Winged Pearl Oyster Pteria Penguin Research Articles

Exploring diurnal and nocturnal valve gaping behavior in winged pearl oyster Pteria penguin juveniles

The diurnal and nocturnal valve gaping behavior of the pearl oyster Pteria penguin was characterized through video analysis aided by open-source software. Juvenile pearl oysters were video-recorded for 48 hours under laboratory conditions, using commonly used surveillance hardware. The direct measuring of the distance changes between the two valve edges effectively revealed the pearl oysters’ tendency to open their valves wider at night-time, than during day-time. Moreover, the differences observed were also attained at the individual level. The description for the first time of this behavior has broader implications for the research in pearl oyster aquaculture. Moreover, it introduces a non-invasive tool for comprehensive assessment of adult oyster behavior.

Effect of fresh and spray-dried microalgal diets on the growth, digestive enzymatic activity, and gut microbiota of juvenile winged pearl oyster Pteria penguin

The effects of fresh and spray-dried microalgal diets on the growth, digestive enzymatic activity, and gut microbial community were investigated in juveniles of the winged pearl oyster Pteria penguin. A total of 240 pearl oysters were fed either live or spray-dried unialgal diets of the species Isochrysis zhanjiangensis and Platymonas subcordiformis at a final concentration of 150,000 cells/mL. The experiment was performed over 28 days in triplicate feeding trials under laboratory conditions. At the end of the feeding trials, the hepatopancreas and gut tissue were dissected to quantify the digestive enzymatic activity and analyze the gut bacterial community. The survival rate of the oyster juveniles in all trials was > 90 %. Moreover, the animals fed a spray-dried P. subcordiformis diet exhibited slightly higher shell growth rates. However, the mean shell height and the total wet weight were not significantly different among all experimental groups (P > 0.05). The digestive enzymes amylase, pepsin, and lipase exhibited significantly higher activity levels in oysters fed spray-dried diets than in those provided live microalgae. The different diets also provoked changes in the gut microbiota of the pearl oysters. A total of 27 phyla and 482 genera were detected within all groups examined; the Proteobacteria, Cyanobacteria, Bacteroidetes, and Spirochaetes were the dominant phyla. In general, spray-dried diets exhibited a higher number of operational taxonomic units (OTUs), Chao1, and Simpson and Shannon indices, implying the ability of these diets to promote high microbial biodiversity. Thus, these diets benefitted the maintenance of the intestinal micro-ecological balance and health. The study findings will help optimize intermediate culture technology and management of P. penguin juveniles.

Spatio-Temporal Variation in Growth Performance and Condition of the Winged Pearl Oyster Pteria penguin

Environmental conditions can strongly influence the growth performance of pearl oysters and affect pearl farm production schedules. Growth and condition index (CI) of two age cohorts of Pteria penguin were measured for 13 months to investigate differences in growth performance between four culture sites within the northern (Vava’u) and southern (Tongatapu) island groups of the Kingdom of Tonga. Environmental conditions were also measured at culture sites and used to explore potential effects on oyster growth and condition. Between island groups, growth performance of P. penguin was superior at northern sites and was most strongly related to higher water temperatures at these sites. Within the southern island group, growth performance varied significantly between sites and may be driven by differences in wave energy. Monthly growth rates (GM) of P. penguin also showed significant temporal variation related to age and environmental conditions. This study demonstrated significant variation in the growth performance of P. penguin at latitudinal and local scales and suggests that in oligotrophic marine environments with minimal terrestrial inputs, such as Tonga, water temperature and wave exposure may be the primary environmental conditions influencing the growth performance of P. penguin. This study therefore recommends that optimal culture sites for P. penguin in Tonga are characterized primarily by warmer water temperatures (25–30°C) and low wave exposure (<15 joules m2 day–1). Culture of P. penguin at sites with more suitable environmental conditions enables pearl production to begin up to 34.2 % (6.5 months) earlier than at less-suitable sites and this may greatly influence mabé pearl farm profitability and feasibility.

Variation of Element Concentration in Nacreous Marginal Area and Central Area of Pteria penguin Shell

Concentrations of 29 elements were analyzed in the marginal area and central area of the shell nacreous layer of the winged pearl oyster Pteria penguin using a laser ablation inductively coupled plasma mass spectrometer. Color of the two shell areas was determined using the color parameter values of lightness, greenness/redness, and blueness/yellowness. It is shown that the concentrations of the elements and the nacreous color are different in the marginal area and central area. The concentrations of Mg, P, B, Li, Cu, and Mo are significantly correlated with lightness and differently distributed in the two shell areas (P < 0.05). The concentration of Na and Mg is significantly related to greenness/redness and differently distributed in the two shell areas (P < 0.05). The concentration of Na, Mg, P, B, Li, and Mo is significantly related to blueness/yellowness and differently distributed in the two shell areas (P < 0.05). The concentration of Mg significantly related to lightness, greenness/redness, and blueness/ yellowness and differently distributed in the two shell areas (P < 0.05). This study provides a new perspective to illustrate the mechanism of color change between the marginal and central areas.

Production Cost of the Farm-Ready Pearl Oyster Pteria penguin Used for Mabé Pearl Production in the Kingdom of Tonga

Mabe pearl (half-pearl) culture provides rural livelihood opportunities in the South Pacific and is a low-tech alternative to capital and labor-intensive round pearl culture. The Kingdom of Tonga is unique among the pearl-producing countries of the South Pacific in focusing on mabe pearl culture using the winged pearl oyster Pteria penguin. The Tongan mabe pearl sector is developing rapidly and stimulated by routine supply of spat to mabe pearl farmers, from the government hatchery at no cost. It is likely that some level of cost recovery for spat supply will be considered as the sector strengthens, but information on hatchery production costs is limited. This study determined the costs of operating the government pearl oyster hatchery in Tonga and developed an economic model to assess the production cost of juvenile oysters. Modeling was based on a single annual hatchery run generating 6,600 oysters from the ocean-based nursery for delivery to commercial pearl farms. Estimated capital cost was USD 19,079 (excluding government buildings and chattels), and the major production costs were hatchery labor (37%), capital purchase and replacement (20%), and nursery labor (10%). Total annual costs for the pearl oyster hatchery were USD 13,263, equating to a cost of USD 2.01 per oyster supplied to farmers in Tonga. Given significant annual profits of around USD 9,338 that can be generated from 100 harvested oysters, there is justification for cost recovery. Results will be valuable to key stakeholders and have regional relevance for hatchery production of high-value aquaculture commodities.

The Effect of Light on the Locomotion and Byssal Reattachment of Winged Pearl Oyster Pteria Penguin (Röding, 1798) Juveniles

The present study describes the effects of various wavelengths of light on locomotion and byssal reattachment activities in the pearl oyster Pteria penguin, the most widespread cultured winged oyster for the production of valuable mabé pearls. Responses of pearl oysters to light have not yet been carefully observed and documented, despite the fact that light is known to influence the positioning of animals within the water column subject to local environmental conditions. To appropriately assess oyster movements and subsequent byssal reattachment, juveniles were filmed during unnatural light–dark cycles, alternating light and darkness every 6 h. Another experiment, to observe reactions to different light colors, was carried out by subjecting juveniles to either red or blue light during a continuous observation period of 24 h. Byssal reattachment for each juvenile was recorded at the end of each observation period. Light, independent of its color, strongly inhibited both locomotion and byssal reattachment activities in juveniles. Moreover, locomotion was observed to be unrelated to the shell size, but it is suggested that a large byssus may be responsible for inhibiting movement by preventing complete extension of the foot. High byssal reattachment rates to substrata under darkness in oyster juveniles is an important factor to take in consideration after detachment events during cleaning or when transplanting seeds to farm grounds.

Morphological variations of the winged pearl oyster Pteria penguin (Roding, 1798) from South China Sea

The present study was undertaken to evaluate the morphological variations of Pteria penguin (Roding, 1798) in wild as well as cultured populations from South China Sea. A total of 307 samples were collected from five different geographic locations comprising three wild (Pop. 1, 2 and 4) and two cultured (Pop. 3 and 5) populations and 10 measured traits were analysed. Principal component analysis (PCA), discriminant analysis and cluster analysis were used to evaluate the morphological variations in the collected samples. Results showed a low intra-population variation within the five sampled populations. Multivariate analyses indicated that the five populations were more or less differentiated on the basis of body characters, particularly those related to major dimensions of the shell outline and their ratios. Discriminant analysis revealed that the overall random assignment of individuals into their original groups was high (81.8%), indicating that these populations are highly divergent from each other. The proportion of individuals correctly classified into their original groups was 96.9, 76.7, 75.0, 78.0 and 82.0% for populations 1, 2, 3, 4 and 5 respectively. Cluster analysis showed highest morphological variation between Pop.1 and Pop. 2. All other populations (Pop.3, Pop.4 and Pop.5) were found to be morphologically similar and consistent with the respective geographical location. Results of the present study will be of use in resource assessment and management of P. penguin in the South China Sea.

Characterization of transcriptome and identification of biomineralization genes in winged pearl oyster (Pteria penguin) mantle tissue

The winged pearl oyster Pteria penguin is a commercially important marine pearl oyster species, with pearls that are quite different from those of other pearl oysters. Among such species, mantle tissue is the main organ responsible for shell and pearl formation, a biomineralization process that is regulated by a series of genes, most of which remain unknown. In this study, we sequenced and characterized the transcriptome of P. penguin mantle tissue using the HiSeq 2000 sequencing platform. A total of 93,204 unique transcripts were assembled from 51,580,076 quality reads, with a mean length of 608bp, and 40,974 unigenes were annotated. The sequence data enabled the identification of 79,702 potential single nucleotide polymorphism loci and 4345 putative simple sequence repeat loci. A total of 71 unique transcripts were identified homologous to known biomineralization genes, including mantle gene, nacrein, pearlin, pif, chitinase, and shematrin, of which only 3 were previously reported in P. penguin. qPCR analysis indicated that 10 randomly selected biomineralization genes were much more highly expressed in mantle tissue than in the other tissues. In addition, 30 unique sequences were identified as highly expressed, with FPKM values of >3000, and most of these were biomineralization-related genes, including shematrin family genes, a jacalin-related lectin synthesis gene, calponin-2, and paramyosin. These findings will be useful for future studies of biomineralization in P. penguin, as well as in other Pteria species.

Sexual and mating system in a caridean shrimp symbiotic with the winged pearl oyster in the Coral Triangle

AbstractFor symbiotic crustaceans, theory predicts that monogamy is adaptive when species inhabit scarce, relatively small and morphologically simple hosts in tropical environments where predation risk away from hosts is high. We tested this prediction in the shrimp Paranchistus pycnodontae, which inhabits the mantle cavity of the winged pearl oyster Pteria penguin in the Coral Triangle. In various symbiotic crustaceans, males are smaller than females, and this sexual dimorphism has been used as evidence of sex change (protandry) in these organisms. Preliminary observations in Pa. pycnodontae suggested that males were smaller than females. Thus, we first investigated the sexual system of Pa. pycnodontae to determine if the species was protandric. Morphological identification and size frequency distributions indicated that the population comprised small males, small immature females and larger mature females, which was confirmed by dissections. No transitional individuals were found. Thus, Pa. pycnodontae is a gonochoric species with reverse sexual dimorphism. Pa. pycnodontae inhabit as heterosexual pairs in the mantle cavity of hosts more frequently than is expected by chance alone. Pairing was size assortative; both carapace length and propodus length of the major cheliped were positively correlated between males and females forming pairs. Males occur with females in the same host, independent of the female gravid condition or of the stage of development of the brooded eggs. Lastly, the major cheliped did not exhibit positive allometry in males. All the available information suggests that Pa. pycnodontae has adopted a socially monogamous mating system with males and females forming exclusive pairs from other adults. Symbiotic shrimps can be used as a model system to understand behavioural diversity within socially monogamous marine invertebrates.

Seasonal Changes in Recruitment ofPteria penguinin North Queensland, Australia

Spat recruitment of the winged pearl oyster Pteria penguin, in relation to season, substrate type, and depth was investigated at Orpheus Island in north Queensland for 27 mo, from February 2008 to April 2010. Two substrate types (70% shade cloth and open-weave polypropylene mesh bags) were deployed at 2 depths (4 m and 6 m) and checked every 6 wk for 3 spawning seasons to determine any differences in quantity of spatfall between these factors. No significant difference was found in spat recruitment between substrate types (P = 0.158) or depth (P = 0.349), although there was a significant seasonal effect on spat recruitment (P < 0.001), with a peak in the quantity of spatfall in late summer, from February to March, and no spat collected in the winter to spring (July to October). Maximum settlement of spat was 10.2 spat per mesh bag collector in February 2008. Recruitment was significantly reduced (P < 0.001) during the 2010 spawning season as a result of disturbance from severe storms generated by tropical cyclone Olga in late January.