Home About us Contact
|
Home About us Contact | ||
|
|
||
Gastropod Species (gastropod + species)
Selected AbstractsEnvironmental determinants correlated to Vibrio harveyi -mediated death of marine gastropodsENVIRONMENTAL MICROBIOLOGY, Issue 1 2010Youhei Fukui Summary Vibrio harveyi is an emerging pathogen that causes mass mortality in a wide variety of marine animal species; however, it is still unclear which environmental determinants correlate V. harveyi dynamics and the bacterium-mediated death of marine animal life. We conducted a correlation analysis over a 5-year period (2003,2007) analysing the following data: V. harveyi abundance, marine animal mortality and environmental variables (seawater temperature, salinity, pH, chlorophyll a, rainfall and total viable bacterial counts). The samples were collected from a coastal area in northern Japan, where deaths of a marine gastropod species (Haliotis discus hannai) have been reported. Our analysis revealed significant positive correlations between average seawater temperature and average V. harveyi abundance (R = 0.955; P < 0.05), and between average seawater temperature and V. harveyi -mediated abalone death (R = 0.931; P < 0.05). Based on the regression model, n°C rise in seawater temperature gave rise to a 21n -fold increase in the risk of mortality caused by V. harveyi infection. This is the first report providing evidence of the strong positive correlation between seawater temperature and V. harveyi -mediated death of marine species. [source] Using molecular and quantitative variation for assessing genetic impacts on Nucella lapillus populations after local extinction and recolonizationINTEGRATIVE ZOOLOGY (ELECTRONIC), Issue 2 2006Isabelle Colson Abstract The dogwhelk Nucella lapillus is a predatory marine gastropod living on rocky shores in the North Atlantic. As with many other gastropod species, Nucella was affected by tributyltin (TBT) pollution during the 1970s and 1980s, and local populations underwent extinction. After a partial ban on TBT in the UK in 1987, vacant sites have been recolonized. Levels of genetic diversity and quantitative genetic variation in shell form were compared between recolonized sites and sites that showed continuous population at three localities across the British Isles. Overall, estimates of genetic diversity were only slightly lower in recolonized populations, suggesting that populations have recovered from previous impacts due to the relatively high levels of migration from non-impacted sites. Molecular and quantitative analyses are broadly concordant and a positive correlation was observed (although not statistically significant) between molecular and quantitative estimates of genetic diversity, indicating the potential usefulness of quantitative methods to complement molecular population genetics analyses. [source] Life history of Littorina scutulata and L. plena, sibling gastropod species with planktotrophic larvaeINVERTEBRATE BIOLOGY, Issue 1 2002Paul A. Hohenlohe Abstract. The intertidal, sibling species Littorina scutulata and L. plena (Gastropoda, Proso-branchia) are sympatric throughout most of their ranges along the Pacific coast of North America. Both species release disc-shaped, planktonic egg capsules from which planktotrophic veliger larvae hatch. Here I review existing data and present new observations on these species' life history, including age at first reproduction, spawning season, maximum fecundity rates, capsule morphology, egg size and number, pre-hatching development, larval growth at three food concentrations, potential settlement cues, planktonic period, and protoconch size. Previous classification of egg capsule morphologies used to distinguish the species is inaccurate; instead, capsules can be categorized into three types of which each species may produce two. Females of L. scutulata produced capsules with either two rims of unequal diameter or one rim, while females of L. plena produced capsules with one rim or two rims of nearly equal diameter. Females of each species spawned sporadically from early spring to early fall in Puget Sound. Larvae of L. plena hatched one day earlier than those of L. scutulata, and both species grew fastest in the laboratory at intermediate food concentrations. Larvae metamorphosed in the presence of a variety of materials collected from their adult habitat, including conspecific adults, algae, rocks, and barnacle tests. This is the first report of planktotrophic larvae in this genus metamorphosing in the laboratory. The total planktonic period of 8 larvae of L. scutulata raised in the laboratory was 37,70 days, and a single larva of L. plena metamorphosed after 62 days. Protoconch diameter of shells collected from the field was 256,436 ,m and did not differ significantly between the species. Previous allozyme and mitochondrial DNA work has suggested high levels of genetic variability in both species and greater genetic population structure in L. plena, despite the long spawning season and long-lived larvae in both species. The interspecific life history differences described here appear insufficient to produce consistent differences in gene flow patterns. [source] Major muscle systems in the larval caenogastropod, Ilyanassa obsoleta, display different patterns of developmentJOURNAL OF MORPHOLOGY, Issue 10 2009Carol C.E. Evans Abstract This study describes the anatomical and developmental aspects of muscular development from the early embryo to competent larval stage in the gastropod Ilyanassa obsoleta. Staining of F-actin revealed differential spatial and temporal patterns of several muscles. In particular, two major muscles, the larval retractor and pedal retractor muscles originate independently and display distinct developmental patterns similar to observations in other gastropod species. Additionally, together with the larval retractor muscle, the accessory larval muscle developed in the embryo at the trochophore stage. Therefore, both these muscles develop prior to ontogenetic torsion. The pedal retractor muscle marked the most abundant growth in the mid veliger stage. Also during the middle stage, the metapodial retractor muscle and opercular retractor muscle grew concurrently with development of the foot. We show evidence that juvenile muscles, such as the buccal mass muscle and siphon muscle develop initially during the late veliger stage. Collectively, these findings substantiate that larval myogenesis involves a complex sequence of events that appear evolutionary conserved within the gastropods, and set the stage for future studies using this model species to address issues concerning the evolution and eventual fates of larval musculature in molluscs. J. Morphol., 2009. © 2009 Wiley-Liss, Inc. [source] Multi-component stable isotope records from Late Weichselian and early Holocene lake sediments at Imio,ki, Poland: palaeoclimatic and methodological implications,JOURNAL OF QUATERNARY SCIENCE, Issue 8 2009Karina Apolinarska Abstract Late Weichselian and early Holocene climatic and environmental changes are inferred from stable carbon and oxygen isotope records obtained on bulk and biogenic carbonates from the sediment sequence of Lake Lednica, western Poland. Along with sediment and pollen stratigraphic data, a wide range of carbonate components occurring in the sediments was analysed for ,13C and ,18O, including shells of several gastropod species and the bivalve genus Pisidium, carapaces of the ostracod subfamily Candoninae and oogonia of the aquatic macrophyte genus Chara. The development of catchment soils and the onset of authigenic carbonate production in response to the climatic amelioration during the Late Weichselian are clearly reflected by rising carbonate content, distinct isotopic shifts in bulk carbonates and decreasing ,13C values of bulk organic matter in the sediments. The GI-1/GS-1 (the Bølling,Allerød Interstadial complex/Younger Dryas Stadial) and the GS-1/Preboreal transitions are marked by significant shifts in ,18O values of 2,3,, as well as by distinct changes in carbonate content, indicative of a decrease and a subsequent increase in mean annual temperature. Corresponding ,13C records reflect primarily changes in aquatic productivity, with favourable conditions for phytoplankton and macrophytes during GI-1 and the Preboreal resulting in persistent 13C enrichment. The Younger Dryas Stadial is characterised by depletions in 13C and 18O, with indications of a climatic tripartition. Consistent offsets in ,13C and ,18O between records obtained on specific carbonate components reflect vital effects in combination with seasonal characteristics and habitat preferences of the respective carbonate-precipitating biota. Largely parallel first-order variations in ,13C and ,18O of the different carbonate components demonstrate that individual isotope records may provide important palaeoclimatic information, although more detailed reconstructions can be obtained from multi-component analysis. Copyright © 2009 John Wiley & Sons, Ltd. [source] Spatial and temporal population genetic structure of four northeastern Pacific littorinid gastropods: the effect of mode of larval development on variation at one mitochondrial and two nuclear DNA markersMOLECULAR ECOLOGY, Issue 10 2009HYUK JE LEE Abstract We investigated the effect of development mode on the spatial and temporal population genetic structure of four littorinid gastropod species. Snails were collected from the same three sites on the west coast of Vancouver Island, Canada in 1997 and again in 2007. DNA sequences were obtained for one mitochondrial gene, cytochrome b (Cyt b), and for up to two nuclear genes, heat shock cognate 70 (HSC70) and aminopeptidase N intron (APN54). We found that the mean level of genetic diversity and long-term effective population sizes (Ne) were significantly greater for two species, Littorina scutulata and L. plena, that had a planktotrophic larval stage than for two species, Littorina sitkana and L. subrotundata, that laid benthic egg masses which hatched directly into crawl-away juveniles. Predictably, two poorly dispersing species, L. sitkana and L. subrotundata, showed significant spatial genetic structure at an 11- to 65-km geographical scale that was not observed in the two planktotrophic species. Conversely, the two planktotrophic species had more temporal genetic structure over a 10-year interval than did the two direct-developing species and showed highly significant temporal structure for spatially pooled samples. The greater temporal genetic variation of the two planktotrophic species may have been caused by their high fecundity, high larval dispersal, and low but spatially correlated early survivorship. The sweepstakes-like reproductive success of the planktotrophic species could allow a few related females to populate hundreds of kilometres of coastline and may explain their substantially larger temporal genetic variance but lower spatial genetic variance relative to the direct-developing species. [source] Parallel changes in genetic diversity and species diversity following a natural disturbanceMOLECULAR ECOLOGY, Issue 6 2009GUILLAUME EVANNO Abstract We examined the spatial and temporal variation of species diversity and genetic diversity in a metacommunity comprising 16 species of freshwater gastropods. We monitored species abundance at five localities of the Ain river floodplain in southeastern France, over a period of four years. Using 190 AFLP loci, we monitored the genetic diversity of Radix balthica, one of the most abundant gastropod species of the metacommunity, twice during that period. An exceptionally intense drought occurred during the last two years and differentially affected the study sites. This allowed us to test the effect of natural disturbances on changes in both genetic and species diversity. Overall, local (alpha) diversity declined as reflected by lower values of gene diversity HS and evenness. In parallel, the among-sites (beta) diversity increased at both the genetic (FST) and species (FSTC) levels. These results suggest that disturbances can lead to similar changes in genetic and community structure through the combined effects of selective and neutral processes. [source] Coexistence patterns of benthic gastropods on the Uruguayan shelfOIKOS, Issue 8 2010Alvar Carranza Community assembly rules theory attempt to understand the processes that determine the composition of local communities from a regional species pool. Nestedness and negative co-occurrence are two of the most commonly reported meta-community patterns, but almost exclusively from terrestrial and freshwater ecosystems. Here we analyzed the structure of species coexistence in six datasets containing presence/absence data for 120 marine benthic gastropod species in 249 sampling units on the Uruguayan continental shelf and Río de la Plata estuary. The ecological features of this system, such as the idiosyncratic nature of the biogeographic and oceanographic realms, are clearly different from those observed in other systems previously targeted by studies on coexistence structure. Community patterns were evaluated using null models and four structure indices. The existence of patterns in community assembly, and in particular segregated co-occurrence, was verified only when analyzing the number of checkerboard units (CH index). This indicates more mutually exclusive species pairs than expected by chance. Nestedness, on the other hand, was not detected in any dataset. Storage and rescue effects related to overall high immigration and low local extinction rates are plausible mechanisms to account for the general pattern of random species coexistence, while the segregated co-occurrence pattern depicted by the CH index may be related to differential habitat requirements within species pairs. Our study highlights the importance of analyzing metacommunity structures in alternative biological, environmental, and historical contexts in order to advance on the construction of a general ecological theory, relating patterns with the processes dominating in particular ecosystems. [source] The island rule and the evolution of body size in the deep seaJOURNAL OF BIOGEOGRAPHY, Issue 9 2006Craig R. McClain Abstract Aim, Our goal is to test the generality of the island rule , a graded trend from gigantism in small-bodied species to dwarfism in large-bodied species , in the deep sea, a non-insular but potentially analogous system. Location, Shallow-water and deep-sea benthic habitats in the western Atlantic Ocean from the North to South Poles. Methods, We conducted regression analyses of body size of deep-sea gastropods species relative to their shallow-water congeners using measurements from the Malacolog ver. 3.3.3 database. Results, Our results indicate that, consistent with the island rule, gastropod genera with small-bodied, shallow-water species have significantly larger deep-sea representatives, while the opposite is true for genera that are large-bodied in shallow water. Bathymetric body size clines within the deep sea are also consistent with predictions based on the island rule. Main conclusions, Like islands, the deep sea is characterized by low absolute food availability, leading us to hypothesize that the island rule is a result of selection on body size in a resource-constrained environment. The body size of deep-sea species tends to converge on an optimal size for their particular ecological strategy and habitat. [source] | |||||||||||||