Julia Elena Aizpun de Moreno

Lipid metabolism of the yellow clam,Mesodesma mactroides: 2-Polyunsaturated fatty acid metabolism

The fate of labeled linoleic, α-linolenic, and higher homologs of α-linolenic acid administered to the yellow clam,Mesodesma mactroides, was investigated. It was found that the clam incorporated the acids dissolved in sea water and converted 18∶2 (n−6) into 20∶2 (n−6) and 18∶3 (n−3) into 18∶4 (n−3) and 20∶3 (n−3). The addition of casein hydrolysate to the sea water increased the desaturation capacity of the clam and allowed the conversion of 18∶2 (n−6) into 18∶3 (n−6) to be demonstrated. An enhanced desaturation of 18∶3 (n−3) into 18∶4 (n−3) was also demonstrated. After 12 hr administration of the acid, no radioactivity was found in arachidonic, 20∶5 (n−3), or 22∶6 (n−3). Feeding the clams a culture ofPhaeodactylum tricornutum previously incubated with 1-14C-α-linolenic acid demonstrated that all the homologs of the α-linolenic series were found in the clam without any important changes. Six hour administration of labeled linolenic acid resulted in the incorporation of the acid into diglycerides and phospholipids.

Lipid metabolism of the yellow clam,Mesodesma mactroides: I. Composition of the lipids

The lipid composition of the yellow clam,Mesodesma mactroides, that lives in the northern beaches of the Buenos Aires province of Argentina was studied. The main nonpolar lipids are triglycerides and alkoxyglycerides. Phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl serine are the main phospholipids. The predominant fatty acids are 16∶0, 16∶1ω7, 18∶0, 18∶1ω9, 20∶5ω3, and 22∶6ω3. The are mainly provided by the clams food and stored in the hepatopancreas. The content of polyunsaturated acids increases in summer together with an increase in nonpolar lipids and is correlative with an increase in phytoplankton in the sea water. Sexual maturity modifies the lipid composition of gametes.

Biochemical composition, lipid classes and fatty acids in the ovary of the shrimp Pleoticus muelleri bate

Abstract 1. 1. Seasonal changes in the biochemical composition, lipid classes and fatty acid distribution in the ovary of the shrimp P. muelleri were studied during 1984 and 1985. 2. 2. Neutral lipids were mainly composed by triaclyglycerols, free fatty acids, free and steryl sterols, partial glycerols, pigments, wax esters and hydrocarbons. 3. 3. Polar lipids included mostly phosphatidylcholine, phosphatidylethanolamine, lysoderivatives of choline and ethanolamine, sphingomyelin, pigments and unidentified glycolipids. 4. 4. Major fatty acids were 16:0, 16:1n-7, 18:1n-9, 20:5n-3 and 22:6n-3. The fatty acid composition of neutral lipids varied significantly throughout the year in contrast to that of polar lipids which remained relatively constant. 5. 5. Ovarian maturation during summer involved a simultaneous increase in ovary mass and in protein and lipid concentrations. Fully developed ovaries accumulated polar lipids and tricylglycerols. 6. 6. Palmitic acid (16:0) increased with maturation of the ovary probably as a result of de novo synthesis whereas the levels of 16:1 and 18:1 fatty acids were not significantly changed. 7. 7. After summer spawning the ovary lost large amounts of polar lipids, and in late summer the shrimp intensified feeding, as a result of which neutral lipids accumulated. The ratio of neutral lipids/polar varied from 0.5 in the summer to 2.1 in the autumn. 8. 8. The increase of the polyenoic fatty acids, 20:5n-3 in the spring (ratio 22:6 20:5 = 0.46 ) and 22:6n-3 in the autumn ( 22:6 20:5 = 1.19 ) may be caused by a change in the composition of dietary lipids.

Biosynthesis of unsaturated fatty acids in the diatomPhaeodactylum tricornutum

The biosynthesis of fatty acids in the diatomPhaeodactylum tricornutum was studied. The diatom was incubated with sodium [114C] acetate and the acids [1-14C] palmitic, [1-14C] stearic, [1-14C] linoleic and [1-14C] α-linolenic. The distribution of radioactivity in the products was determined by gas liquid radiochromatography. The diatom synthesized “de novo” not only saturated and monounsaturated fatty acids, but also linoleic, α-linolenic and other fatty acids including the highly polyunsaturated 20∶5ω3 and 22∶6ω3. When labeled acetate, stearic, α-linolenic or even linoleic acid were incubated with the diatom, the polyunsaturated C20 fatty acids synthesized belonged predominantly to the ω 3 family. The existence of Δ9, Δ6, Δ5, Δ4, ω6 and possibly ω3 desaturases inP. tricornutum is suggested.

Fatty acid metabolism in the calanoid copepodParacalanus parvus: 1. Polyunsaturated fatty acids

The metabolic fate of radioactive linoleate and α-linolenate administered to the South Atlantic copepodParacalanus parvus was studied. The wild copepod was able to incorporate the labeled acids dissolved in seawater. The radioactive linoleate was elongated to 20∶2ω6 and 22∶2ω6 and desaturated by a Δ6 desaturase to 18∶3ω6. α-Linolenate was also desaturated by a Δ6 desaturase to 18∶4ω3 and elongated to 20∶3ω3. The copepod was able to convert α-18∶3 to 20∶5ω3 and 22∶6ω3.

Lipid metabolism of the yellow clam,Mesodesma mactroides: 3-saturated fatty acids and acetate metabolism

The fate of labeled palmitate, stearate, and acetate administered to the yellow clam,Mesodesma mactroides, was investigated. 1-14C palmitic and 1-14C stearic acids were oxidized to CO2 to a limited extent. They were mainly incorporated in diacylglycerols and triacylglycerols and were converted to higher homologs. After administration, palmitic acid was converted to stearic and oleic acids, whereas administered stearic acid was converted to 18∶1, 18∶2, 20∶1, and 20∶2 acids. Labeled acetate was readily included by the clam in 12∶0, 14∶0, 14∶1, 15∶0, 16∶1, 16∶1, 16∶2, 18∶2, 18∶1, 18∶2, 20∶1, 20∶2, and 20∶3 acids.

The role of burrowing beds and burrows of the SW Atlantic intertidal crab Chasmagnathus granulata in trapping organochlorine pesticides

The effect of crab beds and bioturbation activity of the SW Atlantic intertidal crab Chasmagnathus granulata on the organochlorine pesticide (OCP) concentrations in Bahía Blanca estuary, Argentina were studied. Total OCP concentration was significantly lower inside than outside the crab burrows. Nevertheless, the concentrations from outside the crab beds were lower than from outside crab burrows, which indicated that crab beds act as sinks of sediment-bound OCP due to the bioturbation activities of the crabs. The same distribution patterns were found in all sediments as well as in crabs, being cyclodienes>HCHs>DDTs, although large amounts of metabolites rather than the respective parental were found in the organism showing the capacity of C. granulata for metabolising parental compounds. These more water-soluble compounds are excreted by the faeces and finally removed by tidal flushing to the sea. Our results suggest that crabs when present play a role in the distribution of sediment-bound OCP and the crab beds are modifiers of the dynamic of organic pollutants in estuarine areas.

Fatty acid metabolism of the calanoid copepodParacalanus parvus: 2. Palmitate, stearate, oleate and acetate

The de novo biosynthesis of fatty acids in the wild, calanoid copepodParacalanus parvus was studied. The incubation of labeled acetate proved the de novo biosynthesis of saturated and monounsaturated even fatty acids from 14 to 20 carbons and the 22∶1 acid. Saturated and monounsaturated uneven fatty acids from 15 to 21 carbons were also synthesized. The copepod could not synthesize linoleic and α-linolenic acids. By administration of [1-14C]palmitate, [1-14C] stearate and [1-14C]oleate, it was possible to elucidate the general pattern of the de novo biosynthesis of fatty acids in the wildP. parvus.

Biochemical composition, lipid classes and fatty acids in the male reproductive system of the shrimp Pleoticus muelleri bate

1. 1. Seasonal changes in the biochemical composition, lipid classes and fatty acid distribution in the male reproductive system (testes + spermatophores) of the shrimp P. muelleri were studied during 1984 and 1985. 2. 2. Male shripms showed a marked homogeneity in the gonad cycle of the population, with a protracted period of sexual maturity. Fully developed testes occurred throughout the year, whereas immature testes were only found in the spring. 3. 3. During spermatogenesis in spring nitrogen content increased ≊ 20% at the expense of water, whereas the mature reproductive system had a relatively constant biochemical composition throughout the year. 4. 4. The male reproductive system index did not constitute a suitable parameter for the estimation of the grade of sexual maturation. Variation in the indices were not correlated to the gonad stage nor to the changes in the biochemical composition. 5. 5. Neutral lipids were mainly composed of free fatty acids, sterols, triacylglycerols and pigments. 6. 6. Polar lipids included mostly phosphatidylcholine, phosphatidylethanolamine and sphingomyelin. Lysoderivatives of choline and ethanolamine and glycolipids were also present as minor components. 7. 7. The male reproductive system is distinctly rich in polyenoic fatty acids, of which 20:5n-3 and 22:6n-3 appear to be required in substantial quantities for a normal reproductive process. The proportion of these fatty acids in the neutral lipids was not significantly affected by the composition of the diet. The ratio 22:620:5 was below 1.0 throughout the year. 8. 8. Biological and biochemical aspects of the male reproductive system are also compared with those of the ovary of this species.

Seasonal variations in the biochemical composition and lipids of muscle and carapace in the shrimp Pleoticus muelleri bate

Abstract 1. 1. Seasonal variations in the biochemical composition and lipids in the muscle and carapace of the shrimp Pleoticus muelleri from San Jorge Gulf, Argentina, were studied during 1984–1985. 2. 2. The biochemical composition of muscle remained fairly constant throughout the year whereas the carapace showed notable seasonal variations. The carapace contained more water and lesser nitrogenous compounds and mineral salts in spring than in the other seasons, with the suggestion of a higher molt frequency in spring. The carapace could have an additional role as a temporary reservoir of nutrients. 3. 3. Polar lipids were the main fraction of total lipids in both muscle and carapace. Phosphatidylcholine, phosphatidylethanolamine, lysoderivatives of choline, sphingomyelin and pigments were identified; ninhydrine positive components with low R f values were also present. 4. 4. Free sterols and free fatty acids were the major neutral lipid classes in both muscle and carapace in spring; the latter had a higher concentration of astaxanthin and small amounts of sterol esters not detected in muscle. 5. 5. The fatty acid composition of polar lipids varied little in muscle. The neutral lipids of maturing females in summer contained higher levels of saturated fatty acids (16:0 and 18:0). The fatty acid composition of carapace varied markedly in polar and neutral lipids. A low selectivity of fatty acids for carapace formation was observed during the year.