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Abstract Phosphate-shelled brachiopods differ in filter-feeding lifestyle, with Lingula anatina an active infaunal burrower, and Discinisca tenuis a shallow marine epibenthic animal. The shells of these animals are built of organophosphatic constituents, the organic fibres/sheets reinforced with calcium phosphate to provide a sophisticated ultrastructural robustness. This investigation examined the nature of the organic fibres in order to improve understanding of how living organisms produce hierarchically structured biomaterials. Unlike powdered samples commonly used in previous studies, organic fibres were isolated for the first time and the shell fractions were purified, in order to study the content and nature of the biopolymer fibres. Biochemical methods including Calcofluor staining revealed a chitin matrix. Ultrastructural analysis, thermal gravimetric analysis, and spectroscopic analyses show that the core polysaccharide framework is composed of layers of β-chitin sheets and/or fibrils that are coated with a fibrous organic matrix. There is more chitin matrix in the L. anatina shells (26.6 wt.%) compared to the D. tenuis shells (12.9 wt.%). Taken together, the data show that the chitin matrix contributes to increased skeletal strength, making L. anatina highly adapted for life as an active burrower. In comparison, D. tenuis contains less chitin and lives as attached epibenthos in a shallow marine environment. Graphical abstract First spectroscopic evidence of β-chitin sheets in recent organophosphatic brachiopods

This study revises the caddisfly genus Rhyacophila Stephens, Rhyacophilidae, for Yakushima Island within the northern Ryukyu Archipelago in southwestern Japan. Four new species are described based on adults: Rhyacophila yakushima sp. nov. of the R. anatina Species Group, R. arakawa sp. nov. of the R. lieftincki Species Group, R. miyanoura sp. nov. of the R. yosiiana Species Group, and R. nagata sp. nov. of the R. ulmeri Species Group. Additionally, two species are recorded for the island for the first time: R. brevicephala Iwata 1927, a Japanese species, and R. shikotsuensis Iwata 1927, an East Asian species.

The metabolic activity of unionid mussels influences the oxygen fluxes and other physical and chemical characteristics in aquatic systems. Unionid oxygen consumption rate during digestion and its dependency on food availability is understudied. In laboratory conditions, we quantified the oxygen consumption rate of Anodonta anatina and Unio pictorum in response to algal concentration—0.05, 6.0 and 12.0 mg of Ash Free Dry Mass of Chlorella vulgaris L−1—and mussel dry soft-tissue mass at 19 ± 1°C. Following a 5-h feeding-period, the oxygen consumption rate (mg O2 h−1) increased with algal concentration and mussel dry mass in both species during a 2-h digestion-period. The mean oxygen consumption per gram of dry mass (mg O2 gDM−1 h−1) increased with the algal concentration in both species. The oxygen consumption rate of A. anatina was significantly greater than that of U. pictorum at a given algal concentration. The A. anatina oxygen consumption per gram of dry mass decreased with increasing dry mass. Oxygen consumption rate during digestion shows inter-specific differences and is dependent on food availability. The findings inform the species-specific quantification of oxygen consumption, and validation is required in in situ conditions.

A new spionid species Polydora lingulicola sp. nov., a novel symbiont of Lingula anatina Lamarck, 1801 is described here based on materials collected from the Yatsushiro Sea and Ariake Sea, southern Japan. Polydora lingulicola sp. nov., morphologically closest to P. glycymerica Radashevsky, 1993 and P. vulgaris Mohammad, 1972, is distinct from latter two shell-boring species by its smaller size, long maximum caruncle length, non-boring lifestyle, presence of subspherical yellow chromatophores on chaetiger 5 (visible in living specimens), and larval morphology. The new species was observed to construct mud tubes on the surfaces of L. anatina shells, with the tube apertures located near the lateral inhalant pseudosiphon of the hosts, and utilizes the water currents created by the filter-feeding host for feeding suspended food particles. Polydora lingulicola sp. nov. represents the first polychaetous annelid reported to exhibit an obligate symbiotic relationship with a lingulid brachiopod. Epibiotic polychaetes previously reported as P. cornuta Bosc, 1802 to occur on L. anatina shells from Japan in 1902 may belong to P. lingulicola sp. nov. The possibility that the wild populations of P. lingulicola sp. nov. may be vulnerable to extinction because they only associate with L. anatina, wild populations of which are near threatened by habitat loss, coastal pollution, and fishing pressure.

Inferences on the development and morphology of extinct brachiopods must be informed by the ontogeny and shell ornamentation of extant brachiopods. Although the adult shells of extant brachiopods are well studied, detailed descriptions of the embryonic and juvenile shells of extant lingulides are lacking. Here, we describe in detail the shells of juveniles ofLingula anatinaLamarck, 1801 from Vietnam and the Republic of the Philippines. The following previously unknown properties of the lingulide shell are described: (1) a distinct border between the protegulum and the brephic shell; (2) drapes that develop on both the protegulum and brephic shell; and (3) the notched anterior margin of the brephic shell. The drapes and cogs on the brephic shell may be caused by the formation of setal follicles during the planktonic stage. Specimens ofL. anatinafrom the Philippines have larger brephic shells than those from Vietnam, probably because the former have a longer planktonic stage. Based on comparisons of the first-formed shells of extant brachiopods with published data on fossil brachiopods, we suggest that the life cycle of extant lingulides, in which planktotrophic juveniles with a shell hatch from the egg envelope, is the most evolutionarily advanced brachiopod life cycle and appeared in the early Silurian. We suggest criteria for determining the type of life cycle based on the structure of the first-formed shell of brachiopods. Finally, we consider hypothetical scenarios of life cycles of fossil brachiopods, including true planktotrophic larvae in the Cambrian linguliforms.

Using a selection of molecular biomarkers, we evaluated responses in freshwater mussels (Anodonta anatina) exposed to effluent from an industrial wastewater treatment facility. The aims of this work were to (1) assess biomarkers of general toxicity under sublethal exposure to an anthropogenic mixture of chemicals, represented by an arbitrary effluent, and (2) evaluate the potential of A. anatina as a bioindicator of pollution. Adult mussels (n = in total 32; 24 males and 8 females) were exposed (96 h) in the laboratory to a fixed dilution of effluent or to a control treatment of standardized freshwater. Metal concentrations were in general higher in the effluent, by an order of magnitude or more, compared to the control. Toxic unit estimates were used as proxies of chemical stress, and Cu, Ni, and Zn were identified as potential major contributors (Cu> Ni > Zn). Six transcriptional (cat, gst, hsp70, hsp90, mt, sod) and two biochemical (AChE, GST) biomarkers were analyzed in two tissues, gills, and digestive glands. Out of the 16 responses (eight biomarkers × two tissues), 14 effect sizes were small (within ± 28 % of control) and differences non-significant (p > 0.05). Results did however show that (1) AChE activity increased by 40% in gills of exposed mussels compared to control, (2) hsp90 expression was 100% higher in exposed female gills compared to control, and (3) three marker signals (AChE in both tissues, and hsp70 in gills) differed between sexes, independent of treatment. Results highlight a need for further investigation of molecular biomarker variability and robustness in A. anatina.

Although the morphology of the brachiopod tentacle organ, the lophophore, is diverse, the organization of tentacles has traditionally been thought to be similar among brachiopods. We report here, however, that the structure of the tentacle muscles differs among brachiopod species representing three subphyla: Lingula anatina (Linguliformea: Linguloidea), Pelagodiscus atlanticus (Linguliformea: Discinoidea), Novocrania anomala (Craniiformea), and Coptothyris grayi (Rhynchonelliformea). Although the tentacle muscles in all four species are formed by myoepithelial cells with thick myofilaments of different diameters, three types of tentacle organization were detected. The tentacles of the first type occur in P. atlanticus, C. grayi, and in all rhynchonelliforms studied before. These tentacles have a well-developed frontal muscle and a small abfrontal muscle, which may reflect the ancestral organization of tentacles of all brachiopods. This type of tentacle has presumably been modified in other brachiopods due to changes in life style. Tentacles of the second type occur in the burrowing species L. anatina and are characterized by the presence of equally developed smooth frontal and abfrontal muscles. Tentacles of the third type occur in N. anomala and are characterized by the presence of only well-developed frontal muscles; the abfrontal muscles are reduced due to the specific position of tentacles during filtration and to the presence of numerous peritoneal neurites on the abfrontal side of the tentacles. Tentacles of the first type are also present in phoronids and bryozoans, and may be ancestral for all lophophorates.

Three new species of Rhyacophila (Trichoptera: Rhyacophilidae) from Japan are described. Among them, R. hattorii n. sp. and R. kobayashii n. sp. are assigned to the Rhyacophila sibirica Group. Another new species, R. kuranishii n. sp. is assigned to the Rhyacophila anatina Group. The figures of “R. yukii” by Schmid (1970) are actually of R. hattorii, not R. yukii Tsuda 1942. We describe these three new species, redescribe R. yukii, and discuss the diversity of this genus.

Bivalve shells can persist over a geological time, acting as important physical resources to the associated fauna. However, few studies have investigated their relevance as persistent long-term ecological attributes to the ecosystem. As such, it is relevant to investigate the shell decays in riverine systems subjected to different environmental conditions. Towards this end, shells of four bivalve species (Anodonta anatina, Corbicula fluminea, Potomida littoralis and Unio delphinus) were made available individually and in clusters of different sizes. The effects of river flow and seasonality were assessed by recording the decay rates of shells in lentic and lotic habitats throughout the year. Our results evidenced that the decays varied among species and depend on shell size, water flow and season. Thin shelled species (A. anatina and U. delphinus) showed the highest mean percentage of decay per month, 3.17% (lotic) and 2.77% (lotic), respectively, and thick shelled species (C. fluminea and P. littoralis) the lowest, 2.02% (lotic) and 1.83% (lotic), respectively. Size was a relevant variable explaining decays, with the smallest shells presenting the highest values, 1.2–2.0 times higher compared to the other size classes. Also, robustness showed to be the most relevant feature explaining the decays in thick shelled species. River flow was also a relevant descriptor of the decays, with higher decays observed in the lotic compared to the lentic habitats. Furthermore, lower decays were observed mainly during summer (lentic site), and autumn (lotic site) associated to the burial effect of leaves. In summary, shells of the native species A. anatina and U. delphinus are expected to persist and contribute less as habitat engineering species, than shells of the native P. littoralis and invasive C. fluminea species. This is especially valid to lotic habitats where the decays were up to 2.13 times higher than in lentic habitats., This study was supported by the FCT (Foundation for Science and Technology, Portugal) strategic fund UID/Multi/04423/2019.

The worldwide extinction of species especially affects freshwater ecosystems. Even widespread species like the European freshwater duck mussel Anodonta anatina face population declines in many countries and regions. Due to an obligate parasitic phase in its life cycle, knowledge on host fish use is essential for effective conservation of A. anatina. Therefore, in this study host suitability of ten different fish species (native and invasive to Europe) from four different fish families was tested by simultaneously infesting them with the glochidia of A. anatina. Nine out of ten fish species were identified as suitable hosts, but infestation rates, duration of metamorphosis phase as well as duration and rate of juvenile mussel excystment differed significantly between all host species. The bitterling (Rhodeus amarus) was the only fish species with no juvenile mussel excystment. Surprisingly, one of the tested invasive fish (Ctenopharyngodon idella) turned out to be the second best host for the larvae of A. anatina, suggesting that the general assumption that non-native fishes would be a threat to native mussel populations no longer holds true. Compared to the second native Anodonta species in Europe (Anodonta cygnea), this study revealed that A. anatina had higher infestation rates and rates of juvenile mussels excystment as well as a different host compatibility than A. cygnea. These findings illustrate that species-specific assessments of host suitability form an urgent basis for evidence-based conservation and restoration of freshwater mussel populations and the ecosystem services they provide.

Freshwater mussels (Bivalvia: Unionoida) play an important role in freshwater habitats as ecosystem engineers of the water environment. Duck mussel Anodonta anatina is widely distributed throughout Europe, Siberia, and Western and Central Asia, which makes it a convenient object for biogeographic studies. In this study, we analyzed the divergence of A. anatina populations and discovered a separate genetic lineage distributed in rivers of the Azov Sea basin. This was confirmed by the high genetic distances between this group and previously defined populations, and by the position of this clade in the Bayesian phylogeny calibrated by an external substitution rate. Based on our approximate Bayesian computation (ABC) analysis, biogeographic scenarios of A. anatina dispersal in Europe and Northern, Western, and Central Asia over the Neogene&ndash, Quaternary were simulated. The haplogroup&rsquo, s isolation in the rivers of the Azov Sea basin most likely occurred in the Late Pliocene that was probably facilitated by rearrangement of freshwater basins boundaries in the Ponto-Caspian Region. Population genetic indices show the stability of this group, which allowed it to exist in the river basins of the region for a long time. The discovery of a long-term refugium in the rivers of the Azov Sea led to a better understanding of freshwater fauna evolution in the Neogene&ndash, Quaternary and highlighted the importance of conservation of these freshwater animals in the region as a source of unique genetic diversity.

Molecular biomarkers, like gene transcripts or enzyme activities, are potentially powerful tools for early warning assessment of pollution. However, a thorough understanding of response and baseline variation is required to distinguish actual effects from pollution. Here, we assess the freshwater mussel Anodonta anatina as a biomarker model species for freshwater ecosystems, by testing responses of six transcriptional (cat, gst, hsp70, hsp90, mt, and sod) and two biochemical (AChE and GST) biomarkers to environmentally relevant Cu water concentrations. Mussels (n = 20), collected from a stream free from point source pollution, were exposed in the laboratory, for 96 h, to Cu treatments (2 fold-change ≤ 0.80 and Cohen’s f ≤ 0.69, respectively), and no significant treatment effects were observed. In contrast, four out of eight biomarkers (cat, gst, hsp70, and GST) showed a significant sex:tissue interaction, and additionally one (sod) showed significant overall effects from sex. Specifically, three markers in gills (cat, mt, GST) and one in digestive gland (AChE) displayed significant sex differences, independent of treatment. Results suggest that sex or tissue effects might obscure low-magnitude biomarker responses and potential early warnings. Thus, variation in biomarker baselines and response patterns needs to be further addressed for the future use of A. anatina as a biomarker model species.

The Mercuria Boeters, 1971 species living in the coastal zones of France are reviewed. In the Atlantic zone the genus Mercuria comprises four species: M. anatina (Poiret, 1801), M. baudoniana (Gassies, 1859), M. bayonnensis (Locard, 1894) and M. sarahae (Paladilhe, 1869); in the Mediterranean zone we discriminate three species: M. meridionalis (Risso, 1826), M. similis (Draparnaud, 1805), and M. corsensis n. sp. Mercuria sarahae is represented by two subspecies, M. s. sarahae and M. s. vindilica (Paladilhe, 1870). Mercuria corsensis n. sp., a close sister species to the Sardinian M. zopissa (Paulucci, 1882) lives only in the extreme South of Corsica. Amnicola emiliana Paladilhe, 1869, does not belong to the genus Mercuria but must be attributed to Pseudamnicola Paulucci, 1878. Lectotypes for Bythinia [sic] bayonnensis Locard, 1894, Bythinia [sic] baudoniana Gassies, 1859, Amnicola lanceolata Paladilhe, 1869, Amnicola sarahae Paladilhe, 1869, Amnicola vindilica Paladilhe, 1870 and Bithynia meridio...

The organization of the coelomic system and the ultrastructure of the coelomic lining are used in phylogenetic analysis to establish the relationships between major taxa. Investigation of the anatomy and ultrastructure of the coelomic system in brachiopods, which are poorly studied, can provide answers to fundamental questions about the evolution of the coelom in coelomic bilaterians. In the current study, the organization of the coelom of the lophophore in the brachiopod Lingula anatina was investigated using semithin sectioning, 3D reconstruction, and transmission electron microscopy. The lophophore of L. anatina contains two main compartments: the preoral coelom and the lophophoral coelom. The lining of the preoral coelom consists of ciliated cells. The lophophoral coelom is subdivided into paired coelomic sacs: the large and small sinuses (= canals). The lining of the lophophoral coelom varies in structure and includes monociliate myoepithelium, alternating epithelial and myoepithelial cells, specialized peritoneum and muscle cells, and podocyte-like cells. Connections between cells of the coelomic lining are provided by adherens junctions, tight-like junctions, septate junctions, adhesive junctions, and direct cytoplasmic bridges. The structure of the coelomic lining varies greatly in both of the main stems of the Bilateria, that is, in the Protostomia and Deuterostomia. Because of this great variety, the structure of the coelomic lining cannot by itself be used in phylogenetic analysis. At the same time, the ciliated myoepithelium can be considered as the ancestral type of coelomic lining. The many different kinds of junctions between cells of the coelomic lining may help coordinate the functioning of epithelial cells and muscle cells.

The common duck mussel Anodonta anatina can live in sympatry with—and use the same host, brown trout (Salmo trutta)—as the endangered freshwater pearl mussel Margaritifera margaritifera. Since the glochidia release of A. anatina takes place seasonally earlier than that of M. margaritifera, brown trout can be sequentially exposed first to A. anatina and then to M. margaritifera. Cross-immunity, an immune reaction induced in fish host against glochidia after the infection with glochidia of another mussel species, is possible. Thus, it was studied experimentally if brown trout can be cross immunized against M. margaritifera by earlier infection with A. anatina. In addition, the hypothesis that consecutive exposures of same glochidial species in different years in the same host may create acquired immunity was tested in brown trout against M. margaritifera. Furthermore, the dose dependence of acquired immunity against M. margaritifera glochidia in the Atlantic salmon (S. salar) was also studied. Cross-immunity was not found; suggesting that occurrence of A. anatina does not pose a threat to M. margaritifera. Instead, acquired immunity and its dose dependence were evident, emphasizing the significance of availability of 0+ age group immunologically naive Atlantic salmon/brown trout for efficient conservation of M. margaritifera.

Four new species of genus Rhyacophila are described and illustrated from Thailand and Myanmar, Southeast Asia. Rhyacophila longicaudata sp. n. is in the R. nigrocephala Group; the very long basal segment of each inferior appendage distinguishes it from other related species. Rhyacophila aksornkoaei sp. n. and R. limsakuli sp. n. are in the R. anatina Group: they can be differentiated from other species of the group by the brush-like parameres and presence of a ventral process of the aedeagus in R. aksornkoaei sp. n., and by the rectangular apical segment of each inferior appendage and the hooked parameres in R. limsakuli sp. n.. Rhyacophila kengtungensis is in the R. yishepa Group and is characterized by the subtriangular shape of the preanal appendages in dorsal view and by the very large dorsal appendages of the phallic apparatus.

The living species included in the family Anatinellidae Deshayes, 1853 distributed along the American continent are mentioned in this chapter. All American living species belong to the subfamily Kymatoxinae Stenzel and Krause, 1957. Two genera are recognized. The genus Anatina Schumacher, 1817 groups the species A. anatina (Spengler, 1802) and A. cyprinus (Wood, 1828). And the genus Raeta Gray, 1853 includes R. (Raeta) plicatella (Lamarck, 1818) and R. (Raeta) undulata (Gould, 1851).

The genus Eulepida Kolbe, 1894 presently contains 22 species (Lacroix 2017, Sehnal 2018) divided on the base of external and aedeagal morphology into three groups (see Lacroix 2010, 2013 for details). Group II is defined by the combination of the following characters: protibia bidentate; antennal club distinctly longer than antennal shaft; pygidium narrow, longer than wide, with a pronounced elongate terminal invagination; and parameres symmetrical, long, evenly curved in ventral aspect (Lacroix 2010). Until recently this group contained three species, E. anatina Brenske, 1896, E. tschindeana Péringuey, 1904 and E. werneri Lacroix, 2010, to which Lacroix & Montreuil (2017) added E. delgadoensis from Mozambique and Sehnal (2018) added E. mbala from Zambia. Shortly after the description of E. mbala I received large series of melolonthines from Zimbabwe and Mozambique, which included another markedly different group II species of Eulepida described below.

The genus Eulepida Kolbe, 1894 (Coleoptera: Scarabaeidae: Melolonthinae: Leucopholini) was established to accommodate 10 Afrotropical species, seven new and three previously placed in Lepidiota Kirby, 1828, Proagosternus Blanchard, 1851, and Tricholepis Hampson, 1891. Lacroix (2010) designated Leucopholis lepidota Klug, 1855 as the type species of the genus Eulepida. Currently the genus contains 20 species divided into three groups based on morphological characters (Lacroix 2010, 2013): species group I includes Eulepida lepidota (Klug, 1855), E. minor Moser, 1913, E. nitidicollis Kolbe, 1894, E. nyassica Kolbe, 1894, E. sinuatifrons (Fairmaire, 1887), and E. zambiensis Lacroix, 2010; species group II includes E. anatina Brenske, 1896, E. tschindeana Péringuey, 1904, and E. werneri Lacroix, 2010; and species group III includes E. baumanni Kolbe, 1894, E. flavovestita Moser, 1913, E. gracilipes Kolbe, 1894, E. kameruna (Frey, 1972), E. kenyensis Lacroix, 2010, E. mamboiae Brenske, 1896, E. manowensis Moser, 1913, E. mashona Arrow, 1902, E. montana Kolbe, 1894, E. reichei (Thomson, 1858), and E. savagei (Hope, 1842). Examination of material recently collected in Zambia revealed an undescribed species belonging to species group II (sensu Lacroix 2010). This group is defined by the combination of the following characters: protibia bidentate; antennal club distinctly longer than antennal shaft; pygidium narrow, longer than wide, with a pronounced elongate terminal invagination; and parameres symmetrical, long, evenly curved in ventral aspect (Lacroix 2010). The purpose of this paper is to describe one new species, to add new geographic records for some Eulepida species of group II, and to update the key for this group. New faunistic records are reported for Eulepida tschindeana and Eulepida werneri from Zimbabwe.

Pollution is believed to be an important factor modulating the competition between exotic invasive bivalves and their native competitors. Thus, the objective of the present study was to compare the sensitivity of the European native Anodonta anatina and the exotic invasive species Corbicula fluminea to mercury, a ubiquitous environmental contaminant of high concern. In laboratory acute bioassays, adult organisms of both species were exposed independently to mercury for 96 h (31–500 μg/L). The criteria indicative of toxicity were mortality and biomarkers of oxidative stress and damage, neurotoxicity, and energy production changes. Mercury induced mortality in A. anatina (72 h-LC10 and 72 h-LC50 of 14.0 μg/L and 49.6 μg/L, respectively) but not in C. fluminea. The ability of C. fluminea to maintaining the shell closed for considerable periods of time when exposed to high concentrations of mercury and the effective activation (up to 63 μg/L) of mechanisms against the oxidative stress caused by mercury may have contributed to its relatively low sensitivity. In the range of concentrations tested, mercury had no significant effects on the other parameters analysed in C. fluminea. Overall, the findings of the present study, suggest that in real scenarios of competition between C. fluminea and A. anatina populations, the presence of mercury may modulate the process, acting in favour of the exotic species because it is less sensitive to this environmental contaminant than the native bivalve. The results of the present study highlight the need of further investigation on the effects of mercury on the competition between exotic invasive species and their native competitors, especially the effects potentially induced by long-term exposure to low concentrations of this metal, the mechanisms involved in the tolerance to mercury-induced stress, and the potential post-exposure recovery of both exotic invasive and native bivalves. This knowledge is most important for environmental management and assessment of the risks associated with the consumption of bivalves by humans.

Unionoid freshwater mussels have a unique life cycle with a form of parental care where the larvae are developed and kept inside the gills until release, followed by an obligate parasitic stage on fish. The size and location of the marsupium have been used as important phylogenetic characters in unionoids and in Anodontini its location was described exclusively on the outer demibranchs. Two recent surveys in a lake in the North of Portugal revealed large anodontine mussels morphological identical to Anodonta anatina but with glochidia in both demibranchs and with an unusual large size. In order to establish the identity of these mussels, a barcoding approach was used and an anatomical description of the gills and glochidia was performed. These mussels were identified as A. anatina and presented an inner demibranch pair with tripartite tubes. The glochidial sizes were much higher than previously reported for the species reaching maximum (length × height) values of 566 × 552 μm. This species reveals a high ecological plasticity being able to change its size and anatomy to increase its fertility as well as infestation performance. J. Exp. Zool. 325A:52-56, 2016. © 2015 Wiley Periodicals, Inc.

Freshwater mussels of the family Unionidae are one of the most threatened groups worldwide and have suffered severe decline over recent decades. Although the freshwater duck mussel, Anodonta anatina (Linnaeus, 1758), is still widespread, this species has shown evidence of recent declines and is already protected in some European countries. Informed conservation efforts must take into account patterns in genetic diversity and phylogeography. In the present study, 20 newly developed polymorphic loci were described and tested in seven populations of A. anatina, belonging to three previously detected divergent mtDNA lineages. The genetic diversity patterns, within and among A. anatina populations, were evaluated to test their congruence with those lineages. A high genetic differentiation (FST) was found among all populations, with the exception of those in Central Europe (Germany) and the UK, which were not strongly structured. The present study confirms the division of the species into three evolutionarily significant units corresponding to the three previously detected mtDNA lineages, which should be managed independently. Furthermore, owing to the high differentiation among southern European populations, the establishment of distinct management units for the Guadalquivir, Guadiana and Douro populations in the Iberian Peninsula is also proposed. Copyright © 2015 John Wiley & Sons, Ltd.

The origin of the Bilateria and reconstruction of the last common bilaterian ancestor (LCA) are fundamental problems in zoology, including the question whether the LCA was a coelomic creature or not? Insight into the nature of the LCA might be obtained by investigating the coelomic system of poorly studied bilaterians. The Brachiopoda is a relict group of marine invertebrates whose anatomy has been seldom studied with modern methods. For most brachiopods, the coelomic system has been described as bipartite, i.e., as consisting of two parts: the lophophore coelom and trunk coelom. In the present report, a tripartite coelomic system is described for the first time in adult brachiopods, the linguliform Lingula anatina . In addition to a lophophoral and trunk coelom, L. anatina has a preoral coelom. The protocoel is located at the base of the epistome and has its own lining, which consists of non-muscular monociliated epithelial cells connected by desmosomes and tight junctions. Among brachiopods there are two types of the coelom: bipartite and tripartite. The same is known in phoronids and bryozoans (=ectoprocts). These three phyla – brachiopoda, phoronida, and bryozoa – are traditionally united into clade called lophophorata. An analysis of coelomic system organization revealed that the trimeric coelom is plesiomorphic for the lophophorates. The trimeric coelom is typical for the most of deuterostomes. The presence of the trimeric coelom in two main lineages of the bilateria allows to suggest that the LCA may have had a tripartite coelom and strongly specialized two the most anterior parts of the body – the prosome and the mesosome. This suggestion is consistent with published gene expression studies, in which Hox genes are never expressed in the two first segments of the body, whereas Otx genes are expressed in the most anterior segments of some bilaterians.

The presence of environmentally robust dispersive stages of intestinal protozoan parasites in waters represents an important public health threat since these pathogens have caused numerous outbreaks related to either drinking or recreational waters. The purpose of this study was to evaluate the presence of Cryptosporidium oocysts, Giardia and Blastocystis cysts, and microsporidian spores in mussels collected from municipal reservoir, Lake Malta (Poland, Europe). Two species of freshwater bivalves ( Anodonta anatina and Unio tumidus ) were tested for the enteropathogens. A direct wet smear and smears stained with chromotrope 2R, Ziehl–Neelsen and iron hematoxylin made from each pellet of the hemolymph, gills and gastrointestinal homogenates of mussels were examined microscopically. In the study the immunofluorescence antibody test kit MERIFLUOR Cryptosporidium/Giardia was also used for all bivalve samples. None of investigated parasites were found in U. tumidus . In A. anatina , Cryptosporidium oocysts and Blastocystis cysts were detected in 15.4 and 5.1% of mussel samples, respectively. The present results indicate contamination of Lake Malta with Cryptosporidium and Blastocystis , which is important from the point of view of public health threats because of different human uses of studied reservoir.

Earlier studies (1972–1987) on the occurrence of unionid bivalves in the eutrophicated Lake Mikolajskie (Masurian Lakeland, NE. Poland) were continued in 1992–2008. Of the five recorded species (Unio tumidus, U. pictorum, Anodonta cygnea, A. anatina, and Pseudanodonta complanata), A. cygnea and P. complanata disappeared by 1987, whereas U. pictorum was observed sporadically at that time, and the unionid occurrence zone was markedly reduced. Beginning in 1992, a pronounced increase in abundance of U. tumidus was observed, and since 2002–2003, a decline of the other two species. Since 2003 the maximal original vertical distribution of U. tumidus (down to ca. 5 m) was re-established. The size and age structure of its population changed markedly during the study. No individuals of shell length exceeding 55 mm and aged more than 5–6 years were recorded since 1987. Between 1972 and 1987 one-year-old individuals prevailed, whereas in the following years the age structure changed slowly, and in 2008 twoto four-yearold bivalves were most frequent. The potential effects of changes in trophy and the effects of other factors, e.g. decline of Dreissena polymorpha, on changes in the occurrence of Unionidae in Lake Mikolajskie are discussed.

The geographic population patterns of Lingula anatina across the Indo-West Pacific region are analyzed based on mitochondrial COI and nuclear EF-1α gene sequences. Compared with the remarkable morphological stasis, genetic evidence of extant Lingula species displays deep genetic divergence. Three distinct COI lineages were detected for L. anatina, one of which is from Qinhuangdao (Hebei, China, Bohai Sea), the other two from Beihai (Guangxi, China, Gulf of Tonkin). Individuals from South Japan have a very close relationship with one of the two COI lineages found in Beihai, which is also supported by EF-1α results, suggesting a relatively recent migration between South China Sea and East China Sea. Genetic distances between the three lineages of L. anatina are rather high (8.9%, 8.6%, and 2.7%), and those between L. anatina and L. adamsi is much higher (44.5%), compared to other marine invertebrates. Both tectonic evolution and the repeated Quaternary glaciations have contributed to the complex phylogeographic pattern found in these recent Lingula anatina populations.

Freshwater mussels have decreased dramatically in Iberia over the last decades. These animals are responsible for important ecosystem services such as recycling nutrients and improving water clarity. Under this view a better knowledge on the biological features of these animals is extremely important for future conservation and management actions. In this study the reproductive and gametogenic cycle of Anodonta anatina were studied during 2 years in one population as well as the sex ratio and hermaphroditism in six distinct populations, using standard histology. Gametogenesis was continuous in both sexes and germinal epithelium in early stages of development. Gametes were present throughout the reproductive cycle. Oogenesis and spermatogenesis occurred mainly between January and May. Larvae brooding occurred between September and March and main glochidia discharge occurred over a short period (2-3 weeks) in March. For the sex-ratio and hermaphroditism assessments a variable number of individuals were collected from several populations from lakes and rivers. Previous studies described A. anatina as mainly dioecious with only a few populations presenting occasional hermaphroditism. However, the present study indicates that A. anatina sexual behavior is influenced by environmental conditions, being mainly dioecious in rivers with increased hermaphroditism in standing waters. Although self-fertilization was not confirmed, additional studies with molecular characterization of larvae using fast evolving markers should be used in future studies to enlighten this process. Overall, this study indicates that for more efficient conservation actions and management plans, freshwater mussel reproductive biology should be studied at the population level mainly in the subfamily Anodontinae.

In this study, complete mitochondrial genome of the Lingula anatina (Lamark, 1801) from Korea has been sequenced and analysed, and compared with previous complete mitochondrial genome record from Japan. The mitogenome is 25,790 bp and composed of 13 protein-coding genes, two ribosomal RNA and 34 tRNA. In comparison with previous record, there are dramatically changes in structure between two records. Additionally, phylogenetic tree of L. anatina in Brachiopoda reconstructed due to 12 protein-coding genes of mitochondrial genome. The results showed that the Korean L. anatina positioned in Brachiopoda and the closest species is the L. anatina from the Japan. This study provides the second complete mitochondrial genome for the species.

An update of the inventory of alien marine species from the coastal and offshore waters of Greece is presented. Records were compiled based on the existing scientific and grey literature, including the HCMR database of Greek alien species (ELNAIS), technical reports, scientific congresses, academic dissertations, websites, and unpublished/personal observations. 47 species were added to the inventory, including 34 invertebrates, one vertebrate (fish), three plants, eight protozoa, and one cyanobacterium. With the new records, the inventory of alien marine species of Greece now includes a total of 237 species (33 macrophytes, 131 invertebrates, 42 vertebrates, two bacteria and 29 protozoans). Among these, the presence of the gastropod Hypselodoris infucata , the bivalves Dendrostrea frons and Septifer forskali and the chondrichthyan Rhizoprionodon acutus is reported here for the first time. Based on molecular analysis, the occurrence of Bulla arabica in Greek waters is confirmed, and the suggestion that previous records of Bulla ampulla in the Mediterranean should be considered as misidentification of B. arabica is further supported. The acclimitization status of earlier records was revised in the light of new data, and thus the fish Enchelycore anatina , Seriola fasciata and Tylerius spinosissimus , the red algae Hypnea cornuta and Sarconema scinaioides , the scyphomedusa Cassiopea andromeda , the cephalopod Sepioteuthis lessoniana , the nudibranch Chromodoris annulata and the bivalves Gastrochaena cymbium and Pseudochama corbieri were upgraded from casual records to established populations. The increased rate of introductions of warm water species confirms previous findings, which link the rate of introduction in the eastern Mediterranean to climate change.

We measured distribution patterns of hardness and elastic modulus by nanoindentation on shells of the rhynchonelliform brachiopod Mergerlia truncata and the linguliform brachiopods Discradisca stella and Lingula anatina. The rhynchonelliformea produce calcitic shells while the linguliformea produce chitinophosphatic shells. Dorsal and ventral valves, commissure and hinge of the calcitic shell of M. truncata show different nanohardness values (from 2.3 to 4.6 GPa) and E-modulus (from 52 to 76 GPa). The hardness of the biocalcite is always increased compared to inorganic calcite. We attribute the effects to different amounts of inter- and intracrystalline organic matrix. Profiles parallel to the radius of curvature of the valves cutting through the different layers of shell material surprisingly show quite uniform values of nanohardness and modulus of elasticity. Nanoindentation tests on the chitinophosphatic brachiopods D. stella and L. anatina reflect the hierarchical structure composed of laminae with varying degree of mineralization. As a result of the two-phase composite of biopolymer nanofibrils reinforced with Ca-phosphate nanoparticles, nanohardness, and E-modulus correlate almost linearly from (H=0.25 GPa, E=2.5 GPa) to (H=2.5 GPa, E=50 GPa). The mineral provides stiffness and hardness, the biopolymer provides flexibility; and the composite provides fracture toughness. Gradients in the degree of mineralization reduce potential stress concentrations at the interface between stiff mineralized and soft non-mineralized laminae. For the epibenthic chitinophosphatic D. stella the lamination is also present but less pronounced than for the infaunal L. anatina, and the overall distribution of material strength in the cross-sectional profile shows a maximum in the center and a decrease towards the inner and outer shell margins (modulus of elasticity from 30 to 12 GPa, hardness from 1.7 to 0.5 GPa). Accordingly, the two epibenthic forms, calcitic M. truncata and chitinophosphatic D. stella display fairly bulky (homogeneous) nanomechanical properties of their shell materials, while the burrowing infaunal L. anatina is distinctively laminated. The strongly mineralized laminae, which provide the strength to the shell, are also brittle, but keeping them as thin as possible, allows some bending flexibility. This flexibility is not required for the epibenthic life style.

We investigated reproductive rate in relation to oviposition site distribution and quality in the European bitterling, Rhodeus amarus, a freshwater fish that spawns on the gills of living unionid mussels. In a laboratory experiment male bitterling led females to groups of four mussels at a significantly higher rate than single mussels, irrespective of mussel species. Females spawned significantly more frequently on the gills of mussels in groups than on solitary mussels, and showed a preference for spawning on the gills of Unio pictorum in comparison with Anodonta anatina. In a field experiment the total number of eggs spawned on the gills of four mussels was significantly higher than that of single mussels, though the mean number of eggs per mussel was equivalent within species. There was a significant effect of species on the number of eggs spawned in mussels; U. pictorum and U. tumidus received more eggs than A. anatina and A. cygnea. We discuss these results in the context of mating system evolution.

Morphological phylogenetic analysis of the mactrid subfamilies Mactrinae and Kymatoxinae, plus the mactroidean family, Anatinellidae, indicate that the Kymatoxinae shares closer common ancestry with the Anatinellidae than with the Mactridae. Kymatoxinae is, therefore, reassigned from Mactridae to subfamily rank within Anatinellidae. The lack of a pallial sinus in Anatinella G. B. Sowerby I, 1833 suggests that its family was derived from anatomically plesiomophic members of Mactroidea with at best only weakly developed siphons. Fil: Signorelli, Javier Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Carter, Joseph G.. University of North Carolina; Estados Unidos

Freshwater flow regimes are particularly vulnerable to global climate change with changes to the volume and regime of water contributing to global declines in freshwater biodiversity. Droughts or floods can cause massive mortalities of freshwater bivalves, facilitating the accumulation of shells in the aquatic but also in adjacent terrestrial habitats. In order to fully understand the long term impact of these massive mortality events, it is important to assess how bivalve shells persist in the environment. Given that, the present study aimed at studying the shell decays of four different bivalve species (Anodonta anatina, Corbicula fluminea, Potomida littoralis and Unio delphinus) in aquatic (i.e. river) versus terrestrial (i.e. sand soil) habitats. Shell decay rates were significantly different among species and habitats. In the aquatic habitat the shell decay rates varied among species, with the native species A. anatina, which have the largest and thinnest shell, showing the highest decay rate. Alternatively, in the terrestrial habitatthe shell decay rates were more even among species and not related to a particular shell feature or morphology, with the native U. delphinus showing the fastest decay. The shell decay rates were 6 to 12 times higher in aquatic than in the terrestrial habitat. These results suggest that bivalve shells can persist for long periods of time on both habitats (but mainly in terrestrial), which may perhaps trigger significant changes on the ecosystem structure and functioning., This study was conducted in the scope of the project ECO-IAS: Ecosystem-level impacts of an invasive alien species, supported by FCT and COMPETE funds (contract: PTDC/AAC-AMB/116685/2010) and was also partially supported by the European Regional Development Fund (ERDF) through COMPETE funds (PEst-C/ MAR/LA0015/2011) and by FCT/MEC through Portuguese funds (PIDDAC - PEst-OE/BIA/UI4050/2014). Martina Ilarri is supported by a Post-doc grant from the FCT (SFRH/BPD/90088/2012)., info:eu-repo/semantics/publishedVersion

Evolutionary relationships among members of the Lophophorata remain unclear. Traditionally, the Lophophorata included three phyla: Brachiopoda, Bryozoa or Ectoprocta, and Phoronida. All species in these phyla have a lophophore, which is regarded as a homologous structure of the lophophorates. Because the organization of the nervous system has been traditionally used to establish relationships among groups of animals, information on the organization of the nervous system in the lophophore of phoronids, brachiopods, and bryozoans may help clarify relationships among the lophophorates. In the current study, the innervation of the lophophore of the inarticulate brachiopod Lingula anatina is investigated by modern methods. The lophophore of L. anatina contains three brachial nerves: the main, accessory, and lower brachial nerves. The main brachial nerve is located at the base of the dorsal side of the brachial fold and gives rise to the cross neurite bundles, which pass through the connective tissue and connect the main and accessory brachial nerves. Nerves emanating from the accessory brachial nerve account for most of the tentacle innervation and comprise the frontal, latero-frontal, and latero-abfrontal neurite bundles. The lower brachial nerve gives rise to the abfrontal neurite bundles of the outer tentacles. Comparative analysis revealed the presence of many similar features in the organization of the lophophore nervous system in phoronids, brachiopods, and bryozoans. The main brachial nerve of L. anatina is similar to the dorsal ganglion of phoronids and the cerebral ganglion of bryozoans. The accessory brachial nerve of L. anatina is similar to the minor nerve ring of phoronids and the circumoral nerve ring of bryozoans. All lophophorates have intertentacular neurite bundles, which innervate adjacent tentacles. The presence of similar nerve elements in the lophophore of phoronids, brachiopods, and bryozoans supports the homology of the lophophore and the monophyly of the lophophorates.

The fangtooth moray, Enchelycore anatina (Lowe, 1838), native to the eastern Atlantic Ocean but also known from eastern sections of the Mediterranean, is recorded for the fi rst time from Maltese coastal waters in the central Mediterranean. This record is the westernmost one within the Mediterranean and the observed E. anatina individual co-occurred with an individual of Muraena helena Linnaeus, 1758., peer-reviewed

The study was carried out on 9 species of freshwater bivalves (Dreissena polymorpha, D. bugensis, Unio crassus, U. pictorum, U. tumidus, Anodonta anatina, A. cygnea, A. woodiana, and Pseudanodonta complanata). The mitochondrial COI gene studied with PCR-RFLP and 6 restriction enzymes (ScrFI, Csp6I, BsiZI, EcoRI, BamHI and AluI) showed the absence of individual variability within each species studied. The genetic variability of the COI involved differences at the species, genus, and family level, depending on the restriction enzyme used. Four restriction enzymes (ScrFI, Csp6I, BsiZI and AluI) proved efficient in differentiating between D. polymorpha and D. bugensis as well as in identifying the three Unio species (Csp6I and AluI), U. crassus, and P. complanata (ScrFI and AluI). EcoRI and AluI made it possible to identify A. anatina and P. complanata. Two (for EcoRI), 3 (for Csp6I, BsiZI), 5 (for ScrFI) and 9 (for AluI) unique genotypes that occurred in a single species each were observed; the enzymes may therefore be regarded as species-specific markers. Only restriction enzyme AluI can differentiate between A. cygnea and A. woodiana.

The 1995–1998 studies on the unionid fauna of the Pilica catchment area (C Poland) included 103 localities in the river, tributaries, floodplain water bodies and the dam reservoir on the river. As a result of qualitative and quantitative sampling six unionid species (one represented by two forms) were recorded: Unio crassus Philipsson, U. tumidus Philipsson, U. pictorum (Linnaeus), Anodonta cygnea f. cygnea (Linnaeus), A. cygnea f. cellensis (Schroter), A. anatina (Linnaeus) and Pseudanodonta complanata (Rossmassler). Three of them: U. crassus, A. cygnea f. cygnea and P. complanata were found to be rare. Dominance structure and density of unionids are discussed. Spatial distribution and abundance are analysed on the background of such ecological factors as character of bottom sediments, bottom configuration, vegetation, distance from shore, seston content as well as physico-chemical, hydrobiological and bacteriological water pollution. Ecological preferences of each species are described. Selected populations are characterised with respect to their age structure. Species which were abundantly represented are characterised with respect to their metric characters and sexual dimorphism, as well as effect of zebra mussel on their growth and condition.

Genetic and Morphological Variability and Diff erentiation of Mussels (Bivavia, Unionidae, Anodontinae) in Ukraine. Mezhzherin S. V., Yanovich L. M., Zhalay Е. I., Vasilieva L. А., Pampura М. М. - Th e study of allozymes variation and sequence analysis of two mitochondrial genes supports the concept that there are four species of subfamily Anodontinae in the Eastern European fauna, three of them; Anodonta cygnea Linnaeus, 1758; A. anatina Linnaeus, 1758; Pseudanodonta complanata (Rossmassler, 1835) are indigenous and one is invasive (Sinanodonta woodiana Lea, 1834). Th is paper analyzes morphological diagnostic features of which some can be used in identification of these species.

The geographic population structure of sequence variations in a cox1 region of mitochondrial DNA and an intron region of the nuclear EF-1α gene has been assessed for the brachiopod Lingula anatina from three northern Pacific localities, namely Mutsu Bay (northern Japan), Ariake Sea (southern Japan), and Hong Kong. Both the mitochondrial and nuclear gene genealogies indicated a clear separation of the three populations with no shared haplotypes between them, and a sister group relationship between the Mutsu and Ariake haplotypes, each of which formed a monophyletic cluster. Statistical reanalysis of published allozyme data demonstrated genetic divergence between the Mutsu and Ariake populations and between Australian and Japanese populations. Morphometry of shell dimensions also discriminated between forms of the Mutsu and Ariake populations. Those observations gainsay the prevailing hypothesis that populations of L. anatina maintain panmixia and a single homogeneous gene pool over the entire Indo-West Pacific region, and suggest that each population of Mutsu, Ariake, and by inference also Hong Kong, could be seen as a separate species.

For low-energy organisms such as bivalves, the costs of thermal compensation of biological rates (synonymous with acclimation or acclimatization) may be higher than the benefits. We therefore conducted two experiments to examine the effect of seasonal temperature changes on behaviour and oxygen consumption. In the first experiment, we examined the effects of seasonal temperature changes on the freshwater bivalve Anodonta anatina, taking measurements each month for a year at the corresponding temperature for that time of year. There was no evidence for compensation of burrowing valve closure duration or frequency, or locomotory speed. In the second experiment, we compared A. anatina at summer and winter temperatures (24 and 4°C, respectively) and found no evidence for compensation of the burrowing rate, valve closure duration or frequency, or oxygen consumption rates during burrowing, immediately after valve closure or at rest. Within the experimental limits of this study, the evidence suggests that thermal compensation of biological rates is not a strategy employed by A. anatina. We argue that this is due to either a lack of evolutionary pressure to acclimatize, or evolutionary pressure to not acclimatize. Firstly, there is little incentive to increase metabolic rate to enhance predatory ability given that these are filter feeders. Secondly, maintained low energetic demand, enhanced at winter temperatures, is essential for predator avoidance, i.e. valve closure. Thus, we suggest that the costs of acclimatization outweigh the benefits in A. anatina.

Intramarsupial glochidia of Anodonta anatina (L.) and Pseudanodonta complanata (Rossmässler) were studied in southern Finland. Material staining positively with periodic acid – Schiff's reagent (PAS), neutral lipid reserves, and acid phosphatase activity have different distributions in the mantle of the two species. Moreover, the mucous covering of the mantle of the two glochidia behaves differently on critical-point drying. The presence of microvilli with alkaline phosphatase activity on the mantle surface and acid phosphatase activity in the mantle cells in both glochidia suggest that the mantle plays a role in nutrient uptake and digestion and possibly also in electrolyte uptake. The primordia of the stomach, digestive diverticula, and intestine, at least in A. anatina glochidia, contain neutral lipids and exhibit acid phosphatase activity: In A. anatina glochidia, a microvillous layer with alkaline phosphatase activity continues from the ventral walls of the lateral pits to the suspected kidney diverticula. In both glochidia, there may be three pairs of rudimentary ganglia, which do not stain with methylene blue. The eight ciliated sense organs of the glochidia are methylene blue- and PAS-positive and they exhibit succinate dehydrogenase and acid phosphatase activity. In each mantle lobe, the enveloping cell of the dorsal ciliary organ is interconnected with those of the ventral triad via a cellular fold or "tract," and the ciliated central cells of the organs send axons towards each other.

Shells of Lingula squamiformis from argillaceous sediments at three horizons within the Dinantian Series, exposed at three localities in Scotland, have been studied to determine chemico-structural changes resulting from fossilization. Biomineral structures are essentially the same as those of living Lingula anatina with apatitic granules aggregating into spherules, up to 60 nm in size, and larger spheroidal bodies as well as rods and rarer lath-like plates. These aggregates and the original organic constituents were secreted as stratiform successions in two distinct layers, as in Recent L. anatina . The outer, lithified part of the primary layer bears microstructural moulds of a totally degraded periostracum and was probably composed mainly of acidic glycosaminoglycans (GAGs); the inner part evidently contained a higher proportion of spherular apatite within the GAGs than in living species. The secondary layer consists of variably complete rhythmic sets of compact, rod and plate (virgose), and membranous laminae. Compact laminae are normally cleaved along degraded walls of GAGs whereas the original GAGs-filled spaces of virgose laminae are partly occupied by recrystallized apatitic sheets with kaolinite. The phosphatized membranous laminae probably contained more spherular apatite in life than present day Lingula . The shell is canaliculate with chambers and galleries well developed in the virgose laminae. There is a decrease in concentration of amino acids from the posterior to the anterior of the valves of living Lingula anatina and Glottidia pyramidata resulting from the proteinaceous coat of the apatitic spherules. A similar distribution of hydroxyproline occurs, indicative of collagen in the body platform of living lingulids. Nearly all organic constituents have been degraded in the Carboniferous valves but threads, about 50 nm thick, occasionally traverse spaces in virgose laminae and even form a network coated with spherular apatite, which resembles webs of collagens or actin found in living lingulids. Acidic and aliphatic amino acids were extracted from L. squamiformis valves from Calderwood and Kinghorn whereas the narrower range of amino acids from the heavily pyritized valves from Ardross confirmed differential degradation of organic material during the fossilization of penecontemporaneous samples. The fossilization of complete shells of L. squamiformis is not due exclusively to catastrophic burial as has been deemed necessary to preserve Recent Lingula intact. The living shells of Carboniferous species were more apatitic than those of Recent Lingula , especially in the anteriomedian sectors of the secondary layers.

The effect of different conditions of transfer (+1 °C with water, +20 °C with and without water) from the natural habitat and laboratory acclimation procedure (with and without bottom sediment) on the acid-base and electrolyte status of the freshwater uniomd mussel Anodonta anatina (L.) was studied. The shift in the acid-base status of A. anatina during the transfer was smaller at 1°C than at 20°C. The pd content of the haemolymph declined significantly under all three transfer conditions. Neither the transfer nor the laboratory acclimation affected haemolymph [Na*]. However, during transfer at 1°C the haemolyraph [Ca2*] did not change, whereas [K*] increased up to three fold. Haemolymph [Ca1*] increased when mussels were transferred at 20°C After a 17-day aquarium acclimation, the pOj of all the mussels kept in the sediment had returned to the field level and the transfer seemed to have had no effect on the pCH of the haemolymph. Conversely, in the groups kept without sediment, the pO} continuously remained above the field level. Whereas the [K*] of all the mussels declined to the field level, the haemolymph [Ca2*] remained elevated throughout the entire acclimation period of 17 days.

Freshwater mussels Anodanta anatina and Pseudanodonta complanata were exposed to (14C)-pentachlorophenol. The wet weight based bioconcentration factor (BCF = activity in animal per activity in water) at steady state varied from 80 to 120 for A. anatina and from 61 to 85 for P. complanata. The species did not differ significantly in their wet weight or lipid based BCFs but dry weight based values were significantly higher (40-50%) for A. anatina. The soft tissue dry weight and dry weight based condition index of A. anatina (Cl4 = soft tissue dry weight per shell length) differed significantly between natural mussel populations. In animals kept from 4 to 8 months in laboratory conditions, the soft tissue dry weight and glycogen content decreased more rapidly when mussels were maintained at 15 than at 5 degrees C. However, glycogen content in the digestive gland or adductor muscle did not differ in mussels maintained in the laboratory (5 degrees C) when compared to the natural population. The adductor muscle protein content differed between laboratory maintained animals and the natural population in Lake Höytiänen but there was no difference in the soft tissue lipid content. Trace metal concentrations and calcium in the soft tissue were in general higher in laboratory maintained mussels. In addition, laboratory maintenance affected the reproductive cycle of A. anatina.