Temporal and spatial variability in the heavy-metal content of Dreissena polymorpha (Pallas) (Mollusca: Bivalvia) from the Kleines Haff (northeastern Germany)

The present investigation was performed on zebra mussels, Dreissena polymorpha (Pallas), which were sampled from the Kleines Haff. As a part of the Oder estuary, the Kleines Haff acts as a sink for the load of the river Oder. Mussel shells and mussel tissue were analyzed for their content of selected heavy metals, based on the composition of the suspended matter. Mussels were sampled in May, July, August and September 1996 at different locations and divided into three groups regarding their body size. The data show that concentrations of lead, cadmium and mercury vary during the year. Mussel shells and mussel tissue showed seasonal and local differences in heavy-metal concentration. Between the size classes, however, there was no significant difference, with one exception: the lead content in tissues was significantly higher in large mussels (>2.5 cm shell length) than in small ones (<1.9 cm). The concentrations of lead and cadmium clearly decreased in mussel shells from May to September, while they increased in mussel tissues. The lead concentration in the tissue corresponded to that of mercury. The highest values measured for mercury were 218 μg/kg dry weight (DW), for cadmium 1030 μg/kg DW and for lead 6182 μg/kg DW. The average concentration of heavy metals in mussel tissue was 9 to nearly 170 times lower than in the surrounding sediment and seston. It can be assumed that a balance exists between the concentration of heavy metals in the mussels' food and the mussels themselves.     

Factors influencing the attachment strength of Dreissena polymorpha (Bivalvia)

The effects of several factors (shell length, exposure time, substratum orientation in space, illumination, temperature, conspecifics) upon the attachment strength (measured with a digital dynamometer) of the freshwater, gregarious bivalve Dreissena polymorpha were studied under laboratory conditions. A rapid increase in attachment strength was observed on resocart (a thermosetting polymer based on phenol-formaldehyde resin, with paper as filler) substrata during the first 4-d exposure, after which it stabilised at ca 1 N. The attachment strength increased also with mussel size. Mussel adhesion on variously oriented surfaces (vertical, upper horizontal and lower horizontal) was similar. Illumination inhibited attachment strength, as expected for a photophobic species, but only after a 2-d exposure. After 6 d, no effects of light were detected. Thus, illumination seemed to influence the attachment rate, rather than the final strength. The optimum temperature for mussel attachment was 20- 25 degrees C. At lower and higher temperatures (5-15 degrees C and 30 degrees C), their adhesion strength decreased. The presence of conspecifics stimulated mussel attachment strength.     

Occurrence of Conchophthirus acuminatus (Protista: Ciliophora) in Dreissena polymorpha (Mollusca: Bivalvia) along the River Shannon, Ireland

Samples of Dreissena polymorpha were collected at several sites along the River Shannon navigation in Ireland, to determine the occurrence and distribution of their obligate host-specific commensalistic ciliate, Conchophthirus acuminatus, in this newly invaded region. Mussels collected by various methods were fixed immediately in 75% ethanol, in which they were later dissected under a stereoscopic microscope, beginning with thorough flushing of the mantle cavity and removal of the gills. One ml of sediment flushed from the mantle cavity and dissection residue of each mussel was examined under a compound light microscope using brightfield, phase-contrast, and differential-interference-contrast optics. Of 180 mussels examined, 125 (69.44%) harbored C. acuminatus. The ciliates were invariably well fixed and easily identifiable in all preparations. Mean sampling intensity for infected mussels was 8.47 ciliates per ml of sediment. Both prevalence and sampling intensity varied between sites, but no pattern was discernible. The present results are consistent with other reports of C. acuminatus being the most widespread and abundant symbiont of D. polymorpha throughout Europe, often occurring where no other symbionts occur. Its occurrence in Ireland indicates introduction of the mussels as adults, since planktonic veliger larvae are not known to harbor ciliates. Following similar reasoning, it is possible that the earlier North American invasion by D. polymorpha included only veligers, since C. acuminatus has not been found on that continent. Using these simple and quick methods, the ciliates could be easily identified and counted to give general comparative data among sites regarding intensity and prevalence. Thus, this method has promise for future efforts to obtain basic information rapidly in newly invaded systems.     

Particle transport in the zebra mussel, Dreissena polymorpha (Pallas)

The capture, transport, and sorting of particles by the gills and labial palps of the freshwater mussel Dreissena polymorpha were examined by endoscopy and video image analysis. More specifically, the morphology of the feeding organs in living zebra mussels was described; the mode and speeds of particle transport on the feeding organs was measured; and the sites of particle selection in the pallial cavity were identified. Particle velocities (outer demibranch lamellae, 90 microm s(-1); inner demibranch lamellae, 129 microm s(-1); marginal food groove of inner demibranchs, 156 microm s(-1); dorsal ciliated tracts, 152 microm s(-1)), as well as the movement of particles on the ctenidia and labial palps of D. polymorpha, are consistent with mucociliary, rather than hydrodynamic, transport. Particles can be sorted on the ctenidia of zebra mussels, resulting in a two-layer transport at the marginal food groove of the inner demibranch. That is: preferred particles are transported inside the marginal groove proper, whereas particles destined for rejection are carried superficially in a string of mucus. Sorting also occurs at the ventral margin of the outer demibranch; desirable particles are retained on the outer demibranch, whereas unacceptable particles are transferred to the inner demibranch and ultimately excluded from ingestion. We suggest that the structure of homorhabdic ctenidia does not preclude particle sorting, and that some ecosystem modifications attributed to zebra mussels may ultimately be due to ctenidial sorting mechanisms.     

Preliminary data on size composition and settlement ofDreissena polymorpha (Pallas) (Mollusca: Bivalvia) in lakes differing in trophic state

Size composition of colonies and settlement of larvae on nylon substrates as function of depth inDreissena polymorpha demonstrated differences in three lakes of different trophic state. In one lake, the data on size distribution in the colony and of the settled larvae also differed. The explanation requires further research.     

The effect of food availability on byssogenesis by the zebra mussel (Dreissena polymorpha Pallas)

The effect of varying algal availability on byssal thread productionby re–attaching zebra mussels (Dreissena polymorpha) wasquantified. The byssal apparatus was severed and mussels allowedto re–attach to a hard substratum for a 21 day periodduring which they were fed at algal concentrations of 0.0, 0.1,0.5, 1.0 or 2.0 mg C l^-1. Byssal thread production was quantifiedby counting the number of new attachment plaques present eachday. Results showed that starved mussels continued to partition organiccarbon towards thread production but the resultant byssal masswas compromised, containing fewer threads than those producedby fed mussels. The daily average byssal thread production bymussels fed at 2.0 mg C l^-1 was greater than that of starved musselsand the final mean dry soft tissue weight higher. At algal Cconcentrations below maintenance requirements byssal threadproduction was elevated compared to starved mussels, but therewas no concurrent increase in soft tissue. This suggests thatbelow maintenance levels assimilated carbon was solely partitionedtowards byssus production and stored reserves may have beenutilized. The ratio of organic carbon contained in the byssusto that in the soft tissues remained relatively constant acrossall feeding levels. This suggests that the carbon content ofthe byssus is a constant function of that of the soft tissuemass. These results may explain seasonal variation in attachmentstrength of numerous byssate species and seasonal vertical migrationsby D. polymorpha. Present Address-Queen Mary & Westfield College, Dept of Biology,University of London, Mile End Road, London E1 4NS, UK (Received 16 March 1998; accepted 30 September 1998)     

Comparative toxicity of chlorine and peracetic acid in the biofouling control of Mytilopsis leucophaeata and Dreissena polymorpha embryos (Mollusca,Bivalvia)

Chlorination is the most common antifouling procedure, but the search for alternatives is ongoing. Although concentrations that kill adults will also be effective against larvae, it is advisable to evaluate the toxicity of any candidate toxicant against the combatable life stage. For mussels, the earliest life stages are the most vulnerable ones and thus may require the lowest doses biocides. Since the period of larval presence is restricted to a couple of months, a pointed dosage of biocides during this period will be as effective as a continuous dosage throughout the year. This study reports on the lethal acute toxicity of sodium hypochlorite and peracetic acid to 4 h old embryos of Mytilopsis leucophaeata and Dreissena polymorpha. Chlorination was found effective against M. leucophaeata from a concentration of 0.6 mg/l onwards, even at short exposure times. Commercial peracetic acid showed to be a very good alternative in both species although the most appropriate level still has to be determined.     

Food quality controls reproduction of the zebra mussel (Dreissena polymorpha)

Species such as Dreissena polymorpha sometimes contribute substantially in the transfer of primary to secondary production. During the ontogenetic cycle, the reproductive investment of adult mussels is one of the main parameters that affect recruitment success. We studied how food quality and temperature affect the reproductive investment in term of egg mass of D. polymorpha in a lake by sampling mussels monthly from 4 m and 15 m depths. Temperature affected reproduction directly and also indirectly through the food. To assess whether temperature and/or food conditions led to the differences observed in mussels sampled from the two depths, mussels were reared in the laboratory under two different temperature regimes for 3 months, simulating the temperature of the lake at 4 m and 15 m depth. Possible effects of food quality were tested at each temperature using four diets differing in fatty acid composition. Temperature played an important role as a trigger for spawning, and the type of diet clearly affected the reproductive investment. When the heterokont chromophyte alga Nannochloropsis limnetica, which is rich in polyunsaturated fatty acids (PUFAs) and long-chained PUFAs (>C18), was fed to mussels, an increased egg mass was obtained. This result was in contrast to that found when the green alga Scenedesmus obliquus and the cyanobacterium Aphanothece sp., both of which are deficient in long-chained PUFAs, were offered as food to the mussels. Such a PUFA-dependent food quality may affect reproduction in lakes. Food quality effects vary seasonally in a lake and may be most important in summer, when low-food-quality green algae and cyanobacteria are abundant. The low biochemical quality of these blooms may affect at least the later period of gametogenesis of D. polymorpha, which reproduces from June to August.     

Invasion of the Zebra Mussel Dreissena polymorpha (Pallas, 1771) (Dreissenidae) in Lake Ladoga

Biology Bulletin - In May 2019, the invasive mollusk Dreissena polymorpha (Pallas, 1771) was found in Volkhov Bay of Lake Ladoga by means of an unmanned underwater vehicle. The age of some mollusks...     

Bioprocessing of polluted suspended matter from the water column by the zebra mussel (Dreissena polymorpha Pallas)

Measurements of pseudofaeces production of Dreissena polymorpha were carried out with the aim of developing a biological filter at the freshwater inlet of Lake Volkerak-Zoommeer, the Netherlands. Bioprocessing of polluted suspended matter by suspended cultures of D. polymorpha occurs by filtration and sedimentation of the suspended matter as pseudofaeces. The measurements were conducted under semi-natural conditions.Pseudofaeces production was mainly determined by the dry matter content of the water; the relation is linear. Temperature was of much less importance. This agrees with earlier investigations of the filtration rate of D. polymorpha. Even at the lowest temperature measured during the experiments (6.4 °C) no large decrease in activity was observed. The relation of pseudofaeces production with shell length was sigmoid in shape, in accordance with measurements of the filtration rate.The pseudofaeces produced was slightly more polluted than suspended matter, partly due to a finer grainsize. D. polymorpha from Lake IJsselmeer exposed for 217 days at the intended location of the filter showed bioaccumulation of toxicants, especially organic pollutants and Polycyclic Aromatic Hydrocarbons (up to 10-fold accumulation). The required number of D. polymorpha in the biological filter to treat the waterflow of 14 m³ s^–1 entering Lake Volkerak-Zoommeer is 1.24 * 10⁹. The purification efficiency of the filter, the reduction of the amount of toxicants, partly depends on the binding properties of the toxicants and is highest for those strongly bound to suspended matter.     

Sexual selection and simultaneous hermaphroditism among the Unionidae (Bivalvia: Mollusca)

Simultaneous hermaphroditism is an infrequent mode of reproduction among bivalves of the family Unionidae: only five of the 220 North American species are simultaneous hermaphrodites. However, hermaphroditic individuals of otherwise predominantly dioecious species have been encountered in 30 of I01 species examined. These hermaphroditic individuals as well as simultaneous hermaphrodites can exhibit considerable variability in the ratio of spermatogenic: oogenic tissue within the gonad, and the purposes of this paper are to determine the underlying causes of both this variability and the occurrence of occasional hermaphroditic individuals among dioecious species. Results indicate that the ratio of male: female gonodal tissue of a simultaneous hermaphrodite is bimodally distributed, and several hypotheses to account for this observation are presented. It is proposed that populations occurring in different habitats and under conditions of different individual density are subject to fundamentally different sexual selection pressures acting on ratios of allocation to male and female gametes. Occasional hermaphroditism among otherwise predominantly dioecious species was in this study associated with infection of the gonads by digenean trematodes. A model of sexual determination among unionids presented in this paper proposes that sex is determined by genetically controlled hormone levels: occasional hermaphrodites result from alterations in these hormone levels caused by developmental errors and trematodal infections which mimic the results of such errors. Predictions of this model are consistent with observed levels of variability in male: females gonadal tissue among occasional hermaphrodites.     

Cytogenetic characterization of the Zebra Mussel Dreissena polymorpha (Pallas) from Miedwie Lake, Poland

Cytogenetic characterization of D. polymorpha was carried out using banding techniques such as C-banding, fluorochrome CMA3 and silver nitrate treatment. The diploid chromosome number of both investigated D. polymorpha forms (typical and albinotic) was the same 2n = 32 (NF = 56). The karyotype consisted of 5 pairs of metacentric, 7 pairs of submetacentric and four pairs of subtelo-acrocentric chromosomes. Ag-NORs were located in the telomeric position on the largest subtelo-acrocentric chromosome pair. C banding patterns indicate many sites of constitutive heterochromatin mainly located in the telomeric regions and interstitially in some chromosomes. CMA3-sites were observed in almost all chromosomes; apart from the Ag-NORs sites, they were located terminally on the chromosome arms and interstitially on three chromosome pairs. Sixteen chromosomes could be counted at the diakinesis stage of meiosis. No differences in banding chromosome patterns were found neither between both analyzed forms of D. polymorpha nor between males and females.     

Bioaccumulation and Partitioning of Cadmium within the Freshwater Mussel Dreissena polymorpha Pallas

Kinetics of uptake, partitioning and elimination of cadmium were investigated in experimental studies with the freshwater mussel, Dreissena polymorpha. The radioactive cadmium isotopes ¹⁰⁹Cd and ¹¹⁵Cd were used as tracers. Shells, soft parts and body fluid of the mussel exhibited considerable differences in accumulation and elimination. Accumulation factors up to more than 70,000 were calculated for the periostracum, whereas accumulation factors for the whole mussels ranging up to 3,000 were calculated. The shells bound a great deal of cadmium, but only loosely, and the metal could be readily eliminated after transfer to uncontaminated water. In contrast, no significant amounts of the cadmium incorporated in the soft parts were eliminated. The results indicate that the major portion of cadmium in the soft parts is strongly bound and cannot be eliminated by exchange processes.     

Tissue Hemoglobins in Bivalvia (Mollusca)

Distribution and properties of tissue hemoglobins in bivalves are reviewed. The mollusk gills are given particular attention; data on their functions, relative weight, and surface area as well as the content, properties, and functional importance of gill hemoglobin are reviewed.     

Haplosporidium raabei n. sp. (Haplosporidia): a parasite of zebra mussels, Dreissena polymorpha (Pallas, 1771)

Extensive connective tissue lysis is a common outcome of haplosporidian infection. Although such infections in marine invertebrates are well documented, they are relatively rarely observed in freshwater invertebrates. Herein, we report a field study using a comprehensive series of methodologies (histology, dissection, electron microscopy, gene sequence analysis, and molecular phylogenetics) to investigate the morphology, taxonomy, systematics, geographical distribution, pathogenicity, and seasonal and annual prevalence of a haplosporidian observed in zebra mussels, Dreissena polymorpha. Based on its genetic sequence, morphology, and host, we describe Haplosporidium raabei n. sp. from D. polymorpha - the first haplosporidian species from a freshwater bivalve. Haplosporidium raabei is rare as we observed it in histological sections in only 0·7% of the zebra mussels collected from 43 water bodies across 11 European countries and in none that were collected from 10 water bodies in the United States. In contrast to its low prevalences, disease intensities were quite high with 79·5% of infections advanced to sporogenesis.     

Origin of Spanish invasion by the zebra mussel, Dreissena polymorpha (Pallas, 1771) revealed by amplified fragment length polymorphism (AFLP) fingerprinting

The zebra mussel, Dreissena polymorpha is an aquatic nuisance invasive species originally native to the Ponto-Caspian region where it is found in lakes and delta areas of large rivers draining into the Black and Caspian seas. The dispersal of D. polymorpha began at the end of the 18th century, at a time when shipping trade become increasingly important and many canals were built for linking different navigable river systems in Europe. Over the past 200 years, zebra mussels spread to most of the lakes, rivers and waterways in Europe by a combination of natural and anthropogenic dispersal mechanisms. D. polymorpha invaded Spain around 2001, being found for the first time in the Riba-roja reservoir at the lower part of the Ebro River, North-East Spain. The relatively late invasion of Spain was most likely caused by the presence of the Pyrenees, which isolated the Iberian Peninsula from the rest of the European continent, and acted as a barrier to the dispersal of D. polymorpha. In recent studies, molecular genetic methods have successfully been used to determine phylo-geographic relationships, which may reflect invasion corridors and can help retrace source populations. Zebra mussels from populations in Great Britain, The Netherlands, Belgium, France, Germany, Spain, Italy, Romania and North America were analyzed using PCR based amplified fragment length polymorphism (AFLP)-fingerprinting to determine the source population of D. polymorpha in Spain. The phylogenetic analyses and pair-wise genetic distances revealed that the recent invasion of zebra mussels in Spain is most likely from France.     

Field and laboratory studies of Ophryoglena sp. (Ciliata: Ophryoglenidae) infection in zebra mussels,Dreissena polymorpha (Bivalvia: Dreissenidae)

This study, conducted in the Dnieper-Bug Canal in Belarus, is the first to monitor the seasonal (June-November) dynamics of infection with the parasitic ciliate Ophryoglena sp. in a zebra mussel (Dreissena polymorpha) population. Mean population prevalence and intensity of infection varied, respectively, from 11 to 62% and from 0.9 to 24.1 ciliates/mussel. Mean prevalence was highly correlated with mussel length in mussels <20 mm (R(2)=0.97) and was lower in larger mussels. Mean infection intensity in mussels 1-25 mm long was similarly correlated with their size (R=0.98), reached a maximum in the 20-25 mm size-class, and then sharply decreased, thus providing evidence, albeit limited, that high intensity of infection might be lethal. Transinfection of zebra mussels by Ophryoglena sp. was achieved in the laboratory-a first for a protozoan parasite of D. polymorpha; from an initial complete lack of infection, mean prevalence and intensity rose, respectively, to 86.7% and 8.3 ciliates/mussel.     

The annual reproductive cycle of the freshwater mussel Dreissena polymorpha Pallas in lakes

Summary The annual development of the gonads of Dreissena polymorpha was studied at three sampling sites in two lakes over 3 and 1 1/2 years, respectively. A resting stage occurred after the last spawning in summer/autumn. Oogenesis (accompanied by multiplying segmentation of the oogonia and early growth processes of its oocytes) restarted in specimens at least 1 year old at low temperatures (below 10° C) during winter and early spring. At one location (Fühlinger See) the onset of the spawning season was correlated with an increase of water temperatures above 12° C. At 2 m depth, two main spawning periods in May and August were normally recognized, the first at temperatures of 12–16° C, the second at 16–21° C. It was clearly demonstrated for the first time in Dreissena polymorpha that the oocytes became mature in successive cohorts within one gonad. A female mussel may spawn several times during the reproductive season. At 9 m depth, the onset of spawning also started at about 12° C; this occurred in late summer, with two spawning periods within 1 month at a temperature range of 12–16° C. At another location (Heider Bergsee) the size of the gonads and the oocytes was reduced during April of both years studied, when food supply was low simultaneously with rapidly rising water temperatures in this shallow lake. There was no spawning period during spring. The major spawning period was delayed until July (temperatures 19–22°C). This shows (1) the synchronizing influence of low winter temperatures on the annual reproductive cycle and (2) a temperature threshold of at least 12° C for the start of the spawning processes. The results are discussed with regard to the geographical limits of further spread of Dreissena polymorpha.     

New Zealand Recent Hyriidae (Mollusca: Bivalvia: Unionida)

The New Zealand freshwater mussels are taxonomically revised and compared with key Australian and South American taxa using DNA sequence data. Three living species are recognised: Echyridella menziesii, Echyridella aucklandica and Echyridella onekaka. Cucumerunio websteri websteri and Cucumerunio websteri delli, are treated as junior synonyms of Unio aucklandica, which is transferred from Cucumerunio (and Hyridella) to Echyridella. Lectotypes are designated for Unio waikarensis and Unio hochstetteri, which are illustrated together with primary type specimens of other relevant taxa. The type locality of U. aucklandica is restricted to the catchment of the Kawakawa River.     

The fitration rate of Dreissena polymorpha (Bivalvia) in three Dutch lakes with reference to biological water quality management

SUMMARY. 1. The filtration rate of Dreissena polymorpha Pallas measured in the field in three shallow Dutch lakes shows an inverse exponential relationship with the dry matter content of the water.
2. Temperature seems to set only a gross level to the filtration rate in summer and winter season respectively; within a season no clear relation between the filtration rate and temperature exists.
3. Under laboratory conditions the risk of measuring abnormal behaviour of Dreissena polymorpha is shown to be substantial; hence field-measurements of the filtration rate are preferable.
4. The clearing capacity of the Dreissena polymorpha populations in Lakes IJsselmeer and Markermeer is sufficient to filter both lakes at least once or twice a month. This indicates the potential importance of this species for restoration of turbid, eutrophic lakes by means of biomanipulation.