Alan Kohn was a remarkable malacologist with a diversity of research interests that extended beyond the study of the Conidae (Gastropoda) to a wide range of mollusks, other marine invertebrates, and the history of biology. He mentored several generations of undergraduate and graduate students, post-doctoral fellows, and junior colleagues, encouraging them to go beyond what they thought they could do, and supporting them wherever their careers took them. He also taught hundreds of students over nearly four decades, including the signature Invertebrate Zoology course at the University of Washington, both on the main campus and at the Friday Harbor Laboratories. He also was an instructor in the courses of the Tropical Marine Mollusc Programme (Thailand) and the National Workshop on Marine Molluscs (Vietnam). Kohn was active in several scientific societies, serving as President of the American Malacological Union, Pacific Division; President of the American Malacological Union; and President of the Society of Integrative and Comparative Biology. His publications focused on the ecology, systematics, and biogeography of the Conidae, using the species of that family as model organisms to provide broader insights for the study of marine life and to address key ecological and biogeographical questions. He wrote numerous book reviews that were not only informative but also helped broaden his perspective across biology and paleontology.

Nearly 70 years ago, the fish-hunting strategy of the marine gastropod snail Conus striatus Linnaeus, 1758, was unveiled for the first time. Now, Conus striatus is one of the most recognizable and most studied conids, and some toxins (conotoxins) have been characterized from its venom. In his pioneering work, Alan Kohn showed that upon injection of venom through a harpoon-like modified radular tooth, the fish prey of Conus striatus is rapidly immobilized, within a few hundred milliseconds to a couple of seconds. The cocktail of conotoxins induces strong tetanic contractions of all muscles, with visible fasciculation (twitching) of the fish's fins. In this review, we wish to honor the memory of Alan Kohn by summarizing the current knowledge of the venom composition and biological activity of conotoxins of Conus striatus. From the 103 entries of conotoxins from Conus striatus that occur in the Conoserver database, 74 are mature conotoxin sequences and only a dozen or so have been pharmacologically characterized. Surprisingly, the major toxin class responsible for the “taser-like” effect in fish originally observed, the kA-conotoxins, remains poorly understood. Only one three-dimensional structure is known, and the molecular target and mode of action are at best uncertain. This clearly highlights that, despite the vast amount of data accumulated over the years, even for such heavily investigated species as Conus striatus, many important questions remain.

Alan Kohn showed that two cone-snail species—Conus striatus Linnaeus, 1758, and Conus catus Hwass, 1792—hunt fish as their primary prey. In the seven decades since then, it has been established that these two species belong to the subgenus Pionoconus Mörch, 1852, a well-defined lineage of Conus Linnaeus, 1758, and one of eight piscivorous cone-snail clades. In this review, an integrated multidisciplinary framework for the biology of Pionoconus is presented, based on the numerous research papers published since Kohn's seminal discovery. The molecular biology, phylogeny, biogeography, life history, and prey-capture strategy of Pionoconus are among the topics reviewed, along with more specialized subjects, e.g., human envenomation, culinary recipes, shell-collecting history, and biomedical applications. These illustrate the continuing impact of Kohn's scientific contributions.

A review of valid species within genus Pygmaeconus Puillandre & Tenorio, 2017, is presented. Combined analysis of molecular [partial mitochondrial cytochrome c oxidase subunit I (cox1) gene sequences of several individuals, and a nearly-complete mitogenome for one individual] and morphological (shell and radular tooth) characters revealed that tiny cone snails collected with algae and shell grit by scuba at 12 m depth in the southeastern Philippines correspond to a new species, introduced here under the name Pygmaeconus atomus sp. nov. It attains a maximum adult size of < 5 mm, being arguably the smallest recorded member of the cone-snail fauna worldwide.

The genus Conasprella Thiele, 1929 is the second largest in the family Conidae. It encompasses 161 described species that mainly occur at bathyal depths. Despite this relatively high species diversity, species delimitation and taxonomy of the genus have barely been addressed with molecular data. In the present study, we revisit species delimitation in the Indo-Pacific Conasprella orbignyi complex based on data from a previous study and substantial original data. Integrative taxonomy applied to a dataset comprising 82 specimens revealed ten putative species, and available names were assigned to seven of them. Two unnamed species are new and described here as Conasprella zinaidae Fedosov & Puillandre, n. sp. (represented by a single sequenced specimen from Papua New Guinea) and Conasprella emilieae Puillandre & Fedosov, n. sp. (represented by four sequenced specimens, all from Papua New Guinea). Some populations within the Conasprella orbignyi complex show weak genetic structure but unusually high morphological variation, which overlaps differences among genetically distinct species. This variation renders identification of both new species on conchological grounds problematic. Therefore, we provide DNA-based diagnoses for both new species to facilitate their identification in future studies.

The enormous diversity of Conidae in the Indo-West Pacific (IWP) makes the group an attractive model for testing tropical marine diversification, but its incredible richness makes species delineation challenging. Throughout his career, Alan Kohn championed an integrative taxonomic approach and a deep study of variation to delimit cone-snail species to understand this radiation. Most recently, sequence data has provided objective measures of genetic connectivity of populations and is helping to test species limits in light of distributions and ecologies. To expand and better frame our understanding of cone diversity, we provide a broad overview of the cones of Oman, a previously genetically poorly sampled area of the world ocean with unusual and heterogeneous oceanography, where corals and kelp mix, and seasonal upwelling and oxygen minimum zones influence ecosystems. We provide mitochondrial sequence data for 30 of the 54 nominal species recorded from Oman based on new collections and analyze genetic differentiation across the IWP based on available comparative sequence data. We found that endemism is remarkable, with 37–41% of genetically characterized species and 53–56% of all species unique to Oman, Arabia, or the Arabian Sea. Several wide-ranging cone species are geographic mosaics, composed of divergent, allopatric populations, fitting Mayr's concept of polytypic species. Genetic data show other putative endemic species to be genetically connected to species outside the region, suggesting that they are variants, rather than species. These include Conus nigropunctatus G. B. Sowerby II, 1858 (= C. catus Hwass, 1792), C. sumatrensis Hwass, 1792 (= C. vexillum Gmelin, 1791), and C. thomasi G. B. Sowerby III, 1881 (= C. terebra Born, 1778). Life history is an important determinant of endemism. Nearly all (94%) of the broadly distributed IWP species have multispiral protoconchs suggestive of longer planktonic development and exchange potential, whereas two-thirds of regional endemics do not, indicating more restricted geographic exchange.

The diverse shell color patterns of cone snails have attracted the interests of collectors, artists, and scholars for centuries, but their means of construction by the living animal and biological functions, if any, remain poorly understood. What little information that we know is summarized, areas of future study are highlighted, and a new layer-based framework for classification of shell color-pattern elements is presented with modern and fossil examples to help spur future study. Finally, an argument is presented that the color patterns of cone snails likely have little, if any, adaptive or functional significance. Conasprella (Ximeniconus) onisca (Woodring, 1928) is presented as a new combination.

Sensory biology is a critical component of organismal fitness and selection on sensory traits can drive macroevolutionary processes like speciation. Among mollusks, chemosensation (the detection of chemical signals) is an important sensory modality. The functional basis of chemosensation is a suite of olfactory receptor (OR) genes, but despite their importance to molluscan life history, ecology, and evolution, these genes remain poorly characterized for this highly diverse phylum. Here, we explore molluscan biology through this novel lens, using transcriptomics to characterize the olfactory receptor (OR) gene repertoires of Conus ebraeus Linnaeus, 1758 and C. judaeus Bergh, 1895—a pair of closely related, co-occurring gastropod species that exhibit fine-scale niche partitioning. We identify candidate OR genes, construct a gene tree for this gene family, and compare its structure and composition between these two species. We measure and compare gene expression of candidate OR genes, test for differential expression of orthologous loci, and compare patterns of sequence evolution between paralogous and orthologous loci to determine if gene family diversification occurs within or between species. Finally, we compare rates of evolution between ortholog pairs to identify genes showing evidence of differential selective pressures. Although C. ebraeus and C. judaeus share similar OR gene family repertoires, some genes showed divergence in terms of patterns of expression and modes of selection, which suggests the adaptive evolution of olfactory abilities among species. This is the first study to characterize the genetic basis of olfaction in Conus Linnaeus, 1758 and provides a genetic foundation for understanding how sensory biology can contribute to the rapid diversification of this genus.

Characteristics of cone snail (family Conidae) populations and communities are predicted to differ depending on habitat type. In particular, high wave energy and greater exposure at low tides are posited to restrict body sizes of cones at intertidal marine benches in comparison to subtidal reefs. Here, we tested this prediction by comparing shell sizes of cone-snail species that occur at both seaward and lagoonal sites at two atolls in the Tuamotu Archipelago: Makemo and Rangiroa. At Makemo, we also compared sizes of individuals from a seaward site, sites within a small channel or “hoa” that allows water exchange between the sea and lagoon, and sites at increasing distances from the hoa for species that occurred at these sites. Although eight species with adequate sample sizes for analyses occurred at both seaward and lagoonal sites at Rangiroa, we only observed sufficient sample sizes of two species at both seaward and lagoonal sites at Makemo. All of these species exhibited significantly larger body sizes at lagoonal sites that are largely composed of subtidal reefs than at seaward sites that represent intertidal marine benches. These results support the prediction that habitat type influences the body size of cone snails. We also found that body sizes of cone snails steadily increased from the seaward site, through the hoa, and with increasing distance from the hoa in the lagoon. These results as well as our infrequent observations of small-sized individuals at lagoonal sites suggest that cone-snail larvae settle at seaward sites and individual snails migrate through hoas and contribute to recruitment of lagoonal populations.

Episodic mortalities in October 1985 and December 2023 are recorded for mollusks and other organisms on intertidal platforms in the Perth metropolitan region of Western Australia (WA) during periods of elevated air temperatures that coincided with lunar low spring tides. This was similar to mortalities previously reported for the western end of Rottnest Island, offshore from Perth, and are natural occurrences. Mollusks on the Rottnest platforms decreased substantially in both diversity and density between 2007 and 2021. This was thought to be due to a severe marine heatwave along the WA western coast in 2011 caused by global warming, unlike the mortalities observed during this study in 1985 and 2023, which were caused by a combination of high air temperatures and low spring tides. Because marine heatwaves are increasing in frequency and intensity, it is important to distinguish their impacts from previously occurring natural events associated with high air temperatures coinciding with low spring tides.

In a recent phylogenetic study of Mesoamerican freshwater mussels (Bivalvia: Unionidae), new molecular support for the tribe Popenaiadini was presented. Several genera of Mesoamerican mussels, including Nephronaias Crosse & Fischer, 1894, were predicted to be within the Popenaiadini tribe based on morphology, but this hypothesis had not been tested with molecular data. Several freshwater mussel specimens were recently collected in Guanacaste Province, Costa Rica. Based on the morphology of the specimens, the known distribution of Nephronaias in Costa Rica, and examination of specimens in the Zoology Museum of the University of Costa Rica, this species was identified as Nephronaias tempisquensis Pilsbry, 1920. After amplifying a gene extension characteristic of the male-transmitted genomes of freshwater-mussel species exhibiting doubly uniparental inheritance (DUI) of mitochondrial DNA, it was concluded that N. tempisquensis exhibits DUI. Phylogenetic analyses of a combination of male- and female-transmitted mtDNA gene sequences and one nuclear gene region are consistent with the hypothesis that N. tempisquensis is a member of the Popenaiadini tribe and is closely related to the Mesoamerican Psoronaias/Psorula species complex. In addition to providing novel sex-related mtDNA data, the current study presents the first DNA sequence data for the genus Nephronaias and among the first molecular data published for native freshwater mussels from Costa Rica.

Although the life history of the invasive terrestrial slug Arion vulgaris Moquin-Tandon, 1855 has been well studied, there are no long-term studies on the variation in its abundance. In 2003–2022, we used plasticine baits to monitor annual fluctuations in the abundance of a local Arion vulgaris population in Central Europe and studied the factors that influence these fluctuations. The consumption of plasticine, which is a reliable proxy of the abundance of slugs, varied between different years by a factor of 43. The maximum intensity of consumption occurred in July. The variability in slug abundance, as estimated from plasticine bait consumption, was irregular across years. Oviposition took place from September–November. The number of eggs laid did not limit the abundance of the filial generation. Slugs spent the winter period in the egg stage (∼25% of the population) or as juveniles, whose winter mortality varied from 18–100% among years. Winter temperatures were not a significant predictor of slug abundance in the following season, whereas the weather in spring and early summer determined the abundance. Amount of precipitation in April and May had a positive effect (P = 0.01). In contrast, the number of days from April–July in which minimum temperature at a depth of 2 cm below the surface exceeded 18°C (i.e., the optimum temperature for slug development) had a negative effect (P = 0.045). These two factors combined explained 55% of the interannual variability in slug abundance (r = 0.74). The robustness of these results was backed up by the data from a spatially isolated nearby population, showing similar patterns of annual changes in abundance.

Until now, an exhaustive list of Panamanian heterobranch sea slugs (Mollusca: Gastropoda) had not been made. Here, we present a descriptive list of all species of sea slugs off of the coasts of Panamá, based on published references and confirmed photographs of collected species. All publications referring to collections of these gastropods were compiled and examined, and specimens were collected from different coastal areas of Panamá. The resulting catalog contains 232 species of heterobranch sea slugs, of which 117 are found on the Caribbean coast and 127 are found on the Pacific coast. Eight species have a bicoastal distribution, and 18 species have an amphi-Atlantic distribution. This study confirms the high biodiversity of heterobranch sea slugs inhabiting the Panamanian coasts. However, because the Pacific coast has been less well studied, future research should include more extensive sampling in these locations.