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PubMed2005

Germ cell death in the testis and its relation to spermatogenesis in the wax moth, Galleria mellonella (Lepidoptera: Pyralidae), effects of facultative diapause.

The dichotomous spermatogenesis of many Lepidopterans results in the production of two types of sperm: eupyrene sperm possessing a cell nucleus which participates in fertilisation, and apyrene ones, which lose their nuclei during development and whose function remains a mystery. The goal of our study was to analyse spermatogenesis at the end of the larval development of the wax moth, Galleria mellonella, at an optimal temperature of 30 degrees C as well as to describe how they are affected by diapause brought on by a reduction of temperature to 18 degrees C. Spermatogenesis in non-diapausing insects did not differ significantly from that described in other species of Lepidoptera, and any differences found were compared against available literature. Based on the results presented, it may be unequivocally stated that changes in spermatogenesis occur in diapause caused by a suboptimal temperature of 18 degrees C. The main effect of diapause observed in the testes is the degeneration of germ cells, immediately following their differentiation from bipotential spermatocytes. Eupyrene cells seem to reach a more advanced stage of development. Due to the absence of secondary eupyrene spermatocytes in the testis of diapausing insects, it may be surmised that the meiotic divisions, which lead to the formation of secondary spermatocytes and eventually spermatids, do not occur, or are somehow altered. Lastly, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labelling (TUNEL) analyses we performed show that the degenerative changes of eupyrene cells are apoptotic in character.

Adaptation, Physiological↗
PubMed1989

An evaluation of techniques used for the detection of anthelmintic resistance in nematode parasites of domestic livestock.

In vitro and in vivo techniques used for the detection of anthelmintic resistance are reviewed in terms of their versatility, reliability, accuracy, cost and simplicity. The faecal egg count reduction test is considered the most suitable for field screening of resistance but the larval development assay is likely to prove a valuable adjunct in such investigations. Other in vitro techniques, such as egg hatch tests, larval motility and tubulin binding assays are recommended as suitable only for research investigations. Similarly, in vivo procedures such as the critical and controlled anthelmintic efficacy tests are considered to be appropriate only for specific research purposes because of the costs involved in such studies.

Animals↗
PubMed1999

The development of the pressure-bearing tendon of the bullfrog, Rana catesbeiana.

The plantaris longus tendon of the bullfrog is a pressure-bearing tendon and develops a fibrocartilage-like arrangement in the area subjected to compressive forces. The fibrocartilage-like tissue shows some distinct aspects of cellular and fibrillar structure and distribution as compared to the mammalian counterparts. In this work, the development of the plantaris longus tendon was assessed by investigating some of its structural, cytochemical and immunocytochemical aspects in developing tadpoles. The pressure-bearing region is structurally distinct from the tension region as early as at stage 35 of larval development. There is little extracellular matrix in both regions, but the former shows round mesenchymal-like cells with many processes and cell junctions, while the latter is populated by fibroblasts. As development proceeds, the cells in the compression region retract the processes, loose the connections to each other, become rounded and produce abundant proteoglycans and some collagen fibers. Progressively, their organelles become localized in a restricted perinuclear area and are surrounded by a constantly increasing amount of vimentin. The fibroblasts of the tension region produce mostly collagen fibrils, which are packed and aligned to each other. These cells become more elongated and show a diminished cytoplasmic area. The results allow for the conclusion that the compression region does not arise by simple hyperplasia of the peripheral layers of a normal tendon, but from a programmed sequence of developmental steps. This assumption is based on the fact that muscle fibers are still developing when the tendon is already showing a differentiated compression region. We further suggest that mechanical stimulation is a secondary factor most likely associated with the maintenance of the differentiated phenotype of this tendon.

Animals↗
PubMed2006

Developmental plasticity mirrors differences among taxa in spadefoot toads linking plasticity and diversity.

Developmental plasticity is found in most organisms, but its role in evolution remains controversial. Environmentally induced phenotypic differences may be translated into adaptive divergence among lineages experiencing different environmental conditions through genetic accommodation. To examine this evolutionary mechanism, we studied the relationship between plasticity in larval development, postmetamorphic morphology, and morphological diversity in spadefoot toads, a group of closely related species that are highly divergent in the larval period and body shape and are distributed throughout temperate areas of both the New and the Old World. Previous studies showed that accelerated metamorphosis is adaptive for desert-dwelling spadefoot toads. We show that even under common garden conditions, spadefoot toad species show divergent reaction norms for the larval period. In addition, experimentally induced changes in the larval period caused correlated morphological changes in postmetamorphic individuals such that long larval periods resulted in relatively longer hindlimbs and snouts. A comparative analysis of morphological variation across spadefoot toad species also revealed a positive correlation between the larval period and limb and snout lengths, mirroring the effects of within-species plasticity at a higher taxonomic level. Indeed, after approximately 110 Ma of independent evolution, differences in the larval period explain 57% of the variance in relative limb length and 33% of snout length across species. Thus, morphological diversity across these species appears to have evolved as a correlated response to selection for a reduced larval period in desert-dwelling species, possibly diverging from ancestral plasticity through genetic accommodation.

Animals↗
PubMed1996

Temperature-dependent development and survival of the lesser mealworm, Alphitobius diaperinus.

Development, growth and survival of the lesser mealworm, Alphitobius diaperinus (Panzer), were determined at six constant temperatures. No egg hatch or larval development occurred at 17 degrees C. At temperatures of 20, 25, 30, 35 and 38 degrees C the median development times (days), respectively, were for eggs (13.4, 6.0, 4.4, 2.6 and 2.6), larvae (133.0, 46.0, 26.2, 22.4 and 23.9), pupae (17.0, 8.0, 5.5, 4.0 and 4.1), and from oviposition to adult emergence (164.4, 60.2, 37.9, 29.0 and 30.8). The Sharpe & DeMichele (1977) model was used to describe the temperature-dependent development. The mean egg survival (hatching) ranged from 61% to 86%, with lowest hatch at 20 degrees C. Survival of the larvae and pupae ranged from 32% to 73% and from 85% to 95%, respectively, with lowest survival at 20 degrees C. Pupae had significantly lower weights at 35 degrees C and adults at 38 degrees C than at the other temperatures. Female pupae (20 mg) and female adults (16 mg) were significantly heavier than male pupae (17 mg) and male adults (13 mg). Adults (0.5-9 months old) laid 4-7 eggs per female per day at 25 degrees C.

Animals↗
PubMed2005

The unexpected importance of mosquito oviposition behaviour for malaria: non-productive larval habitats can be sources for malaria transmission.

BACKGROUND: Mosquitoes commute between blood-meal hosts and water. Thus, heterogeneity in human biting reflects underlying spatial heterogeneity in the distribution and suitability of larval habitat as well as inherent differences in the attractiveness, suitability and distribution of blood-meal hosts. One of the possible strategies of malaria control is to identify local vector species and then attack water bodies that contain their larvae. METHODS: Biting and host seeking, not oviposition, have been the focus of most previous studies of mosquitoes and malaria transmission. This study presents a mathematical model that incorporates mosquito oviposition behaviour. RESULTS: The model demonstrates that oviposition is one potential factor explaining heterogeneous biting and vector distribution in a landscape with a heterogeneous distribution of larval habitat. Adult female mosquitoes tend to aggregate around places where they oviposit, thereby increasing the risk of malaria, regardless of the suitability of the habitat for larval development. Thus, a water body may be unsuitable for adult mosquito emergence, but simultaneously, be a source for human malaria. CONCLUSION: Larval density may be a misleading indicator of a habitat's importance for malaria control. Even if mosquitoes could be lured to oviposit in sprayed larval habitats, this would not necessarily mitigate -- and might aggravate -- the risk of malaria transmission. Forcing mosquitoes to fly away from humans in search of larval habitat may be a more efficient way to reduce the risk of malaria than killing larvae. Thus, draining, fouling, or filling standing water where mosquitoes oviposit can be more effective than applying larvicide.

Animals↗
PubMed1998

Cardio-respiratory ontogeny during chronic carbon monoxide exposure in the clawed frog Xenopus laevis.

The present study investigates the ontogeny of cardio-respiratory physiology in Xenopus laevis where O2 transport is obstructed. Animals were raised from eggs (NF stage 1) to metamorphic climax (NF stage 63), while maintained either in air or in chronic 2 kPa CO, which functionally ablates O2 transport by hemoglobin (Hb). Whole-animal rate of oxygen consumption (.MO2), whole-body lactate concentration, individual mass, heart rate (fh) and stroke volume (Vs) were measured. Additionally, cardiac output (.Q) and the ratio of the rate of oxygen consumption to the total rate at which oxygen is transported in the blood (.MO2/.QO2) were calculated to determine limitations imparted when O2 transport is impaired. Our data on early development suggest that the onset of convective blood flow occurs prior to the absolute need for convection to supplement diffusive transport. Values for .MO2, whole-body lactate concentration, mass and fh did not differ significantly between controls and CO-exposed animals. However, CO-exposed animals showed a significant (P<0.05) increase in Vs, .MO2/.QO2 and .Q compared with controls. These results indicate that limiting blood O2 transport is not deleterious to metabolism and development as a whole and that convective oxygen transport via Hb is not essential for normal cardiovascular or respiratory function during larval development.

Animals↗
PubMed2002

Effect of temperature on life history of Cirrospilus vittatus (Hymenoptera: Eulophidae), an ectoparasitoid of Phyllocnistis citrella (Lepidoptera: Gracillariidae).

Cirrospilus vittatus is a generalist parasitoid detected on the invading Phyllocnistis citrella 1 yr after the introduction of this pest into Spain in 1993. In this study, the influence of temperature on parasitoid development, survival, and some selected life history parameters was determined. Development times shortened as the temperature increased from 15 to 30 degrees C, but increased between 30 and 35 degrees C. Larval development times varied the greatest over the range of temperatures, whereas egg development varied the least. The estimated upper and lower development thresholds were 38.2 and 8.2 degrees C, respectively, and the maximal developmental rate (8.75 d(-1)) occurred at 31.5 degrees C. The thermal constant was 275.1 +/- 4.6 degree-days. Cirrospilus vittatus appeared to be a synovigenic species. Mean fecundity at 25 degrees C was 39.17 eggs per female, and the oviposition rate fluctuated around five eggs per day. Superparasitism was quite common (42.8%), but fertility was high (85.6%). Immature C. vittatus survival was 58.1%. From these results, an intrinsic rate of increase of 0.126 females per female per day was estimated. Although under typical Mediterranean climatic conditions, development of C. vittatus could continue throughout the year, its reproductive fitness at 25 degrees C is lower than other leafminer parasitoids attacking P. citrella in Spain. These results could account for the progressive displacement observed in field populations occurring between C. vittatus and the predominant indigenous parasitoids of P. citrella, Cirrospilus sp. near lyncus.

Animals↗
PubMedDate not supplied

[Stimulation of egg development in female nematodes by beta-diethylaminoisobutyronitrile].

The biological activity of a new organic compound beta-diethylaminoisobuthironitrile was determined. A new phenomenon for nematodes of open-type larval development (Strongyloid) was found. Alive females of nematodes belonging to the genera Trichostrongylus, Ostertagia, Bunostomum and Haemonchus were treated with 5 volumes-% mixture of the compound with water. The development of eggs of these nematodes in the mother body and output of larvae in female were observed. The larvae lead an active mode of life, feed and are capable of developing. Optimal exposure of females in solution is 4 hours for Haemonchus and Trichostrongylus, 2 hours for Bunostomum, and 3 hours for Ostertagia. Stimulation of egg development in nematodes of semiclose and semi-open types was not observed.

Animals↗
PubMed1982

Effects of rearing temperature on length of larval period and size of adults in Culicoides arakawae and Culicoides maculatus (Dipteria:Ceratopogonidae).

Effects of rearing temperature on the duration of larval period and the wing lengths of adults were studied in a laboratory strain of Culicoides arakawae and in wild-caught C. maculatus fed cultured nematodes of Rhabditis elongata as diets on agar medium. Larvae of each species responded differently to rearing temperature. So that the larval development of C. arakawae adapted to high temperature and of C. maculatus to low temperature. Low temperature increased the duration of larval period considerably in C. arakawae and slightly in C. maculatus. The developmental zero, for both species was found in almost the same range from 15 to 16 degrees C. No pupae were produced in C. arakawae at 35 degrees C and in C. maculatus above 30 degrees C. High temperature, as well as low temperature, induced low efficiency in pupation. The highest percent pupation was seen in both species at 22.5 degrees C. There was a close inverse relationship between the wing length and larval rearing temperature for both sexes of each species.

Animals↗
PubMedDate not supplied

The MR P-type transposable elements and the genetic activities of mutagens and carcinogens in Drosophila melanogaster. I. N,N-Dimethylnitrosamine (DMN).

A technique was developed for the assay of the genetic activities of carcinogens in both the soma and germ line in the course of early larval development and to assess the extent of their modification through the introduction into the genome of the MR IInd autosome P-type transposable elements. The influence of MR on genotoxicity for a given treatment was indicated by the relative frequencies of non-MR (Cy) to MR-carrying sibs emerging within the same cultures. The viable genetic changes in the soma were classified as recombinational or mutational events on the basis of the comparative yields of mosaic sectors in females heterozygous for the markers y w sn carried in standard order (XS) or multiply inverted (XIn) X-chromosomes. The results with this technique are here described for the carcinogen DMN. In the absence of MR, the topical application of DMN induced no larval lethality up to the highest tested doses (20 mM), but raised the yields of the somatic sectors for all the test markers in the emerging females in accordance with a linear dose fit. Comparison of the XS and XIn data indicated that somatic mutagenesis by DMN entailed the induction of recombinational and mutational events in roughly equal proportions. The introduction of MR into the genome, whether patro- or matroclinously, resulted in dramatic and proportionately equivalent enhancements in the activities of DMN, both with respect to the induction of larval lethality and somatic sectoring. These activities increased exponentially with dose, following a 4th-degree polynomial course up to 10 mM, when larval lethality approached 100%. At lower dose levels, the yields of all sector types in the viable females also followed comparable polynomial curves at different heights, except for y sn in the XIn series, where sector recovery remained at the control level throughout the examined dose range. Analysis of the sector size distribution for eye and bristle mosaicism in the XS control and DMN-treated series gave statistically comparable mean values, irrespective of the presence or absence of MR, indicating that DMN alone, or in conjunction with the P elements, did not alter the timing of aberrant clone initiation. In contrast, estimates of the genetic induction events in the somatic primordia with 5 mM DMN indicated greatly increased response in the presence of MR, which was in excess of 20-fold for the mutational changes involving the sn locus.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2002

The terminal nerve in turbot, Psetta maxima: a developmental immunocytochemical study.

The ontogeny and organization of the terminal nerve (TN) during turbot development was studied using an antiserum to neuropeptide Y. First immunoreactive cells were detected in the olfactory placode at hatching time. At 1 day after hatching, a loose group of labeled neurons form an extracranial primordial ganglion of the TN. During the subsequent larval development, more perikarya displaying increased immunoreactivity were found along the course of the olfactory nerve. Moreover, labeled cells cross the meninx of the forebrain gathering in the olfactory bulb of larval turbot. Projections from these cells, directed both to the caudal brain and to the retina, develop when the cells become established in the olfactory bulb. The generation of immunoreactive cells in the olfactory organ extends into the metamorphic period, when a pronounced asymmetry affects the turbot morphology. At this time, the topological location of the immunoreactive cells in the TN becomes distorted. This developmental pattern was compared with those found in other teleosts and in other vertebrates. Preabsorption experiments of anti-neuropeptide Y serum with neuropeptide Y and FMRF-amide suggests that immunoreactive material observed in TN cells was not neuropeptide Y, and raises the possibility that other peptides, e.g. FMRF-amide-like peptides, exist in this neural system.

Animals↗
PubMed1993

Abnormal anaphase resolution (aar): a locus required for progression through mitosis in Drosophila.

We describe a new mitotic locus of Drosophila melanogaster required for the progression through mitosis in the syncytial embryo and in late larval development. The locus aar (abnormal anaphase resolution) maps to the cytological interval 85E7-F16 and was identified by two alleles. The aar1 allele causes pupal lethality. Larval neuroblasts show an elevated mitotic index with high chromosome condensation and stretched and lagging chromatids during anaphase. aar2 produces fully viable but sterile females. aar1/aar2 females lay eggs that develop mitotic figures with similar abnormalities to those observed in neuroblasts. Indirect immunofluorescence of these embryos indicates that the centrosome cycle appears normal, although some abnormal spindle microtubules can be seen during mitosis.

Alleles↗
PubMed1997

Ontogeny of serotonergic neurons in Aplysia californica.

Although the identity, projection patterns, and functions of serotonergic neurons in juvenile and adult Aplysia are relatively well understood, little is known about the development of these cells. We have used light and electron microscopic immunocytochemistry to investigate the genesis, differentiation, identity, and fate of the serotonergic cells in the embryonic, larval, and metamorphic stages of the life cycle of Aplysia. The results indicate that the first serotonergic cells emerge at midembryogenesis and that a total of five cells makes up the entire serotonergic system by hatching. These cells are part of a newly discovered ganglion in Aplysia, called the apical ganglion. This serotonergic system of five cells remains essentially intact throughout larval development. The apical ganglion, together with its serotonergic cells, is resorbed at metamorphosis. A distinct set of serotonergic cells, which begins to emerge by the end of the larval period, is rapidly elaborated during the metamorphic and early juvenile periods to form the adult serotonergic system. These results support the view that the larval and adult forms of the Aplysia nervous system consist of entirely distinct sets of serotonergic cells, each adapted to the stage-specific morphological and behavioral characteristics of the animal.

Animals↗
PubMed2004

Seasonal susceptibility of 'Bartlett' pears to codling moth (Lepidoptera: Tortricidae) infestation and notes on diapause induction.

Seasonal susceptibility of 'Bartlett' pear, Pyrus communis L., to codling moth, Cydia pomonella (L.), infestation, successful completion of larval development after infestation, and the induction of C. pomonella diapause was studied from 1992 through 1995. The seasonal variation in C. pomonella infestation and larval survival were effected by changes in fruit maturity. In late May through mid-June, pears were hard and were not as successfully infested by C. pomonella and produced less larvae compared with fruit later in the season. In late June to mid-July, pears became more suitable for infestation and a greater percentage of the larvae completed their development. In late July through mid-August, pears were susceptible to infestation, but the larvae were less likely to successfully complete development than in the late June to mid-July period due to pear tissue breakdown. From mid-August through September, pears are unsuitable for infestation, and few larvae were produced. When fruit were infested with neonate larvae in late May and mature larvae emerged from the fruit in July, a low percentage of the larvae entered diapause. However, when fruit were infested with neonate larvae in early July and mature larvae emerged from the fruit in early August, the majority of the larvae entered diapause. When fruit were infested with neonate larvae in late July through September and mature larvae emerged from the fruit after mid-August, nearly all C. pomonella larvae had entered diapause.

Animals↗
PubMedDate not supplied

Can an aspect of consciousness be imprinted into an electronic device?

Although quantum mechanics allows consciousness to have some effect on the collapse of wave functions, most conventional scientists expect the effect to be quite small. Their experience with expert systems, computer-aided design, etc., would cause them to deny the possibility that a specific human intention could be imprinted into a simple electronic device via a meditative process and that this device could then influence a target experiment in accordance with the specific intention. Here, via two very different target experiments, that prevailing supposition has been experimentally tested and found to be fallacious! For each target experiment, one starts with two identical physical devices, isolates them from each other and "charges" one with the specific intention for the particular experiment. This charging process involved the services of four highly qualified meditators to imprint the device with the specific intention. The devices were then wrapped in aluminum foil and separately shipped, via Federal Express approximately 2,000 miles to a laboratory where the actual target experiments were conducted by others. For the two experiments, the intentions were (1) to decrease (increase) the pH of water by one pH unit and (2) to increase the ATP/ADP ratio in fruit fly larvae so as to significantly decrease their development time. For (1), changes of 0.5 to 1.0 pH units were achieved while, for (2), reductions of approximately 15 percent in larval development time for the imprinted vs. unimprinted device were observed (p<0.005). From a theoretical perspective, (1) a thermodynamic basis is provided for the effect of intention on both the electrochemical potential and flux of molecular species, (2) a conceptual model for linking subtle domains with the physical domain devices is given, and (3) a conceptual model is also given of how such devices may broadcast specific prime directive information via intention-augmented electromagnetism which can "tilt" chemical reactions in appropriate ways within the target experiment.

Adenosine Diphosphate↗
PubMed1987

Thyroid hormones in blood plasma of developing salmon embryos.

Blood plasma thyroxine (T4) and 3,5,3'-triiodo-L-thyronine (T3) concentrations in developing embryos of chum (Oncorhynchus keta), coho (Oncorhynchus kisutch), chinook (Oncorhynchus tschawytscha), and Atlantic salmon (Salmo salar) were measured by radioimmunoassay between hatching and completion of yolk-sac absorption. Blood sampling was initiated when approximately 50% of the yolk that was present at hatching had been absorbed. At this time blood plasma levels of T4 (7-9 ng/ml) and T3 (1-5 ng/ml) were similar in all species. In embryos of each salmon species blood plasma levels of T4 increased to maximal values (9-16 ng/ml) when both differentiation of the abdominal body wall and absorption of the yolk sac were completed. Blood plasma levels of T3 generally decreased to low or nondetectable values during this time. There was either a trend toward a decrease or a stasis of levels of T4 and at the same time in some species an increase in levels of T3 in the blood plasma following the completion of yolk-sac absorption and the onset of exogenous feeding. These results demonstrate that thyroid hormones are present in the blood of developing teleost embryos. This finding is discussed in light of the possible role of thyroid hormones in control of the embryonic and larval development of fishes.

Animals↗
PubMed1995

Characterisation of an avermectin resistant strain of Australian Haemonchus contortus.

A strain of Haemonchus contortus (CAVR) isolated in Australia was found to be resistant to ivermectin (IVM) with 0.4 mg kg-1 of the anthelmintic failing to significantly reduce worm burdens. Resistance to IVM was sex-influenced in the CAVR strain with adult males showing a greater sensitivity to IVM. Cross resistance to moxidectin was evident with approximately 15% of the population surviving a dose of 0.1 mg kg-1. The free-living stages of the CAVR isolate had a reduced sensitivity to avermectin (AVM) inhibition of development and motility. Similar structure-activity patterns and resistance factors were obtained for a series of related AVMs as inhibitors of larval development and L3 motility in CAVR and White River II, an IVM-resistant H. contortus isolate from South Africa. Further, both isolates were found to be 3 times more sensitive to paraherquamide than a susceptible H. contortus isolate. This suggest that the same resistance mechanism is operating in both isolates. The CAVR strain is susceptible to the benzimidazoles, levamisole and closantel.

Animals↗