Size dependent bioaccumulation of heavy metals by Mytilopsis sallei (Recluz) at Visakhapatnam harbour

Relationship between body size and bioaccumulation of copper, zinc, lead and cadmium in the fouling bivalve, M. sallei (Recluz) in Visakhapatnam harbour was studied. While concentration of copper, zinc and lead decrease with increasing size, no such relationship is observed for cadmium.     

Salinity tolerance in different life history stages of an invasive false mussel Mytilopsis sallei Recluz, 1849: implications for its restricted distribution

ABSTRACT

Although the false mussel Mytilopsis sallei Recluz, 1849 is recognised as an aggressive invasive species, its populations in several estuaries in Thailand are restricted to small areas. A salinity gradient is a major characteristic of its habitat, hence the effect of various salinity levels (0–40?ppt) on the mortality of larvae, juveniles and adults of M. sallei was investigated. Condition Indices of adults reared at different salinity levels for two months were measured. Spatial and temporal variations of salinity and false mussel abundance in a canal with a salinity gradient were also monitored. After an acute (48?h) test, survival of larvae was highest at salinity levels of 12.5 and 16.25?ppt and decreased at lower and higher levels. Juveniles survived at all salinity levels, but most adults died in the first 24?h at a salinity of 40?ppt, while condition indices were lowest at salinity levels of 30 and 35?ppt. In the field survey, highest false mussel abundance was consistently found at the middle part of the canal with mid-range salinity. The results suggested that salinity is a determinant of survival in M. sallei larvae and potentially regulates the dispersal success of false mussels. However, the importance of salinity was marginal in the later stages of its life history.     

Effect of the invasive bivalve Mytilopsis sallei on the macrofaunal fouling community and the environment of Yundang Lagoon,Xiamen, China

Mytilopsis sallei is a small marine bivalve and is considered as a serious pest. We assume that the invasive bivalve M. sallei changed the community structure of fouling macrofauna and reduced the species diversity index in Yundang Lagoon, Xiamen, China. In order to verify the above hypothesis, test panels were submerged seasonally at five stations during four seasons in Yundang Lagoon, and some chemical parameters were determined. The results showed there were significant differences in density and biomass of M. sallei and other fouling macrofauna with season and with station. The species diversity of the macrofaunal fouling community at stations B and F was low in summer, because high density of M. sallei was found at two stations. There were significantly positive correlations between density and biomass of M. sallei and water temperature and COD, and significantly negative correlations with pH. The results confirmed that this invasive species changed the density and biomass compositions of fouling macrofauna, reduced the species diversity index during the summer period, and somewhat worsened the aquatic environmental quality in Yundang Lagoon, because the pH and the DO were the lowest, and the BOD and the COD were the second lowest in summer among four seasons.     

Life-history characteristics and sexual strategy of Mytilopsis sallei (Bivalvia: Dreissenacea), introduced into Hong Kong

First recorded from Hong Kong in 1980, Mytilopsis sallei now dominates the intertidal pier community within the Government Dockyard, Victoria Harbour. Analysis of monthly samples of M. sallei has demonstrated aspects of the reproductive strategy and life-history characteristics correlated with seasonal changes in local water quality.
Mytilopsis sallei is dioecious, has a high fecundity, matures early (at 8–10 mm shell length), grows fast and the majority of the population is probably semelparous. These are characteristic traits of opportunistic r -strategists. Comparable characteristics are typical of other introduced bivalves. Maximum life span of M. sallei in the Dockyard is probably less than 20 months with, however, most of the population dying before that. Heavy recruitment, particularly during spring-summer, suffocates older individuals. The shells of dead animals similarly last for little more than one year, dissolution and crushing effecting this. A mat of byssal threads serves to bind the mass and anchor it to the substratum.
Mytilopsis sallei exhibits two periods of reproductive activity and settlement per year. These are possibly two elements of a single recruitment divided into minor (autumn-winter) and major (spring-summer) components by either high summer temperatures or low salinities. Summer and winter recruits of M. sallei , respectively, mature to produce the summer and winter juveniles of the following year. Over-stepping generations plus survival of a few individuals into their second year thus ensure continued success of M. sallei , and account for its spread and dominance in its introduced range. Such a bimodal pattern appears typical of many Hong Kong intertidal, estuarine and freshwater bivalves.     

Effect of salinity on hatching, survival and infectivity of Anguillicola crassus (Nematoda: Dracunculoidea) larvae

The effect of salinity on hatching, larval survival and infectivity of Anguillicola crassus was studied under experimental conditions using eggs obtained from naturally infected eels. Egg hatching rate, second-stage larval survival and larval infectivity were maximal in fresh water and declined with increase in salinity. Larvae survived up to 100 d in fresh water, 70 d in 50 % sea water and 40 d in 100% sea water. Infectivity experiments demonstrated that salinity influenced transmission success throughout the life cycle by decreasing total infectivity of the larval population in utero within female A. crassus and when larvae were free-living in the aquatic environment. Infectivity was age-dependent in relation to salinity. Larvae were infective to intermediate and paratenic hosts for up to 80 d in fresh water, 21 d in 50% sea water and up to 8 d in 100% sea water. The data confirm field observations that infection levels decrease with an increase in salinity. The study contributes to experimental verification of the colonization abilities of A. crassus and supports the hypothesis that A. crassus can be disseminated and transmitted in brackish water. The importance of regular monitoring and stringent hygiene practices in the transportation of eels is emphasized.     

Effect of previous feeding conditions on survival in Daphnia pulicaria (Crustacea: Cladocera)

Survival of natural Daphnia populations without previous acclimatization in filtered water under laboratory conditions (starvation) was used as a parameter describing the actual competitive ability of populations in periods of food limitation. Two populations (1 and 2) of Daphnia pulicaria Forbes coming from two enclosures with a low (< 1 mgC l^–1) and a high (about 3 mgC l^–1) seston level were examined in their resistance to starvation. Juveniles of both populations survived better than adult females in the conditions without seston as well as in the control experiment, despite their much lower biomass. Animals from population 1 had lower mortality than those from population 2 in all variants of the experiment. The results confirm the hypothesis that the ability of daphnids to starve depends also on adaptation to previous feeding conditions.     

Melanin pigments of fungi under extreme environmental conditions (Review)

This review is dedicated to the research on the functions of melanin pigments in fungi. The participation of melanin pigments in protection from environmental factors is considered. Data on the biosynthetic pathways and types of melanin pigments in fungi are presented.     

盐度对不同日龄日本无针乌贼幼体生长及存活的影响

对不同日龄(1日龄、7日龄、15日龄)的日本无针乌贼在不同盐度(10、15、20、25、30、35、40)条件下的生长及存活状况进行了研究。结果表明,各日龄组日本无针乌贼的存活率及增重率均随盐度的升高而升高,但当盐度超过一定值后,其存活率及增重率随盐度的升高而降低。日本无针乌贼的适宜盐度范围为20～30,不同日龄乌贼幼体的适宜盐度范围略有不同,其中15日龄幼体对盐度的耐受性要优于1日龄及7日龄乌贼幼体。乌贼幼体的最适盐度约为25,其生长和存活均较高。     

Staphylococcus aureus requires cardiolipin for survival under conditions of high salinity

Background  

The ability of staphylococci to grow in a wide range of salt concentrations is well documented. In this study, we aimed to clarify the role of cardiolipin (CL) in the adaptation of Staphylococcus aureus to high salinity.     

Effects of salinity on growth and survival of African sharptooth catfish (clarias gariepinus) larvae

Growth and survival of replicate batches of African sharptooth catfish (Clarias gariepinus) larvae were monitored in 0, 2.5, 5.0, 7.5 and 10 ppt salinity. No significant differences in mortality or growth rate were evident between 0 and 5 ppt salinity. At 7.5 ppt mortality rate was higher and larval growth rate declined in comparison to the lower salinities. At 10 ppt all larvae died within 48 hours. The condition factor of the larvae similar between 0–2.5 ppt and displayed a declining trend between 2.5–7.5 ppt. Osmoconcentratkm of blood plasma of C. gariepinus in fresh water was 280 ± 20 mOsm/kg which is equivalent to 9.5 ppt salinity. It was concluded that 0–2.5 ppt is the optimal sclinity range for larval rearing and that short-term exposure to higher salinities (2.5–7.5 ppt) could be effective in the treatment of ectoparasitic diseases.     

Light and electron microscopy of the leucocytes of Crassostrea virginica (Mollusca: Pelecypoda)

Summary The fine structure of oyster leucocytes resembles to a great extent, that of typical eucaryotic cells. Organelles which have been described for the first time in this report are light granules, dense granules, protocentriole and X structure. Light microscopy reveals two morphological types of oyster leucocytes: agranular and granular. Based upon nuclear morphology and cytoplasmic compositions revealed in electron microscopy, at least three types of agranular and one type of granular cells are recognized.In the Giemsa-stained preparations, granular leucocytes exhibit three distinct types of cytoplasmic granules: refractile, dark blue, and pink, which presumably correspond to light granules Type A, B, and C seen in the electron micrographs. A granular leucocyte may contain one or more types of granules. Cytochemical investigations show that oyster leucocytes contain at least three hydrolytic enzymes: non-specific esterases, acid, and alkaline phosphatase. The latter two enzymes constitute 63% of the enzyme activity detected. These intracellular enzymes may be associated with the light granules and/or lysosome-like bodies.It is also demonstrated that the granular leucocyte population is significantly higher (P<0.001) in the oysters experimentally infected with Bacillus mycoides (72.19±4.71%) as contrasted with that of the controls (37.18±4.48%).Leucocytes in progressive stages of degeneration are also described.Contribution No. 71 from Marine Research Laboratory, University of Connecticut.The initial phase of this investigation was carried out at the Department of Zoology, Rutgers, The State University, New Brunswick, New Jersey, and supported by Public Health Service Research Grant AI-00781 from the National Institute of Allergy and Infectious Diseases of the National Institute of Health, awarded to Dr. L. A. Stauber. Supported by a grant from the University of Connecticut Research Foundation and Faculty Summer Fellowship to S. Y. Feng.     

Effects of salinity on food intake, growth, and survival of pufferfish (Fugu obscurus)

The food intake, growth, food conversion ratio and survival of yearling pufferfish, Fugu obscurus Abe, were investigated under different water salinity conditions over a 54‐day period. Within the salinity regimes of 0 (freshwater), 8, 18, and 35‰, the food intake levels were 0.97%, 1.43%, 1.19% and 1.01%, respectively; food conversion ratios were 1.31, 1.93, 1.61 and 1.36, respectively; and specific growth rates were 0.41%, 1.15%, 0.84%, and 0.35%, respectively. The three data series were reduced with increasing salinity. However, the survival rates did not show the same tendencies, which were 80%, 100%, 100%, and 67%, respectively. There were significant differences among the treatments. In conclusion, the yearling pufferfish optimum culture salinity condition was about 8‰.     

Anatomical studies on Margaritifera margaritifera and Cumberlandia monodonta (Mollusca: Pelecypoda: Margaritiferidae)

The family Margaritiferidae has received little serious anatomical study since the early twentieth centurv. The present paper attempts to provide information, derived from relaxed preserved and living material, on aspects of the mantle anatomy and neuroanatomy of two species, Margaritifera margaritifera and Cumberlandia monodonta . An historical overview of the systematics of the family is provided along with a proposed division of major groups within the genus Margaritifera .
The diaphragm of margaritiferids is complete, rather than incomplete as previously interpreted, and is formed bv both the gills and the diaphragmatic septa, the latter of which, in life, cover a portion of the posterior outer gill demibranchs and separate the branchial and suprabranchial chambers. Union of the diaphragmatic septa posteriorly draws the mantle margins together, separating the inhalent and exhalent apertures and thus completing the diaphragm.
The general visceral nervous system of each species is consistent with that of other bivalves. Differences from other unionaceans include the possession of a small, as opposed to a large, dorsal supra-anal bifurcation. Also, each of the two species studied lacks the anterior loop of the branchial nerve reported in some other unionaceans.     

Effects of salinity and temperature on long-term survival of the eel pathogen Vibrio vulnificus biotype 2 (serovar E)

Vibrio vulnificus biotype 2 (serovar E) is a primary eel pathogen. In this study, we performed long-term survival experiments to investigate whether the aquatic ecosystem can be a reservoir for this bacterium. We have used microcosms containing water of different salinities (ranging from 0.3 to 3.8%) maintained at three temperatures (12, 25, and 30 degrees C). Temperature and salinity significantly affected long-term survival: (i) the optimal salinity for survival was 1.5%; (ii) lower salinities reduced survival, although they were nonlethal; and (ii) the optimal temperature for survival was dependent on the salinity (25 degrees C for microcosms at 0.3 and 0.5% and 12 degrees C for microcosms at 1.5 to 3.8%). In the absence of salts, culturability dropped to zero in a few days, without evidence of cellular lysis. Under optimal conditions of salinity and temperature, the bacterium was able to survive in the free-living form for at least 3 years. The presence of a capsule on the bacterial cell seemed to confer an advantage, since the long-term survival rate of opaque variants was significantly higher than that of translucent ones. Long-term-starved cells maintained their infectivity for eels (as determined by both intraperitoneal and immersion challenges) and mice. Examination under the microscope showed that (i) the capsule was maintained, (ii) the cell size decreased, (iii) the rod shape changed to coccuslike along the time of starvation, and (iv) membrane vesicles and extracellular material were occasionally produced. In conclusion, V. vulnificus biotype 2 follows a survival strategy similar to that of biotype 1 of this species in response to starvation conditions in water. Moreover, the aquatic ecosystem is one of its reservoirs.     

Effect of conditions and protectants on the survival of Penicillium bilaiae during storage

Penicillium bilaiae is a fungal microorganism used to promote soil-bound phosphorous uptake in several crop species such as wheat, canola, and pulse crops. In this study, an air-dried granular starch-based form of the inoculant was studied for improved longevity. Experiments were performed to determine optimal water activity, packaging atmosphere, and the effects of several protective chemicals. Viable spore fractions were measured at 1, 3, and 6 months. Longevity of the microorganism was found to suffer at intermediate values of water activity and with the addition of glycerol. However, skim milk powder, sucrose, MSG, and proprietary PBX3000 were found to improve survival, with a maximum survival fraction of 15% at 6 months using the best formulation. Cell concentration was not found to influence shelf-life. High viability loss during storage in a nitrogen environment resulted in less than 1% survival.