Distribution and abundance of planktonic mollusks along a longitudinal gradient in the Southeastern Pacific off Chile

The objectives of this research were to estimate the abundance of the main groups of planktonic mollusks (meroplanktonic larvae, holoplanktonic gastropods and cephalopod paralarvae), and relate these groups to the physical-chemical water properties along a longitudinal gradient between Caldera, on the coast of mainland Chile, and the Easter Island ecoregion (Rapa Nui Island and Salas y Gómez Island), in the Southeast Pacific Ocean. Plankton samples were collected over the course of the CIMAR 21-Islas Cruise, from October to November 2015, at 33 oceanographic stations via vertical hauls of a WP2 net (180-µm mesh size) from a maximum depth of 300 m to the sea surface. Mollusks were sorted, counted and initially assigned to Class rank, later being identified to lower taxonomic ranks. Planktonic mollusks were obtained at all stations, and were composed of 92.7% of Gastropoda and 7.3% of Bivalvia. The total abundance of mollusks varied between 55 and 4,922 individuals 100 m-3.Euthecosomate gastropods exhibited the highest occurrence within the oceanic area. Meanwhile, no paralarvae were captured. Differences in the composition of planktonic mollusks between the continental and oceanic zones were evident. Bivalve larvae increased their abundance in warmer, salty and vertically mixed waters. These results are the first record of meroplanktonic mollusks in waters near the Chilean oceanic islands, and suggest that planktonic mollusks display spatial variation at the scale of the South Pacific Basin, which could be related to the hydrographic conditions and the water column structure.

Studies on New Zealand Bivalve Larvae, with Observations on the Adults, and on the Hydrology of Bay of Islands and Wellington Harbour

<p>1) Observations made on some hydrological parameters at Bay of Islands and Wellington Harbour during 1970-71 are presented and discussed. The parameters include water temperature, salinity, dissolved oxygen content and turbidity. The water current system in Bay of Islands is also discussed and a proposed pattern presented. The hydrology of Bay of Islands and Wellington Harbour are compared. Bay of Islands is topographically lees isolated from oceanic influence than Wellington Harbour, and there is a more marked change from estuarine to oceanic hydrological conditions within the bay. Monthly mean surface seawater tempe ratures at Bay of Islands exceed those of Wellington Harbour by about 4 degrees C. Water temperature stratification is more marked in Bay of Islands than Wellington Harbour, suggesting less efficient water mixing. Salinities are lower in Wellington harbour (normally about 33.5 - 34.5 parts per thousand) than the main basin of Bay of Islands (normally about 3S.5. parts per thousand). Turbidities in estuarine areas of Bay of Islands are similar to those for most of Wellington Harbour ( 3 - 6 metres Secchi Disc visibility values), but are much Less in outer basin areas (Secchi Disc visibility values may exceed 15 metres). Dissolved oxygen content is high in both harbours, frequently exceeding 100 per cent saturation in surface water. The results suggest that although both harbours are hydrologically quite homogeneous, Wellington Harbour is more efficiently mixed than Bay of Islands. (2) Benthic and shore collections of marine bivalve molluscs were made in Bay of Islands, and benthic collections were made in Wellington Harbour, during 1970-72. The species occurring are recorded and discussed, and the distribution of some common species in Wellington Harbour is related to sediment types. A list of bivalve molluscs collected in Bay of Islands is presented, and additional species to previous Wellington Harbour species lists are recorded. Invertebrate marine communities described for New Zealand are discussed, and the bivalve fauna of both harbours is visually compared to these communities. The observations at fifty four anchor dredge benthic stations in Wellington Harbour are then treated statistically, and compared to the visual assessments. It appears that the great variability in Wellington Harbour sediments makes identity of classical communities in the harbour almost impossible. However, station groups (groups of stations with similar bivalve species present) are evident, and their distribution in Wellington Harbour correlate closely to sediment type distribution. Lists of the most abundant bivalve species occurring in both harbours, deduced from all the observations presented in this study, are given. (3) Observations were made on the occurrence of common late stage bivalve larvae in the plankton at Bay of Islands and Wellington Harbour during 1979 - 71. Three stations in Bay of Islands and four stations in Wellington Harbour were sampled approximately monthly. The bivalve larvae in shorter series of plankton samples from Raumati Beach, Dargaville Beach, Mahurangi, Ohiwa Harbour, Raglan Harbour and Kaipara Harbour during 1971 - 72 were also analysed. Twenty-nine species of bivalve larvae from these plankton samples are described. Twenty-three species of late stage bivalve larvae are provisionally identified, the identifications being based on the larval hinge structure, the distribution and abundance of the larvae in relation to adult stocks, and in some cases by correlation with the adult gonad or condition index cycle. The broad seasonal pattern of occurrence of twenty five species of late stage bivalve larvae in the plankton at Bay of Islands, Wellington Harbour and Raumati Beach is presented. (4) Ecological studies made on bivalve larvae at Bay of Islands and Wellington Harbour during 1970 - 71, are presented and compared to other published studies from overseas. Included are observations on the vertical meso-distribution of bivalve larvae over tidal cycles in estuarine and non-estuarine localities of l2m to l5m depth, the daytime vertical meso-distribution of bivalve larvae in non-estuarine water 20m- 30m in depth, the effect of light on the vertical meso-distribution of bivalve larvae in water 15m- 30min depth, and the horizontal mega-distribution of bivalve larvae in Wellington Harbour and Bay of Islands. The observations suggest that in estuarine areas, the effect of alternating tides on the vertical distribution of bivalve larvae far outweighs the effects of any other factors. During the flood tide, bivalve larvae rise from the bottom into the water column and are carried up the estuary by the tide. During the ebb tide the larvae settle and remain on the bottom. In non-estuarine areas, no such vertical migration was observed. Gravity, light and water currents, in particular, affect the vertical distribution of bivalve larvae in these areas. The horizontal mega-distribution of bivalve larvae within Wellington Harbour is fairly uniform. In Bay of Islands, bivalve larvae occur in greatest densities near the shores, while much of the central basin is almost devoid of larvae. This distribution is due to the proximity of the adult stocks to the regions of most larvae, and to the prevailing water current pattern within the bay.</p>

Studies on New Zealand Bivalve Larvae, with Observations on the Adults, and on the Hydrology of Bay of Islands and Wellington Harbour

<p>1) Observations made on some hydrological parameters at Bay of Islands and Wellington Harbour during 1970-71 are presented and discussed. The parameters include water temperature, salinity, dissolved oxygen content and turbidity. The water current system in Bay of Islands is also discussed and a proposed pattern presented. The hydrology of Bay of Islands and Wellington Harbour are compared. Bay of Islands is topographically lees isolated from oceanic influence than Wellington Harbour, and there is a more marked change from estuarine to oceanic hydrological conditions within the bay. Monthly mean surface seawater tempe ratures at Bay of Islands exceed those of Wellington Harbour by about 4 degrees C. Water temperature stratification is more marked in Bay of Islands than Wellington Harbour, suggesting less efficient water mixing. Salinities are lower in Wellington harbour (normally about 33.5 - 34.5 parts per thousand) than the main basin of Bay of Islands (normally about 3S.5. parts per thousand). Turbidities in estuarine areas of Bay of Islands are similar to those for most of Wellington Harbour ( 3 - 6 metres Secchi Disc visibility values), but are much Less in outer basin areas (Secchi Disc visibility values may exceed 15 metres). Dissolved oxygen content is high in both harbours, frequently exceeding 100 per cent saturation in surface water. The results suggest that although both harbours are hydrologically quite homogeneous, Wellington Harbour is more efficiently mixed than Bay of Islands. (2) Benthic and shore collections of marine bivalve molluscs were made in Bay of Islands, and benthic collections were made in Wellington Harbour, during 1970-72. The species occurring are recorded and discussed, and the distribution of some common species in Wellington Harbour is related to sediment types. A list of bivalve molluscs collected in Bay of Islands is presented, and additional species to previous Wellington Harbour species lists are recorded. Invertebrate marine communities described for New Zealand are discussed, and the bivalve fauna of both harbours is visually compared to these communities. The observations at fifty four anchor dredge benthic stations in Wellington Harbour are then treated statistically, and compared to the visual assessments. It appears that the great variability in Wellington Harbour sediments makes identity of classical communities in the harbour almost impossible. However, station groups (groups of stations with similar bivalve species present) are evident, and their distribution in Wellington Harbour correlate closely to sediment type distribution. Lists of the most abundant bivalve species occurring in both harbours, deduced from all the observations presented in this study, are given. (3) Observations were made on the occurrence of common late stage bivalve larvae in the plankton at Bay of Islands and Wellington Harbour during 1979 - 71. Three stations in Bay of Islands and four stations in Wellington Harbour were sampled approximately monthly. The bivalve larvae in shorter series of plankton samples from Raumati Beach, Dargaville Beach, Mahurangi, Ohiwa Harbour, Raglan Harbour and Kaipara Harbour during 1971 - 72 were also analysed. Twenty-nine species of bivalve larvae from these plankton samples are described. Twenty-three species of late stage bivalve larvae are provisionally identified, the identifications being based on the larval hinge structure, the distribution and abundance of the larvae in relation to adult stocks, and in some cases by correlation with the adult gonad or condition index cycle. The broad seasonal pattern of occurrence of twenty five species of late stage bivalve larvae in the plankton at Bay of Islands, Wellington Harbour and Raumati Beach is presented. (4) Ecological studies made on bivalve larvae at Bay of Islands and Wellington Harbour during 1970 - 71, are presented and compared to other published studies from overseas. Included are observations on the vertical meso-distribution of bivalve larvae over tidal cycles in estuarine and non-estuarine localities of l2m to l5m depth, the daytime vertical meso-distribution of bivalve larvae in non-estuarine water 20m- 30m in depth, the effect of light on the vertical meso-distribution of bivalve larvae in water 15m- 30min depth, and the horizontal mega-distribution of bivalve larvae in Wellington Harbour and Bay of Islands. The observations suggest that in estuarine areas, the effect of alternating tides on the vertical distribution of bivalve larvae far outweighs the effects of any other factors. During the flood tide, bivalve larvae rise from the bottom into the water column and are carried up the estuary by the tide. During the ebb tide the larvae settle and remain on the bottom. In non-estuarine areas, no such vertical migration was observed. Gravity, light and water currents, in particular, affect the vertical distribution of bivalve larvae in these areas. The horizontal mega-distribution of bivalve larvae within Wellington Harbour is fairly uniform. In Bay of Islands, bivalve larvae occur in greatest densities near the shores, while much of the central basin is almost devoid of larvae. This distribution is due to the proximity of the adult stocks to the regions of most larvae, and to the prevailing water current pattern within the bay.</p>

Dynamic Immune Response to Vibriosis in Pacific Oyster Crassostrea gigas Larvae during the Infection Process as Supported by Accurate Positioning of GFP-Tagged Vibrio Strains

As the immune system is not fully developed during the larval stage, hatchery culture of bivalve larvae is characterized by frequent mass mortality caused by bacterial pathogens, especially Vibrio spp. However, the knowledge is limited to the pathogenesis of vibriosis in oyster larvae, while the immune response to pathogenic microorganisms in this early life stage is still far from being fully elucidated. In this study, we combined green fluorescent protein (GFP)-tagging, histological and transcriptomic analyses to clarify the pathogenesis of experimental vibriosis and the mechanisms used by the host Pacific oyster Crassostrea gigas larvae to resist infection. The Vibrio strains first colonized the digestive system and rapidly proliferated, while only the transcription level of IκB kinase (IKK) and nuclear factor κB (NF-κB) associated with signaling transduction were up-regulated in oyster at 18 h post challenge (hpc). The mRNA levels for integrin β-1, peroxinectin, and heat shock protein 70 (HSP70), which are associated with phagocytosis, cell adhesion, and cytoprotection, were not upregulated until 30 hpc when the necrosis already happened in the larval digestive system. This suggested that the immunity in the early stages of C. gigas is not strong enough to prevent vibriosis and future research may focus on the strengthening of the gastrointestinal immune ability to defend vibriosis in bivalve larvae.

Draft Genome Sequence of Vibrio ostreicida Strain PP-203, the Type Strain of a Pathogen That Infects Bivalve Larvae

ABSTRACT Vibrio ostreicida is a Gram-negative gammaproteobacterium that has been shown to cause disease in bivalve larvae. Presented here is the draft genome of the type strain Vibrio ostreicida strain PP-203, which was isolated from the inner surface of an Ostrea edulis (European flat oyster) spat container with recorded deaths at a hatchery in Galicia, Spain.

Application of Bacteriophages to Control Vibrio alginolyticus Contamination in Oyster (Saccostrea glomerata) Larvae

Mortalities of bivalve larvae and spat linked with Vibrio spp. infection have been described in hatcheries since 1959, causing potential development of resistant bacteria. A reliable and sustainable solution to this problem is yet to be developed. Potential treatment of bacterial infection with bacteriophages is gaining interest in aquaculture as a more sustainable option for managing Vibrio spp. infection. This study assessed the effectiveness of bacteriophages (Φ-5, Φ-6, and Φ-7) against pathogenic Vibrio isolates (USC-26004 and USC-26005). These phage isolates were found to belong to the Myoviridae viral family. A total of 212 ORFs of Φ-5 were identified and annotated. The genome of this phage contained putative thymidine kinase and lysin enzyme. During infections with phages, the OD values of the isolates USC-26005 and USC-26004 remained stable at a much lower reading compared to the control after 9 h of incubation. Mortality rate of oyster (Saccostrea glomerata) larvae was 28.2 ± 3.5% in the bacteriophage treatment group, compared to 77.9 ± 9.1% in the bacterial treatment group after 24 h incubation. Findings of this study indicate that lytic phages might be utilized as potential bio-control agents of luminescent bacterial disease in oyster hatcheries.

Adaption potential of Crassostrea gigas to ocean acidification and disease caused by Vibrio harveyi

The survival and development of bivalve larvae is adversely impacted by ocean acidification and Vibrio infection, indicating that bivalves need to simultaneously adapt to both stressors associated with anthropogenic climate change. In this study, we use a half-dial breeding design to estimate heritability (h2) for survival to Vibrio harveyi infection and larval shell length to aragonite undersaturated and normal conditions in laboratory-reared Crassostrea gigas. Phenotypic differences were observed between families for these traits with heritability estimated to be moderate for survival to V. harveyi challenge (h2 = 0.25) and low for shell length in corrosive (Ωaragonite = 0.9, h2 = 0.15) and normal conditions (Ωaragonite = 1.6, h2 = 0.15). Predicted breeding values for larval shell length are correlated between aragonite-undersaturated and normal conditions (Spearman r = 0.63, p &lt; 0.05), indicating that larger larvae tend to do better in corrosive seawater. Aquaculture hatcheries routinely cull slow-growing larvae to reduce and synchronize time taken for larvae to metamorphose to spat, thus inadvertently applying size-related selection for larger larvae. This indirect selection in the hatchery populations provides a plausible explanation why domesticated oyster populations are less sensitive to ocean acidification.

Identification and Genome Analysis of Vibrio coralliilyticus Causing Mortality of Pacific Oyster (Crassostrea gigas) Larvae

Vibrio coralliilyticus is known as a coral pathogen that also infects marine bivalve larvae worldwide. It is considered to be one of the major constraints in artificial marine bivalve seed production as it causes mortality. In this study, we first isolated and characterized a high virulent of V. coralliilyticus designated as SNUTY-1 that was the cause of Pacific oyster larvae mortality in Korea. In the pathogenicity test, exposure to 2.14 × 105 CFU/mL for 24 h caused mortality to 88.65 ± 2.4% of the tested healthy Pacific oyster larvae. SNUTY-1 showed anti-microbial resistance to β-lactams, such as penicillins, cephalosporins, and carbapenems. We sequenced and assembled the complete genome of SNUTY-1 (5,842,676 bp), consisting of two chromosomes (Chr I and Chr II) and two plasmids (pSNUTY1 and pSNUTY2). The COG functional analysis confirmed that Chr I had more genes associated with basic cellular functions in comparison to Chr II. The results of the phylogenetic trees based on OrthoANI values indicated that the SNUTY-1 was closely related to V. coralliilyticus strains. SNUTY-1 had a unique plasmid (pSNUTY2), which could mean that the Korean isolate is different from other sequenced V. coralliilyticus strains from different geographical origins. Toxic proteins such as cytolysin/hemolysin and extracellular metalloprotease genes were encoded on Chr I and Chr II of SNUTY-1. These data facilitate the control of V. coralliilyticus infections in aquaculture by providing valuable insights into the biodiversity of this organism and valuable information for the study of virulence factors.