The parasitoidOoencyrtus nezarae (Hymenoptera: Encyrtidae) prefers hosts parasitized by conspecifics over unparasitized hosts

Summary Two laboratory experiments were conducted to examine the ovipositional preferences of the egg parasitoidOoencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) for parasitized and unparasitizedMegacopta punctatissimum Montandon (Hemiptera: Plataspidae). Females that had never oviposited or that had not oviposite for 3 days preferred recently parasitized hosts more than unparasitized hosts. The preference for recently parasitized hosts appeared to be mediated by the punctures in already parasitized hosts made by the ovipositor of the first female. Survival of the parasitoid progeny was lower in recently parasitized hosts than in unparasitized hosts. However, handling time of parasitized hosts was extremely short relative to that of unparasitized hosts, because the superparasitizing female could use the punctures made by the previous females. It is concluded that the females preferred the parasitized hosts over unparasitized hosts because the benefit of saving time and energy for drilling was more than the cost of progeny survival.     

Lectin binding sites on head structures of the spermatid and spermatozoon of the mosquito Culex quinquefasciatus (Diptera,Culicidae)

The presence of intranuclear and acrosomal lectin binding sites in spermatids and spermatozoa of the mosquito Culex quinquefasciatus was analysed. Direct and indirect lectin-gold techniques were used on LR White-embedded cells. The nuclear compartment was the structure most intensely labelled. Early spermatid nucleus showed moderate labelling for peanut agglutinin (PNA), Griffonia simplicifolia IB4 (GS-IB4) and Ricinus communis agglutinin (RCA), and light labelling for the other lectins tested. The sperm nucleus was intensely labelled by all lectins. The acrosome, an enzyme-containing structure, was labelled by some lectins. The anterior acrosomal region was labelled by PNA, while the proximal acrosomal region was labelled by PNA and G. simplicifolia II (GS II) lectins, and showed the presence of fucose residues with the use of Ulex europaeus I (UEA-I) lectin. The spermatozoa stored in the spermatheca showed the same pattern of labelling as that observed in spermatozoa localized in testis and seminal vesicles for all lectins tested. Carbohydrate residues in the nuclear compartment may be involved with the process of chromatin condensation. In the acrosomal region these residues may play a role in the process of spermoocyte interaction.     

Effect of endurance training and chronic isoproterenol treatment on skeletal muscle sensitivity to norepinephrine

The purpose of this study was to determine the influence of metabolic stresses, such as endurance training and chronic isoproterenol treatment, on skeletal muscle sensitivity to norepinephrine. Using an isolated perfused rat hindlimb preparation, dose-response curves for skeletal muscle oxygen consumption (VO2) and vascular resistance were obtained with control, endurance trained, and isoproterenol treated rats. No significant difference was found between control and experimental groups for non-stimulated VO2. In response to NE infusion, trained rats showed a significantly greater increase in VO2 compared to control rats while the response of the isoproterenol treated rats was of the same magnitude as the one for their respective control rats. At the highest dose of NE infused, the vasopressor response was significantly lower in trained rats compared to control rats. At none of the doses was there a significant difference in the vasopressor response between control and isoproterenol treated rats. These results suggest that repeated exposures to high levels of catecholamines, as produced during endurance training, leads to an increased sensitivity of skeletal muscle to the effect of norepinephrine.     

Performance ofin vitro propagatedAlnus glutinosa (L.) Gaertn. clones inoculated withFrankiae

Summary ThreeAlnus glutinosa (L.) Gaertn. clones, obtained byin vitro propagation techniques, were inoculated with four strains ofFrankia. The ability of these clones to nodulate and fix nitrogen was previously reported; this study deals with the performance of 12 different combinations of pairs of symbionts.Shoot fresh weight, shoot height and collar diameter were measured 60 and 82 days after inoculation. Shoot fresh weight seems to be more sensitive and reliable than the other parameters. Nitrogenase activity, measured by the acetylene reduction assay, was assayed 78 days after inoculation and was consistent with the biomass measurements.Better growth was observed when type N strains were used. Significant growth differences were observed between clones AG-2 and AG-8 on the one hand and clone AG-4 on the other. Thus, the use of genetically defined host plants and microsymbionts permitted the demonstration of significant performance variation even among cloned plants from the same provenance (AG-4 and AG-8).The duration of the experiment influenced the results with differences becoming less significant with time. This might be caused by an external limiting factor such as the pot size, competition for light,etc. But it could also be indicative of differences in nodulation speed among the treatments.     

Statistical mechanics of DNA and protein suitable for computer calculation

The metling behavior of DNA and formation of α-helices and β-strands in protein can be discussed rigorously by statistical mechanical treatment. To do this, however, appropriate formulations are required for fast computer calculation. New formalisms for DNA and protein in terms of recurrence relations suitable for computer calculation are presented.     

Seasonal changes in ovarian state in a eusocial halictine bee,Lasioglossum duplex,based on stages of the oldest oocytes in each ovariole (Hymenoptera: Halictidae)

Summary The changes in ovarian activity in the life cycle of the eusocial halictine beeLasioglossum (Evylaeus) duplex (Dalla Torre) was studied in both queens and workers by examining the stages of the terminal follicle in each of the six ovarioles. By this method, ovarian activities of both queens and workers were more quantitatively determined than by observation of gross ovarian features as usually conducted. Queen ovaries clearly exhibited two active periods, corresponding to the spring solitary phase and the summer eusocial phase, with distinctly greater activity in the latter. In ovaries of overwintering queens oosorption of young follicle was observed. Worker ovaries were found more active in orphan than in queenright colonies. The order of ovarian activity obtained from pooled data, summer queens>spring queens>orphan workers>queenright workers, was also recognized by comparison of individual females. Bionomics of the eusocial halictine beeLasioglossum duplex IX. Contribution No. 3107 from the Inst. Low Temp. Sci.     

On the dynamics of the mass mortality of Diadema antillarum in Barbados

Widespread mortality of the black sea urchin Diadema antillarum occurred in the Caribbean in 1983; beginning in Panama in January, and having its major impact at Barbados in September. Mortality on ten reefs surveyed in Barbados was 93.2%, with the highest being 99.9% and the lowest 86.9%. Mortality on each reef was independent of the pre-mortality density on the reef. Urchins with test diameters between 20 and 40 mm were more severely affected than smaller or larger urchins. Populations on reefs exposed to incoming oceanic water suffered heavier mortality than those on protected reefs. Mean size of urchins was smallest on high density reefs. This may indicate a negative effect of density on urchin growth. At post-mortality densities, urchins may grow faster and reach sexual maturity sooner.     

Distribution of corticotropin-releasing factor in ovine brain determined by radioimmunoassay

We have developed and used a sensitive and specific radioimmunoassay to demonstrate the presence of CRF-like immunoreactivity in extra-hypothalamic areas of ovine brain. Synthetic CRF displaced antibody bound tracer at an ED50 value of 200 pg and there was no cross-reactivity with LHRH, TRH, ACTH, beta-endorphin and several other peptides. Displacement of bound 125I-CRF by brain extracts exhibited curves parallel to synthetic CRF standards. Highest concentrations (1 ng/mg tissue) of CRF-like immunoreactivity were found in the median eminence but surprisingly, high concentrations of CRF-like immunoreactivity were found in frontal, parietal, occipital and particularly temporal areas of cerebral cortex. Much lower concentrations were found in other brain areas including the basal ganglia, limbic system and brain stem.     

Natural mortality at different population densities of a pine shoot moth,Evetria cristata

A field population of Evetria cristata was studied in 10 plots in 1962 and in 6 plots in 1963. These plots were divided into 2 or 3 groups of different population levels of the shoot moth in respective years. The survival of the insect was then analysed in these different groups of plots. The survival rate of E. cristata from eggs to adults in the first generation was found always higher in the group with low population density, which indicates the existence of some factors that affect the population more severely when the insect is more abundant. Lissonota evetriae and Pediobius sp. seemed to have killed more proportion of the hosts where the shoot moth density was high. However, the total effect of the all natural enemies was not always great in the plots with high density of the moth. The survival of the second generation of the moth in 1963 was observed to be much higher at any population level than in the other generations.