Photosynthetic carbon dioxide fixation in zooxanthellae

The carbon-fixation patterns of freshly isolated zooxanthellae from the hermatypic coral Acropora formosa were examined during a 15 min exposure to sodium mosa were examined during a 15 min exposure to sodium [¹⁴C]bicarbonate. The labelling pattern during the first 60 s exposure showed that the C₃ carbon-fixation pathway is the major route for photosynthetic carbon fixation in Symbiodinium sp. 3-Phosphoglyceric acid, which constituted >50% of the label after 5 s, steadily decreased over the first 60 s. Hexose phosphates, aspartate, malate and glucose were the other main products during the first 60 s. Over longer periods, significant amounts of the organic acids succinate, aspartate and glutamate were found in the extract along with glucose; but no glycerol.     

Female benefit,male risk: Polyandry in the true armyworm Pseudaletia unipuncta

In Lepidoptera polyandry is common and females may increase their lifetime reproductive output through repeated matings if they acquire essential resources from male ejaculates. However, the paternity of males mating with previously-mated females is far from assured unless sperm precedence is absolute. In this study on the polyandrous armyworm, Pseudaletia unipuncta, we used two strains of male (the black-eyed wild type and a red-eyed homozygous, recessive mutant), mated with red-eyed females, to determine (i) whether male investment has any impact on female reproductive output, and (ii) if females do benefit from multiple matings, to what extent males fertilize the eggs to which they contributed. Multiple mating resulted in a significant increase in both the fecundity and longevity of females. However, the degree of sperm precedence (those eggs fertilized by the second male) varied from 0–100%, but was not affected by either male size or age, or by the duration of copulation. In cases where sperm precedence was <50% (x = 12%) females produced significantly more eggs (1384 versus 940) prior to the second mating than females where sperm precedence was >50% (x = 89%), indicating that the quality of the first mating influenced the fertilization success of the female's second mate.     

Air pollution and agricultural aphid pests. I: Fumigation experiments with SO2 and NO2

A wide range of aphid/host-crop systems was surveyed by means of fumigation experiments in closed chambers for sensitivity to SO(2) and NO(2) at a concentration of 100 nl litre(-1). Aphid performance was measured by the mean relative growth rate (MRGR) of individual aphids. In all cases, except for Acrythosiphon pisum (Harris) on Vicia fabaL., there were increases in the MRGR of the aphids feeding on fumigated plants as compared to clean air controls, both during and post fumigation. The increases in MRGR ranged from 6 to 75%, with the majority falling between 25 and 40%. A. pisum on V. faba showed a consistent negative response, with decreases in MRGR between -9 and -12%. The changes in aohid MRGR were not due to direct effects, as no significant differences in MRGR were observed between fumigated and clean air chambers when aphids were fed on artificial diet sachets during fumigation.     

The short-term partitioning of carbon-14 assimilate between zooxanthellae and polyp tissue in Acropora formosa

The usefulness of Fluorinert for the extraction of Acropora formosa polyp tissue and zooxanthellae was demonstrated. The latter remain intact, with no leakage of metabolites, and the polyp tissue can be extracted in a minimal volume. Intact A. formosa and its isolated zooxanthellae were incubated in the light with sodium [¹⁴C]bicarbonate for 5 s to 15 min and the kinetics of carbon-14 fixation was determined. The isolated zooxanthellae showed a linear response for carbon fixation, whilst the zooxanthellae in the intact association showed a lag period of 1 to 2 min, containing only 12% of the total fixed carbon in the first 1 min. After 10 min, the distribution of fixed carbon between the symbiotic partners was approximately even and the total carbon fixed was in a range similar to that fixed by the isolated zooxanthellae. A pulse-chase experiment showed rapid movement of fixed carbon from the polyp tissue to the zooxanthellae after the 30 s pulse. The paper discusses two possible explanations for the observed results.     

Indirect evidence indicates female semiochemicals release male precopulatory behaviour in the snow crab,Chionoecetes opilio (Brachyura: Majidae)

Summary Experiments were conducted in aquaria to test the hypothesis that females of the snow crab,Chionoecetes opilio, release a sex pheromone to attract mates. Males exhibited significantly increased activity to water from a source aquarium containing recently-moulted pubescent females, egg-stripped multiparous females and recently-moulted immature females than to water from an aquarium containing berried multiparous females, eggs alone, adolescent males or an empty aquarium. Males without their cephalic chemoreceptors maintained low activity levels in the presence of recently-moulted pubescent females, whereas maxilla-ablated males reacted as strongly as intact males. These findings are discussed within the context of the ecdysteroid-sex pheromone hypothesis, proposed by Kittredgeet al. (1971) and Kittredge & Takahashi (1972), but subsequently rejected. We propose that ecdysteroids from both pubescent and multiparous females may elicit male search-and-clasp behaviour inC. opilio and that the reproductive biology of species used to refute the hypothesis was inappropriate to test the role of ecdysteroids as a cue in the mating process.     

Glycerine from biodiesel: The perfect diesel fuel

Glycerine supply currently exceeds its demand by a significant margin as it is formed as by-product in biodiesel production. Different routes for its utilisation are currently being looked into, especially ones that would allow its use as a fuel addition. However these routes are not as energy efficient as its direct combustion.Previously glycerine and other very low cetane number calorific liquids were thought impossible to be used as fuels in compression ignition engines. We have developed a combustion cycle that permits the utilisation of glycerine as a fuel in a compression ignition engine without the need for pilot fuels or cetane improving additives. The paper discusses the results of glycerine combustion in standard unmodified Lister-Petter and Deutz compression ignition engines.     

Linamarase activities in Bacillus spp. responsible for thermophilic aerobic digestion of agricultural wastes for animal nutrition

Thermophilic Bacillus spp. isolated from thermophilic aerobic digestion (TAD) of model agricultural slurry were screened for ability to secret linamarase activity and degrade linamarin, a cyanogenic glycoside toxin abundant in cassava. Screening was performed by both linamarin - picrate assay and by p-nitrophenyl beta-D-glucoside (PNPG) degradation, and results of both assays were related. Linamarase positive isolates were identified as Bacillus coagulans, Bacillus licheniformis and Bacillus stearothermophilus. Enzyme production was growth related and peak production was reached in 48 h in B. coagulans and 36 h in B. stearothermophilus. B. coagulans produced over 40 times greater activity than B. stearothermophilus. Enzyme productivity in shake flask was not strictly related to screening assay result. Crude enzyme of B. coagulans was optimally active at 75 degrees C while that of B. stearothermophilus was optimally active at 80 degrees C and both had optimum activity at pH 8.0. The thermophilic and neutrophilic- to marginally alkaline activity of the crude enzymes could be very useful in the detoxification and reprocessing of cyanogens containing cassava wastes by TAD for use in animal nutrition.