1,721,022 research outputs found
Growth and Development of Cardiochiles-nigriceps Viereck (hymenoptera, Braconidae) Larvae and Their Synchronization With Some Changes of the Hemolymph Composition of Their Host, Heliothis-virescens (f) (lepidoptera, Noctuidae)
No full textLarval development of the parasitoid Cardiochiles nigriceps Viereck occurs in the last instar larva of its host, Heliothis virescens (F.). This allows the parasitoid to exploit the nutritional increase in the biosynthetic activity occurring in the host in preparation for metamorphosis. To understand the biochemical basis of this host parasitoid developmental synchrony, we undertook host ligation studies and analyzed host hemolymph for proteins and glycerol esters. Parasitization affected the biochemical profile of the host. The hemolymph protein concentration of parasitized last instar H. virescens larvae increased through time, whereas unparasitized (control) larvae were characterized by a decrease in the protein titer when they reached the prepupal stage. The effect of parasitism on glyceride titers of host hemolymph was not as pronounced as the effect on proteins. Ligation conducted on 5th instar hosts, which were parasitized as 4th instars, affected parasitoid development in a time-dependent way. The percentage of successfully developing C. nigriceps larvae increased with the increase of the time interval between parasitization and ligation. Ligation performed before day 2 of the 5th larval instar of H. virescens completely inhibited parasitoid development. Ligations that disrupted parasitoid development were associated with a low host hemolymph protein concentration. Parasitoid development was successful when hemolymph protein titer was high, as occurred when ligations were performed after day 3 of the 5th host instar in both control and parasitized larvae. Ligations in both situations resulted in a slight increase in glyceride titers. The results suggest that host proteins and/or some factor(s) associated with them may play a role in parasitoid growth and development. (C) 1993 Wiley-Liss, Inc
Morphology and Ultrastructure of the Serosal Cells (teratocytes) In Cardiochiles-nigriceps Viereck (hymenoptera, Braconidae) Embryos
No full textThe morphogenetic changes of the serosal membrane during embryonic development of Cardiochiles nigriceps Viereck (Hymenoptera : Braconidae) were investigated. Eggs observed soon after oviposition into the natural host Heliothis virescens (F.) (Lepidoptera, Noctuidae) showed a transparent chorion and a uniform texture. After 5 hr, the embryo exhibited a distinct granular appearance and by 12 hr attained the germ band stage. A serosal membrane originated from the anterior pole of the embryo between 14 and 15 hr after the egg was laid, eventually forming with the cells both in the anterior and posterior pole a continuous envelope around the developing embryo. Ultrastructural observations revealed that the serosal cells in contact with the abdominal region of the embryo, beginning 24-25 hr after oviposition, formed a syncytium. However, the syncytial tissue did not extend to the cells around the head and thorax. The serosal cells at both embryo poles increased in size without losing their structural organization, and developed into teratocytes when the larva hatched. In contrast, the serosal cells surrounding the body of the embryo persisted longer on the head and thorax region of the newly hatched larva, while the syncytial tissue degraded more rapidly after hatching. In vitro rearing experiments showed that C. nigriceps embryos removed from parasitized host larvae just before and just after serosa formation, hatched only when the medium used was formulated with the addition of fetal bovine serum. Embryos did not develop or hatch when placed in a serum-free medium. Once the syncytium deriving from the serosal membrane became evident, embryos readily developed and hatched in serum-free media. The results of this study seem to suggest that the serosal embryonic membrane could have a nutritional role for the developing parasitoid embryo
Preliminary-results On Invitro Rearing of the Endoparasitoid Cardiochiles-nigriceps From Egg To 2nd Instar
No full textThe composition of an artificial medium and technical procedures used for in vitro rearing of the endophagous larval parasitoid Cardiochiles nigriceps Viereck (Hymenoptera, Braconidae), from post-germ band egg to the 2nd instar larva, are described. Amino acids, carbohydrates, salts, and vitamins were supplied in defined amounts as an aqueous solution which, when supplemented with 20 mg/ml of bovine albumin, 5 mg/ml of lactalbumin (enzymatic hydrolysate), 20 % (v/v) fetal bovine serum, 20 % (v/v) milk and 10% (v/v) chicken egg yolk, allowed for parasitoid growth and molting to the 2nd instar. Molting to the final instar was never observed
Spiracular glands of Drosophila melanogaster puparia elicit recognition response in Trichopria drosophilae.
No full textPoste
Oviposition behavior of Anaphes iole Girault, an egg parasitoid of Lygus hesperus (Hymenoptera: Mymaridae; Heteroptera: Miridae)
No full textHost searching and handling behavior of the egg parasitoid Anaphes iole Girault toward Lygus Hesperus Knight eggs was observed in the laboratory on fresh green beans. The host eggs are embedded in plant tissues with only the egg cap exposed above the substrate. Three ethograms were developed to describe the behavior of female parasitoids toward healthy eggs, parasitized (marked) eggs, and host oviposition wounds not containing eggs. Females intensely antennated and probed 95% of healthy eggs and 42% of wounds. When oviposition occurred, females marked the host eggs externally and, if reencountered, briefly antennated and then rejected all marked eggs, thus preventing superparasitism. The time spent by parasitoids in each behavioral step when encountering healthy eggs, marked eggs, or wounds was compared. Behavior of naive (1st egg encountered) versus experienced females (later eggs encountered) was also analyzed. Experienced females accepted and handled host eggs more rapidly compared with naive females
Host Regulation Effects On Heliothis-virescens (f) Larvae Induced By Teratocytes of Cardiochiles-nigriceps Viereck (lepidoptera, Noctuidae-hymenoptera, Braconidae)
No full textTeratocytes deriving from the serosal membrane of Cardiochiles nigriceps Viereck, obtained "in vitro" from embryos hatched on a semidefined medium, were injected at different numbers and in different developmental stages of nonparasitized Heliothis virescens (F.) last instar larvae. Host development was affected by teratocyte injections and the responses registered ranged from normal to complete inhibition of pupation, according to the number of teratocytes injected and the developmental stage of the larva at time of injection. Complete pupation failure was observed when teratocytes derived from 4 C. nigriceps embryos were injected into 1st day 5th instar (new-slender stage) host larvae. Complete pupation occurred when teratocytes from 2 embryos were injected into 3rd or 4th day 5th instars (burrow-digging or day 1 cell formation stage). Intermediate responses, such as the formation of pupal cuticle without ecdysis or with only partial ecdysis, were obtained with, intermediate teratocyte numbers, or host developmental stages. All pupae derived from teratocyte injected larvae failed to develop into adults normally obtained from control injected larvae. The larval weight just before pupation was negatively affected only when teratocyte injections were performed on 1st day 5th instar H. virescens larvae. Teratocyte injections altered the hemolymph protein titer to a level similar to that occurring in parasitized larvae. At the same time the ecdysteroid titer was characterized by a late significant increase, which reached values almost 3 times greater than found in normally parasitized larvae, and also surpassed the highest values registered for nonparasitized larvae. Ligation of parasitized larvae between the meso- and metathorax demonstrated that when the prothoracic glands were excluded, there was almost no ecdysteroid production posterior to the ligation. Ligations performed on parasitized larvae to isolate parasitoid eggs before hatching in the last abdominal segments, demonstrated that only virus and venom determined a reduction of the ecdysteroid titer. On the basis of these results the possible role of teratocytes in affecting the biological activity of ecdysteroids is postulated and discussed in a wider context of host-parasitoid physiological interactions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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