The infaunal polychaete Perinereis aibuhitensis Grube,distributed widely along Asian coasts and estuaries,is considered a useful animal model in ecotoxicological tests and a promising candidate in biomonitoring programs.This paper deals with the activities of antioxidant enzymes including superoxide dismutase(SOD),catalase(CAT),and glutathione peroxidases(GSH-Px) in infaunal polychaete P.aibuhitensis exposed to a series of sublethal water-bound cadmium(Cd) concentrations(0,0.34,1.72,3.44,6.89,and 17.22 mg L-1) under a short-term exposure(1-8 d).The results indicate that the SOD and GSH-Px activities in P.aibuhitensis are stimulated first and then renewed to the original level.The CAT activity of worms decreases at an earlier exposure time but increases to the control values at a later exposure time.Our study suggests that Cd can interfere with the antioxidant defense system of P.aibuhitensis.However,the changes in antioxidant enzyme activities for this species do not show the best promise as biomarkers in Cd biomonitoring of estuarine and coastal zones because weak or non-dose-effect relationships between the antioxidant enzymes activities and Cd levels are found.
Polychaetes provide an excellent food resource for fi sh and represent the dominant zoobenthos in marine ecosystems. Diel variation in the rates of metabolism and ammonia-N excretion of Marphysa sanguinea were studied. The worms were grouped according to their wet body weight into small（S; 1.24±0.06 g）, medium（M; 4.00±0.30 g）, and large（L; 8.54±1.08 g） categories. Their weight-specifi c metabolic rates, based on aerobic respiration（ R）, were measured at 16℃（±0.2℃） and classed as either routine（ RR） or standard（ RS） rates. Both respiration types decreased with increasing body weight. Respiration was described by R = a W^b, where b was-0.400 9 and-0.532 0 for RR and RS, respectively. Diurnal changes in RS for each group was relatively flat, with a slightly increasing trend with time, but was relatively stable as a whole. RR of the diurnal variation of worms was higher than RS, but both had similar overall trends. The peak values of specifi c dynamic action（SDA）（ RSDA） in the S, M, and L groups were 2.704, 1.149, and 0.682 mg/（g·h）, respectively. The durations of SDA were 13, 6, and 6 h, respectively and the energy expenditures of SDA were 377.98, 117.34, and 74.94 J/g, respectively. These data indicate that the metabolic rates were higher in smaller individuals, which is advantageous for their rapid growth.
Shewanella marisflavi strain AP629 was certified as a novel pathogen of the sea cucumber Apostichopusjaponicus. In this study, four monoclonal antibodies （MAbs） （3C1, 3D9, 2F2, 2A8） against strain AP629 were developed by immunizing Balb/C mice. 3C1 and 3D9 recognized S. marisflavi only, showing no cross reactivity to other gram-negative bacteria, However, 2F2 and 2A8 showed cross reactivity to all tested bacteria. Indirect immunofluorescence, and immunogold electron microscopy, showed the binding antigens of 3C1 and 3D9 were located at the secretion on the surface of strain AP629. The binding antigens of 2F2 and 2A8 were noted on the membrane of the cells. MAbs 3C1 and 3D9 recognized the lipopolysaccharide fraction of strain AP629, and 2F2 and 2A8 recognized in western-blotting protein antigens with molecular weights of 113 and 128 kDa respectively. MAbs 3C1 and 3D9 have the potential for use in pathogen diagnosis, epidemiology and studies on the mechanism of how S. marisflavi infects A. japonicus. Imrnunohistochemistry with 3C1 or 3D9 identified strain AP629 in the body wall of infected A. japonicus. In the adult sea cucumbers that were infected via body wall injection, positive signals were observed at the site of skin ulceration, and at the connective tissue of the non-ulcerated body wall. In addition, some large blue-stained cells aggregated at the connective tissue colonized by large numbers of bacteria. In juveniles infected via immersion infection, positive signals were observed at the cuticle of the body wall only. Our results suggest that 3C1 and 3D9 could be used in various immunological assays to study the invasion mechanism of strain AP629 in A. japonicus, the law of bacterial colonization, proliferation in different tissues of A. japonicus, and correlation between secretion on the surface of strain AP629 and its pathogenesis to A. japonicus.
