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PubMed2005

Ontogeny of humoral immune parameters in fish.

The first appearance of IgM in lymphocytes varies considerably among fish species. Generally, the first appearance of B-lymphocytes and immunoglobulins is late in marine species compared to fresh water species, and larvae have reached about 20-30 mm in length when IgM is first expressed. Rainbow trout and channel catfish show the first appearances of surface IgM at about 1 week after hatching. Marine species like the sea bass, spotted wolffish and cod show IgM positive lymphocytes 1-10 weeks after hatching. Transfer of maternal antibody to eggs and embryos has been demonstrated in several species. Examples are plaice, tilapia, carp, sea bass and salmon, but not cod. The ontogeny of complement component C3 has been studied in Atlantic halibut (Hippoglossus hippoglossus L.), Atlantic cod (Gadus morhua L.) and the spotted wolffish (Anarhichas minor O.). By Western blotting experiments C3 was found in unfertilised eggs in the spotted wolffish indicating a maternal transfer. RT-PCR analysis revealed C3 mRNA transcripts from 290 degrees in spotted wolffish eggs. Using immunohistochemistry and in situ hybridisation, C3 was found in liver, brain, kidney and muscle of cod larvae 2 days post-hatching and in intestines, pancreas, heart and gills at different stages of larval development. Also, C3 was detectable in halibut larvae in yolk sac, muscle, liver, brain, chondrocytes, spinal chord, eye, heart, intestines and kidney. These studies suggest that complement may play a role in generation of different organs, not only in the defence against invading pathogens. Lysozyme is a bactericidal enzyme present in mucus, lymphoid tissue and serum of most fish species, but not in cod and wolffish. The enzyme has been detected in oocytes, fertilised eggs and larval stages of fish species like coho salmon, sea bass and tilapia. The activity of other enzymes like the cathepsins has been described in eggs and larvae of sea bass, cod and salmonids. Cathepsins may have a bactericidal role in the skin of fish. Lectins are carbohydrate-binding proteins that interact with pathogenic surface structures that result in opsonization, phagocytosis or activation of complement. Lectins have been isolated from the eggs of various fish species.

Animals↗
PubMed1998

A role for nautilus in the differentiation of muscle precursors.

In the Drosophila embryo, nautilus is expressed in a subset of muscle precursors and differentiated fibers and is capable of inducing muscle-specific transcription, as well as myogenic transformation. In this study, we examine the consequences of nautilus loss-of-function on the development of the somatic musculature. Genetic and molecular characterization of two overlapping deficiencies, Df(3R)nau-9 and Df(3R)nau-11a4, revealed that both of these deficiencies remove the nautilus gene without affecting a common lethal complementation group. Individuals transheterozygous for these deficiencies survive to adulthood, indicating that nautilus is not an essential gene. These embryos are, however, missing a subset of muscle fibers, providing evidence that (1) some muscle loss can be tolerated throughout larval development and (2) nautilus does play a role in muscle development. Examination of muscle precursors in these embryos revealed that nautilus is not required for the formation of muscle precursors, but rather plays a role in their differentiation into mature muscle fibers. Thus, we suggest that nautilus functions in a subset of muscle precursors to implement their specific differentiation programs.

Animals↗
PubMed2001

A comparison of the effects of organophosphate insecticide exposure and temperature stress on fluctuating asymmetry and life history traits in Culex quinquefasciatus.

Effects of exposure to a non-chemical (temperature) or chemical (organophosphate insecticide) stressor during larval development were compared in Culex quinquefasciatus mosquitoes. Stress was measured in two ways: using conventional life history traits (survival, development time and a measure of body size) and by calculating the degree of developmental instability from the departure from bilateral symmetry of wing characters (fluctuating asymmetry). Increasing insecticide dose, but not temperature, was observed to elevate wing fluctuating asymmetry in male but not female mosquitoes. Insecticide treatment reduced survival and was associated with a significant reduction in wing trait sizes in both females and males but did not significantly affect development time. Temperature was associated with a significant reduction in all life history traits in both sexes. Therefore wing fluctuating asymmetry in C. quinquefasciatus cannot be used as a general biomonitor of all stress, although it may have potential as a more specific monitor of chemical stress. It needs to be complimented with other measures such as life history and biochemical methods. The significant differences in response between sexes may impact on results of short-term larval exposures to insecticides.

Animals↗
PubMed2006

Ecological opportunity and phenotypic plasticity interact to promote character displacement and species coexistence.

We investigated the roles of resource availability and phenotypic plasticity in promoting ecological character displacement (i.e., trait evolution stemming from resource competition between species). Because ecological character displacement generates new populations that differ in resource use, this process should only occur when exploitable resources are available. We tested this hypothesis in two species of spadefoot toads (Spea bombifrons and S. multiplicata) whose tadpoles use phenotypic plasticity to develop into either an omnivore morph, which specializes on detritus, or a physically distinctive carnivore morph, which specializes on shrimp. Both species grow best on shrimp, but when reared together, S. bombifrons outcompetes S. multiplicata for shrimp and S. multiplicata outcompetes S. bombifrons for detritus. We found that when each species occurred alone in the field, they produced similar proportions of omnivores and carnivores. When the two species occurred together, however, they underwent ecological character displacement in larval development, with S. multiplicata producing mostly omnivores, and S. bombifrons producing mostly carnivores. We combined observations of natural populations with experiments to evaluate whether such character displacement was only possible when both shrimp and detritus were relatively abundant. Mixed-species ponds contained abundant detritus and shrimp, in contrast with nearby pure-species ponds, which were deficient in one resource. Experiments revealed that S. multiplicata competed poorly when detritus was rare and that S. bombifrons competed poorly when shrimp was rare. In nature, when one of these two resources was scarce, one species was missing, perhaps through competitive exclusion by the species that was the superior competitor for the remaining resource. Thus, ecological character displacement and, therefore, coexistence of close competitors, was only possible when diverse resources were available. Finally, even if exploitable resources are available, character displacement is not guaranteed to transpire if species cannot utilize such resources expeditiously. Phenotypic plasticity provides a general and important mechanism for facilitating resource partitioning. Thus, by facilitating shifts in resource use, phenotypic plasticity and ecological opportunity may often interact to promote divergence and coexistence of competitors.

Adaptation, Physiological↗
PubMed2005

Developmental disorders in larvae of eelpout (Zoarces viviparus) from German and Swedish Baltic coastal waters.

Pregnant eelpout were collected for several years at German and Swedish Baltic coastal stations with different impact of pollutants and the prevalence of fry abnormalities compared between sites. Mortality of apparently normal developed larvae was observed with high variability in both German and Swedish sites. Malformation of larvae was a prominent disorder at all German stations with a prevalence ranging from about 50% up to a maximum of 90% in almost all analysed samples. At the Swedish stations malformation rates were significantly lower (range: 0-6%). Growth retardation of fry was clearly more prominent in eelpout from German coastal waters as well. Taken together the field data suggests that impaired larval development was associated with the state of environmental pollution at the sampling locations.

Animals↗
PubMed1976

The release of a compound-chromosome stock in a vineyard cellar population of Drosophila melanogaster.

The prospect of autocidal insect control was investigated in a cellar population of D. melanogaster using a compound-chromosome stock. The released stock was synthesized by irradiating virgin female progeny derived from the cellar and crossing to a second-chromosome compound laboratory stock. Incorporation of an appropriate genetic background into the compound stock was tested in laboratory studies. Larval development to adult emergence and adult survival studies indicated the compound release stock to be relatively similar to the wild population, while behavioral tests detected no mating isolation between wild or compound genotypes. An unstable equilibrium point of compound frequency 0.7 was observed in population cage experiments with the two genotypes. Adults were released into the cellar at a 50:1 ratio in favor of the compound. Five hundred newly hatched compound-chromosome larvae were also released. Adult, larval and pupal samples were regularly made. The compound stock successfully bred in the cellar maintaining an adult frequency of at least 90% for 108 days after the release. The rapid decline in compound frequency after this period is thought to be due to the migration of inseminated wild-type females from wine storage areas adjacent to the cellar. The results indicate that a compound stock may limit the rate of population expansion in an area and may be a useful mechanism of autocidal control. It cannot be overemphasized that the probability of a successful release will be related to the level of understanding of the adaptive strategy of the population into which the release is made.

Animals↗
PubMed2006

[Some ecological parameters of Ctenocephalides felis strongylus (Jordan, 1925) (Siphonaptera: Pulicidae)].

Among the fleas of medico-veterinary interest, Ctenocephalides felis (Bouché, 1 835) is the one most studied. This taxon includes two subspecies: Ctenocephalides f. felis, and Ctenocephalides f. strongylus (Jordan, 1925); only C. f. felis has been the subject of almost all the studies available. We were, thus, interested in C. f. strongylus which can be regarded as the species of substitution of C. f. felis on the African continent. The purpose of our work was to establish some biological parameters such as: hatching of eggs, cycle of development and emergence of adults. These data were compared with those available on C. f. felis. With temperatures ranging between 19 degrees C and 29 degrees C and a relative humidity (HR) of 75 % +/- 5, the hatching rates of eggs observed from the two subspecies of C. felis, are higher than 88 %. The optimal temperature of eggs hatching for C. felis is 29 degrees C, with more than 70 % of hatching obtained in 1-2 days after the laying. The larval developments of the two subspecies are almost identical and function of the temperature 18-9 days with 27 degrees C). Only differs the minimal duration of the progressive cycle. For C. f. strongylus, it lasts in 16-17 days at 29 degrees C, 20-21 days at 27 degrees C and 38 days at 19 degrees C. For C. f. felis, published values give report of 15 days at 27 degrees C and 17 days at 24 degrees C. The emergence of adults of C. f. strongylus takes eight to ten days between 19 degrees C and 29 degrees C, while data published on C. f. felis are about 26 days at 19 degrees C and 15 days at 27 degrees C.

Animals↗
PubMed2005

Developmental analysis and squamous morphogenesis of the peripodial epithelium in Drosophila imaginal discs.

Imaginal discs of Drosophila provide an excellent system with which to study morphogenesis, pattern formation and cell proliferation in an epithelium. Discs are sac-like in structure and are composed of two epithelial layers: an upper peripodial epithelium and lower disc proper. Although development of the disc proper has been studied extensively in terms of cell proliferation, cell signaling mechanisms and pattern formation, little is known about these same processes in the peripodial epithelium. We address this topic by focusing on morphogenesis, compartmental organization, proliferation and cell lineage of the PE in wing, second thoracic leg (T2) and eye discs. We show that a subset of peripodial cells in different imaginal discs undergo a cuboidal-to-squamous cell shape change at distinct larval stages. We find that this shape change requires both Hedgehog and Decapentapelagic, but not Wingless, signaling. Additionally, squamous morphogenesis shifts the anteroposterior (AP) compartment boundary in the peripodial epithelium relative to the stationary AP boundary in the disc proper. Finally, by lineage tracing cells in the PE, we surprisingly find that peripodial cells are displaced into the disc proper during larval development and this movement leads to Ubx repression.

Animals↗
PubMed2002

Biological control of infective larvae of a gastro-intestinal nematode (Teladorsagia circumcincta) and a small lungworm (Muellerius capillaris) by Duddingtonia flagrans in goat faeces.

The high prevalence of benzimidazole-resistant nematodes in French grazing dairy goat flocks led to a search for nematode-control schemes based on integrated approaches with non-chemical options, like vaccination, grazing management, or biological control using nematophagous fungi. The effect of the daily feeding of goats with spores of the nematophagous fungus Duddingtonia flagrans on third-stage larvae (L3) of Teladorsagia circumcincta was examined in faecal cultures. In addition, the effect of D. flagrans on the survival of first-stage larvae (L1) of Muellerius capillaris was tested. Twenty-two culled dairy goats previously raised in a zero-grazing system were twice infected at monthly intervals with 5,000 and then 7,500 T. circumcincta L3. Eight animals were infected with a benzimidazole-susceptible (BZs) strain while the remainder received a benzimidazole-resistant one (BZr). Six culled goats naturally infected with M. capillaris were purchased from private farms. All the goats were divided in two groups, one group receiving daily 5 x 10(5) chlamydospores of D. flagrans/kg body weight per goat for seven consecutive days in the food, the other group acting as control. For T. circumcincta-infected goats, individual egg counts and coprocultures (13 days, 25 degrees C) followed by L3 extraction with the Baermann method were performed. For M. capillaris-infected goats, extraction of L1 with the Baermann apparatus was individually performed on day 0 and after coprocultures on days 7, 10 and 14. Reductions in percentage development of T. circumcincta L3 in fungus groups compared with control groups ranged from 84% (BZs strain) to 90% (BZr strain). A decrease in M. capillaris L1 recovery was noted on days 7 and 10 (a reduction of 70% compared with day 0) and on day 14 (85%), but this pattern was similar in both groups, whether receiving the fungus or not. At the dosage of 5 x 10(5) spores/kg body weight, D. flagrans was highly effective in reducing the larval development of T. circumcincta in goats faeces. In contrast, the fungus did not reduce M. capillaris L1 survival in faeces in our conditions.

Animals↗
PubMedDate not supplied

Genetic resistance to afltoxin B1 toxicity in Drosophila melanogaster: chromosome substitution analysis.

Different wild-type strains of Drosophila melanogaster display variation in the ability to resist the toxic effects of continuous development from the egg stage on media supplemented with aflatoxin B1 (AFB1, a potent insect toxigenic agent and vertebrate hepatocarcinogen). The genetic basis of differences in egg-pupa development time and egg-adult viability have been investigated by chromosome substitution analysis. Five strains were studied: A-11, a "resistant" strain showing relatively little effect from the AFB1 treatments, with increased development time, reduced viability, and smaller body size); and three strains produced by chromosomal substitution from A-11 and A-9, testing the effect of either chromosome X (strain R-X), 2 (strain R-2) or 3 (strain R-3) from A-11 against an A-9 background. Data from R-X, R-2, and R-3 indicate that autosomal genes on chromosomes 2 and 3 control the ability of strain A-11 to resist the toxic effects of AFB1 ingestion during larval development.

Aflatoxins↗
PubMed2004

Behavioral evidence for host fidelity among populations of the parasitic wasp, Diachasma alloeum (Muesebeck).

The concept of "host fidelity," where host-specific mating occurs in close proximity to the oviposition site and location of larval development, is thought to impart a pre-mating isolation mechanism for sympatric speciation (sensu members of the genus Rhagoletis). The apple maggot fly, Rhagoletis pomonella, and the blueberry maggot fly, R. mendax, are morphologically similar sibling species thought to have speciated in sympatry by divergence of host plant association. Both of these fly species are attacked by the specialist braconid parasitoid, Diachasma alloeum. The current study demonstrates that both male and female D. alloeum exhibit a behavioral preference for the odor of the fruit of their larval Rhagoletis host species. Specifically, those D. alloeum emerging from puparia of R. pomonella are preferentially attracted to hawthorn fruit and those emerging from puparia of R. mendax are preferentially attracted to blueberry fruit. However, male D. alloeum reared from either R. pomonella or R. mendax were equally attracted to females originating from both Rhagoletis species. We suggest that the data herein present evidence for "host fidelity," where populations of D. alloeum exhibit a greater tendency to mate and reproduce among the host plants of their preferred Rhagoletis hosts. Furthermore, host fidelity may have resulted in the evolution of distinct host races of D. alloeum tracking the speciation of their larval Rhagoletis prey.

Animals↗
PubMed2006

Toxicity of heavy metals on embryogenesis and larvae of the marine sedentary polychaete Hydroides elegans.

The toxicity of heavy metals to marine invertebrates has been widely investigated; however, the effects on marine sedentary polychaetes have largely been ignored. The toxicity of copper, aluminium, lead, nickel, and zinc on fertilization, embryogenesis, and larvae of Hydroides elegans was examined in laboratory acute-toxicity tests. Exposure to metal during fertilization or early developmental stages leads to fertilization block and arrested development, which resulted in morphologic abnormalities in embryo and larvae. Fertilization rate showed a drastic decrease at the highest metal concentration tested. Embryos of H. elegans showed a differential response to metals, and the responses were stage-specific. The different morphologic effects of heavy metals reflect differentiation of the early embryonic cells. For individual metals, the toxicity ranking for 24-hour trochophore larvae was Cu > Al > Pb > Ni > Zn, with EC(50) values of 0.122, 0.210, 0.231, 0.316, and 0.391 mg l(-1), respectively. Rate of larval development and embryogenesis were the most sensitive end points, although the latter is more advisable for routine assessment of seawater quality because of its greater simplicity. In addition to bivalves and sea urchins, polychaete embryos can provide biologic criteria for seawater quality taking into account the sensitivity of a polychaete and contributing to the detection of harmful chemicals with no marked effect on the species currently in use in seawater quality bioassays.

Animals↗
PubMed1985

Scanning and freeze-fracture study of larval nerves and neuromuscular junctions in Manduca sexta.

The nerves and nerve terminals to tonic larval muscle fibers in third and fifth instar caterpillars were studied to compare them with those formed by the same motor neurons on phasic flight muscles in adult moths. Scanning micrographs showed a primary nerve branch running the length of each fiber, with secondary nerve branches extending from it at intervals. There was a great deal of variability in both the length of the branches and the distance from the nerve at which the neuromuscular junctions were formed. The rapid increase in muscle fiber size during larval development may be responsible for this variability. The nerves and junctions were often found to be obscure by overlying fibroblasts and tracheoblasts or entering the deep muscle clefts. Those examined were similar in appearance to the adult junctions formed by the same neurons, although some may have formed single branches instead of y-shapes. The membrane specializations of the synapse seen in freeze-fractured specimens were similar to those of the adult junction. However, the overall shape of the nerve terminal within the junction differed. The larval nerve terminals appeared varicose instead of having a uniform diameter. The spacing of the nerve plaques varied, in contrast with the relatively straight alignment and even spacing of plaques found in adult junctions. Such differences could result from an interaction between the motor neuron and the two different types of muscle fiber that it innervates, an intrinsic change in the motor neurons themselves that occurs with metamorphosis, or a plastic functional response that occurs as a result of the different types of motor patterns that are used in the two stages.

Animals↗
PubMed2001

Seasonally varying diet quality and the quantitative genetics of development time and body size in birch feeding insects.

Genetic variance-covariance structures (G), describing genetic constraints on microevolutionary changes of populations, have a central role in the current theories of life-history evolution. However, the evolution of Gs in natural environments has been poorly documented. Resource quality and quantity for many animals and plants vary seasonally, which may shape genetic architectures of their life histories. In the mountain birch-insect herbivore community, leaf quality of birch for insect herbivores declines profoundly during both leaf growth and senescence, but remains stable during midsummer. Using six sawfly species specialized on the mountain birch foliage, we tested the ways in which the seasonal variation in foliage quality of birch is related to the genetic architectures of larval development time and body size. In the species consuming mature birch leaves of stable quality, that is, without diet-imposed time constraints for development time, long development led to high body mass. This was revealed by the strongly positive phenotypic and genetic correlations between the traits. In the species consuming growing or senescing leaves, on the other hand, the rapidly deteriorating leaf quality prevented the larvae from gaining high body mass after long development. In these species, the phenotypic and genetic correlations between development time and final mass were negative or zero. In the early-summer species with strong selection for rapid development, genetic variation in development time was low. These results show that the intuitively obvious positive genetic relationship between development time and final body mass is a probable outcome only when the constraints for long development are relaxed. Our study provides the first example of a modification in guild-wide patterns in the genetic architectures brought about by seasonal variation in resource quality.

Animal Feed↗
PubMed2003

Transcriptional outputs of the Caenorhabditis elegans forkhead protein DAF-16.

In Caenorhabditis elegans, the forkhead protein DAF-16 transduces insulin-like signals that regulate larval development and adult lifespan. To identify DAF-16-dependent transcriptional alterations that occur in a long-lived C. elegans strain, we used cDNA microarrays and genomic analysis to identify putative direct and indirect DAF-16 transcriptional target genes. Our analysis suggests that DAF-16 action regulates a wide range of physiological responses by altering the expression of genes involved in metabolism, energy generation and cellular stress responses. Furthermore, we observed a large overlap between DAF-16-dependent transcription and genes normally expressed in the long-lived dauer larval stage. Finally, we examined the in vivo role of 35 of these target genes by RNA-mediated interference and identified one gene encoding a putative protease that is necessary for the daf-2 Age phenotype.

Animals↗
PubMed2003

The C. elegans G-protein-coupled receptor SRA-13 inhibits RAS/MAPK signalling during olfaction and vulval development.

In C. elegans, the RAS/MAPK pathway is used in different tissues to regulate various cell fate decisions. Several positive and negative regulators tightly control the activity of the RAS/MAPK pathway at different steps. We demonstrate a link between a G-protein-coupled receptor signalling pathway and the RAS/MAPK cascade. SRA-13, a member of the SRA family of chemosensory receptors, negatively regulates RAS/MAPK signalling during vulval induction and the olfaction of volatile attractants. Epistasis analysis indicates that SRA-13 inhibits the RAS/MAPK pathway at the level or upstream of MAPK. In both tissues, the vulval precursor cells and the chemosensory neurones, SRA-13 acts through the GPA-5 Galpha protein subunit, suggesting a common mechanism of crosstalk. Moreover, we find that vulval induction is repressed by food withdrawal during larval development and that SRA-13 activity is required for the suppression of vulval induction in response to food starvation. Thus, SRA-13 may serve to adapt the activity of the RAS/MAPK pathway to environmental conditions.

Amino Acid Sequence↗
PubMed1999

Maturation of lobster stomatogastric ganglion rhythmic activity.

The stomatogastric ganglion of the adult lobster, Homarus americanus generates extremely regular pyloric rhythms with a characteristic period of 0.5-1.5 Hz. To study the changes in the pyloric rhythm during embryonic and larval development, we recorded excitatory junctional potentials evoked by lateral pyloric (LP) neuron activity. Early in development the motor discharge of the LP neuron was often irregular, preventing use of conventional analysis methods that rely on extracting burst times to calculate cycle frequency and its variability. Instead, cycle frequency was determined for the LP neuron from the peak of the power spectrum obtained from the occurrence times of excitatory junctional potentials in the p1 muscle. The ratio of the power in the peak to the power from 0 to 3 Hz was used as a relative measure of the regularity of the rhythm. Throughout embryonic and the first larval stage, LP neuron activity is slow, irregular, and only weakly periodic. The regularity of the rhythm increased during midlarval stages, and both the frequency and regularity increased considerably by the postlarval stage LIV.

Animals↗
PubMed1965

The inheritance of yellow-larva and ruby-eye in Culex pipiens.

It has been suggested that mosquito vectors of filariasis and other diseases might be controlled by genetic methods. This is not yet possible because of the lack of genetic information concerning the vector species. The present study describes the development of a marker strain which is being used to study genetic control.Two spontaneous mutants of Culex pipiens are described, one for the first time. Ruby-eye (ru) is an autosomal recessive in linkage group 2. It is completely penetrant and completely expressed. It is evident in later instar larvae, pupae, and adults. Yellow-larva (y) is an autosomal recessive, sometimes behaving as a partial dominant, and is also in linkage group 2. It is evident in late fourth-instar larvae and pupae and is generally associated with lengthened larval development. Ruby-eye and yellow-larva are occasionally seen in collections from the field. The frequency of crossing over between ru and y differs significantly among progenies and also between the sexes, the median values being 17% in males and 24% in females.

Culex↗