In most marine gastropods, the duration of the larval phase is a key feature, strongly influencing species distribution and persistence. Antarctic lineages, in agreement with Thorson's rule, generally show a short pelagic developmental phase (or lack it completely), with very few exceptions. Among them is the ascidian-feeding gastropod family Velutinidae, a quite understudied group. Based on a multilocus (COI, 16S, 28S and ITS2) dataset for 182 specimens collected in Antarctica and other regions worldwide, we investigated the actual Antarctic velutinid diversity, inferred their larval development, tested species genetic connectivity and produced a first phylogenetic framework of the family. We identified 15 Antarctic Molecular Operational Taxonomic Units (MOTUs), some of which represented undescribed species, which show two different types of larval shell, indicating different duration of the Pelagic Larval Phase (PLD). Antarctic velutinids stand as an independent lineage, sister to the rest of the family, with extensive hidden diversity likely produced by rapid radiation. Our phylogenetic framework indicates that this Antarctic flock underwent repeated events of pelagic phase shortening, in agreement with Thorson's rule, yielding species with restricted geographic ranges.

ATIMO VATAE, BIOPAPUA, CEAMARC-AA, PANGLAO 2004, REVOLTA V

The systematics of several Eastern Atlantic conoidean species, traditionally ascribed to the genus Raphitoma Bellardi, 1847, are revised on the basis of DNA sequence data from three gene regions (cytochrome c oxidase subunit I, 16S rRNA and 12S rRNA). We assign genus ranking to three major lineages (Raphitoma, Cyrillia Kobelt, 1905 and Leufroyia Monterosato, 1884) and suggest that two West African species belong in the subgenus Daphnella (Paradaphne) Laseron, 1954. A new classification, based on molecular systematics and critical study of morphology, is provided for all Eastern Atlantic and Mediterranean species that are currently ascribed to Raphitoma s.l. The genus Clathromangelia Monterosato, 1884 is confirmed as belonging to Raphitomidae. Phylogenetic relationships and genetic distances suggest that Raphitoma maculosa Høisæter, 2016 and R. obesa Høisæter, 2016 may be divergent morphotypes of R. bicolor (Risso, 1826) and Cyrillia aequalis (Jeffreys, 1867), respectively.

AURORA 2007, BOA1, EBISCO, PANGLAO 2004, PAPUA NIUGINI, SALOMON 2, SANTO 2006

The systematics of several Eastern Atlantic conoidean species, traditionally ascribed to the genus Raphitoma Bellardi, 1847, are revised on the basis of DNA sequence data from three gene regions (cytochrome c oxidase subunit I, 16S rRNA and 12S rRNA). We assign genus ranking to three major lineages (Raphitoma, Cyrillia Kobelt, 1905 and Leufroyia Monterosato, 1884) and suggest that two West African species belong in the subgenus Daphnella (Paradaphne) Laseron, 1954. A new classification, based on molecular systematics and critical study of morphology, is provided for all Eastern Atlantic and Mediterranean species that are currently ascribed to Raphitoma s.l. The genus Clathromangelia Monterosato, 1884 is confirmed as belonging to Raphitomidae. Phylogenetic relationships and genetic distances suggest that Raphitoma maculosa Høisæter, 2016 and R. obesa Høisæter, 2016 may be divergent morphotypes of R. bicolor (Risso, 1826) and Cyrillia aequalis (Jeffreys, 1867), respectively.

AURORA 2007, BOA1, EBISCO, PANGLAO 2004, PAPUA NIUGINI, SALOMON 2, SANTO 2006

Profundiconus is the most divergent cone snail genus and its unique phylogenetic position, sister to the rest of the family Conidae, makes it a key taxon for examining venom evolution and diversity. Venom gland and foot transcriptomes of Profundiconus cf. vaubani and Profundiconus neocaledonicus were de novo assembled, annotated, and analyzed for differential expression. One hundred and thirty-seven venom components were identified from P. cf. vaubani and 82 from P. neocaledonicus, with only four shared by both species. The majority of the transcript diversity was composed of putative peptides, including conotoxins, profunditoxins, turripeptides, insulin, and prohormone-4. However, there were also a significant percentage of other putative venom components such as chymotrypsin and L-rhamnose-binding lectin. The large majority of conotoxins appeared to be from new gene superfamilies, three of which are highly different from previously reported venom peptide toxins. Their low conotoxin diversity and the type of insulin found suggested that these species, for which no ecological information are available, have a worm or molluscan diet associated with a narrow dietary breadth. Our results indicate that Profundiconus venom is highly distinct from that of other cone snails, and therefore important for examining venom evolution in the Conidae family.

KANACONO

Species in the family Capulidae (Littorinimorpha: Capuloidea) display a wide range of shell morphologies. Several species are known to live in association with other benthic invertebrates—mostly bivalves and sabellid worms, but also other gastropods—and are believed to be kleptoparasitic filter feeders that take advantage of the water current produced by the host. This peculiar trophic ecology, implying a sedentary lifestyle, has resulted in highly convergent shell forms. This is particularly true for the genus Hyalorisia Dall, 1889, which occurs in deep water in the Caribbean and Indo-West Pacific provinces, with two nominal species recognized so far. Combining morphological, ecological and molecular data, we assessed the diversity of the genus, its phylogenetic position inside the family and its association with its bivalve host, the genus Propeamussium de Gregorio, 1884 (Pectinoidea), resulting in the description of nine new cryptic species. When sympatric, species of Hyalorisia are associated with different host species, but the same species of Propeamussium may be the host of several allopatric species of Hyalorisia.

AURORA 2007, CONCALIS, CORSICABENTHOS 1, EBISCO, KANACONO, KANADEEP, KARUBENTHOS 2, KAVIENG 2014, KOUMAC 2.3, MADEEP, MAINBAZA, MIRIKY, NanHai 2014, PANGLAO 2004, PANGLAO 2005, SALOMON 2, ZhongSha 2015

A coiled shell is the most evident feature of the typical Bauplan of a gastropod mollusc. However, at least 54 families independently evolved an apparently simplified shell morphology: the limpet. Species with this largely uncoiled, depressed shell morphology occur in almost every aquatic habitat and are associated to a number of different lifestyles and diets. The marine gastropod family Capulidae includes 18 recognised genera, the large majority of which are coiled, but with a number of limpet-like species. Capulid shell plasticity is also associated to a broad range of feeding ecologies, from obligate suspension feeders to kleptoparasites.

KARUBENTHOS 2, KOUMAC 2.3, PANGLAO 2004

A remarkably high diversity of native small spindle-shells (Gastropoda, Fasciolariidae, Fusininae) has been recently inventoried in the Mediterranean Sea, with 23 species identified based on shell morphology. They have almost invariably been classified in the genus Fusinus, and a few of them recently moved to other genera (Aptyxis Troschel 1868, Aegeofusinus Russo, 2017 and Gracilipurpura Jousseaume, 1880), mostly based on the sole shell features. We have reconstructed a molecular phylogenetic framework for the Mediterranean Fusininae, focusing on native species representative of the genus-level taxa. Our results confirmed that Fusinus s.s. (type species Murex colus Linnaeus, 1758) should be restricted to a group of large-shelled species from the Indo-West Pacific and does not fit any of the small-shelled Mediterranean fusinines. We confirm that Murex syracusanus Linnaeus, 1758 represents a distinct lineage, and show that for all the remaining species the pattern is suggestive of a single monophyletic radiation of small Mediterranean fusinines, for which the name Pseudofusus Monterosato, 1884 must be used

ATIMO VATAE, AURORA 2007, CONCALIS, Restreint, EBISCO, EXBODI, GUYANE 2014, KANACONO, KARUBENTHOS 2, KARUBENTHOS 2012, KAVIENG 2014, MIRIKY, NanHai 2014, PAKAIHI I TE MOANA, PANGLAO 2004, PANGLAO 2005, PAPUA NIUGINI, SALOMON 2, SALOMONBOA 3, SANTO 2006, TARASOC, TERRASSES, Restreint

Abstract The systematics of the marine mollusc family Velutinidae has long been neglected by taxonomists, mainly because their often internal and fragile shells offer no morphological characters. Velutinids are usually undersampled owing to their cryptic mantle coloration on the solitary, social or colonial ascidians on which they feed and lay eggs. In this study, we address the worldwide diversity and phylogeny of Velutinidae based on the largest molecular dataset (313 specimens) to date, accounting for > 50% of the currently accepted genera, coupled with morphological and ecological data. Velutinids emerge as a diverse group, encompassing four independent subfamily-level lineages, two of which are newly described herein: Marseniopsinae subfam. nov. and Hainotinae subfam. nov. High diversity was found at genus and species levels, with two newly described genera (Variolipallium gen. nov. and Pacifica gen. nov.) and ≥ 86 species in the assayed dataset, 58 of which are new to science (67%). Velutinidae show a remarkable morphological plasticity in shell morphology, mantle extension and chromatic patterns. This variability is likely to be the result of different selective forces, including habitat, depth and trophic interactions.

ATIMO VATAE, BIOMAGLO, BIOPAPUA, CEAMARC-AA, CORSICABENTHOS 1, CORSICABENTHOS 2, CORSICABENTHOS 3, GUYANE 2014, ILES DU SALUT, KANACONO, KANADEEP 2, KARUBENTHOS 2, KAVIENG 2014, KOUMAC 2.1, KOUMAC 2.3, MADEEP, MADIBENTHOS, PANGLAO 2004, PAPUA NIUGINI, SAKIZAYA 2019, SANTO 2006, Tuhaa Pae 2013, ZhongSha 2015

Background:  Planaxis sulcatus has been touted as a textbook example of poecilogony, with members of this wideranging 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. Results:  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. Conclusions:  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.

ATIMO VATAE, INHACA 2011, KAVIENG 2014, KOUMAC 2.1, SANTO 2006

Among gastropods, the ability to swim has developed independently several times, mostly among Heterobranchia. Only a few species of Caenogastropoda are known to have swimming adults. Velutinidae Gray, 1840, is a family of caenogastropods with a fragile shell enclosed by the mantle. The adults of this family are benthic and ectoparasites of ascidians. Here, we present the first recorded instance of a swimming velutinid, Marsenia cf. gemma, filmed in New Caledonia. The swim propulsion method was based on the movement of the snail’s foot, which followed a ∞-shaped curve. This first report changes our perspective on the biology of this family, unexpectedly placing it within the restricted group of swimming caenogastropods.

ATIMO VATAE, KOUMAC 2.1, KOUMAC 2.3, MADIBENTHOS, PANGLAO 2004, PAPUA NIUGINI

KARUBENTHOS 2, KOUMAC 2.3, PANGLAO 2004

The four recent species of the genus Leufroyia Monterosato, 1884 are revised based on an integrative taxonomy approach: L. leufroyi (Michaud, 1828), L. concinna (Scacchi, 1836), L. erronea Monterosato, 1884 and L. villaria (Pusateri & Giannuzzi-Savelli, 2008).

CORSICABENTHOS 1

Predator-prey interactions are thought to play a driving role in animal evolution, especially for groups that have developed venom as their predatory strategy. However, how the diet of venomous animals influences the composition of venom arsenals remains uncertain. Two prevailing hypotheses to explain the relationship between diet and venom composition focus on prey preference and the types of compounds in venom, and a positive correlation between dietary breadth and the number of compounds in venom. Here, we examined venom complexity, phylogenetic relationship, collection depth, and biogeography of the Terebridae (auger snails) to determine if repeated innovations in terebrid foregut anatomy and venom composition correspond to diet variation. We performed the first molecular study of the diet of terebrid marine snails by metabarcoding the gut content of 71 terebrid specimens from 17 species. Our results suggest that the presence or absence of a venom gland is strongly correlated with dietary breadth. Specifically, terebrid species without a venom gland displayed greater diversity in their diet. Additionally, we propose a revision of the definition of venom complexity in conoidean snails to more accurately capture the breadth of ecological influences. These findings suggest that prey diet is an important factor in terebrid venom evolution and diversification and further investigations of other understudied organisms, like terebrids, are needed to develop robust hypotheses in this area.

PAPUA NIUGINI

In this study, we delved into the interaction between corallivorous marine gastropods, the muricid Coralliophilinae Chenu, 1859, and their cnidarian food targets. Coralliophilinae is a subfamily of specialised corallivorous caenogastropods that feed by browsing on octocorals or hexacorals. Only sparse information is available on the phylogenetic relationships and the degree of specificity of the trophic relationships within this corallivorous lineage. To address these gaps, we generated the largest molecular dataset to date, comprising two mitochondrial (cox1 and 16S rDNA) and one nuclear gene (ITS2 rDNA) from 586 specimens collected worldwide. The coral hosts of coralliophilines were identified through an integrative approach, combining literature data with new records, employing morphological and/or molecular markers, and incorporating data from DNA barcoding of the snail stomach content. Our comprehensive approach unveiled the existence of numerous cryptic species in Coralliophilinae, while the phylogeny showed that most of the currently accepted genera are not monophyletic. The molecular dating confirmed the origin of the Coralliophilinae in Middle Eocene, with diversification of most lineages during the Miocene. Our results indicate that the subfamily’s ancestor evolved in shallow waters in association with Scleractinia. Through the evolutionary history of Coralliophilinae, multiple host shifts to other cnidarian orders were observed, not correlated with changes in the depth range. The results of diversification analyses within the subfamily further suggest that the association with the host has influenced the evolutionary patterns of Coralliophilinae, but not vice versa.

ATIMO VATAE, BIOMAGLO, CONCALIS, CORSICABENTHOS 2, CORSICABENTHOS 3, EBISCO, EXBODI, GUYANE 2014, INHACA 2011, KARUBENTHOS 2, KAVIENG 2014, LIFOU 2000, MADIBENTHOS, MAINBAZA, MIRIKY, NORFOLK 2, NanHai 2014, PAKAIHI I TE MOANA, PANGLAO 2004, PANGLAO 2005, PAPUA NIUGINI, SANTO 2006, TARASOC, TERRASSES, Tuhaa Pae 2013, Walters Shoal, ZhongSha 2015

Introduction Host-parasite associations provide very useful models to study adaptive processes. We investigated the interaction between carnivorous marine gastropods, the Ovulidae or egg-cowries, and their cnidarian food targets. Ovulidae (Fleming, 1828), is a family of specialized carnivorous caenogastropods that feed by browsing on octocorals (Anthozoa: Octocorallia: Malacalcyonacea and Scleralcyonacea) or, to a much lesser degree, on antipatharians (Anthozoa: Hexacorallia: Antipatharia) and Stylasteridae (Hydrozoa: Hydroidolina: Anthoathecata). Very scanty information is available on the phylogenetic relationships and the degree of specificity of the relationship with the cnidarians of this corallivorous lineage, especially for deep-water taxa. Methods To assess taxonomic identifications and investigate cnidarian/ovulid relationships in the context of their evolution, we generated an extensive molecular dataset comprising two mitochondrial ( cox1 and 16S rDNA ) and one nuclear gene ( 28S rDNA ) from 524 specimens collected worldwide. The coral hosts of the ovulid species have been identified by integrating literature data with new records, employing morphological and/or molecular (the mitochondrial 16S rDNA and mtMSH , and the nuclear ITS2) markers. Results We obtained a molecular phylogenetic framework for the Ovulidae, time-calibrated with nine reliable fossil records. An ancestral state reconstruction allowed to identify Hexacorallia or Hydroidolina as the most likely ancestral cnidarian host for the Ovulidae. Discussion Our phylogenetic hypothesis revealed the existence of groups that do not completely correspond to the currently employed subfamilial arrangement. Concerning trophic ecology, while only pediculariines ( Pedicularia and allied) are associated with hydrozoans (Stylasteridae), our results suggest that some ovulid lineages shifted independently between octocorals and hexacorals.

ATIMO VATAE, AURORA 2007, BIOMAGLO, CORSICABENTHOS 1, CORSICABENTHOS 2, CORSICABENTHOS 3, EBISCO, EXBODI, KANACONO, KANADEEP, KARUBENTHOS 2, KAVIENG 2014, KOUMAC 2.3, MADEEP, MADIBENTHOS, MAINBAZA, MIRIKY, NORFOLK 2, NanHai 2014, PAKAIHI I TE MOANA, PANGLAO 2004, PAPUA NIUGINI, SALOMONBOA 3, SANTO 2006, SPANBIOS, ZhongSha 2015

The worldwide distributed neogastropod family Muricidae comprises more than 1800 extant species of whelks, rock-shells, murex-shells, drill-shells, and coral-shells. Despite several attempts at a taxonomic revision based on morphological characters, the systematics of this family is still largely debated. Here, we present a molecular revision of the family Muricidae based on the largest dataset analysed so far, which comprises 384 specimens representing 360 species and includes, for the first time, all the currently recognised subfamilies. A molecular dataset of cox1, 12S rRNA, 16S rRNA, and 28S rRNA genetic markers and six fossil-based calibration points were used to produce time-calibrated phylogenetic reconstructions, using a Maximum Likelihood approach. Our results confirmed the monophyly of most of the accepted subfamilies, suggested a revision of the taxonomic composition of Muricopsinae and Muricinae, and highlighted some lineages not immediately comprised in any of the recognised subfamilies. The origin and early diversification of the subfamilies of Muricidae occurred between 32 and 60 million years ago.

ATIMO VATAE, AURORA 2007, BIOPAPUA, CONCALIS, EBISCO, GUYANE 2014, KARUBENTHOS 2012, MAINBAZA, MIRIKY, NORFOLK 1, NORFOLK 2, PANGLAO 2004, PANGLAO 2005, PAPUA NIUGINI, SALOMON 2, SANTO 2006, TERRASSES