Taxonomic and Biological Remarks on Thyasira gouldii (Philippi, 1845) in Eastern Canada and Reinstatement of the Species Thyasira plana (Verrill and Bush, 1898)

Within the bivalve family Thyasiridae, symbioses with chemoautotrophic, sulphur-oxidizing bacteria do not occur in all lineages; variation in symbiont presence and in the degree of abfrontal expansion of gill filaments occurs on fine phylogenetic scales within the family. Thyasirid symbionts are harboured extracellularly and are periodically engulfed and digested by host gill epithelial cells. Symbiotic thyasirids are mixotrophic, retaining the capacity to feed on particulate matter; the relative importance of particulate feeding and symbiont-derived nutrition to host metabolism may vary on temporal and spatial scales depending on the abundance of particulate organic matter and sediment sulphide availability. Here, we demonstrate the existence of a temporal trend in symbiont abundance in Thyasira cf. gouldi from Bonne Bay, Newfoundland, Canada, over 18 months (2011 and 2012): symbiont abundance is highest during the months of autumn and is lowest in spring. The density of membrane whorls, lysosomal microbodies associated with the digestion of bacterial symbionts, does not display a similar temporal trend, indicating that relationships between the contribution of symbiont-derived nutrition and seasonal fluctuations in environmental parameters are less clear. Along with the extracellular status of thyasirid symbioses, their highly dynamic nature may explain the possible evolutionary loss or gain of chemosymbioses among some members of this group.

Understanding the extent to which traits that are used to delimit and diagnose species are phenotypically plastic is important for recognizing species boundaries. Shell characters have long been used for describing species of gastropods, even though these features may be influenced by environmental conditions. To determine the degree of phenotypic plasticity of two North American lymnaeid species, Stagnicola elodes (Say, 1821) and Stagnicola emarginata (Say, 1821), that occur in different habitats and differ in shell morphology, we reared individuals in captivity under similar conditions and compared shell shapes and sizes of wild-caught and captive-reared populations. We also exposed individuals of S. elodes to effluent from a potential predator (crayfish) to gauge the possible impact of the presence of predators on shell morphology. Although the two species remained morphologically distinct, shell shapes of captive-reared individuals of both species differ significantly from those of wild-caught individuals and show similar magnitudes of change among species. Directions of change, however, differed significantly among species. Although shell shapes of individuals of S. elodes that were exposed to crayfish cues were not significantly different from control snails, shell sizes of exposed snails were smaller than unexposed snails. These results suggest that exposure to predators affects growth rates of S. elodes. Nonetheless, given significant associations between shell shape and size that were observed in the captive-rearing and predator-exposure experiments, shell shape changes allometrically during development. These results suggest that morphological differences of other North American Stagnicola species reflect ecophenotypic variation, but more work is necessary to further evaluate this hypothesis.

Comparative study of reproductive synchrony at various scales in deep-sea echinoderms

Submarine slope failures in the nearshore waters of SE Baffin Island, eastern Canadian Arctic, present a challenge to coastal and seabed development. Submarine slope failures are a known geohazard in fjords in Norway, Chile, Alaska, British Columbia and elsewhere, but have received little attention in the coastal waters of Arctic Canada. Over the past 6 years, there has been a rapid expansion of multibeam echosounder (MBES) mapping in Canadian Arctic fjords, leading to the discovery of many submarine slope failures. One area that has been mapped in detail is inner Frobisher Bay. This macrotidal, seasonally ice-covered, semi-enclosed embayment has a glacially scoured bed, ice-contact deposits, including recessional moraines, and stratified glaciomarine and post-glacial silts and clays with abundant dropstones. The prevalence of submarine slope failures in the inner bay (one per 20 km 2 ) appears to be anomalous. To date, MBES mapping has imaged at least 246 failures, ranging in size from 0.007 to 2.1 km 2 and all within the glaciomarine and post-glacial succession. Morphometric analysis of these features based on high-resolution MBES bathymetry provides an insight into their spatial distribution, relative chronology, triggers and flow characteristics; factors essential to understanding the mechanisms underlying their abundance in this Canadian Arctic fjord.

The Phantom Cave snail (Cochliopa texana), a little-studied rissooidean gastropod that is locally endemic within the lower Pecos River basin (Texas) and currently a candidate for addition to the Federal list of threatened and endangered species, is redescribed and transferred to the hydrobiid genus Pyrgulopsis, based on shell and anatomical characters. Specimens from the type locality (Phantom Lake Spring) and San Solomon Spring are larger than those from East Sandia Spring and also differ somewhat in shell shape and shape of the central cusps of the lateral radular teeth. However genetic (mtCOI, NDI) variation within and among these geographically proximal (6– 13 km) populations was slight, providing no basis for the recognition of distinct conservation units of this imperiled species. We also describe Pyrgulopsis ignota n. sp., which was recently discovered in a different part of the lower Pecos River basin and initially confused with the Phantom Cave snail. These two species differ in shell shape, operculum morphology, and form and glandular ornament of the penis. They are also strongly differentiated genetically from each other and from (13) other regional congeners ( pairwise sequence divergence .6.3% for both genes). A Bayesian phylogenetic analysis of the COI and NDI dataset indicated that these two snails are not closely related and that P. ignota occupies a basal position relative to other regional congeners.

The marine gastropod Littorina saxatilis has different ecotypes in shores only a few meters apart. This has both taxonomic and evolutionary implications. Here we report on an extreme type of within-shore dimorphism in shell characters. In the wave-exposed rocky shores in northwestern Spain, we found one form of L. saxatilis in the upper-level barnacle zone. It had a white, ridged shell, with black bands in the grooves. Another form confined to the lower-shore mussel belt had a smooth shell that was either white and tessellated or darkly colored. These two forms cooccured in a narrow midshore zone together with individuals that had combined characters, but were present in low frequencies (11%-29%). We used principal-component analysis of metric shell characters to study variation in shell size and shape. We found that the upper-shore form was larger than the lower-shore form. We also found small but significant differences in shell shape. Experiments in a common laboratory environment suggested the differences in shell ornamentation and color are inherited, but the individuals did not develop the morph-specific characters until a shell height of about 3 mm. The occurrence of mainly two distinct forms may suggest the presence of two species that hybridize. An analysis of five polymorphic enzyme loci in populations of snails from three geographically separated sites indicated, however, that there was no positive correlation between morphological distances and genetic distances among populations on a geographic scale (tens of kilometers). Thus, we rejected the hypothesis of two species. However, on a microgeographic scale (meters), genetic differentiation between groups with the same form was less than differentiation between forms. This indicated a partial barrier to gene flow between the two forms, and preliminary mate choice data suggested this was caused by nonrandom mating in the midshore zone of overlap.

Antibiotic resistance (AR) is a growing health concern worldwide and the Arctic represents an understudied region in terms of AR. This study aimed to quantify AR genes (ARGs) from effluent released from a wastewater treatment plant (WWTP) in Iqaluit, Nunavut, Canada, thus creating a baseline reference for future evaluations. Water, sediment, and truncate softshell clam ( Mya truncata) tissue samples were compared from the wastewater, the receiving environment of Frobisher Bay, and nearby undisturbed freshwaters. The pharmaceuticals and personal care products (PPCPs) atenolol, carbamazepine, metoprolol, naproxen, sulfapyridine, and trimethoprim were found in the wastewater, but the PPCPs were undetectable in the receiving environment. However, the relative abundances of ARGs were significantly higher in wastewater than in the receiving environment or reference sites. Abundances did not significantly differ in Frobisher Bay compared to undisturbed reference sites. ARGs in clams near the WWTP had similar relative abundances as those from pristine areas. The lack of ARG detection is likely due to Frobisher Bay tides flushing inputs to levels below detection. These data suggest that the WWTP infrastructure does not influence the receiving environment based on the measured parameters; more importantly, further research must elucidate the impact and fate of AR and PPCPs in Arctic communities.

Long-term studies provide an effective way to assess the ecological impacts of decades-long environmental change in Arctic coastal benthic environments, but are rarely undertaken in the Canadian Arctic. In light of this, historical datasets can be compared with modern samples to examine temporal differences in benthic community structure. Frobisher Bay, Nunavut, provides a unique opportunity to use a historical census to examine the impacts that long-term environmental changes have had on the marine benthos. Between 1967 and 1976, and in 2016, infaunal samples were collected in inner Frobisher Bay and were compared to determine how the molluscan assemblages have changed between the two time periods. Molluscan assemblages in two regions of inner Frobisher Bay (Iqaluit and Cairn Island) were examined to minimize sampling discrepancies between the two time periods. A long-term increase in mean annual air temperature and a decline in the length of the ice cover season were observed. Both regions exhibited some change in sediment composition and quality as well as in molluscan assemblage between the two time periods, and species diversity indices also indicated some change between these time periods. Both the 1967–1976 and 2016 molluscan datasets provide a baseline for future long-term studies in a changing Arctic.

Introduction: The gastropod Bostryx torallyi shows high variability in shell shape and coloration. Subspecies of this organism have been described based on shell characters but, since they were slightly different, they were synonymized afterwards. Until now, shell variability has been analyzed only descriptively and its anatomy is still unknown. Objective: In this study, I provide anatomical information of B. torallyi and apply a geometric morphometric analysis to evaluate the shell shape variation among specimens. Methods: To accomplish this, type material and numerous lots were examined and dissected out. Additionally, relative warp analysis, based on 9 landmarks in ventral view of the shell, was performed using 80 specimens of 9 localities from Bolivia and Argentina. Results: According to our results, geometric morphometrics is a suitable method to evaluate differences in shell shape among localities; for instance, distinctions in the shell were noticeable between gastropods of low and high altitudes. On the other hand, it was established that the coloration of this species is independent of large-scale factors since the examined specimens came from environments with similar conditions. Furthermore, the sculpture of the protoconch and anatomy of B. torallyi coincided with the other Argentinian species of the genus. Conclusions: Therefore, I concluded that a geometric morphometric analysis of shell shape is a good complement to traditional qualitative description of the characteristics of the shell in this species.

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Leptopoma is a species rich genus with approximately 100 species documented according to shell morphology and animal anatomy. Many of the Leptopoma species are described in terms of shell size, shape, sculpture and colour patterns of a small number of examined materials. However, the implications of the inter- and intra-species variations in shell form to the taxonomy of Leptopoma species and the congruency of its current shell based taxonomy with its molecular phylogeny are still unclear. Over the last decade, more than 900 collection lots consisting of more than 4000 Leptopoma specimens have been obtained in Sabah and deposited in BORNEENSIS at Universiti Malaysia Sabah. Access to this collection gave us the opportunity to examine the geographical variations in shell forms and the phylogenetic relationship of Leptopoma species in Sabah. The phylogenetic relationship of three Leptopoma species was first estimated by performing maximum likelihood and Bayesian analysis based on mitochondrial genes (16S and COI) and nuclear gene (ITS-1). After this, a total of six quantitative shell characters (i.e. shell height, shell width, aperture height, aperture width, shell spire height, and ratio of shell height and width) and three qualitative shell characters (i.e. shell colour patterns, spiral ridges, and dark ring band in aperture) of the specimens were mapped across the phylogenetic tree and tested for phylogenetic signals. Data on shell characters of Leptopoma sericatum and Leptopoma pellucidum from two different locations (i.e. Balambangan Island and Kinabatangan) where both species occurred sympatrically were then obtained to examine the geographical variations in shell form. The molecular phylogenetic analyses suggested that each of the three Leptopoma species was monophyletic and indicated congruence with one of the shell characters (i.e. shell spiral ridges) in the current morphological-based classification. Other qualitative and quantitative shell characters were incongruent with the Leptopoma species phylogeny. Although the geographical variation analyses suggested some of the shell characters indicating inter-species differences between the two Leptopoma species, these also pointed to intra-species differences between populations from different locations. This study provides an initiation to resolve the taxonomy conundrum for the remaining 100 little known Leptopoma species from other regions and highlights a need to assess variations in shell characters before they could be used in species classification.

Most species of freshwater mussels (Unionoida) show a wide variability in shell form and size but an understanding of which factors determine unionoid morphology is poor. We identified ecophenotypic trends in shell and internal characters within three unionoid species from two habitat types (marinas and river) of the River Thames, UK, using traditional and modern morphometric techniques. In marinas, all species grew to larger maximum sizes than in the river, which might be a result of higher temperatures and phytoplankton densities in marinas. Unio pictorum in marinas was more elongated than in the river and Fourier shape analysis revealed a trend from dorsally arched river specimens to straight dorsal and pointed posterior margins in marina individuals. The degree of shell elongation and shape of dorso-posterior margin were not associated with sediment composition, but were associated with the different hydrological characters of the two habitat types. Relative shell width was a poor indicator of collection site and influenced by allometric growth. Unlike U. pictorum, a difference in shell elongation of marina and river mussels could not be detected in Unio tumidus and Anodonta anatina. However, all three species showed the same trends regarding the shape of the dorso-posterior shell margin. This shell character may thus have broad ecological significance and could have considerable utility to palaeontologists, taxonomists, and conservation biologists.

How an embryo develops its particular form during ontogeny and how shape changes through evolutionary time are two closely linked questions. An approach to these issues, mainly inspired by D'Arcy Thompson's work, is to highlight the 'laws of form', that is how developmental systems determine the variation of organismal forms on short and long time scales. During the last decades, theoretical models of morphogenesis have allowed the identification of some of these rules from experimentally well-studied developmental systems. Molluscs are also well suited to address the relationships between evolution and development. The preservation of the ontogeny of the shell due to its accretionary growth and the excellent fossil record in this group are undeniable advantages. Also, molluscan shell shape and growth have been the focus of extensive theoretical work, revealing the regularity of accretionary growth which often conforms well to logarithmic spiral coiling. The study of evolutionary changes occurring in mollusc lineages relies nearly exclusively on the interpretation of shell morphologies. Important taxonomic features of molluscs include the shape of the aperture, the degree of coiling of the shell tube, the ornamentation (ribs, tubercles, spines, keels) and growth features (growth halts, constrictions, varices). The evolution of the molluscan shell is characterized by frequent convergences in form and ornamentation. As a consequence, the recognition of transformation of one shape into another crucially depends on the knowledge of how these shell shapes are generated. The comparison between different clades of molluscs can be informative with regards to the basic rules of accretionary growth. In particular, it has been pointed out that common rules of accretionary growth could underlie the morphogenesis of the shell and its evolution in ammonoids and gastropods. Evidences come from the comparison of intraspecific patterns of covariation between shell characters, from the examination of growth changes occurring at maturity and from the analysis of teratological shells with malformations caused by injuries or change in living conditions in both clades. In some highly variable ammonoids species, it has been shown that simple growth rules could underlie the evolutionary recurrent covariation of aperture shape, degree of coiling and intensity of the ornamentation (Buckman's law of covariation). Similarly, these characters covary with the spacing between growth halts during the ontogeny of some ammonoids species. A central objective of this thesis is to investigate what kinds of generic rules could produce the patterns of variation of molluscan shell shape. In a first part, it is discussed how generic models can inform us about the generation and evolution of structures of particular size and shape. In a second part, a null hypothesis model of shell growth is proposed. The intricate relationships between growth rate and allometry are described. The kind of morphological variation expected given these basic growth rules is compared to experimental evidence in developmentally plastic shells of intertidal gastropods. A population of recent gastropods (Hexaplex trunculus, Muricidae), originated from a single egg mass and bred in laboratory for about a year and a half is used to describe the ontogenetic patterns of covariation between shell characters and the dynamics of growth. This study highlights a covariation between growth rhythm (frequency and amplitude of pulses of growth), growth halts spacing, aperture allometry and intensity of ornamentation. In particular, variation in growth rhythm is regarded as critical in generating the observed covariation between growth halts spacing and ornamentation. A simple growth model is proposed to account for the integration of the covariation of these shell characters. Some recurrent patterns of variation in ammonoids species could result from similar rules tied to basic constraints of accretionary growth. The theoretical and empirical framework developed here can assist in formulating and testing new hypotheses of growth of molluscan shells. It paves the way toward the development of data-driven mathematical models which could facilitate the comparison of theoretical and empirical data in the future, and perhaps helps interpreting them in a developmental, ecological or evolutionary context. More generally, this dissertation argues that the time parameter is mandatory to the study of allometry, if one seeks to understand the relationships between size and shape and how they vary in populations.

Thick-billed murres (Uria lomvia) originating from breeding colonies in the Canadian Arctic were collected on their wintering grounds off the coast of Newfoundland. Murres had been previously banded such that the age of each bird could be determined upon collection. This allowed us to explore the possible relationships between age and contaminant levels in the thick-billed murre. Samples of breast muscle were analyzed for organochlorines (chlorobenzenes, hexachlorocyclohexanes, DDTs, chlordanes, mirex, dieldrin, and PCBs) and metals (selenium, cadmium, mercury, and lead). Levels of both organochlorine and metal residues were sufficiently low so that toxic effects were unlikely. First-year birds contained lower levels of DDTs, mirex, dieldrin, and PCBs compared with older birds, reflecting lower levels of contamination of these compounds in food chains at breeding colonies located at higher latitudes. Higher levels of chemical residues in older birds may reflect greater direct input of those organochlorines into the wintering grounds via the highly contaminated St. Lawrence River. Levels of chlorobenzenes, hexachlorocyclohexanes, and chlordanes, which reflect atmospheric deposition, were not detected at higher levels in older birds. Of the metals, only cadmium was detected at higher levels in older birds.

A distinct fauna consisting mainly of nematodes, harpacticoid and cyclopoid copepods, rotifers, turbellarians and polychaete larvae, inhabits the lower levels of the sea ice in Frobisher Bay. Similar faunas are found throughout circumpolar regions. Thirteen taxa of the Frobisher Bay ice fauna were entirely herbivorous. Their food consisted of 26 genera of algae dominated by Chlamydomonas, Nitzschia, Navicula and Chaetoceros. There was a clear tendency to feed on the most abundant ice algae, hence little evidence of selective feeding. High algal food concentrations in the ice (estimated at 5000 μg C/l) were in sharp contrast with the scant nourishment available from phytoplankton under the ice (8 μg C/l) from mid-winter until the start of the summer bloom. Algal stocks and estimated productivity rates indicate that ice meiofaunal food requirements may be met by the ice algae. All the major ice meiofaunal species are well adapted to feeding within the ice. All are small enough to enter brine channels and secure particulate prey from surfaces within confined spaces. The ice meiofaunal species are major consumers of the ice algae and therefore important links in the transfer of energy from the ice to pelagic and benthic predators, including fishes, birds and mammals.