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No description available.

No description available.

Studies on the effect of food quality on the growth dynamics of the copepod <i>Acartia tonsa</i> were conducted using various algal treatments grown under a number of different nutrient regimes. Populations of the copepod <i>A. tonsa</i> were fed algal prey (diatoms <i>Thalassiosira weissflogi </i>and<i> T. pseudonana</i>, prymnesiophyte <i>Emiliania huxleyi</i>, dinoflagellate <i>Aureodinium pigmentosum</i>) grown under different nutrient regimes, in order to study the impact of food quality on production and development throughout the life cycle of the copepod. Changes in predator population structure and biomass were recorded, along with consumption of each of the algal groups, permitting carbon and nitrogen growth efficiencies to be estimated. There was a clear difference in the <i>Acartia tonsa</i> population structure when fed nitrogen-sufficient or nitrogen-deplete prey, with those fed nitrogen-deplete prey slower to develop and reproduce and laying fewer eggs. Algal nutrient status affected selectivity between the diatom and dinoflagellate, the latter being favoured under nutrient-deplete conditions, perhaps in part because their carbon:nitrogen ratio was less susceptible to altered nutrient status. Copepod production was found to be extremely poor when fed diatoms, with lower egg production, poorer hatching success, juveniles smaller and more lethargic and less likely to grow. Although diatoms were found to be nutritionally inferior to the other prey species, even a small proportion of non-diatom (dinoflagellate) had a disproportionately positive effect. Diatoms do therefore have a significant role to play in mixed diets. Growth efficiencies increased with time during the progression to later life history stages, culminating in highest efficiencies during active egg production.

The predominant eicosanoids generated by <i>Balanus perforatus</i> were examined on a monthly basis by reverse phase high pressure liquid chromatography and were identified as 8-hydroxyeicosapentaenoic acid, and 8-hydroxyeicosatetraenoic acid, with their generation correlating with the environmental seawater temperature. No change in either apparent lipoxygenase activity or precursor fatty acid levels were found with the time of year. Changes in fatty acid composition followed the trend expected by homeoviscous adaptation. The subtidal barnacle <i>B. balanus</i> was found to generate an unusual range of products which were tissue-specific in generation, with the testes/seminal vesicles producing large amounts of a novel eicosanoid identified by mass spectrometry as 8,13-dihydroxyeicosapentaenoic acid (diHEPE). This product was highly acid-labile, degrading to a range of unidentified conjugated triene- and pentaene-containing products. Addition of 8,13-diHEPE to excised barnacles increased muscular contractions which is believed to aid in fertilisation. Preliminary results suggest biosynthesis through joint lipoxygenase and cytochrome P450 pathways. The involvement of various eicosanoids, particularly trioxilins and hepoxilins in triggering egg-hatching of <i>Elminius modestus</i> larvae was examined. In contrast to previous reports, trioxilin A₃ was not found to cause egg-hatching, whereas its unstable epoxide precursor, hepoxilin A₃, and the synthetic hepoxilin analogue, PBT-3, did at concentrations of 10^-6and 10^-7 M respectively. Crude barnacle extracts are known to cause an increase in the settlement of <i>B. amphitrite</i>, although in this study crude adult extracts separated by chromatography had no significant effect on levels of settlement, although the precursor fatty acid arachidonic acid caused an increase in settlement. A range of plant-derived terpenoids were found to inhibit settlement of <i>B. amphitrite.</i>

Samples of deep-sea asteroids were collected in a time-series from a station at 2200m in the northern Rockall Trough. These were supplemented by specimens from less regular samplings at other stations. Gametogenic cycles were analysed by determination of gonad and gut caecum indices and oocyte size-frequency distributions and by observations of histology, histochemistry and ultrastructure. Of 15 species examined, 13 showed no reproductive periodicity. Oocytes ranging from prey itellogenic to maximum size are always present in the mature ovary. Size frequency data show a pattern of continuous growth of oocytes with no synchrony between individuals. Fecundity is low and mature oocytes large (c. 1000pm diameter) and yolky, suggesting direct development. Spermatogenesis follows a similar pattern in all these species: mature males are always ripe, ready to shed sperm at any chance encounter with a female. Two species, Plutonaster bifrons and Dytaster insignis, show a contrasting reproductive strategy. They are highly fecund, producing many small (< 120pm) eggs, suggesting planktotrophic larval development. Oocyte size-frequency distributions of P. bifron s indicate a seasonal cycle of gametogenesis with synchrony between individuals and spawning from March to June. Fine structural examination reveals a common structure for somatic portions of the gonads. In seasonally-breeding, species oocytes begin development while unspawned ripe oocytes are being resorbed. Oocyte growth is synchronous and yolk formation begins at c - 40pm diameter. In all a seasonally-breeding species pre-vitellogenic oocytes are very similar. Vitellogenesis begins in the oocyte periphery in different-sized oocytes in the various species. There are differences in the form and numbers of ovarian accessory cells and also in the nature of processes involved in the destruction of excess small oocytes or in the removal of unspawned eggs. Resorption involves phagocytosis or internal degeneration or both. These differences are most marked at family level, suggesting that this strategy has been derived independently in each family. The fine structure of the testes conforms to the basic pattern for asteroids.

Exergonic reactions involving the catabolism of lipids, in particular the fatty acid moieties of triacylglycerols, provide Nasonia vitripennis Walker (Hymenoptera: Pteromalidae) with a major part of the energy required during metamorphosis, odgenesis, host deprivation, and diapause. Flight muscle development is described and flight muscle mitochondriogenesis probably accounts for the increase in phosphoglycerides during the pupal stage and the marked sexual dimorphism in phosphoglyceride metabolism of the flightless male, and the female insect. Palmitic, palmitoleic and oleic acids are preferentially deposited in the triacylglycerols of N. vitripennis and these fatty acids are selectively utilised during metamorphosis, oogenesis, host deprivation and diapause. Phosphoglycerides contain a preponderance of polyunsaturated fatty acids, and in the female insect, large quantities of branched-chain fatty acids. It is thought that the latter are important constituents of flight muscle mitochondria or egg lipids, and may perform functions normally attributed to long chain polyunsaturates. Fatty acid metabolism is markedly influenced by the environment. Parasitoids reared at extremes of temperature contain more unsaturated fatty acids. This is probably a reflection of temperature-dependent anabolic, catabolic and desaturation enzyme systems, but increased unsaturation of membrane lipids at low temperatures would be beneficial and counteract a tendency of decreasing membrane fluidity. Fatty acid composition is also influenced by diet. Certain fatty acids are selectively accumulated or excluded from the tissue lipids of N. vitripennis while the parasitoid duplicates host levels of palmitic, palmitoleic, linolenic and arachidic acids. The degree to which the parasitoid can adapt to its host's fatty acid metabolism, as a factor governing host suitability is discussed. Lipid is accumulated prior to entry into diapause and it is suggested that the accumulation of w 6 series fatty acids, normally excluded from the tissue lipids of N. vitripennis, may be an important factor in diapause induction and maintenance.

The haemolymph of the cockroach, <I>Blaberus discoidalis</I>, contains multiple lectins, designated BDL1, BDL2, BDL3 and GSL, each with different carbohydrate specificities. Both these endogenous, as well as the exogenous lectins, Con A, WGA and HPA, have been shown to induce an enhanced phagocytic response by <I>B. discoidalis</I> plasmatocytes. Thus, the mannose-specific lectins (BDL1 and Con A) both increased the phagocytosis of baker's yeast and <I>Escherichia coli</I>, whereas the G1cNAc/Ga1NAc-specific lectins (BDL2, WGA and HPA) induced the phagocytosis of <I>Bacillus cereus </I>and <I>E. coli. </I>The β-1,3-glucan-specific lectin (GSL) and the Ga1NAc-specific BDL3 only enhanced the phagocytosis of yeast and <I>B. cereus</I>, respectively. The presence of putative receptors for all the phagocytosis-enhancing lectins on the plasmatocytes, was demonstrated using FITC-labelled exogenous lectins to probe the surface of the haemocytes for suitable carbohydrate moieties. When <I>B. cereus</I>, a Gram-positive bacteria, was incubated with an equivalent concentration of lysozyme to that found in the cell-free haemolymph of <I>B. discoidalis</I>, the opsonic activities of BDL1, BDL2 and the exogenous lectins were altered. The G1cNAc-specific lectins, BDL2, WGA and HPA, all exhibited a reduction in the level of enhanced phagocytosis, attributable to the degradation of the peptidoglycan layer surrounding the bacteria, while the mannose-binding lectins, BDL1 and Con A, induced an increase in the phagocytic rate, due to exposure of mannose residues on the surface of <I>B. cereus</I>. These results demonstrate, for the first time in insects, that multiple endogenous lectings, in the cockroach haemolymph are capable of acting as non-self recognition molecules, in a manner analogous to antibodies in the vertebrate immune system.

The effects of cadmium and zinc ions upon the longevity of two freshwater crustaceans, <i>Daphnia pulex</i> (de Geer) and <i>Cyclops fuscus</i> (Jurine) were examined at temperatures (8°C, 14°C, and 21°C). Winter collected speciments of both species were found to be more resistant than summer collected specimens. In both species Cd^++ was more resistant than Zn^++ and resistance to both metal ions was greater in <i>C.fuscus</i> than in <i>D.pulex</i>. Temperature has a synergistic effect on the toxicity of both metals to both species. The pH influence on the toxicity of Cd^++ and Zn^++ to <i>D.pulex</i> was examined. The toxicity of both metals increased with increasing acidity. Acidity alone was lethal to <i>D.pulex</i> with no Cd^++ or Zn^++ added. Cadmium and zinc were accumulated by <i>D.pulex</i> to high concentrations in proportion to time and concentration in solutions. Cadmium accumulations were lower than zinc. The major sites of accumulation, tested using Zn^65 were the gut, hepatopancreas and exoskeleton of <i>D.pulex</i>. The respiratory rate of <i>D.pulex</i> and <i>C.fuscus</i> were affected by the presence of CD^++ and Zn^++, but <i>D.pulex</i> was more affected than <i>C.fuscus</i>, and cadmium effect was generally more than zinc ions. The ultrastructural changes in the hepatopancreas of <i>D.pulex</i> were examined after exposure to cadmium ions. The hepatopancreatic cell was affected. Mitochondria were the most affected organelles.

No description available.