The effects of co-cultivation of pearl mussels and fishes on water pollution control in middle or small sized water

Our field experiments showed that the cultivation of pearl mussels formed a new biocoene composed of filamentous algae, protozoa, porifera and coelenterate. It effectively reduced nitrogen, phosphorus, chemical oxygen demand and biochemical oxygen demand in the water by 67.3%, 73.2%, 38.1% and 15.5%, respectively, during May to September 1998 when the water eutrophication was developing. This could control water eutrophication and produce pearls, shellfish meat and shells. This is an economical and effective way to control water eutrophication by using the ultra strong filtering capability of freshwater pearl mussels.

Identification of a uroporphyrinogenⅢsynthetase gene and characterization of its role in pearl sac formation in Hyriopsis cumingii

UroporphyrinogenⅢsynthetase(UROS)is an important enzyme involved in the structural formation of porphyrin,which is responsible for color intensity.A UROS homolog was isolated and characterized from the pearl mussel,Hyriopsis cumingii(HcUros).The HcUros cDNA was 858 bp in length with an open reading frame that encoded a 285 amino acid protein,which contained a conserved HemD domain.HcUros exhibited widespread tissue distribution,displaying particular enrichment in the mantle and haemolymph of purple mussels,compared to white mussels.In situ hybridization of HcUros in mantle tissue demonstrated that it was specifically expressed in the dorsal epithelial cells of the mantle pallia.Additionally,HcUros expression was upregulated following implantation of the pearl sac to produce pearls.The data suggest that HcUros contributes to shell pigmentation,and nacre formation and coloring in H.cumingii.

Cloning of a microphthalmia-associated transcription factor gene and its functional analysis in nacre formation and melanin synthesis in Hyriopsis cumingii

Microphthalmia-associated transcription factor(MITF)is an essential transactivator in melanin synthesis.To characterize the role of MITF in the pearl mussel Hyriopsis cumingii,the MITF homolog of H.cumingii was isolated.The full-length HcMitf cDNA consisted of a 1332-bp with an open reading frame that encode for a 443 amino acid protein that contain a conserved basic helix-loop-helix zipper domain.The HcMitf was found to widespread tissue distribution but expression was higher in purple mussels than in white mussels,mostly in mantle,liver,kidney,gill,and foot with the exception of the adductor mussel.HcMitf and its downstream gene tyrosinase(HcTyr)were highly expressed at the nacre deposition stage after implantation of mantle tissue to produce pearls.Using RNA interference,the expression of HcMitf was reduced by 78%(P<0.01)and expression of HcTyr was also significantly suppressed and consequently total melanin content was decreased(P<0.05).The results suggest that HcMitf plays an important role in melanin synthesis,nacre formation and shell pigmentation in the H.cumingii.