Coccomyxa sp. (Chlorophyta: Chlorococcales), a new pathogen in mussels (Mytilus galloprovincialis) of Vigo estuary (Galicia, NW Spain)

In this work, we describe the occurrence of irregular shaped green aggregations in the mantle, gill filaments, adductor muscle, visceral mass and haemolymph of wild mussels (Mytilus galloprovincialis) collected from the Vigo estuary (Galicia, NW Spain). Microscopic examination of these masses revealed that they consist of intracellular green algae which are spherical to oval in shape, 5 μm in length and 3 μm in width, without flagella and with a smooth surface. The algal cells present a small single nucleus, a mitochondrion, 1-2 parietal chloroplasts and lack pyrenoids. Reproduction is by formation of 2-4 autospores or daughter cells. Pigment analysis reveals the presence of photopigments typical of green algae in addition to alloxanthin, diadinoxanthin and diatoxanthin. These carotenoids are noted for the first time in a parasitic chlorophyte. The signs of infection, together with the morphological observations, suggest that this parasitic algae may be Coccomyxa parasitica. However, further molecular studies are required for confirmation. This is the first report of Coccomyxa algae parasitizing the species M. galloprovincialis.     

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.     

Incidence of hemocytes and parasites in coastal populations of blue mussels (Mytilus edulis)--testing correlations with area,season, and distance to industrial plants

Blue mussel hemocytes (cells with immunoresponse activities) are suggested as indicators of anthropogenic contamination. We compared hemocyte numbers, granulocytoma (aggregated hemocytes), and parasites among populations of mussels from different areas of Skagerrak (a north and a south), seasons (summer and autumn), and impact levels (close or far from industrial activities). Seasonal hemocyte numbers were larger in the north compared to the south. Northern unimpacted populations had higher hemocyte numbers than populations close to industries, while no differences were found in the south. More uneven tissue distributions were found in populations far from industries in the north area and in populations close to industries in the south area. Parasites were more common in northern mussels than in southern, but no relationship to impact level was found. Mussels with granulocytoma, however, were found in all populations from the impacted sites while in none of the other populations suggesting granulocytoma as a possible indicator of industrial impact.     

Development of a qualitative PCR method for the Alexandrium spp. (Dinophyceae) detection in contaminated mussels (Mytilus galloprovincialis)

Paralytic shellfish poisoning (PSP) is a syndrome caused by the consumption of shellfish contaminated with neurotoxins produced by organisms of the marine dinoflagellate genus Alexandrium. A. minutum is the most widespread species responsible for PSP in the Western Mediterranean basin. The standard monitoring of shellfish farms for the presence of harmful algae and related toxins usually requires the microscopic examination of phytoplankton populations, bioassays and toxin determination by HPLC. These procedures are time-consuming and require remarkable experience, thus limiting the number of specimens that can be analyzed by a single laboratory unit. Molecular biology techniques may be helpful in the detection of target microorganisms in field samples. In this study, we developed a qualitative PCR assay for the rapid detection of all potentially toxic species belonging to the Alexandrium genus and specifically A. minutum, in contaminated mussels. Alexandrium genus-specific primers were designed to target the 5.8S rDNA region, while an A. minutum species-specific primer was designed to bind in the ITS1 region. The assay was validated using several fixed seawater samples from the Mediterranean basin, which were analyzed using PCR along with standard microscopy procedures. The assay provided a rapid method for monitoring the presence of Alexandrium spp. in mussel tissues, as well as in seawater samples. The results showed that PCR is a valid, rapid alternative procedure for the detection of target phytoplankton species either in seawater or directly in mussels, where microalgae can accumulate.     

Ecophysiological aspects of cardiac activity in the subtropical mussel Perna viridis (L.) (Bivalvia: Mytilidae)

Cardiac activity in the subtropical mytilid mussel Perna viridis was monitored to assess the influence of various endogenous and exogenous parameters. Temperature had a positive, significant, effect on heart rate; the Q₁₀ ranged from 2.5 to 2.6. Salinity, over a wide range (15-35‰), had no significant influence on heart rate reflecting the species' euryhalinity. Reduced oxygen tensions, either induced by emersion or seawater hypoxia, elicited rapid, significant, bradycardia. Positive inotropisms (indicative of greater heart output) were evident during seawater hypoxia and may represent an energetically advantageous mechanism of reducing heart rate while increasing stroke volume to maintain haemolymph circulation to organs associated with digestion and basal metabolism. Malnourishment for 14 days did not affect heart rate. The heart rate of larger mussels was slower than those of smaller individuals. Gender-based differences in P. viridis' heart rate were not present. No diurnal (24 h) variation in cardiac activity was evident while mussels were exposed to relatively stable, immersed conditions. Heart rate plasticity often reflected the ambient environmental conditions and such a flexible physiological response may partly explain the species' dominance in transitional, polluted harbours.     

New genotypes and factors associated with Cryptosporidium detection in mussels (Mytilus spp.) along the California coast

A 3 year study was conducted to evaluate mussels as bioindicators of faecal contamination in coastal ecosystems of California. Haemolymph samples from 4680 mussels (Mytilus spp.) were tested for Cryptosporidium genotypes using PCR amplification and DNA sequence analysis. Our hypotheses were that mussels collected from sites near livestock runoff or human sewage outflow would be more likely to contain the faecal pathogen Cryptosporidium than mussels collected distant to these sites, and that the prevalence would be greatest during the wet season when runoff into the nearshore marine environment was highest. To test these hypotheses, 156 batches of sentinel mussels were collected quarterly at nearshore marine sites considered at higher risk for exposure to livestock runoff, higher risk for exposure to human sewage, or lower risk for exposure to both faecal sources. Cryptosporidium genotypes detected in Haemolymph samples from individual mussels included Cryptosporidium parvum, Cryptosporidium felis, Cryptosporidium andersoni, and two novel Cryptosporidium spp. Factors significantly associated with detection of Cryptosporidium spp. in mussel batches were exposure to freshwater outflow and mussel collection within a week following a precipitation event. Detection of Cryptosporidium spp. was not associated with higher or lower risk status for exposure to livestock faeces or human sewage sources. This study showed that mussels can be used to monitor water quality in California and suggests that humans and animals ingesting faecal-contaminated water and shellfish may be exposed to both host-specific and anthropozoonotic Cryptosporidium genotypes of public health significance.     

Variability in response of four populations of Amblyseius largoensis (Acari: Phytoseiidae) to Raoiella indica (Acari: Tenuipalpidae) and Tetranychus gloveri (Acari: Tetranychidae) eggs and larvae

Raoiella indica (Acari: Tenuipalpidae) is a phytophagous mite that recently invaded the Neotropical region. A predatory mite Amblyseius largoensis (Acari: Phytoseiidae) has been found associated with R. indica in Florida. This study evaluated A. largoensis by determining its likelihood of consuming eggs and larvae of R. indica and Tetranychus gloveri (Acari: Tetranychidae) under no-choice and choice conditions. To detect variations in the response of A. largoensis to R. indica, four populations of predators were examined: (1) predators reared exclusively on R. indica in the laboratory for 2 years, (2) predators reared on T. gloveri in the laboratory for 2 months but reared on R. indica for 2 years previously, (3) predators collected from a field infested with R. indica, and (4) predators collected from a field that had never been infested with R. indica. Results of this study suggest that A. largoensis is likely to accept and consume high numbers of R. indica eggs regardless of their previous feeding experience. In contrast, all populations consumed relatively fewer R. indica larvae than the other prey tested. Predators previously exposed to R. indica were more likely to consume R. indica larvae. By contrast, predators not previously exposed to R. indica showed the lowest likelihood of choosing to feed on this prey item. Plasticity in the response of A. largoensis to R. indica larvae could be associated to selection, learning, or a combination of both. The possible implications of the observed differences in terms of biological control of R. indica are discussed.     

Seasonal patterns of metabolism and the heat shock response (HSR) in farmed mussels Mytilus galloprovincialis

Mussels (Mytilus galloprovincialis) are the main bivalves cultured in the Mediterranean Sea and in the Thermaikos gulf North of Greece. Global warming might affect these cultures since increases in the sea temperatures especially during summertime and may cause mass mortalities. Thus projections of the effects of global warming and the knowledge of the mechanisms of thermal limitation and adaptation are considered important in this context. In the present work we studied the seasonal expression of Hsp70 and Hsp90 of aquacultured mussels in nature in an effort to examine whether mussels are seasonally thermally stressed. Moreover we determined the activity of the key glycolytic enzyme PK in order to examine seasonal changes in the metabolic profile. The present data showed a biphasic seasonal pattern in the expression of Hsps in the mantle and PAM of M. galloprovincialis. The expression of inducible Hsp72 and Hsp90 increased between February and mid April, and remained constant or decreased slightly by the end of May. Hsps expression started again in early June leading to a gradual increase by mid July and remained by the end of August. The pattern of the HSR indicates increased protein turnover or protein damage in the tissues of aquacultured M. galloprovincialis between winter and summer seasons. The induction temperature is probably limited, and beyond some upper limits there is no further change in the HSR induction temperatures and the HSR sets in. PK activity in the mantle was significantly higher in winter than in spring. Early May saw a reactivation of PK to higher than spring values. Similar to mantle PK, PK activity in PAM was significantly higher in winter than in spring. A slight reactivation was observed by the end of August.     

Molecular and bioassay-based detection of Toxoplasma gondii oocyst uptake by mussels (Mytilus galloprovincialis)

Toxoplasma gondii is associated with morbidity and mortality in a variety of marine mammals, including fatal meningoencephalitis in the southern sea otter (Enhydra lutris nereis). The source(s) of T. gondii infection and routes of transmission in the marine environment are unknown. We hypothesise that filter-feeding marine bivalve shellfish serve as paratenic hosts by assimilation and concentration of infective T. gondii oocysts and their subsequent predation by southern sea otters is a source of infection for these animals. We developed a TaqMan PCR assay for detection of T. gondii ssrRNA and evaluated its usefulness for the detection of T. gondii in experimentally exposed mussels (Mytilus galloprovincialis) under laboratory conditions. Toxoplasma gondii-specific ssrRNA was detected in mussels as long as 21 days post-exposure to T. gondii oocysts. Parasite ssrRNA was most often detected in digestive gland homogenate (31 of 35, i.e. 89%) compared with haemolymph or gill homogenates. Parasite infectivity was confirmed using a mouse bioassay. Infections were detected in mice inoculated with any one of the mussel sample preparations (haemolymph, gill, or digestive gland), but only digestive gland samples remained bioassay-positive for at least 3 days post-exposure. For each time point, the total proportion of mice inoculated with each of the different tissues from T. gondii-exposed mussels was similar to the proportion of exposed mussels from the same treatment groups that were positive via TaqMan PCR. The TaqMan PCR assay described here is now being tested in field sampling of free-living invertebrate prey species from high-risk coastal locations where T. gondii infections are prevalent in southern sea otters.     

Presidential address: rediscovering parasites using molecular tools--towards revising the taxonomy of Echinococcus, Giardia and Cryptosporidium

Molecular biology has provided parasitologists with a fantastic variety of techniques that have had a major impact on research into parasites and parasitism. Molecular tools have revealed the extent and nature of genetic diversity in parasites and this information has made a significant contribution to studies on the population genetics and evolutionary biology of parasites. Similarly, epidemiology has benefited enormously from the application of molecular tools in terms of studying parasite life cycles and transmission, and in the development of specific and sensitive methods for diagnosis and surveillance. However, the theme I wish to develop in this paper is concerned with the contribution molecular tools have made to parasite taxonomy and systematics, and in particular, the fact that in many cases molecular tools are validating the proposals made many years ago by taxonomists and biologists which were discounted or not fully accepted at the time. To do this I have chosen four examples (Echinococcus, Entamoeba, Giardia, Cryptosporidium) where recent research involving molecular characterisation has confirmed observations made many years ago and has resulted in a need to revise the taxonomy of different groups of parasites.     

The metallothionein genes of Mytilus galloprovincialis: genomic organization, tissue expression and evolution

Recently, increasing interest has been directed to the study of metallothioneins (MTs), which are small proteins that are able to bind metal ions. The induction of MT synthesis after exposure to metal or other environmental contaminants in a large number of aquatic invertebrates makes these proteins good biomarkers in water monitoring programs. Within bivalves, the species Mytilus galloprovincialis and Mytilus edulis represent model organisms for these types of studies, as well as for molecular studies regarding the expression and characterization of MT encoding genes. In the present paper, we focused on the genomic characterization, evolutionary, and tissue-expression analyses of the MT-10, MT-10 Intronless, and MT-20 genes in M. galloprovincialis. The comparison of the genomic sequences showed the presence of long nucleotide stretches within the introns of the MT genes that are conserved between M. galloprovincialis and M. edulis. These non-coding conserved sequences may contain regulatory motifs. Real-Time RT-PCR experiments revealed that, at the basal conditions, the MT-10 and MT-10 Intronless genes are expressed at levels considerably higher than the MT-20 gene, mainly in the digestive gland and gill tissue. The strong induction of the MT-20 gene expression detected in a field-collected sample is associated with the up-regulation of both the MT-10 and MT-10 Intronless genes. Evolutionary analysis revealed signals of localized positive selection that, together with the tissue-expression data, support a possible functional diversification between the MTs encoded by the MT-10 and MT-10 Intronless genes.     

Respiratory responses to temperature and hypoxia in the nonindigenous Brown Mussel, Perna perna (Bivalvia: Mytilidae), from the Gulf of Mexico

The respiratory responses to increasing temperature and progressive hypoxia were examined relative to temperature acclimation in the nonindigenous, brown mussel, Perna perna (Mytilidae) from the Gulf of Mexico. When oxygen uptake rate (V?_O2) was recorded at near full air O₂ saturation, rate-temperature curves for Texas specimens of P. perna were sigmoidal, V?_O2 generally increasing with increasing temperature but becoming suppressed as temperatures approached 10 and 30 °C, corresponding closely to this species' incipient thermal limits. At each tested temperature, V?_O2 did not differ among individuals acclimated to 15, 20, or 25 °C. Lack of thermal acclimation was also reflected in acclimatory Q₁₀ values>1.0 (range=1.34-2.14) recorded across acclimation groups at test temperatures equivalent to acclimation temperature. Low acute respiratory Q₁₀ values in all acclimation groups across 15-20 °C indicated a limited capacity for thermal regulation of V?_O2 within this temperature range. The ability of P. perna to regulate O₂ uptake with progressive hypoxia was temperature-dependent, increasing from poor O₂ regulation at 10 °C to good regulation at 30 °C. The O₂ regulatory ability of P. perna and other open-water mytilids in declining O₂ concentrations does not greatly differ from that of estuarine heterodont bivalves, suggesting that it is not a major factor preventing open-water species, such as P. perna, from invading estuarine environments. However, P. perna's inability to regulate O₂ uptake at temperatures>25 °C combined with its relatively low upper thermal limit of 30 °C will likely prevent it from establishing permanent estuarine populations on Gulf of Mexico shores.     

Comparative cryopreservation study of trochophore larvae from two species of bivalves: Pacific oyster (Crassostrea gigas) and Blue mussel (Mytilus galloprovincialis)

Oysters and mussels are among the most farmed species in aquaculture industry around the world. The aim of this study was to test the toxicity of cryoprotective agents to trochophore larvae from two different species of bivalves and develop an improved cryopreservation protocol to ensure greater efficiency in the development of cryopreserved trochophores (14 h old oyster larvae and 20 h old mussel larvae) to normal D-larvae for future developments of hatchery spat production. The cryopreservation protocol producing the best results for oyster trochophores (60.0 ± 6.7% normal D-larvae) was obtained by holding at 0 °C for 5 min then cooling at 1 °C min⁻¹ to −10 °C and holding for 5 min before cooling at 0.5 °C to −35 °C, holding 5 min and then plunging into liquid nitrogen (LN), using 10% ethylene glycol. For mussel experiments, no significant differences were found when cooling at 0.5 °C min⁻¹ or at 1 °C min⁻¹ for CPA combinations with 10% ethylene glycol and at 0.5 °C min⁻¹. Using these combinations, around half of trochophores were able to develop to normal D-larvae post-thawing (48.9 ± 7.6% normal D-larvae).     

Genetic and morphometric characterization of mussels (Bivalvia: Mytilidae) from mid-atlantic hydrothermal vents.

Mussels were collected from deep-sea hydrothermal vents along the Mid-Atlantic Ridge. Specimens from the Snake Pit site were previously identified genetically and anatomically as Bathymodiolus puteoserpentis, but the relationships of mussels from other sites (Logatchev and Lucky Strike) were unclear. Molecular genetic and morphological techniques were used to assess differences among these mussel populations. The results indicate that the range for B. puteoserpentis extends from Snake Pit to Logatchev, and that an unnamed second species, B. n. sp., occurs at Lucky Strike. Analysis of mitochondrial NADH dehydrogenase subunit 4 (ND4) revealed 13% sequence divergence between the two species. Nei's genetic distance (D) based on 14 allozyme loci was 0.112. A multivariate morphometric analysis yielded a canonical discriminant function that correctly identified individuals from these sites to species 95% of the time.     

Agonistic interactions between the invasive green crab, Carcinus maenas (Linnaeus) and juvenile American lobster, Homarus americanus (Milne Edwards)

Invasive organisms have the potential for competition with native organisms. In the Southern Gulf of St. Lawrence, juvenile American lobsters have a potential spatial overlap with adult green crabs. Crustaceans use agonistic behaviour to settle disputes, with the larger organism often winning contests for limited resources such as food and shelter. Two experiments were carried out using adult green crabs (53-76 mm carapace width) and juvenile American lobsters (28-57 mm carapace length). The first experiment used a limited food resource. We found that green crabs were the first to the food in all trials, fed in significantly more trials than lobsters and spent a significantly greater proportion of time with the food. The lobsters were only able to displace the green crabs from the food in 2 of 65 attempts. The second experiment was designed to examine shelter competition; unexpectedly some predation by green crabs on lobsters occurred, which allowed us to test hypotheses about how relative size and shelter use affect predation. Green crabs captured and consumed juvenile lobsters in 6 of 11 trials. The lobsters that survived spent significantly more time in shelter. There was no clear relationship between shelter use and size of lobster. The lobsters that were larger in relation to the green crabs suffered a higher rate of predation, which we believe was due to more conspicuous activity and less use of shelter. It appears that green crabs have the potential to negatively impact native juvenile lobster.     

Sex, size and colour in a semi-terrestrial crab, Heloecius cordiformis (H. Milne Edwards, 1837)

We investigated the relationship between sex, size and colour in the little studied Australian endemic semaphore crab, Heloecius cordiformis, and related it to the crabs' social system with the aim of identifying the potential signalling function of claw colour.Equal sampling of crabs from all size classes revealed a strong relationship between sex, size and claw colour. Purple-clawed males were larger and had larger claws than pink-, orange- or green-clawed males. Male claws showed positive allometric growth: relative to body size, purple-clawed males had larger claws. The largest females had pink claws; the few with purple claws were no larger than immature green-clawed crabs. Female claws grow isometrically with the body so the relative claw size did not differ among the female colour classes. Quantitative measurements of claw colour revealed spectral differences between these subjectively described colours. The purple claws typical of large males also contrasted more strongly against the mudflat background than the other colours.Heloecius copulate outside female-owned burrows and probably within male-owned burrows. The male's waving display, in which both claws are raised and lowered, may feature in both mating strategies: as a territorial display and to attract wandering females. Large males are competitively superior so size, and potentially colour, are important in territorial disputes and may also feature in mate choice.     

Effects of epibiotic algae on the survival, biomass and recruitment of mussels, Mytilus L. (Bivalvia: Mollusca)

Habitats composed of living ‘ecosystem engineers’, such as mussels, are subject to direct and indirect interactions with organisms that live among them. These interactions may affect the presence and structure of habitat, and hence, the associated taxa. We examined the direct effects of epibiotic algae on the survival, biomass and recruitment of mussels (Mytilus L.) on the west coast of Ireland. A field experiment showed that the presence of epibiotic fucoid algae reduced the likelihood of survival of mussels during storms. We also found that the strength of attachment of mussels did not increase in the presence of epibionts. Another in situ experiment revealed that the presence of ephemeral epibiotic algal mats had no effect on the biomass of host mussels, suggesting no effect on mussel growth or production. The abundance of small mussels (< 5 mm) covaried with cover of epibiotic algae at one location, but experimental results suggest no direct effect of the algae on recruitment unless through the action of chemical cues which linger after the removal of algae. We have identified a negative direct interaction between epibiotic algae and mussels on exposed rocky shores, which may often be characterised by bottom-up regulation. It is thought that positive interactions may be more important on more sheltered or sedimentary shores where top-down processes are more likely to dominate.     

Morphology and taxonomy of the microsporidium Liebermannia covasacrae n. sp. from the grasshopper Covasacris pallidinota (Orthoptera, Acrididae)

During a survey for grasshopper pathogens in Argentina in 2005-2006, individual Covasacris pallidinota from halophylous grasslands in Laprida, Buenos Aires province were found to be infected with a microsporidium. Infection was restricted to the salivary gland epithelial cells. The microsporidium produced ovocylindrical spores averaging 2.6 ± 0.28 × 1.4 ± 0.12 μm (range 2.2-3.4 × 1.1-1.7 μm), which resembled in size and shape the spores of Liebermannia patagonica and L. dichroplusae, two recently described species that also parasitize Argentine grasshoppers. The life cycle of the microsporidium included the formation of polynucleate, diplokaryotic, moniliform, merogonial plasmodia wrapped in flattened cisterns of the host endoplasmic reticulum (ER). Plasmodia divided to produce diplokaryotic cells. The latter underwent elongation, dissociation of diplokarya counterparts, vacuolization, dismantling of the host ER envelope, and deposition of electron-dense material outside the plasma membrane. The resultant binucleate sporogonial plasmodia divided into two uninucleate sporoblasts, which eventually transformed into spores. Uninucleate spores contained a lamellar polaroplast, embraced by an elongated polar sac, anchoring disc, 3-5 polar filament coils, and a cluster of anastomizing tubules (sporoblast trans-Golgi, posterosome) at the posterior end. Sequence similarity of the SSU rDNA of the newly discovered microsporidium (Genbank accession no. EU709818) to L. patagonica and L. dichroplusae was 99% and 97%, respectively, suggesting that the three species belong to one genus. All three species fell into one clade in SSU rDNA-based phylogenetic trees produced by neighbor joining, maximum parsimony, and maximum likelihood analyses with 100% statistical support. We assign the name Liebermannia covasacrae to this microsporidium. It can be easily differentiated from both congeners by host species, tissue tropism, type of sporogony, and several features of morphology. Comparison of the three Liebermannia spp. demonstrates that the nuclear phase (dikaryotic versus monokaryotic spores) and type of sporogony (polysporous versus disporous) may vary in closely related species.     

Sexual dimorphism of craniological characters in Eurasian badgers, Meles spp. (Carnivora, Mustelidae)

An analysis of 30 craniological characters of Eurasian badgers (Meles spp.) revealed different levels of sexual size dimorphism (SSD) and geographic variation in the three different species. SSD is displayed mostly in the general size of the skull (condylobasal length, zygomatic width, width of rostrum, and cranial height) and mandible (height of the vertical mandibular ramus, total length of the mandible, and length between the angular process and infradentale), and in some dental characters (length of the upper molar M¹). The most stable size dimorphism is manifested in the size of the canines, which is pronounced in all studied samples. SSD is not apparent in the length of the auditory bulla, the postorbital width, the minimum palatal width, the length of the lower molar M₂, and the talonid length of the lower carnassial tooth M₁.In both the European badgers, Meles meles, and the Asian badgers, Meles leucurus, two geographic forms that differ in the degree of SSD have been found. The most pronounced SSD of cranial characters is found in the Transcaucasian form of Meles meles and the Far-Eastern form of Meles leucurus. In the large European form of Meles meles, SSD is less pronounced in both absolute and relative criteria than in the smaller Transcaucasian form. An analogous situation is observed in the larger Siberian and smaller Far-Eastern forms of Meles leucurus. In the Japanese badgers, Meles anakuma, a downsizing of the skull is accompanied by a decrease in SSD (except in canine size) in comparison to the continental species. The significant differences in the manifestation of SSD in the Eurasian badgers support an earlier hypothesis (Abramov, 2001. Proc. Zool. Inst. Russ. Acad. Sci. 288, 221-233; Abramov, 2002. Russ. J. Theriol. 1 (1), 57-60; Abramov, 2003. Small Carnivore Conserv. 29, 5-7) that Meles meles, Meles leucurus, and Meles anakuma are separate species. The differences in the level of SSD among and within these three species of badgers may be attributed not to differences in the diet or social structure, but to the history of speciation events and formation of intraspecific distribution ranges.     

Invasion by Limnoperna fortunei (Dunker, 1857) (Bivalvia, Mytilidae) of the Pantanal Wetland, Brazil

Limnoperna fortunei (Bivalvia, Mitylidae) was introduced into South America in 1991 in the La Plata River (Argentina). It arrived in the ballast water of ships coming from Asia, where this species is native. It was first observed in 1998 in the Paraguay River. Limnoperna was introduced into the Pantanal region as hull fouling of vessels using the Paraguay–Parana waterway. This study describes how L. fortunei came to the Pantanal region, and provides details of its occurrence, density, and impacts. From 1999 to 2002, observations and sampling on natural and artificial substrates in the Paraguay River were made. Some aspects of the spread and impacts, based on local community information, were also analyzed. On artificial substrate the density reached 523.8 individuals m⁻² and on natural substrate (rocks), up to 10,000 individuals m⁻² were found. The densities observed were quite low compared to those found in Southern Brazil, where values up to 100,000 individuals m⁻² have been recorded in the last 3 years. In the Paraguay River, the population density of L. fortunei can be negatively impacted by periodic low levels of dissolved oxygen and decreases in pH to between 5 and 6. Such conditions are frequently present during the periodic flooding or inundation of this area. Under these conditions, a high mortality of L. fortunei was recorded in March of 2002, on both natural and artificial substrates. Despite low densities, L. fortunei can colonize water cooling systems of boats, obstructing water circulation and causing motor overheating. Accumulation in water supply equipment, such as pumps and pipes has also been observed. An erratum to this article is available at .