The Incorporation of Phenylalanine and Uridine in Tetrahymena: A Pressure Study1

SYNOPSIS. The action of pressure was studied on the incorporation of labelled phenylalanine and uridine, and on the synthesis of water-soluble proteins in heat-synchronized Tetrahymena pyriformis. Incorporation of [¹⁴C] phenylalanine and [³H] uridine into TCA insoluble fractions was markedly decreased in pressuretreated Tetrahymena. Moreover, the incorporation was dependent upon the age of the cells. Water-soluble protein synthesis was unaffected. These results appear consistent with the proposal that pressure-induced division-delays occur by inhibiting the accumulation of “division proteins” which are essential for cell division.     

Nutritional ecology of the interaction between larvae of the gregarious ectoparasitoid, Muscidifurax raptorellus (Hymenoptera: Pteromalidae), and their pupal host, Musca domestica (Diptera: Muscidae)

In this study we examined the relationship between clutch size and parasitoid development of Muscidifurax raptorellus (Hymenoptera: Pteromalidae), a gregarious idiobiont attacking pupae of the housefly, Musca domestica (Diptera: Muscidae). Host quality was controlled in the experiments by presenting female parasitoids with hosts of similar size and age. This is the first study to monitor the development of a gregarious idiobiont parasitoid throughout the course of parasitism. Most female wasps laid clutches of one to four eggs per host, although some hosts contained eight or more parasitoid larvae. In both sexes, parasitoids completed development more rapidly, but emerging adult wasp size decreased as parasitoid load increased. Furthermore, the size variability of eclosing parasitoid siblings of the same sex increased with clutch size. Irrespective of clutch size, parasitoids began feeding and growing rapidly soon after eclosion from the egg and this continued until pupation. However, parasitoids in hosts containing five or more parasitoid larvae pupated one day earlier than hosts containing one to four larvae. The results are discussed in relation to adaptive patterns of host utilization by gregarious idiobiont and koinobiont parasitoids.     

What can the mitochondrial genome reveal about higher‐level phylogeny of the molluscan class Cephalopoda?

We present the first analysis of cephalopod mitochondrial gene order and construct phylogenies based on gene order using Bayesian, distance, and parsimony analysis methods. Analyses included all species of cephalopod for which the whole mitochondrial genome has been sequenced. Where resolution was obtained, these analyses supported division of Neocoleoidea, in which all recent coleoid Cephalopoda can be placed, into Octopodiformes and Decapodiformes. For the same taxa, we also constructed a phylogeny in a maximum likelihood framework based on amino‐acid coded sequence data of all mitochondrial protein coding genes. As well as supporting Octopodiformes and Decapodiformes, amino‐acid analyses established support for Teuthoidea (Oegospida and Myopsida) to the exclusion of Sepiidae, and supported a monophyletic Oegopsida. Partial mitochondrial sequences of additional higher‐level taxa for which whole genome data were not available were subsequently included in the amino‐acid analysis to provide additional information on phylogeny. Spirulida was found to be basal amongst Decapodiformes. Mapping of morphological characters onto our phylogeny and consideration of palaeontological evidence suggests that our phylogeny reflects true evolutionary relationships. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 161 , 573–586.     

Some Other Amazonians: Perspectives on Modern Amazonia

Some Other Amazonians: Perspectives on Modern Amazonia . Stephen Nugent and Mark Harris, eds. London: Institute for the Study of the Americas, 2004. 211 pp.     

Genome‐wide association mapping and biochemical markers reveal that seed ageing and longevity are intricately affected by genetic background and developmental and environmental conditions in barley

Globally, over 7.4 million accessions of crop seeds are stored in gene banks, and conservation of genotypic variation is pivotal for breeding. We combined genetic and biochemical approaches to obtain a broad overview of factors that influence seed storability and ageing in barley (Hordeum vulgare). Seeds from a germplasm collection of 175 genotypes from four continents grown in field plots with different nutrient supply were subjected to two artificial ageing regimes. Genome‐wide association mapping revealed 107 marker trait associations, and hence, genotypic effects on seed ageing. Abiotic and biotic stresses were found to affect seed longevity. To address aspects of abiotic, including oxidative, stress, two major antioxidant groups were analysed. No correlation was found between seed deterioration and the lipid‐soluble tocochromanols, nor with oil, starch and protein contents. Conversely, the water‐soluble glutathione and related thiols were converted to disulphides, indicating a strong shift towards more oxidizing intracellular conditions, in seeds subjected to long‐term dry storage at two temperatures or to two artificial ageing treatments. The data suggest that intracellular pH and (bio)chemical processes leading to seed deterioration were influenced by the type of ageing or storage. Moreover, seed response to ageing or storage treatment appears to be significantly influenced by both maternal environment and genetic background.     

Cross‐species amplification of 105 Lolium perenne SSR loci in 23 species within the Poaceae

Amplification of 105 Lolium perenne SSR markers was studied in 23 grass species representing seven tribes from three subfamilies of Poaceae. Twelve of the SSR markers are published for the first time. Between 2% and 96% of the SSR markers could be amplified within a given species. A subset of eight SSR markers was evaluated for polymorphism across nine of the 23 grass species. Four to seven of the markers were polymorphic within each species, with an average detection of 2.4 alleles per species.     

Effects of experience on parasitoid movement in odour plumes

Abstract. Insects commonly improve the effectiveness with which they locate biotic resources through learning, but the mechanism by which experience exerts its effects has rarely been studied in detail. The effect of oviposition experience on upwind movement of the eucoilid parasitoid, Leptopilina heterotoma (Thomson) (Hym.: Eucoilidae), in odour plumes of host microhabitats, was quantified with the use of a Kramer-type locomotion compensator. A 2h exposure to host Drosophila melanogaster larvae in either fermenting apple-yeast or decaying mushroom substrate (known to affect their preference for these odours in glasshouse and field choice experiments) had a number of effects on movement in plumes of each substrate. Females experienced with a particular substrate walked faster and straighter, made narrower turns and spent more time in upwind movement (i.e. toward the source) in a plume of odour from that substrate than in odour from an alternative substrate. Inexperienced females, by contrast, generally showed little or no significant difference in responses to alternative odours. In addition to affecting the mean values of movement parameters, experience also affected variability around those means. When walking speed or path straightness in an odour plume was increased by experience, variability among individuals was correspondingly decreased. The consequences of odour learning for microhabitat choice is discussed briefly.     

Heavy Water and Hydrostatic Pressure Effects on Tetrahymena pyriformis1

SYNOPSIS. Heat-synchronized cultures of Tetrahymena pyriformis strain GL subjected to pulses of high hydrostatic pressure (10,000 psi for 2 min) had increasing division delays during the 1st 40 min after the last heat shock (40 min after heat treatment). Pressure treatment during the subsequent 10-min interval disrupted cell synchrony. Comparable pressures applied to the cells at later stages, before the 1st synchronous division, caused negligible division delay. Continuous exposure to 10% (v/v) heavy water hardly affected division; higher concentrations delayed or blocked division. Ten-min pulses with heavy water (40%, 50%, 70%) resulted in increasing division delays depending on the stage of the cell cycle during which the heavy water was applied. Amelioration of the division-delaying effects of pressure was observed in cells treated simultaneously with pressure (3,000 psi for 30 min), and 30% D₂O. The results are consistent with the hypothesis that some of the pressure and D₂O effects could be attributed to changes in the sol-gel state of the cytoplasm.