids and fatty acids occurring in tissues related to vitellogenesis. Different reproductive stages (previtellogenesis, early vitellogenesis, vitellogenesis, and postvitellogenesis) were determined histologically. Gonadosomatic and hepatosomatic indices were first used in spiders. The midgut diverticula proved to be the organ with the highest lipid concentration, with triacylglycerols as the major component. Phospholipids were the principal lipids transported. In vitellogenesis, a major accumulation of lipids occurred in the ovary, principally phosphatidylethanolamine (41%); it probably synthesized in the midgut diverticula before being released into the hemolymph for transport and accumulation in the ovary. Phosphatidylethanolamine is possibly involved in maintaining membrane fluidity and in the function of the electron transport chain. The principal fatty acids in the different organs were palmitic, stearic, oleic, and linoleic acids. During vitellogenesis, the ovaries become enriched in polyunsaturated fatty acids. The lipid patterns in the male midgut diverticula, muscle, and hemolymph were similar to those of the previtellogenic or postvitellogenic females.

Fatty acid compositions of Collembola: unusually high proportions of C20 polyunsaturated fatty acids in a terrestrial invertebrate

To examine the C(20) polyunsaturated fatty acid (PUFA) compositions of Collembola, we raised five species of Collembola on yeast diets, and then quantified body mass, neutral lipid fatty acid (NLFA) and phospholipid fatty acid (PLFA) compositions. PLFA content was always less than 5% of dry weight, but NLFA content varied from 5.9% to 29.6% of dry weight, depending upon species. Combined C(20) PUFA proportions of up to 9.2% and 48% were observed in the NLFA and PLFA fractions, respectively, resulting in total C(20) PUFA proportions of up to 19.4% of the total fatty acid compositions of Collembola. C(20) PUFAs were also detected in Collembola specimens from a deciduous woodland at proportions up to 29.7% of the total fatty acid composition. Terrestrial invertebrates generally contain <4% and <22% C(20) PUFAs in PLFAs and NLFAs, respectively; therefore, these results demonstrate that Collembola often possess the highest proportions of C(20) PUFAs yet observed in terrestrial invertebrates. The biochemical reasons for such high C(20) PUFA proportions, which were biosynthesised by the Collembola since these components were absent from the yeast diets, remain unclear. The distinctive fatty acid compositions of Collembola may be useful in soil food web studies utilising fatty acids as biomarkers of trophic behaviour.