First Stage Of Larval Development Research Articles

The value of EDTA treatment of hatchery water to rear Greenshell™ mussel (Perna canaliculus) larvae

The chelating agent ethylenediaminetetraacetic acid (EDTA) is used throughout the world to improve the yield of early stage D-larvae during bivalve hatchery production. Adding EDTA (12 μM) to seawater significantly increases the survival of Greenshell™ mussel (Perna canaliculus) larvae during their first 48 h of development. However, whether there are benefits of continuing to use EDTA beyond this first stage of larval development remain unknown and were tested in this study. After rearing for 48 h in the presence of EDTA, P. canaliculus larvae were experimentally raised to 22-day post-fertilisation in seawater with and without 12 μM EDTA. The survival, shell length growth, algal ingestion rate, swimming activity and potential toxic metal accumulation by the larvae were compared over this period. There were minimal benefits from continuing addition of EDTA. However, significant changes in metal concentrations within the larvae were observed. Zinc, cadmium and mercury were detected at significantly lower concentrations in 22-day-old larvae reared with EDTA versus those without EDTA. Collectively, the results indicate that the use of EDTA is critical only during the first 48 h of larval development, during which time larval shell formation is initiated and appears highly vulnerable to interference by heavy metal ions.

Development and migration of the C. elegans Q neuroblasts and their descendants.

During the first stage of larval development, the Q neuroblasts and their descendants migrate to well-defined positions along the anteroposterior body axis, where they differentiate into sensory neurons and interneurons. The two Q neuroblasts are initially present at similar positions on the left and right lateral side, but this symmetry is broken when the Q neuroblast on the left side (QL) polarizes towards the posterior and the Q neuroblast on the right side (QR) towards the anterior. This left-right asymmetry is maintained when the descendants of the two Q neuroblasts migrate to their final positions in the posterior and anterior. The mechanisms that establish this asymmetry and control the migration of the Q descendants along the anteroposterior axis are surprisingly complex and include interplay between Wnt signaling pathways, homeotic genes, and the basic cell migration and polarity machinery. Here, we will give an overview of what is currently known about the mechanisms that mediate and control the development and migration of the Q neuroblasts and their descendants.

Gene expression pattern of digestive and antioxidant enzymes during the larval development of reared Atlantic bluefin tuna (ABFT),Thunnus thynnusL.

The aim of this study was to determine whether mortality observed during the larval development of reared bluefin tuna (Thunnus thynnus) could be related to improper expression profiles of key genes involved in digestive or antioxidant response capabilities. Tuna larvae were sampled at hatching, 2, 5, 10, 15 and 20 dph (days post hatching) for the relative quantification of transcripts encoded by genes involved in digestive [trypsinogen 1 (TRYP1), alpha‐amylase (AMY), aminopeptidase N (ANPEP)] and antioxidant [catalase (CAT)] functions. The levels of expression of ANPEP related to the development and maturation of intestinal function increased from 5 to 20 dph. Furthermore, AMY and TRYP1 genes, which are pancreatic enzymes implicated in carbohydrate and peptide digestions exhibit a typical peak of expression at 5 and 15 dph respectively. The antioxidant enzyme, CAT, exhibited higher mRNA levels during the first stage of larval development. In conclusion, our investigation indicates that the expression of genes involved in digestive and antioxidant physiological processes followed typical patterns which could not explain high mortality rate observed during the first stage of larval development.

The role of dispersal and retention in the early life stages of shrimp in a lowland river

This study investigated the importance of dispersal and retention processes during early ontogeny for three caridean shrimp species that complete their entire life history in freshwater. Directional traps were used to examine the small-scale movement patterns of shrimp into and out of nursery habitat patches (slackwaters) in a small lowland river in southeastern Australia. Movement patterns provided evidence for two contrasting life history based dispersal and retention strategies. For the two smaller atyid species, Paratya australiensis and Caridina mccullochi , the majority of larvae remained within the slackwater in which they were hatched until the final stage of development, at which point dispersal, either among slackwaters or out of slackwaters to faster-flowing pool and run habitats, occurred. For the larger palaemonid species, Macrobrachium australiense , larvae were hatched into slackwaters and dispersal occurred predominately during the first stage of larval development and then decreased as development progressed. Despite the differences in dispersal strategies among species, movement was mostly associated with a particular larval stage and thus emphasizes the importance of retention during critical developmental periods and of the potential impact that flow alteration could have on these and other species with similar life histories.

Non‐receptor tyrosine kinase CSK‐1 controls pharyngeal muscle organization in Caenorhabditis elegans

C-terminal Src kinase (Csk) is a non-receptor type of tyrosine kinase, and serves as an essential negative regulator of Src family tyrosine kinases (SFKs) in vertebrates. However, analyses of Csk and SFKs from primitive animals suggest that the Csk-mediated mechanisms regulating SFK activity might diverge between evolutional branches, different tissues or SFK family members. We examined in vivo roles of CSK-1, a Caenorhabditis elegans orthologue of Csk, by generating animals lacking csk-1 function. Although some csk-1 mutants died during embryogenesis, the majority of mutants died during the first stage of larval development. In csk-1 mutants, the function of pharyngeal muscles, the major site of CSK-1 expression, was severely damaged. The pumping of pharyngeal grinder cells became arrhythmic, causing disabled feeding. Electron microscopy showed that pharyngeal muscle filaments were disorientated in the csk-1 mutants. These indicate that CSK-1 is crucial for proper organization of pharyngeal muscles. However, the growth arrest phenotype in csk-1 mutants could not be suppressed by src-1 and/or src-2 mutation, and SRC-1 was not significantly activated in the csk-1 mutants. These results suggest that CSK-1 has an essential function in organization of pharyngeal muscle filaments that does not require C. elegans SFKs.

Survival strategy of Echinococcus multilocularis in the human host

As exemplified by “aborted” calcified liver lesions commonly found in patients from endemic areas, Echinococcus multilocularis metacestodes develop only in a minority of individuals exposed to infection with the papasite. Clinical research has disclosed some aspects of the survival strategy of E. multilocularis in human hosts. Clinical observations in liver transplantation and AIDS suggest that suppression of cellular/Th1-related immunity increases disease severity. Most of the studies have stressed a role for CD8+ T cells and for Interleukin-10 in the development of tolerance. A spontaneous secretion of IL-10 by the PBMC seems to be the immunological hallmark of patients with progressive forms of alveolar echinococcosis (AE). IL-10-induced inhibition of effector macrophages, but also of antigen-presenting dendritic cells, may be operating and allowing parasite growth and survival. The genetic correlates of susceptibility to infection with E. multilocularis are clearer in humans than in the mouse model. A significant link between MHC polymorphism and clinical presentation of AE has been shown, and the spontaneous secretion of IL-10 in patients with a progressive AE is higher in patients with the HLA DR3+, DQ2+ haplotype. Clustering of cases in certain families, in communities otherwise exposed to similar risk factors, also points to immuno-genetic predisposition factors that may allow the larva to escape host immunity more easily. The first stage of larval development may be crucial in producing “danger signals” stimulating the initial production of cytokines. Therapeutic use of Interferon alpha is an attempt to foil the survival strategy of E. multilocularis.

Potential effect of an anchovy-mediated pump on the vertical availability of nitrogen for primary production in the Catalan Sea (northwest Mediterranean)

The potential effect on the pelagic ecosystem of nitrogen recycling by anchovies ( Engraulis encrasicolus) in a major spawning area of the Catalan Sea (NW Mediterranean) was assessed by comparing estimates of N excretion in the form of ammonia and urea with the N requirements of primary production. The influence of diel vertical migrations of anchovies on primary production in the stratified layer above the thermocline was also addressed. Results showed that N released by anchovy accounted for almost 2% of phytoplankton total demand in the entire water column during the thermal stratification period. Diel trophic dynamics in the area related to vertical migrations led to a net upward nutrient transport through the thermocline, which might contribute to the vertical reallocation of production within the photic layer towards the stratified layer. If nocturnal N excretion occurs in the topmost 10 m, where spawning takes place, the net production increase in this surface layer could be >5%. This could enhance survival in the first stages of larval development of the species.

Settlement of the muricid Concholepas concholepas and its relationship with El Niño and coastal upwellings in southern Chile

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 167:171-175 (1998) - doi:10.3354/meps167171 Settlement of the muricid Concholepas concholepas and its relationship with El Niño and coastal upwellings in southern Chile C. A. Moreno1,*, G. Asencio1, W. E. Duarte1, V. Marín2 1Instituto de Ecología y Evolución, Universidad Austral de Chile, Casilla 567, Valdivia, Chile 2Depto. Cs. Ecológicas, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile *E-mail: cmoreno@uach.cl The settlement of Concholepas concholepas (Brugière, 1789) (Gastropoda; Muricidae) was monitored in the intertidal zone in front of the Marine Reserve of Mehuin in Maiquillahue Bay, south-central Chile, from 1989 to 1997. Data appeared correlated to the SOI (Southern Oscillation Index) and the occurrence of local upwelling as detected from satellite images. Greatest settlement density was linked to the coupling of upwelling between February and April, coinciding with the occurrence of the first stages of larval development (which hatch from benthic capsules as a late veliger stage). These conditions co-occur when the mean value of the SOI over the 3 mo prior to the beginning of the settlement period approximates zero. Settlement · Recruitment · Concholepas concholepas · El Niño · Upwelling · Chile Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 167. Publication date: June 18, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.

An activating mutation in a Caenorhabditis elegans Gs protein induces neural degeneration.

Heterotrimeric guanine nucleotide-binding proteins (G proteins) act as signal-transducing molecules that connect serpentine-transmembrane receptors to a variety of intracellular effectors. We characterized a Caenorhabditis elegans G(s) gene, gsa-1, which encodes a G(s) alpha-subunit (G alpha(s)) that is expressed throughout the nervous system and in muscle cells. gsa-1 is an essential gene; a loss-of-function mutation in gsa-1 results in lethality at the first stage of larval development. Partial (mosaic) loss of G alpha(s) expression or overexpression of the protein results in reciprocal defects in movement and egg-laying, suggesting a role for G alpha(s) in the regulation of these behaviors. Expression of a constitutively active form of G alpha(s) from an inducible promotor results in hypercontraction of body-wall muscle cells and vacuolization and degeneration of neurons within hours of induction. Neurons that are susceptible to the degeneration induced by activated G alpha(s) are predominantly motoneurons located within the ventral nerve cord. Phenotypic analysis shows that the induced neural degeneration is not the result of programmed cell death but is probably caused by the activation of ion channels. A genetic suppressor of activated G alpha(s) was isolated that identifies a putative downstream target of G(s) signaling.

In situ hybridization analyses of Na, K-ATPase alpha-subunit expression during early larval development of Artemia franciscana.

The spatial pattern of expression of the mRNA encoded by the Na,K-ATPase alpha-subunit cDNA clone pArATNa136 was determined by in situ hybridization of first, second, and third instar Artemia franciscana larvae. This mRNA was expressed at high levels in the salt gland, the antennal gland, and the end of the midgut, which are the three main osmoregulatory organs in Artemia at these stages of development. The pattern of expression was similar at the three stages of development analyzed, although the level of expression increased during development, especially in the salt and antennal glands. The expression of the mRNA coding for another Na, K-ATPase alpha-subunit isoform, the proposed alpha 2-isoform, was also determined and was shown to be limited to the salt gland. These results suggest that the clone pArATNa136 codes for the biochemically defined alpha 1-isoform of the Na,K-ATPase alpha-subunit and reinforce the importance of this isoform in osmoregulation at the three larval stages studied. The alpha 2-isoform may also be involved in osmoregulation during the first stages of larval development.

Embryotoxic effects of environmental chemicals: Tests with the South African clawed toad ( Xenopus laevis)

In the course of the investigations reported below, it was shown that p-chloroaniline has a lethal effect on the embryos of Xenopus laevis at a concentration of 100 ppm and is development inhibiting (teratogenic) at concentrations of 1 and 10 ppm, respectively. In the case of aniline, a significant development-inhibiting effect was observed at a concentration as low as 1 ppm. A toxic effect was caused by concentrations between 30 and 40 ppm during embryogenesis and by concentrations above 40 ppm during larval development. A very conspicuous finding was an inhibiting effect of 20 to 40 ppm aniline on pigmentation during embryogenesis and of a concentration as low as 1 ppm on the body size of the young toads. In the case of potassium dichromate, it was possible to barely detect a weak development-inhibiting effect during embryogenesis but no development-retarding effect during larval development. Toxic effects of potassium dichromate occurred during embryogenesis at concentrations of 5 and 7.5 ppm and during the larval development at concentrations above 10 ppm. Sodium dodecylbenzenesulfonic acid at a concentration of 50 ppm was found to have such a strong embryolethal effect that 80% of the eggs showed no cell division at all and the remaining 20% developed to only the bicellular stage. A teratogenic effect of this substance was not observed. Phenol, too, was found to be toxic at a concentration of 50 ppm; in contrast to sodium dodecylbenzenesulfonic acid, however, it did not show any lethal effect on the embryos but it did on the tadpoles, mainly in the first stages of larval development. Lower concentrations of phenol (5 and 10 ppm) had a nonsignificant inhibiting effect on the growth of the larvae. A teratogenic effect of phenol was not detected.