Ellen E. Strong

We describe a new species of Solenogastres in the family Dondersiidae, Nematomenia quattriniae sp. nov ., using an integrative taxonomic approach. The species is characterized by a slender, light-yellow body with a scaly appearance and dorsal keel, prominent anterior pedal glands, a dorsal foregut gland, a single dorso-terminal sensory organ, and the presence of seminal receptacles and seminal vesicles. Specimens were collected from a bathyal site (581 m depth) on the continental slope off Louisiana (USA) associated with the hydrozoan Acryptolaria abies (Allman, 1877), which displayed signs of an active defense response. This study sheds light on the trophic ecology of solenogasters and highlights the continued discovery of novel biodiversity and predator-prey interactions in deep-sea ecosystems.

Solenogastres (Mollusca, Aplacophora) are a unique and understudied group of marine invertebrates of evolutionary and ecological significance. Their diversity remains underestimated due to frequent lack of identification by non-specialists, limited molecular data, and the complexity of their taxonomy. Here we present the first Solenogastres from Puerto Rico, expanding the group’s known geographic distribution in the Caribbean Sea. Using an integrative taxonomic approach, we describe two new species, Dorymenia gummi sp. nov. and Strophomenia boricua sp. nov. , and document their associations with coral hosts. These findings offer new insights into the ecology and biodiversity of these elusive mollusks.

Galeommatoidea are bivalves with small (usually 1–15 mm), fragile, sometimes vestigial, shells, occurring free-living or in association with other benthic invertebrates from the intertidal to depths in excess of 7,000 m. They are the most diverse but least studied and most underrepresented group of bivalves in biodiversity surveys and museum collections. The majority of commensal species of Galeommatoidea have dull, frequently uncoloured, unsculptured shells, but free-living species have papillate, sometimes coloured, mantles; they can be gregarious, and superficially resemble crawling gastropods. Many species of Galeommatoidea remain to be discovered, and we argue that future descriptions of free-living new species should ideally include photos of living animals, while many of the historically known species described based on their shells will probably be best treated as nomina dubia.

The superfamily Stromboidea is a clade of morphologically distinctive gastropods which include the iconic Strombidae, or ‘true conchs’. In this study, we present the most taxonomically extensive phylogeny of the superfamily to date, using fossil calibrations to produce a chronogram and extant geographical distributions to reconstruct ancestral ranges. From these results, we confirm the monophyly of all stromboidean families; however, six genera are not monophyletic using current generic assignments (Strombidae: Lentigo, Canarium, Dolomena, Doxander; Xenophoridae: Onustus, Xenophora). Within Strombidae, analyses resolve an Indo‐West Pacific (IWP) clade sister to an East Pacific/Atlantic clade, together sister to a second, larger IWP clade. Our results also indicate two pulses of strombid diversification within the Miocene, and a Tethyan/IWP origin for Strombidae—both supported by the fossil record. However, conflicts between divergence time estimates and the fossil record warrant further exploration. Species delimitation analyses using the COI barcoding gene support several taxonomic changes. We synonymise Euprotomus aurora with Euprotomus bulla, Strombus alatus with Strombus pugilis, Dolomena abbotti with Dolomena labiosa, and Dolomena operosa with Dolomena vittata. We identified cryptic species complexes within Terebellum terebellum, Lambis lambis, “Canarium” wilsonorum, Dolomena turturella and Maculastrombus mutabilis. We reinstate Rimellopsis laurenti as a species (previously synonymised with R. powisii) and recognise Harpago chiragra rugosus and Lambis truncata sowerbyi valid at the rank of species. Finally, we establish several new combinations to render Lentigo, Dolomena, and Canarium monophyletic: Lentigo thersites, Dolomena robusta, Dolomena epidromis, Dolomena turturella, Dolomena taeniata, Dolomena vanikorensis, D. vittata, “Canarium” wilsonorum, Hawaiistrombus scalariformis, Maculastrombus mutabilis, Maculastrombus microurceus.

The superfamily Stromboidea is a clade of morphologically distinctive gastropods which include the iconic Strombidae, or ‘true conchs’. In this study, we present the most taxonomically extensive phylogeny of the superfamily to date, using fossil calibrations to produce a chronogram and extant geographical distributions to reconstruct ancestral ranges. From these results, we confirm the monophyly of all stromboidean families; however, six genera are not monophyletic using current generic assignments (Strombidae: Lentigo, Canarium , Dolomena , Doxander ; Xenophoridae: Onustus, Xenophora ). Within Strombidae, analyses resolve an Indo-West Pacific (IWP) clade sister to an East Pacific/Atlantic clade, together sister to a second, larger IWP clade. Our results also indicate two pulses of strombid diversification within the Miocene, and a Tethyan/IWP origin for Strombidae – both supported by the fossil record. However, conflicts between divergence time estimates and the fossil record warrant further exploration. Species delimitation analyses using the COI barcoding gene support several taxonomic changes. We synonymise Euprotomus aurora with Euprotomus bulla , Strombus alatus with Strombus pugilis , Dolomena abbotti with Dolomena labiosa , and Dolomena operosa with Dolomena vittata . We identified cryptic species complexes within Terebellum terebellum , Lambis lambis , “Canarium” wilsonorum, Dolomena turturella and Maculastrombus mutabilis . We reinstate Rimellopsis laurenti as a species (previously synonymised with R. laurenti ) and recognise Harpago chiragra rugosus and Lambis truncata sowerbyi valid at the rank of species. Finally, we establish several new combinations, rendering Lentigo , Dolomena , and Canarium monophyletic: Lentigo thersites , Dolomena robusta , Dolomena epidromis , Dolomena turturella , Dolomena taeniata, Dolomena vanikorensis , D. vittata , “Canarium” wilsonorum , Hawaiistrombus scalariformis , Maculastrombus mutabilis , Maculastrombus microurceus .

Interspecific hybridization can lead to myriad outcomes, including transgressive phenotypes in which the hybrids are more fit than either parent species. Such hybrids may display important traits in the context of climate change, able to respond to novel environmental conditions not previously experienced by the parent populations. While this has been evaluated in an agricultural context, the role of transgressive hybrids under changing conditions in the wild remains largely unexplored; this is especially true regarding transgressive gene expression. Using the blue mussel species complex (genus Mytilus) as a model system, we investigated the effects of hybridization on temperature induced gene expression plasticity by comparing expression profiles in parental species and their hybrids following a 2‐week thermal challenge. Hybrid expression plasticity was most often like one parent or the other (50%). However, a large fraction of genes (26%) showed transgressive expression plasticity (i.e. the change in gene expression was either greater or lesser than that of both parent species), while only 2% were intermediately plastic in hybrids. Despite their close phylogenetic relationship, there was limited overlap in the differentially expressed genes responding to temperature, indicating interspecific differences in the responses to high temperature in which responses from hybrids are distinct from both parent species. We also identified differentially expressed long non‐coding RNAs (lncRNAs), which we suggest may contribute to species‐specific differences in thermal tolerance. Our findings provide important insight into the impact of hybridization on gene expression under warming. We propose transgressive hybrids may play an important role in population persistence under future warming conditions.

Terrestrial gastropods are among the most imperiled groups of organisms on Earth. Many species have a complex taxonomic history, often including poorly defined subspecies, most of which have not been the focus of modern systematics research. Genomic tools, geometric morphometrics, and environmental niche modeling were used to assess the taxonomic status of Patera clarkii nantahala (Clench & Banks, 1932), a subspecies of high conservation concern with a restricted range of approximately 3.3 km2 in North Carolina, USA. A genome-scale dataset was generated that included individuals with morphologies matching P. c. nantahala, P. c. clarkii, and one individual with an intermediate form between P. c. nantahala and P. c. clarkii that was initially hypothesized as a potential hybrid. Mitochondrial phylogenetics, nuclear species tree inference, and phylogenetic networks were used to assess relationships and gene flow. Differences in shell shape via geometric morphometrics and whether the environmental niches of the two subspecies were significantly different were also examined. Molecular analyses indicated an absence of gene flow among lineages of P. clarkii sensu lato. Analyses rejected our hypothesis that the intermediate shelled form represented a hybrid, but instead indicated that it was a distinct lineage. Environmental niche models indicated significant differences in environmental niche between P. c. clarkii and P. c. nantahala, and geometric morphometrics indicated that P. c. nantahala had a significantly different shell shape. Given multiple lines of evidence, species-level recognition of P. nantahala is warranted.

Juga is a genus of freshwater snails distributed from northern Washington to central California. The taxonomy and classification of the genus has a long and complex history, driven mainly by the features of their highly variable shells. The number of recognized species has fluctuated from ~9 to 11; however, it has been claimed that the actual diversity may be three times that number. We here present a systematic revision using a recently published molecular phylogeny as a framework, which supported the interpretation that there are only nine valid species. Comprehensive review of type material and original descriptions for all available species-group names indicates that almost all species previously considered valid were para- or polyphyletic grades of organization in shell morphology. Most species previously suggested to be putatively new were confirmed to be morphological variants of species already described. Species accounts include complete synonymies and partial chresonymies; the shells and radulae are illustrated and described. Lectotypes are designated for Melania plicifera Lea, 1838, M. silicula Gould, 1847, and M. rudens Reeve, 1860. Three species, Juga caerulea sp. nov., J. canella sp. nov., and J. douglasi sp. nov., are described as new and one species is excluded from the genus. The subgenera Calibasis D.W. Taylor, 1966 and Idabasis D.W. Taylor, 1966 are synonymized with Juga.

Planaxis sulcatus has been touted as a textbook example of poecilogony, with members of this wide-ranging Indo-Pacific marine gastropod said to produce free-swimming veligers as well as brooded juveniles. A recent paper by Wiggering et al. (BMC Evol Biol 20:76, 2020) assessed a mitochondrial gene phylogeny based on partial COI and 16S rRNA sequences for 31 individuals supplemented by observations from the brood pouch of 64 mostly unsequenced individuals. ABGD and bGYMC supported three reciprocally monophyletic clades, with two distributed in the Indo-Pacific, and one restricted to the northern Indian Ocean and Red Sea. Given an apparent lack of correlation between clade membership and morphological differentiation or mode of development, the reported 3.08% maximum K2P model-corrected genetic divergence in COI among all specimens was concluded to represent population structuring. Hence, the hypothesis that phylogenetic structure is evidence of cryptic species was rejected and P. sulcatus was concluded to represent a case of geographic poecilogony. Our goal was to reassess the case for poecilogony in Planaxis sulcatus with a larger molecular dataset and expanded geographic coverage. We sequenced an additional 55 individuals and included published and unpublished sequence data from other sources, including from Wiggering et al. Our dataset comprised 108 individuals (88 COI, 81 16S rRNA) and included nine countries unrepresented in the previous study. The expanded molecular dataset yielded a maximum K2P model-corrected genetic divergence among all sequenced specimens of 12.09%. The value of 3.08% erroneously reported by Wiggering et al. is the prior maximal distance value that yields a single-species partition in ABGD, and not the maximum K2P intraspecific divergence that can be calculated for the dataset. The bGMYC analysis recognized between two and six subdivisions, while the best-scoring ASAP partitions recognized two, four, or five subdivisions, not all of which were robustly supported in Bayesian and maximum likelihood phylogenetic analyses of the concatenated and single gene datasets. These hypotheses yielded maximum intra-clade genetic distances in COI of 2.56–6.19%, which are more consistent with hypothesized species-level thresholds for marine caenogastropods. Based on our analyses of a more comprehensive dataset, we conclude that the evidence marshalled by Wiggering et al. in support of Planaxis sulcatus comprising a single widespread, highly variable species with geographic poecilogony is unconvincing and requires further investigation in an integrative taxonomic framework.