Fauna and standing crop of freshwater mussels in Poyang Lake, China

Freshwater mussels are a major component of the zoobenthos and they therefore play an important role in freshwater ecosystems. The community composition and the standing crop of freshwater mussels in Poyang Lake, the largest freshwater lake in China and one of two lakes connected to the Changjiang （Yangtze） River, were investigated from February 2008 to May 2009. Mussels were sampled in hydrologically and geographically distinct sampling areas. A total of 42 species and 13 genera were identified, of which 32 species were endemic to China. Two species, Unio douglasiae and Lamprotula caveata, dominated all sampling areas. The number of genera and species, and the number of species within each genus, differed significantly among sampling areas. Freshwater mussels were very abundant, with an overall density of 0.28±0.22 ind./m-＇ and biomass of 4.08±3.96 g/m^2. Significant variation observed among sampling areas and among genera was probably due to the variety of habitats among the areas sampled and to the adaptability of different freshwater mussels to environments. This study suggests that Poyang Lake and other freshwater lakes in the region are important sites of freshwater mussel biodiversity and conservation.

Proximate composition and elemental analysis in soft tissues of freshwater mussels （Anodonta anatina） from the Chashma Lake, River Indus Pakistan

BACKGROUND： Aquatic invertebrates are playing an important role in assessment of the water contaminants and also serve as a major component of food chain. Freshwater mussels are considered to be the good bioindicator species of aquatic environment and widely used to determine the metals load. METHODS： Proximate composition and elemental analysis were carried out in edible （foot, mantle） and non-edible portion （gills） of freshwater mussels （Anodonta anatina） harvested from various site of Chashma Lake, River Indus Pakistan. RESULTS： The nutritional components were varied among the studied portion and muscular foot found to be the best part for consumption. Protein and fat contents were significantly higher in foot （15.90±0.88%, 1.19 ±0.26%） as compared to mantle （10.78±2.24%, 0.27±0.09%） and gills （6.44± 1.22%, 0.53 4-0.15%） respectively. For the macro minerals mantle had high concentration of Ca （46838±984 mg/kg）, Na （2706±343 mg/kg）, P （6921± 1063 mg/kg） and Mn （7207± 1046 mg/kg） as compared to foot. CONCLUSIONS： Heavy metals （Cd, Cu, Cr） concentration in edible portions were lower than the permissible limit by WHO whereas the concentration of Pb was slightly higher than the recommended value that might be the risk for the consumers. Being filter feeder gills accumulated the high concentration of all the metals and found to be the key portion for biomonitoring studies. Freshwater mussels of Chashma Lake Indus River are the rich source of protein and all the other micro and macro minerals therefore could be used as an excellent source of food.

Optimization of the ultrasonic-microwave assisted enzymatic hydrolysis of freshwater mussel meat

In the present study,the Ultrasonic-Microwave(US-MW)technique was applied for assisting enzymatic hydrolysis of freshwater mussel meat.The operating parameters of enzymatic hydrolysis were investigated and the properties and qualities of the freshwater mussel hydrolysates were also analyzed.The considerable optimum conditions for enzymatic hydrolysis of mussel meat were ratio of liquid to material of 10.36:1,power of 360.52 W,processing time of 6.91 min,enzymolysis time of 4 h.Under these conditions,a degree of hydrolysis(DH)of 48.40% was obtained.The hydrolysates produced under optimum conditions,were characterized in terms of electrophoretic profile,amino acid composition and infrared spectrum analysis.SDS-PAGE profiles of the hydrolysates revealed that several protein bands were cleaved and several light myosin chains(25 kDa and 15 kDa,respectively)and peptides of molecular weight lower than 6.5 kDa were identified.The infrared spectrum absorption peak of amide band A and band III shifted after US-MW pre-treatment,which indicated that the N-H(hydrogen bonding)stretching vibration and triple helix structure of samples were affected.The essential amino acids in hydrolysates with or without US-MW pre-treatment were 36.62 mg/100 g and 33.40 mg/100 g.It was proved that US-MW assisted enzymatic hydrolysis is an effective technology to utilize freshwater mussel meat.

Effect of complex hydraulic variables and physicochemical factors on freshwater mussel density in the largest floodplain lake,China

Background Habitat degradation and flow regime alterations are two of the most prominent and common impact factors to freshwater mussel populations.Knowledge of the correlation between freshwater mussel distribution,density and habitat characteristics is important for maintaining and restoring their biodiversity and ecological functions.Information on predicting habitat suitability of freshwater mussels is lacking in China.Here,we aimed to analyze the correlation between freshwater mussel density and complex hydraulic and physicochemical variables to predict habitat suitability.Results The results showed that four complex hydraulic variables(boundary Reynolds number,critical shear stress,bed roughness and mean sediment particle size)and four physicochemical variables(water temperature,chlorophylla,transparency and pH)were key factors for predicting habitat suitability of freshwater mussels.Freshwater mussel density was significantly correlated with Froude number,water temperature and chlorophyll-a.Conclusions Our results confirmed that higher freshwater mussel density would be associated with areas that are stable in complex hydraulic and physicochemical variables.These results provide an important insight into the conservation of freshwater mussel diversity and their habitat restoration in China and globally.

Occurrence and fate of chlorinated methylsiloxanes in surrounding aqueous systems of Shengli oilfield, China

Mono-chlorinated products of cyclic volatile methylsiloxanes(cVMS),i.e.,Monochlormethylheptamethylcyclotetrasiloxane[D3D(CH_(2)Cl)],monochlormethylnonamethylcyclopentasiloxane[D4D(CH_(2)Cl)],and monochlormethylundemethylcyclohexasiloxane[D5D(CH_(2)Cl)],were detected in water[<LOQ(Limit of quantitation)-86.3 ng/L,df(detection frequency)=23%-38%,n=112]and sediment samples[<LOQ-504 ng/g dw(dry weight),df=33%-38%,n=112]from 16 lakes located in Shengli oilfield of China,and had apparent increasing trends(31%-34%per annum)in sediments during Year 2014-2020.Simulated experiments showed that chloro-cVMS in sediment-water system had approximately 1.7-2.0 times slower elimination rates than parent cVMS.More specifically,compared with those of parent cVMS,volatilization(86-2558 days)and hydrolysis(135-549 days)half-lives of chlorocVMS were respectively 1.3-2.0 and 1.8-2.1 times longer.In two species of freshwater mussels(n=1050)collected from six lakes,concentrations of chloro-cVMS ranged from 9.8-998 ng/g dw in Anodonta woodiana and 8.4-970 ng/g dw in Corbicula fluminea.Compared with parent cVMS,chloro-cVMS had 1.1-1.5 times larger biota-sediment accumulation factors(2.1-3.0)and 1.1-1.7 times longer half-lives(13-42 days).Their stronger persistence in sediment and bioaccumulation in freshwatermussels suggested that environmental emission,distribution and risks of chloro-cVMS deserve further attention.

Hic74,a novel alanine and glycine rich matrix protein related to nacreous layer formation in the mollusc Hyriopsis cumingii

Organic matrix proteins play an important role in the biomineralization of mollusc shells.We have identified and characterized a novel matrix protein,namely hic74,isolated from the mantle of the freshwater mussel Hyriopsis cumingii.The hic74 gene encodes a 850 amino acid protein that is rich in alanine(ala,30.8%),glycine(gly,25.8%)and serine(ser,10.6%),with ala mainly existing in poly-ala forms within the ala/gly-rich regions.Quantitative PCR expression analysis demonstrated that hic74 was specifically amplified from the mantle and in situ hybridization showed a strong signal in the epithelial cells in the pallial region of the mantle.Lower levels of expression were detected during the early stages of pearl sac formation but increased and remained constant during nacreous layer formation suggesting that hic74 might be involved in this process.

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.