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

In this study, we present mollusks of the family Caecidae Gray, 1850 collected between 2007 and 2008 from unconsolidated carbonate substrates of the Abrolhos coral bank during the PROABROLHOS Project (Productivity, Sustainability and Use of the Abrolhos Bank Ecosystem). A total of 649 individuals belonging to two genera and six species were collected from nine stations at depths of 15.6 to 22 m in the dry and rainy seasons. The most abundant species were Caecum brasilicum de Folin, 1874 and Caecum floridanum Stimpson, 1851. Caecum circumvolutum de Folin, 1867, Caecum metamorphosicum Lima, Santos & Absalão, 2013, Meioceras cubitatum de Folin, 1868 and Meioceras nitidum (Stimpson 1851) altogether comprised approximately 6.5% of the total number of individuals collected. Among the 14 species previously recorded for the Abrolhos coral reef area, Caecum metamorphosicum is for the first time registered in the area in this study. This calls attention that, overall, there is a need for more researches focused on the carbonate substrate in coral areas, especially on micro specimens.

A comparative burrowing study was performed using two estuarine clams, Rangia cuneata (G. B. Sowerby I, 1831) and Polymesoda caroliniana (Bosc 1801). These studies were carried out using three types of sediment (sand, silt, and clay) removed from the clam's native environment and placed into separate tanks. The number of burrowing events, in which the animals actively burrowed into the sediment, and the duration of time over which these events occurred were recorded and analyzed. There was a significant effect of sediment type on the number of burrowing events, but not so much on the duration of events. Pairwise comparisons between sediment types revealed subtle differences regardless of species. From these results, we report that sediment type can significantly influence the burrowing behavior of sympatric clams, but in different ways; and note observations on how these species physically interact and alter the substrate when burrowing.

The organic component of the molluscan shell allows for orderly biomineralization and ensures structural integrity that is crucial to survival. This organic contribution to the shell typically composes 2-5% of the total adult shell by weight. Because macro- and microstructure of the shell is known to vary with ontogeny and across taxa, we examined if the organic to mineral ratio components in shell also varied with growth across taxa. To assess intraspecific differences in the organic to mineral ratio of the shell during growth, we examined ratios in three marine [Crepidula fornicata (Linnaeus, 1758), Littorina littorea (Linnaeus, 1758), and Littorina saxatilis (Olivi, 1792)] and two freshwater [Corbicula fluminea (Müller, 1774) and Bellamya chinensis (Gray, 1834)] mollusks across size ranges. In the marine gastropods, the average organic component by weight of the small size class was significantly larger than the average organic proportions of the medium and large size classes. The smallest size class of L. saxatilis had an average shell organic proportion of 11.12%, while the smallest size classes of C. fornicata (3.53%) and L. littorea (2.60%) had percentages below 5%. The smallest size class of C. fluminea had a greater average shell organic proportion than the largest size class (6.19% vs 2.68% organics). Adult specimens of B. chinensis had an average shell organic proportion of 3.93%, while in utero shelled juveniles had an average of 10.05%. In both freshwater and marine species, the smallest size class had a greater organic proportion. As the organic matrix is energetically more expensive than the calcified shell portion, we hypothesize that energy expended in these smaller (usually pre-reproductive maturity) stages of growth allows for a more rapid production of shell and that this “expense” is a valuable trade-off for the protection the shell offers young mollusks.

Heteropods are predatory planktonic gastropods that are important in pelagic ecosystems. However, distributions of large heteropod species are poorly known. Heteropod collections from two midwater sampling programs conducted after the 2010 Deepwater Horizon oil spill (DWHOS): the Offshore Nekton Sampling and Analysis Program (ONSAP) in 2011 and the Deep Pelagic Nekton Dynamics of the Gulf of Mexico (DEEPEND) in 2015-2018 were used for this study These programs collected over 3,495 heteropods in the two target families from 46 sampling stations in the northern Gulf of Mexico (GOM). The zone along the northeastern GOM continental slope had the greatest species richness and abundances. The family Pterotracheidae (Pterotrachea coronata (Forsskal 1775), Pterotrachea hippocampus(Philippi 1836) and Pterotrachea scutata (Gegenbaur 1855) was the most abundant and contained the largest specimens examined. Common carinariids included Carinaria lamarcki (Péron & Lesuer 1810) and Cardiapoda placenta (Lesson 1830). We found evidence of diel migration in P. coronata and P. scutata but not for C. lamarcki, C. placenta or P. hippocampus. We evaluated body and eye size at capture depth for each species. There was no evidence of eye size increasing relative to body size with depth among the five species and relative eye size is species-specific. However, it was observed that vertical migrators had a different eye-type than the non-migrators. We determined that pterotracheids have smaller eyes relative to their total body size than carinariids. The allometric pattern of eye growth differed in P. scutata from those of the other species which could indicate that a factor other than depth plays a part in heteropod eye development. This is the first comprehensive study of large heteropods in the northern GOM which provides an important baseline for continued study of this pelagic gastropod.

Natural history collections are an invaluable resource that can inform systematic studies and biodiversity discovery, and also contribute to understanding changes in species abundance and distributions over time. The decline in abundance and diversity of Pacific Island land snails has been a major conservation concern for more than six decades, but only the largest and most colorful snails are protected under the US Endangered Species act, and few are listed as critically endangered on the IUCN Red List. Like most invertebrates, the conservation status of many Hawaiian land snails still need assessment. Molecular data are highly informative for revising species limits and understanding evolutionary patterns and processes, but with as much as 70% of Hawaiian land snails already extinct, few fresh samples are available from which to extract DNA. To overcome the lack of material suitable for DNA barcoding, we test whether short DNA fragments of 225 to 355 bp can be sequenced from museum snail shells containing dried tissues collected more than 50 years ago. Short DNA sequences (225 bp) were obtained from 66.7% of lots, while longer DNA sequences (355 bp) were successfully sequenced from 24.2% of lots. Snail specimens stored in natural history cabinets for more than 100 years were successfully sequenced, supporting the inclusion of these materials for modern biodiversity studies. Molecular data from this study represents a small proportion of Hawaiian microsnail species housed among the millions of specimens in the Bishop Museum in Hawaii and other natural history collections. Additional resources and focused efforts are needed to scale this approach to incorporate many more of the hundreds of snail species in need of assessment in Hawaii. More broadly, there are large representative collections of endangered Pacific Island non-marine snails in many natural history museums that may be suitable for molecular work, either with DNA barcoding or other genomic approaches.

The increased availability of publicly available, digitally accessioned biodiversity data and scientific literature presents the opportunity to reassess geographical associations of understudied taxonomic groups. Using these resources, in addition to occurrence data managed by the National Park Service at the Great Smoky Mountains National Park and private collections, we have assembled an updated taxonomic checklist and robust geographic dataset of all records of terrestrial gastropods (land snails and slugs) within the state of Tennessee. Additionally, we quantified spatial and taxonomic biases in survey coverage and overall survey quality for terrestrial gastropods at two spatial resolutions: ecoregion and county. Our state checklist includes 301 species of terrestrial gastropods that have at least one occurrence record, which increases the number of species by 40 from previous assessments of terrestrial gastropod biodiversity in Tennessee. Spatial analyses revealed < 33% of ecoregions and < 18% of counties to be sufficiently sampled for any terrestrial gastropod group as inferred by accumulation curves and the ratio between number of records to number of genera within each spatial unit. Significant biases in survey coverage in the state were revealed at both spatial scales, and a disproportionate number of occurrence records were found in the eastern portion of the state near urban centers, universities, and the Great Smoky Mountains National Park. Taxonomic diversity estimates were similarly biased. Moreover, larger snails comprise the vast majority of occurrence records compared to snails less than 5 mm in shell diameter and slugs. From a conservation perspective, the addition of many newly reported species requires updating status assessments, and the spatial and taxonomic bias reported here should act as an incentive for future targeted gastropod survey effort, particularly in western Tennessee.

The Fernando de Noronha Archipelago off NE Brazil harbors a few unique terrestrial gastropod species. One of them, the monotypic genus Ridleyconcha Christensen, 2020, presents such an idiosyncratic shell morphology that, in the 130 years since its description, it has been variously allocated in unrelated families: Streptaxidae, Endodontidae, Charopidae, Camaenidae, and Scolodontidae. Herein, R. quinquelirata is included into a molecular phylogenetic framework of stylommatophoran land snails to clarify its taxonomic position. The analysis supports the latest morphological revision classifying Ridleyconcha in Scolodontidae. Considering the present sampling, Ridleyconcha appears to be the sister taxa of Entodina Ancey, 1887.

A unique and rare event of consumption of a seabird (aviphagy) was recorded for a Southern Ocean squid in Australian waters. Petrel remains were identified in the stomach contents of a large (518 mm Mantle Length, 3.4 kg) female ommastrephid squid, Todarodes filippovae (Adam 1975) captured off the southern coast of Tasmania, Australia. The remains were identified as to being from either a fairy prion Pachyptila turtur or white-faced storm petrel Pelagodroma marina. This unique observation expands the evidence for aviphagy recorded in other cephalopods to now include squid.

Invasive mollusks pose a serious threat to global freshwater diversity and have been implicated in many ecosystem-altering invasion events over the past few decades. Biomonitoring surveys are therefore a key tool for ensuring biosecurity in diversity hotspots and vulnerable habitats. In this study, we use DNA barcoding to provide the first record of the viviparid, Sinotaia cf. quadrata (Benson, 1842) from North America. Reciprocal monophyly and low genetic divergence (uncorrected p-distance: 0.004) with a Bellamya quadrata (Benson, 1842) individual from the type region (China) provides strong support for this identification. The species was recovered as part of a routine biomonitoring survey of the Adirondack region of northern New York. Only three adults were recovered (no populations or juveniles) suggesting that the discovery represents a very recent arrival. Considering the proximity of the sampling site from the massive St. Lawrence River, it is likely that S. cf. quadrata was introduced into the St. Lawrence, probably via the aquarium plant trade, and was able to spread into smaller river system in northern New York and possibly other border states. This record represents the fourth alien viviparid, the third of which is of Asian origin that have made its way to New York waters. Future biomonitoring efforts for the upcoming summer period will involve targeted searches for S. cf. quadrata to determine the extent of its spread in the region.

All previously known localities of Pyrgophorus parvulus (Guilding, 1828) on the Caribbean island of Montserrat were destroyed by volcanic eruptions starting in 1995. Here we document a population in a freshwater stream only indirectly affected by that eruption. Specimens collected on Montserrat are morphologically consistent with P. parvulus and 16S DNA sequences indicate genetic consistency.

We investigated citric acid as a potential molluscicide and deterrent for the invasive slug species Arion fasciatus (Nilsson, 1823). To examine the efficacy of citric acid through ingestion or environmental exposure, slugs were given lettuce sprayed with 5% citric acid or 5% citric acid sprayed paper towels in no-choice tests. Slugs in choice tests were given both Romaine lettuce sprayed with 5% citric acid and DI water. We also investigated the impact of spraying Romaine lettuce seedlings with 5% citric acid to see if it impacts plant growth. No-choice tests revealed that environmental exposure to citric acid resulted in the eventual death of 64% of the slugs in the treatment group, while the ingestion of citric acid did not affect slug mortality. Choice tests revealed that citric acid significantly decreased Romaine lettuce herbivory. Romaine lettuce seedlings that were sprayed weekly for six weeks with 5% citric acid had a 31% lower biomass compared to the control, but no seedling deaths were observed. Overall, citric acid shows promise as a slug deterrent and molluscicide, though greenhouse and field trials are required to further elucidate its efficacy and impact on plants.

Machfudz Djajasasmita was an Indonesian malacologist who actively conducted research on Indonesian mollusks in the 20^th century. He was the first Indonesian mollusk curator at the Museum Zoologicum Bogoriense, Indonesian Institute of Sciences, replacing Louis Johan Marie (LJM) Butot. During his life, he described three species and two subspecies of mollusks: Corbicula lacunae, Pterocyclos spiroliratus, Amphidromus minutus, Amphidromus poecilochrous asmani, and Amphidromus poecilochrous candidus. Additionally, one gastropod species was described after him, i.e. Amphidromus djajasasmitai Dharma, 1993. All the holotypes of these species are deposited at the Museum Zoologicum Bogoriense. Djajasasmita contributed 765 specimen lots at the museum and produced at least 27 important publications during his active career. For his significant contributions and dedication in Malacology, the Indonesian Malacological Society awarded him ‘the Father of Indonesian Malacologists’.