Mollusc Species Research Articles

Effect of tributyltin exposure on the embryonic development and behavior of a molluscan model species, Lymnaea stagnalis

The presence of the organotin compound tributyltin (TBT) in aquatic ecosystems has been a serious environmental problem for decades. Although a number of studies described the negative impact of TBT on mollusks at different levels, investigations connected to its potential effects during embryogenesis have been neglected. For a better understanding of the impact of TBT on mollusks, in the present study, embryos of previously TBT-treated or not treated specimens of the great pond snail (Lymnaea stagnalis) were exposed to 100 ng L−1 TBT from egg-laying (single-cell stage) until hatching. According to our results, TBT significantly delayed hatching and caused shell malformation. TBT transiently decreased the locomotion (gliding) and also reduced the feeding activity, demonstrating for the first time that this compound can alter the behavioral patterns of molluscan embryos. The heart rate was also significantly reduced, providing further support that cardiac activity is an excellent indicator of metal pollution in molluscan species. At the histochemical level, tin was demonstrated for the first time in TBT-treated hatchlings with intensive reaction in the central nervous system, kidney, and hepatopancreas. Overall, the most notable effects were observed in treated embryos derived from TBT treated snails. Our findings indicate that TBT has detrimental effects on the development and physiological functions of Lymnaea embryos even at a sub-lethal concentration, potentially influencing their survival and fitness. Highlighting our observations, we have demonstrated previously unknown physiological changes (altered heart rate, locomotion, and feeding activity) caused by TBT, as well as visualized tin at the histochemical level in a molluscan species for the first time following TBT exposure. Further studies are in progress to reveal the cellular and molecular mechanisms underlying the physiological and behavioral changes described in the present study.

A synopsis of the Early Miocene St Bathans Fauna of New Zealand

The St Bathans Fauna, from sites near the village of St Bathans, Central Otago, South Island, is the first substantive pre-Quaternary terrestrial vertebrate fossil fauna discovered in New Zealand. This fauna derives from 33 sites or discrete sedimentary beds located in the lower 50 m of the lacustrine Bannockburn Formation, Manuherikia Group, and is generally accepted as local stage Altonian (19–15.9 Ma; Burdigalian, Early Miocene) in age. Investigations since 2001 have revealed an abundant and diverse fauna from over 9000 catalogued lots that is herein reviewed. Invertebrates notably include eight genera and species of terrestrial molluscs. Among vertebrates, freshwater fish remains dominate with 17 species evidenced by 16,500 analysed otoliths (genera Neochanna, Galaxias, Prototroctes, and Mataichthys) and many thousands of bones. Birds (minimally 45 species, several thousand bones) are the most common non-fish vertebrates, among which waterfowls dominate all assemblages (10 species). Co-occurring with these was a diverse herpetofauna, including undetermined crocodylians and a terrestrial turtle, both absent in Recent faunas. Significantly, the St Bathans Fauna evidences that Zealandia already had all of New Zealand’s ‘old’ endemic Recent taxa (sphenodontids, leiopelmatids, dinornithiforms, apterygids, aptornithids, strigopoid parrots, acanthisittids, and mystacinids) during the Early Miocene. Furthermore, it includes Australasia’s oldest ardeids, two flightless rallids, a novel higher landbird family, a greater diversity of bats, and terrestrial mammals. All sites reflect a single fauna, except that the ducks Manuherikia lacustrina (stratigraphically lower in section) and M. primadividua (higher) have a mutually exclusive distribution that is not yet correlated with any other biotic distribution differences.

Extraction of melanin from the shell and mantle and activities of enzymes related to the melanin biosynthesis in the Ruditapes philippinarum

The shell surface of Manila clam (Ruditapes philippinarum) has a variety of colors and stripes, with diverse shell color polymorphism. As an important trait of economic shellfish, shell color plays an important role in the selection breeding of shellfish species. In this study, we extracted melanin from the shell and mantle of R. philippinarum by the hydrochloric acid method and measured the melanin content by spectrophotometry. The absorption spectrum of melanin and its absorption peak at 350 nm absorbance was determined. We found significant differences in the melanin content of clams with dark strain and light strain, as well as four different shell colors. Moreover, we further detected the activities of enzymes related to melanin synthesis in R. philippinarum mantle, such as tyrosinase (TYR), tyrosine hydroxylase (TH), dopa decarboxylase (DDC), N-acetyltransferase (NAT), and N-β- alanyldopamine (NBAD) in the mantle of R. philippinarum. The results showed that the activities of TYR, TH, DDC and NAT were positively correlated with the content of melanin. However, the activity of NBAD was negatively correlated with the content of melanin. Altogether, these results indicating that these enzymes are involved in the regulation of the melanogenesis pathway of R. philippinarum. This study provides valuable information for further research on shell color genetic mechanism and breeding of R. philippinarum.

Aquatic invertebrate diversity in Apostle Islands and Isle Royale waters: Comparison among habitats and sampling gears and to open Lake Superior

Aquatic invertebrate composition in Great Lakes nearshore regions is known to differ from offshore, but studies representing the closest-to-land end of this gradient are primarily from estuaries and rivermouths having substantial watershed connectivity and anthropogenic influence. Here, we present data from aquatic invertebrate surveys conducted in two Lake Superior parks that are distanced from such watersheds and pressures, namely Apostle Islands National Lakeshore (APIS) and Isle Royale National Park (ISRO). Our intensive, multi-gear surveys from 99 APIS stations in 2017 and 165 ISRO stations in 2012 reveal a broad diversity of zooplankton and benthic/littoral macroinvertebrate taxa. Park samples yielded 29 zooplankton and >300 benthic/littoral taxa, with richness exceeding that of comparable nearshore datasets, especially for aquatic insects, leeches, and mites. Station depth was a major factor structuring invertebrates, and benthic/littoral densities were highest and composition most diverse at shallow stations having aquatic vegetation. Species composition and taxa accumulation patterns differed considerably among sampling gears, highlighting the value of multi-gear surveys. Several park mollusk and insect species matched ‘special concern’ listings, and two non-native cladocerans were very abundant. These two surveys added 11 new species to the aquatic macroinvertebrates known from Lake Superior, highlighting the importance of these parks in harboring biodiversity and the importance of individualized assessments of places not well represented in more routine lakewide biological monitoring. Our data are available as baselines for future biological surveys and trend assessments.

Community Structure of Mollusca (Gastropoda and Bivalvia) at Toronipa Beach

Toronipa Beach is known to have high biodiversity, especially in the Mollusca community such as Gastropoda and Bivalvia. However, research on the distribution and abundance of Mollusca species in this area, especially related to environmental changes, is still limited. To fill this gap, an analysis study was conducted on the structure of the Toronipa Beach Mollusca community as a basis for effective conservation efforts. Data were collected through purposive sampling methods at three different locations, then analyzed using the Shannon-Wiener Index method, evenness index, and dominance index. The results showed that the North of Toronipa Beach had the highest diversity with a Simpson index of 0.91, followed by the West with 0.76, and the East with 0.75. These differences in diversity reflect variations in microhabitats, such as substrates, water flow, and human activities, which affect the distribution and abundance of species. This study highlights the importance of proper management and conservation to maintain biodiversity in Toronipa Beach and provides a basis for further studies on the impacts of the environment and climate change on coastal ecosystems.

Snails of ‘sky islands’ above an equatorial desert: Terrestrial molluscs on four isolated mountain ranges in northern Kenya

AbstractThe mountains of northern Kenya (Ndoto, Nyiro, Kulal and Marsabit) are separated by semi‐arid plains uninhabitable for most terrestrial molluscs (snails and slugs). Nevertheless, each “sky island” supports a little‐known forest mollusc fauna. The diversity and endemism of these faunas are addressed here based on surveys and the limited records available in the literature. In total 75 forest mollusc species and subspecies were found, including six previously undescribed Streptaxidae and many first records. Most previously recorded taxa were refound. The richness of faunas is broadly comparable to that of other Kenyan forests surveyed using similar methods (Ndoto 41 taxa, Nyiro 40, Kulal 33, Marsabit 34). A large proportion of the forest taxa (24 taxa, 29%) are endemic to Kenya north of the Mathews Range. More than half of these (14 taxa, 17% of the total) are known only from a single mountain range. At Nyiro, where different forest types were compared, fewer endemic species were found in Juniper forest than in other forest types. Moving northwards along the Ndoto‐Nyiro‐Kulal chain, diversity declines while endemism increases, perhaps reflecting increasing isolation from the southern forests, but the trends are not significant when Marsabit is included. Across the four ranges, neither diversity nor endemism is clearly linked to the isolation, maximum elevation, forest cover or geological origin of each range (Kulal and Marsabit are volcanoes, while Nyiro and Ndoto are uplifted basement rock). Instead, the unique circumstances of each range create a distinctive set of isolated faunas.

Genome-wide identification of the PP1 and PPP1R3 gene family in oyster Crassostrea gigas: Unraveling their roles in glycogen metabolism

High glycogen in oysters contributes to their flavor, quality, and hardiness, making it a crucial target trait for breeding purposes. Until now, the upstream regulatory mechanism for glycogen synthesis has remained unclear. Protein phosphatase-1 regulatory subunit 3 (PPP1R3) is a member of a family that directs the protein phosphatase-1 (PP1) to glycogen, resulting in the activation of glycogen synthase (GS) and the inactivation of glycogen phosphorylase (GP). However, their functions in molluscan species have remained unclear until now. In our study, we verified the function of the PP1α/PPP1R3D pathways in the glycogen metabolism process in Crassostrea gigas. Initially, we conducted a phylogenetic analysis and identified two PP1 and PPP1R3 members in molluscan species, emphasizing copy number variations in eukaryotic animals. Additionally, we identified distinct substitutions of conserved motifs specific to bivalves, Cephalopoda, or Gastropods, revealing functional diversity in PP1 and PPP1R3. Our primary focus was on PP1α/PPP1R3D in the oyster C.gigas, detected in the muscle glycogen fraction of bivalve species, with mRNA expression showing a positive correlation with glycogen content. By manipulating CgPPP1R3D expression in oysters through adenovirus-mediated overexpression or siRNA-mediated downregulation, we established a direct positive correlation between CgPPP1R3D expression levels and glycogen content. Colocation analysis confirmed protein interactions between CgPP1α and CgPPP1R3D. Furthermore, to elucidate the correlation between gene expression and glycogen accumulation, we conducted an association analysis and identified a cluster of significant SNP loci upstream of CgPPP1R3D significantly related to glycogen content. The high polymorphism observed may be linked to differential expressions of CgPPP1R3D in oyster individuals with high and low glycogen levels. These findings serve as a crucial reference for enhancing glycogen traits in molluscan species.

Century‐scale loss and change in the fishes and fisheries of a temperate marine ecosystem revealed by qualitative historical sources

AbstractPolicies aiming to restore ecosystems, achieve thriving fisheries and reverse biodiversity loss require knowledge of their former status and long‐term variation. As quantitative fish data is typically only available for recent decades long after changes may have occurred, a greater use of qualitative sources has been encouraged in marine historical ecology. We examined diverse historical information (including maritime history, fisheries reports, naturalists' accounts, recipes, nautical charts and newspapers) across a multi‐century time span (13th–20th century) for a wide range of species to document their long‐term trajectories in an understudied Northeast Atlantic ecosystem (Irish Sea coast of Wales). We find strong evidence of the loss of both a pelagic fishery for herring, which was of fundamental socio‐ecological importance since at least the 13th century, and the loss of significant multi‐species demersal and intertidal fisheries. Local, commercial and/or functional extinction has occurred for taxa spanning a wide range of diversity (crustacean, elasmobranchs, sturgeon, and teleosts), body size and ecological role, suggesting far‐reaching changes to food webs. This raises fundamental questions about the present‐day health and integrity of this coastal ecosystem and the long‐term viability of current fisheries which depend on a few shellfish species. Our century‐scale synthesis of qualitative data for multiple taxa allows the collective breadth of losses to be fully appreciated and may reduce the risk of ‘shifting baselines’. Restoration to historical baselines may not be achievable, but our findings provide evidence of long‐term change relevant to policies for recovery, and prevention of further decline of fishes, fisheries and ecosystems.

Shellfish CO2 excretion is modulated by seawater carbonate chemistry but largely independent of pCO2.

Four species of shellfish, blue mussel (Mytilus galloprovincialis), Pacific abalone (Haliotis discus hannai), zhikong scallops (Chlamys farreri), and Pacific oyster (Crassostrea gigas), were exposed to decoupled carbonate system variables to investigate the impacts of different seawater carbonate parameters on the CO2 excretion process of mariculture shellfish. Six experimental groups with two levels of seawater pH (pH 8.1 and pH 7.7) and three levels of total alkalinity (TA = 1000, 2300, and 3600μmol/kg, respectively) were established, while pH 8.1 and TA = 2300μmol/kg was taken as control. Results showed that the CO2 excretion rates of these tested shellfish were significantly affected by the change in carbonate chemistry (P < 0.05). At the same TA level, animals incubated in the acidified group (pH 7.7) had a lower CO2 excretion rate than those in the control group (pH 8.1). In comparison, at the same pH level, the CO2 excretion rate increased when seawater TA level was elevated. No significant correlation between the CO2 excretion rate and seawater pCO2 levels (P > 0.05) was found; however, a significant correlation (P < 0.05) between CO2 excretion rate and TA-DIC (the difference between total alkalinity and dissolved inorganic carbon) was observed. Blue mussel has a significantly higher CO2 excretion rate than the other three species in the CO2 excretions per unit mass of soft parts, with no significant difference observed among these three species. However, in terms of CO2 excretion rate per unit mass of gills, abalone has the highest CO2 excretion rate, while significant differences were found between each species. Our studies indicate that the CO2 buffering capacity impacts the CO2 excretion rate of four shellfish species largely independent of pCO2. Since CO2 excretion is related to acid-base balancing, the results imply that the effects of other carbonate parameters, particularly the CO2 buffering capacity, should be studied to fully understand the mechanism of how acidification affects shellfish. Besides, the species difference in gill to soft parts proportion may contribute to the species difference in responding to ocean acidification.

Studies on Benthic Fauna with relation to physio chemical parameters in Betana Wetland, Morang, Nepal

This study examined the benthic fauna and its relation to the physic chemical parameters in Betana wetland, Morang, Nepal from December 2020 to May 2021. Over the course of six months, the study found two genera of Annelida (Hirudinea and Lumbricina), eight genera of Arthropoda (Macrobranchium, Chironomus, Cyclops, Cypridopsis, Blasturus, Diptera, Coeleptera, and Naupli), and four species of Mollusca (Bellamya bengalensis, Parreysia flavidens, Lamellidens marginalis, and Indoplanorbis exutus). Arthropods were more prevalent in the spring due to the increase in temperature. The average maximum water temperature was 23.66°C in the spring and the minimum was 20.25°C in the winter. The maximum soil temperature was 24.9°C in the spring and the minimum was 21.08°C in the winter. The pH was highest in the spring (7.67) and lowest in the winter (7.21). The highest dissolved oxygen (DO) was found in the winter (7.6 mg/l) and the lowest was in the spring (7 mg/l). The maximum free CO₂ was found in the spring (26.83 mg/l) and the minimum was in the winter (21.25 mg/l). Total alkalinity was highest in the spring (113 mg/l) and lowest in the winter (105 mg/l). Total hardness was highest in the spring (83.51 mg/l) and lowest in the winter (69.25 mg/l). Water temperature and soil temperature had a high correlation coefficient (0.93) with benthic fauna, while DO and pH showed a high negative correlation coefficient (-0.93 and -0.92), respectively.

Highly defended nudibranchs "escape" to visually distinct background habitats.

The "escape and radiate" hypothesis predicts that once species have evolved aposematism, defended species can utilize more visually diverse visual backgrounds as they "escape" the need to be well camouflaged. This enables species to explore new ecological niches, resulting in increased diversification rates. To test this hypothesis "escape" component, we examined whether the background habitats of 12 nudibranch mollusk species differed among species depending on the presence and strength of chemical defenses. We obtained a rich array of color pattern statistics using quantitative color pattern analysis to analyze backgrounds viewed through the eyes of a potential predator (triggerfish, Rhinecanthus aculeatus). Color pattern analysis was done at viewing distances simulating an escalating predation sequence. We identified 4 latent factors comprising 17 noncorrelated color pattern parameters, which captured the among-species variability associated with differences in chemical defenses. We found that chemically defended species, indeed, were found on visually distinct backgrounds with increased color and luminance contrast, independent of viewing distance. However, we found no evidence for increased among-species background diversity coinciding with the presence and strength of chemical defenses. Our results agree with the "escape and radiate" hypothesis, suggesting that potent chemical defenses in Dorid nudibranchs coincide with spatiochromatic differences of visual background habitats perceived by potential predators.

Molluscan pleiotropic FADD involved in innate immune signaling and induces apoptosis

Fas-associated protein with death domain (FADD) was initially identified as a crucial adaptor protein in the apoptotic pathway mediated by death receptor (DR). Subsequently, many studies have confirmed that FADD plays a vital role in innate immunity and inflammatory responses in animals. However, the function of this pleiotropic molecule in mollusk species has not been well explored. In this study, we successfully verified the gene sequence of FADD in the Zhikong scallop (Chlamys farreri) and designated it as CfFADD. The CfFADD protein contains a conserved death effector and death domains. Phylogenetic analysis showed that CfFADD is a novel addition to the molluscan FADD family with a close evolutionary relationship with molluscan FADD subfamily proteins. CfFADD mRNA expression in various scallop tissues was significantly induced by challenge with pathogen-associated molecular patterns (lipopolysaccharide, peptidoglycan, and poly(I:C)), suggesting its role in innate immunity in scallops. Co-immunoprecipitation showed that CfFADD interacted with the scallop DR (tumor necrosis factor receptor) and a signaling molecule involved in the Toll-like receptor pathway (interleukin-1 receptor-associated kinase), confirming that CfFADD may be involved in DR-mediated apoptosis and innate immune signaling pathways. Further studies showed that CfFADD interacted with CfCaspase-8 and activated caspase-3. HEK293T cells exhibited distinct apoptotic features after transfection with a CfFADD-expression plasmid, suggesting a functional DR-FADD-caspase apoptotic pathway in scallops. Overexpression of CfFADD led to a significant dose-dependent activation of interferon β and nuclear factor-κB reporter genes, demonstrating the key role of CfFADD in innate immunity. In summary, our research has confirmed the critical roles of CfFADD in innate immunity and apoptosis and provides valuable information for developing comparative immunology theories.

Redescription of Melibe japonica (Nudibranchia: Dendronotoidea: Tethydidae) and its phylogenetic relationship in the genus

ABSTRACT Melibe japonica is a species of gastropod mollusc originally described as a large (up to 70 cm), translucent yellow-white nudibranch with a strong reddish tinge in parts. Subsequent studies reported that it has reddish tubercles all over its translucent pinkish body and cerata. However, it has recently been suggested that M. japonica is a synonym of Melibe viridis without any discussion or explanation. This study aims to show that M. japonica is a valid species. Due to the state of preservation of the type material of M. japonica, neither morphological nor genetic studies were possible, so a neotype for the species was provisionally designated. We provide a detailed description of its external morphology, internal anatomy and phylogenetic relationship, using fresh and preserved specimens collected in Japan. We also extend and update its geographic distribution.

Morphometric features of larvae of the mussel Mytilus galloprovincialis (Lamarck, 1819) (Bivalvia: Mytilidae) in ontogenesis

Sequentially appearing in ontogenesis, the morphometric features of mussel Mytilus galloprovincialis larvae can serve as a basis for their species identification among the pool of larvae of other bivalve mollusc species found in the Black Sea plankton. The study presents the photographs of live mussel larvae and scanning electron microscope (SEM) images of the larvae hinge at different developmental stages: D-veliger, veliger, veliconcha and pediveliger. There was shown the sequence of morphological changes in provinculum, as well as the shell’s size and shape changes, from the earliest straight-hinge stage of veliger up to metamorphosis. The correlation between shell width (C, µm) and shell length (L, µm) [ ; R2 = 0.9879], as well as the correlation between hinge edge length (l, µm) and shell length (L, µm) [ ; R2 = 0.9872] were determined for mussel larvae ranging in size from 98 to 350 µm. By employing energy dispersive X-ray spectroscopy EDS(x), the elemental composition of the larvae shell’s hinge edge at the stages of veliger, veliconcha and pediveliger was determined; and it showed the presence of calcium, carbon, oxygen, sodium and chlorine. Magnesium was detected in pediveligers’ hinge edge only.

Prevalence of Pseudomonas and Vibrio Species in Shellfish with Special Reference to Their Susceptibility to Antibacterial Agents, Toxigenic and Virulent Genes

Prevalence of Pseudomonas and Vibrio Species in Shellfish with Special Reference to Their Susceptibility to Antibacterial Agents, Toxigenic and Virulent Genes

Harmozica ravergiensis (Gastropoda: Hygromiidae) in Western Ukraine as part of anthropogenic expansion of its range

In September 2023, a large population of the Caucasian snail Harmozica ravergiensis was discovered in a newly built residential complex in Lviv. This is its second record in Western Ukraine, with an interval of almost 20 years, as well as the westernmost known locality of the species. Adults of H. ravergiensis from Lviv had larger shells compared to samples from other introduced Eastern European populations of this species, measured by us personally or described in the literature. Another 16 species of land molluscs, mostly alien to Ukraine or its western part, were found in Lviv together with H. ravergiensis. The latter includes a snail of Crimean origin, Monacha fruticola, which is still rarely recorded north of the steppe zone of Ukraine. In the studied area of Lviv, H. ravergiensis and M. fruticola often formed joint aggregations, which had never been observed before in Ukraine. Possible ways of penetration of H. ravergiensis and some other introduced molluscs into the studied area are discussed. Now H. ravergiensis is most often found in Eastern Ukraine, especially in the Donetsk region (the earliest known record dates back to 1990). There are also a few reliable finds in Western (since 2006) and Central (since 2015) Ukraine. In general, in the late 20th and early 21st centuries, the range of H. ravergiensis expanded significantly, reaching the Tver region of Russia in the north, the southern Ural in the northeast, Central Asia in the southeast, and Western Ukraine in the west. Here, we analyse for the first time the extent of this expansion based on personally studied material, published data, and images in two citizen science databases.

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Al-Dalmaj marsh is one of the most important marshes in Iraq; it extends from Al-Qadisiyah Province in the west to Wasit Province in the east, south of the Tigris and Euphrates Rivers. In order to study the malacological diversity of this site, a survey of the marsh molluscs species was made during this study. About 177 specimens were collected, seven species of gastropods belonging to six families and two species of Bivalves belonging to one family were identified, remarks on the nomenclature, taxonomy and distribution of these species. According to this study Al-Dalmaj Marsh includes diverse molluscs species and the presented results will provide important information for future studies concerned with the molluscs or Invertebrates biodiversity state of this important ecosystem in Iraq.

Drivers for the Diversity of Mollusc Communities in Unique Calcareous Fen Habitats

The research was carried out in calcareous fen habitats which share coverage with Natura 2000 sites designated under the EU Habitats and the Birds Directive. A total of 27 taxa of molluscs were recorded: 23 gastropod and 4 bivalve species. Anisus vorticulus, one of the species of Community interest whose conservation requires designation of special conservation areas within the Habitats Directive Natura 2000, was subrecedent and accedent in mollusc communities. Calcareous fen habitats offer the aquatic organisms harsh environmental conditions including a relatively high temperature of the water up to 33.29 °C (undrained fens), oxygen deficits in the water, high pH of up to 11.08 (fen pools) and conductivity above 3000 μS cm−1 (fen ditches). Therefore molluscs have to face extreme environmental conditions. Temperature of the water, pH, dissolved oxygen and conductivity were the parameters most associated with the distribution of mollusc species in the calcareous fen habitats. The abundance of submerged and floating macrophytes, the degree of habitat persistence and the fish predation pressure on molluscs also exerted a significant effect on their distribution. The calcareous fen habitats that are listed in Annex I of the European Union Habitats Directive create a unique valuable ecosystem that contributes to the natural diversity of aquatic organisms.

Preliminary Analysis of Hydrodynamic Drag Reduction and Fouling Resistance of Surfaces Inspired by the Mollusk Shell, Dosinia juvenilis.

Many species of plants and animals show an ability to resist fouling with surface topographies tailored to their environments. The mollusk species Dosinia juvenilis has demonstrated the ability to resist the accumulation of fouling on its outer surface. Understanding the functional mechanism employed by nature represents a significant opportunity for the persistent challenges of many industrial and consumer applications. Using a biomimetic approach, this study investigates the underlying hydrodynamic mechanisms of fouling resistance through Large Eddy simulations of a turbulent boundary layer above a novel ribletted surface topography bio-inspired by the Dosinia juvenilis. The results indicate a maximum drag reduction of 6.8% relative to a flat surface. The flow statistics near the surface are analogous to those observed for other ribletted surfaces in that the appropriately sized riblets effectively reduce the spanwise and wall-normal velocity fluctuations near the surface. This study supports the understanding that nature employs ribletted surfaces toward multiple functionalities including the considered drag reduction and fouling resistance.

Diversification of von Willebrand Factor A and Chitin-Binding Domains in Pif/BMSPs Among Mollusks

Pif is a shell matrix protein (SMP) identified in the nacreous layer of Pinctada fucata (Pfu) comprised two proteins, Pif97 and Pif 80. Pif97 contains a von Willebrand factor A (VWA) and chitin-binding domains, whereas Pif80 can bind calcium carbonate crystals. The VWA domain is conserved in the SMPs of various mollusk species; however, their phylogenetic relationship remains obscure. Furthermore, although the VWA domain participates in protein–protein interactions, its role in shell formation has not been established. Accordingly, in the current study, we investigate the phylogenetic relationship between PfuPif and other VWA domain-containing proteins in major mollusk species. The shell-related proteins containing VWA domains formed a large clade (the Pif/BMSP family) and were classified into eight subfamilies with unique sequential features, expression patterns, and taxa diversity. Furthermore, a pull-down assay using recombinant proteins containing the VWA domain of PfuPif 97 revealed that the VWA domain interacts with five nacreous layer-related SMPs of P. fucata, including Pif 80 and nacrein. Collectively, these results suggest that the VWA domain is important in the formation of organic complexes and participates in shell mineralisation.