Search results for "Larva"
showing 10 items of 632 documents
Molecular and Insecticidal Characterization of a Cry1I Protein Toxic to Insects of the Families Noctuidae, Tortricidae, Plutellidae, and Chrysomelidae
2006
ABSTRACT The most notable characteristic of Bacillus thuringiensis is its ability to produce insecticidal proteins. More than 300 different proteins have been described with specific activity against insect species. We report the molecular and insecticidal characterization of a novel cry gene encoding a protein of the Cry1I group with toxic activity towards insects of the families Noctuidae, Tortricidae, Plutellidae, and Chrysomelidae. PCR analysis detected a DNA sequence with an open reading frame of 2.2 kb which encodes a protein with a molecular mass of 80.9 kDa. Trypsin digestion of this protein resulted in a fragment of ca. 60 kDa, typical of activated Cry1 proteins. The deduced sequen…
Use of Bacillus thuringiensis toxins for control of the cotton pest earias insulana (Boisd.) (Lepidoptera: Noctuidae)
2006
ABSTRACT Thirteen of the most common lepidopteran-specific Cry proteins of Bacillus thuringiensis have been tested for their efficacy against newly hatched larvae of two populations of the spiny bollworm, Earias insulana . At a concentration of 100 μg of toxin per milliliter of artificial diet, six Cry toxins (Cry1Ca, Cry1Ea, Cry1Fa, Cry1Ja, Cry2Aa, and Cry2Ab) were not toxic at all. Cry1Aa, Cry1Ja, and Cry2Aa did not cause mortality but caused significant inhibition of growth. The other Cry toxins (Cry1Ab, Cry1Ac, Cry1Ba, Cry1Da, Cry1Ia, and Cry9Ca) were toxic to E. insulana larvae. The 50% lethal concentration values of these toxins ranged from 0.39 to 21.13 μg/ml (for Cry9Ca and Cry1Ia, …
Role of protozooplankton in the diet of North Sea autumn spawning herring (Clupea harengus) larvae
2022
AbstractThe role of small prey (< 200 µm) in larval marine fish nutrition is largely understudied. Here, we explore the contribution of protozooplankton (PZP 20–200 µm) to larval fish diets, compared to metazoan microzooplankton (MZP 55–200 µm). More specifically, we tested whether the contribution of PZP increased during the low productivity season and decreased as larvae grow. We used North Sea autumn spawning herring (Clupea harengus) as a case study, as it is a key species with high commercial and ecological importance. In autumn and winter, the potential PZP and MZP prey was dominated by cells < 50 µm (mainly Gymnodiniales, Pronoctiluca pelagica,Tripos spp. and Strombidium spp.),…
Ultrastructural changes of the oenocytes of Gryllus bimaculatus DEG (Saltatoria, Insecta) during the moulting cycle
1974
1. The oenocytes of Gryllus bimaculatus are characterized by an abundant smooth-surfaced ER (ATER). In spite of the great cell size the plasma membrane never shows extensive infoldings during the moulting cycle. In addition to mitochondria there are very large numbers of microbodies containing peroxidase but apparently not uricase. Within the second part of the instar the microbodies lie along the clefts which run through the whole cell. 2. The following changes are observed in the course of a moulting cycle: Immediately after hatching the ATER is scarcely developed, some liposomes are located within areas of ATER disappearing some hours later. 20 hours after emergence glycogen deposits app…
Biosynthesis of ecdysones in isolated prothoracic glands and oenocytes of Tenebrio molitor in vitro.
1974
Abstract Isolated prothoracic glands from Tenebrio larvae synthesize in vitro α-ecdysone, but not β-ecdysone from 4-14C-cholesterol. Isolated abdominal oenocytes from the larvae synthesize mainly β-ecdysone, but only little α-ecdysone. When prothoracic glands and oenocytes are cultured together, the α-ecdysone derived from the prothoracic glands is oxidized by the oenocytes to β-ecdysone. The newly synthesized hormones are not stored in the cells, but are secreted into the medium if sufficient amounts of non-labelled hormones are present. If no unlabelled hormones are added to the culture medium, the newly formed hormones are converted to a large extent into polar conjugates.
Woc (without children) gene control of ecdysone biosynthesis in Drosophila melanogaster.
2001
Abstract The first step in ecdysteroidogenesis, i.e. the 7,8-dehydrogenation of dietary cholesterol (C) to 7-dehydrocholesterol (7dC), is blocked in Drosophila melanogaster homozygous woc (without children) third instar larval ring glands (source of ecdysone). Unlike ring glands from wild-type D. melanogaster larvae, glands from woc mutants cannot convert radiolabelled C or 25-hydroxycholesterol (25C) to 7dC or 7-dehydro-25-hydroxycholesterol (7d25C) in vitro, nor to ecdysone (E). Yet, when these same glands are incubated with synthetic tracer 7d25C, the rate of metabolism of this polar Δ5,7-sterol into E is identical to that observed with glands from comparably staged wild-type larvae. The…
The onset of metamorphosis in Tenebrio molitor larvae (Insecta, Coleoptera) under grouped, isolated and starved conditions
1991
Abstract The post-embryonic development of the beetle Tenebrio molitor presents a variable number of larval instars. Several parameters (instar length, time of apolysis and cuticle deposition) were compared during the larval-larval and larval-pupal cycles of mealworms over 50 mg, reared in grouped or isolated conditions. In grouped conditions comparable to mass breeding, larval-larval and larval-pupal apolyses were found to occur at the same time, but instar duration was longer in the case of prepupae. However, isolation was found to accelerate larval-pupal (but not larval-larval) apolyses and to reduce the number of larval instars, whereas starvation inhibited larval-larval (but not larval…
Ecdysteroid titres in a tenebrionid beetle, Zophobas atratus: effects of grouping and isolation.
1997
Metamorphosis in Zophobas atratus is dependent on isolation: when kept in grouped conditions, larvae undergo numerous supernumerary moults, growing in size, without pupating. This beetle thus represents an interesting model for the analysis of possible differences in the endocrine regulation of normal vs. supernumerary larval moults. In this study, the ecdysteroid titres have been analysed in this species, using enzyme immunoassay. The hormonal variations of larvae undergoing normal or supernumerary larval cycles were particularly examined, in either grouped or isolated conditions. Normal larval cycles presented very similar ecdysteroid variations in grouped as well as isolated conditions, …
Solar UV-B radiation affects leaf quality and insect herbivory in the southern beech tree Nothofagus antarctica
2004
We examined the effects of solar ultraviolet-B (UV-B) radiation on plant-insect interactions in Tierra del Fuego (55°S), Argentina, an area strongly affected by ozone depletion because of its proximity to Antarctica. Solar UV-B under Nothofagus antarctica branches was manipulated using a polyester plastic film to attenuate UV-B (uvb-) and an Aclar film to provide near-ambient UV-B (uvb+). The plastic films were placed on both north-facing (i.e., high solar radiation in the Southern Hemisphere) and south-facing branches. Insects consumed 40% less leaf area from north- than from south-facing branches, and at least 30% less area from uvb+ branches than from uvb-branches. The reduced herbivory …
Regulation of Macromolecular Synthesis during Sea Urchin Development
1979
Immediately following fertilization the sea urchin egg enters a period of very rapid cell division that cleaves the egg cell into about one thousand proportionately smaller cells, which form the swimming blastula, i.e. a larval form that is less vulnerable to environmental injuries since it is capable of actively swimming away from them.