Chrysoperla carnea predation on Heliothis virescens larvae parasitized by Microplitis croceipes

Predation by third instar larvae of Chrysoperla (=Chrysopa) carnea (Stephens) (Chrysopidae) did not alter the ratio of unparasitized Heliothis virescens (F.) (Noctuidae) larvae to H. virescens larvae parasitized by Microplitis croceipes (Cresson) (Braconidae) when these second instar larvae were exposed together to the predator on cotton (Gossypium hirsutum L., Malvaceae) in field cages. This indicates that C. carnea larvae did not prefer either parasitized or unparasitized larvae.

---

Prédation par Chrysopa carnea des chenilles d'Heliothis virescens parasitées par Microplitis croceipes

Résumé Les prédations de chenilles d'Heliothis virescens, parasitées ou saines, élevées sur coton (Gossypium hirsutum L.), de la variété Stoneville 213, ont été comparées, dans des cages de 10 m² chacune placées dans la nature. Des chenilles du second stade ont été placées sur des pieds de coton dans 10 cages, à raison de 160 chenilles préalablement exposées à M. croceipes pendant leur premier stade et 40 chenilles saines par cage. Des larves du troisième stade de Chrysopa carnea ont été ajoutées dans 6 cages, à raison de 500/cage, et 4 cages ont servi de témoins pour évaluer les autres causes de mortalité. L'expérience a été répétée 2 fois. Les chenilles d'H. virescens ont été retirées au bout d'un jour dans une expérience et au bout de 2 jours dans l'autre. C. carnea n'a fait aucun choix entre chenilles parasitées ou non; la fréquence moyenne de chenilles parasitées n'a pas présenté de différence significative entre les cages avec ou sans C. carnea. Qui qu'il en soit, C. carnea a réduit significativement la survie des chenilles d'H. virescens parasitées ou non.

     

Effect of Plant Species and Environmental Conditions on Ice Nucleation Activity of Pseudomonas syringae on Leaves

Selected plant species and environmental conditions were investigated for their influences on expression of ice nucleation activity by 15 Pseudomonas syringae strains grown on plants in constant-temperature growth chamber studies. Ice nucleation frequencies (INFs), the fraction of cells that expressed ice nucleation at −5 or −9°C, of individual strains varied greatly, both on plants and in culture. This suggests that the probability of frost injury, which is proportional to the number of ice nuclei on leaf surfaces, is strongly determined by the particular bacterial strains that are present on a leaf surface. The INFs of strains were generally higher when they were grown on plants than when they were grown in culture. In addition, INFs in culture did not correlate closely with INFs on plants, suggesting that frost injury prediction should be based on INF measurements of cells grown on plants rather than in culture. The relative INFs of individual strains varied with plant host and environment. However, none of seven plant species tested optimized the INFs of all 15 strains. Similarly, incubation for 48 h at near 100% relative humidity with short photoperiods did not always decrease the INF when compared with a 72 h, 40% relative humidity, long-photoperiod incubation. Pathogenic strains on susceptible hosts were not associated with higher or lower INFs relative to their INFs on nonsusceptible plant species. The ice nucleation activity of individual bacterial strains on plants therefore appears to be controlled by complex and interacting factors such as strain genotype, environment, and host plant species.     

The structure of the basement membrane of human lymph node high endothelial venules: An ultrastructural, histochemical and immunocytochemical study

Summary The structure of the basement membrane of the high endothelium of reactive human lymph nodes was investigated by techniques selective for carbohydrates (periodic acid-Schiff; critical electrolyte concentration staining with Alcian Blue; lectin histochemistry), specific proteins (immunohistochemistry for laminin and fibronectin) and by conventional techniques of light and transmission electron microscopy. Adjacent small lymphocytes were assigned to B and T cell subsets by use of monoclonal antibodies and they were analysed for non-specific esterase,-glucuronidase,-N-acetylglucaminidase and proteolytic activities. The basement membranes were shown to be distinctive and to contain three layers, of differing laminin, glycosaminoglycan and glycoprotein oligosaccharide content. Certain lymphocytes (probably T) contained enzymes potentially able to degrade some components of these basement membranes.     

Hexavalent capsomers of herpes simplex virus type 2: symmetry, shape, dimensions, and oligomeric status

The structures of the hexavalent capsomers of herpes simplex virus type 2 were analyzed by negative staining electron microscopy of capsomer patches derived from partially disrupted nucleocapsids. Optimally computer-averaged images were formed for each of the three classes of capsomer distinguished by their respective positions on the surface of the icosahedral capsid with a triangulation number of 16; in projection, each capsomer exhibited unequivocal sixfold symmetry. According to correspondence analysis of our set of capsomer images, no significant structural differences were detected among the three classes of capsomers, as visualized under these conditions. Taking into account information from images of freeze-dried, platinum-shadowed nucleocapsid fragments, it was established that each hexavalent capsomer is a hexamer of the 155-kilodalton major capsid protein. The capsomer has the form of a sixfold hollow cone approximately 12 nm in diameter and approximately 15 nm in depth, whose axial channel tapers in width from the outside towards the inner capsid surface.     

Foraging-efficiency-predation-risk trade-off in the grey squirrel

Many animals must often respond to environmental patterns that simulatneously influence both foraging efficiency and predation risk. We noted that grey squirrels (Sciurus carolinensis) sometimes immediately consume food items in areas of relatively great exposure to predators, and at other times carry food items to the safety of a tree prior to consumption. We outlined a hypothesis that the squirrels were somehow trading-off energy intake rate against predation risk. A simple model shows that maximal energetic efficiency is associated with immediate consumption, whereas (under the field conditions studied) carrying items to the safety of trees provides for minimal exposure to predation. Our analysis of the model predicts that the tendency to carry a food item should decrease with distance of food from cover (travel time) and increase with item size (handling time). To test our predictions, we presented free-roaming grey squirrels with patches containing a fixed number of identical food items. We estimated the proportion of items carried to trees before consumption for 12 different combinations of distance to the nearest tree and item size. The results support our hypothesis and indicate that a simple behavioural criterion based solely on foraging rate or time exposed to predators is insufficient to explain the variation in the data.     

An information-theory analysis of task specialization among worker honey bees performing hive duties

Worker honey bees (Apis mellifera) performing field duties are known to possess individual task specializations. However, little evidence has been forthcoming about individual specializations among the younger pre-foraging worker bees performing hive duties. This paper reports results obtained from behavioural observations of worker bees in seven hives. An information-theory analysis of these data reveals that the divergence from independence (D₂) of worker bee identity and behavioural pattern performed has a low value in all of the experimental hives. Young worker bees performing hive duties therefore do not possess detectable individual specializations. Environmental and life-history considerations that may account for this difference in behaviour between field and hive worker bees are discussed.     

Spatial variation in larval concentrations as a cause of spatial variation in settlement for the barnacle,Balanus glandula

Summary Settlement rates of the high intertidal barnacle, Balanus glandula, were monitored at three sites in the rocky intertidal zone in Central California simultaneously with measurements of larval concentrations in the adjacent water column. In both 1983 and 1984, settlement rates onto vacant substrate differed among the sites by nearly two orders of magnitude. For all sampling dates, this spatial variation in settlement mirrored the spatial distribution of Balanus glandula cyprid concentration in the water column. A perfect rank correlation was found between cyprid concentrations near a site and subsequent settlement. A noteworthy observation was that the sites switched rank in their settlement rates from 1983 to 1984. This change in settlement rankings matched a switch in rankings for cyprid concentrations.Settlement itself appears to be an important cause of the spatial pattern of cyprid concentrations. Comparing the rates of settlement to estimates of the number of cyprids available at a site suggests that settlement causes a large drain on the cyprid population as a water mass passes over successive sites. No consistent spatial patterns were found in the distribution of other major plankton groups (calanoid copepods) that are similar in size to Balanus cyprids but do not settle.The large differences in settlement rates among these sites were previously shown to be a leading cause of large differences in the structure of benthic barnacle populations. The close correspondence shown here between these large differences in settlement and differences in larval concentrations suggests that nearshore oceanic processes affecting larval arrival contribute to the control of benthic community structure.     

Monoclonal antibodies to epitopes on different regions of the 200 00 dalton neurofilament protein : Probes for the geometry of the filament

Neurofilaments in mammalian nervous tissues have three subunit proteins. These subunit proteins have apparent molecular masses of 200 (NF200), 150 (NF150) and 68 (NF68) kD. Biochemical assembly studies have indicated that the NF68 protein forms the core of the filament and that the other two proteins are associated proteins. Electron microscopy immunolocalization studies have been performed previously on isolated filaments and on filaments from neurons in culture, and have confirmed the localization of NF68 as a core filament protein and NF200 as a peripheral protein. We have raised two monoclonal antibodies to the NF200 components. Using immunogold labelled protein A, we have been able to localize these antibodies to tissue sections of adult cerebellum at the EM level. With this method, we have found that one of the monoclonal antibodies (NF2) shows a linear arrangement of gold particles directly on the filament, whereas the second monoclonal antibody (NF111) reacts with the filaments to give a periodic arrangement of gold particles. By immunoblotting against chymotryptic fragments of the NF200 protein, we have found that the mAB-NF111 reacts solely with a 160 kD piece, whereas the other monoclonal antibody reacts with both the 160 kD piece and the 40 kD piece. The latter piece was shown to be associated to the filament by binding studies with iodinated NF68. Thus the EM localization studies and the biochemical studies indicate that the two monoclonal antibodies react with different parts of the NF200 molecule, one binding to a part of the molecule which is located closer to the filament, and one to a more peripheral part of the molecule.     

Genetic Variation for the Sex Ratio in NASONIA VITRIPENNIS

We detected genetic variation for the sex ratio in the parasitoid wasp Nasonia vitripennis by analysis of inbred lines and with an artificial selection experiment. Sex ratios differed significantly among five independently isolated lines. Furthermore, sex ratio in broods produced by single females in single hosts shifted from 80-90% female to 50-55% female in 13 to 15 generations in each of two replicate selection lines. The final sex ratios of both selection lines were significantly lower than any of the inbred line sex ratios. Backcrosses revealed that the selection response was due to nuclear genes acting through the female parent. In light of known facultative sex ratio behavior and major genes affecting sex ratio in Nasonia, our results suggest that population and individual sex ratios in this species are molded by processes at both genetic and behavioral levels.     

Photochemical reactions in interstellar grains photolysis of co,NH3, and H2O

A simulation of the organic layer accreted onto interstellar dust particles was prepared by slow deposition of a CO:NH₃:H₂O gas mixture on an Al block at 10K, with concomitant irradiation with vacuum UV. The residues were analyzed by GC-MS, HPLC, and near IR; a reaction pathway leading from NH₃ to complex alcohol, fatty acid, and amide products in 27 stages is postulated. The astronomical relevance and significance of the observations are discussed.