合浦珠母贝性变现象的初步研究

长期以来,有关合浦珠母贝(pinctada martensii,Dunker)的性现象说法不一,一般认为合浦珠母贝属雌雄异体种类,但也有一些雌雄同体的报道。立石等曾对日本大村湾合浦珠母贝性腺进行组织学观察,发现极少数个体具有精卵巢结构;小岛等研究了日本英虞湾的合浦珠母贝性腺,也认为似乎具有雌雄同体的现象,但他们都认为,这可能是由于海区的不同而发生的特殊现象。日本学者的研究还表明,合浦珠母贝可以进行两性交替(Alternative amphisexuality),即具有性变现象。但国内在这方面一直没有研究报导。在生产实践中合浦珠母贝的性变现象与其育苗生产直接相关,研究探讨合浦珠母贝性别转化及性别决定的规律将为其生产性人工育苗提供重要的理论指导。

合浦珍珠贝人工育苗提高产量的初步探讨

合浦珍珠贝(Pteria martensii)人工育苗在60年代中期初获成功。随着生产的发展，由小规模的育苗水体逐渐扩大到水池式的生产，育苗工艺不断改进。1977年，东兴珍珠场采用流水育苗法，对缩短育苗期和提高附苗率获得成效。最高的附苗水准达11万个／米^3，比一般的静水生产池提高一倍左右。

Effects of ocean acidification on the metabolic rates of three species of bivalve from southern coast of China

Oceanic uptake of anthropogenic carbon dioxide results in a decrease in seawater pH, a process known as "ocean acidification". The pearl oyster Pinctada fucata, the noble scallop Chlamys nobilis, and the green-lipped mussel Perna viridis are species of economic and ecological importance along the southern coast of China. We evaluated the effects of seawater acidification on clearance, respiration, and excretion rates in these three species. The animals were reared in seawater at pH 8.1 (control), 7.7, or 7.4. The clearance rate was highest at pH 7.7 for P. fucata and at pH 8.1 for C. nobilis and P. viridis. The pH had little effecton the respiration rate of P. fucata and P. viridis. In contrast, the respiration rate was significantly lower atpH 7.4 in C. nobilis. The excretion rate was significantly lower at pH 7.4 than pH 8.1 for all species. Theresults indicate that the reduction in seawater pH likely affected the metabolic process (food intake, oxygenconsumption, and ammonia excretion) of these bivalves. Different species respond differently to seawateracidification. Further studies are needed to demonstrate the exact mechanisms for this effect and evaluateadaptability of these bivalves to future acidified oceans.

Construction of cDNA subtractive library from pearl oyster (Pinctada fucata Gould) with red color shell by SSH

The molecular basis of color polymorphism in the shells of the pearl oyster Pinctada fucata is largely unknown. We developed a red-shelled family line and used suppression subtractive hybridization （SSH） to screen for differentially expressed genes in red- and non-red-shelled pearl oysters. We constructed forward and reverse cDNA subtractive libraries consisting of 2 506 and 797 clones, respectively. Among 343 randomly selected clones in the forward library, 304 sequences were identified in GenBank using BLASTx and BLASTn. Of the 304 sequences, 13 showed no similarity to known sequences and 291 were matched with known genes of the pearl oyster, including shematrin-1, shematrin-2, shematrin-6, shematrin-7, nacrein, nacrein-like protein, aspein for shell matrix protein, glycine-rich protein, mantle gene 5, 28S, EST00031, EST00036, 16S, and COl. In the reverse library, 7 clones were sequenced and analyzed by BLAST. Two sequences shared similarity with EST00036 from the P. fucata subtraction cDNA library, four with the P. fucata mitochondrial gene for 16S rRNA and 1 with P. fucata shematrin-2. We evaluated the expression of 12 genes from the forward library using RT PCR. Two sequences matched with 16S and CO1 so were considered to be false positives. The remaining 10 sequences were differentially expression in the red-shelled pearl oysters. Our results suggest that differential expression of these genes may be related to color variation in the red-shelled family line of the pearl oyster.

Effect of Temperature on Gene Expression in the Pearl Oyster Pinctada fucata

In this study, we examined the effect of elevated temperature on the expression patterns of genes, i.e., nacrein, irr, n16, n19, and hsp70 in the pearl oyster Pinctada fucata. The experiment was carried out at 4 temperatures, i.e., 20℃(ambient, control), 24, 28℃, and 32℃. The expression levels of target genes in P. fucata were assayed at 0, 6, 24, 48, and 96 h via real-time polymerase chain reaction. Results showed that the expression levels of nacrein and irr had no significant variations among different time points below 28℃, but significantly increased over time at 32℃. The expression levels of n16 and n19 did not change markedly at 20℃. The former increased significantly at 6 h and 24 h while the latter substantially decreased during 6–96 h at 24, 28 and 32℃. Among different temperatures, the level of n16 was significantly lower at 20℃ than at other temperatures during 6–96 h, and the level of n19 significantly varied among different temperatures at 48 h and 96 h. The expression level of hsp70 was significantly higher at 32℃ than at 20, 24 and 28℃ at 24 h. These results demonstrated that elevated temperature impacted the physiological processes of P. fucata and potentially influenced its adaptability to thermal stress.

A possible mechanism for the formation of annual growth lines in bivalve shells

We report a unique shell margin that differed from the usual shell structure of Pinctada fucata.We observed empty organic envelopes in the prismatic layer and the formation of the nacreous layer in the shell margin.All the characteristics of the growing margin indicated that the shell was growing rapidly.To explain this anomaly,we propose the concept of "jumping development".During jumping development,the center of growth in the bivalve shell jumps forward over a short time interval when the position of the mantle changes.Jumping development explains the unusual structure of the anomalous shell and the development of annual growth lines in typical shells.Annual growth lines are the result of a discontinuity in the shell microstructure induced by jumping development.