Intra-tree foraging behavior of Ceratitis capitata flies in relation to host fruit density and quality

We examined the intra-tree foraging behavior of individually-released, wild-population Mediterranean fruit flies (medflies), Ceratitis capitata (Wiedemann), on field-caged host trees bearing each of three different densities (0, 3, or 12 per tree) of non-infested host fruit (kumquat) or each of two levels of fruit quality (12 non-infested fruit or 12 fruit infested with eggs and covered with host marking pheromone). With increasing density of non-infested fruit, medflies tended to remain longer in trees, visit more fruit before leaving, oviposit more often, accept a proportionately smaller number of fruit visited, and emigrate sooner after the last egg was laid (i.e. have a shorter Giving-Up-Time). Medflies spent much less time, oviposited much less often, and exhibited a longer Giving-Up-Time on trees harboring pheromone-marked fruit than non-infested fruit. Variation in temperature within the range at which experiments were conducted (25–36°C) had little detectable influence on foraging behavior. We compare our findings with published findings on the intra-tree foraging behavior of another tephritid fly, Rhagoletis pomonella (Walsh), and with current foraging behavior theory. We discuss implications of our findings with respect to medfly management strategies, particularly fruit stripping in eradication programs and use of synthetic marking pheromone for control.

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Résumé Nous avons étudié le comportement de prospection dans un arbre, de femelles d'une population sauvage de C. capitata, libérées individuellement à l'intérieur de cages contenant des Eriobotrya japonica (kumquat), portant chacun 3 densités différentes de fruits no contaminés (0, 3, 12 par arbre) et chacun 2 niveaux de qualité de fruits: 12 fruits non infestés ou 12 fruits contaminés par des oeufs et recouverts de phéromone de marquage de l'hôte. C. capitata avait terndance à rester plus longtemps dans les arbres, à visiter plus de fruits avant le quitter, à pondre plus souvent, à accepter proportionnellement un nombre plus réduit de fruits déjà visités, à émigrer plus tôt après la ponte du dernier oeuf (c'est-à-dire à présenter un temps d'abandon plus bref), quand la densité des fruits non contaminés augmentait. C. capitata a dépensé beaucoup moins de temps, pondu beaucoup moins souvent, et présenté un temps d'abandon plus long sur les arbres portant des fruits marqués par la phéromone que sur ceux ayant des fruits non contaminés. Les variations de température dans la gamme de cells où les observations ont eu lieu (23–36°C) n'ont eu qu'une faible influence décelable sur le comportement de prospection. Nous avons comparé nos résultats avec ceux publiés sur la prospection à l'intérieur de l'arbre par une autre téphritide (Rhagoletis pomonella) et avec la théorie dominante sur le comportement de prospection. Nous discutons les conséquences de nos résultats sur les stratégies de lutte contre C. capitata, en particulier l'élimination des fruits dans les plans d'erradication et l'utilisation de phéromone synthétique de marquage.

     

Isolation and culture of cells derived from human cerebral microvessels

Summary Microvessels were isolated from non-neoplastic human cerebral cortical fragments resected for treatment of intractable seizure disorder. The microvessels were incubated in modified Lewis medium with 20 or 30% fetal bovine serum. Within 1–2 weeks, two cell populations emerged from the isolates. One type of cells had polygonal morphology, showed density-dependent contact inhibition at confluence in vitro, showed lectin-binding characteristics of endothelium (but only moderate positivity for factor VIII antigen), demonstrated induction of -glutamyl trans-peptidase when exposed to astrocyte-conditioned media, and responded to insulin by a pronounced increase in DNA synthesis. The other variety of cells grew in vitro more slowly in irregular strands separated by clear zones, showed ultrastructural features of smooth muscle, and isoelectric focusing of cell proteins revealed the presence of smooth-musclespecific -isoactin. Both types of cells could be serially subcultured. The ability to isolate and grow the two cell types, tentatively identified as human cerebral microvascular endothelium and smooth muscle, may facilitate studies of human blood-brain barrier function as well as the pathogenesis of cerebral microangiopathies unique to the human brain.Funded by Canadian Heart Foundation, Heart and Stroke Foundation of Ontario and UCLA Biomedical Research Support Grant     

Comparison of different methods of immobilization for lignin peroxidase production by Phanerochaete chrysosporium

Summary Phanerochaete chrysosporium was immobilized in agar, agarose and -carrageenan gel beads, nylon web, and polyurethane foam, and used for the production of lignin peroxidase in shake cultures on a carbon-limited medium. Nylon was found to be the best carrier, with the maximum lignin peroxidase activity (340 U/l) reached on the 7th day. The enzyme production rate was significantly lower with freely suspended mycelial pellets. Both nylon and polyurethane based biocatalysts were active for at least 38 days after the addition of veratryl alcohol. Best results were obtained when a spore inoculum was used instead of day-old pellets. -Carrageenan was found unsuitable as a carrier for lignin peroxidase production.     

Synthesis of the penicillin precursor, δ-(l-α-aminoadipyl)-l-cysteinyl-d-valine (ACV), by an immobilized enzyme preparation

Summary -(l--Aminoadipyl)-l-cysteinyl-d-valine (ACV) synthetase activity has been partially-purified from cell-free extracts of Streptomyces clavuligerus by ammonium sulfate precipitation. The salt precipitated enzyme was immobilized on an anion exchange resin and synthesis of ACV was observed by exposing the immobilized enzyme preparation to a reaction mixture containing l--aminoadipic acid, l-valine and l-cysteine in the presence of appropriate cofactors. Reaction mixtures containing l--aminobutyric acid(aB) in place of l-valine synthesized the ACV analog ACaB. Immobilized ACV synthetase can be reused, and after six cycles of reaction, 28.9% of original activity remains.     

Physiological adaptations of an under-ice population of Pseudocalanus in Barrow Strait (N.W.T) to increasing food supply in spring

Summary Zooplankton and water samples were collected at weekly intervals between April 25 and May 30, 1986 in Barrow Strait, N.W.T. (Canadian Arctic Archipelago). In tows from 0–30 m, the zooplankton community (>202 m) was dominated by Pseudocalanus. The population was apparently growing and developing as shown by an increase in the proportion of adults (stage VI) and decreases in the proportion of stages III, IV, and V as the season progressed. Respiration and excretion rates of the Pseudocalanus populations were probably linked, there being an immediate increase in excretion rate, accompanying an increase in feeding rate when chlorophyll concentrations increased, which was followed by a smaller increase in respiration rate after a time lag. Hence, there was a large decrease in the ON ratio. Increased metabolism coincided with changes in the population structure, as did protease and bodily protein, but could not be clearly linked to dietary acclimation. Only laminarinase activity could be statistically related to an identifiable fraction of potential nutritional value in the water, particulate soluble carbohydrate, but neither showed overall seasonal change.     

Plasmid content and homology of 16 strains of filamentous,nonheterocystous cyanobacteria

We have developed several strain-specific, rapid, small-scale plasmid isolation procedures in order to characterize the plasmid profiles of 16 filamentous, nonheterocstous cyanobacteria. At least one distinct plasmid was found in eight strains, with seven of these containing two or more different plasmids. Eight strains were found to be without plasmid DNA. Both the large, 12.9 kb, and the small, 1.6 kb, plasmids fromPlectonema boryanum 581 were isolated, purified, and cloned. Southern blots of plasmid DNAs from the eight strains were probed with these cloned DNAs and also with ultra-pure plasmid DNA fromPhormidium liridum 426. Four strains ofP. boryanum (485, 581, 594, 1542) andP. luridum 426 have identical plasmid profiles, and plasmid homology is extensive.