A chemical and histochemical study of the lipides of the pyloric cecum of the starfish,Asterias forbesi

The lipides of the diverticula of Asterias forbesi have been studied by histochemical and biochemical means. Correlations between results obtained by histochemical examination of sections, and chemical analysis of isolated lipide have been made, particularly with respect to phosphatides, steroids, and aldehyde lipides. The results of the histochemical study were in good agreement with the chemical data as to the nature of the phosphatide fraction, the presence of acetone-soluble aldehyde lipides, and the composition of the free droplet fat. Homogenized diverticula were differentially centrifuged in order to establish the distribution of types of lipides in the various cellular components. In addition, data have been presented which demonstrate a direct correlation between the titer of alpha-glycerol ethers and that of acetone-soluble lipide acetals in the unsaponifiable fraction.     

Enhanced lipid production in Nannochloropsis sp. using fluorescence‐activated cell sorting

To advance the utilization of microalgae as a viable feedstock for biodiesel production, the intracellular lipid content of three strains of the marine microalgae Nannochloropsis sp. was enhanced using flow cytometry (FC) coupled with cell sorting. Total lipid content was doubled to 55% (biomass dry weight) in the sorted, daughter cells of Nannochloropsis (strain 47) after consecutive three rounds of cell sorting, and this trait was maintained for approximately 100 subsequent cell generations. In addition, daughter cells had a fatty acid profile similar to that of the parent, wild‐type strain. The study demonstrates that FC coupled with cell sorting is a powerful tool for the enhancement of intracellular lipid content in microalgae exploited for biodiesel feedstock.     

Evaluation of Turtle Exclusion and Escapement Devices for Hoop-Nets

Abstract Baited and unbaited hoop-nets commonly are used to capture catfish in lotic and lentic systems. Turtle bycatch and post-capture mortality has been problematic during catfish surveys in Missouri, USA, most recently in the Gasconade River, Gasconade and Osage counties. We evaluated 3 modified hoop-net designs that would reduce turtle bycatch without reducing catfish capture in the Gasconade River during 15 May-15 July 2006 after pilot study evaluation of 5 hoop-net designs in April 2006. We deployed modified and control-nets in blocks for 48 hours to evaluate differences in turtle and catfish catch rate, as well as abundance, size, and mortality rate of turtle bycatch. The chimney design reduced turtle bycatch by 84% when compared to the control, without decreasing the number or average size of captured flathead catfish (Pylodictis olivaris). Environmental conditions that affected turtle mortality included Secchi disc transparency, temperature, dissolved oxygen, and stream river depth. This is the first known attempt to create turtle exclusion or escapement devices for hoop-nets deployed in freshwater systems. Biologists using hoop-nets to sample aquatic vertebrates in moderate to large river systems will benefit from our study. The application of this methodology will reduce turtle bycatch mortality, especially when sampling is conducted in high water temperatures.     

Host preference and offspring performance are linked in three congeneric hyperparasitoid species

1. The optimisation theory predicts that insect mothers should oviposit on resources on which they attain the highest exclusive fitness. The development of parasitoid wasps is dependent on limited host resources that are often not much larger than the adult parasitoid. 2. In the present study preference and development in three congeneric species of secondary hyperparasitoids attacking cocoons of two congeneric primary parasitoids that differ significantly in size were compared. Gelis agilis (Fabricius) and G. acarorum (L.) are wingless hyperparasitoids that forage in grassy habitats, whereas G. areator (Panzer) is fully winged and forages higher in the canopy of forbs. 3. The three species were reared on cocoons containing pupae of a small gregarious endoparasitoid, Cotesia glomerata (L.), and a larger solitary species, C. rubecula (Marshall), both of which develop in the caterpillars of pierid butterflies. 4. Adult mass was correlated with initial cocoon mass in all three species, whereas development time was unaffected. Wasps were larger when developing in C. rubecula. However, for a given host mass, wasps were larger when developing on the smaller host, C. glomerata. This suggests that there is a physiological limit to hyperparasitoid size that was exceeded when C. rubecula served as host. 5. All three hyperparasitoids strongly preferred to attack cocoons of the larger species, C. rubecula, often avoiding cocoons of C. glomerata entirely. 6. Preference and performance are correlated in the three Gelis species. However, owing to variation in the distribution and thus abundance of their hosts, it is argued that cumulative fitness may be still higher in the smaller host species.     

Intrinsic competition between primary hyperparasitoids of the solitary endoparasitoid Cotesia rubecula

1. In nature, competitive interactions occur when different species exploit similar niches. Parasitic wasps (parasitoids) often have narrow host ranges and need to cope with competitors that use the same host species for development of their offspring. When larvae of different parasitoid species develop in the same host, this leads to intrinsic and often contest competition. Thus far, most studies on intrinsic competition have focused on primary parasitoids. However, competition among primary hyperparasitoids, parasitic wasps that use primary parasitoids as a host, has been little studied. 2. This study investigated intrinsic competition between two primary hyperparasitoids, the gregarious Baryscapus galactopus and the solitary Mesochorus gemellus, which lay their eggs in primary parasitoid larvae of Cotesia rubecula, while those in turn are developing inside their herbivore host, Pieris rapae. The aims were to identify: (i) which hyperparasitoid is the superior competitor; and (ii) whether oviposition sequence affects the outcome of intrinsic competition. 3. The results show that B. galactopus won 70% of contests when the two hyperparasitoids parasitised the host at the same time, and 90% when B. galactopus oviposited first. When M. gemellus had a 48 h head start, the two hyperparasitoids had an equal chance to win the competition. This suggests that B. galactopus is an intrinsically superior competitor to M. gemellus. Moreover, the outcome of competition is affected by time lags in oviposition events. 4. In contrast to what has been reported for primary parasitoids, we found that a gregarious hyperparasitoid species had a competitive advantage over a solitary species.     

Systematic revision of Nearctic species of Achalcus Loew (Diptera: Dolichopodidae) with comments on their phylogeny, ecology and zoogeography

The species of the genus Achalcus Loew from the Nearctic Region are revised and a key to males and females is provided. Achalcus utahensis (Harmston & Miller) and A. oregonensis (Harmston & Miller) are redescribed, and A. californicus sp.n., A. dytei sp.n. and A. similis sp.n. are described. Together with eight of the nine known Palaearctic species of the genus, they represent a monophyletic species group, which is characterized by the presence of five pairs of dorsocentral bristles and the incorporation of the epandrial setae onto the shaft of the epandrial lobe. Like their Palaearctic congeners, most Nearctic species occur in damp habitats, such as coastal forests and riparian vegetation. Most specimens were collected in the Pacific coastal states from British Columbia to California, but one species occurs in Utah, and one of six species which were not described because males are lacking, was discovered in Ontario.