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Four species new to science were identified in the Tellinidae museum collections in the Marine Biological Museum of Chinese Academy of Sciences. Pinguitellina triquetra sp. nov., collected in 1981, has not previously been described or reported. It differs from other Pinguitellina species by its trigonal shape, rose-colored valve interior, and deep and wide pallial sinus, which is confluent with the pallial line. Pinguitellina protuberangla sp. nov. has a broad and deep dorsal corner, short and straight posterodorsal margin, comparatively large adductor scars, depressed and fragile shells, and deep socket at the anterior edge of the right valve. Pinguitellina minuta sp. nov. was previously misidentified as Arcopella casta in China. It is a new species based on its unique characteristics, which include small, fragile, inflated, translucent, and triangularly ovate-shaped shells with acuminated and convex umboes. As the first species described in China within the genus Abranda Iredale, 1924, Abranda xui sp. nov. has internal ligaments and thin, fragile, and translucent elliptical shells with fine radials on the surface. In this study, we reorganized the species currently contained in the two genera Pinguitellina and Abranda and created keys to the known species. We believe that numerous collected bivalve specimens have been overlooked in the South China Sea, and to date, mollusk has not been adequately sampled. Thus, further exploration and analysis are required to understand species diversity in this area. [ABSTRACT FROM AUTHOR]

Both genetic and environmental factors affect the morphology of oysters. Molecular identification is currently the primary means of species identification, but it is inconvenient and costly. In this research, we evaluated the effectiveness of geometric morphometric (GM) techniques in distinguishing between two oyster species, Crassostrea gigas and C. ariakensis. We used traditional morphometric and GM methods, including principal component analysis (PCA), thin-plate spline analysis (TPS) and canonical variable analysis (CVA), to identify specific features that distinguish the two species. We found that differences in shape can be visualised using GM methods. The Procrustes analysis revealed significant differences in shell morphology between C. gigas and C. ariakensis. The shells of C. ariakensis are more prominent at the widest point and are more scattered and have a greater variety of shapes. The shells of C. gigas are more oval in shape. PCA results indicated that PC1 explained 45.22%, PC2 explained 22.09% and PC3 explained 10.98% of the variation between the two species, which suggests that the main morphological differences are concentrated in these three principal components. Combining the TPS analysis function plots showed that the shell shape of C. ariakensis is mainly elongated and spindle-shaped, whereas the shell shape of C. gigas is more oval. The CVA results showed that the classification rate for the two species reached 100% which means that C. ariakensis and C. gigas have distinct differences in shell morphology and can be completely separated, based on morphological characteristics. Through these methods, a more comprehensive understanding of the morphological characteristics of different oyster populations can be obtained, providing a reference for oyster classification and identification. [ABSTRACT FROM AUTHOR]

Background: Amongst the genus Rumina, R. paivae was decribed from North Africa for the first time by Lowe in 1861 on the basis of a limited number of samples. During the 19 and 20 centuries, it was described several times, under different names and different ranks leading to a taxonomic imbroglio before being forgotten. In 2002, Mienis rehabilitated R. paivae, but Prevot et al. (2013, 2014) considered it as a large phenotype of R. decollata Linnaeus (1758) on the basis of genetic and anatomical studies. New information: In this study, we present morphological and anatomical comparisons and differences between two groups of shells collected in France and considered as R. decollata. Using seven morphological characters related to the size and one to the microscopic sculptures of the shell and two related to the eggs and the colours of the morphs, we attribute these two groups to two morphologically described species: R. paivae and R. decollata. We propose a way to easily distinguish them from each other. With regard to their distribution, morphology and genetics, we discuss their relative systematic position. Moreover, in this study, we report for the first time R. paivae, a given north African taxa, in the south-ast of France, in Marseille. [ABSTRACT FROM AUTHOR]

The platycerate gastropods Orthonychia yutaroi Ebbestad, sp. nov. (Ordovician, Boda Limestone, Sweden), O. enorme (Silurian, Sweden, Gotland), O. parva (Pennsylvanian, Finis Shale Member, USA), and Orthonychia sp. (Mississippian, Imo Formation, USA) are studied including their protoconch morphology. Orthonychia yutaroi is the oldest known species in Orthonychia. Platycerates contain species with both, openly and tightly coiled protoconchs. This is the first report that tightly coiled protoconchs occur in Orthonychia. This and previously published observations blur the diagnostic difference between orders Cyrtoneritimorpha (openly coiled protoconch) and Cycloneritimorpha (tightly coiled protoconch). We suggest to treat Cyrtoneritimorpha and Cycloneritimorpha as synonyms of Neritimorpha. The monotypic Devonian genus Pragoserpulina is morphological so close to the Orthonychia species reported herein that synonymy of both genera seems to be possible (and thus of the families Pragoserpulinidae and Orthonychiidae). Protoconch morphology and dimensions suggest that the studied platycerate species had planktotrophic larval development. By contrast, two studied Carboniferous euomphaloid species (one with an openly and the other with tightly coiled protoconch) have paucispiral, large protoconchs indicating non-planktotrophic larval development. We assume that openly and tightly coiled protoconchs were present in various Paleozoic gastropod clades and that selection acted against the openly coiled protoconch morphology. It has previously been proposed that increasing predation pressure in the plankton was the reason for the demise of openly coiled protoconchs (Paleozoic plankton revolution). The presence of larval planktotrophy in platycerates excludes the possibility that they belong to extant basal gastropod clades such as Patellogastropoda, Cocculiniformia, and Vetigastropoda. However, a previously proposed close relationship to Neritimorpha is corroborated. [ABSTRACT FROM AUTHOR]

This study was designed to investigate about species diversity of soil mollusks in Shemiranat county. The country was divided into 10 sampling stations and the collected samples were identified morphologically and systematically according to the certified identification keys. Results showed the significant effect of temperature and relative humidity on the abundance of the soil mollusks. There were no samples collected in cold months, but in warm seasons, August had the most numerous samples, and March showed the lowest abundance. In this study, a total of 94 samples belonging to 10 species under 9 genera and 8 families were identified as follows: Helix lucorum (Helicidae), Cernuella neglecta, Monacha cantiana and M. parumcincta (Hygromidae), Succinea putris (Succineidae), Chondrula tridens (Enidae), Planorbis intermixtus (Planorbidae), Deroceras tritulatum (Agriolimacidae), Ambigolimax valentianus (Limacidae) and Arion fuscus (Arionidae). P. intermixtus was the most abundant species among the collected samples and S. putris had the lowest density. [ABSTRACT FROM AUTHOR]

Eleven coastal geographical populations of wild Cyclina sinensis in China were collected in February 2020, and the effects of four morphological traits (shell length; shell height; shell width; external ligament length) on one weight trait (living body weight) were studied by correlation analysis, path analysis, determination coefficient analysis, and regression analyses. The statistical results showed that the coefficient of body weight variation was generally greater than morphological traits(P"0.05). The correlation analysis results showed that the coefficient of correlation between morphological traits (except for external ligament length) and body weight are significantly positive (P"0.05) in all populations. Based on the results of path analysis and determination coefficient analysis, shell length has the greatest direct effect on body weight in the Yancheng population; shell height has the greatest direct effect on body weight in Dandong, Fuzhou and Tangshan populations; shell width has the greatest direct effect on body weight in Zhanjiang, Wenzhou, Dongtai, Ningbo, Tianjin, Dongying, and Wanning populations. Multiple regression equations were obtained with body weight as the dependent variable, shell length, height, and width and external ligament length as independent variables. The results of systematic clustering showed that there are no apparent geographical differentiation characteristics among eleven geographical populations in morphology. This study provided a scientific basis for selective and genetic breeding and can guide the development and utilization of wild C. sinensis seed resources. [ABSTRACT FROM AUTHOR]

Nacre—a biological composite of alternating layers of aragonite platelets and organic matrices, derived from biomaterials like molluscan shells has recently attracted a lot of interest as a potential substitute for ceramic material in orthopedic tissue engineering. It is formed as a result of interesting biomineralization processes. Molluscs use a striking variety of structural motifs to build their shells composed of calcium carbonate and a small percentage of proteins. These integral proteins determine the structural organization and properties of the mineralized composite. However, the composition and thermal stability of these proteinous matrices remains a mystery. Until now it was presumed that the organic matrix in a shell degrades completely up to 500 °C (stage―I). Stage―II comprises degradation of CaCO 3 to CaO spanning about 600 °C to 850 °C. However, in case of a gastropod mollusc shell of Neverita josephinia , stage―III was also observed, in which majority weight loss of core organic proteinous matrix (OPM) exceeding 6 wt%, starts after about 1000 °C of thermal heating. It is observed that the core organic matrix (OM) has varied composition throughout the shell, stronger bonding, complex topology and has very high thermal resilience even up to 1400 °C. Simultaneous analysis of evolved gases by FTIR spectrometer coupled with thermogravimetric analyzer shows the composition of non-mineral species is more than 8 wt%. The results are supported by room temperature as well as gas phase by FTIR spectroscopy, XRD, SEM, CHNS analyses. The XRD spectra of the pristine shell powder and that calcined at 550 °C reveal aragonite to calcite phase transformation in calcium carbonate. The SEM shows the cross-lamellar morphology of the gastropod mollusk shell. There are two different sets of organic matrices: one with complex topology and a very tight binding to the mineral components (intra-crystalline), and the other with a loose binding to the mineral (inter-platelet area). Elemental analysis (CHNS) data, also supports this. This study identifies that the organic matrix, comprising proteins, peptides, lipids, and carbohydrates, exhibits complex topology and strong mineral bonding, contributing to the shell's notable mechanical strength and resistance to thermal degradation. The implications of this high thermal resilience for the shell's mechanical properties and potential biomineralization processes are discussed, suggesting a reevaluation of the organic matrix's role in molluscan shells. [Display omitted] • Simultaneous TG―FTIR analysis of the molluscan gastropod shell of N. josephinia was demonstrated. • Stage―III also was observed in the TG curve, with over 6% weight loss due to core organic proteinous matrix (OPM). • Results show very special bondings of organics with minerals or even with calcium, contributing towards very high thermal resilience. [ABSTRACT FROM AUTHOR]

Background: Despite their large size, striking colouration and genital extravagance, the taxonomy of the European giant keelback slugs of the genus Limax is still poorly understood. Preliminary morphological and molecular data suggest that many unnamed or unrecognised species exist, especially in the Alps, the Mediterranean and the Balkans. We organised a citizen science expedition to Durmitor National Park in Montenegro and discovered a new species, genetically distinct, but morphologically similar to the sympatric L. cinereoniger Wolf 1803 and describe it as L. pseudocinereoniger. [ABSTRACT FROM AUTHOR]

In this paper, a live hectocotylus, found inside a stranded female Argonauta argo shell, allowed us to describe the behaviour of this copulatory arm and add new information on its morphology. The hectocotylus penile filament is contained in a special membranous pocket or sac, almost completely transparent, extending from the apex of the basal part to about one-third of the central section. The hectocotylus assumes a folded position to protect the penile filament in the membranous sac. This is probably extracted only when copulation occurs. Our observations seem to suggest that the shell may have the secondary function of storing and protecting the hectocotyli received by males until the copulation. The observations confirmed the high vitality and endurance of the hectocotylus after detachment from the A. argo male. [ABSTRACT FROM AUTHOR]

Background In Morocco, many uncertainties surround the current diversity and distribution of the bivalve family Sphaeriidae. Such information, including taxonomy and conservation status, are vital for further studies to improve the knowledge of this family in Morocco and represents the first step towards the development of a national conservation plan for all freshwater bivalves. Between 2016 and 2019, several investigations were carried out to assess the diversity and distribution of Sphaeriidae in the different basins of Morocco, covering different types of habitat (lakes, springs, rivers and small ponds). The identification of specimens and their morpho-ecological features was based on morphological and morphometric analyses. The data on the general distribution of the collected species allowed the evaluation of their conservation status as well. The shell morphology and morphometric analyses revealed the existence of five species belonging to the genus Pisidium [P. casertanum (Poli, 1791), P. (cf.) personatum Malm, 1855, P. subtruncatum Malm, 1855, P. amnicum (O. F. Müller, 1774) and Pisidium sp.] and one species to the genus of Musculium [M. lacustre (O. F. Müller, 1774)]. Sphaeriidae were found in all Moroccan basins, except Bouregreg and Sakia El Hamra-Oued Eddahab Basins. The results showed that Sebou Basin was the species richest with the occurrence of the five species, while Loukkos and Sous-Massa Basins had the lowest-species richness with one species only. The conservation status of sphaeriids in Morocco was evaluated for the first time and resulted in P. (cf.) personatum and P. subtruncatum being proposed as Least Concern and Vulnerable, respectively, while the status of Regionally Extinct is suggested for both species P. amnicum and M. lacustre. New information First evaluation of the diversity and species richness of the family Sphaeriidae in Morocco with an assignment of an updated conservation status of the recorded species. [ABSTRACT FROM AUTHOR]

The gastropod Rapana venosa (Valenciennes, 1846) is a successful worldwide invader occurring in the Black Sea. The aim of this study is to overview specific population features of this mollusk from Odesa Bay through integrative systematic approach by means of morphological and molecular research. For this purpose, the mollusks were collected from the Black Sea and examined using morphological methods: traditional morphometry, which employs linear parameters of shells (height, width, whorl height, whorl width, height of the last whorl) and shell weight, and geometric morphometrics of the shell shape data. For a molecular genetic test, the COI gene region was used. Among all conchological variability, the two morphotypes were defined: the first has a "broad" shape -- shells have a thick and durable last whorl and a low spire, and the second one -- "extended" shape: shells are relatively slender with an elongated high-conical spire. According to the geometric morphometric data, R. venosa has statistically significant differences between defined morphotypes (F = 4.12, p = 0.001); however, the shapes in males and females are not significantly different (F = 1.13, p = 0.318). No genetic diversity, neither novel haplotypes were revealed by the molecular analysis: in Odesa Bay, the haplotype occurring also in other regions of invasion across the world is present. [ABSTRACT FROM AUTHOR]

Micro-computed tomography (micro-CT) is a high-resolution 3D-imaging technique which is now increasingly applied in biological studies focusing on taxonomy and functional morphology. The creation of virtual representations of specimens can increase availability of otherwise underexploited and inaccessible samples. The 3D model dataset can be also further processed through volume rendering and morphometric analysis. The success of micro-CT as a visualisation technique depends on several methodological manipulations, including the use of contrast enhancing staining agents, filters, scanning mediums, containers, exposure time and frame averaging. The aim of this study was to standardise a series of micro-CT scanning and 3D analysis protocols for a marine gastropod species, Hexaplex trunculus. The analytical protocols have followed all the developmental stages of this gastropod, from egg capsules and embryos to juveniles and adults. [ABSTRACT FROM AUTHOR]

The radula is the food gathering and processing structure and one important autapomorphy of the Mollusca. It is composed of a chitinous membrane with small, embedded teeth representing the interface between the organism and its ingesta. In the past, various approaches aimed at connecting the tooth morphologies, which can be highly distinct even within single radulae, to their functionality. However, conclusions from the literature were mainly drawn from analyzing mounted radulae, even though the configuration of the radula during foraging is not necessarily the same as in mounted specimens. Thus, the truly interacting radular parts and teeth, including 3D architecture of this complex structure during foraging were not previously determined. Here we present an experimental approach on individuals of Vittina turrita (Neritidae, Gastropoda), which were fed with algae paste attached to different sandpaper types. By comparing these radulae to radulae from control group, sandpaper-induced tooth wear patterns were identified and both area and volume loss could be quantified. In addition to the exact contact area of each tooth, conclusions about the 3D position of teeth and radular bending during feeding motion could be drawn. Furthermore, hypotheses about specific tooth functions could be put forward. These feeding experiments under controlled conditions were introduced for stylommatophoran gastropods with isodont radulae and are now applied to heterodont and complex radulae, which may provide a good basis for future studies on radula functional morphology. [ABSTRACT FROM AUTHOR]

Two species of scallop, Austrochlamys natans ("Ostión del Sur") and Zygochlamys patagonica ("Ostión patagonico") are presently exploited in the southern part of the Magallanes Province (MP). The lack of clarity in taxonomic identification and ecological aspects is generating both erroneous extraction statistics and an unperceived harvesting pressure on A. natans and Z. patagonica. We aim to discriminate these Magallanes scallops accurately, improve our understanding of their complex natural history and discuss possible implications for their management and conservation status, given the current fisheries statistics. To achieve these goals, we present a complete review of the historical identification of the Magallanes scallop and a multi-locus molecular phylogeny which allowed us to recover the phylogenetic position of A. natans. We sampled 54 individuals from five localities across the southern Pacific coast of the MP. We calculated the depth of the byssal notch (BND) and shell height (VH) ratio from morphological characters and conducted phylogenetic reconstructions with mitochondrial (12S and 16S) and nuclear markers (28S) using Bayesian and maximum likelihood analyses. Both morphology and molecular phylogeny identified two distinct entities, Z. patagonica and a distinct, highly divergent lineage that corresponds to A. natans. Our study provides integrative evidence to alert the current fishery management and the need for further conservation studies. [ABSTRACT FROM AUTHOR]

Hox genes are key developmental regulators that are involved in establishing morphological features during animal ontogeny. They are commonly expressed along the anterior–posterior axis in a staggered, or collinear, fashion. In mollusks, the repertoire of body plans is widely diverse and current data suggest their involvement during development of landmark morphological traits in Conchifera, one of the two major lineages that comprises those taxa that originated from a uni-shelled ancestor (Monoplacophora, Gastropoda, Cephalopoda, Scaphopoda, Bivalvia). For most clades, and bivalves in particular, data on Hox gene expression throughout ontogeny are scarce. We thus investigated Hox expression during development of the quagga mussel, Dreissena rostriformis, to elucidate to which degree they might contribute to specific phenotypic traits as in other conchiferans. The Hox/ParaHox complement of Mollusca typically comprises 14 genes, 13 of which are present in bivalve genomes including Dreissena. We describe here expression of 9 Hox genes and the ParaHox gene Xlox during Dreissena development. Hox expression in Dreissena is first detected in the gastrula stage with widely overlapping expression domains of most genes. In the trochophore stage, Hox gene expression shifts towards more compact, largely mesodermal domains. Only few of these domains can be assigned to specific developing morphological structures such as Hox1 in the shell field and Xlox in the hindgut. We did not find traces of spatial or temporal staggered expression of Hox genes in Dreissena. Our data support the notion that Hox gene expression has been coopted independently, and to varying degrees, into lineage-specific structures in the respective conchiferan clades. The non-collinear mode of Hox expression in Dreissena might be a result of the low degree of body plan regionalization along the bivalve anterior–posterior axis as exemplified by the lack of key morphological traits such as a distinct head, cephalic tentacles, radula apparatus, and a simplified central nervous system. [ABSTRACT FROM AUTHOR]

Mollusks have a wide variety of body plans, which develop through conserved early embryogenesis, namely spiral embryonic development and trochophore larvae. Although the comparative study of mollusks has attracted the interest of evolutionary developmental biology researchers, less attention has been paid to bivalves. In this review, we focused on the evolutionary process from single‐shell ancestors to bivalves, which possess bilaterally separated shells. Our study tracing the lineage of shell field cells in bivalves did not support the old hypothesis that shell plate morphology is due to modification of the spiral cleavage pattern. Rather, we suggest that modification of the shell field induction process is the key to understanding the evolution of shell morphology. The novel body plan of bivalves cannot be established solely via separating shell plates, but rather requires the formation of additional organs, such as adductor muscles. The evolutionary biology of bivalves offers a unique view on how multiple organs evolve in a coordinated manner to establish a novel body plan. RESEARCH HIGHLIGHTS: Various morphology of mollusks developed from the conserved spiral development provide a nice research area of EvoDevo.Unique shell plate morphology is likely to be achieved through modification of the shell field induction process.The evolutionary biology of bivalves offers a unique view on how multiple organs evolve in a coordinated manner to establish a novel body plan. [ABSTRACT FROM AUTHOR]

Type specimens and (or) photographs of the 21 named taxa used for California Holocene olivellids were examined to recognize four modern species now assigned to the genus Callianax and one species presumed extinct. The California Holocene species include C. alectona, C. biplicata, C. diegensis, and C. strigata, while the extinct species is Olivella pedroana. Other olivellid names previously used in California are also discussed and these include O. baetica, O. biplicata alba, O. biplicata angelana, O. biplicata brunnea, O. biplicata fucana, O. biplicata lapillus, O. biplicata parva, O. boetica, O. b. diegensis, O. b. mexicana, O. dama, O. glandinaria, O. intorta, O. minuta, O. nota, O. porteri, and O. pycna. Olivella dama and O. intorta are valid species that occur further south in Mexico and are not present in California today despite reports. Olivella nota is also a valid name but for a west Pacific species. [ABSTRACT FROM AUTHOR]

Anatinella nicobarica is a very rarely reported species of bivalve mollusc in the world. It was discovered in the Nicobar Sea by Gmelin, (1791) for the first time. After so many years, its rave occurrence was observed in India. Reappearance of this rare clam was reported after 72 years from Chennai beach (mainland coast of India). [ABSTRACT FROM AUTHOR]

Mollusk shells are an ideal model system for understanding the morpho-elastic basis of morphological evolution of invertebrates’ exoskeletons. During the formation of the shell, the mantle tissue secretes proteins and minerals that calcify to form a new incremental layer of the exoskeleton. Most of the existing literature on the morphology of mollusks is descriptive. The mathematical understanding of the underlying coupling between pre-existing shell morphology, de novo surface deposition and morpho-elastic volume growth is at a nascent stage, primarily limited to reduced geometric representations. Here, we propose a general, three-dimensional computational framework coupling pre-existing morphology, incremental surface growth by accretion, and morpho-elastic volume growth. We exercise this framework by applying it to explain the stepwise morphogenesis of seashells during growth: new material surfaces are laid down by accretive growth on the mantle whose form is determined by its morpho-elastic growth. Calcification of the newest surfaces extends the shell as well as creates a new scaffold that constrains the next growth step. We study the effects of surface and volumetric growth rates, and of previously deposited shell geometries on the resulting modes of mantle deformation, and therefore of the developing shell’s morphology. Connections are made to a range of complex shells ornamentations. [ABSTRACT FROM AUTHOR]

This study reports fifteen species of nudibranchs from the coast of Pakistan (Northern Arabian Sea) except Jorunna funebris reported here, all are new records. [ABSTRACT FROM AUTHOR]

Two new species of genus Amphidromus Albers, 1850 are described from Vietnam and compared to five other species of this genus: Amphidromus koenigi Thach & Huber, 2018, Amphidromus laii Thach, 2019, Amphidromus inconstans Fulton, 1898, Amphidromus kaloensis Fulton, 1896 and Amphidromus bernardfamyi Thach, 2017. [ABSTRACT FROM AUTHOR]

Subspecies richness (average number of subspecies per species = SSP/SP) has traditionally been explained by niche breadth, characteristics of the preferred habitat ("habitat hypothesis"), dispersal ability, range size ("range size hypothesis"), etc. However, in several invertebrate groups, there are striking differences between SSP/SP across families, which cannot be explained using classic arguments, and we might assume some hidden factor in the background. For example, some families of terrestrial molluscs, that possess conspicuously more subspecies than others, have higher degree of morphological complexity (shell size, number of diagnosable shell characters), for which we propose the "artefact hypothesis." According to this, morphological complexity plays an important role in taxonomists' subspecies recognition. We used shell size, number of characters mentioned in species descriptions and area extent in six European land snail families, and habitat characteristics (rock‐dwelling vs. non‐rock‐dwelling) in one largest European snail families (Clausiliidae) to test our hypothesis. We found that all three factors (range size, morphological complexity and habitat type) correlated positively with the SSP/SP ratio. Although the generality of our findings has to be tested in other invertebrate phyla, we provide examples of striking differences between SSP/SP ratios in butterflies (Lepidoptera) and beetles (Coleoptera) as well. Our findings imply that researchers (a) should use the number of SSP more carefully in comprehensive studies, and (b) should maintain and use the rank subspecies in order to provide a stronger status for the species rank, and avoid taxonomic inflation. Furthermore, the subspecies rank might be more useful for "cryptic species" (clades that are indistinguishable morphologically) than species. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Molluscan shells, exhibiting a variety of complex three-dimensional architectures, are an exemplar model system to study biogenic mineral formation by living organisms. Recent studies have demonstrated that the deposition process of some shell ultrastructures can be described using classical analytical models borrowed from materials physics, which were developed to predict the structural evolution of man-made and geological polycrystalline composite assemblies. In the current study, we use this newly developed capacity to quantitatively describe the morphogenesis of the prismatic ultrastructure in three shells from the bivalve family Pinnidae towards establishing a correlation between structure, texture, growth kinetics, topology and phylogeny of the species. Using data collected by electron microscopy, synchrotron-based microtomography, electron backscatter diffraction analysis (EBSD) and X-ray diffraction we demonstrate that the prismatic ultrastructures in Pinnidae are formed following either ideal or triple-junction-controlled kinetics, which are shown to be closely linked to the morphological and topological characteristics, as well as crystallographic texture of these biocomposites. The experimental and analytical framework presented in this comparative study can serve as an additional tool for classifying molluscan shell ultrastructures on the levels of structural and textural morphogenesis. Statement of Significance The ability to quantitatively describe the structural evolution of the prismatic architecture in mollusc shells is used for the first time to derive and compare between analytical parameters that define the growth kinetics and morphological and topological evolution during the growth of three shells from the family Pinnidae from two different genera. Furthermore, these parameters are linked to the evolution of crystallographic texture in the studied architectures. The developed experimental and analytical framework not only enables us to quantitatively describe species-specific growth mechanisms but also suggests a direct correlation between the evolution of morphology and texture. [ABSTRACT FROM AUTHOR]

New records of early life stages of cephalopods are presented based on planktonic collections carried out around Easter Island (Rapa Nui; 27°7′S, 109°21′W) and at the nearby Apolo Seamount (located at ~7 nautical miles southwest from Easter Island) during March and September 2015 and March 2016. A total of 13 individuals were collected, comprising four families (Octopodidae, Ommastrephidae, Chtenopterygidae, and Enoploteuthidae) and five potential genera/types (Octopus sp. Chtenopteryx sp. rhynchoteuthion paralarvae, and two undetermined Enoploteuthid paralarvae). Cephalopod mantle lengths (ML) ranged from 0.8 to 4.5 mm, with 65% of them (mainly Octopodidae) corresponding to newly hatched paralarvae of ~1 mm ML, and 35% to rhynchoteuthion and early stages of oceanic squids of around 1.5–4.5 mm ML. These results provide the first records on composition and presence of early stages of cephalopods around a remote Chilean Pacific Island, while also providing a morphological and molecular basis to validate the identity of Octopus rapanui (but not Callistoctopus, as currently recorded), Ommastrephes bartramii and Chtenopteryx sp. around Rapa Nui waters. Despite adult Octopodidae and Ommastrephidae having been previously recorded at these latitudes, the current findings provide evidence to suggest that the northwest side of Easter Island, and one of the nearby seamounts, may provide a suitable spawning ground for benthic and pelagic species of cephalopods inhabiting these areas. For Chtenopterygidae and Enoploteuthidae, this is the first record for the Rapa Nui ecoregion. [ABSTRACT FROM AUTHOR]

Variation in snail shell shape has provided evolutionary biologists with excellent material for the study of local adaptation to local environments. However, the assumption that shell shape variation is evidence of distinct lineages (species) might have led to taxonomic inflation within some gastropod lineages. Here, we compare shell shape variation and genetic structure of two independent lineages of New Zealand rocky shore whelks in order to understand the process that leads to an unusual disjunct distribution. We examined the Buccinulum vittatum complex (three subspecies plus Buccinulum colensoi) using mitochondrial DNA sequences, 849 single nucleotide polymorphisms and geometric morphometric data on shell shape. Specimens within the range of B. colensoi shared nuclear markers and mitochondrial DNA haplotypes with the southern subspecies Buccinulum vittatum littorinoides, whereas the northern samples (Buccinulum vittatum vittatum) had distinct genotypes. We infer that gene flow between B. colensoi and B. v. littorinoides is greater than between either of these taxa and B. v. vittatum. The distinctive shell sculpturing of B. colensoi is maintained despite gene flow, suggesting a role for selection. Although the shell form of B. colensoi appears to be an adaptation to local conditions, we did not observe convergent evolution in the sympatric whelk species Cominella maculosa. [ABSTRACT FROM AUTHOR]

Deep-sea clams (Bivalvia: Vesicomyidae) have been found in reduced environments over the world oceans, but taxonomy of this group remains confusing at species and supraspecific levels due to their high-morphological similarity and plasticity. In the present study, we collected mitochondrial COI sequences to evaluate the utility of DNA barcoding on identifying vesicomyid species. COI dataset identified 56 well-supported putative species/operational taxonomic units (OTUs), approximately covering half of the extant vesicomyid species. One species (OTU2) was first detected, and may represent a new species. Average distances between species ranged from 1.65 to 29.64%, generally higher than average intraspecific distances (0-1.41%) when excluding Pliocardia sp.10 cf. venusta (average intraspecific distance 1.91%). Local barcoding gap existed in 33 of the 35 species when comparing distances of maximum interspecific and minimum interspecific distances with two exceptions (Abyssogena southwardae and Calyptogena rectimargo-starobogatovi). The barcode index number (BIN) system determined 41 of the 56 species/OTUs, each with a unique BIN, indicating their validity. Three species were found to have two BINs, together with their high level of intraspecific variation, implying cryptic diversity within them. Although fewer 16 S sequences were collected, similar results were obtained. Nineteen putative species were determined and no overlap observed between intra- and inter-specific variation. Implications of DNA barcoding for the Vesicomyidae taxonomy were then discussed. Findings of this study will provide important evidence for taxonomic revision in this problematic clam group, and accelerate the discovery of new vesicomyid species in the future. [ABSTRACT FROM AUTHOR]

Evolutionary and ecological situations in a species’ native and invasive ranges can be drastically different. This is the case for Potamopyrgus antipodarum Gray (1843) a morphologically highly variable freshwater snail native to New Zealand, where sexual and asexual individuals coexist and experience selective pressure by sterilizing endoparasites. By contrast, only a few asexual lineages have been established in invaded regions around the globe, where parasite infection is extremely rare. We analyzed the ecomorphology of 996 native P. antipodarum in a geometric morphometric framework, using brood size as proxy for fecundity, and mtDNA and nuclear SNPs to account for relatedness and identify reproductive mode. As expected, we found genetic and morphological diversity to be higher in native than in invasive snails investigated previously, but surprisingly no higher morphological diversity in sexual versus asexual individuals. The relationships between shell morphology, habitat, and fecundity were complex. Shape variation was primarily linked to genetic relatedness but specific environmental factors including flow rate induced similar shell shapes. By contrast, shell size was largely explained by environmental factors. Fecundity was correlated with size but showed trade-offs with shape in increasingly extreme conditions. With increasing flow and toward small springs, the trend of shell shape becoming wider was reversed, i.e., snails with narrower shells were brooding more embryos. We concluded that both genetic and environmental contributions to variation in shell morphology in P. antipodarum likely play an important role in the ability of this species to adapt to a wide spectrum of habitats. [ABSTRACT FROM AUTHOR]

A new subspecies of genus Leptopoma Pfeiffer, 1847 is described from Selawati Island, West New Guinea, Indonesia and compared to six other species and forms of this genus: Leptopoma melanostoma (Petit, 1841), Leptopoma niasense Fulton, 1907, Leptopoma perlucidum f. subalatum Quadras & Möllendorff, 1893, Leptopoma helicoides (Grateloup 1840), Leptopoma vitreum (Lesson, 1830) and Leptopoma stainforthi (Sowerby, 1842). It is characterized by a translucent shell, dark brown umbilicus, black outer lip and columella, narrow but raised peripheral rib, and wide dark brown umbilicus. [ABSTRACT FROM AUTHOR]

The Volutid genus Arctomelon Dall, 1915 in Alaskan waters is examined, four species are recognized. A new species, Arctomelon borealis sp. nov. is described from bathyal depths of the central Aleutian Islands. A. stearnsii ryosukei (Habe & Ito, 1965) is recognized as a distinct species. [ABSTRACT FROM AUTHOR]

This paper seeks to correct the erroneous taxonomy associated with the current understanding of the Altivasum flindersi (Verco, 1914) complex based on type revision, morphological differences and geographic separation. Structurally, there are three distinct species that can be differentiated, Altivasum flindersi (Verco, 1914), A. typicum Hedley, 1916 and A. profundum sp. nov. Geographically, these species are not all sympatric, with A. typicum restricted to shallower waters, at depths around 20-180 m off the south Western Australian coast, whereas A. profundum is located at the edge of the South Western Australian continental shelf, and A. flindersi is found off the coast of the Great Australian Bight at similar depths to A. typicum. There is an overlap in distribution between A. typicum Hedley, 1916 and A. flindersi (Verco, 1914) on the western side of the Great Australian Bight where they are often associated with similar habitats. [ABSTRACT FROM AUTHOR]

The named taxa of Chondropometes land snails from western Cuba Annulariidae are reviewed and illustrated. Following a discussion of the taxonomic work to date and the morphology, distribution and ecology of these land snails, the authors make suggestions for future work based upon shell morphological features and geographic isolation of various populations. [ABSTRACT FROM AUTHOR]

Cephalopods are an important, abundant and taxonomically diverse component of the bathypelagic realm. However, their biology, ecology and distribution are poorly known. Specimens of Mastigoteuthis agassizii (Mastigoteuthidae) have been captured in the southern part of the Denmark Strait, which is at approximately 65°N. This site is approximately 550 km north of the previously most northern known border of the Mastigoteuthidae range. The main goal of this paper is to provide an extended morphological description and biological analysis of M. agassizii, the first species of the Mastigoteuthidae caught in the Subarctic Atlantic. Despite sample collection at 534 deep-water stations in the area, only two specimens were captured, indicating the rarity of this species in the northern part of its range. We suggest that the typical range of this species is bathyal depths throughout the North Atlantic to the Subarctic, but not through the Denmark and Davis Straits to the Arctic. These findings coincide with the geographic border of the Northern Atlantic boreal bathyal province, which is warmer and more saline compared to the Arctic province further to the north. We also provide the first descriptions of the radula and reproductive system of M. agassizii. The female had synchronous ovulation, fecundity of approximately 23,000 oocytes, oocyte resorption having not been found, most likely due to the early maturity stage of the female. The males, as proven by our sample and additional photo in other source, were found to have the distal part of the penis enlarged, divided into two valves and pigmented, possibly indicating they can protrude outside the mantle cavity. This enlarged valved part, as it is supposed in the literature for other deep-water squid families having it, may be used as an analogue to the lacking hectocotylus. [ABSTRACT FROM AUTHOR]

Molecular and morphological data from newly collected specimens and a review of the literature and type material indicate that the widespread tropical sea hare Dolabrifera dolabrifera is a species complex of five genetically distinct taxa. The name Dolabrifera dolabrifera is retained for a widespread species in the Indo-Pacific tropics. Dolabrifera nicaraguana is endemic to the eastern Pacific. Dolabrifera ascifera, D. virens and a new species described herein are restricted to the tropical Atlantic, with partially overlapping ranges in the Caribbean region and St. Helena. The temperate Pacific species Dolabrifera brazieri is also distinct and endemic to temperate southeastern Australia and New Zealand. These species of Dolabrifera constitute highly divergent lineages and most contain unique internal anatomical characteristics, particularly in the male reproductive morphology and shell shape, making them relatively easy to identify upon dissection. However, externally all these species are extremely variable in colour pattern and morphology and are virtually indistinguishable. This is particularly problematic for identification in the Atlantic Ocean where three species co-occur in the Caribbean region. [ABSTRACT FROM AUTHOR]

The western Palearctic freshwater snail genus Mercuria (Caenogastropoda: Hydrobiidae) comprises 26 species primarily distributed in lowland localities of Western Europe and North Africa. Although this genus in North Africa has received considerable attention in terms of species discoveries through morphological descriptions, its distribution and phylogenetic patterns remain unknown. Based on morphological and mitochondrial DNA (mtCOI) evidence, this study examines the three Mercuria species (M. bakeri, M. tingitana, and M. targouasensis) from Morocco identified so far. Besides expanding on information regarding the anatomy of these species, two new species (M. midarensis sp. n. and M. tensiftensis sp. n.) are described for this region and phylogenetic relationships inferred between these species and the European M. emiliana and M. similis. All Moroccan and European species were recovered as independent entities according to these phylogenetic inferences (uncorrected p-distances 2.8-8.5%) and DNA barcode data. Moroccan Mercuria species clustered with M. emiliana from Spain, although basal relationships within this clade were not well supported. Given that factors such as the season when specimens are collected, habitat type, and parasites could be responsible for the remarkable intraspecific variation observed in shell and penis morphology, it is proposed that the most efficient approach to delimit and identify Mercuria species is to combine morphological descriptions with genetic data. [ABSTRACT FROM AUTHOR]

Alongside confirmation of the monophyly of the gastropod family Mitridae, a recent molecular phylogenetic analysis disclosed multiple inconsistencies with the existing taxonomic framework. In the present study, we expanded the molecular sampling to 103 species, representing 26% of the 402 extant species currently accepted in the family and 16 of the 19 currently accepted extant genera; 83 species were sequenced for four molecular markers [cytochrome c oxidase subunit I (COI), 16S and 12S rRNA, and H3 (Histone 3)]. Molecular analyses were supplemented by morphological studies, focused on characters of the radula and, in a more restricted data set, proboscis anatomy. These data form the basis for a revised classification of the Mitridae. A first dichotomy divides mitrids into two unequal clades, Charitodoron and the Mitridae s.s. Species of Charitodoron show profound differences to all other Mitridae in foregut anatomy (lacking an epiproboscis) and shell morphology (smooth columella, bulbous protoconch of non-planktotrophic type), which leads to the erection of the separate family Charitodoronidaefam. nov. Three traditional subfamilies (Mitrinae, Cylindromitrinae and Imbricariinae) correspond to three of the inferred phylogenetic lineages of Mitridae s.s.; we redefine their contents, reinstate Strigatellinae Troschel, 1869 as valid and establish the new subfamily Isarinae. In the absence of molecular material, a sixth subfamily, Pleioptygmatinae, is included in Mitridae based on morphological considerations only. To resolve the polyphyly of Mitra and Cancilla in their current taxonomic extension, we reinstate the genera Episcomitra Monterosato, 1917, Isara H. & A. Adams, 1853 and Probata Sarasúa, 1989 and establish 11 new genera: Quasimitra, Roseomitra, Fusidomiporta, Profundimitra, Cancillopsis, Pseudonebularia, Gemmulimitra and Neotiara in Mitrinae; Imbricariopsis in Imbricariinae; Carinomitra and Condylomitra are left unassigned to a subfamily. Altogether 32 genera are recognized within the family. Their diversity and distribution are discussed, along with general trends in morphological evolution of the family. [ABSTRACT FROM AUTHOR]

Abstract: Mucus‐secreting epithelia protect marine gastropods from abrasive particles and microbes in seawater. We studied the morphology and function of the epithelium in the giant keyhole limpet Megathura crenulata. All exposed surfaces of the limpets were covered by a mucus‐secreting, simple columnar epithelium, in which most cells on the sole of the foot bore cilia, while the majority of cells on the side of the foot and three mantle regions bore microvilli. None of the coatings had antibacterial properties. The epithelium of the foot was distinct from that of other regions, in that the mucus secreted was used for locomotion and was left behind as the limpet moved. The glycocalyx bound to the microvilli of the mantle cells appeared to be clean in visual and SEM examinations, and attempts to enhance the binding of inert particles and bacteria were unsuccessful. Because studies have shown that standard tissue processing may cause artifactual shrinkage of mucous layers, cryostat sections and additives to standard fixatives were tested, but we found no change in the thickness of the mucous layers of the limpets compared to routinely processed tissues. Sloughing of the glycocalyx in vertebrate systems removes bound microbes, and alterations of the glycocalyx layers are associated with disease conditions. Sloughing of the glycocalyx on limpets was rarely observed. In one case, the outer mantle of the limpet was covered with silt and the glycocalyx appeared to be detaching. This process could be experimentally induced by dousing the outer mantle with talc particles. The types of secretory cells producing the mucus in each region of the skin were characterized using standard histological stains and lectin staining. Because analysis was hampered by their small size, classification of the types of secretory cells was based on TEM descriptions of granule morphology, which allowed for comparison to the secretory cells described from skin of the abalone. The possible roles of the numerous secretions, and the mechanisms of mucus production and loss, are compared to what is known in vertebrate systems and to our relative lack of knowledge regarding invertebrate systems. [ABSTRACT FROM AUTHOR]

We describe an Olenekian (Early Triassic) "fossil squid" belonging to the oldest complex Mesozoic marine biota collected in the Lower Shale unit of the Lower Triassic Thaynes Group in Idaho, USA. The studied specimen shows a tapered structure embedded in a cylindrical soft body. Morphological, ultrastructural and geochemical features of the specimen suggest that it corresponds to an internally-shelled cephalopod exhibiting a tapered micro-laminated gladius with rachis, narrow median and lateral fields and a large conus; a pair of posterior large fin-supported cartilages and fins; ventral and dorsal mantle band-shape structures, the dorsal one being cartilaginous; mantle patches; a stomach containing undigested arm-hooks and sheet-like pieces of potential flooded ink. Coupled SEM/EDS analyses show that (i) arm-hooks and ink were pseudomorphed by nanoparticles (less than 0.6 mm in diameter) of carbon, (ii) gladius and soft tissues were substituted by granules of calcium phosphate, (iii) cartilage canalicula's were partially filled with calcium phosphate grains and crystals of Zn- and S-containing minerals. The specimen was hence probably fossilized due to metabolism of P- and C-accumulating bacteria. Based on this specimen, Idahoteuthis parisiana Doguzhaeva and Brayard gen. et sp. nov. and Idahoteuthidae Doguzhaeva and Brayard fam. nov. are erected. This family is characterized by an elongated, cylindrical, dorsally cartilaginous muscular mantle; well-developed, about 0.2 mantle length, rounded anteriorly and acute posteriorly, fin-supported cartilages and similarly shaped two fins at conical mantle termination, and thin slender gladius with narrow median and lateral fields, rachis and breviconic conus. This family assumedly falls in Myopsida (Decabrachia). A streamlined body, large fin-supported cartilages and eroded arm-hooks in the stomach of Idahoteuthis Doguzhaeva and Brayard gen. nov. suggest that this was a maneuverable cannibal predator that dwelled in the subequatorial shallow sea of the west coast of Pangaea. [ABSTRACT FROM AUTHOR]

Alongside confirmation of the monophyly of the gastropod family Mitridae, a recent molecular phylogenetic analysis disclosed multiple inconsistencies with the existing taxonomic framework. In the present study, we expanded the molecular sampling to 103 species, representing 26% of the 402 extant species currently accepted in the family and 16 of the 19 currently accepted extant genera; 83 species were sequenced for four molecular markers [cytochrome c oxidase subunit I (COI), 16S and 12S rRNA, and H3 (Histone 3)]. Molecular analyses were supplemented by morphological studies, focused on characters of the radula and, in a more restricted data set, proboscis anatomy. These data form the basis for a revised classification of the Mitridae. A first dichotomy divides mitrids into two unequal clades, Charitodoron and the Mitridae s.s. Species of Charitodoron show profound differences to all other Mitridae in foregut anatomy (lacking an epiproboscis) and shell morphology (smooth columella, bulbous protoconch of non-planktotrophic type), which leads to the erection of the separate family Charitodoronidae fam. nov. Three traditional subfamilies (Mitrinae, Cylindromitrinae and Imbricariinae) correspond to three of the inferred phylogenetic lineages of Mitridae s.s.; we redefine their contents, reinstate Strigatellinae Troschel, 1869 as valid and establish the new subfamily Isarinae. In the absence of molecular material, a sixth subfamily, Pleioptygmatinae, is included in Mitridae based on morphological considerations only. To resolve the polyphyly of Mitra and Cancilla in their current taxonomic extension, we reinstate the genera Episcomitra Monterosato, 1917, Isara H. & A. Adams, 1853 and Probata Sarasúa, 1989 and establish 11 new genera: Quasimitra, Roseomitra, Fusidomiporta, Profundimitra, Cancillopsis, Pseudonebularia, Gemmulimitra and Neotiara in Mitrinae; Imbricariopsis in Imbricariinae; Carinomitra and Condylomitra are left unassigned to a subfamily. Altogether 32 genera are recognized within the family. Their diversity and distribution are discussed, along with general trends in morphological evolution of the family. [ABSTRACT FROM AUTHOR]

The study of morphology is a common means of biological grouping and classification. In recent years, morphometric studies have been dominated by quantitative geometric-morphometric methods of data extraction such as outline or landmark-based analysis. These methods are often used in conjunction with various classification methods such as linear discriminant analysis (LDA) and random forests (RF) in order to achieve inter- and intraspecific grouping based on environmental factors. Despite numerous studies incorporating these data-extraction and classification methods, comparisons of the effectiveness of these methods are largely lacking, especially for species which display low morphological variation. The aim of this study was to compare the effectiveness of two data-extraction methods, elliptic Fourier analysis (EFA) and generalized Procrustes analysis, and two classification methods, LDA and RF, using Littorina littorea as the study organism. The results show that the principal component scores derived from EFA, provided the optimal data input for classification while the greatest percentage of successfully classified individuals was achieved using LDA. However, based on this study RF is the recommended classification method as it is resistant to overfitting, makes no assumptions about the data, is well suited to morphometric data and produces similar rates of classification to LDA. The results are discussed in a biological context for L. littorea, based on the environmental factors of zonation and shore exposure. [ABSTRACT FROM AUTHOR]

Chaetoderma nitidulum Lovén, 1844 is a common species of caudofoveate (chaetodermomorph) with a wide distribution range in the northeastern Atlantic Ocean. It was the first species of aplacophoran mollusc to be described, but its species identity has been debated. Here, we investigate the molecular and morphological diversity of specimens from a large geographical area and size range, which had been preliminarily identified, based on morphology, as C. nitidulum. Analyses of molecular data revealed two distinct genetic sister lineages in the Eastern Atlantic and one clade sister to these in the Western Atlantic. Morphological analyses showed significant variation that does not reflect the genetic linages. In addition, molecular phylogenetics combined with comparative morphological analyses showed that radula characters used to distinguish the genera Chaetoderma and Falcidens within Chaetodermatidae do not represent apomorphies, but are a result of ontogenetic changes in C. nitidulum. The emerging phylogenetic patterns were surprising, bringing us one step closer to understanding chaetodermatid ontogeny and evolution, but they also emphasize that the systematic relationships of chaetodermatid caudofoveates are still far from understood. [ABSTRACT FROM AUTHOR]

Confirming the extinction of species with only old occurrence records is often difficult, due to the scarcity of biological information. Phylogenetic position and taxonomic status of the potentially extinct species are unclear in most such cases. In the present study, we document that a species of the endemic genus Hirasea of the oceanic Ogasawara Islands, which was formerly believed to have become extinct, still survives, on the basis of combined surveys involving molecular phylogenetics and morphometrics. Hirasea is notorious for its highly diversified shell morphologies and a number of species and subspecies have already become extinct because of environmental changes and impacts of alien predators. In this study, we first reconstruct phylogenetic relationships among extant Hirasea populations. Next, on the basis of quantitative shell morphological analysis of extant populations and type specimens, we identify morphological traits that reflect phylogenetic relationships among the species. By using these morphological traits and molecular phylogenies, we demonstrate that H. nesiotica liobasis, previously considered extinct, is still extant on Chichijima. Although classifications by means of morphology and molecular phylogeny often show incongruences, judgement of the conspecific status of living and extinct populations is still possible by considering ranges of variation and phylogenetic constraints on morphological traits. [ABSTRACT FROM AUTHOR]

Repetitive DNA represents the major component of the genome in both plant and animal species. It includes transposable elements (TEs), which are dispersed throughout the genome, and satellite DNAs (satDNAs), which are tandemly organized in long arrays. The study of the structure and organization of repetitive DNA contributes to our understanding of genome architecture and the mechanisms leading to its evolution. Molluscs represent one of the largest groups of invertebrates and include organisms with a wide variety of morphologies and lifestyles. To increase our knowledge of bivalves at the genome level, we analysed the Antarctic scallop Adamussium colbecki. The screening of the genomic library evidenced the presence of two novel satDNA elements and the CvA transposon. The interspecific investigation performed in this study demonstrated that one of the two satDNAs isolated in A. colbecki is widespread in polar molluscan species, indicating a possible link between repetitive DNA and abiotic factors. Moreover, the transcriptional activity of CvA and its presence in long-diverged bivalves suggests a possible role for this ancient element in shaping the genome architecture of this clade. [ABSTRACT FROM AUTHOR]

Planktonic larval stages of bivalves are notoriously difficult to identify due to their similar morphology. To evaluate changed patterns in the presented planktonic bivalve larvae within Gomso Bay (Yellow Sea, South Korea), three sites were sampled twice a month from June to October 2015 and were analysed using next-generation sequencing (NGS) and light microscopy. Bivalve larvae revealed different patterns, and at least five bivalve taxa were only detected by the NGS. According to the NGS results, most bivalve larvae were Crassostrea gigas (37%), followed by Ruditapes philippinarum (26%), and Solen strictus (23%); Mactra chinensis and M. veneriformis accounted for <1% of the bivalve larvae. C. gigas and S. strictus were most abundant in late June, but rare in the other investigated periods, while R. philippinarum was more abundant in June and late September. Microscopic observations showed a similar trend to the NGS in terms of bivalve larvae presence, although they were difficult to identify the exact species. Thus, morphological and molecular approaches should be combined in future studies to provide accurate sequences of correctly identified specimens to develop NGS libraries. [ABSTRACT FROM AUTHOR]

We studied shell variation in the thick-shelled river mussel (Unio crassus Philipson, 1788) sampled from two sites of very different character: (1) a rocky channel (San river) and (2) a fine-sediment channel (Zborowianka river). The analyzed mussels differed significantly between the sampled channels in almost all analyzed phenotypic traits and shape indices. Intersexual variation was so low that it cannot be used effectively for sexing in this species. The growth rate was much higher in the fine-sediment and nutrient-rich channel than in the rocky one, but the asymptotic shell length for the rocky channel was larger than for the fine-sediment channel, suggesting higher survival in the mountainous, unmodified river. Shell size differed significantly within the rocky channel, depending on microhabitat: shell size and dorsal arching were much greater in mussels living in the strong current of the rocky midchannel than in those inhabiting still water at the nearest bank. The results demonstrate that microhabitat conditions significantly determine shell shape. [ABSTRACT FROM AUTHOR]

The expression of alternative reproductive tactics (ARTs) is often influenced by the environmental cues and intrinsic conditions experienced by each male, and it may be reversible or permanent. In male loliginid squid, ARTs include consorts and sneakers, which differ in behaviour, body size, sperm deposition site, and morphology and functioning of ejaculates. Here, we describe intermediate-sized males in the squid Doryteuthis plei (Blainville, 1823) that produce sneaker-like, consort-like and intermediate ejaculates. In addition, age estimates show that sneakers and intermediate males are younger than consorts. Our findings suggest that ARTs in this species may be ontogenetically expressed. Such a transition between phenotypes requires dramatic anatomical and physiological reorganization of the male reproductive system, not only to produce different-structured spermatophores, but also to generate sperm with distinct behaviour, both of which are compatible with the switch in sperm deposition site. These findings demonstrate that this peculiar mating system may also fit the current predictions of ARTs. [ABSTRACT FROM AUTHOR]

Four rare Pennsylvanian (Stark Shale: Pennsylvanian, Missourian [=Kasimovian]) coleoids from Nebraska and Iowa, which are preserved as flattened partial phragmocones and body chambers associated with three-dimensionally fossilized ink sacs, are herein described as Pabianiconus starkensis new genus new species, Nebraskaconus whitei new genus new species, and Starkites compressus new genus new species. One specimen that is missing most of the phragmocone, is provisionally assigned to Donovaniconus. The fossils are assigned to the Coleoidea because of the presence of ink-filled sacs in the body chamber region of the conch. Additionally, eight fragmented and flattened phragmocones and body-chamber clusters with similar morphologies, including some with ink fragments and arm hooks, are assigned to the Coleoidea, but are not named because of their fragmentary condition. On most of the eight specimens, the shell material is associated with other unidentified finely macerated material, which suggests these fossils are probably either ejectoid masses or coprolites from coleoid predators and/or scavengers. However, the new genera named above appear to have been deposited as complete animals, based on the presence of the ink-filled sacs that are in the body chambers. With their body chamber and phragmocone morphologies, these rare coleoid taxa provide valuable information about conch variability within the Carboniferous evolutionary radiation of coleoids. [ABSTRACT FROM PUBLISHER]

BelgrandiellaA. J. Wagner, 1927 is a genus comprising minute snails with conic or turriform shells that are facultative stygobionts, inhabiting subterranean waters and springs. Few specimens or even empty shells of this taxon can be found, so the taxonomy is based mostly on the shell morphology and geographic distribution. Anatomy is known for a few taxa, and its usefulness is restricted. This, coupled with a popular idea that isolation is the first factor shaping divergence and speciation of the spring/cave fauna, resulted in dozens of nominal species ofBelgrandiella, known from shells at a given locality. Herein we present shells, anatomy and four molecular markers (nuclear H3, 18S and 28S and mitochondrial cytochrome oxidase subunit I) inBelgrandiellafrom 16 localities in Slovenia, northern Croatia, and Bosnia and Herzegovina. Five sites are type localities ofBoleana umbilicata, Belgrandiella kusceri,Belgrandiella krupensis,Belgrandiella zermanicaandBelgrandiella robusta,respectively. Considering the shell and geographic distribution, we have determinedB. cf.robustaBelgrandiellacf.croatica,Belgrandiellacf.fontinalis,Belgrandiellacf.kuesteri,Belgrandiellacf.pagetiandBelgrandiellacf.koprivnensisThe shells of all, as well as penes and female reproductive organs of two putative, species have been illustrated. Molecular analysis indicates four distinct clades, most probably of species rank forB. kusceri,B. cf.kuesteri,B. cf.fontinalisandB. cf.koprivnensis. Four nominal species (B. krupensis,B. robusta,B. umbilicataandB. zermanica) and one genus (Boleana) must be synonymised withBelgrandiella kusceri, and there are no more than four valid, biological species in the studiedBelgrandiella. The molecular divergence is completely unmirrored by high morphological variability. Hence the level of endemism is markedly overestimated in these snails. [ABSTRACT FROM AUTHOR]

The bivalve family Vesicomyidae comprises two subfamilies: Pliocardiinae and Vesicomyinae. The Pliocardiinae include conspicuous mostly large- and medium-sized clams, which live in symbiosis with chemoautotrophic bacteria and often dominate chemosynthetic communities in the deep sea. The Vesicomyinae comprise poorly-studied tiny bivalves, which at first sight differ considerably from their better known, large-sized relatives. Vesicomyines have a worldwide distribution from mid-slope to hadal depths and reach abundances of thousands of specimens in one trawl catch in deep-sea trenches. The genus Vesicomya is morphologically very similar to the genus Kelliella, the type genus of family Kelliellidae. This fact has long caused taxonomic ambiguities and it has been suggested that Vesicomya and Kelliella, as well as their respective nominate families, should be synonymized. In this paper we study the relationship between Vesicomya and Kelliella, for the first time using not only morphological characters but also genetic divergence based on the mitochondrial cytochrome c oxidase subunit I (COI) gene. Our molecular data indicate that the genera Vesicomya and Kelliella are clearly distinct and that Kelliella is distantly related to the Vesicomyidae. Results of morphological analysis support the molecular inferences. We provide further evidence for the relationship of vesicomyines and pliocardiines and propose an evolutionary scenario according to which Vesicomyinae is the less derived group and Pliocardiinae the more derived. We provide the first information on stable carbon and nitrogen isotopic composition of soft tissues of Vesicomya and Kelliella. These data do not suggest involvement of chemosynthetically fixed carbon in the nutrition of either Vesicomya or Kelliella. We revise current usage of these two genera and provide lists of the species of each, with details of their distribution. A new species, Vesicomya alleni, is described on the basis of morphological and molecular characters. [ABSTRACT FROM AUTHOR]

The genetic diversity of one of the most abundant species in the Arctic and subarctic oceans, the pelagic snail Limacina helicina, has not yet been characterized in the north Pacific. This species has different 'forma' (L. helicina forma helicina, acuta, pacifica and ochotensis), but whether or not the morphological differences between these forma are caused by phenotypic plasticity or genetic differentiation remains unclear. Here, we analysed partial nucleotide sequences of the mitochondrial cytochrome c oxidase subunit I gene in L. helicina from the subarctic western North Pacific Ocean (SWNP; L. helicina f. acuta) and compared them with those from Svalbard (L. helicina f. helicina) and other localities (Beaufort Sea, eastern Pacific, northern Sea of Japan and western Atlantic). The results show clear genetic differentiation between populations in the SWNP and Svalbard (ΦCT = 0.59282, P < 0.001). These genetic differences are consistent with the previous description of the two forma L. h. f. acuta (SWNP) and L. h. f. helicina (Svalbard) based on shell morphology [ABSTRACT FROM AUTHOR]