Life history and reproductive ecology of the endangered Itasenpara bitterling Acheilognathus longipinnis (Cyprinidae) in the Himi region,central Japan

The life history, reproductive ecology and habitat utilization of the Itasenpara (deepbody) bitterling Acheilognathus longipinnis were investigated in a lowland segment of the Moo River in Toyama Prefecture, central Honshu, Japan. Analysis of 1285 individuals revealed that the study population comprised a single size class, an age at maturation of 3 months and a life span of 1 year. On the basis of the growth pattern, the life cycle was divided into two stages: the juvenile stage, characterized by rapid growth, and the adult stage at which growth ceased. Spawning by A. longipinnis was recorded between early September and late October. Female A. longipinnis in the 0+ year age class began to mature when they reached a standard length (L_S) of 56·4 mm. Mature females had a large clutch size (maximum 273 eggs) and deposited highly adhesive and relatively large eggs (2·55 mm³; major axis, 3·12 mm; minor axis, 1·22 mm) via a short ovipositor (mean length, 21·5 mm) into freshwater mussels. The embryos remained in the gill cavities of the freshwater mussels (used as a spawning substratum) and emerged as juveniles (L_S, 9 mm). Habitat utilization during spawning was analysed using a generalized linear model. The best‐fit model showed that three environmental factors (freshwater mussel availability, water depth and vegetation cover) were important variables for habitat utilization by A. longipinnis. Shallow areas (water depth, 250–330 mm) created for rice paddy management and areas with an abundance of cover were particularly effective for predator avoidance. These results suggest that maintenance of water level fluctuations corresponding with rice cultivation and the abundance of vegetation on the river bank (particularly avoidance of concrete revetments) is essential for conservation of this species under current practices for rice cultivation in Japan.     

Species traits and catchment‐scale habitat factors influence the occurrence of freshwater mussel populations and assemblages

相似文献   

Integration of “Innate” and “Learned” Components within the IRME for Mussel Recognition in the European Bitterling Rhodeus amarus (Bloch)

The European bitterling (Rhodeus amarus Bloch) practises a rather unusual method of spawning by using the favorable conditions in the gills of a living freshwater mussel (genera Unio and Anodonta) for the embryonic development of its fry. The capacity of mussel recognition was studied in inexperienced individuals with the aid of simultaneous preference tests in which pairs of dummies with increasing similarity to mussels were presented to the animals. The frequency of mussel-referred motor patterns, which were supposed to be species-specific (Wiepkema 1961), supplied the evaluation criterion. The results revealed a hierarchy of effectiveness within the class of relevant stimuli and showed certain effects of additivity typical of an Innate Releasing Mechanism or IRM. By far the most effective stimulus consisted in the specific smell of the mussel which is composed of at least three constituents (protein, hyaluronic acid, ammonium). The water flow itself, produced by the mussel in order to maintain nutritive and respiratory functions, was effective depending on its velocity (3 < v < 12 cm/s), its orientation (suction produced no effect), its direction (vertical > horizontal) and the shape of its field (oval). Within the visual modality only two simple perceptory patterns could be detected (dark spot on a clearer surface, straight horizontal edge), but the visual shape of the mussel as a whole was ignored by inexperienced individuals. Nevertheless the bitterlings are able to learn the shape when exposed to a living mussel and, in addition, it was even possible to condition the animals to an artificial object (inverted pot of clay) by using the mussel-smell flow as a reinforcing stimulus. The final discussion deals with the question of whether it is possible to interpret these “innate” respectively “learned” components of the IRME as sensory counterparts of behavioral structures which simply serve different functions by referring to correspondingly different sectors of the environment. In such a case the epistemological dichotomy regularly associated with the notions of “innate” (= “pre-given phylogenetical knowledge”) and “learned” (= “cognitive increase during ontogeny”) would suffer incisive questioning.     

Long‐term mark‐and‐recapture study of a freshwater mussel reveals patterns of habitat use and an association between survival and river discharge

相似文献   

Determining Management Units in Southeastern Brazil: The Case of Astyanax bimaculatus (Linnaeus, 1758) (Teleostei: Ostariophysi: Characidae)

Characterization, management and protection of biodiversity are the most prominent challenges in conservation biology. Analyses on molecular similarity (Random Amplified Polymorphic DNA-Polymerase Chain Reaction, RAPD-PCR) and morphologic patterns (morphometric and meristic characters) were performed to evaluate the existence of population structuring in the Doce river basin, in a widespread small-sized characin, Astyanax bimaculatus. Three hundred (300) individuals were collected from six locations isolated by waterfalls or dams, in the Doce river basin, Minas Gerais State, Brazil. Genetic differentiation among tributaries was significant (p<0.00001) and accounted for 21% of total variance (p<0.00001). Only the Grande waterfall of the Casca river was an effective factor for differentiation of populations (p<0.00001), and meristic characters were also consistent with molecular data. We concluded that genetic and morphologic variation of this species was not necessarily associated with waterfalls and that molecular and meristic data are effective predictors of population divergence in this basin. The consequences of these findings for the protection and management of aquatic biodiversity were discussed.     

Invasive zebra mussel (Dreissena polymorpha) threatens an exceptionally large population of the depressed river mussel (Pseudanodonta complanata) in a postglacial lake

1. Freshwater mussels are in decline worldwide, with the depressed river mussel Pseudanodonta complanata being one of the rarest and most endangered species in Europe. Invasive mussels are suspected to be an important factor of decline, but there is little information on their interaction with native species.
2. This study analyzed densities, depth distribution, and individual sizes and weights in one of the largest known populations of P. complanata in Europe in relation to the co‐occurring invasive zebra mussel Dreissena polymorpha and other mussel species, using a systematic transect analysis.
3. Pseudanodonta complanata was the dominant unionid species in Lake Siecino reaching densities of up to 26 ind/m², with half of the specimens found at a water depth of 2.0–4.0 m. Densities were highest on sandy substrates in areas of underwater currents. In contrast, 67% of native Unio tumidus were found at depths < 1 m, indicating different habitat preference.
4. In the study area, 91% of P. complanata, 92% of U. tumidus, and all Anodonta individuals were fouled by D. polymorpha. The dreissenid:unionid mass ratio (mean ± SD; maximum) was 0.43 ± 0.56; 4.22 and 0.86 ± 1.87; 8.76 in P. complanata and U. tumidus, respectively. Pseudanodonta complanata fouled with D. polymorpha were impaired in their anchoring capability and had shell deformations potentially affecting shell closing and filtration activity. Fouling intensity was negatively correlated with unionid density, potentially leading to accelerated population declines.
5. The observed adverse effects of invasive zebra mussels on the depressed river mussel and the difficulties in eradicating established populations of invasive mussels suggest that D. polymorpha should be considered a serious threat to P. complanata. Therefore, the further spread of zebra mussels into habitats with native unionids needs to be avoided by all means.

     

Bioaccessibility of Cd,Cr, Cu,Mn, Ni,Pb, and Zn in Mediterranean mussel (Mytilus galloprovincialis Lamarck, 1819) along the southeastern Black Sea coast

The adverse effect of seafood consumption on human health is related to the bioaccessibility in contrast with the total heavy metal level in the tissues. In this study, bioaccessibility of Cd, Cr, Cu, Mn, Ni, Pb, and Zn in Mediterranean mussel (Mytilus galloprovincialis Lamarck, 1819) edible soft tissues collected along the southern Black Sea coast were investigated using in vitro digestion model. Total Pb concentration in the tissues was found to be higher than the maximum permissible limits set by European Commission. The bioaccessibility of metals in the tissues was found to be decreased in the order: Ni (83.11%) > Cu (80.47%) > Zn (76.86%) > Cd (73.32%) > Mn (69.11%) > Pb (61.07%) > Cr (58.44%). While significant positive linear regression was observed between total and bioaccessible concentrations for Mn, Pb, and Ni, significant negative linear regression was found for Cd (p < .05). The hazard quotients (HQ) calculated using bioaccessible amount were detected lower than the limit (HQ <1), which may not pose a potential hazard to humans reported by US Environmental Protection Agency. In sum, mussel consumption from sampling sites may cause a potential risk concerning human health especially for Cd and Pb in case of increased portion sizes.     

Reproductive Ecology and Host Utilization of Four Sympatric Bitterling (Acheilognathinae,Cyprinidae) in a Lowland Reach of the Harai River in Mie,Japan

Bitterling are fishes that use freshwater mussels for oviposition. The reproductive ecology and pattern of mussel utilization of four sympatric species of bitterling, Acheilognathus rhombeus, A. tabira tabira, Tanakia lanceolata, and T. limbata, were investigated in a lowland river with seven sympatric mussel species. Three bitterling species are spring spawners with overlapping spawning seasons. A. rhombeus is an autumn-spawning species and is temporally isolated in its reproduction from the other species. Ovipositor length during oviposition of T. limbata and T. lanceolata was short, while those of A. tabira tabira and A. rhombeus were long. Most T. limbata inhabited near-shore areas, whereas the two other spring-spawning species were distributed across the entire river. All bitterling species used Inversidens brandti, Obovalis omiensis and Inversiunio jokohamensis as spawning hosts, but not the other mussel species available. T. lanceolata, A. tabira tabira and A. rhombeus showed spawning preferences for O. omiensis and I. brandti. However, T. limbata did not show clear preferences for any of the mussel species they used. A. t. tabira showed a significant preference for large I. brandti in offshore areas, while the other spring-spawning bitterling showed a preference for mussels inshore. These results are discussed in the context of reproductive resource partitioning.     

Habitat characteristics contributing to local occupancy and habitat use in rock pool <Emphasis Type="Italic">Daphnia</Emphasis> metapopulations

The effects of invasive macrophytes, water level fluctuations and predation on freshwater unionids Pyganodon grandis and Utterbackia imbecillis were studied in three small impoundments in Northeastern Texas in 2003–2005. Mussel density was sampled with quadrats. Mortality, associated with the water level fluctuations and predation, was estimated by collecting dead shells on the shore at about two month intervals. In two ponds, horizontal distribution of unionids was limited by dense beds of invasive and noxious macrophytes (mainly Eurasian watermilfoil Myriophyllum spicatum and American lotus Nelumbo lutea): mussel densities were significantly lower in these macrophyte beds (P < 0.001). In the third pond with the lowest density of macrophytes (stonewort Chara sp.), unionids were distributed more evenly, and the average unionid biomass was the highest among all ponds studied. Vertical distribution of unionids in all ponds was likely limited by low oxygen at depth >2 m. The total amount of shells found on the shore per year varied from 0.1% to 28% of the total population in the pond and was negatively correlated with water level (r = −0.72 to −0.81, P < 0.005). Mammalian predators consumed up to 19% of the total unionid population and predation was facilitated by water level fluctuations. Handling editor: K. Martens     

The effect of Hurricane Katrina on the mussel assemblage of the Pearl River, Louisiana

We sampled the mussels of the Pearl River along the eastern border of Louisiana, USA, in 1997 and 2007. Hurricane Katrina followed the pathway of the river in August 2005, and we were interested in detecting any resulting decreases in mussel abundance or diversity. The mussel assemblage was relatively stable, despite the hurricane and a drought in the Pearl River Basin in 2006 and 2007. We detected no change in average species richness per site, and the total number of mussels collected per site (e.g., collection per unit effort) actually increased in 2007. Species importance curves comparing the two studies did, however, suggest a reduction from 29 to 23 species. Monte Carlo simulations and comparisons of assemblage similarity also suggested that Glebula rotundata increased at the expense of Potamilus purpuratus and Villosa lienosa, possibly because it was more tolerant of salt water intrusion. Eight of 13 mussels with adequate sample sizes had different adult size structures in the two surveys, either increasing or decreasing in mean shell length during the 10 years. Large individuals were rare for the two species that decreased in relative abundance in 2007. Semi-quantitative sampling appeared adequate here to compare relatively long-term changes in mussel diversity and adult size structure. However, more research on natural variation in assemblage structure and mussel size distributions is needed to understand the importance of disturbances like hurricanes or droughts.     

The role of the blue mussel Mytilus edulis in the cycling of nutrients in the Oosterschelde estuary (The Netherlands)

The fluxes of particulate and dissolved material between bivalve beds and the water column in the Oosterschelde estuary have been measured in situ with a Benthic Ecosystem Tunnel. On mussel beds uptake of POC, PON and POP was observed. POC and PON fluxes showed a significant positive correlation, and the average C:N ratio of the fluxes was 9.4. There was a high release of phosphate, nitrate, ammonium and silicate from the mussel bed into the water column. The effluxes of dissolved inorganic nitrogen and phosphate showed a significant correlation, with an average N:P ratio of 16.5. A comparison of the in situ measurements with individual nutrient excretion rates showed that excretion by the mussels contributed 31–85% to the total phosphate flux from the mussel bed. Ammonium excretion by the mussels accounted for 17–94% of the ammonium flux from the mussel bed. The mussels did not excrete silicate or nitrate. Mineralization of biodeposition on the mussel bed was probably the main source of the regenerated nutrients.From the in situ observations net budgets of N, P and Si for the mussel bed were calculated. A comparison between the uptake of particulate organic N and the release of dissolved inorganic N (ammonium + nitrate) showed that little N is retained by the mussel bed, and suggested that denitrification is a minor process in the mussel bed sediment. On average, only 2/3 of the particulate organic P, taken up by the mussel bed, was recycled as phosphate. A net Si uptake was observed during phytoplankton blooms, and a net release dominated during autumn. It is concluded that mussel beds increase the mineralization rate of phytoplankton and affect nutrient ratios in the water column. A comparison of N regeneration by mussels in the central part of the Oosterschelde estuary with model estimates of total N remineralization showed that mussels play a major role in the recycling of nitrogen.     

Microbial biomass and activity in the vicinity of a mussel bed built up by the blue mussel Mytilus edulis

Our study focuses on the impact of the biosedimentary system mussel bed (Mytilus edulis) on the spatial variability of benthic microbial biomass and activity in relation to organic deposits. We sampled a transect of six stations from the muddy mussel bed towards a reference station in the sandflat in monthly intervals for 1 year. The sediment grain size fraction <63 μm and the total organic carbon (TOC) concentration decreased significantly towards the sandflat. Bacterial numbers and total microbial biomass (total adenylates) showed a high spatial variability and were not correlated to increasing distance from the mussel bed. However, a significant relationship with the TOC concentration was found. In contrast, the energetic status (adenylate energy charge) of the microbial community in the mussel bed was significantly lower than in the sandflat. A principal component analysis of the substrate-utilization pattern revealed clear differences between the microbial communities in the mussel bed and in the sandflat. Our results indicate that the sandflat may be dominated by a relatively specialized benthic microbial community with an increased efficiency in utilizing organic carbon sources. As a disadvantage, however, such r-strategists are only able to meet environmental changes within a comparatively narrow range. Benthic microbial communities in the vicinity of an M. edulis mussel bed, in contrast, are dominated by relative generalists with a greater physiological capacity to buffer discrete environmental changes. Such K-strategists show a lack of specialization which generally means a reduced efficiency in utilizing a particular resource. Received: 2 May 1999 / Received in revised form: 22 November 1999 / Accepted: 6 December 1999     

Interspecific and sexual differences in riverine distribution of tropical eels Anguilla spp.

A total of 261 individuals of the four tropical eel species, Anguilla celebesensis, Anguilla marmorata, Anguilla bicolor pacifica and Anguilla interioris, were collected from 12 locations around Sulawesi Island, Indonesia, to gain knowledge about the riverine distribution of tropical eels. Anguilla marmorata was predominant in the lower reaches of Poso River (94·4% of total eel catch in the sampling area), Poso Lake (93·3%), three small inlet rivers of Tomini Bay (100%) and Laa River (92·3%). Anguilla celebesensis occurred frequently in the inlet rivers of Poso Lake (63·5%). Anguilla bicolor pacifica and Anguilla interioris were rare (1.5 and 0.4%, respectively). Otolith Sr:Ca ratio electron‐probe micro analysis (EPMA) for individual migratory histories revealed that 15 A. celebesensis caught in Poso Lake and its inlet rivers were categorized into 14 river eels (Sr:Ca < 2·5) showing upstream migration seemingly at their elver stage and only one sea eel (Sr:Ca ≥ 6·0) that stayed in the marine habitat for the majority of its life after recruiting to Sulawesi Island before its late upstream migration. In A. marmorata, 19 examined eels from Poso Lake and its inlet rivers were all river eels, while 17 eels from the lower reaches of Poso River were two river eels, six sea eels and nine estuarine eels (2·5 ≤ Sr:Ca < 6·0) that mostly lived in the brackish water. The sex ratio of A. celebesensis was highly skewed towards a dominance of females (99%). In A. marmorata, females were predominant in Poso Lake (95·2%), its inlet rivers (94·7%) and Laa River (100%), while males were more frequent in the lower reaches of Poso River (76·5%) and small inlet rivers of Tomini Bay (94·1%). These results indicate that the riverine distribution pattern of tropical eels differs among species and between sexes.     

Partial replacement of dietary buffalo meat on the bone with chicken carcass improves serum antioxidant profile of zoo‐housed Indian leopards (Panthera pardus fusca)

This experiment was conducted to study the effect of gradual replacement of dietary buffalo meat on the bone (BMB) with chicken carcass (CC) on nutrient utilization, serum cortisol, and total serum antioxidant profile of zoo‐housed Indian leopard. Twelve adult leopards were randomly distributed into a replicated Latin square design comprising three treatments, three periods, four animals, and three sequences. Leopards in group T₁ were fed normal zoo diet of BMB. On the basis of dry matter, 10% and 20% of BMB was replaced with CC in groups T₂ and T₃, respectively. Each experimental period comprised 21 days. During each period, a digestion trial of 4‐day collection period was conducted after an adaptation period of 17 days. On Day 21 of each experimental period, blood was collected from all the animals by puncturing the ventral coccygial vein. Intake and apparent digestibility of major nutrients were similar among the groups. Replacement of 20% BMB with addition of CC increased (p < 0.001) the calculated supply of I, niacin, and vitamin A. Carotenoid intake increased (p < 0.01) with increased level of CC in the diet. Serum concentration of cortisol decreased (p < 0.01) whereas serum concentration of total carotenoids increased (p < 0.001) with increased level of CC in the diet. Serum concentration of antioxidant enzymes increased (p < 0.001) with increased level of CC in the diet. It was concluded that replacement of 20% of BMB with CC increased antioxidant profile. This may reduce oxidative stress in zoo‐housed Indian leopards without any adverse effect on nutrient utilization.     

Estimation of vital population rates to assess the relative health of mussel assemblages in the Upper Mississippi River

1. Native freshwater mussels are a guild of benthic, filter feeding invertebrates that perform important ecological functions in rivers. Because of their long lifespans (30–50 years or longer), mussels are slow to respond to human-induced alterations. Thus, development of sensitive indicators of mussel population responses to river conditions and management would be beneficial. Compared to marine species, estimation of vital rates (e.g. survival, growth) in freshwater mussels has received little attention.
2. We placed passively integrated transponder tags on 578 mussels of four species (Amblema plicata, Cyclonaias pustulosa, Obliquaria reflexa, and Pleurobema sintoxia) in a well-studied mussel assemblage in a side channel of the upper Mississippi River. Growth and survival of tagged mussels were assessed annually for 4 years across core (high density) and peripheral (low density) areas of the assemblage.
3. Overall survival was highly variable, ranging from c. 15 to 90%, and was related to life history, habitat quality, and hydrologic events. Survival, which varied significantly among species and over time, was consistently higher in the dense and species-rich core of the mussel assemblage, relative to the periphery because substrates were consistently more stable in the core of the mussel bed relative to the periphery. Substrate movement during low flows was an order of magnitude lower in the core relative to the periphery, and survival was inversely related to stability of river substrates. Patterns in habitat-specific survival indicate source–sink population dynamics such that mussels in the core habitat provide recruitment to the periphery, but mussels in the periphery are subject to unsustainably low survival; additional studies to track the source of recruitment in the periphery are needed to test this hypothesis.
4. Growth rate did not vary significantly between core and peripheral areas but did vary by species. Growth rate (proportional change per year) declined with age, and was similar at mean age for A. plicata (0.016 per year), P. sintoxia (0.015 per year), and C. pustulosa (0.013 per year), but much lower for O. reflexa (0.008 per year).
5. Effective management decisions for mussels requires a better understanding of how vital rates govern populations and how they vary across a suite of physical and biological factors. Information on how population vital rates vary among species and over time gives managers another tool to understand how mussels may respond to management actions such as habitat restoration projects. Given the importance of substrate stability inferred from this study, management actions that maintain or increase substrate stability are likely to result in high quality mussel assemblages and may restore a valuable component of ecosystem function in this region.

     

DNA barcoding uncovers extensive cryptic diversity in the African long-fin tetra Bryconalestes longipinnis (Alestidae: Characiformes)

To investigate the presence of cryptic diversity in the African longfin-tetra Bryconalestes longipinnis, we employed DNA barcoding in a phylogeographic context, as well as geometric morphometrics, documenting for the first time genetic and body shape variation in the species. Analysis of cytochrome oxidase I gene (coI) sequence variation exposed extremely high levels of genetic differentiation among samples from across the geographic range of the species (up to 18%), certainly much greater than the traditionally employed c. 3% sequence divergence heuristic threshold for conspecifics. Phylogeographic analyses of coI data revealed eight clusters/clades that diverge by >4% and up to 18% (p-distance), potentially representing cryptic members of a species complex. A clear biogeographic pattern was also uncovered, in which the two main coI lineages corresponded geographically with the upper Guinea (UG) and lower Guinea (LG) ichthyofaunal provinces of continental Africa, respectively. Within each of these main lineages, however, no apparent phylogeographic structuring was found. Despite strong genetic differentiation, there is considerable overlap in body shape variation between UG and LG populations. For the most part, morphological variation does not match the strength of the molecular phylogeographic signal. Therefore, the ability to reliably utilise external body shape for regional delimitation remains elusive. Further anatomical investigation appears necessary to establish whether compelling diagnostic morphological features do exist between the divergent lineages of the B. longipinnis complex uncovered in this study.     

Association of genetic polymorphism inGH gene with milk production traits in Beijing Holstein cows

Associations were analysed between polymorphisms of the growth hormone gene (GH-MspI) (localized in intron 3) and milk production traits of Beijing Holstein cows (a total of 543 cows). Polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method was used for identification of various geno-types. Frequencies of genotypes were 0.77, 0,21 and 0.02 for A/A, A/B and B/B, respectively. The frequency of theGH ^A allele is 0.875. The results of the least squares means show that in all three lactations, theGH A/A cows yielded more milk (P < 0.01 for lactation I andP 0.05 for lactations II and III), whereas A/B cows showed higher milk fat content than A/A individuals (P < 0.05 for lactations I and II, andP < 0.01 for lactation III). The A/A cows yielded more fat than A/B individuals (P < 0.01 only in lactation I). The A/A cows yielded more milk protein than A/B individuals (P < 0.01 for lactations I, II, and III). The A/A cows produced milk of higher protein content than of A/B individuals (P < 0.05 only in lactation II).     

Invasion of an indigenous Perna perna mussel bed on the south coast of South Africa by an alien mussel Mytilus galloprovincialis and its effect on the associated fauna

The introduced mussel Mytilus galloprovincialis is progressively increasing in abundance along the south coast of South Africa. Quantitative 0.1 m² samples were collected in the mid-zone of an indigenous Perna perna mussel bed in the 1980s prior to the arrival M. galloprovincialis (12) and in the 2000s during the M. galloprovincialis invasion (16). In addition, in situ counts of M. galloprovincialis were done on eight occasions between 1993 and 2005, and in the low- and high-zones on four occasions. In the mid-zone M. galloprovincialis was absent until 1987, its mean densities were low (< 15 individuals/0.1 m²) between 1993 and 1996, but thereafter increased steadily, peaking in 2004 (at 721 individuals/0.1 m²), before declining in 2005 (331 individuals/0.1 m²). The greatest densities of M. galloprovincialis were recorded at the high-zone (1121 individuals/0.1 m²) and the smallest in the low-zone. As M. galloprovincialis numbers increased, there was an associated, but smaller decline in P. perna numbers and the overall density of mussels increased significantly (P < 0.05). No major change was recorded in the size composition of P. perna. The density of associated fauna differed significantly (P < 0.01) between sampling dates with the lowest and highest values being recorded near the ‘beginning’ (2001) and ‘end’ (2005) of the invasion period respectively. These differences were largely due to variations in the density of barnacles, and the toothed barnacle Chthamalus dentatus appeared to be the only associated faunal species that was directly affected by the M. galloprovincialis invasion, experiencing a significantly (P ≤ 0.05), but temporary decline in density and biomass values.     

Effects of increasing temperatures on population dynamics of the zebra mussel <Emphasis Type="Italic">Dreissena polymorpha</Emphasis>: implications from an individual-based model

Zebra mussels (Dreissena polymorpha, Pallas, 1771) have had unprecedented success in colonizing European and North American waters under strongly differing temperature regimes. Thus, the mussel is an excellent model of a species which is able to cope with increasing water temperatures expected under global change. We study three principle scenarios for successful survival of the mussel under rising temperatures: (1) no adaptation to future thermal conditions is needed, existing performance is great enough; (2) a shift (adaptation) towards higher temperatures is required; or (3) a broadening of the range of tolerated temperatures (adaptation) is needed. We developed a stochastic individual-based model which describes the demographic growth of D. polymorpha to determine which of the alternative scenarios might enable future survival. It is a day-degree model which is determined by ambient water temperature. Daily temperatures are generated based on long-term data of the River Rhine. Predictions under temperature conditions as recently observed for this river that are made for the phenology of reproduction, the age distribution and the shell length distribution conform with field observations. Our simulations show that temporal patterns in the life cycle of the mussel will be altered under rising temperatures. In all scenarios spawning started earlier in the year and the total reproductive output of a population was dominated by the events later in the spawning period. For maximum temperatures between 20 and 26°C no thermal adaptation of the mussel is required. No extinctions and stable age distributions over generations were observed in scenario 2 for all maximum temperatures studied. In contrast, no population with a fixed range of tolerated temperatures survived in scenario 3 with high maximum temperatures (28, 30, 32°C). Age distributions showed an excess of 0+ individuals which resulted in an extinction of the population for several thermal ranges investigated. Priority programme of the German Research Foundation—contribution 14.     

Seroprevalence of <Emphasis Type="Italic">Toxoplasma gondii</Emphasis> antibodies in the Slovak Republic

One-thousand eight-hundreds forty-five individuals were examined for the presence of Toxoplasma gondii antibodies, 31.3 % prevalence of them being found by using the complement fixation test as a screening method. The determined total antibodies were present mainly in low titers which show evidence of past or latent infection. The acute stage of toxoplasmosis by the detection of specific IgM and IgA was diagnosed. The occurrence of acute toxoplasmosis in the healthy population is very low and presents only at 0.3 %. There was no significant difference between genders (p = 0.232), but significant differences in the prevalence of toxoplasmosis depending on age (p < 0.001) and regions (p = 0.007) were found.