Oyster Larvae Research Articles

Differential inimical effects of Alexandrium spp. and Karenia spp. on cleavage, hatching, and two larval stages of Japanese pearl oyster Pinctada fucata martensii

The effects of four harmful and potentially harmful dinoflagellates, Alexandrium affine, Alexandrium catenella, Karenia mikimotoi and Karenia papilionacea, on the early-life development of Japanese pearl oyster, Pinctada fucata martensii, were assessed. Density- and time-dependent, mild to severe effects on cleavage, hatching, D-larvae, and pre-settling larvae of pearl oysters were found. The non-PST-producer A. affine was highly toxic to both cleavage and hatching with potent lytic activity at a density of 2.5×102cellsml−1. The PST-producer A. catenella also affected cleavage and reduced hatching, but at 2-fold higher density with lytic activity only at the highest density tested (2×103cellsml−1). Cleavage was affected by K. mikimotoi and K. papilionacea at 1.5×104cellsml−1, but hatching was only affected by K. mikimotoi. Mortalities in both larval stages were not observed. D-larvae were not affected by K. papilionacea, but their activity decreased following exposure to A. affine, A. catenella, and mainly K. mikimotoi. Pre-settling larvae were more sensitive to all four harmful algae than were D-larvae. The dinoflagellate A. catenella had the highest effect on the activity of pre-settling larvae (10cellsml−1), followed by K. mikimotoi (5×102cellsml−1), A. affine (5×102cellsml−1), and K. papilionacea (1.5×104cellsml−1). The results of this study suggest that complex mechanisms, including paralytic shellfish toxins (PST), brevetoxins (PbTx) and a variety of lytic and membrane-disruptive toxins and/or other metabolites, could have been involved in such inimical stage-specific effects. It also highlight the threat posed by harmful algae on the recruitment of Japanese pearl oysters and potentially other bivalve species, and show that they could exert subchronic to chronic effects at realistically low cell densities, and impact bivalve populations through altered reproductive and recruitment processes, ultimately hampering both wild populations and aquaculture industries.

Hydrodynamic sensing and behavior by oyster larvae in turbulence and waves.

Hydrodynamic signals from turbulence and waves may provide marine invertebrate larvae with behavioral cues that affect the pathways and energetic costs of larval delivery to adult habitats. Oysters (Crassostrea virginica) live in sheltered estuaries with strong turbulence and small waves, but their larvae can be transported into coastal waters with large waves. These contrasting environments have different ranges of hydrodynamic signals, because turbulence generally produces higher spatial velocity gradients, whereas waves can produce higher temporal velocity gradients. To understand how physical processes affect oyster larval behavior, transport and energetics, we exposed larvae to different combinations of turbulence and waves in flow tanks with (1) wavy turbulence, (2) a seiche and (3) rectilinear accelerations. We quantified behavioral responses of individual larvae to local instantaneous flows using two-phase, infrared particle-image velocimetry. Both high dissipation rates and high wave-generated accelerations induced most larvae to swim faster upward. High dissipation rates also induced some rapid, active dives, whereas high accelerations induced only weak active dives. In both turbulence and waves, faster swimming and active diving were achieved through an increase in propulsive force and power output that would carry a high energetic cost. Swimming costs could be offset if larvae reaching surface waters had a higher probability of being transported shoreward by Stokes drift, whereas diving costs could be offset by enhanced settlement or predator avoidance. These complex behaviors suggest that larvae integrate multiple hydrodynamic signals to manage dispersal tradeoffs, spending more energy to raise the probability of successful transport to suitable locations.

A partial substitution of microalgae with single cell detritus produced from seaweed (Porphyra haitanensis) for the nursery culture of tropical oyster (Crassostrea belcheri)

Oyster seed production in hatchery and nursery systems has relied on the production of microalgae, which is cost effective, but often unpredictable. The development of a satisfactory substitute diet would greatly reduce production costs of hatchery operations. Single cell detritus (SCD) production from seaweed (Porphyra haitanensis) may have great potential as a partial substitute for microalgae. In this experiment, a technique for producing SCD was developed and the product was used as a partial substitute for microalgae for the nursery culture of juvenile tropical oysters (Crassostrea belcheri) in a hatchery setting. A reverse osmosis technique was used on ground seaweed (particle size <200 μm) immersed in freshwater and placed on a shaker at 100 rpm for 2 h before being returned to seawater. This technique was shown to be highly effective for SCD production with a density of 33.7 ± 7.0 × 104 cell mL−1 and the percentage of SCD particle diameter <20 μm was 89.2%. A partial replacement of microalgae with SCD was found to be unsuitable for nursing oyster larvae. For juvenile oysters (shell width 1.85 ± 0.03 mm and shell length 1.78 ± 0.06 mm) substituting 75% of microalgae with SCD showed lower absolute shell growth, and lower daily yields and survival rates when compared to rates substituting 50% or lower substitution with SCD, or 100% microalgae (P < 0.05). It was found that substituting 50% of the traditional microalgae with SCD produced from seaweed (P. haitanensis) can be used as a partial microalgae substitute for the nursery culture of the juvenile tropical oyster.

Molecular cloning of two molluscan caspases and gene functional analysis during Crassostrea angulata (Fujian oyster) larval metamorphosis.

Caspases have been demonstrated to possess important functions in apoptosis and immune system in vertebrate. But there is less information reported on the oyster larval development. In the present work, two full-length molluscan caspase genes, named Cacaspase-2 and Cacaspase-3, were characterized for the first time from Fujian oyster, Crassostrea angulata. Which respectively encode two predicted proteins both containing two caspase domains of p20 and p10 including the cysteine active site pentapeptide "QACRG" and the histidine active site signature. Otherwise Cacaspase-2 also contains a caspase recruitment domain. Homology and phylogenetic analysis showed that Cacaspase-2 shared high similarity with initiator caspase-2 groups, but Cacaspase-3 clustered together with executioner caspase-3 groups. Cacaspase-2 and Cacaspase-3 mRNA were both highly expressed in gills and labial palp and were significantly expressed highly in larvae during settlement and metamorphosis. Through the whole mount in situ hybridization, the location of Cacaspase-2 is in the foot of the oyster larvae and the location of Cacaspase-3 is in both the foot and velum tissues. These results implied that Cacaspase-2 and Cacaspase-3 genes play a key role in the loss of foot and Cacaspase-3 gene has an important function in the loss of velum during larvae metamorphosis in C. angulata.

A PRELIMINARY IDENTIFICATION ON EARLY STAGE OF OYSTER LARVAE SOURCE AND DISPERSAL: A FIELD AND NUMERICAL STUDY NEARBY ZHOUSHEI RIVER ESTUARY, TAIWAN

Oyster (Crassostrea angulata) has long been an important species for economic aquaculture in Taiwan. This study was motivated by a recent and emerged problem that the traditional regions where oyster larvae (OL) were collected in the south part of Zhoushei river during the past decades have already changed. Figure 1 depicts our study region with three geophysical features: (1)the biggest industrial park (i.e. Mailiao Industrial Park, MIP) in Taiwan is located at the mouth of Zhoushei river, (2)multiple sandbars exist within shallow-water regions, and (3)a wide range of tidal flats where a well-mixed estuary has been confirmed. We speculate that those factors may give a mixed contribution to water quality, flow structure and biological process, thereby affecting dispersal and connectivity of OL. Unfortunately, a conclusive reason causing the mentioned problem is still unknown. The main goal of this study is to identify where the OL may come from, and what affects the dispersal ranges and recruitment areas during early stages. In this paper, we shall present field and numerical results for a preliminary identification on early stage of OL source and dispersal.

Mortalities of Eastern and Pacific oyster Larvae caused by the pathogens Vibrio coralliilyticus and Vibrio tubiashii.

Vibrio tubiashii is reported to be a bacterial pathogen of larval Eastern oysters (Crassostrea virginica) and Pacific oysters (Crassostrea gigas) and has been associated with major hatchery crashes, causing shortages in seed oysters for commercial shellfish producers. Another bacterium, Vibrio coralliilyticus, a well-known coral pathogen, has recently been shown to elicit mortality in fish and shellfish. Several strains of V. coralliilyticus, such as ATCC 19105 and Pacific isolates RE22 and RE98, were misidentified as V. tubiashii until recently. We compared the mortalities caused by two V. tubiashii and four V. coralliilyticus strains in Eastern and Pacific oyster larvae. The 50% lethal dose (LD50) of V. coralliilyticus in Eastern oysters (defined here as the dose required to kill 50% of the population in 6 days) ranged from 1.1 × 10(4) to 3.0 × 10(4) CFU/ml seawater; strains RE98 and RE22 were the most virulent. This study shows that V. coralliilyticus causes mortality in Eastern oyster larvae. Results for Pacific oysters were similar, with LD50s between 1.2 × 10(4) and 4.0 × 10(4) CFU/ml. Vibrio tubiashii ATCC 19106 and ATCC 19109 were highly infectious toward Eastern oyster larvae but were essentially nonpathogenic toward healthy Pacific oyster larvae at dosages of ≥1.1 × 10(4) CFU/ml. These data, coupled with the fact that several isolates originally thought to be V. tubiashii are actually V. coralliilyticus, suggest that V. coralliilyticus has been a more significant pathogen for larval bivalve shellfish than V. tubiashii, particularly on the U.S. West Coast, contributing to substantial hatchery-associated morbidity and mortality in recent years.

Predator-mediated landscape structure: seasonal patterns of spatial expansion and prey control by Chrysaora quinquecirrha and Mnemiopsis leidyi

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 510:183-200 (2014) - DOI: https://doi.org/10.3354/meps10850 Predator-mediated landscape structure: seasonal patterns of spatial expansion and prey control by Chrysaora quinquecirrha and Mnemiopsis leidyi Denise Breitburg*, Rebecca Burrell Smithsonian Environmental Research Center, PO Box 28, Edgewater, Maryland 21037, USA *Corresponding author: breitburgd@si.edu ABSTRACT: The scyphomedusa Chrysaora quinquecirrha and lobate ctenophore Mnemiopsis leidyi are dominant consumers in the planktivorous food web in Chesapeake Bay, USA, and are important predators throughout much of their ranges. Our studies in the Patuxent River (a subestuary of Chesapeake Bay) and its tributary creeks suggest successive waves of population spread and trophic influence of these 2 gelatinous species in opposing directions across the aquatic landscape. In years when both species were abundant, Mnemiopsis appeared first in the main channel of the Patuxent River and initially was most abundant in the bottom layer of the water column. Mnemiopsis densities then rapidly increased in shallow tributaries and coves, with distributions likely caused by a combination of transport and temporally and spatially varying patterns of growth and reproduction. In contrast, densities of Chrysaora ephyrae were initially highest in small coves and tributary creeks, with densities of Chrysaora medusae spreading outward from these small systems to the main river as summer progressed. We found no conclusive evidence for tidally-cued vertical migrations of either species or directional swimming by Chrysaora that would create these differing spatio-temporal patterns. As Chrysaora increased and spread, it likely reduced or eliminated Mnemiopsis by direct predation, and possibly through the effect that partial predation could have on Mnemiopsis reproduction. Because of differences in diets and feeding rates, these shifting temporal and spatial patterns of medusa and ctenophore dominance potentially influence spatial distributions and temporal patterns of survival of ichthyoplankton, oyster larvae, and copepods. KEY WORDS: Gelatinous zooplankton · Estuary · Food web · Spatial distributions · Chesapeake Bay Full text in pdf format Supplementary material PreviousNextCite this article as: Breitburg D, Burrell R (2014) Predator-mediated landscape structure: seasonal patterns of spatial expansion and prey control by Chrysaora quinquecirrha and Mnemiopsis leidyi . Mar Ecol Prog Ser 510:183-200. https://doi.org/10.3354/meps10850 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 510. Online publication date: September 09, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Soundscape variation from a larval perspective: the case for habitat-associated sound as a settlement cue for weakly swimming estuarine larvae

Settlement is a critical phase in the life history of most benthic marine organisms and has important implications for their survival and reproductive success, and ultimately for pop - ulation and community dynamics. Larval encounter with settlement habitats is likely facilitated through the use of habitat-specific physical and chemical cues, but the scales over which particular habitat-related environmental cues may operate are rarely measured. In Pamlico Sound, North Carolina, USA we used passively drifting acoustic recorders to measure the varia- tion in habitat-related underwater sound, a potential broad-scale settlement cue, at spatio - temporal scales relevant to dispersing bivalve larvae in the estuary. Sound levels increased by up to 30 dB during passage over oyster reefs compared to off-reef soft bottom areas, and sound level fluctuations in the 2000 to 23 000 Hz frequency range closely corresponded to the presence of oyster reef patches below drifters, indicating that sound characteristics could reliably provide a signal of benthic habitat type to planktonic larvae. Using these soundscape measurements and the known descent capabilities of oyster larvae, we demonstrate with a conceptual model that response to habitat-related sound cues is a feasible mechanism for enhanced larval encounter with settlement substrate.

The density and spatial arrangement of the invasive oyster Crassostrea gigas determines its impact on settlement of native oyster larvae

Understanding how the density and spatial arrangement of invaders is critical to developing management strategies of pest species. The Pacific oyster, Crassostrea gigas, has been translocated around the world for aquaculture and in many instances has established wild populations. Relative to other species of bivalve, it displays rapid suspension feeding, which may cause mortality of pelagic invertebrate larvae. We compared the effect on settlement of Sydney rock oyster, Saccostrea glomerata, larvae of manipulating the spatial arrangement and density of native S. glomerata, and non-native C. gigas. We hypothesized that while manipulations of dead oysters would reveal the same positive relationship between attachment surface area and S. glomerata settlement between the two species, manipulations of live oysters would reveal differing density-dependent effects between the native and non-native oyster. In the field, whether oysters were live or dead, more larvae settled on C. gigas than S. glomerata when substrate was arranged in monospecific clumps. When, however, the two species were interspersed, there were no differences in larval settlement between them. By contrast, in aquaria simulating a higher effective oyster density, more larvae settled on live S. glomerata than C. gigas. When C. gigas was prevented from suspension feeding, settlement of larvae on C. gigas was enhanced. By contrast, settlement was similar between the two species when dead. While the presently low densities of the invasive oyster C. gigas may enhance S. glomerata larval settlement in east Australian estuaries, future increases in densities could produce negative impacts on native oyster settlement. Synthesis and applications: Our study has shown that both the spatial arrangement and density of invaders can influence their impact. Hence, management strategies aimed at preventing invasive populations reaching damaging sizes should not only consider the threshold density at which impacts exceed some acceptable limit, but also how patch formation modifies this.

Evaluating and improving a semi‐automated image analysis technique for identifying bivalve larvae

Knowledge of the distribution, abundance, and transport of bivalve larvae is limited due to their small size, similar morphologies between species, and lack of an automated approach for identification. The objective of this research is to evaluate and improve the accuracy of ShellBi, a novel supervised image classification method that uses birefringence patterns on the shells of bivalve larvae under polarized light to identify species. The performance of the ShellBi method was tested by rearing Crassostrea virginica (eastern oyster) larvae at different temperatures (21.3 and 27.5°C) and salinities (10.3, 14.1, 14.4, and 20.5). Differences in rearing temperatures resulted in differences in classification accuracy, as did large variations in salinity (≥10 units). classification accuracies increased from 67–88% to 97–99% when training sets included images of larvae reared in conditions similar to those of the larvae being classified. Additional tests indicate that misclassification rates ranged from 0 to 13% for false positives and from 0 to 22% for false negatives, depending on the proportion of oyster larvae in the sample. Results suggest that this technique could be applied to field samples with high accuracy as long as the images that are used to make classifications include larvae that were reared in conditions that are similar to those in situ. In addition, these findings demonstrate that the ShellBi method can be used to measure and identify bivalve larvae in a different system than the one for which it was developed, suggesting that the method has broad applicability in marine and estuarine systems.

The potential of ocean acidification on suppressing larval development in the Pacific oyster Crassostrea gigas and blood cockle Arca inflata Reeve

We evaluated the effect of pH on larval development in larval Pacific oyster (Crassostrea gigas) and blood cockle (Arca inflata Reeve). The larvae were reared at pH 8.2 (control), 7.9, 7.6, or 7.3 beginning 30 min or 24 h post fertilization. Exposure to lower pH during early embryonic development inhibited larval shell formation in both species. Compared with the control, larvae took longer to reach the D-veliger stage when reared under pH 7.6 and 7.3. Exposure to lower pH immediately after fertilization resulted in significantly delayed shell formation in the Pacific oyster larvae at pH 7.3 and blood cockle larvae at pH 7.6 and 7.3. However, when exposure was delayed until 24 h post fertilization, shell formation was only inhibited in blood cockle larvae reared at pH 7.3. Thus, the early embryonic stages were more sensitive to acidified conditions. Our results suggest that ocean acidification will have an adverse effect on embryonic development in bivalves. Although the effects appear subtle, they may accumulate and lead to subsequent issues during later larval development.

Effects of the red tide dinoflagellate, Karenia brevis, on early development of the eastern oyster Crassostrea virginica and northern quahog Mercenaria mercenaria

The brevetoxin-producing dinoflagellate, Karenia brevis, adversely affects many shellfish species including the commercially and ecologically important bivalve molluscs, the northern quahog (=hard clam) Mercenaria mercenaria and eastern oyster Crassostrea virginica, in the Gulf of Mexico, USA. This study assessed the effects of exposure of these bivalves to K. brevis during their early development. In separate experiments, embryos of 2–4 cell stage of M. mercenaria and C. virginica were exposed to both whole and lysed K. brevis cells isolated from Manasota Key, Florida. Low bloom concentrations of 500 to 3000 cellsmL−1 were simulated for 96h. Shell length, percent abnormality (and normality), and percent mortality of resulting larvae were measured. Percentages were recorded after 6, 24, and 96h of exposure; larval shell length was measured at 24 and 96h. For both quahogs and oysters, the effects of exposing embryos to K. brevis on all larval responses were generally dose- and time-dependent. Percent mortalities and abnormalities of both clam and oyster embryos increased significantly after only 6h of exposure to whole cells of K. brevis. For clams, these parameters were significantly higher in whole and lysed treatments (at 3000 cellsmL−1) than in controls. Percent mortalities of oysters were significantly higher in the whole-cell treatment (3000 cellsmL−1) than under control conditions. After 24h of exposure, mean larval shell length of both bivalve species was significantly reduced relative to controls. This was evident for clam larvae in both the lysed treatment at 1500 cellsmL−1 and in whole and lysed treatments at 3000 cellsmL−1, and for oyster larvae in the lysed treatment at 3000 cellsmL−1. After 96h, both species exposed to the lysed cell treatment at 3000 cellsmL−1 had significantly smaller larvae compared to those in the control. Overall, lysed cells of K. brevis had a more pronounced effect on shell length, percent abnormality, and mortality in both clams and oysters than did whole cells. Given the fact that blooms of K. brevis overlap with the spawning periods of these two bivalves, and that cells of this naked dinoflagellate are readily lysed by wave action, these results suggest that exposure to K. brevis during the early life history stages of clams and oysters could adversely affect their population recruitment. Further, the presence of whole or lysed cells of K. brevis in hatcheries could have a major negative impact on production.

Multi-technique approach to characterise the effects of cryopreservation on larval development of the Pacific oyster (Crassostrea gigas)

Cryopreservation experiments were conducted on D-stage larvae of the Pacific oyster (Crassostrea gigas) to investigate the effects of two cryoprotectant solutions and three cooling rates on larval development from 1 to 22 days post-fertilisation. Cryoprotectant solutions were made up to final concentrations (after 1:1 dilution with larvae) of 10% ethylene glycol, 1% polyvinylpyrrolidone and either 0.2 or 0.4 M trehalose. Three cooling rates (0.5, 1 and 2 °C min−1 between −10 and −35 °C post-holding) were tested in an orthogonal design with the two cryoprotectants. Results indicate that control larvae out-performed all cryopreservation treatments for survival, feeding consumption and shell length parameters. However, larvae exposed to 0.4 M trehalose did considerably better than those exposed to 0.2 M trehalose, regardless of cooling rate conditions. Scanning electron and light microscopy observations were used to assess larval morphology and organogenesis, indicating that treatments with surviving larvae were morphologically and developmentally similar to control larvae.

Identification and quantification of two species of oyster larvae using real-time PCR

A real-time polymerase chain reaction (PCR) assay was developed for the identification and quantification of two oyster species: Ostrea edulis and Crassostrea gigas. Two sets of primers and TaqMan-MGB probes were designed, based on partial sequences of the 16S rRNA gene. An amplification positive control system was also located in the 18S rRNA gene sequences. Closely related species of oysters and other bivalves, known to co-occur with the target species in European waters, were used to test the assay for cross-reactivity. The assay designed was specific for the target species and no signal or no significant signal was detected for all non-target species tested. The high sensitivity of this method was demonstrated since it is possible to detect just one larva (150–200 μm size) of each species even when it is present with others. Furthermore, this assay provided an acceptable quantification of the number of spiked larvae (1, 10 and 100 larvae) in plankton samples employing a standard curve for larvae.

Interactive Effects of Mosquito Control Insecticide Toxicity, Hypoxia, and Increased Carbon Dioxide on Larval and Juvenile Eastern Oysters and Hard Clams

Mosquito control insecticide use in the coastal zone coincides with the habitat and mariculture operations of commercially and ecologically important shellfish species. Few data are available regarding insecticide toxicity to shellfish early life stages, and potential interactions with abiotic stressors, such as low oxygen and increased CO2 (low pH), are less understood. Toxicity was assessed at 4 and 21days for larval and juvenile stages of the Eastern oyster, Crassostrea virginica, and the hard clam, Mercenaria mercenaria, using two pyrethroids (resmethrin and permethrin), an organophosphate (naled), and a juvenile growth hormone mimic (methoprene). Acute toxicity (4-day LC50) values ranged from 1.59 to >10mg/L. Overall, clams were more susceptible to mosquito control insecticides than oysters. Naled was the most toxic compound in oyster larvae, whereas resmethrin was the most toxic compound in clam larvae. Mortality for both species generally increased with chronic insecticide exposure (21-day LC50 values ranged from 0.60 to 9.49mg/L). Insecticide exposure also caused sublethal effects, including decreased swimming activity after 4days in larval oysters (4-day EC50 values of 0.60 to 2.33mg/L) and decreased growth (shell area and weight) in juvenile clams and oysters after 21days (detected at concentrations ranging from 0.625 to 10mg/L). Hypoxia, hypercapnia, and a combination of hypoxia and hypercapnia caused mortality in larval clams and increased resmethrin toxicity. These data will benefit both shellfish mariculture operations and environmental resource agencies as they manage the use of mosquito control insecticides near coastal ecosystems.

Identification and Functional Characterization of Two Executioner Caspases in Crassostrea gigas

Caspase-3 and caspase-7 are two key effector caspases that play important roles in apoptotic pathways that maintain normal tissue and organ development and homeostasis. However, little is known about the sequence, structure, activity, and function of effector caspases upon apoptosis in mollusks, especially marine bivalves. In this study, we investigated the possible roles of two executioner caspases in the regulation of apoptosis in the Pacific oyster Crassostrea gigas. A full-length capase-3–like gene named Cgcaspase-3 was cloned from C.gigas cDNA, encoding a predicted protein containing caspase family p20 and p10 domain profiles and a conserved caspase active site motif. Phylogenetic analysis demonstrated that both Cgcaspase-3 and Cgcaspase-1 may function as effector caspases clustered in the invertebrate branch. Although the sequence identities between the two caspases was low, both enzymes possessed executioner caspase activity and were capable of inducing cell death. These results suggested that Cgcaspase-3 and Cgcaspase-1 were two effector caspases in C. gigas. We also observed that nucleus-localized Cgcaspase-3, may function as a caspase-3–like protein and cytoplasm-localized Cgcaspase-1 may function as a caspase-7–like protein. Both Cgcaspase-3 and Cgcaspase-1 mRNA expression increased after larvae settled on the substratum, suggesting that both caspases acted in several tissues or organs that degenerated after oyster larvae settlement. The highest caspase expression levels were observed in the gills indicating that both effector caspases were likely involved in immune or metabolic processes in C. gigas.

Correction: Oyster Larvae Settle in Response to Habitat-Associated Underwater Sounds

Two funding organizations and grants were incorrectly omitted from the Statement. The Statement should read: Funding was provided by National Science Foundation Grants OCE-1234688 and DDIG-1210292, PADI Foundation Grant 5145 and a National Shellfisheries Association Melbourne R. Carriker Student Research Grant. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Technological Constraints During the First 40 Years of Eastern Oyster Crassostrea virginica Aquaculture

This article focuses on early efforts to culture eastern oyster larvae to settlement. Initial experiments were performed in 1878 and 1879 by Brooks, the first researcher to produce fertilized eggs. The subsequent challenge was to rear the microscopic larvae to settlement by feeding them and changing their culture water without losing them. Researchers like Ryder struggled with these problems, devising a number of filters and water circulation schemes, none of which were practical. Ryder eventually abandoned laboratory work and invented extensive and imaginative, but commercially unsuccessful, field trials to cultivate larvae in ponds and sluiceways. Subsequently, the Nelsons in New Jersey in the early 1900s tried similar experiments, ultimately focusing on understanding larval biology in nature and on predicting when naturally spawned larvae would settle so that settlement surfaces could be provided expeditiously. A breakthrough came in 1920 when Wells used a centrifuge to separate oyster larvae from old culture water, transferring the concentrated larval mass to new culture water. Wells then developed a system of culture vessels that enabled millions of competent larvae to be reared to settlement. Subsequently, researchers were able to study issues that enhanced the industrial culture of larvae of many bivalves, not just oysters.

FLUORESCENT LAMP LIGHT INTENSITY ON THE EMBRYOGENESIS DEVELOPMENT AND THE SURVIVAL OF PEARL OYSTER (Pinctada maxima) LARVAE

&lt;p&gt;One of the important factors in determining the success of pearl oyster (Pinctada maxima) culture is the quality and quantity of larvae produced in brood stock spawning process in the laboratory. Problems were often found in larval rearing and larvae attachment to the substrate that were low in quality and little number of larvae. The study purposes were observe the embryogenesis development and the survival rate of pearl oyster larvae under different fluorescent lamp light intensities. The study was conducted in August 1&lt;sup&gt;nd&lt;/sup&gt; – 30&lt;sup&gt;th&lt;/sup&gt;, 2011 in Sambelia Bumi Gemilang Hamparan Mutiara laboratory, East Lombok. Results revealed that different in light intensities effected the survivorship of the pearl oyster larvae significantly (p&amp;lt;0.01). Honest Significant Difference (HSD) test indicated that the highest survival rate occurred in dark condition (dark treatment) of 38%, followed by intensity of 10 watts (34.67%), 5 watts (30.67%) and 15 watts (4.66%) resfectively&lt;/p&gt; &lt;p&gt;Keywords: embryogenesis development, survivorship, pearl oyster (&lt;span style="text-decoration: underline;"&gt;Pinctada&lt;/span&gt; &lt;span style="text-decoration: underline;"&gt;maxima&lt;/span&gt;) larvae, fluorescent lamp light intensity&lt;/p&gt;

FLUORESCENT LAMP LIGHT INTENSITY ON THE EMBRYOGENESIS DEVELOPMENT AND THE SURVIVAL OF PEARL OYSTER (Pinctada maxima) LARVAE

One of the important factors in determining the success of pearl oyster (Pinctada maxima) culture is the quality and quantity of larvae produced in brood stock spawning process in the laboratory. Problems were often found in larval rearing and larvae attachment to the substrate that were low in quality and little number of larvae. The study purposes were observe the embryogenesis development and the survival rate of pearl oyster larvae under different fluorescent lamp light intensities. The study was conducted in August 1nd – 30th, 2011 in Sambelia Bumi Gemilang Hamparan Mutiara laboratory, East Lombok. Results revealed that different in light intensities effected the survivorship of the pearl oyster larvae significantly (p&lt;0.01). Honest Significant Difference (HSD) test indicated that the highest survival rate occurred in dark condition (dark treatment) of 38%, followed by intensity of 10 watts (34.67%), 5 watts (30.67%) and 15 watts (4.66%) resfectively Keywords: embryogenesis development, survivorship, pearl oyster (Pinctada maxima) larvae, fluorescent lamp light intensity