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PubMed2026

Comprehensive identification and evolutionary analysis of the Wnt gene family in bivalves: Insights into the larval development of the noble scallop Chlamys nobilis.

The Wnt gene family regulates fundamental developmental processes in metazoans, but its evolutionary composition and developmental deployment in bivalves remain largely unresolved. Here, we performed a comparative genomic analysis of Wnt genes in 19 bivalve species and examined developmental expression profiles in the noble scallop Chlamys nobilis, with Crassostrea gigas and Chlamys farreri used for cross-species comparison. A total of 235 Wnt genes were identified and assigned to 12 subfamilies. No reliable Wnt3 ortholog was detected in any analyzed bivalve, supporting the view that Wnt3 loss occurred early during lophotrochozoan evolution rather than representing a lineage-specific absence. Most Wnt proteins retained the conserved WNT domain, indicating strong structural conservation, whereas lineage-specific copy-number variation and gene loss were observed among species. C. farreri and C. gigas each retained 12 Wnt genes and lacked Wnt3, whereas C. nobilis lacked Wnt3, Wnt7, and Wnt16. Developmental transcriptome analysis and RT-qPCR revealed clear stage-specific expression patterns. In C. gigas, Wnt2/10/A were highly expressed during earlydevelopment and peaked around the D-shaped larval stage, while Wnt8 and Wnt11 showed distinct stage-specific peaks. By contrast, Wnt1/5/6/9 were more active during later larval development or juvenile formation. These results provide a comparative framework for bivalve Wnt evolution and identify candidate Wnt genes potentially involved in larval development and aquaculture-relevant developmental transitions.

Animals↗
PubMed2003

A comparison of larval development and mucosal mast cell responses in worm-naïve goat yearlings, kids and lambs undergoing primary and secondary challenge with Teladorsagia circumcincta.

Larval development, mucosal mast cell (MMC) and eosinophil responses in worm-nai;ve lambs, yearling goats and goat kids were compared using two different experimental challenge regimes involving oral administration of infective Teladorsagia circumcincta L(3). Experimental challenge regimes enabled primary and secondary immune responses in the two species to be compared. Goats carried higher worm burdens than lambs and there were significant differences in the stages of development attained by the larval challenge that established in the two species. Possible physiological reasons for these differences are discussed. There were also differences in the establishment and development of larvae in individual yearlings which may indicate the development of a weak age-related immune response. Quantitative analysis of MMC and globule leukocyte (GL) recruitment and functional activity in the form of mast cell-specific proteinase (MCP) production demonstrated differences between the species with goat tissues containing significantly higher numbers of GL and lower concentrations of MCP than the lambs. Quantitative analysis of blood and tissue eosinophil responses failed to demonstrate any significant differences in either species under the two challenge regimes.

Aging↗
PubMed1977

A fine-structural study of embryonic and larval development in the gymnoblastic hydroid Pennaria tiarella.

1. The pregastrulation blastomers contain electron-dense granules which become localized after gastrulation in the apices of the developing epithelio-muscle cells and persist throughout larval development. The cytoplasm of the blastomeres is organized into anucleate, membrane-delimited lobules. The lobules, which persist until six hours of development, come to contain a single, peripherally located cisterna of granular endoplasmic reticulum. Microvilli are present at the earliest stages examined and persist throughout development. Cilia are first detected at four hours. 2. Gastrulation, marked by the appearance of the mesoglea, occurs between six and eight hours of development. Basal foot processes of epithelio-muscle cells are detected by eight hours, but myonemes cannot be detected until later in development. 3. Immediately following gastrulation, mucous cells begin their differentiation from dividing cells located near the apex of the ectoderm. During their differentiation, the cells elongate toward the mesoglea. 4. By 16 hours post-fertilization, a third cell type can be detected in the ectoderm. The cell, which contains no granules, has an unusual cytoplasmic organization in which fused membranes divide the cytoplasm into parallel compartments containing a single cisterna of granular endoplasmic reticulum. 5. The findings of the present study are correlated with those of previous studies of development in Pennaria and other hydroids. The possible functional roles of the Type I granules, the cytoplasmic lobules, and the nongranular cell are discussed.

Animals↗
PubMed1997

Mosquito hexamerins: characterization during larval development.

We report here the first examination of hexamerins expressed during mosquito larval development. Haemolymph proteins from fourth-instar larvae of six species representing the two major subfamilies of mosquitoes were characterized by immunoblotting using antisera to calliphorin, the major hexamerin of the blowfly. Calliphora vicina, or to LSP1 or LSP2, the two distinct hexamerins of Drosophila melanogaster. In each mosquito species the antisera demonstrated the presence of multiple abundant hexamerin polypeptides of 66-85 kDa in molecular weight. According to the subunit composition of native proteins, the larval hexamerins from both Aedes aegypti and Anopheles gambiae form heterohexamers. Furthermore, the two major Aedes hexamerin subunits (AaHex1 and AaHex2) are neither rich in aromatic amino acids nor methionine. cDNA clones encoding AaHex1 and AaHex2 were isolated and used to show that hexamerin mRNA is uniquely expressed in fourth-instar larvae of both A. aegypti and A. gambiae and disappears rapidly at the onset of pupal development.

Aedes↗
PubMed1986

Ecdysteroid levels during the larval development of the spider crab Hyas araneus.

Ecdysteroid levels were determined by radioimmunoassay during the larval development of the spider crab Hyas araneus L. In each of the three larval instars (zoea I, zoea II, megalopa) a minimum in ecdysteroid levels was found during early postmoult and a maximum during premoult. The amounts of ecdysteroids increased during development and reached maxima of 93, 137, and 165 pg ecdysone equivalents per larva in zoea I, zoea II, and megalopa, respectively. Ecdysteroid concentrations per unit of body dry weight or carbon increased during each moulting cycle, but the average values showed decreasing tendency from the first to the last instar. The main ecdysteroid in all larval instars and during the moulting cycle was 20-OH-ecdysone, and practically no ecdysone could be detected by HPLC-RIA.

Animals↗
PubMed1994

Embryogenesis, hatching and larval development of Artemia during orbital spaceflight.

Developmental biology studies, using gastrula-arrested cysts of the brine shrimp Artemia franciscana, were conducted during two flights of the space shuttle Atlantis (missions STS-37 and STS-43) in 1991. Dehydrated cysts were activated, on orbit, by addition of salt water to the cysts, and then development was terminated by the addition of fixative. Development took place in 5 ml syringes, connected by tubing to activation syringes, containing salt water, and termination syringes, containing fixative. Comparison of space results with simultaneous ground control experiments showed that equivalent percentages of naupliar larvae hatched in the syringes (40%). Thus, reactivation of development, completion of embryogenesis, emergence and hatching took place, during spaceflight, without recognizable alteration in numbers of larvae produced. Post-hatching larval development was studied in experiments where development was terminated, by introduction of fixative, 2 days, 4 days, and 8 days after reinitiation of development. During spaceflight, successive larval instars or stages, interrupted by molts, occurred, generating brine shrimp at appropriate larval instars. Naupliar larvae possessed the single naupliar eye, and development of the lateral pair of adult eyes also took place in space. Transmission electron microscopy revealed extensive differentiation, including skeletal muscle and gut endoderm, as well as the eye tissues. These studies demonstrate the potential value of Artemia for developmental biology studies during spaceflight, and show that extensive degrees of development can take place in this microgravity environment.

Animals↗
PubMed1990

Juvenile hormone mediated DNA synthesis during larval development of Corcyra cephalonica (Insecta).

Large amount of DNA is synthesized during larval development of Corcyra and this is conspicuously seen in the early-last instar. Ligation in early-last instar causes a decline in both DNA content and DNA concentration. Radiolabelling studies show a low rate of DNA synthesis in isolated abdomens, suggesting that hormonal factors from the anterior half of the larvae play a regulatory role in the DNA metabolism. Juvenile hormone I (JH-I) treatment of ligated early-last instar stimulates DNA synthesis with consequent increase in DNA content and DNA concentration.

Abdomen↗
PubMed2002

The abdominal-B-like gene expression during larval development of Nereis virens (polychaeta).

We have studied the posterior Hox gene Nvi-Post1 expression in the early development of the polychaete Nereis virens. This is the first evidence of the posterior group Hox genes expression during the larval development of a Lophotrochozoan. The expression begins in the trochophore hyposphere at the prospective sites of larval parapodia. As the larva develops the expression weakens and finally becomes undetectable in the nectochaete stage and juvenile worm. The Nvi-Post1 expression appears to be important for larval, but not postlarval development.

Animals↗
PubMed2003

Phormidium animalis (Cyanobacteria: Oscillatoriaceae) supports larval development of Anopheles albimanus.

The capability of Phormidium animalis, a cyanobacterium commonly found in larval habitats of Anopheles albimanus in southern Mexico, to support larval development of this mosquito was investigated. First-stage larvae were reared under insectary conditions with P. animalis ad libitum and their development was compared with larvae fed with wheat germ. The time of pupation and adult mosquito size, assessed by wing length, were similar in both groups, but fewer adult mosquitoes were obtained from larvae fed with the cyanobacteria. Nevertheless, these observations indicate that P. animalis is ingested and assimilated by larval An. albimanus, making this cyanobacterium a good candidate for genetic engineering for the introduction of mosquitocidal toxins for malaria control in the region.

Animals↗
PubMed2000

Larval development of the tropical deep-sea echinoid Aspidodiadema jacobyi: phylogenetic implications.

The complete larval development of an echinoid in the family Aspidodiadematidae is described for the first time from in vitro cultures of Aspidodiadema jacobyi, a bathyal species from the Bahamian Slope. Over a period of 5 months, embryos grew from small (98-micron) eggs to very large (3071-micron) and complex planktotrophic echinopluteus larvae. The fully developed larva has five pairs of red-pigmented arms (preoral, anterolateral, postoral, posterodorsal, and posterolateral); fenestrated triangular plates at the bases of fenestrated postoral and posterodorsal arms; a complex dorsal arch; posterodorsal vibratile lobes; a ring of cilia around the region of the preoral and anterolateral arms; and a long, unpaired posterior process containing a fenestrated rod. The presence of a posterior process and posterodorsal arms makes the larva of Aspidodiadema jacobyi much more similar to larvae of irregular urchins in the order Spatangoidea than to other families of the order Diadematoida, to which the family is normally assigned. This unexpected larval form lends support to a recommendation that the Aspidodiadematidae should be either elevated to ordinal status as a sister group of the order Diadematoida, or split off as a sister group of the other families within the order. In either case, if we accept the parsimonious hypothesis that the aboral process and posterodorsal arms were derived only once in the evolutionary history of euechinoids, then the larval data suggest that the Aspidodiadematidae may be very near the node where the irregular and regular euechinoids first diverged.

Animals↗
PubMed1987

Arrested larval development in cattle nematodes.

Most economically important cattle nematodes are able to arrest their larval development within the host - entering a period of dormancy or hypobiosis. Arrested larvae have a low death rate, and large numbers can accumulate in infected cattle during the grazing season. Because of this, outbreaks of disease caused by such nematodes can occur at times when recent infection with the parasites could not have occurred, for example during winter in temperature northern climates when cattle are normally housed. The capacity to arrest is a heritable trait. It is seen as an adaptation by the parasite to avoid further development to its free-living stages during times when the climate is unsuitable for free-living survival. But levels of arrestment can vary markedly in different regions, in different cattle, and under different management regimes. Climatic factors, previous conditioning, host immune status, and farm management all seem to affect arrestment levels. In this article, James Armour and Mary Duncan review the biological basis of the phenomenon, and discuss the apparently conflicting views on how it is controlled.

Journal Article↗
PubMed1989

Dynamics of the intramolluscan larval development of Schistosoma haematobium: replication of daughter sporocysts and cercarial production.

During the intramolluscan larval development of Schistosoma haematobium (Algerian strain) in Bulinus truncatus, two replication processes of daughter sporocysts occur. Replication by direct sporocystogenesis appears more important than sporocystogenesis post cercariogenesis. These mechanisms assure a periodic renewal of the sporocyst stock in the snail host and seem to be synchronized with the development of cercarial generations. The succession of several generations of cercariae is responsible for the alternation of high and low periods of productivity. The scheme proposed for the intramolluscan development of S. haemtobium is compared with those described for S. mansoni and S. bovis and interpreted in terms of demographic strategies adapted to a better exploitation of the snail host.

Animals↗
PubMed1997

Larval development of Dicrocoelium dendriticum in Cernuella (Xeromagna) cespitum arigonis under controlled laboratory conditions.

The larval development of Dicrocoelium dendriticum (Digenea: Dicrocoeliidae) in experimentally infected Cernuella (Xeromagna) cespitum arigonis (Schmidt, 1853), a species of mollusc important in the epidemiology of dicrocoeliosis in Spain, has been studied. A total of 948 specimens of this mollusc, distributed in five batches, were tested with individual doses of 50 to 150 parasite eggs, obtained from sheep, after 4 days without food. After infection these molluscs and control specimens were kept in an environmental simulation chamber at 20 degrees C, 50% relative humidity and 7 h of light per day. To detect the parasite, a minimum of six molluscs were examined every 20 days from day 1 post-infection (p.i.). The eggs of D. dendriticum were eliminated in the molluscan faeces 48 h post infection. The percentages of molluscs harbouring the parasite ranged between 17.53% and 75%. Daughter sporocysts with undifferentiated germinal masses and occupying very reduced areas of the hepatopancreas were observed 50 days p.i. and in the period immediately following. After 110 days p.i. sporocysts with cercariae at different stages of development were found although slimeball emission was never observed.

Animals↗
PubMed2005

The AP-3 clathrin-associated complex is essential for embryonic and larval development in Caenorhabditis elegans.

The adaptor protein (AP) complexes are involved in membrane transport of many proteins. There are 3 AP complexes in C. elegans unlike mammals that have four. To study the biological functions of the AP-3 complexes of C. elegans, we sought homologues of the mouse and human genes that encode subunits of the AP-3 complexes by screening C. elegans genomic and EST sequences. We identified single copies of homologues of the m3, s3, b3 and d genes. The medium chain of AP-3 is encoded by a single gene in C. elegans but two different genes in mammals. Since there are no known mutations in these genes in C. elegans, we performed RNAi to assess their functions in development. RNAi of each of the genes caused embryonic and larval lethal phenotypes. APM-3 is expressed in most cells, particularly strongly in spermatheca and vulva. We conclude that the products of the C. elegans m3, s3, b3 and d genes are essential for embryogenesis and larval development.

Adaptor Protein Complex 3↗
PubMed1990

Anopheles gambiae complex egg-stage survival in dry soil from larval development sites in western Kenya.

The potential for Anopheles egg survival in dry soil from larval development sites was investigated in western Kenya. A total of 230 dry soil samples collected in 1987, 1988 and 1989 yielded 126 first-instar Anopheles gambiae s.l. larvae from 2 to 5 days after flooding with water. These larvae were from dried animal hoofprints along streams (57.9%), from dried edges of permanent and temporary pools (41.3%) and from dried stream beds (0.8%). Larval density was 1.2 larvae/kg of soil from positive microhabitats in 1987 and 2.4 larvae/kg in 1988. Thirteen larvae from the 1989 soil samples, reared to adults, were identified by DNA probes as Anopheles gambiae sensu strictu (n = 6) and Anopheles arabiensis (n = 7). Experimentally, eggs from field-collected females remained viable up to 12 days for An. gambiae s.l. and 10 days for An. funestus. In western Kenya, egg viability in dry soil may represent a significant, short-term survival mechanism for 2 species of the An. gambiae complex.

Animals↗
PubMed2004

Evaluation of a larval development assay (DrenchRite) for the detection of anthelmintic resistance in cyathostomin nematodes of horses.

A larval development assay (LDA, DrenchRite) was evaluated to determine the effectiveness of this method in detecting anthelmintic resistance in cyathostomin nematodes of horses. A total of 15 horse farms from Georgia and South Carolina (USA) and Population S ponies from the University of Kentucky (USA) were included in this study. Nematode eggs were extracted from pooled fecal samples and placed into the wells of a DrenchRite plate for testing against thiabendazole (TBZ), levamisole (LEV) and 2 ivermectin (IVM) analogs (IVM-1, IVM-2). After a 7-day incubation larvae in each well were counted and data were analyzed by logistic regression. Resistance status of each farm for different drugs was determined in a separate study using a fecal egg count reduction test. LDA were performed on the 15 farms once, however, the Population S cyathostomins were assayed on 3 separate occasions to estimate the consistency of results between assays. Mean TBZ LC50 for oxibendazole resistant, suspected resistant and sensitive farms were 0.2015, 0.1625, and 0.1355 microM, respectively. For LEV, mean LC50 for PYR resistant, suspected resistant and sensitive farms were 1.590, 1.8018 and 1.4219 microM, respectively. All 15 farms had worms susceptible to IVM; mean LC50 for IVM-1 and for IVM-2 were 7.5727 and 87.9718 nM, respectively. A linear mixed model was fitted to the data to determine the relationship between LC50 and LC95 and resistance status for each farm. No meaningful relations were found. Consistency of assays varied between drugs, being best for TBZ and worst for LEV and IVM-1. All farms in this study had benzimidazole-resistant nematodes; therefore usefulness of DrenchRite for discriminating susceptibility versus resistance to this drug class could not be accurately assessed. Moreover, since all farms tested were sensitive to IVM and resistance to this drug class has not yet been reported in cyathostomins, it is not possible to assess accurately the usefulness of DrenchRite LDA for detecting IVM resistance at this time. Assay results for LEV suggest that LEV in a LDA does not yield data that is useful in estimating PYR efficacy in vivo. Based on results for PYR/LEV, the current high prevalence of benzimidazole resistance, no known cases of IVM resistance, and the sometimes extreme variation in results seen in many of the assays, DrenchRite LDA cannot be considered a useful tool for the diagnosis of resistance in cyathostomins of horses at present.

Animals↗
PubMedDate not supplied

[Experimental study of the larval development of Hymenolepis stylosa (Rudolphi, 1809), Raillet, 1899 (Cestoda : cyelophyllidea) (author's transl)].

Comparative studies of the larval development of Hymenolepis stylosa Rudolphi, 1809 (Cestoda : Cyclophyllidea), a parasite of Corvid birds are undertaken from three insect species. The development in the beetle, Tenebrio molitor shows that the scolex differenciation occurs before the invagination of the metacestode in the cystic vesicle. The cercomer is long, narrow and flexuous. In the grasshopper, Lousta migratoria, the development is the same one but the scolex invaganation begins early. In another beetle, Dermestes frischi, the oncosphere is stopped in the gut-wall. The morphology and development of the cysticercoids of avian species of Hymenolepis, which have a well known life cycle, are similar. Studies on the structure of the larval stages of avian and mammal species of Hymenolepis seem necessary to find the relations between the different species of this genus.

Animals↗
PubMed1985

Fatty acid composition of phospholipids and neutral lipids during embryonic and early larval development in Atlantic herring (Clupea harengus, L.).

The fatty acid compositions of total polar and total neutral lipids of Atlantic herring eggs and larvae were determined immediately before fertilization, after fertilization and at various times during subsequent embryonic and early larval development. Within 3 hr after fertilization the percentage of total PUFA in neutral lipid decreased from 33% to 20%, with a reciprocal increase in monoenes. Thereafter the percentage of PUFA in the neutral lipids increased progressively, attaining the original level in ripe eggs by the time of yolk sac absorption. During the larval stages the percentage of PUFA continued to increase in the neutral lipid, reaching almost 44% of the total by day 32 after fertilization, although it was reduced to 32% by day 36. The percentage of monoenes in the neutral lipid displayed a progressive decrease during the whole period of development from 3 hr after fertilization. Throughout all the developmental periods the fatty acid composition of total polar lipids remained essentially constant. The polar lipids of the yolk sac displayed virtually the same fatty acid composition as the larval bodies, but the neutral lipids of the yolk sac were low in PUFA compared to the larval bodies. The results are discussed with reference to changes in lipid class composition during development. The conservation of high levels of PUFA in lipids during embryogenesis and early larval development reflects the importance of these fatty acids during development.

Animals↗