脉红螺幼虫变态诱导机制及变态过程的调控机理

Metamorphosis is an important developmental stage in shellfish, which has a crucial influence on dynamics, distribution and recruitment of natural populations as well as seed breeding. Rapana venosa, a carnivorous gastropod, is one of the most important commercial shellfish in China. However, information about the mechanism of its metamorphosis regulation was extremely limited. Based on the results of our previous research that juvenile oyster can significantly induce R. venosa larvae to metamorphosis, we plan to design a series of experiments aiming to sift and identify the key active substance in juvenile oyster inducing the metamorphosis of R. venosa, examine the key neurotransmitters content level, mRNA expression level and mRNA spatial expression of neurotransmitter receptors as well as analyze activities and mRNA expression level of digestive enzymes. In our study, we investigated the regulatory function of R. venosa neuroendocrine and digestive system in terms of molecular and genetic basis, providing new insights into the regulation mechanism of R. venosa metamorphosis process. The results are crucial for better understanding the metamorphosis mechanisms and population dynamics of carnivorous snails as well as providing theoretical supports for seed breeding, resource recovery, stock enhancement and aquaculture of R. venosa.

变态过程是贝类从幼虫向成贝转变的重要发育阶段，对苗种繁育以及自然海区中贝类种群数量变动、分布和资源补充有重要影响。脉红螺是我国重要的经济贝类，属于肉食性螺类，目前国内外对其变态过程研究很少，尚不清楚其变态机理。本项目在前期首次发现刚变态牡蛎稚贝能够高效诱导脉红螺幼虫变态的基础上，进一步筛查与确定牡蛎稚贝体内诱导脉红螺幼虫变态的关键活性物质，查明其诱导机制；通过研究关键神经递质含量及其受体基因表达量变化与时空分布特征、消化酶活性及其编码基因表达量变化，从分子水平探讨神经内分泌系统和消化系统对脉红螺幼虫变态的调控作用，阐明脉红螺幼虫变态过程的调控机理。研究成果可为脉红螺苗种繁育、增养殖和资源恢复技术研发提供理论依据，对于揭示其在自然海区中种群数量变动和分布规律及资源补充机制具有重要科学意义。

变态过程是贝类从幼虫向成贝转变的重要发育阶段，对苗种繁育以及自然海区中贝类种群数量变动、分布和资源补充有重要影响。脉红螺是我国重要的经济贝类，属于肉食性螺类，目前国内外对其变态过程研究很少，尚不清楚其变态机理。饵料是诱导贝类幼虫变态的重要外部因子。本研究发现，具有变态能力的4螺层脉红螺幼虫（壳高1200-1500μm）摄食了刚变态的牡蛎稚贝（壳长320-350μm左右），牡蛎稚贝体内的特殊物质诱导了脉红螺幼虫变态，这些特殊物质可能包括牡蛎多糖、牡蛎糖蛋白等物质。在神经内分泌系统和消化系统对脉红螺变态调控作用方面，本研究利用RNA-seq、iTRAQ、GC-MS、Real time PCR等技术对脉红螺幼虫变态过程分子机理展开研究，从转录组水平、蛋白质组水平和代谢组水平揭示了幼虫变态过程调控特征。其中与神经系统相关的基因，如5-羟色胺受体、神经元乙酰胆碱受体和一氧化氮合成酶（NOS）在脉红螺变态后发生了下调，而GABA受体结合蛋白发生了显著上调。另外获得了神经内分泌系统关键基因5-HT receptor和NOS的cDNA序列，揭示了其在脉红螺变态过程中表达特点及调控机理。本研究也鉴定到了vdg3等与消化系统相关的关键差异基因，在脉红螺浮游幼虫中随着发育时间的推移，其表达量稳步上升，在变态后急剧升高；此外，肉食性消化酶胰蛋白酶和羧肽酶B在变态中发生上调，而植食性的消化酶类如纤维素酶、内切葡聚糖酶等在变态过程中显著下调。本研究初步阐明了脉红螺变态的分子机理，相关研究成果可为脉红螺苗种繁育、增养殖和资源恢复技术研发提供理论依据，对于揭示其在自然海区中种群数量变动和分布规律及资源补充机制具有重要科学意义。