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Arsenic is naturally found in the tissues of marine animals, usually as the non-toxic arsenical arsenobetaine, but exposure to elevated arsenic concentrations in the environment may alter the arsenic species distribution within tissues of the organism. This study examined the arsenic species in the tissues of the marine periwinkle (Littorina littorea) along an arsenic concentration gradient in the sediment. The arsenicals in L. littorea were examined using the complementary analytical methods high performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC–ICPMS) and X-ray absorption spectroscopy (XAS). Total arsenic concentrations in the periwinkle tissues ranged from 56 to 840mg·kg−1 dry weight (equivalent to 13 to 190mg·kg−1 wet weight). Inorganic arsenicals were found to be positively correlated with total arsenic concentrations (R2 =0.993) and reached 600mg·kg−1 dry weight, the highest reported to date in marine organisms. These high inorganic arsenic concentrations within this low trophic organism pose a potential toxicological risk to higher trophic consumers. [ABSTRACT FROM AUTHOR]

Hybrid zones of ecologically divergent populations are ideal systems to study the interaction between natural selection and gene flow during the initial stages of speciation. Here, we perform an amplified fragment length polymorphism ( AFLP) genome scan in parallel hybrid zones between divergent ecotypes of the marine snail Littorina saxatilis, which is considered a model case for the study of ecological speciation. Ridged-Banded ( RB) and Smooth-Unbanded ( SU) ecotypes are adapted to different shore levels and microhabitats, although they present a sympatric distribution at the mid-shore where they meet and mate (partially assortatively). We used shell morphology, outlier and nonoutlier AFLP loci from RB, SU and hybrid specimens captured in sympatry to determine the level of phenotypic and genetic introgression. We found different levels of introgression at parallel hybrid zones and nonoutlier loci showed more gene flow with greater phenotypic introgression. These results were independent from the phylogeography of the studied populations, but not from the local ecological conditions. Genetic variation at outlier loci was highly correlated with phenotypic variation. In addition, we used the relationship between genetic and phenotypic variation to estimate the heritability of morphological traits and to identify potential Quantitative Trait Loci to be confirmed in future crosses. These results suggest that ecology (exogenous selection) plays an important role in this hybrid zone. Thus, ecologically based divergent natural selection is responsible, simultaneously, for both ecotype divergence and hybridization. On the other hand, genetic introgression occurs only at neutral loci (nonoutliers). In the future, genome-wide studies and controlled crosses would give more valuable information about this process of speciation in the face of gene flow. [ABSTRACT FROM AUTHOR]

Anti-herbivory defenses support persistence of seaweeds. Little is known, however, about temporal dynamics in the induction of grazer-deterrent seaweed traits. In two induction experiments, consumption rates of the periwinkle Littorina obtusata (L.) on the brown seaweed Ascophyllum nodosum (L.) Le Jolis were measured in 3-d intervals. Changes in palatability of directly grazed A. nodosum were tested every 3 d with feeding assays using fresh and reconstituted seaweed pieces. Likewise, assays with fresh A. nodosum assessed changes in seaweed palatability in response to water-borne cues from nearby grazed conspecifics. Consumption rates of L. obtusata varied significantly during the 27-d induction phase of each experiment. Direct grazing by L. obtusata lowered palatability of fresh and reconstituted A. nodosum pieces to conspecific grazers after 15 d as well as after 6 and 12 d, respectively. After 12, 18, and 24 d, fresh A. nodosum located downstream of L. obtusata-grazed conspecifics was significantly less palatable than A. nodosum located downstream of ungrazed conspecifics. Changes in L. obtusata consumption rates and A. nodosum palatability during both induction experiments suggest temporal variation of grazer-deterrent responses, which may complicate experimental detection of inducible anti-herbivory defenses. [ABSTRACT FROM AUTHOR]

Anti-herbivory defenses support persistence of seaweeds. Little is known, however, about temporal dynamics in the induction of grazer-deterrent seaweed traits. In two induction experiments, consumption rates of the periwinkle Littorina obtusata (L.) on the brown seaweed Ascophyllum nodosum (L.) Le Jolis were measured in 3-d intervals. Changes in palatability of directly grazed A. nodosum were tested every 3 d with feeding assays using fresh and reconstituted seaweed pieces. Likewise, assays with fresh A. nodosum assessed changes in seaweed palatability in response to water-borne cues from nearby grazed conspecifics. Consumption rates of L. obtusata varied significantly during the 27-d induction phase of each experiment. Direct grazing by L. obtusata lowered palatability of fresh and reconstituted A. nodosum pieces to conspecific grazers after 15 d as well as after 6 and 12 d, respectively. After 12, 18, and 24 d, fresh A. nodosum located downstream of L. obtusata-grazed conspecifics was significantly less palatable than A. nodosum located downstream of ungrazed conspecifics. Changes in L. obtusata consumption rates and A. nodosum palatability during both induction experiments suggest temporal variation of grazer-deterrent responses, which may complicate experimental detection of inducible anti-herbivory defenses. [ABSTRACT FROM AUTHOR]

An extensive community of organisms inhabits the common periwinkle, Littorina littorea (L., 1758), along the wave-swept rocky shores of Canada's East coast. This community, which includes both facultative and obligate endosymbionts, comprises a diverse array of species from seven animal phyla, including Annelida, Arthropoda, Gnathostomulida, Nematoda, Nemertea, and Platyhelminthes, as well as ciliates and algae. The presence of larger numbers of endosymbionts was found to correlate with specific shell characteristics of the snail host, including a wider aperture and columella, suggesting that these individuals have a larger mantle cavity relative to snails housing a small community of endosymbionts. Snails with large communities of endosymbionts were usually encrusted with coralline algae and often had trematode infections. Although L. littorea has been extensively studied since the last century, the existence of this community of organisms has passed unnoticed. The large diversity of organisms in this community suggests that these snails may provide refugia for a wide range of smaller taxa. [ABSTRACT FROM AUTHOR]

Species occupying different ecological niches may evolve ecotypes that differ in size as a result of divergent selection on this trait. Size differences may affect mate preference and cause deviations from random mating. Several marine snails of the genus Littorina have ecotypes that differ in size and earlier studies have shown strong assortative mating between differently sized ecotypes in at least one of these species, L. saxatilis. Here we studied male mate choice in two ecotypes of the congeneric L. fabalis that differ in size. We found mating to be nonrandom, because males of the large ecotype followed the mucus trails and copulated with females of their own large ecotype more than with females of the smaller ecotype. Males of the smaller ecotype showed no strong preference, but tended to copulate more with females of the large ecotype than with their own females. Further experiments using the small ecotype showed that mate choice was size-based, with a general preference of the males to mate large females. It seems likely that the partial reproductive barrier that we describe somewhat impedes gene flow between the two ecotypes of L. fabalis, a result that corroborates earlier observations of a weak, but significant, gene-flow barrier across zones where the two ecotypes overlap and hybridize. [ABSTRACT FROM AUTHOR]

There are few examples of host population regulation by macroparasites in stable communities; however, strong impact of parasites on the host individual is obvious in many cases (for example increased mortality, a reduction in fecundity up to the complete castration). Associations between the host populations (periwinkle Littorina obtusata) and prevalence of trematodes was investigated using long-term data (1982-1997) of two L. obtusata populations in the White Sea, northwest Russia. We hypothesized that high prevalence of trematodes will reduce future host population density, and increase mortality. Using a general linear model, we found a significant negative correlation between host population density and the prevalence of the most abundant parasite, Microphallus piriformes in the previous year. We found no correlation between snail reproduction and the prevalence, but observed a significant reduction in middle-aged mollusk abundance which was associated with high prevalence. This indicates the importance of parasite-induced mortality for the dynamics of the host population. There was an association between trematode infection and L. obtusata populations that influence their distribution within littoral zone. The 'source' population, located in the lower section of the macrophyte zone, appears to be self-sustaining, controlling the whole population recruitment and dynamics. [ABSTRACT FROM AUTHOR]

Abstract: Although geographic variation in algal–herbivore interactions should be common, our appreciation of such variation remains incomplete. For example, feeding choice assays examining variation in palatability of algae typically compare multiple algal species or genera from a single location or a single alga from multiple locations. Unfortunately, most studies have not compared the interaction of herbivores with multiple algae from multiple locations, thus tests of variation of relative palatability are lacking. To examine spatial variation in algal palatability we determined the feeding preferences of the periwinkle snail Littorina littorea when offered multiple algal genera at the same time from two regions in choice assays. Multi-choice experiments were repeated throughout the year to examine temporal variation in feeding preferences. Consistent with previous studies, L. littorea preferred to feed on ephemeral algae compared to perennial species. Importantly, the relative palatability of the two ephemeral genera, Ulva and Porphyra, varied greatly between regions and seasons. Under certain conditions, Ulva only represented 24% of consumed algal wet mass in choice assays, while under other conditions, Ulva was eaten almost exclusively. Preferences for Ulva or Porphyra were unrelated to differences in morphology. Variation in the relative palatability of algae could influence consumer behavior leading to shifts in algal communities across broad geographic scales. [Copyright &y& Elsevier]

Early to late Holocene sediments from core F80, Fårö Deep, Baltic Sea, are investigated for their palynomorph composition and dinoflagellate cyst record to map variations in sea-surface-water salinity and palaeoproductivity during the past 6000 years. The F80 palynomorph assemblages are subdivided into four Assemblage Zones ( AZs) named A to D. The transition from the stratigraphically oldest AZ A to B reflects a marked increase in palaeoproductivity and a gradual increase in surface-water salinity over the ∼1500 years between the Initial Littorina (former Mastogloia Sea Stage) and Littorina Sea Stage. A period with maximum sea-surface salinity is recorded within the overlying AZ C from 7200 to 5200 cal. a BP, where the process length of Operculodinium centrocarpum indicates that average salinities were probably the highest (∼15-17 versus 7.5 psu today) since the last glaciation. The change from AZ C to D correlates with a shift from laminated to non-laminated sediments, and the dinoflagellate cyst assemblages suggest that the surface- and the deep-water environment altered from c. 5250 cal. a BP, with less productivity in the surface water and more oxygenated conditions in the deep water. Here we demonstrate that past regional changes in surface salinity, primary productivity and deep-water oxygenation status in the Baltic Sea can be traced by mapping overall palynomorph composition, dinoflagellate cyst assemblages and variations in the process length of O. centrocarpum in relation to periods of laminated/non-laminated sedimentation and proportion of organic-matter in the sediments. An understanding of past productivity changes is particularly important to better understand present-day environmental changes within the Baltic Sea region. [ABSTRACT FROM AUTHOR]

Abstract: Marine sediment cores from the Pomeranian Bay and Arkona Basin were analysed in terms of geochemical composition, diatom assemblages and radiocarbon dating, in order to evaluate the characteristics of the Littorina transgression, on the environment of the south Baltic basin. The data show that this transgression had a strong influence on the evolution of the hydrographic system, which has changed substantially from the Ancylus Lake to the Littorina Sea. The beginning of the period of the Littorina Sea was estimated at 7400–8000cal BP, but culmination of the marine ingression appeared a few hundred years afterwards in the western cores from the Arkona Basin, and almost 2000years later in the eastern cores from the Pomeranian Bay. In this study we present a new look at the evolution of the Baltic Sea during the Holocene, based on the statistical analysis of relations between geochemical composition and diatom occurrence. Canonical correlation analysis clearly describes Ancylus and Littorina environments. The Ancylus Lake was characterised as a cold lacustrine environment with poor nutrient availability and high mineral matter inflow, probably from adjacent rivers, while the Littorina Sea environment was much warmer, with a high inflow of nutrients that favoured biogenic production. [Copyright &y& Elsevier]

The prevalence of parasite infections in Littorina littorea (Common Peri-winkle) was examined at 16 rocky intertidal sites along the New Hampshire coastline over three summers (2006 to 2008). We sampled over a relatively small spatial scale (21 kin) and expected that the prevalence of infections in L. littorea would be similar between sites over this sampling area. In total, 1983 snails were collected from areas at mean low water during spring tides. Snail size (ram), gender, and type of parasitic infection were noted for all snails. Eleven percent of snails collected were infected with rediae and cercariae of the trematodes Cryptocotyle lingua or Cercaria parvicaudata; one snail had a double infection of both trematodes. The prevalence of infection at sites ranged from 1.9% to 30.1%. At all sites, female snails outnumbered male snails, and a greater proportion of females were infected than males. Large snails were more likely to be infected with trematodes at 3 sites, while a higher level of infection was found in small snails at 1 site. Snails at wave-protected sites were more likely to be infected than snails at wave-exposed sites. No relationship was found between the number of gulls at a site and the prevalence of infection. Although temporal variation in levels of prevalence in parasitic infections may explain some of our site-to-site differences, our data show large spatial variation of parasite prevalence in L. littorea over a minimum distance of 0.5 km and provide a foundation to test hypotheses concerning the susceptibility of female and immature (small) snails to infection. [ABSTRACT FROM AUTHOR]

Despite an exponential rise in anthropogenically-mediated transfers of non-indigenous species during the last 150 years, several coastal anthropogenic activities remain unregulated under current legislation frameworks. This study investigates the potential role of commercial periwinkle (Littorina littorea) harvesting as an unregulated facilitator of both small- and large-scale geographic range expansion of an invasive oyster epibiont (Ostrea chilensis) within the Menai Strait (North Wales, UK) and beyond. The frequency of oyster-fouled periwinkles was greatest in areas of high adult oyster abundance and restricted to large, market-sized periwinkles (>20 mm) inhabiting the low shore. Active efforts by commercial collectors to reject oyster-fouled periwinkles were found to be inadequate, with oysters of all sizes observed within collected hauls. Whilst the survival of fouled and unfouled periwinkles was comparable under post-collection refrigerated conditions, a significant decrease in both mobility and flesh content was associated with the presence of oyster epibionts. Survival of all but the smallest oyster epibionts under post-collection refrigerated conditions enhances the possibility of accidental non-indigenous oyster transfers. Better interventions during both initial visual inspection and post-griddling stages are recommended, as well as the development of techniques that kill off all non-indigenous epibionts, whilst leaving the freshness and marketability of the periwinkles uncompromised. [ABSTRACT FROM AUTHOR]

Previously we isolated the major alginate lyase isozyme LbAly35 from a marine snail Littorina brevicula and showed that this enzyme was significantly heat stable in a broad pH range compared with other molluscan alginate lyases (Hata et al., Fish Sci 75:755-763, ). LbAly35 showed practically no similarity to other molluscan alginate lyases in the N-terminal amino-acid sequence of 20 residues and no cross-reactivity with anti-abalone alginate lyase antiserum. These led us to consider that the primary structure of LbAly35 is considerably deviated from other molluscan enzymes. Thus, in the present study, we first compared the thermal stability of LbAly35 with an abalone alginate lyase, HdAly, and found that the first order inactivation rate constants for LbAly35 at 40 and 45 °C were 1/20 and 1/45 of those for HdAly, respectively. Then, we cloned cDNAs encoding LbAly35 and characterized its deduced amino-acid sequence comparing with those of other molluscan alginate lyases. The cDNAs were amplified by polymerase chain reaction (PCR) and 5′- and 3′-RACE PCRs from the L. brevicula hepatopancreas cDNA using degenerated primers synthesized on the basis of partial amino-acid sequences of LbAly35. The cDNA covering the entire translational region of LbAly35 comprised 1,093 bp and encoded an amino-acid sequence of 296 residues. The amino-acid sequence consisted of an initiation methionine, a putative signal peptide for secretion (22 residues), a propeptide-like region (10 residues), and a mature LbAly35 domain of 263 residues. Although the N-terminal region of LbAly35 was significantly deviated from those of other molluscan alginate lyases, the catalytic domain of LbAly35 showed ~45 % identity to other molluscan enzymes which had been classified under polysaccharide-lyase-family-14 (PL-14). In addition, the amino-acid residues crucially important for the catalytic actions of PL-14 enzymes were also conserved in LbAly35. Accordingly, LbAly35 was regarded as a member of PL-14 as other molluscan alginate lyases despite the significant deviation of its N-terminal region. [ABSTRACT FROM AUTHOR]

The molluscan cardiovascular system typically incorporates a transient extracardiac structure, the larval heart, early in development, but the functional importance of this structure is unclear. We documented the ontogeny and regulatory ability of the larval heart In relation to two other circulatory structures, the true heart and the velum, in the intertidal gastropod Littorina obtusata. There was a mismatch between the appearance of the larval heart and the velum. Velar lobes appeared early in development (day 4), but the larval heart did not begin beating until day 13. The beating of the larval heart reached a maximum on day 17 and then decreased until the structure itself disappeared (day 24). The true heart began to beat on day 17. Its rate of beating increased as that of the larval heart decreased, possibly suggesting a gradual shift from a larval heart-driven to a true heart-driven circulation. The true heart was not sensitive to acutely declining P02 shortly after it began to beat, but increased in activity in response to acutely declining P02 by day 21. Larval heart responses were similar to those of the true heart, with early insensitivity to declining P02 (day13) followed by a response by day15. Increased velum-driven rotational activity under acutely declining Pqj was greatest in early developmental stages. Together, these findings point to cardiovascular function in L. obtusata larvae being the result of a complex interaction between velum, larval and true heart activities, with the functions of the three structures coinciding but their relative importance changing throughout larval development. [ABSTRACT FROM AUTHOR]

Energy metabolism and phosphorus excretion were studied in Littorina littorea and L. saxatilis snails from the White Sea. Some elemental components of the body were determined quantitatively, and the rates of oxygen consumption and phosphorus excretion were estimated. All parameters were calculated relative to dry body weight (mg). Daily expenditures for energy metabolism in Littorina spp. averaged 3.6 ± 1.1%, and those for phosphorus metabolism were approximately four times lower (about 1%), with the total phosphorus content averaging 0.8% dry body weight. The atomic ratio of consumed oxygen to excreted phosphorus for both species averaged O: P = 1164 ± 140. [ABSTRACT FROM AUTHOR]

Abstract: The Baltic Ice Lake, Yoldia Sea, Ancylus Lake and Littorina Sea stages of regression and transgression controlled the history of the Baltic Sea since the last glacial period. Many details regarding their development remain unknown, including the question whether the regression of the Ancylus Lake (between 10,700 and 10,200calyr BP) took place west of the Darss Sill, or elsewhere. This study addresses whether a drowned river system in Fehmarn Belt (SW Baltic Sea) can be related to the drainage of the Ancylus Lake. The river channel is cut into glacial till in the western part of Fehmarn Belt. Here, the channel reaches an incision depth of up to 12m at a base level of 40m b.s.l. (below sea level). Near Mecklenburg Bay, the buried channel is incised down to 60m b.s.l. and widens rapidly from several hundred meters to more than 1km, fading towards east. It was mainly shaped as part of a glacial meltwater system at a maximum water level of 30m b.s.l., and is therefore not related to the Ancylus Lake drainage. During the lowstand of the Baltic Ice Lake, local shallow water bodies covered the study area. A previously reported westward directed drainage of a lake in the eastern Fehmarn Belt could be restricted to a time interval between the highstand of the Ancylus Lake and prior to the Littorina Transgression. Timing, water level and potential water discharge of this event suggest a connection to a partial drainage of the Ancylus Lake. It is concluded that the threshold separating the Ancylus Lake from the North Sea needs to be located west of Fehmarn Belt. [Copyright &y& Elsevier]

Reid, D. G., Dyal, P. & Williams, S.T. (2012) A global molecular phylogeny of 147 periwinkle species (Gastropoda, Littorininae). - Zoologica Scripta, 41, 125-136. Complete species-level molecular phylogenies have been published for several genera of Littorinidae (e.g. Echinolittorina, Littoraria). Here we add new sequence data from three genes (28S rRNA, 12S rRNA, cytochrome oxidase c subunit I) for single specimens of an additional 24 species, to make a data set of 147 (97%) of the 152 recognized species of the subfamily Littorininae. This three-gene data set is analysed to produce a phylogenetic hypothesis for the subfamily, which includes the first complete species-level phylogeny of the genus Peasiella and the first three-gene phylogeny of all Littorina species. The non-planktotrophic species of Littorina have previously been classified together (as subgenus Neritrema), implying a single origin of this developmental mode. Tests of this hypothesis with the new data are inconclusive, and resolution is not improved in a tree constructed from five genes (adding previously published sequences of 16S rRNA and cytochrome b). Using available fossils for calibration we generate a BEAST chronogram, which emphasizes that the radiation of Littorina is more recent than that of other littorinine genera. A database is provided, listing all known species of Littorininae, with their distributions, development, ecology and gene sequences, as a tool for future evolutionary studies of this model group. [ABSTRACT FROM AUTHOR]

A high-resolution multiproxy study of core MD99-2286 reveals a highly variable hydrographic environment in the Skagerrak from 9300 cal. yr BP to the present. The study includes foraminiferal faunas, stable isotopes and sedimentary parameters, as well as temperature and salinity reconstructions of a c. 29 m long radiocarbon-dated core record. The multivariate technique fuzzy c-means was applied to the foraminiferal counts, and it was extremely valuable in defining subtle heterogeneities in the foraminiferal faunal data corresponding to hydrographic changes. The major early-/mid-Holocene (Littorina) transgression led to flooding of large former land areas in the North Sea, the opening of the English Channel and Danish straits, and initiation of the modern circulation system. This is reflected by fluctuating C/N values and an explosive bloom of Hyalinea balthica. A slight indication of ameliorated conditions between 8000 and 5750 cal. yr BP is related to the Holocene Thermal Maximum. A subsequent increase in freshwater/Baltic water influence between 5750 and 4350 cal. yr BP is reflected by dominance of Bulimina marginata and depleted δ18O values. The Neoglacial cooling (after 4350 cal. yr BP) is seen in the Skagerrak as enhanced turbidity, increasing TOC values and short-term changes in an overall Cassidulina laevigata-dominated fauna suggesting a prevailing influence of Atlantic waters. This is in agreement with increased strength of westerly winds, as recorded for this period. The last 2000 years were also dominated by Atlantic Water conditions with generally abundant nutrient supply. However, during warm periods, particularly the ‘Medieval Warm Period’and the modern warming, the area was subject to a restriction in the supply of nutrients and/or the nutrient supply had a more refractory character. [ABSTRACT FROM PUBLISHER]

The article discusses a study that showed marine gastropods Crepidula plana and Crepidula convexa specimens displayed immunity from trematode larvae, unlike gastropods that serve as intermediate hosts. Some 114 specimens of C. plana and 103 of C. convexa from Rhode Island and Massachusetts showed no parasitic infection although 264 Littorina littorea specimens, periwinkles, from the same sites were infected. The results are similar to those from two studies on C. fornicata of the same genus.

The article investigates a case in which feeding structures in the snail genus Littorina may have been retained after loss of feeding ability. Using light and scanning electron microscopy, the organization and behavior of velar ciliation in nonfeeding larvae of several species of Littorina. The velar cilia of living veligers of each species and their lengths were estimated with a calibrated ocular micrometer.

Abstract: Concentration of 99Tc has been measured in fucoids and molluscs, sampled in a sheltered intertidal at the southwest coast of Norway from February to November 2006. The concentrations of 99Tc in molluscs differed significantly between species. The filtering bivalve Mytilus edulis had the lowest concentrations with averages of 2.3–5.9Bqkg−1 d.w., while the herbivorous gastropods Littorina littorina, Littorina obtusata and Patella vulgata had higher concentrations. P. vulgata and L. obtusata had the highest concentrations, 40–47 and 26–30Bqkg−1 d.w., respectively. L. obtusata has a specialized habit of living, and prefers to feed on fucoids. P. vulgata can graze extensively on the fucoid Ascophyllum nodosum when available. Fucoids are known to have very high uptake of 99Tc, and this was also found in the present study. The high 99Tc-concentrations of L. obtusata and P. vulgata are most likely due to their habit of feeding on fucoids. [Copyright &y& Elsevier]

Two sympatric and divergent adaptive ecotypes of Littorina saxatilis (RB and SU) are known to hybridize showing partial premating isolation in the wild. Previous studies have revealed that morphological intermediate forms (presumably hybrids) present fitness (viability, sexual selection and fecundity) similar to that from pure ecotypes at the mid-shore. However, the absence of postzygotic isolation due to genetic incompatibility cannot be ruled out unless it is measured directly on true F hybrids. In this study, we overcome this problem and present data on 56 individual crosses including the four possible mating combinations (RB/RB, RB/SU, SU/RB and SU/SU) to compare fertilization and fecundity rates (including young progeny viability) between the four type crosses. Pooled RB female crosses showed apparently larger fertility and fecundity than pooled SU female crosses, probably because of differences in fecundity and laboratory survivorship between ecotypes. However, similar fertilization and fecundity rates were found for both RB and SU females when mated with different male types, supporting the idea that genetic-incompatibility-based postzygotic isolation can be ignored as a major determinant of this polymorphism in nature. [ABSTRACT FROM AUTHOR]

Core Psd-590 (length 947 cm, water depth 124 m) penetrated the entire sequence of marine (Littorina) mud (730 cm) and stopped in gray lacustrine (Ancylus) clays with hydrotroilitic films. The Littorina mud is gray-colored, microlaminated in the interval of 730 to 700 cm, and dark gray with hydrotoilitic films and obscure microlamination higher in the section. According to the diatom data, typical marine sediments begin at the level of 620 cm, while the lithological-geochemical data indicate this change at the level of 730 cm. This level is marked by a considerable increase in the concentrations of SiO, CO, C, and Mn in the sediments. In the interval of 730 to 620 cm, diatoms are represented by both freshwater and brackish-water species. The Littorina transgression began in the form of individual flows of saline North Sea waters into the Baltic Sea, which is evident from the microlamination and sharp peaks in the concentrations of the chemical elements. The transgression exhibits two weakening and one strengthening (core interval of 380 to 220 cm) stages; the latter was marked by the maximal water salinity. The post-Littorina mud contains molluscan shells and fish bones and is enriched in the fraction of 0.05-0.01 mm. The microlaminated Littorina mud was deposited during periods with stagnant conditions in the bottom water layer, while the homogenous sediments accumulated during periods of its aeration. [ABSTRACT FROM AUTHOR]

Numerous studies indicate that the behavioral responses of prey to the presence of predators can have an important role in structuring assemblages through trait-mediated indirect interactions. Few studies, however, have addressed how relative susceptibility to predation influences such interactions. Here we examine the effect of chemical cues from the common shore crab Carcinus maenas on the foraging behavior of two common intertidal gastropod molluscs. Of the two model consumers studied, Littorina littorea is morphologically more vulnerable to crab predation than Gibbula umbilicalis, and it exhibited greater competitive ability in the absence of predation threat. However, Littorina demonstrated a greater antipredator response when experimentally exposed to predation cues, resulting in a lower level of foraging. This reversed the competitive interaction, allowing Gibbula substantially increased access to shared resources. Our results demonstrate that the susceptibility of consumers to predation can influence species interactions, and suggest that inter-specific differences in trait-mediated indirect interactions are another mechanism through which non-consumptive predator effects may influence trophic interactions. [ABSTRACT FROM AUTHOR]

The hypothesis of a monogenic inheritance of dark longitudinal bands on the shell in the gastropods Littorina obtusata and L. saxatilis was checked. One gene having two alleles proved to be responsible for the shell banding pattern in both of the species. The presence of bands was a dominant character in either case. [ABSTRACT FROM AUTHOR]

The article explores the mesograzer and small predator-level seasonal change in trophic interactions. The authors used eelgrass Zostera marina, attached epiphytes and red alga Delesseria sanguinea that were collected in western Baltic Sea from April 2002 to February 2003 in their study. They found that in later spring and autumn, epiphytic algae was the primary source of organic matter for mesograzers. They also discovered that compared to other seasons, isopod Idotea baltica was more herbivorous in summer. They concluded that high plasticity of mesograzers is important for the stability of eelgrass food webs regardless of the variation in primary producers' biomass.

The article discusses a study on the variation in shells and fitness variables in Littorina saxatilis collected from the high intertidal of three shores on the east coast of Yorkshire, England. The snails were taken from pits and crevices in bedrock cliff or high-shore boulders in December and January. Principal component analyses (PCA) were used to analyze the linear dimension data. Extended eigenshape analysis results showed similar features in terms of relationships of shell to standardised tissue variables. Also noted is the possible existence of ontogenetic changes in the way the shell grows.

Ecosystem engineering is an important process in a variety of ecosystems. However, the relationship between engineer density and engineering impact remains poorly understood. We used experiments and a mathematical model to examine the role of engineer density in a rocky intertidal community in northern California. In this system, the whelk Nucella ostrina preys on barnacles ( Balanus glandula and Chthamalus dalli), leaving empty barnacle tests as a resource (favorable microhabitat) for other species. Field experiments demonstrated that N. ostrina predation increased the availability of empty tests of both barnacle species, reduced the density of the competitively dominant B. glandula, and indirectly increased the density of the competitively inferior C. dalli. Empty barnacle tests altered microhabitat humidity, but not temperature, and presumably provided a refuge from wave action. The herbivorous snail Littorina plena was positively associated with empty test availability in both observational comparisons and experimental manipulations of empty test availability, and L. plena density was elevated in areas with foraging N. ostrina. To explore the effects of variation in N. ostrina predation, we constructed a demographic matrix model for barnacles in which we varied predation intensity. The model predicted that number of available empty tests increases with predation intensity to a point, but declines when predation pressure was strong enough to severely reduce adult barnacle densities. The modeled number of available empty tests therefore peaked at an intermediate level of N. ostrina predation. Non-linear relationships between engineer density and engineer impact may be a generally important attribute of systems in which engineers influence the population dynamics of the species that they manipulate. [ABSTRACT FROM AUTHOR]

Maakia amurensis (strain A-18) cell culture synthesizes a significant quantity of isoflavonoids, a large part of which consists of isoflavone glucosides and malonylglucosides. β−D-Hydrolase enzyme complexes from the marine mollusk Littorina sitkana and the marine mycelial fungus P. canescens were used to obtain isoflavones from their conjugated forms. The specificity of β−D-glucanases from L. sitkana for various glycosides was studied. The deglycosylation efficiency depended on the aglycon structure. The deglycosylated fraction of isoflavonoids obtained from M. amurensis cell culture exhibited antitumor activity. [ABSTRACT FROM AUTHOR]

Many species with restricted gene flow repeatedly respond similarly to local selection pressures. To fully understand the genetic mechanisms behind this process, the phylogeographic history of the species (inferred from neutral markers) as well as the loci under selection need to be known. Here we sequenced an intron in the arginine kinase gene (Ark), which shows strong clinal variation between two locally adapted ecotypes of the flat periwinkle, Littorina fabalis. The 'small-sheltered' ecotype was almost fixed for one haplotype, H1, in populations on both sides of the North Sea, unlike the 'large-moderately exposed ecotype', which segregated for ten different haplotypes. This contrasts with neutral markers, where the two ecotypes are equally variable. H1 could have been driven to high frequency in an ancestral population and then repeatedly spread to sheltered habitats due to local selection pressures with the colonization of both sides of the North Sea, after the last glacial maximum (∼18 000 years ago). An alternative explanation is that a positively selected mutation, in or linked to Ark, arose after the range expansion and secondarily spread through sheltered populations throughout the distribution range, causing this ecotype to evolve in a concerted fashion. Also, we were able to sequence up to four haplotypes consistently from some individuals, suggesting a gene duplication in Ark. [ABSTRACT FROM AUTHOR]

The gastropod Littorina littorea (common periwinkle) is an abundant and widespread North Atlantic species. The characteristic development of Intersex in L. littorea has been widely applied as a biomarker for tributyltin (TBT) contamination. Here, we assess the potential of L. littorea as a novel sentinel species for evaluating the sublethal effects in wild populations of widely distributed contaminants. We collected animals from six sites across the South coast of England. Tissue concentrations of polycyclic aromatic hydrocarbons (PAHs), organotin compounds (OTCs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs) were measured and compared with biomarkers of damage to DNA (Comet assay), lysosomal stability (NRR assay), and endocrine disruption (Intersex development). There was a strong correlation between DNA damage and PAH bioaccumulation (n = 6, r = 0.84, p < 0.05), as well as that between Intersex development and OTC pollution (n = 6, r = 0.91, p < 0.05). The relationship between PAH bioaccumulation and DNA strand breaks was nonlinear, highlighting the need to consider the role of adaptive mechanisms in the interpretation of field results. These results illustrate the potential use of periwinkles for monitoring a wide range of priority pollutants. [ABSTRACT FROM AUTHOR]

Rößler, D., Moros, M. & Lemke, W. 2010: The Littorina transgression in the southwestern Baltic Sea: new insights based on proxy methods and radiocarbon dating of sediment cores. Boreas, 10.1111/j.1502-3885.2010.00180.x. ISSN 0300-9483. The Littorina transgression is one of the most pronounced environmental events in the Holocene history of the Baltic Sea. It changed the hydrographic system from the freshwater Ancylus Lake into the brackish-marine Littorina Sea. Here, 18 cores from two western Baltic basins, Mecklenburg Bay and the Arkona Basin, were analysed. We show that, besides biological indicators, sedimentary organic carbon, C/N ratio, bulk δC isotope values and carbonate content display clearly the transition from Ancylus Lake to the Littorina Sea. The first appearances of benthic foraminifers, marine molluscs and ostracods represent the onset of brackish-marine conditions in the bottom waters. Central Arkona Basin sediments display more abrupt shifts in geochemical parameters and microfossil records at the transition from Ancylus Lake to the Littorina Sea than those from Mecklenburg Bay. Mixing of reworked Ancylus material with Littorina Sea stage material was stronger in Mecklenburg Bay, resulting in less pronounced proxy parameter changes and older bulk material dates. Radiocarbon dating of both calcareous material (benthic foraminifers, mollusc shells) and bulk fractions at the transgression horizon shows large age discrepancies. Based on calcareous fossil dates it appears that marine waters began to enter Mecklenburg Bay c. 8000 cal. a BP. In the Arkona Basin the first marine signals are recorded approximately 800 years later, c. 7200 cal. a BP. This indicates a transgression pathway via the Great Belt into Mecklenburg Bay and then into the Arkona Basin. [ABSTRACT FROM AUTHOR]

The accumulation and trophic transfer of the platinum group elements (PGE): Rh, Pd and Pt; have been studied in short-term (5 day) exposures conducted in aquaria containing the marine macroalga, Ulva lactuca, and/or the grazing mollusc, Littorina littorea. Metals added to sea water (to concentrations of 20 μg L−1) were taken up by U. lactuca in the order Rh, Pt > Pd and by L. littorea in the order Pd ≥ Pt ≥ Rh, with greatest metal accumulation in the latter generally occurring in the visceral complex and kidney. When fed contaminated alga, accumulation of Rh and Pd by L. littorea, relative to total available metal, increased by an order of magnitude, while accumulation of Pt was not readily detected. We conclude that the diet is the most important vector for accumulation of Rh and Pd, while accumulation of Pt appears to proceed mainly from the aqueous phase. [Copyright &y& Elsevier]

The hypothesis on monogenic inheritance of white spot pattern on the shell of the gastropod snail Littorina obtusata was tested. Although in most cases our results did not contradict this assumption, the hypothesis cannot explain the observed segregation in general. An alternative hypothesis was suggested, according to which the presence of spot pattern is controlled by two complementary biallelic genes. [ABSTRACT FROM AUTHOR]

Conceptual models predict a unimodal effect of consumer abundance on prey diversity with the highest diversity at intermediate consumer abundance (intermediate disturbance hypothesis). Consumer selectivity and prey productivity are assumed to be further important determinants. Preferential grazing on dominant prey species favoured by high nutrient supply is supposed to increase prey diversity, whereas the effect of consumers on prey diversity may be negative under low nutrient conditions (grazer reversal hypothesis). We tested the effect of four common consumers the isopod Idotea baltica, the amphipod Gammarus oceanicus, and the gastropods Littorina littorea and Rissoa membranacea on diversity and composition of epiphytes growing on eelgrass Zostera marina. Consumer density was manipulated (four levels: grazer free control, low, medium, high) based on abundances observed in eelgrass systems. Additionally, we manipulated nutrient supply (three levels) and the presence of Idotea in a factorial experiment. The impact of consumer abundance on epiphyte diversity varied depending on consumer identity and epiphyte evenness was affected rather than species number in this short-term experiment. Idotea reduced epiphyte diversity (Shannon-Wiener index H') and Gammarus increased epiphyte diversity. Littorina had no effect at low and medium abundance, but a negative effect in the high density treatment. Only Rissoa supported the conceptual models as it caused the proposed unimodal pattern in epiphyte diversity. The varying species-specific selectivity of the studied consumers is likely to explain their diverse impact on epiphyte diversity. Nutrients enhanced epiphyte diversity at medium enrichment, whereas higher nutrient supply reduced epiphyte diversity. The effect of Idotea changed from negative at low nutrient concentration to positive at higher nutrient supply, supporting the grazer reversal hypothesis. This study implies that consumer species identity and nutrient concentrations are important in controlling prey diversity and composition. Different consumer selectivity and changes in selectivity with growing consumer abundance and nutrient concentration are the causal factors for this effect. [ABSTRACT FROM AUTHOR]

Abstract: A latitudinal cline in length-standardized shell thickness and mass of Littorina obtusata in the Gulf of Maine (GoM) has been attributed to predation by the European green crab Carcinus maenas. However, latitudinal variation in water temperature may also contribute to this cline. To investigate this hypothesis, we grew snails from 2 thin-shelled and 2 thick-shelled populations in warm (16°C) and cold (10°C) water treatments, representing summer temperatures of southern and northern parts of the GoM, respectively. Snails grown in warmer water showed a markedly greater increase in shell length (50%) and shell mass (60%) compared to conspecifics grown in colder water, but shell mass standardized for length was only weakly (relative to clinal variation) and not consistently (among populations) affected by temperature. Our experimental snails made shells that were lighter, when standardized for length, than conspecifics grown in nature. This “shell thinning” was particularly apparent in warmer water, because experimental snails diverted the increased calcification afforded by warmer water parallel (shell elongation) rather than perpendicular (shell thickening) to the axis of shell coiling. Interestingly, we estimate that if 16°C snails had only grown to the length of 10°C snails and used the additional shell material they produced to make their shell thicker rather than longer, they would have produced a shell comparable in mass to that of snails from the same population and shell length grown in nature. We conclude that water temperature is not directly responsible for natural variation in size-standardized shell thickness of L. obtusata in the GoM, but that it may contribute to this pattern indirectly, for example by facilitating the snail''s plastic phenotypic response (shell thickening) to predation risk. [Copyright &y& Elsevier]

The hermit crab Pagurus longicarpus was shown to inhabit shells that were partially predated from intertidal areas of Long Island, New York. Among field collections of P. longicarpus, 2.13% of the hermit crabs (46 of 2155) were found with shells with snail tissue present. Over 90% of these partially predated snail shells were occupied by male hermit crabs. Although hermit crabs were in 8 species of snail shells, only Littorina littorea and Nassarius obsoletus were found occupied by hermit crabs and containing snail tissue. In the laboratory, we found that specimens of the spider crab Libinia emarginata were able to pull off the operculum of snails, leaving damage as found in field collections. In contrast, specimens of P. longicarpus were not able to prey on live, healthy snails. When specimens of P. longicarpus were placed in communal tanks, hermit crabs preferred partially predated snail shells to empty and original shells. However, original shells and empty shells were occupied with more frequency than partially predated shells when crabs were isolated. These findings indicate P. longicarpus actively seeks shells soon after attack and abandonment by snail predators, especially in the presence of competitors. [ABSTRACT FROM AUTHOR]

Empirical estimates of selection gradients caused by predators are common, yet no one has quantified how these estimates vary with predator ontogeny. We used logistic regression to investigate how selection on gastropod shell thickness changed with predator size. Only small and medium purple shore crabs ( Hemigrapsus nudus) exerted a linear selection gradient for increased shell-thickness within a single population of the intertidal snail ( Littorina subrotundata). The shape of the fitness function for shell thickness was confirmed to be linear for small and medium crabs but was humped for large male crabs, suggesting no directional selection. A second experiment using two prey species to amplify shell thickness differences established that the selection differential on adult snails decreased linearly as crab size increased. We observed differences in size distribution and sex ratios among three natural shore crab populations that may cause spatial and temporal variation in predator-mediated selection on local snail populations. [ABSTRACT FROM AUTHOR]

The article discusses research on the indirect interaction between two different species of meso-herbivores mediated by seaweeds. It references a study by Hee Young Yun at the Alfred Wegener Institute for Polar and Marine Research in Helgoland, Germany, and his colleagues, published in the June 3, 2010 issue of "Marine Ecology Progress Series." The researchers studied whether the feeding of the isopod Idotea baltica or the periwinkle Littorina littorea influenced the consumption by other consumers through anti-herbivory defense induction in the brown seaweed called Fucus vesiculosus. They conclude that the quantity and quality of induced defenses appears to be independent of the identity of the inducer.

We describe an efficient algorithm for determining exactly the minimum number of sires consistent with the multi-locus genotypes of a mother and her progeny. We consider cases where a simple exhaustive search through all possible sets of sires is impossible in practice because it would take too long to complete. Our algorithm for solving this combinatorial optimization problem avoids visiting large parts of search space that would not result in a solution with fewer sires. This improvement is of particular importance when the number of allelic types in the progeny array is large and when the minimum number of sires is expected to be large. Precisely in such cases, it is important to know the minimum number of sires: this number gives an exact bound on the most likely number of sires estimated by a random search algorithm in a parameter region where it may be difficult to determine whether it has converged. We apply our algorithm to data from the marine snail, Littorina saxatilis. [ABSTRACT FROM AUTHOR]

The article reports on the result of a study which tested the density-dependent responses to grazer removal on the biomass and composition of natural high rocky-shore biofilms over a seven month period. Result of the study shows that effects of grazing history are not exclusive to macrophytic systems. In addition, grazers boosted the concentration of micro-autotrophs relative to non-chl a biofilm constituent, plausibly by removing an unproductive biofilm canopy and facilitating light and nutrient penetration for new growth.

The article reports on the result of a study which examines the effect of four common mesograzers, such as the isopod Idotea baltica, the amphipod Gammarus oceanicus, and the gastropods Littorina littorea and Rissoa membranacea on epiphytes in an eelgrass Zostera marina L. system. Result shows that the positive effect of the two gastropod species disappeared under higher nutrient supply, implying the importance of nutrient limitation for this interaction. Meanwhile, the effect of I. baltica remained at moderate grazer densities despite the higher nutrient concentrations.

Intertidal gastropods and bivalves are important hosts for a wide range of metazoan parasites, which may exert a variety of negative effects on their hosts with consequences for mollusc population dynamics and community structure. Although vital for our understanding of the relative importance of parasites in intertidal ecosystems, quantitative information on macroparasite communities in molluscs is still largely missing. We examined the macroparasite community in Littorina littorea, Nucella lapillus, Patella vulgata and Mytilus edulis/galloprovincialis from rocky shore habitats on the south coast of Ireland. In total, twelve macroparasite taxa belonging to four major parasite groups were found in 3900 examined host individuals from sixteen intertidal localities. Digenean trematodes were the dominant parasite group, occurring in all of the investigated mollusc species and at all sampling sites. The macroparasite community in gastropods was largely similar to the species composition reported from other European shore localities, possibly due to a wide distribution of bird final hosts. In contrast, the parasite community composition observed in mussels showed obvious differences when compared to data on macroparasites in mussels from soft sediment habitats, which is probably related to differences in the species composition of gastropods acting as first intermediate hosts on rocky shores. Comparatively low infection rates in molluscs on the south coast of Ireland indicate differences in the abundance of bird final hosts as well as less suitable conditions for parasite transmission. Thus, effects of parasitism on the molluscan hosts can be assumed to be rather low, which is favourable from an economic point of view, since periwinkles and mussels are commercially exploited in Ireland. [ABSTRACT FROM AUTHOR]

The MACPF domain-containing proteins potentially able to build a transmembrane pore structure are found in the transcriptome of a common periwinkle kidney loaded with trematode rediae. Two homologs of mammalian Macrophage expressed gene 1 (Mpeg1), Ll Mpeg1-1 and LI Mpeg1-2, share similar domain structure with the only difference such as LI Mpeg1-2 transcript lacks of a C-terminal transmembrane helix. Expression of membrane-anchored protein Ll Mpeg1-1 is similar in kidneys of naturally infected with trematode Himasthla elongata and uninfected snails. The expression of the second soluble LI Mpeg1-2 protein is 4-fold upregulated under infection. The third MACPF protein found in Littorina littorea kidney is homologous with Perivitellin – 2 67 kDa subunit named Ll PV2-67 and the expression of the transcript is 3-fold upregulated in the kidney of infected snails. The last two molecules are candidate effectors that may participate in the immune response of common periwinkles to trematode infestation. A single parasite-expressed MACPF-like protein was recorded from the transcriptome of Himasthla elongata . [ABSTRACT FROM AUTHOR]

Eight new microsatellite loci were characterized for Littorina saxatilis (Olivi, 1792) and tested for their cross-hybridization in congeners. All loci were polymorphic in Irish and Celtic Sea samples, with an average number of alleles per locus of 15 (range, 6-31). Observed and expected locus heterozygosities ranged from 26 to 85% and from 53 to 92%, respectively. Three loci showed excess homozygosity and significant departures from Hardy-Weinberg expectations in one sample, possibly due to null alleles, population structuring or inbreeding. No linkage disequilibrium was detected among loci within samples. A high degree of cross-hybridization was observed in closely related congeners and most loci were polymorphic. These markers will be useful for investigating population genetic diversity and connectivity in coastal populations, especially for marine reserve design. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we investigated why a littorinid snail, Littorina sitkana, preferentially consumes the ulvoid green algae Ulva lactuca and Ulva linza, even though these algae contain high concentrations of dimethylsulfoniopropionate (DMSP), which has been shown to be the precursor to an activated defense that deters feeding by sea urchins (Strongylocentrotus droebachiensis and S. purpuratus). When urchins consume algae containing DMSP, the DMSP is rapidly cleaved into DMS and acrylic acid, which are feeding deterrents to the urchins. In multiple-choice feeding-preference assays, L. sitkana consumed U. lactuca and U. linza at a greater rate than six other algal species. In experiments to confirm that DMSP was being cleaved by the snails, DMS was generated when snails were fed either U. lactuca or U. linza, but was not present in containers with snails alone or algae alone. In laboratory bioassays, acrylic acid reduced feeding by snails when it was incorporated into agar-based diets at concentrations of 0.25% and 0.50% of the food''s fresh mass, demonstrating that the animals are deterred by one of the products of DMSP cleavage. When feeding rates from multiple-choice feeding-preference assay were compared to the carbon to nitrogen ratio (C:N) of the macroalgae, there was a strong negative linear relationship between grazing rates and C:N until a C:N of ~8 was reached. Algae with a C:N higher than 8 were avoided by snails. When the snails were offered agar-based diets containing a range of nitrogen concentrations (1.96–6.85% of the dry mass), feeding rates were positively correlated with the diets'' nitrogen concentrations and negatively correlated with their C:N. Because L. sitkana forages only during low tides, it may have a limited window of time to obtain sufficient nitrogen. Therefore, it may preferentially select foods with high nitrogen concentrations, even though these foods contain chemical defenses. [Copyright &y& Elsevier]

Abstract: The short-term (5 day) accumulation of Cu and Zn in different tissues of the marine gastropod, Littorina littorea, has been studied in the presence of ∼10mgl−1 of antifouling paint particles and pre- or simultaneously contaminated algal food (Ulva lactuca). Accumulation of Cu was observed in the head–foot, digestive gland–gonad complex and gills to extents dependent on how and when food was contaminated and administered. However, retention of Zn was only observed in the gills and only when L. littorea and U. lactuca were simultaneously exposed to paint particles. Relative to the alga, faecal material was highly enriched in Zn, suggesting that the animal is able to rapidly eliminate this metal, most likely through the formation and egestion of insoluble phosphate granules. Thus, L. littorea is a useful biomonitor of marine contamination by antifouling applications in respect of Cu but not Zn. [Copyright &y& Elsevier]