Feeding selectivity of bivalve larvae on natural plankton assemblages in the Western English Channel

Meroplankton, including bivalve larvae, are an important and yet understudied component of coastal marine food webs. Understanding the baseline of meroplankton ecology is imperative to establish and predict their sensitivity to local and global marine stressors. Over an annual cycle (October 2009–September 2010), bivalve larvae were collected from the Western Channel Observatory time series station L4 (50°15.00′N, 4°13.02′W). The morphologically similar larvae were identified by analysis of the 18S nuclear small subunit ribosomal RNA gene, and a series of incubation experiments were conducted to determine larval ingestion rates on natural plankton assemblages. Complementary gut content analysis was performed using a PCR-based method for detecting prey DNA both from field-collected larvae and those from the feeding experiments. Molecular identification of bivalve larvae showed the community composition to change over the course of the sampling period with domination by Phaxas in winter and higher diversity in autumn. The larvae selected for nanoeukaryotes (2–20 µm) including coccolithophores (<20 µm) which together comprised >75 % of the bivalve larvae diet. Additionally, a small percentage of carbon ingested originated from heterotrophic ciliates (<30 µm). The molecular analysis of bivalve larvae gut content provided increased resolution of identification of prey consumed and demonstrated that the composition of prey consumed established through bottle incubations conferred with that established from in situ larvae. Despite changes in bivalve larvae community structure, clearance rates of each prey type did not change significantly over the course of the experiment, suggesting different bivalve larvae species may consume similar prey.

Effects of environmental conditions on planktonic abundances, benthic recruitment and growth rates of the bivalve mollusc Ruditapes decussatus in a Portuguese coastal lagoon

Controlling environmental parameters for the early stages of marine invertebrates have received little attention, particularly in field studies. This study involves measurement of abundances and growth rates of the bivalve Ruditapes decussatus Linnaeus 1758 during its planktonic larval and early benthic life stages in a coastal lagoon: Ria Formosa, Portugal. Measured abundances were compared with tidal amplitude, water temperature, salinity, wind velocity and direction, and a food availability indicator 2chlorophyll a). Data were obtained on abundance and prodissoconch length of the larvae, measured two tothreetimes perweek,and ofpost-larval stagesindividuals thathadsettled inartificial collectors over10months.Larval and juvenile cohorts were identified using size-frequency distributions and larval ages estimated by larval shell growth lines.

Vertical distribution of benthic invertebrate larvae during an upwelling event along a transect off the tropical Brazilian continental margin

Abundance and composition of marine benthic communities have been relatively well studied in the SE Brazilian coast, but little is known on patterns controlling the distribution of their planktonic larval stages. A survey of larval abundance in the continental margin, using a Multi-Plankton Sampler, was conducted in a cross-shelf transect off Cabo Frio (23 degrees S and 42 degrees W) during a costal upwelling event. Hydrographic conditions were monitored through discrete CDT casts. Chlorophyll-a in the top 100 m of the water column was determined and changes in surface chlorophyll-a was estimated using SeaWiFS images. Based on the larval abundances and the meso-scale hydrodynamics scenario, our results suggest two different processes affecting larval distributions. High larval densities were found nearshore due to the upwelling event associated with high chlorophyll a and strong along shore current. On the continental slope, high larval abundance was associated with a clockwise rotating meander, which may have entrapped larvae from a region located further north (Cabo de Sao Tome, 22 degrees S and 41 degrees W). In mid-shelf areas, our data suggests that vertical migration may likely occur as a response to avoid offshore transport by upwelling plumes and/or cyclonic meanders. The hydrodynamic scenario observed in the study area has two distinct yet extremely important consequences: larval retention on food-rich upwelling areas and the broadening of the tropical domain to southernmost subtropical areas. (C) 2009 Elsevier B.V. All rights reserved.

Molecular cloning and functional analysis of cathepsin B in nutrient metabolism during larval development in Meretrix meretrix

Seed rearing is an important part in large scale clam culture industry. Since the nutritional history affects early development in bivalve, the condition of larval nutrition plays a key role in successful seed rearing. So far, the molecular mechanism of nutrient uptake in bivalve larvae is unclear. As one of the important proteolytic enzymes, cathepsin B of several organisms has been reported to be involved in digestion. We intended to analyze whether cathepsin B is involved in larval nutrient metabolism in the economic bivalve, clam Meretrix meretrix. The full length of M. meretrix cathepsin B (MmeCB) cDNA was cloned, which is 1647 bp with an open reading frame of 1014 bp. The deduced amino acid sequence encoded a preproenzyme of 337 residues with Cys-114, His-282 and Asn-302 composing cathepsin B activity center. The temporal and spatial expressions of MmeCB mRNA were examined from trochophore to post larva stages by whole mount in situ hybridization. In trochophore stage, no detectable signal was found. In the later three stages, MmeCB mRNA was detected in the digestive gland, suggesting a possible role of MmeCB in digestion. Moreover, MmeCB mRNA was also observed in the epidermal cells in D-veligers. Cathepsin B specific inhibitor (CA074 methyl ester) was applied to block the activity of cathepsin B in unfed larvae. The average shell lengths of treated larvae were smaller than that in control groups. The results of mRNA epidermal distribution and inhibitor treatment in D-veligers indicated that MmeCB may be also associated with other pathway of nutrient metabolism in larval epidermis. The overall results in this paper revealed that MmeCB might play a role in larval nutrient metabolism. (C) 2008 Elsevier B.V. All rights reserved.

A juvenile recruitment prediction model for Ruditapes decussatus (L.) (Bivalvia : Mollusca)

Despite the importance of larval abundance in determining the recruitment of benthic marine invertebrates and as a major factor in marine benthic community structure, relating planktonic larval abundance with post-settlement post-larvae and juveniles in the benthos is difficult. It is hampered by several methodological difficulties, including sampling frequency, ability to follow larval and post-larval or juvenile cohorts, and ability to calculate growth and mortality rates. In our work, an intensive sampling strategy was used. Larvae in the plankton were collected at weekly intervals, while post-larvae that settled into collectors were analysed fortnightly. Planktonic larval and benthic post-larval/juvenile cohorts were determined, and growth and mortality rates calculated. Integration of all equations allowed the development of a theoretical formulation that, based on the abundance and planktonic larval duration, permits an estimation of the future abundance of post-larvae/juveniles during the first year of benthic life. The model can be applied to a sample in which it was necessary only to measure larval length.

Studies on The Eco Biology of The Indian Pearl Oyster, Pinctada Fucata (Gould)

The present work aims to study induced maturation of the pearl oyster for induced spawning experiments. The work on larval development was done with a view to developing techniques for the artificial rearing of commercially important pearl oyster P fucata, and also to elucidate the principles and problems of tropical bivalve larvae in general for detailed investigations in the future. The present study is designed to probe into the details of the basic aspects of the biology related to the hatchery technology of Pinctada fucata and the understanding of the factors which influence induction of maturation, spawning, larval rearing and spat settlement. This would go a long way in the upgradation of hatchery technology of the Indian Pearl oyster Pinctada fucata fora commercial level seed production..

Ecosystem structure of Gomishan Wetland

Gomishan Wetland is situated in the extreme southern part of the eastern coast of Caspian Sea. It is connected to the Caspian Sea, so its hydrological features are directly generated from the sea. The whole wetland area (which also consists of the northern part of the wetland that is situated in Turkmenistan republic) is calculated with the aid of the Satellite Images for the years of 1977, 1987 and 1998 respectively 5070, 16320 and 29520 hectares. To have better ideas about food chains in the aquatic ecosystem, five permanent stations was appointed in different parts of the wetland. During one year field study, at the beginning of each month, physical, chemical and biological characteristics of the water and the sediment was surveyed and different specimens were gathered, fixed and took to the laboratories for the relevant analyses. The factors measured in water samples were mainly consist of turbidity, pH, EC, DO, BOD, PO4, NO3, alkalinity, Cl and hardness . The factors measured from sediment samples were the percentage of Sand, Very Fine Sand, Silt, Clay, K, P, N, and Organic Carbon. Biological examinations of the water has been consist of planktonic sample collections, determination, counting and analysis of both phyto and zoo planktons of the wetland. For example the zooplanktons of the Gomishan Wetland are determined in 15 groups, belonging to 5 phyla. The seasonal changes are recognized considerable. The least density of the zooplanktons is occurred in February. The density of most of the groups is seen from the beginning of the summer until the mid autumn. The annual mean density for any 15-zooplankton groups and also the minimum and maximum density with %95 confidences, for each of them, is calculated for the environment of all of the stations and also for the whole wetland. The spatial distribution of the individuals within the population of each of the groups is introduced, according to regular or contagious or random distribution. Diversity indices are calculated for the zooplanktons living in the environment of the stations. Comparison of the wetland, with the southeastern Caspian Sea, from the point of view of zooplankton density and diversity is also obtained. Benthos invertebrates in each station from sediment samples were also extracted. The specimens were colored by Rose Bengal solvent and then were determinate and counted, in separate groups of macro and meio benthos. Among the macro benthos, the highest density was seen in the species of Fyrgula caspia. After that, more density was seen respectively in Apra ovata, Cerastoderma sp., Balanus sp., Nerds divesicolarr, lifytilaster lineatus and Dreissena sp. Among the meio benthos, the most density was seen in Foraminifera and then respectively in Ostracoda, Nernatoda and Bivalve larvae. The indices of diversity and distribution are also calculated. As the birds in this lagoon are of prime importance, all mid winter waterfowl censuses available from recent 13 years are gathered and analysis. Also a whole year (12 times, each at the beginning of one month) waterfowl census was undertaken, throughout the wetland. According to this study, the Eastern Ecosystem of the wetland, is supporting the most population (%75) of the waterfowls, the Middle Open Water Ecosystem and the Western Reed bed Ecosystem, are supporting respectively %14 and %11 of the population. Four of the species are found in the global threatened red list, and the wintering population of the 20 species of the site, in some years, are observed more than %I of the global populations. The Waterfowl Species Diversity and Similarity Indices are given also.

Phylogeography and hybrid swarms: history of brackish water bivalve diversity in North European marginal seas

This study addressed the large-scale molecular zoogeography in two brackish water bivalve molluscs, Macoma balthica and Cerastoderma glaucum, and genetic signatures of the postglacial colonization of Northern Europe by them. The traditional view poses that M. balthica in the Baltic, White and Barents seas (i.e. marginal seas) represent direct postglacial descendants of the adjacent Northeast Atlantic populations, but this has recently been challenged by observations of close genetic affinities between these marginal populations and those of the Northeast Pacific. The primary aim of the thesis was to verify, quantify and characterize the Pacific genetic contribution across North European populations of M. balthica and to resolve the phylogeographic histories of the two bivalve taxa in range-wide studies using information from mitochondrial DNA (mtDNA) and nuclear allozyme polymorphisms. The presence of recent Pacific genetic influence in M. balthica of the Baltic, White and Barents seas, along with an Atlantic element, was confirmed by mtDNA sequence data. On a broader temporal and geographical scale, altogether four independent trans-Arctic invasions of Macoma from the Pacific since the Miocene seem to have been involved in generating the current North Atlantic lineage diversity. The latest trans-Arctic invasion that affected the current Baltic, White and Barents Sea populations probably took place in the early post-glacial. The nuclear genetic compositions of these marginal sea populations are intermediate between those of pure Pacific and Atlantic subspecies. In the marginal sea populations of mixed ancestry (Barents, White and Northern Baltic seas), the Pacific and Atlantic components are now randomly associated in the genomes of individual clams, which indicates both pervasive historical interbreeding between the previously long-isolated lineages (subspecies), and current isolation of these populations from the adjacent pure Atlantic populations. These mixed populations can be characterized as self-supporting hybrid swarms, and they arguably represent the most extensive marine animal hybrid swarms so far documented. Each of the three swarms still has a distinct genetic composition, and the relative Pacific contributions vary from 30 to 90 % in local populations. This diversity highlights the potential of introgressive hybridization to rapidly give rise to new evolutionarily and ecologically significant units in the marine realm. In the south of the Danish straits and in the Southern Baltic Sea, a broad genetic transition zone links the pure North Sea subspecies M. balthica rubra to the inner Baltic hybrid swarm, which has about 60 % of Pacific contribution in its genome. This transition zone has no regular smooth clinal structure, but its populations show strong genotypic disequilibria typical of a hybrid zone maintained by the interplay of selection and gene flow by dispersing pelagic larvae. The structure of the genetic transition is partly in line with features of Baltic water circulation and salinity stratification, with greater penetration of Atlantic genes on the Baltic south coast and in deeper water populations. In all, the scenarios of historical isolation and secondary contact that arise from the phylogeographic studies of both Macoma and Cerastoderma shed light to the more general but enigmatic patterns seen in marine phylogeography, where deep genetic breaks are often seen in species with high dispersal potential.

Pharmacological and immunocytochemical investigation of the role of catecholamines on larval metamorphosis by beta-adrenergic-like receptor in the bivalve Meretrix meretrix

Catecholamines regulate several physiological processes in mollusks. Many pharmacological experiments have been conducted to determine the effects of adrenergic agonist and antagonist of catecholamine receptors on Meretrix meretrix metamorphosis. Results showed that adrenaline (AD) and noradrenaline (NA) had substantial effects (p < 0.05) on larval metamorphosis at concentrations ranging from 10 mu M to 100 mu M. 10 mu M beta-adrenergic receptor (AR) agonist isoproterenol showed the same inducement effect as that of NA and AD on metamorphosis, whereas the alpha-AR agonist phenylephrine had no significant effect at concentrations between 0.1 mu M and 100 mu M concentrations (p > 0.05). Furthermore, I mu M beta-AR antagonist propanolol, but not alpha-AR antagonist prazosin, depressed the larval metamorphosis induced by NA or AD. By immunocytochemistry, two cell bodies of beta-adrenergic-like receptor, C/A1, C/A2, were observed in the cerebral/apical ganglion of competent larvae. In addition, there were other immunoreactive dots near C/A1 and C/A2. The results of pharmacology and immunocytochemistry suggests that beta-adrenergic-like receptor located in the larval CNS, might play a considerable role in the larval metamorphosis of M meretrix by AD or NA. (c) 2006 Elsevier B.V. All rights reserved.

Spatial and temporal variation of commercially important bivalve species in the Algarve coast, Portugal

Dissertação de mestrado, Biologia Marinha, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015

STOWING AWAY ON SHIPS THAT PASS IN THE NIGHT: SCLEROBIONT ASSEMBLAGES ON INDIVIDUALLY DATED BIVALVE AND BRACHIOPOD SHELLS FROM A SUBTROPICAL SHELF

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)