Identification and characterization of gonadotropin-releasing hormone (GnRH) in Zhikong scallop Chlamys farreri during gonadal development.

Gonadotropin-releasing hormone (GnRH) controls synthesis of sex steroid hormones through hypothalamic-pituitary-gonadal (HPG) axis in vertebrates. But in mollusks, research on neuroendocrine control of gonadal function, such as the function of GnRH during gonadal development is limited. In this study, we investigated the morphology and structure of the nerve ganglia of Zhikong scallop Chlamys farreri by physiological and histological observations. We also cloned the ORF and studied the expression patterns of GnRH in the scallop. Tissue expression analysis showed that GnRH was highly expressed in parietovisceral ganglion (PVG). The in situ hybridization result further confirmed that GnRH mRNA only distributed in some good-sized neurons in the posterior lobe (PL) and some pint-sized neurons in the lateral lobe (LL). In addition, by examining the expression of GnRH during gonadal development in ganglia, we found GnRH displayed higher expression in the female scallops, and showed significant high expression at the growing stage of female scallops in PVG. This study would contribute to gaining insight into the mechanism underlying reproduction regulation by GnRH in the scallop and help to provide a better understanding of reproductive neuroendocrine in mollusks.

Outer fold is sole effective tissue among three mantle folds with regard to oyster shell colour.

Molluscs constitute the second largest phylum of animals in the world, and shell colour is one of their most important phenotypic characteristics. In this study, we found among three folds on the mantle edge of oyster, only the outer fold had the same colour as the shell. Transcriptome and mantle cutting experiment indicated that the outer fold may be mainly reflected in chitin framework formation and biomineralisation. There were obvious differences in SEM structure and protein composition between the black and white shell periostraca. The black shell periostraca had more proteins related to melanin biosynthesis and chitin binding. Additionally, we identified an uncharacterized protein gene (named as CgCBP) ultra-highly expressed only in the black outer fold and confirmed its function of chitin-binding and CaCO3 precipitation promoting. RNAi also indicated that CgCBP knockdown could change the structure of shell periostracum and reduce shell pigmentation. All these results suggest that the mantle outer fold plays multiple key roles in shell periostraca bioprocessing, and shell periostracum structure affected by chitin-binding protein is functionally correlated with shell pigmentation. The investigation of oyster shell periostracum structure and shell colour will provide a better understanding in pigmentation during biological mineralisation in molluscs.

A review on factors that affect surface charge accumulation and charge-induced surface flashover.

The surface charge accumulation is very likely to trigger the surface flashover, which limits the large-scale application of DC GIL/GIS. This article comprehensively reviews the effect of six factors, including insulator-electrode shape, surface roughness of the insulator and conductor, metal particles, temperature, humidity, and gas type, on the insulator surface charging property. Furthermore, three models i.e. 'analogous ineffective region' expansion model, charge cluster triggered surface flashover model, and synergistic model of adsorbed gas, revealing the mechanism of charge triggered surface flashover phenomenon are reviewed and discussed. Future work from the perspective of theoretical analysis and engineering application are suggested in this field.