Pearl Oyster Pinctada Radiata Research Articles

Analysis of Nutritional Composition of the Pearl Oyster Pinctada radiata as a New Mediterranean “Bioresource” for Human Consumption

Protein intake inadequacy has been considered to be one of the major nutritional problems worldwide for many years and it appears that this issue will continue to increase sharply in the coming decades. This deficiency can be partly overcome by the effective use of protein-rich bioresources such as mollusks. In the present study, the oyster Pinctada radiata, collected from the Aegean Sea, is fully nutritionally characterized as a new non-indigenous bioresource concerning mainly its protein, carbohydrate and fat composition during the different seasons of the year. The results showed that the protein content of the pearl oyster is at satisfactory levels, with its maximum value in winter and minimum in summer. On the contrary, its fat and carbohydrates are at low levels, with their maximum values in the summer period. Regarding the profile of fatty acids, polyunsaturated fats are in the highest proportion, which is very encouraging, as a diet rich in this kind of fat is desired. The entire nutritional profile of the studied oyster demonstrates its high nutritional value and supports its possible use as a “new” seafood source for human consumption in the Mediterranean.

Hazardous impacts of heavy metal pollution on biometric and biochemical composition of pearl oyster Pinctada radiata from five sites along Alexandria coast, with reference to its potential health risk assessment

This study investigated the effect of heavy metals on the pearl oyster Pinctada radiata from 5 sites along the coast of Alexandria, with focus on its ecological health and potential risks to human consumption. Pollution results showed that Abu-Qir had the highest Cu and Cd values. Montaza and Eastern Harbor had the highest Fe and Pb values, respectively. Statistically, differences in metal concentrations among study sites were significant (p < 0.05). Non-carcinogenic risk (TTHQ) of tested metals and carcinogenic ones of Cd and Pb showed “high risk” on human health by consuming pearl oysters. Morphometric measurements and condition indices were studied to assess growth patterns and health in relation to heavy metals exposure. Key findings showed detectable declines in size and condition index in Eastern Harbor, whereas Abu-Qir recorded the highest values. This condition index performance presented Abu-Qir, Mammora, and Miami as ideal locations for spat collection and oyster rearing, potentially enhancing Egyptian pearl farming. Average values of spatial proximate contents of pearl oyster showed that it was rich in proteins (33.07–58.52%) with low fat content (1.39–1.87%) and carbohydrates (9.72–17.63%). Biochemical composition of pearl oyster demonstrated its high nutritional value which supported its promotion as a functional food for human consumption. The calorie content of pearl oyster was less than 2 Kcal, making this species an alternative source of healthy food to reduce obesity. Regression analysis indicated that Cu, Cd, and Pb had significant effect on 2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, calories, vitamins, and pigment content of the collected oysters.

First genetic survey on the invasive rayed pearl oyster Pinctada radiata (Leach, 1814) populations of the Balearic Islands (Western Mediterranean)

A survey of the invasive pearl oyster Pinctada radiata along the Balearic Archipelago was conducted based on the COI mitochondrial marker. Results confirmed the identity of the specimens as P. radiata. The Balearic populations are certainly of Indo-Pacific origin but not from the Persian Gulf nor from other introduced populations in the eastern or central Mediterranean, therefore the precise origin remains to be discovered. Despite the small number of samples from the Persian Gulf compared to the Mediterranean, the haplotype diversity is higher in the native populations compared to the non-native.

Deep behavioral impairment in the pearl oyster Pinctada radiata exposed to anthropogenic noise and light stress

The pearl oyster Pinctada radiata is an iconic species in the Arabian Gulf, which is one of the ecosystems most at risk in the world because of the multiple sources of pollution it faces. Alongside chemical pollution, the Gulf is ranked first with regard to noise and light pollution, and pearl oyster populations are at risk. The impact of these latter types of pollution on marine invertebrates is still poorly known. We used the difference in noise and brightness that can exist between a very quiet room without artificial lighting and a standard laboratory room equipped with a standard aquarium as a testbed to explore the possible impact of noise and light pollution on the behavioral and biological traits of Pinctada radiata without added chemical exposure. During an experiment that lasted 2.5 months, we analyzed their grouping behavior, valve activity, biological rhythm, growth rate and spawning activity. In the standard aquarium kept in the laboratory room, the oysters dispersed instead of regrouping as in their natural environment, regrouping which was observed in the quiet room. They stayed closed longer, the opening amplitude of their valves was systematically lower, and in the closed position, they squeezed their valves more tightly when subjected to noise and light pollution. Their daily opening rhythm was strongly structured by switching the electric light on and off, and females showed significantly less egg-laying behavior. In conclusion, seemingly innocuous human activities can lead to very significant alterations in pearl oyster behavior. We propose that it could have significant effects on populations and ecosystems.

Zrakasta bisernica Pinctada radiata (Leach, 1814) (Bivalvia: Pteriidae) u istočnom dijelu Jadrana – novija opažanja

Adriatic Sea as a part of the Mediterranean is settled by many introduced species which extend their range northward. Among them is the rayed pearl oyster Pinctada radiata, a mollusk of Indo-Pacific origin that colonises habitats throughout the Mediterranean. P. radiata established a population in a fish farm on the island of Mljet in the Adriatic Sea, which was observed in 2017. To determine the status of the population, 48 specimens of P. radiata were randomly sampled from the ropes of a fish farm in 2019. Morphometric parameters were determined using a digital calliper. The recorded parameters showed that shell height ranged from 50.55 mm to 72.98 mm, shell length from 46.66 mm to 71.15 mm, and shell width from 19.98 mm to 58.54 mm. During additional visual survey in 2020 the presence of the spat within population at Mljet fish farm was not observed. It appears that only adult specimens are present, and it is unclear if the population is reproducing. In addition, P. radiata spat was observed in the shallow waters of Lokrum Island in 2021 and 2022, indicating the possibility of survival of larvae naturally dispersing from pre-existing populations. An adult specimen of P. radiata was also observed in Mali Ston Bay on two occasions, in 2009 and 2021. P. radiata, a highly adaptable species that tolerates a wide range of environmental factors, has successfully colonised new habitats.

New records of introduced species in the Mediterranean Sea (April 2023)

This Collective article reports 17 introduced species and 22 new locations for these species in the Mediterranean Sea. The reports are from three different Marine Strategy Framework Directive (MSFD) subregions (Aegean-Levantine Sea, Adriatic Sea and Western Mediterranean Sea) and the Sea of Marmara and cover ten different countries. The goal of consistent and detailed reporting of introduced species is to complement the existing species inventories and serve as a basis for establishing monitoring strategies and other conservation measures. Some of the reports from this article are the first species records for the Mediterranean Sea, namely the green alga Udotea flabellum from the Aegean Sea (Turkey) and the deepbody boarfish Antigonia capros from the Balearic Sea (Spain). In addition, new records of introduced species are included for different seas, namely the moon crab Matuta victor for the Aegean Sea (Greece), the whale shark Rhincodon typus and the lionfish Pterois miles for the Alboran Sea (Spain), the almaco jack Seriola rivoliana for the Tyrrhenian Sea (Italy), and the hound needlefish Tylosurus crocodilus for the Adriatic Sea (Italy). Furthermore, reports on first country records are included: the red alga Colaconema codicola from Slovenia, the nudibranch Melibe viridis from Bosnia and Herzegovina, the lionfish Pterois miles from Montenegro, and the goldstripe sardinella Sardinella gibbosa from Syria, which also represents a second record for the Mediterranean Sea. Furthermore, the occurrence of the scleractinian coral Oculina patagonica was noted in Gulf of Lion (France). Four polychaete species, namely Leodice antennata, Timarete punctata and Branchiomma bairdi, are reported from the vermetid reef habitat and two of them (L. antennata and B. bairdi) are also recorded for the first time in Lebanon. Evidence for established populations of the Asian date mussel Arcuatula senhousia in the Sea of Marmara (Turkey) and the rayed pearl oyster Pinctada radiata around the island of Sardinia (Italy) is provided.

Aneuploidy in the Pearl Oyster Pinctada radiata (Leach, 1814): Evidence for Nonrandom Chromosome Loss and Gain in Marine Bivalves

Aneuploidy, or presence of an abnormal number of chromosomes, has been commonly observed in marine bivalves. This phenomenon has also been shown to be negatively correlated with growth and survival rates in several species of oysters and clams. The impact of pollutants on the aneuploidy level in bivalves has also been previously demonstrated. Over the past two decades, evidence of nonrandom chromosomal loss has been demonstrated, with the identification of the missing chromosomes in aneuploid karyotypes reported in several species. The results have shown that only a few pairs were preferentially affected by the loss of one homologue chromosome in different species of oysters and clams. Recently, during the genotoxicity assessment of the marine environment in Qatar using the pearl oyster Pinctada radiata (Leach, 1814) as model and surrogate species, we observed hypodiploid and hyperdiploid karyotypes. Hyperdiploidy was more frequent, which is highly uncommon in bivalves. The identification of the extra and missing chromosomes in aneuploid cells showed that pairs 4, 5, 12, and 13 were found to be more susceptible than others in having an extra individual chromosome. The same set of pairs showed a tendency to lose one homologue chromosome. Several hypotheses on the preferential chromosomal susceptibility in bivalves, in general, are discussed.

Early embryonic developmental stages of the pearl oyster Pinctada radiata (Leach, 1814) from Lattakia coast, Syria

Matured brood stock of Pinctada radiata were collected from Afamia region in Lattakia coast. Three sets of spawning and larval rearing experiments were conducted during the period from July - October 2016 and the pearl oysters were successfully spawned at average temperature 31.5 ± 0.26 °C. After about 60 min, oocytes presented no germinal vesicle, rounded and measured 47.5-55 μm with an average of 50 ± 3.95 μm in diameter. Early stages of embryonic development were recorded and the polar body was observed 15 min after fertilization, trefoil stage at 1 h and 30 min, morula at 3 h and 30 min, blastula at 4 h and 50 min, gastrula at 6 h, trochophore larva at 8 h and veliger larva at 20 h. Veliger larva dimensions were 61.88 ± 3.82 μm for average length along the antero-posterior axis and 51.26 ± 5.14 μm for height along the dorso-ventral axis.

Evaluation of hemolymph biochemical properties, clearance rate, bacterial microbiota and expression of HSP genes of gulf pearl oyster Pinctada radiata in response to salinity changes

Hypo-salinity exposure is a serious concern for bivalve aquaculture, with profound effects on the animals’ physiological condition. The present study aimed to evaluate the influence of low-salinity exposure on the clearance rate, total heterotrophic marine bacteria and total Vibrio count in flesh, as well as the biochemical parameters of hemolymph and heat shock protein (HSP) gene expression, in Pinctada radiata. To this end, the oysters were reared for 14 days at salinities of 40 (control group), 35, 30, 25 and 20 PSU. Results indicated that low salinity led to a significantly lower clearance rate, with the lowest clearance rate observed at 20 PSU. However, no significant differences were found among the groups in the total heterotrophic marine bacteria, calcium concentration, aspartate aminotransferase (AST), alanine aminotransferase (ALT) or alkaline phosphatase (ALP) levels. In addition, the results demonstrated that the total Vibrio count increased significantly in oysters exposed to the hypoosmotic condition. A reduction in glucose concentration was observed in the 25 and 20 PSU groups compared to the other experimental groups. In addition, the highest survival rate was found in the 40 and 35 PSU groups. Based on q-RT-PCR results, HSP70 and HSP90 mRNA levels were significantly up-regulated by low-salinity exposure, while the expression of HSP20 mRNA was remarkably down-regulated in the 35 and 30 PSU salinity groups. The present study shows that pearl oysters tolerate a wide range of salinities (40–20 PSU), whereas optimal salinity for oyster culture ranges from 30 to 40 PSU. These results also provide a better understanding of the feeding behavior and physiological changes of P. radiata in response to salinity changes.

Decline in oyster populations in traditional fishing grounds; is habitat damage by static fishing gear a contributory factor in ecosystem degradation?

The territorial waters of Qatar once supported dense assemblages of the pearl oyster Pinctada radiata. The oysters settled on a patchy network of limestone platforms (hairãt) and provided a suite of ecosystem services to the surrounding marine environment. Commercially important fish species are associated with hairãt and as a result, industrial fishing with traps focused on these areas. This study has shown that heavily-fished areas are presently in a state which can be considered non-favorable to conservation while areas closed to fishing are recovering. It is probable that an increase in fishing activity using traditional Gargoor traps and grapple retrieval are responsible for the current ecological status of the hairãt. The intensity in trap fishing appears to be having a detrimental effect on species such as corals, sea grasses and oysters. The decline in the standing stock of oysters is dramatic with an estimated reduction ratio of 580:1 between 2002 and 2016. As fishing damage appears to be a significant contributor to these losses, measures such as spatial protection of productive shallow offshore habitats and restriction on fishing effort are urgently required to address the decline. Strategic oyster stock enhancement through the re-seeding of selected areas could boost the recovery of damaged hairãt as P. radiata ecosystem services return.

English

English

First genotoxicity assessment of marine environment in Qatar using the local Pearl oyster Pinctada radiata

The Arabian Gulf countries’ marine environment has been subjected to increasing industrial development and anthropogenic pressure, leading to the growing introduction of contaminants into the marine environment, with a large percentage of those consisting of potentially genotoxic substances. In this study, we performed the first integrated assessment of some of the genotoxic contaminants present in the Qatari marine environment and their biological effect, by the evaluation of the aneuploidy levels on the native pearl oyster Pinctada radiata. The aneuploidy levels varied significantly between sampling sites but not between sampling seasons. However, an important spatial and temporal variability of the bioaccumulated contaminants in the P. radiata tissues was observed, leading us to suggest that the high levels of aneuploidy found in the two harbor sampling sites could be a consequence of a local chronical contamination and not a direct response to the temporal fluctuations of the bioavailable contaminants to P. radiata.

Gill Histopathological Effects of PAHs on Adult Pearl Oyster, &amp;lt;i&amp;gt;Pinctada radiata&amp;lt;/i&amp;gt; at Al-Khiran Coast in Kuwait

The hazardous effect of water pollution on the histopathology of gill organ of the pearl oyster, Pinctada radiata was studied with respect to polycyclic aromatic hydrocarbon contamination in Al-Khiran coast at Kuwait. Thirty oyster samples from each site, site one where dead oysters were located, site two which is two kilometers away from site one and the control site which is ten kilometers away from site one were collected from Al-Khiran area where a massive number of dead oysters were reported. The gills of oysters were immediately removed and transferred to Bouin’s solution for fixation and then processed for sectioning, staining and mounting and gill tissues were ready for examination. Histopathological changes in gills of oysters exposed to polycyclic aromatic hydrocarbons in site one and site two included necrosis and edemas of branchial lamellae, complete degeneration of gill filaments, loss of regular shape and haemolysis, and inflammation. Gill tissues of oysters from the control site had normal appearance. The study showed a clear evidence that PAHs caused severe histopathological changes in gills of pearl oyster Pinctada radiata.

Assessment of trace elements in the shell layers and soft tissues of the pearl oyster Pinctada radiata using multivariate analyses: a potential proxy for temporal and spatial variations of trace elements

Concentrations of trace elements (Cd, Cu, Ni, Pb, V, and Zn) were determined in the soft tissues (adductor muscle and gills) of the pearl oyster Pinctada radiata and surficial sediments from two sampling sites located in the northern part of the Persian Gulf by Graphite Furnace Atomic Absorption Spectrophotometer (GFAAS). Moreover, the levels of Li, Mg, Al, Mn, Fe, Cu, Sr, Ba, Pb, and Zn were measured in two shell layers (prismatic and nacreous) using Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-ICP-MS). There were significant differences between the sampling sites with regard to mean concentrations of Cu, Mn, and Al in the prismatic layers of the shells. But in terms of the soft tissues, only in the case of Ni accumulation in the muscle significant differences between the sites could be observed. No significant differences could be found between the sites from the elements concentrations in the sediments point of view. The levels of Cd, Cu, Ni, and Zn in the gills were markedly higher than those in the muscle. Concentrations of Mn, Mg, Li, and Cu in the prismatic layer were significantly higher than in the nacreous but the reverse case could be found for Sr. The patterns of metal occurrence in the selected tissues, shell layers, and sediments exhibited the following descending order: Zn, Ni > Cd, Cu > V, and Pb and Zn, Ni, Cd > Cu, V, and Pb for muscle and gills, respectively; Zn > Cu, Ni, Pb, Cd, and V for sediments; Mg > Sr, Mn, Li, Al, Fe, Ba, Cu, Pb, and Zn for the prismatic layer; and Sr, Mg > Mn, Al, Fe, Li, Ba, Cu, Pb, and Zn for the nacreous layer. In most cases, the temporal variations of the elements levels in the prismatic layer were clearer than those in the nacreous layer (especially for Li, Mg, Mn, Pb, and Fe). Comparison of the gained data from this study with the other relevant researches shows that in most cases the levels of the elements in this investigation either fell within the range for other world areas or were lower. Generally, it can be concluded that the shell (especially prismatic layer) of P. radiata can be considered as a suitable proxy for temporal and spatial variations of the trace elements (and probably some environmental parameters) in the study area.

Shell morphology and relative growth variability of the invasive pearl oyster Pinctada radiata in coastal Tunisia

The variability of shell morphology and relative growth of the invasive pearl oyster Pinctada radiata was studied within and among ten populations from coastal Tunisia using discriminant tests. Therefore, 12 morphological characters were examined and 34 metric and weight ratios were defined. In addition to the classic morphological characters, populations were compared by the thickness of the nacreous layer. Results of Duncan's multiple comparison test showed that the most discriminative ratios were the width of nacreous layer of right valve to the inflation of shell, the hinge line length to the maximum width of shell and the nacre thickness to the maximum width of shell. The analysis of variance revealed an important inter-population morphological variability. Both multidimensional scaling analysis and the squared Mahalanobis distances (D2) of metric ratios divided Tunisian P. radiata populations into four biogeographical groupings: the north coast (La Marsa); harbours (Hammamet, Monastir and Zarzis); the Gulf of Gabès (Sfax, Kerkennah Island, Maharès, Skhira and Djerba) and the intertidal area (Ajim). However, the Kerkennah Island population was discriminated by the squared Mahalanobis distances (D2) of weight ratios in an isolated group suggesting particular trophic conditions in this area. The allometric study revealed high linear correlation between shell morphological characters and differences in allometric growth among P. radiata populations. Unlike the morphological discrimination, allometric differentiation shows no clear geographical distinction. This study revealed that the pearl oyster P. radiata exhibited considerable phenotypic plasticity related to differences of environmental and/or ecological conditions along Tunisian coasts and highlighted the discriminative character of the nacreous layer thickness parameter.

Macrofauna associated with an introduced oyster, Pinctada radiata: Spatial scale implications of community differences

The macrozoobenthos associated with the introduced pearl oyster Pinctada radiata has been sampled at two different spatial scales of three sectors (order of hundreds of kilometres) and of eight localities (order of tens of kilometres). Moreover, the NW sector was selected to compare three localities with the presence of P. radiata (low density) and one locality where it was totally absent. The first design was hierarchical, with random localities nested within sectors; the second one was an asymmetrical factorial design, in which the presence/absence of Pinctada and hydrodynamism were considered. Similarity relationships were investigated by means of multivariate clustering, similarity percentage analysis and nm-MDS ordination; the two experimental designs have been tested by permutational MANOVA and analysis of dispersion (PERMDISP). Most of the variability of the associated zoobenthic community appeared to be mainly captured by local environmental factors; the meso-scale variability was more discriminating than differences at larger spatial scale. Large scale NW–SE biogeographic gradient may also have some effects in the assemblage composition. Although the whole arrangement of samples in the MDS plane showed a clear Bray-Curtis distance between the locality without Pinctada and all the remaining sites, pair-wise contrasts were not all significant. The factor “presence/absence” was not significant in this design, whereas the exposure was more indicative of differences in the local assemblage composition. These results may not confirm that the community structure variability is due to the impact of Pincata invasion because the potential and subtle community shift may be masked by the overwhelming influence of just the local environmental gradients. In spite of this, the introduced oyster may play the role of an engineer species at high densities, contributing to the complexity of the benthic habitat and influencing the trophic pattern of its fauna.

Comparative morphometric study of the invasive pearl oyster Pinctada radiata along the Tunisian coastline

In order to study the relative growth of the pearl oyster Pinctada radiata in Tunisia, a total of 330 individuals of this species were collected from six sites along the Tunisian coastline. Quantitative measurements of collected oysters were conducted for shell height, shell length, shell width, hinge length, height and width of the nacreous part and wet weight. The size structure of the sampled populations was described and the relative growth between different morphometric characteristics was estimated as allometric growth lines for the six P. radiata samples. It appeared that the majority of examined samples were dominated by large individuals that exceed a shell height of 42 mm. The maximum size (100.5 mm), recorded in Bizerta lagoon, is bigger than that recorded elsewhere in particular in the Red Sea. Size distribution analysis also showed that the majority of P. radiata samples were dominated by two or more size groups. Differences of allometric regression were found between the examined samples for the tested relationships. Moreover, the Factorial Discriminant Analysis, coupled with Ascending Hierarchic Classification, classified the sub-populations according to geographic locations.

Variations of trace metal concentrations in seawater and pearl oyster Pinctada radiata from Bahrain (Arabian Gulf)

Concentrations of seven trace metals in oysters ( Pinctada radiata) and paired seawater samples from two stations in Bahrain (Arabian Gulf) were determined every 6–8 weeks during the period March 1991–March 1992. The measured annual means in oysters were higher for Pb (7.64 μg g −1) and Cd (2.48 μg g −1) at an offshore Station 2, while Ni was higher in oysters at a nearshore Station 1. For Cu and Mn no differences were observed between oysters of both stations, however, Fe and Zn were higher in oysters of Station 1. No significant difference was observed in concentrations of trace metals in seawater of the nearshore or offshore stations or between individual metals. Seasonal distribution of metals in oysters and water indicated a tendency to increase towards the hot summer months (June, July-September). Generally, metal concentrations were higher in oysters irrespective of the station and the levels of Pb and Cd exceeded the WHO limits.