Differential community development of fouling species on the pearl oysters Pinctada fucata,Pteria penguin and Pteria chinensis (Bivalvia,Pteriidae)

Abstract

A field experiment documented the development of fouling communities on two shell regions, the lip and hinge, of the pearl oyster species Pinctada fucata, Pteria penguin and Pteria chinensis. Fouling communities on the three species were not distinct throughout the experiment. However, when each species was analysed separately, fouling communities on the lip and hinge of P. penguin and P. chinensis were significantly different during the whole sampling period and after 12 weeks, respectively, whereas no significant differences could be detected for P. fucata. There was no significant difference in total fouling cover between shell regions of P. fucata and P. chinensis after 16 weeks; however, the hinge of P. penguin was significantly more fouled than the lip. The most common fouling species (the hydroid Obelia bidentata, the bryozoan Parasmittina parsevalii, the bivalve Saccostrea glomerata and the ascidian Didemnum sp.) showed species-specific fouling patterns with differential fouling between shell regions for each species. The role of the periostracum in determining the community development of fouling species was investigated by measuring the presence and structure of the periostracum at the lip and hinge of the three pearl oyster species. The periostracum was mainly present at the lip of the pearl oysters, while the periostracum at the hinge was absent and the underlying prismatic layer eroded. The periostracum of P. fucata lacked regular features, whereas the periostracum of P. penguin and P. chinensis consisted of a regular strand-like structure with mean amplitudes of 0.84 μm and 0.65 μm, respectively. Although the nature and distribution of fouling species on the pearl oysters was related to the presence of the periostracum, the periostracum does not offer a fouling-resistant surface for these pearl oyster species.     

Differential community development of fouling species on the pearl oysters Pinctada fucata, Pteria penguin and Pteria chinensis (Bivalvia, Pteriidae)

A field experiment documented the development of fouling communities on two shell regions, the lip and hinge, of the pearl oyster species Pinctada fucata, Pteria penguin and Pteria chinensis. Fouling communities on the three species were not distinct throughout the experiment. However, when each species was analysed separately, fouling communities on the lip and hinge of P. penguin and P. chinensis were significantly different during the whole sampling period and after 12 weeks, respectively, whereas no significant differences could be detected for P. fucata. There was no significant difference in total fouling cover between shell regions of P. fucata and P. chinensis after 16 weeks; however, the hinge of P. penguin was significantly more fouled than the lip. The most common fouling species (the hydroid Obelia bidentata, the bryozoan Parasmittina parsevalii, the bivalve Saccostrea glomerata and the ascidian Didemnum sp.) showed species-specific fouling patterns with differential fouling between shell regions for each species. The role of the periostracum in determining the community development of fouling species was investigated by measuring the presence and structure of the periostracum at the lip and hinge of the three pearl oyster species. The periostracum was mainly present at the lip of the pearl oysters, while the periostracum at the hinge was absent and the underlying prismatic layer eroded. The periostracum of P. fucata lacked regular features, whereas the periostracum of P. penguin and P. chinensis consisted of a regular strand-like structure with mean amplitudes of 0.84 microm and 0.65 microm, respectively. Although the nature and distribution of fouling species on the pearl oysters was related to the presence of the periostracum, the periostracum does not offer a fouling-resistant surface for these pearl oyster species.     

Control of biofouling on pearl oysters Pinctada imbricata using wax and Chinese herbs

Abstract

Biofouling poses severe challenges to pearl oyster Pinctada imbricata culture in China, and controlling it is both labor- and capital-intensive. The antifouling properties of wax, and wax mixed with Chinese herbs, sprayed onto pearl oyster shell surfaces during peak biofouling seasons were evaluated. Pearl oysters coated with three wax treatments (plain wax, Chinaberry seed extract, Chinese honeylocust fruit extract) and a control (no treatment), were cultured in nets for up to 60?days. Mortality rate, fouling organism and pearl-oyster weights, and shell height are reported for individual oysters on each of six sampling dates. With the exception of oysters submerged for 12?days, all oysters were significantly affected by treatment type and submersion duration. Fouling weight increased more rapidly over time in the control-treatment oysters. Wax-based coatings deterred fouling-organism settlement on oysters for at least 2?months during the intensive fouling season, reducing mortality and not adversely effecting growth.     

马氏珠母贝雌雄同体和自体受精的研究

对马氏珠母贝(Pinctada martensiiDunker)成体的性腺进行外观和切片观察,可把马氏珠母贝雌雄同体的个体分为2种类型,其中A类型可以从性腺外观特征上辨别,而B类型需性腺穿刺或组织切片来确认。对试验群体的性腺的类型进行的初步统计表明,雌雄同体个体比例A类型为4.6%,B类型为3.4%,其中雌雄生殖细胞均接近成熟的个体分别约为1.8%和2.1%。通过解剖、0.07‰的氨海水处理,对雌雄同体个体的自体授精及其早期胚胎发育进行了研究,发现自体授精的受精率低于异体授精,同时在发育过程中有较多的卵裂球解体,但仍有部分胚胎可以发育成D型幼虫。     

Spat collection studies on pearl oysters Pinctada mazatlanica and Pteria sterna (Bivalvia,Pteriidae) in Bahia de La Paz,South Baja California,Mexico

The present work deals with the temporal and bathymetrical variations of the epifaunal community associated with two species of pearl oysters (Pinctada mazatlanica and Pteria sterna) during a seed collecting season from June to November 1989. A total of 63 items (species, genera and/or families) were recorded; their variations in presence and abundance were followed during three periods (June–July, August–September and October–November). The collectors were examined for different immersion times (2, 4, 6 and 8 weeks) for each period. Community structure was compared through the Brillouin Index, the Morisita Index and the Importance Value.We define the chronology of spatfall for both species of pearl oysters and their bathymetrical distribution. Relationships between these species and the epifaunal community present into the collectors were analysed, searching for possible noxious effects on the survival of juvenile pearl oysters, and identifying index species related with their spatfall. A strategy for starting massive seed collection of both species is established, particularly for P. mazatlanica.     

马氏珠母贝3个野生种群及种群间杂交后代遗传多样性的ISSR分析

运用ISSR分子标记技术分析了马氏珠母贝(Pinctada martensii)广西北海(BW)、广东大亚湾(DW)和海南三亚(SW)野生种群及其自繁子一代(BB1、SS1、DD1)和杂交子一代(BS1、BD1、DS1)9个群体各50个个体的遗传多样性.结果表明:3个野生群体遗传多样性分别是0.2585、0.2607和0.2571;3个自繁群体子一代遗传多样性分别是0.2504、0.2545和0.2527,3个杂交子一代遗传多样性分别是0.2747、0.2659和0.2784.种群间杂交增加了子代的遗传多样性,同时增加了杂交子一代与杂交亲本间的遗传距离,而自繁群体的遗传多样性与其来源的野生种群比较,遗传多样性降低.本文指出利用野生群体进行杂交育种应该纯化亲本才能获得杂种优势,人工育苗或选择性育种需要保持足够数量的繁殖亲本以避免遗传多样性降低.     

Realized heritability and genetic gains of three generation for superior growth in the pearl oyster Pinctada martensii

The pearl oyster Pinctada martensii is an important economic shellfish species and mainly cultured in the southern provinces of China. The species is cultured for marine pearl production. However, pearl quality has recently decreased because the cultured stocks had slow growth and mass mortalities caused by inbreeding depression. We have initiated a selective breeding program to improve the cultivated stocks since 2002. In 2004, a base population was developed by collecting the breeders from Beibuwan and Liushagang stocks. During the period of 2005–2007, a two successive generation selection for shell length in the base population was carried out to produce the second generation selected and unselected lines. In May of 2008, three types of lines were produced by selecting the breeders from the second generation selected and unselected lines. The three types of lines were designated as SS (Selected for three generations), SC (selected for the two generations) and CC (unselected for three generations). Realized heritability for the third generation, cumulative (over three generation) and current (for the third generation) genetic gains were evaluated by comparing the growth performance of three types of lines at days 8, 16, 45, 75, 180 and 360. It was found that the SS lines had significant larger mean shell length and shell height than the SC and CC lines at all sampling ages (P < 0.05). The realized heritability estimate for adult shell length for the third generation was 0.41, similar with those detected for the first and second generation. The cumulative and current genetic gains for adult shell length were 20.94% and 13.27%, respectively. The present results indicate that there exists a high genetic variation in the population and mass selection is potential to improve pearl oyster stocks.     

The structure-function relationship of MSI7, a matrix protein from pearl oyster Pinctada fucata

We previously identified a matrix protein, MSI7, from pearl oyster Pinctada fucata. According to the structural analysis, the DGD site in the N-terminal of MSI7 is crucial for its role in the shell formation. In this study, we expressed a series of recombinant MSI7 proteins, including the wild-type and several mutants directed at the DGD site, using an Escherichia coli expression system to reveal the structure-function relationship of MSI7. Furthermore, in vitro crystallization, crystallization speed assay, and circular dichroism spectrometry were carried out. Results indicated that wild-type MSI7 could induce the nucleation of aragonite and inhibit the crystallization of calcite. However, none of the mutants could induce the nucleation of aragonite, but all of them could inhibit the crystallization of calcite to some extent. And all the proteins accelerated the crystallization process. Taken together, the results indicated that MSI7 could contribute to aragonite crystallization by inducing the nucleation of aragonite and inhibiting the crystallization of calcite, which agrees with our prediction about its role in the nacreous layer formation of the shell. The DGD site was critical for the induction of the nucleation of aragonite.     

Significant correlation of Cd,Cu, Pb and Zn in sediments and oysters (Saccostrea cucullata) collected from Qeshm Island,Persian Gulf,Iran

Abstract

The relationships are evaluated between the heavy metal species in sediments and the accumulation by the soft tissues of Saccostrea cucullata collected from the northern and southern coasts of Qeshm Island, Persian Gulf. The sequential extraction technique was employed to fractionate the sediment into non resistant and resistant fractions. Data from sequential extractions indicated that the metals were mainly associated with the residual fraction at the north coast and with non residual fractions at the south coast. The results showed that the best correlations were observed between heavy metals concentrations in soft tissues and the fractions in the southern sediment. Note that the bioavailability of trace metals is influenced by the chemical characteristics and properties of the sediment. Therefore, the present results generally supported the use of soft tissues of S. cucullata as a more accurate biomonitoring organism for Cu, Pb and Cd in sediments from the southern coast of Qeshm Island, Persian Gulf.     

Normal hematological indices, blood chemistry and histology and ultrastructure of pancreatic islets in the wild Indian bonnet monkeys (Macaca radiata radiata)

The present study is aimed at determining some haematological and biochemical parameters in the wild Indian bonnet monkeys as also the microscopic and ultrastructural characteristics of their pancreatic islets. Adult wild Indian bonnet monkeys (Macaca radiata radiata) of both sexes weighing between 2.5 and 4 kg were used in these experiments. Their platelet, reticulocyte and total leukocyte counts and the blood concentrations of hemoglobin and plasma proteins and the serum concentrations of aspartate amino transferase, alanine amino transferase and calcium are similar to the values reported for M. mulatta. Plasma glucose is lower when compared with reported values of M. mulatta and M. fascicularis. Insulin levels are comparable with those of M. mulatta and M. nigra. Histology of islets is similar to that of humans. Ovoid cell collections of islet cells are scattered throughout the pancreas. Ultrastructure of A, B and D cells is similar to humans. These findings suggest that this relatively underutilized macaques may be a suitable model for biomedical research.     

Identification of EGFR in pearl oyster (Pinctada fucata martensii) and correlation analysis of its expression and growth traits

Marine pearl production is directly influenced by the growth speed of Pinctada fucata martensii. However, the slow growth rate of this organism remains the main challenge in aquaculture production. Epidermal growth factor receptor (EGFR), an important receptor of tyrosine kinases in animals, plays versatile functions in development, growth and tissue regeneration. In this study, we described the characteristic and function of an EGFR gene identified from P. f. martensii (PmEGFR). PmEGFR possesses a typical EGFR structure and is expressed in all studied tissues, with the highest expression level in adductor muscle. PmEGFR expression level is significantly higher in the fast-growing group than that in the slow-growing one. Correlation analysis represents that shell height and shell weight show positive correlation with PmEGFR expression (p < 0.05), and total weight and tissue weight exhibit positive correlation with it (p < 0.01). This study indicates that PmEGFR is a valuable functional gene associated with growth traits.     

Shell selection behaviour and spatial distribution of three species of intertidal hermit crabs from Hormuz Island,Persian Gulf (Crustacea: Paguroidea)

Shell selection behaviour and spatial distribution of three hermit crab species, Diogenes avarus, D. karwarensis, and Areopaguristes perspicax, were studied at six sites along the intertidal zones of Hormuz Island in the Persian Gulf. 1025 specimens were collected occupying altogether 31 shell species (D. avarus 28 species, A. perspicax 22 species, and D. karwarensis 8 species). Diogenes avarus was found to be by far the most abundant of these three crab species, and Cerithidea cingulata the dominant shell occupied by these hermit crabs. The distribution of the hermit crabs significantly varied (p<0.05) among the sites. The number and the wide diversity of shells occupied in different sites show that the main factor in shell selection for these hermit crabs is the abundance and distribution of shell species in the field.     

The influence of cooling rate,developmental stage,and the addition of sugar on the cryopreservation of larvae of the pearl oyster Pinctada fucata martensii

This paper examines the effects of cooling rate, developmental stage, and the addition of sugar on the cryopreservation of the larvae of the pearl oyster, Pinctada fucata martensii. The survival rates of frozen-thawed trochophores was 43.1% at a cooling rate of 1.0 degrees C/min. The survival rate of frozen-thawed larvae increased with developmental stage, except for umbo stage larvae, and the late D-shaped larvae showed a survival rate as high as 91%. The addition of sugar (0.2M glucose or sucrose) improved the survival rate of larvae. These results indicate that the preferred cooling rate, developmental stage, and sugar for the cryopreservation of pearl oyster larvae are 1 degrees C/min, late D-shaped larvae and 0.2M glucose or sucrose.     

An overview of Iranian mangrove ecosystems, northern part of the Persian Gulf and Oman Sea

Iranian mangrove forests occur between longitude 25°19′ and 27°84′, in the north part of the Persian Gulf and Oman Sea. In 2002, it was estimated that 93.37 km² of Iranian shorelines were covered with mangrove forests, with the largest area (67.5 km²) occurring between the Khamir Port and the northwest side of Qeshm Island, and the smallest area (0.01 km²) in the Bardestan estuary. Only two species of mangrove are found in the Persian Gulf: Avicennia marina from Avicenniaceae and Rhizophora macrunata from Rhizophoraceae. A. marina is the dominant specie in these forests whereas Rh. macrunata is found only in the Sirik region. Overexploitation of mangrove leaves and oil pollution are the main causes of mangrove destruction in this region.     

Histology and histochemistry of the reproductive tract of the pulmonate snail,Bulinus truncatus,with observations on the effects of castration on its growth and histology

The reproductive tract of B. truncatus was investigated histologically in order to study possible effects of castration upon the accessory sex glands. In the female part of the reproductive tract—subdivided into albumen gland, oviduct, muciparous gland, oothecal gland, uterus, vagina and bursa copulatrix—13 histochemically different secretory cell types were distinguished. The majority produce different types of (acid) mucopolysaccharides. The roles of the various parts of the female tract in the production of an egg mass were elucidated by comparing the histochemistry of the egg mass to that of the female tract; the abundance and location of the cell types were also taken into account for this purpose.

The male part appeared to contain 12 histochemically different secretory cell types. These produce mainly (phospho lipoproteins together with some polysaccharides and neutral lipids.

Castration causes an acceleration of the growth of the snails. The volumes of female (albumen gland) and male (prostate gland) accessory sex glands were measured on histological sections. It appeared that growth of the albumen gland is not arrested by castration. This was not established beyond doubt for the prostate gland. The results suggest that the stimulating effects of the dorsal body hormone on the growth and synthetic capacity of the female accessory sex glands—such effects have been established for Lymnaea stagnalis—are not exerted via the ovotestis in B. truncatus.