Pen Shell Atrina Pectinata Research Articles

Molecular characterization of Vasa homolog in the pen shell Atrina pectinata: cDNA cloning and expression analysis during gonadal development.

Vasa is an ATP-dependent RNA helicase of the DEAD (Asp-Glu-Ala-Asp) box family and a representative component of the germ plasm. In this study, we cloned the full-length vasa homolog in the bivalve Atrina pectinata (psvasa), and performed phylogenetic analysis, mRNA expression analysis for tissue-specific distributions, and immunostaining analysis to reveal its histological localization. The sequence of psvasa was 3587bp in length and contained a 5' untranslated region of 150bp, an open reading frame of 2214bp, and a 3' untranslated region of 1223bp. The deduced amino acid sequence of psvasa was 737 amino acids long and contained evolutionarily conserved sequences reported in other animals. The mRNA expression analysis showed the highest expression levels in the gonads. Expression was especially high in the ovaries, followed by the testes. The immunostaining analysis showed Vasa-positive cells in the developing gonads, suggesting the presence of putative germ stem cells contributing to the supply of germ cells. Furthermore, characteristic Vasa signals were observed in the basophilic nuclei of the oocytes, suggesting that psvasa plays an important role in the progression of meiosis in oocytes.

Evolution of nacre- and prisms-related shell matrix proteins in the pen shell, Atrina pectinata

The molluscan shell is a good model for understanding the mechanisms underlying biomineralization. It is composed of calcium carbonate crystals and many types of organic molecules, such as the matrix proteins, polysaccharides, and lipids. The pen shell Atrina pectinata (Pterioida, Pinnidae) has two shell microstructures: an outer prismatic layer and an inner nacreous layer. Similar microstructures are well known in pearl oysters (Pteriidae), such as Pinctada fucata, and many kinds of shell matrix proteins (SMPs) have been identified from their shells. However, the members of SMPs that consist of the nacreous and prismatic layers of Pinnidae bivalves remain unclear. In this study, we identified 114 SMPs in the nacreous and prismatic layers of A. pectinata, of which only seven were found in both microstructures. 54 of them were found to bind calcium carbonate. Comparative analysis of nine molluscan shell proteomes showed that 69 of 114 SMPs of A. pectinata were found to have sequential similarity with at least one or more SMPs of other molluscan species. For instance, nacrein, tyrosinase, Pif/BMSP-like, chitinase (CN), chitin-binding proteins, CD109, and Kunitz-type serine proteinase inhibitors are widely shared among bivalves and gastropods. Our results provide new insights for understanding the complex evolution of SMPs related to nacreous and prismatic layer formation in the pteriomorph bivalves.

Artificial fertilisation method for the production of pen shell Atrina pectinata juveniles in hatcheries

In juvenile production of pen shell Atrina pectinata, broodstocks are usually induced to spawn by a combination of a slight increase in water temperature and addition of conspecific sperm to rearing water, but the stimulus is not always effective in eliciting a positive response from ripe adults. To solve the problem of unstable spawning induction, we developed an artificial fertilisation method suitable for the hatchery production of pen shell juveniles. The method was based on our recent finding that all-trans retinoic acid (at-RA) strongly induced the maturation of pen shell oocytes. Experiments were conducted to assess the following: 1) suitable at-RA concentration for oocyte treatment, 2) necessity of at-RA treatment of sperm, 3) optimum egg to sperm ratio, 4) allowable time lag between the at-RA treatment of oocytes and insemination, and 5) possible changes in the performance of the method during the spawning season. In addition, we confirmed the effectiveness of the method by observing the early growth of hatched larvae and the actual production of pen shell juveniles in two separate hatcheries. The recommended conditions were clarified as follows: 1) 1.0 or 0.1 μM at-RA was suitable to prepare mature oocytes, 2) at-RA treatment of sperm was not necessary, 3) optimum egg to sperm ratio was 1:1000, 4) mature oocytes were competent for insemination until 2 h after the at-RA treatment, and 5) fertilisation and hatching rates changed in accordance with alterations in the maturity of broodstocks. In the actual production of juveniles, benthic juveniles of pen shells were successfully obtained at two different hatcheries, although the number of produced juveniles was still small. Increasing familiarity with this new method through repetitive practice, together with the improvement of rearing techniques, would improve the performance of the method. The artificial fertilisation method presented in this article offers a novel alternative for stable production of juvenile pen shells.

A novel peptide identified from visceral ganglia induces oocyte maturation, spermatozoa active motility, and spawning in the pen shell Atrinapectinata

The identification of novel peptides that regulate reproduction is essential for studying reproductive physiology in bivalves. Therefore, we aimed to identify peptides that affect the reproductive physiology of bivalves. We identified an oocyte maturation-, sperm motility-, and spawning-inducing peptide from the visceral ganglia of the pen shell, Atrina pectinata. The peptide consisted of 26 amino acid residues (GFDSINFPGTIDGFKDYSSNKKERLL). This peptide induced oocyte maturation and sperm motility activation at less than 1 nM upon the treatment of gonad fragments and induced spawning at 1 nmol when injected into mature individuals. Mature eggs and sperms artificially spawned by peptide administration were fertilized, and we confirmed that the development proceeded normally to veliger (D-shape) larvae. These results indicated that GFDSINFPGTIDGFKDYSSNKKERLL stimulated the gonads of pen shells and induced oocyte maturation, sperm motility activation, and spawning.

Phylogeography and Taxonomic Revision of the Pen Shell Atrina pectinata Species Complex in the South China Sea

Phylogeographic studies contribute to addressing questions regarding the geographic patterns and evolutionary scenarios within and among species and also shed light on the taxonomic status of widely distributed species complexes. The pen shell Atrina pectinata species complex is a widely distributed and economically important bivalve in the northwestern Pacific. Previous phylogeographic studies have identified four genetically distinct cryptic species within the A. pectinata species complex along the coast of China, of which three cryptic species were distributed in the South China Sea. However, less attention has been given to their identification and delimitation. Herein, we report the phylogeography and taxonomic revision of the A. pectinata species complex in the South China Sea using DNA sequence data from mitochondrial cytochrome oxidase I (COI) and 16S ribosomal RNA (16S rRNA), and nuclear 28S ribosomal RNA (28S rRNA) gene markers. Using a combination of phylogenetic and DNA-based species delimitation analysis methods, we found strong support for four genetically valid species in the A. pectinata species complex and defined them as A. japonica, A. lischkeana, Atrina sp., and A. pectinata based on our results as well as on previous morphological and genetic studies. A demographic historical analysis showed that all three species in the South China Sea had populations that were relatively stable over time and then subjected to sudden expansion during the late Pleistocene (60,000–90,000 years ago). These results provide new insights into the systematics and evolution of the A. pectinata species complex and have important conservation and management implications.

Population genetic structure of the pen shell Atrina pectinata sensu lato (Bivalvia: Pinnidae) throughout East Asia

The pen shell (Atrina pectinata sensu lato) is a commercially important but endangered mollusk in East Asia, requiring special attention for resource management. Whereas the presence of several cryptic species is considered to occur along the coast of China, the genetic structure around Japan is not well understood. We collected 664 individuals from twelve sites in Japan and from one site in South Korea, sequenced their mitochondrial cytochrome c oxidase subunit I (mtCOI) gene, and conducted phylogeographic analyses together with 540 mtCOI sequences previously reported for China and the Korean Peninsula. As a result, A. pectinata s. l. was found to be comprised of six monophyletic lineages (lineages 1–6) which were identical to those of previous studies. Lineages 1 and 2 have a broad range of geographical distribution from the eastern coast of the Asian continent to Japan. Hierarchical AMOVA revealed a significant genetic differentiation among groups of sampling sites both in lineages 1 and 2, inferring the effects of post-recruitment selection or coastal topography. Some of the sampling sites around Japan had two or three lineages, and careful attention is needed for the resource management in these sites because lineage identification by external morphology is impossible in some cases.

Population Dynamics of the Comb Pen Shell Atrina pectinata (Linnaeus, 1767) (Mollusca, Bivalvia: Pinnidae) Collected by Diving from Shallow Areas of the Southwest Visayan Sea, Northeastern Panay Island, Philippines

With the objective of determining the population dynamics of the comb pen shell (Atrina pectinata) (Mollusca, Bivalvia: Pinnidae) collected by divers in the southwest Visayan Sea, length-frequency data recorded between June 2018 and May 2019 were analyzed using the FiSAT software. von Bertalanffy growth parameters for the species were SL = 40.69 cm and K = 0.78 yr–1 the range of values for other fast-growing tropical bivalves. The estimated mean growth rate of 0.15 ± 0.05 cm d–1 likewise supports a fast growth rate and a short lifespan (< 1 yr) of the population. The recruitment pattern shows one major and minor pulse that coincides with the northeast monsoon and just prior to the southwest monsoon, respectively. Using ELEFAN II, total mortality (Z) of 2.79 yr–1 was estimated. From an averaged M/K value from the related bivalve literature (1.51) multiplied by the species’ own K, natural mortality (M) of 1.18 yr–1was estimated, which when subtracted from the Z, gave fishing mortality (F) of 1.61 yr-1 and an exploitation rate E of 0.58, considered overexploited. Recommended management measures for more sustainable utilization of the species include non-collection of individuals smaller than the cited minimum size at sexual maturity [20 cm shell length (SL)], and a ban on the collection at least during the major spawning season deemed to be, based on the growth rate between October and December each year. Marketing of the non-adductor portion of the viscera, normally just discarded, is also recommended to increase the income of the fishers.

Cytoprotective Effect of a Neutrase Enzymatic Hydrolysate Derived from Korea Pen Shell Atrina pectinata Against Hydrogen Peroxide -Induced Oxidative Damages in Hepatocytes

Cytoprotective Effect of a Neutrase Enzymatic Hydrolysate Derived from Korea Pen Shell Atrina pectinata Against Hydrogen Peroxide -Induced Oxidative Damages in Hepatocytes

Evolution of Biomineralization Genes in the Prismatic Layer of the Pen Shell Atrina pectinata.

Molluscan shells are composed of calcium carbonates, with small amounts of extracellular matrices secreted from mantle epithelial cells. Many types of shell matrix proteins (SMPs) have been identified from molluscan shells or mantle cells. The pen shell Atrina pectinata (Pinnidae) has two different shell microstructures, the nacreous and prismatic layers. Nacreous and prismatic layer-specific matrix proteins have been reported in Pteriidae bivalves, but remain unclear in Pinnidae. We performed transcriptome analysis using the mantle cells of A. pectinata to screen the candidate transcripts involved in its prismatic layer formation. We found Asprich and nine highly conserved prismatic layer-specific SMPs encoding transcript in P. fucata, P. margaritifera, and P. maxima (Tyrosinase, Chitinase, EGF-like proteins, Fibronectin, valine-rich proteins, and prismatic uncharacterized shell protein 2 [PUSP2]) using molecular phylogenetic analysis or multiple alignment. We confirmed these genes were expressed in the epithelial cells of the mantle edge (outer surface of the outer fold) and the mantle pallium. Phylogenetic character mapping of these SMPs was used to infer a possible evolutionary scenario of them in Pteriomorphia. EGF-like proteins, Fibronectin, and valine-rich proteins encoding genes each evolved in the linage leading to four Pteriomorphia (Mytilidae, Pinnidae, Ostreidae, and Pteriidae), PUSP2 evolved in the linage leading to three Pteriomorphia families (Pinnidae, Ostreidae, and Pteriidae), and chitinase was independently evolved as SMPs in Mytilidae and in other Pteriomorphia (Pinnidae, Ostreidae, and Pteriidae). Our results provide a new dataset for A. pectinata SMP annotation, and a basis for understanding the evolution of prismatic layer formation in bivalves.

Abnormal Karyotype of Pen Shell (Atrina pectinata) During Its Early Embryonic Development in Late Breeding Season

The pen shell, Atrina pectinata, distributes globally. It is one of the most important edible bivalves in east Asian countries. However, there are multiple difficulties in rearing pen shell larvae and juveniles because of their high mortality. To understand the mechanism underlining such high mortality at the early embryonic development stage, we obtained approximately 100 million larvae during later breeding season in June, 2017, and checked a large amount of mitotic chromosomal plates of the early embryos and post-spawning gonads tissue slices of their parents. The results showed that most diploid A. pectinata embryos have 17 pairs of chromosomes (2n = 34) as their parents do. The first pair of particularly large chromosomes are heterotypic in some diploid embryos while they are homomorphic in others. The primary sex-determination chromosome type is XX/XY. A lot of triploid, pentaploid and aneuploid embryos with different numbers of the largest homomorphic or heteromorphic chromosomes were found due to the degeneration of overmatured parent gonads which hold normal karyotype. These larvae will die even though most of them may develop into the trochophore stage with 34 chromosomes. Genetic deficiency of chromosomes will cause a high rate of mortality in early embryos in late breeding season. These findings should enrich the current knowledge of juvenile pen shell aquaculture.

Fatty acid ester metabolites of gymnodimine in shellfish collected from China and in mussels (Mytilus galloprovincialis) exposed to Karenia selliformis

Marine shellfish exposed to the microalgae Karenia selliformis can accumulate gymnodimines (GYM). Shellfish samples collected from Beihai City in Guangxi Autonomous Region, and Ningde City in Fujian Province, in the South China Sea, as well as mussels Mytilus galloprovincialis fed on K. selliformis under laboratory conditions were analyzed. Gymnodimines and various fatty acid ester metabolites were detected in the clam Antigona lamellaris and pen shell Atrina pectinata, while no esters were found in the oyster Crassostrea sp. and the gastropod Batillaria zonalis despite positive detection of free GYM in both species. When present, the predominant acyl esters observed were 18:0-GYM-A and 20:1-GYM-A. Under laboratory conditions GYM-A was accumulated and metabolized to fatty acid esters in mussels exposed to K. selliformis, with 16:0-GYM-A and 20:1-GYM-A as the major variants. A novel compound with the same accurate mass as GYM-A and its 16:0 fatty acid ester were observed in the experimental mussels but was not present in the microalgal strain to which mussels were exposed. No significant differences of reactive oxygen species (ROS) levels and antioxidant enzymes were found between mussels fed on K. selliformis or GYM-free microalgae Isochrysis galbana. This suggests the accumulation of GYM and its metabolites does not significantly impact the physiological status of mussels. While it is currently not proven that GYM affects human health, risk assessments should consider the presence of GYM esters in naturally contaminated shellfish as part of exposure analysis.

Some Aspect on the Biology of Pen Shell Atrina Pectinata (Linneaus, 1767) In Coastal Waters of Maqueda Bay, Philippines

A Total of 379 pen shells Atrinapectinata were collected from February 2017 to January 2018 in the coastal waters of Maqueda Bay. Measurement and analysis of length and weight were done using FiSAT software. Population parameters were assessed to evaluate the stock status which includes the asymptotic length (L∞) and growth coefficient (K) to be 34.65 cm, 0.77 year−1 respectively. Specimens of A. pectinata reached a mean length of 20.98 cm. Length-weight relationship resulted to “negative allometric” 0.0462L2.6533 R2 = 0.7823; signifying pen shells growth was faster in length than on weight. The recruitment pattern was continuous over the year with one major peak during rainy season (July). In addition, the highest catch based on collected sampling date catch was during summer, which suggest as the peak season of the species in the area. Furthermore, the average catch annually of hookah diver was 17.69208. Higher condition index was recorded from April to May, September and January, indicating the high quality of pen shell meat and is recommended as the best period to harvest pen shell whereas June to August and October to December can be concluded as the spawning period of the pen shell and the ideal period to institute close season. Further analysis revealed that the pen shell was nearly facing overexploitation with the exploitation rate (E = 0.46) mainly due to lack of a minimum limit size and also due to an increase in the harvesting effort. The estimated total mortality (Z), natural mortality (M) and fishing mortality (F); 1.36 year−1, 1.01year−1 and 0.62 year−1, respectively. Using the mentioned (Z), (M), (F) and (E), the total population resulted to 84725.7 suggesting that half of the population has been exploited due to overfishing

Effect of superheated steam roasting with hot smoking treatment on improving physicochemical properties of the adductor muscle of pen shell (Atrina pectinate).

The adductor muscle of the pen shell Atrina pectinata (AMPS) is a popular protein‐enriched food item in Asian Pacific countries, and has only been marketed in the frozen condition, as a result browning and decreased sensory attributes occur. To overcome these problems, superheated steam roasting (at 270°C for 4 min) combined with the hot smoke (10 min) using a selective Oak sawdust was employed to develop a new AMPS product yielding high physicochemical properties during storage periods (0–13 days) especially at 10°C. The processed AMPS showed high sensory preferences because of good odor, color, and textural properties. It also significantly inhibited bacterial growth, volatile basic nitrogen, thiobarbituric acid‐reactive species, and pH changes, and eventually possessed higher nutritional composition with low trimethylamine N‐oxide level. Results indicate that saturated steam allows AMPS at good physicochemical conditions, whereas hot smoke‐derived aroma compounds prolong its shelf life through antioxidant and antimicrobial activities.

Oocyte maturation and active motility of spermatozoa are triggered by retinoic acid in pen shell Atrina pectinata

For recovery of the declining population of pen shells in the wild, the production of pen shell juveniles for transplantation or aquaculture is underway in Japan. For more stable juvenile production, artificial fertilization methods for pen shells are needed, but methods to induce oocyte maturation (meiosis resumption) used in other bivalves, which make oocytes fertilizable, were ineffective for pen shells. Here, we report evidence showing that retinoic acid (RA) has strong activity in inducing oocyte maturation and activating sperm motility in pen shells. Treatment of fully developed oocytes with 1.0 μM all-trans-RA (at-RA) induced germinal vesicle breakdown, a typical morphological sign of oocyte maturation, but 1.0 μM at-retinol and at-retinal, 2 mM ammonia, and 1.0 μM serotonin were ineffective. Treatment with at-RA for 30 min was sufficient for oocyte maturation and was more potent than its isomers, 9-cis- and 13-cis-RA. Parallel results were obtained for sperm motility activation. Oocyte responsiveness to at-RA increased during the final stage of ovary development. Artificial fertilization was successful only with the oocytes treated with at-RA, and fertilized eggs developed to D-shaped (veliger) larvae without apparent morphological abnormalities. These results indicate the possible application of RA for the artificial fertilization of pen shells.

Survival time of juvenile pen shell Atrina pectinata (Bivalvia: Pinnidae) in hyposaline water

Survival time of juvenile pen shell Atrina pectinata (shell length ≈ 34 mm) exposed to hyposaline water without sediments was investigated in laboratory experiments. The bivalves were individually maintained in rearing cups in which salinity was decreased either gradually (over 1–11 h to 12 salinities ranging from 0 to ca. 34 ppt) or rapidly (directly to 21 salinities) at 12 and 24 °C. When the environmental salinity was gradually decreased, survival time differed markedly between the bivalves exposed to: salinities ≤ 18.6 ppt (survival time < 20 h in general) vs. ≥ 21.1 ppt (> 83 h) at 24 °C; and between salinities ≤ 15.1 ppt (< 34 h) vs. ≥ 17.2 ppt (> 83 h) at 12 °C. When the environmental salinity was rapidly decreased, survival time, again, differed markedly between the bivalves exposed to: salinities ≤ 15.9 ppt (< 20 h in general) vs. ≥ 17.7 ppt (> 140 h) at 24 °C; and salinities ≤ 21.3 ppt (< 38 h in general) vs. ≥ 22.3 ppt (> 140 h) at 12 °C. Such sharp decreases in survival time due to reduced salinity led to the selected, statistical models that assume either a sharp exponential increase or stepwise hike in hazard (instantaneous mortality rate) according to salinity reduction. These data and models indicate that juvenile A. pectinata should not be kept at salinities < 21 ppt for periods > 1 day in environments without sediments.

De novo assembly of pen shell (Atrina pectinata) transcriptome and screening of its genic microsatellites

The pen shell (Atrina pectinata) is a large wedge-shaped bivalve, which belongs to family Pinnidae. Due to its large and nutritious adductor muscle, it is the popular seafood with high commercial value in Asia-Pacific countries. However, limiting genomic and transcriptomic data have hampered its genetic investigations. In this study, the transcriptome of A. pectinata was deeply sequenced using Illumina pair-end sequencing technology. After assembling, a total of 127263 unigenes were obtained. Functional annotation indicated that the highest percentage of unigenes (18.60%) was annotated on GO database, followed by 18.44% on PFAM database and 17.04% on NR database. There were 270 biological pathways matched with those in KEGG database. Furthermore, a total of 23452 potential simple sequence repeats (SSRs) were identified, of them the most abundant type was mono-nucleotide repeats (12902, 55.01%), which was followed by di-nucleotide (8132, 34.68%), tri-nucleotide (2010, 8.57%), tetra-nucleotide (401, 1.71%), and penta-nucleotide (7, 0.03%) repeats. Sixty SSRs were selected for validating and developing genic SSR markers, of them 23 showed polymorphism in a cultured population with the average observed and expected heterozygosities of 0.412 and 0.579, respectively. In this study, we established the first comprehensive transcript dataset of A. pectinata genes. Our results demonstrated that RNA-Seq is a fast and cost-effective method for genic SSR development in non-model species.

Seasonal changes of reproductive activity and biochemical composition of pen shell Atrina pectinata Linnaeus, 1767 in Bohai Sea, China

Seasonal variations in the biochemical composition and the reproductive cycle of pen shell Atrina pectinata in Bohai Sea were investigated from May 2013 to April 2014. Histological analysis indicated that the reproductive cycle of A. pectinata can be divided into two phases, inactive stage and gametogenesis, which were equally and significantly influenced by seawater temperature and food availability. Gametogenesis began in late autumn (October), and completed in June and July. Spawning took place in August, coinciding with the highest water temperature and the richest phytoplankton. The significantly high glycogen content in adductor muscles sustained throughout the late active and ripeness stages, but plummeted during spawning and inactive stages. The protein content in female gonads exhibited a synchronous increase along with oocyte diameter and lipid content, suggesting that the female gonads could accumulate protein and lipid for vitelline in A. pectinata. Furthermore, the RNA/DNA ratio was found to be a useful index to indicate the level of gonad maturation in both males and females. The findings of the present study provided a foundation for the fishery resource administration and the aquaculture development of this species.

Characterization, expression, and functional analysis of testis-specific serine/threonine kinase 1 (Tssk1) in the pen shell Atrina pectinata

Testis-specific serine/threonine kinase 1 (Tssk1) was named since its function was determined in mouse spermiogenesis. In our research, we cloned a homolog of the pen shell Atrina pectinata Tssk1, ApTssk1, and determined its expression characteristics at mRNA. The full length of ApTssk1 cDNA was 1517 bp, with an open reading frame of 1089 bp (58–1146), which encodes a peptide including 362 amino acids. The homologous analysis indicated that the deduced amino acid sequences of ApTssk1 shared a close identity with other reported Tssk1. In addition, the highly conserved fragment containing a serine/threonine protein kinase catalytic (S-TKc) domain was predicted to exist in ApTssk1. Results from the RT-qPCR display that ApTssk1 was only transcribed in the male gonad of A. pectinata, and was highest in the mature testis. Therefore, this study indicated that ApTssk1 might play a functional role during spermatogenesis in A. pectinata.

First report on the occurrence of the comb pen shell, Atrina pectinata (Linnaeus, 1767) (Bivalvia: Pinnidae) in Ulleungdo Island in the East Sea: Ecology and molecular identification of the species using COI gene sequence

Pen shell is one of the largest marine bivalves inhabiting shallow subtidal soft bottoms in the west Pacific and Indian Oceans. In Korea, the comb pen shell Atrina pectinata fisheries has been established on the south and west coasts. Recently, a pen shell population has been discovered from a subtidal sand flat (25–30 m depth) in Ulleungdo Island located in the East Sea of Korea, suggesting a potential shellfish resource in this area. In the present study, we first surveyed the population density and size of the unique pen shell using SCUBA, and identified the pen shell to species level using mitochondrial cytochrome oxidase I gene (COI) sequence. An underwater survey carried out from July to September 2013 revealed that populations of pen shell patched on subtidal sand flat at a depth of 20–25 m. Grain size analysis indicated that sand particles accounted for 99% of the 600 × 700 m sand flat. The underwater survey also indicated that density of the pen shell ranged between 6–19 ind/m2, with a mean of 11 ind/m2. Shell height (i.e. longest axis of the shell) of the pen shell on the sand flat varied between 17.2 cm to 28.8 cm, with a mean of 25.1 cm, and the age was estimated to range between 1.5–7.5 yrs, with a mean of 5 yr. COI DNA sequence obtained from the pen shell in this study showed 98.9–99.2% similarity to Atrina pectinata (Linnaeus 1767) reported from Japan. In the cluster analysis, the COI DNA sequence of the pen shells from Ulleungdo Island was grouped with A. pectinata reported from Japan and China, indicating that the pen shell discovered in this study was A. pectinata, commonly distributed on the west and south coasts of Korea.

Gonad Development of the Pen ShellAtrina pectinataFrom Shandong Province, China

The processes of gametogenesis, development, and degeneration, together with the gonad fatty acids, of the pen shell Atrina pectinata were studied. The results showed that water temperature is the key factor affecting gonadal development. The gonad started to develop and differentiate at 6–7°C, with fast development of both the visceral mass and the gonad when the temperature increased to 11–12°C. The gonad index peaked at approximately 21°C, which suggested that 6–7°C is the threshold for gonad development and that 21°C is the optimum temperature at which broodstock will mature. The gonad fatty acid 18:1n-9 correlated remarkably with the condition and gonad indices, which might be indicative of the maturity of the gonad of A. pectinata. From the perspective of nutritional composition, Pavlova sp. and Chroococcus sp. were thought to be the most appropriate feed for A. pectinata broodstock cultivation.