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opencc-zeroJul 2020View details →

Data from: Shells of the bivalve Astarte moerchi give new evidence of a strong pelagic-benthic coupling shift occurring since the late 1970s in the NOW Polynya

Climate changes in the Arctic may weaken the currently tight pelagic-benthic coupling. In response to decreasing sea ice cover, arctic marine systems are expected to shift from a 'sea-ice algae-benthos' to a 'phytoplankton-zooplankton' dominance. We used mollusk shells as bioarchives and fatty acid trophic markers to estimate the effects of the reduction of sea ice cover on the exported food to the seafloor. Bathyal bivalve Astarte moerchi that lives at 600 m depth in northern Baffin Bay reveals a clear shift in growth variations and Ba/Ca ratios since the late 1970s that we relate to a change in food availability. Fatty acid compositions of tissues show that this species feeds mainly on microalgae exported from the euphotic zone to the seabed. We thus suggest that changes in pelagic-benthic coupling are likely due to either local changes in sea ice dynamics, mediated through bottom-up regulation exerted by sea ice on phytoplankton production or to a mismatch between phytoplankton bloom and zooplankton grazing due to change in their phenology. Both possibilities allow a more regular and increased transfer of food to the seabed.

opencc-zeroAug 2020View details →

Controls on range shifts of coastal Californian bivalves during the peak of the last interglacial and baseline predictions for today

As the most recent time in Earth history when global temperatures were warmer than at present, the peak of the last interglacial (Marine Isotope Substage [MIS] 5e; ~120,000 years ago) can serve as a pre-anthropogenic baseline for a warmer near-future world. Here we use a new compilation of 22 fossil localities in California that have been reliably dated to Marine Isotope Stage (MIS) 5e to establish baseline expectations for contemporary bivalve species movements by identifying and analyzing bivalve species with "extralimital" ranges, i.e. species that occupied the California region during MIS 5e but are now restricted to adjacent regions. We find that 15% of species (n = 142) found in MIS 5e localities have extralimital ranges and currently occupy warmer waters to the south of the California region. The majority of extralimital occurrences occur in paleo-embayments, suggesting that these sheltered habitats were more suitable habitats for warm-water species than exposed coasts during the MIS 5e. We further find that extralimital species now tend to occur in cooler, more seasonally productive coastal waters and to occupy more offshore islands when compared to the broader species pool immediately south of California. These findings suggest that high dispersal potential and pre-existing tolerances to environmental conditions similar to California's comparatively cool and seasonally productive environments may have enabled extralimital bivalves to colonize the California region during MIS 5e.

opencc-by-4.0Jan 2018View details →

ShellTrace v2.0 - Bivalve growth and trace element model

This file contains the R-script used to model growth and trace element uptake in bivalve shells, as described in the equally named Geoscientific Model Development publication (de Winter et al., 2017), including a copy of the manuscript preprint.

FIGURE 8 in Opaepupu, a new genus and species of bivalve-associated shrimp (Decapoda Caridea: Palaemonidae) from Hawai'i

FIGURE 8. Opaepupu huna gen. et sp. nov., colour pattern in life: A—holotype, ovigerous female (pocl 3.6 mm, cl 4.3 mm) from Kâne'ohe Bay, Hawai'i (FLMNH UF 45826); B—allotype, male (pocl 2.3 mm, cl 2.9 mm) from the same locality (FLMNH UF 51717). Photographs courtesy of Gustav Paulay.

FIGURE 7 in Opaepupu, a new genus and species of bivalve-associated shrimp (Decapoda Caridea: Palaemonidae) from Hawai'i

FIGURE 7. Opaepupu huna gen. et sp. nov., allotype, male (pocl 2.3 mm, cl 2.9 mm) from Kâne'ohe Bay, Hawai'i (FLMNH UF 51717): A—left second pereiopod (cheliped), dorsomesial view; B—same, ventrolateral view; C—same, carpus and chela, mesial view; D—same, chela fingers closed, mesial view; E—right second pereiopod (cheliped), carpus and chela, mesial view. Setae omitted in D.

FIGURE 6 in Opaepupu, a new genus and species of bivalve-associated shrimp (Decapoda Caridea: Palaemonidae) from Hawai'i

FIGURE 6. Opaepupu huna gen. et sp. nov., allotype, male (pocl 2.3 mm, cl 2.9 mm) from Kâne'ohe Bay, Hawai'i (FLMNH UF 51717): A—frontal region, dorsal view; B—rostrum, dorsal view; C—same, detail of tip (drawn without scale); D—distal pleonites, telson and right uropod, lateral view; E—telson and left uropod, dorsal view; F—right first pleopod, mesial view; H—right second pleopod, lateral view.

FIGURE 4 in Opaepupu, a new genus and species of bivalve-associated shrimp (Decapoda Caridea: Palaemonidae) from Hawai'i

FIGURE 4. Opaepupu huna gen. et sp. nov., holotype, ovigerous female (pocl 3.6 mm, cl 4.3 mm) from Kâne'ohe Bay, Hawai'i (FLMNH UF 45826): A—left second pereiopod (cheliped), dorsomesial view; B—same, ventrolateral view; C—same, carpus and chela, lateral view; D—same, carpus and chela, mesial view; E—same, chela fingers closed, mesial view; F—same, chela fingers opened, mesial view; G—right second pereiopod (cheliped), carpus and chela, lateral view; H—same, chela fingers closed. Setae omitted in E, F, H.

FIGURE 5 in Opaepupu, a new genus and species of bivalve-associated shrimp (Decapoda Caridea: Palaemonidae) from Hawai'i

FIGURE 5. Opaepupu huna gen. et sp. nov., holotype, ovigerous female (pocl 3.6 mm, cl 4.3 mm) from Kâne'ohe Bay, Hawai'i (FLMNH UF 45826): A—left first pereiopod (cheliped), lateral view; B—same, chela, mesial view; C—left third pereiopod, lateral view; D—same, distal portion of propodus and dactylus, lateral view; E—left fifth pereiopod, lateral view; F—same, distal portion of propodus and dactylus, mesial view.

FIGURE 3 in Opaepupu, a new genus and species of bivalve-associated shrimp (Decapoda Caridea: Palaemonidae) from Hawai'i

FIGURE 3. Opaepupu huna gen. et sp. nov., holotype, ovigerous female (pocl 3.6 mm, cl 4.3 mm) from Kâne'ohe Bay, Hawai'i (FLMNH UF 45826): A—mandible, lateral view; B—same, incisor process, dorsal view; C—maxillule, lateral view; D—maxilla, lateral view; E—first maxilliped, lateral view; F—second maxilliped, lateral view; G—third maxilliped, lateral view; H—paragnaths and median lip, ventral view.

FIGURE 2 in Opaepupu, a new genus and species of bivalve-associated shrimp (Decapoda Caridea: Palaemonidae) from Hawai'i

FIGURE 2. Opaepupu huna gen. et sp. nov., holotype, ovigerous female (pocl 3.6 mm, cl 4.3 mm) from Kâne'ohe Bay, Hawai'i (FLMNH UF 45826): A—frontal region, dorsal view; B—same, lateral view; C—pleon, ventral view; D—telson and uropods, dorsal view; E—telson, dorsal view (median depression not indicated); F—same, detail of posterior margin, dorsal view; G—antenna, ventral view; H—left first pleopod, lateral view; I—left second pleopod, lateral view; J—right uropodal exopod, detail of distolateral margin and diaeresis, dorsal view; K—developing egg.

FIGURE 1 in Opaepupu, a new genus and species of bivalve-associated shrimp (Decapoda Caridea: Palaemonidae) from Hawai'i

FIGURE 1. Opaepupu huna gen. et sp. nov., holotype, ovigerous female (pocl 3.6 mm, cl 4.3 mm) from Kâne'ohe Bay, Hawai'i (FLMNH UF 45826): habitus, dorsal view. Both second pereiopods (chelipeds), found detached in the vial, were tentatively assigned to the female specimen and drawn as if they were in situ.

opencc-zeroDec 2013View details →

Data from: Potential effects of an invasive bivalve, Nuttallia obscurata, on select sediment attributes within the intertidal region of coastal British Columbia

On the west coast of British Columbia, Canada, the varnish clam, Nuttallia obscurata, is a rapidly spreading invasive species that can reach high densities (i.e. 800 individuals m− 2). A field survey (Tier I) and an in situ mesocosm density manipulation experiment (Tier II) were applied to determine the potential effects of this invasive bivalve on select sediment attributes within the intertidal zone. In situ experiments involved seeding 1 m2 mesocosms with varnish clams at four densities; 0 (control), 200 (low), 500 (mid) and 800 (high). Sediment samples were taken 7 times over a three week period and analyzed for organic matter, ammonium and grain size (gravel, coarse silt, fine silt and silt) at three different depths, 0–3 cm (surface), 3–6 cm (intermediate) and 6–9 cm (bottom). Field surveys demonstrated that at natural densities bivalve distribution was best explained by sediment grain size. Contrary to expectations, the in situ manipulations indicated that at high densities varnish clams did not significantly increase sediment organic matter concentrations. Their ability to deposit feed and re-ingest biodeposits may have prevented accumulations. High densities of varnish clams did however result in significantly higher concentrations of sediment ammonium and percent silt, but mostly within the lower sections of the sediment core. Reworking of the surficial sediments due to intense storm activity likely obscured any differences in determined sediment attributes among the 4 treatments. Nitrogen is a limiting nutrient with ammonium preferentially used by phytoplankton and microphytobenthos. These primary producers form the basis of all marine food webs thus increases in amounts of ammonium to shallow coastal seas as a result of high densities of an invasive bivalve within intertidal zones could result in an increased risk of eutrophication within these sensitive regions.

opencc-zeroDec 2014View details →

Data from: The effect of taxonomic corrections on Phanerozoic generic richness trends in marine bivalves with a discussion on the clade's overall history

This study uses a comprehensive, revised, and updated global bivalve dataset combining information from two major databases available to study temporal trends in Phanerozoic bivalve richness: the Sepkoski Compendium and the Paleobiology Database. This compilation results in greater taxonomic and stratigraphic coverage than possible with either of the two databases alone. However, there are challenges in directly comparing these two sources due to differences in their taxonomic designations and stratigraphic range information. Moreover, both of these datasets are fraught with a number of taxonomic errors, which can significantly bias the overall richness estimate. Additionally, a substantial number of taxonomic corrections were made before a new Phanerozoic bivalve richness curve was produced. The new generic taxonomic curve is comparable with the trajectory of the Sepkoski's modern fauna and shows rapid and substantial diversification through the Ordovician, followed by a Paleozoic plateau, a Mesozoic high, and Cenozoic diversification after a small reduction in richness associated with the K/Pg extinction. The steep Cenozoic rise documented in the raw richness curve derived from the new dataset is likely real, and reflects the overall robustness and completeness of the bivalve fossil record.

opencc-zeroDec 2013View details →

Data from: Shell ornamentation as a likely exaptation: evidence from predatory drilling on Cenozoic bivalves

Predation is an important process in modern oceans and in the evolutionary history of marine ecosystems. Consequently, it has been hypothesized that shelled prey modified their ornamentation in response to predation. However, bivalve ornamentation has also been argued to be important in maintaining a stable life position in the sediment and in burrowing. To test whether concentric ribs were effective against drilling by carnivorous gastropods, we examined drill hole position and completeness for four Cenozoic bivalve species that differ in rib strength (Astarte radiata, A. goldfussi, Lirophora glyptocyma, and L. latilirata). The percentage of drill holes located between the ribs increases with increasing rib strength, whereas the percentage of drill holes on top of ribs decreases. This result suggests that gastropods select the drill hole site more effectively as rib strength increases, thereby saving time and energy, and that natural selection favors gastropods that select drill hole sites between ribs. Because of this greater stereotypy, the percentage of drill holes that are incomplete is generally lower in strongly ribbed species. The proportion of drill holes located on top of ribs is greater for incomplete than complete holes, implying that ribs can be effective against predators, but only when selected as the drilling location. We show that ribs are most effective against drilling predation for bivalves with moderately sized ribs, between which gastropods have difficulty siting drill holes. Concentric ribs are unlikely to have evolved as an adaptation against drilling predation because concentric ribs evolved in the Paleozoic and were already common in the Mesozoic, whereas drilling frequency increased later, in the Late Cretaceous–Paleogene. Moreover, rib strength of North American Astarte did not change through this time interval. Thus, the ribs considered here are a likely exaptation to drilling given their effectiveness at deterring drilling predation on bivalves with moderate ribs.

opencc-zeroDec 2015View details →

Data from: Anchors and snorkels: heterochrony, development and form in functionally-constrained fossil crassatellid bivalves

New growth-rate estimates for nine species from three genera of New Zealand Crassatellidae (Mollusca; Bivalvia), combined with existing morphometric ontogenetic descriptions, allow identification of heterochronic processes in the evolution of these genera. Both paedomorphosis (progenesis and neoteny) and peramorphosis (hypermorphosis and acceleration) have occurred within the clade. Overall, morphological variability and response to environmental pressure in this non-siphonate group is restricted by the interplay of anatomical and life-habit constraints. Stability in the substrate, predator avoidance, sluggish burrowing speed and inability to escape by deep burial are suggested as key drivers of, or constraints on, morphological change. Two groups of shell characters are identified: heavy, armoured "anchors" and elongate "snorkels", which combine juvenile and adult traits in shells of different sizes and ages, produced by heterochronic variation in developmental timing. Anchors and snorkels both represent different 'solutions' to the problems of life as a non-siphonate, infaunal bivalve.

opencc-zeroDec 2011View details →

Data from: Genetic architecture in a marine hybrid zone: comparing outlier detection and genomic clines analysis in the bivalve Macoma balthica

The role of natural selection in speciation has received increasing attention and support in recent years. Different types of approaches have been developed that can detect genomic regions influenced by selection. Here we address the question whether two highly different methods - Fst outlier analysis and admixture analysis - detect largely the same set of non-neutral genomic elements or, instead, complementary sets. We study genetic architecture in a natural secondary contact zone where extensive admixture occurs. The marine bivalves Macoma balthica rubra and M. b. balthica descend from two independent trans-Arctic invasions of the north Atlantic and hybridize extensively where they meet, for example in the Kattegat - Danish Straits - Baltic Sea region. The Kattegat - Danish Straits region forms a steep salinity cline and is the only entrance to the recently (ca 8000 years ago) established brackish water basin the Baltic Sea. Salinity along the contact zone drops from 30‰ (Skagerrak, M.b.rubra) to 3‰ (Baltic, M.b.balthica). Both outlier analysis and genomic clines analysis suggest that large parts of the genome are influenced by non-neutral effects. Contrasting samples from well outside the hybrid zone, outlier analysis detects 16 of 84 amplified fragment length polymorphism (AFLP) markers as significant Fst outliers. Genomic clines analysis detects 31 out of 84 markers as non-neutral inside the hybrid zone. Remarkably, only three markers are detected by both methods. We conclude that the two methods together identify a suite of markers that are under the influence of non-neutral effects.

opencc-zeroDec 2017View details →

Data from: Is biodiversity energy-limited or unbounded? A test in fossil and modern bivalves

The quantity of biomass in an ecosystem is constrained by energy availability. It is less clear, however, how energy availability constrains taxonomic and functional diversity. Competing models suggest biodiversity is either resource-limited or far from any bound. We test the hypothesis that functional diversity in marine bivalve communities is constrained by energy availability, measured as particulate organic carbon (POC) flux, in the modern oceans. We find that POC flux predicts the relative prevalence of ecological modes in both the Atlantic and Pacific oceans. Moreover, the associations of ecological modes with POC fluxes are similar between the Atlantic and Pacific despite being based on independent sets of species, indicating a direct causal relationship. We then use the relationship between POC flux and the prevalence of functional groups in the modern to test the hypothesis that the trend of increasing functional diversity in bivalves across the past 500 million years has occurred in response to increased POC flux. We find no evidence that the earliest appearing modes of life are preferentially associated with low POC environments or that the mean POC flux experienced by marine bivalves has increased across geological time. To reconcile the close association between ecological mode and POC flux in the modern oceans with the lack of evidence for increasing POC fluxes across time, we propose that POC flux has not increased substantially over time but, rather, the increase in bivalve functional diversity enabled bivalves to become more abundant, to occupy a broader range of environments, and to capture a greater fraction of the total POC flux. The results here suggest at geographic scale of oceans and through geologic time bivalve diversity was not bounded by food availability.

opennotspecifiedDec 2006View details →

FIGURE 13 in A new deepsea pectinid bivalve from thermal vents of Manus backarc Basin (southwestern Pacific), Sinepecten segonzaci n. gen., n. sp. (Pectinoidea: Pectinidae), and its relationships with the genera Bathypecten and Catillopecten

FIGURE 13. Pattern of byssal notch morphogenesis in extant Pectinids displaying different mode of life (not to scale). 1–3: first successive ontogenetic stages exemplified by juveniles of Pecten maximus (1: postlarval; 2: without ctenolium; 3: with ctenolium); a–g: adults, byssally fixed (a–d), freeliving (f–g), or both (e); ct: ctenolium; P: prodissoconch. a: Bathypecten vulcani; b: Sinepecten segonzaci; c: Hemipecten forbesianus; d: Chlamys varia; e: Aequipecten opercularis; f: Pecten maximus; g: Propeamussium watsoni. Thick black arrows indicate ontogenetic trajectories. Thin arrows outline the main growth allometries (parallel to commissure plan only) around byssal notch. For (b), crosses indicate place of byssal notch covered by its ventral edge and thus invisible (see Figure 6). Black anterior auricle of (f) corresponds to stage 3.