Radular Morphology Research Articles

Pseudolatirus Bellardi, 1884 revisited, with the description of two new genera and five new species (Neogastropoda: Fasciolariidae)

The genus Pseudolatirus Bellardi, 1884, with the Miocene type species Fusus bilineatus Hörnes, 1853, has been used for 13 Miocene to Early Pleistocene fossil species and eight Recent species and has traditionally been placed in the fasciolariid subfamily Peristerniinae Tryon, 1880. Although the fossil species are apparently peristerniines, the Recent species were in their majority suspected to be most closely related to Granulifusus Kuroda & Habe, 1954 in the subfamily Fusininae Wrigley, 1927. Their close affinity was confirmed by the molecular phylogenetic analysis of Couto et al. (2016). In the molecular phylogenetic section we present a more detailed analysis of the relationships of 10 Recent Pseudolatirus-like species, erect two new fusinine genera, Okutanius gen. nov. (type species Fusolatirus kuroseanus Okutani, 1975) and Vermeijius gen. nov. (type species Pseudolatirus pallidus Kuroda & Habe, 1961). Five species are described as new for science, three of them are based on sequenced specimens (Granulifusus annae sp. nov., G. norfolkensis sp. nov., Okutanius ellenae gen. et sp. nov.) and two (G. tatianae sp. nov., G. guidoi sp. nov.) are attributed to Granulifusus on the basis of conchological similarities to sequenced species. New data on radular morphology is presented for examined species.

Identification of new species of Kalloconus and Africonus (Gastropoda, Conidae) from the Cabo Verde Islands through mitochondrial genome comparison

The new species Kalloconus marimaris sp. nov. and Africonus angeluquei sp. nov. are described from the material obtained during the MNCN sampling campaigns at the Cabo Verde Islands. The new species have been characterized by examination of their shell and radular teeth morphology and by the comparison of mitochondrial genomes obtained through next-generation DNA sequencing techniques. Phylogenetic analyses suggest that K. marimaris sp. nov., known from Sal Island, is a sister species to Kalloconus ateralbus, whereas A. angeluquei sp. nov. from Maio Island is a sister species to Africonus josephinae and Africonus borgesi from Boa Vista Island. The estimated genetic distances were consistent with the full species rank for the new taxa described herein.

Integrative systematics of Placida cremoniana (Trinchese, 1892) (Gastropoda, Heterobranchia, Sacoglossa) reveals multiple pseudocryptic species

Placida cremoniana (Trinchese, 1892) is a sacoglossan heterobranch sea slug of striking coloration, with a reported range that has increased dramatically in recent years. Described from the Mediterranean in 1892, nominal conspecifics were reported from Japan in 1959, and since the 1990s, additional populations have been reported from across the tropical Atlantic, Pacific, and Indian oceans, plus temperate areas of Japan, Australia, and Europe. This sequence of events is consistent with a dramatic range expansion by one species due to human-mediated introductions, or dispersal from tropical into temperate areas induced by recent climate change. Alternatively, the expanding range of this nominal species could, instead, reflect the gradual discovery of previously unsampled members of a global species complex. These hypotheses were tested using a combination of molecular data from three loci (COI, 16S, and H3), as well as radular morphology and external color patterns, from specimens sampled from most of the reported range. Molecular species delimitation recovered P. cremoniana as a complex of four genetically divergent species, further distinguished by consistent differences in head coloration and radular morphology. As the Mediterranean species retains the name P. cremoniana, the three new species are described here, including an Eastern Pacific endemic and two species that are sympatric across large areas of the Central and Western Pacific. Photographic records and literature reports suggest that additional species may occur in the Indian Ocean, tropical Australia, and Caribbean.

Living with a giant parchment tube worm: a description of a new nudibranch species (Gastropoda: Heterobranchia) associated with the annelid Chaetopterus

Small fionid nudibranch specimens collected within a Chaetopterus sp. tube worm are described here as a new species Tenellia chaetopterana sp. nov. This case is the first example of symbiotic association between a mollusk and an annelid host amongst cladobranch sea slugs. The external morphology of this species suggests it is adapted for living inside the worm’s tube: flattened body, laterally directed cerata and rhinophores, and wide foot. Molecular data, including partial sequences of mitochondrial COI and 16S and nuclear H3 genes, indicates that this species is distinct from other members of the genus Tenellia as well as other fionids. The species is close to the coral-feeding fionids of the genus Tenellia (formerly in genus Phestilla) in several morphological characters such as general radula morphology, absence of cnidosacs, and flattened body shape, as well as by molecular data. Tenellia chaetopterana sp. nov. has unique biology, implicating possible diversity previously overlooked by nudibranch faunistic studies.

A new species of the genus Phymorhynchus (Neogastropoda: Raphitomidae) from a hydrothermal vent in the Manus Back-Arc Basin

During an investigation carried out by the Institute of Oceanology, Chinese Academy of Sciences (IOCAS), three living raphitomid specimens were collected from a hydrothermal vent site in the Manus Back-Arc Basin. Observations of the shell, external anatomy and radular morphology reveal that they represent an undescribed species of the genus Phymorhynchus Dall, 1908. In this paper, we describe and illustrate this species as Phymorhynchus oculatus sp. nov. The new species is most similar in general shell shape to Phymorhynchus buccinoides Okutani, Fujikura & Sasaki, 1993, but can be distinguished from it by having spiral cords over the whole shell surface and much longer marginal tooth with a distal barb. A list of species of Phymorhynchus from vent/seep habitats is also given.

Molecular analysis reveals a new cryptic species in a limpet Lottia kogamogai (Patellogastropoda: Lottiidae) from Japan.

A group of small lottiid species in Japan, the Lottia kogamogai complex, was phylogenetically analyzed based on the mitochondrial COI gene. As a result, L. kogamogai is subdivided into two geographic clades. Lottia kogamogai s.s. is limited to southern temperate Japan. The northern population formerly considered an intraspecific variation of the species is shown to be a distinct new species, here described as Lottia goshimai n. sp. The new species is distinguishable from L. kogamogai not only genetically, but in radular morphology and shell sculpture.

Diferencias morfométricas de dos especies del género Eatoniella en Isla Navarino, Reserva de Biosfera Cabo de Hornos, Chile

The external morphometrics of shell and radula morphology were performed in two species of micromollusks of the genus Eatoniella in Navarino Island, Chile. A total of 50 specimens of E. picea and 72 of E. nigra were analyzed. These species have similar morphology, but E. picea has a smaller diameter/length ratio (0.53 ± 0.02) than E. nigra (0.61 ± 0.04). In relation to the radula morphology, E. picea has wider middle cuspid teeth and small denticles in its border, meanwhile E. nigra has pointed central cuspid teeth.

A taxonomic position of Armenian endemic freshwater snails of the genus Shadinia Akramowski, 1976 (Caenogastropoda: Hydrobiidae): combining morphological and molecular evidence

ABSTRACTAccording to analyses of anatomical data and nucleotide sequences of three genes (16S, 18S rDNA and CO 1 mtDNA), the Armenian endemic genus Shadinia Akramowski, 1976 should be considered as a separate subfamily, Shadiniinae of Hydrobiidae Stimpson, 1865. A combination of genetic resemblance and similarity in conchology, morphology of radula, male and female anatomy (except some details) assures us of the close relationship of Shadinia and the genera Persipyrgula and Intermaria recently described from riverine waters of Iran. We provisionally assign these two genera to the new subfamily, which also includes the genus Nicolaia, established in 2015 for small hydrobiids from the Kasach River (Armenia). The latter genus has not yet been studied genetically, but morphological evidence leads us to consider it as compatible with Persipyrgula and Intermaria. All three genera differ significantly from the genus Shadinia in only one respect: females of these snails have one seminal receptacle, while those of Shadinia have two. The subfamily Shadiniinae is a sister group to Pyrgulinae; the former differs morphologically from the latter in possessing a pigmented nervous system and odontophore, presence of basal cusps on the central tooth of the radula and a black pigmented coiled oviduct without the widening that characterises most of the Pyrgulinae.http://zoobank.org/urn:lsid:zoobank.org:pub:3009CB4E-EE5B-44BE-B8E4-497B5CB3BE5D

Not all spotted cats are leopards: evidence for a Hemilienardia ocellata species complex (Gastropoda: Conoidea: Raphitomidae)

The small conoidean Hemilienardia ocellata is one of the easily recognizable Indo-Pacific “turrids”, primarily because of its remarkable eyespot colour pattern. Morphological and molecular phylogenetic analyses revealed four species that share this “characteristic” colour pattern but demonstrate consistent differences in size and shell proportions. Three new species – Hemilienardia acinonyx sp. nov. from the Philippines, H. lynx sp. nov. from Papua New Guinea and H. pardus sp. nov. from the Society and Loyalty Islands – are described based on the results of phylogenetic analyses. Although the H. ocellata species complex clade falls in a monophyletic Hemilienardia, H. ocellata and H. acinonyx sp. nov. possess a radula with semi-enrolled or notably flattened triangular marginal teeth, a condition that diverges substantially from the standard radular morphology of Hemilienardia and other raphitomids.

An integrative taxonomic approach to infer the systematic position of Chalepotaxis Ancey, 1887 (Gastropoda: Stylommatophora: Helicarionidae)

ABSTRACTIn the absence of knowledge about its anatomy, the systematic position of the genus Chalepotaxis, which inhabits a large part of South East Asia, has been historically dubious. The genitalia, sole of the foot and the caudal region of the type species, Chalepotaxis infantilis (Gredler, V. 1881. Zur Conchylien-Fauna von China. III. Stück. Jahrbücher der Deutschen Malakozoologischen Gesellschaft 8, 110–128), are described, which place this genus into the Helicarionidae family. DNA markers (cytochrome oxidase subunit I [COI] and 28S rRNA genes) corroborate this assignment and unequivocally remove the species from the Camaenidae (=Bradybaenidae) and Ariophantidae, where it had previously been placed. Radular morphology of the type species is also re-described and illustrated.

First record of nudibranch mollusk Onchidoris muricata (O. F. Müller, 1776) (Mollusca, Gastropoda, Heterobranchia) in the Sea of Japan and its ephemeral population associated with unusual prey

The nudibranch mollusk Onchidoris muricata known from boreal waters of the western Pacific, North American Pacific shore, and both coasts of the northern Atlantic was first recorded from the Sea of Japan (East Sea). This discovery extends its distribution range southwards along the Asian Pacific coast from cool temperate waters of Kamchatka and Kommander’s Islands to cool temperate sub-zone of the Sea of Japan. Three discovered populations in the northern Sea of Japan are confirmed to be conspecific with other Pacific and Atlantic populations of O. muricata because of external and radular morphology along with low interpopulation genetic variation (<3 %) found between studied COI gene sequences, while intraspecific distances between Onchidoris species range from 12.9 to 19.7 %. One of the discovered population constitutes an ephemeral settlement and is associated with the bryzoan Microporina articulata, an unusual prey for the Onchidorididae. Despite observing reproducing O. muricata adult individuals sheltered in M. articulata colonies, the nudibranch population remains unstable and became extinct within one season; however, it can be resurrected due to larvae migration from adjacent waters using ecological plasticity of this species as intrinsic resource for distribution area extension.

Molecular and morphological systematics of Elysia Risso, 1818(Heterobranchia: Sacoglossa) from the Caribbean region.

The Caribbean is a biodiversity hotspot for photosynthetic sea slugs, with about 27 described species in the genus Elysia Risso, 1818. However, many species are poorly known or have complex taxonomic histories, complicating assessments of regional biodiversity and impeding studies of plastid symbiosis, speciation, and larval biology. Using an integrative approach, we address the taxonomy and systematics of Caribbean elysiids by performing robust tests of existing species hypotheses, and describe six new species. Species delimitation included DNA barcoding of up to 189 nominal conspecific specimens; nuclear gene sequences were then used to confirm that divergent lineages were genetically distinct candidate species. New synonymies and species descriptions are based on external anatomy, penial and radular morphology, developmental characters, and host ecology of all species described from the region, plus a critical review of the literature. We synonymized three species (Elysia annedupontae Ortea, Espinosa & Caballer in Ortea, Caballer, Moro & Espinosa, 2005, Elysia clarki Pierce et al. 2006, and Elysia leeanneae Caballer, Ortea & Espinosa in Ortea, Espinosa, Buske & Caballer, 2013), transfered one species from Bosellia (Elysia marcusi), and described six new species (Elysia pawliki n. sp., Elysia zemi n. sp., Elysia christinae n. sp., Elysia hamanni n. sp., Elysia taino n. sp., and Elysia buonoi n. sp.). We resurrected the name Elysia velutinus Pruvot-Fol, 1947, a senior synonym of Elysia tuca Ev. Marcus & Er. Marcus, 1967. Based on a four-gene phylogeny of 76 Elysia spp., we identified shifts in host use and penial armature that may explain patterns of endemic diversification in Elysia, invoking both ecological and non-ecological mechanisms. Non-monophyly of stylet-bearing species rejects previous attempts to classify species based on presence of a stylet (i.e., the genus Checholysia Ortea, Caballer, Moro & Espinosa, 2005). Our findings show how integrative approaches can resolve the taxonomic status of problematic species (e.g., Elysia papillosa Verrill, 1901) for soft-bodied marine taxa.

Radular morphology of Zidona dufresnei (Neogastropoda: Volutidae) and an analysis of its variability along the distributional range

ABSTRACTThe radular morphology of Zidona dufresnei was studied by optical and scanning electron microscopy. We analysed the variability among and within three populations distributed along the southwestern Atlantic Ocean coast, considering the hypothesis that the isolation among populations favours adaptive phenotypic variation, which is also expressed at the radular level. Populations selected for this study differ in their maximum individual size, growth rate, size and age at maturity, and fecundity. This study provides the first analysis of the interpopulational variability of the radula of Zidona dufresnei and the first description of its morphology. Zidonia dufresnei exhibited a rachiglossate radulae composed of rows of tricuspid teeth (radular formula: 0+R+0). No differences in tooth shape among populations and sexes were observed. However, significant interpopulational differences in the height of the rachidian cusp and total length of the radula were detected. Specimens from San Antonio Bay showed the lowest values for all radular variables. Positive significant relationships between total shell length and the height of the rachidian cusp and total length of the radula were found, while the number of rows remained relatively constant regardless of size. The larger morphotypes had a longer radula because of an increase in the height of the rachidian cusp. No sexual dimorphism was observed in any morphometric variables of the radula. The results suggest that populations distributed along the Argentine Sea are homogeneous for radular morphology, despite the differences in life history traits, which may be linked to a similarity in feeding habits across populations.

Radular Morphology of Extinct Pleurocerids (Gastropoda: Cerithioidea: Pleuroceridae)

Abstract: The freshwater gastropod family Pleuroceridae suffers from a disproportionately high number of imperiled species and recent extinctions. As pleurocerid diversity has been lost, so too has our ability to study the biology of these animals. However, many extinct species were deposited in natural history collections before their demise. I extracted radulae from dried tissue left in shells of seven extinct species in three genera (Leptoxis Rafinesque, 1819, Gyrotoma Shuttleworth, 1845, Lithasia Haldeman, 1840) to gain insights into the morphological differences separating species and provide data for future researchers. There were notable intergeneric and interspecific differences in radular morphology such as shape of cusps (e.g., dagger-like vs. blunt) and number of denticles on the rachidian, lateral, and marginal teeth. Interestingly, the degree of radular differences among Leptoxis spp. likely corroborates previous hypotheses that the genus is not a natural group. These data are a resource for ...

Janolus fuscus O’Donoghue, 1924 (Gastropoda: Proctonotidae), a species of a nudibranch family that is new to the marine fauna of Russia

The seaslug Janolus fuscus of the family Proctonotidae, which is new to the Russian fauna, was found in the Sea of Japan for the first time. A small population of this mollusk was found at the northwestern coast on a bank occupying approximately 3000 m2 of the sea bottom south of Rudnaya Bay. Data on the distribution, ecology, radula morphology, and feeding of this mollusk on the bryozoan Microporina articulata are presented. The differences between J. fuscus and similar species of the genus Janolus are discussed. The partial sequences (614 bp) of the mitochondrial COI gene differed in two nucleotide substitutions, suggesting that the population that is found in the Sea of Japan is conspecific to the North American J. fuscus.

Functional morphology of the buccal complex of Flabellina verrucosa (Gastropoda: Opisthobranchia)

Buccal complex of Gastropoda is a complex structure consisting of the radula, odontophore and the buccal muscles. The general morphology and function of the buccal complex of Gastropoda was well-studied in several aspects. However, there are only a few integrated studies on both general and fine morphology, and the mechanism of feeding performed on opisthobranchs. Opisthobranchs' feeding mechanisms are very specific and diverse, because opisthobranch molluscs have highly-specified feeding preferences. Un- like the majority of opisthobranchs, Flabellina verrucosa (Gastropoda: Opisthobranchia) has a wide range of feeding objects. The feeding mechanism of this species can be an example of the non-specified feeding mode. General and fine morphology of the buccal complex of F. verrucosa is studied in the present work. Based on three-dimensional reconstruction of the buccal complex and data on the fine morphology of muscles, we suggest the mechanism of the functioning of the food-obtaining apparatus. Prey is pulled into the buccal cavity due to blowing negative pressure and triturated using the radula. This feeding mechanism is suggested for Gastropoda for the first time and could be compared only with that in Tochuina tetraquetra and Dendronotus iris (Nudibranchia: Dendronoti- da), although the morphology of radula in these three species differs considerably. How to cite this article: Mikhlina A.L., Vortsepneva E.V., Tzetlin A.B. 2015. Functional morphology of the buccal complex of Flabellina verrucosa (Gastropoda: Opisthobran- chia) // Invert. Zool. Vol.12. No.2. P.175-196. doi: 10.15298/invertzool.12.2.04

Taxonomic Revision of the Anatomidae (Mollusca: Gastropoda: Vetigastropoda) from Brazil, with Description of Four New Species

ABSTRACT A taxonomic revision of the family Anatomidae from Brazil led to the discovery of nine species, four of which are new. This contrasts with only two species previously recorded: Anatoma aedonia (Watson, 1886) and Anatoma proxima (Dall, 1927). The lectotype designation for A. aedonia by Geiger (2012) has clarified the identity of this taxon, which is now considered a rare species, mainly from deep waters. The holotype of A. proxima is lost (Geiger, 2012), and some very similar taxa occur sympatrically in the western Atlantic; accordingly, we designate here a neotype for Scissurella proxima and redescribe it, re-evaluating its shell variability and radula morphology. The review of a large amount of shells in malacological collections in Brazil, including material from recent dredging along the southeastern coast, revealed the occurrence of seven additional species: Anatoma americana Bandel, 1998, synonymized under A. proxima by Geiger (2012), is herein considered a valid species; Anatoma atlantica (...

Two new species of Ovassiminea Thiele, 1927 (Truncatelloidea: Assimineidae) from tropical Australia

This study reports Ovassiminea Thiele, 1927 (Truncatelloidea: Assimineidae) for the first time in Australia, and two new species, Ovassiminea annulata n. sp., and Ovassiminea miskellyi n. sp., are described. They share a combination of morphological characters similar to the genus type species Ovassiminea dohrniana (Nevill, 1880), such as radular and shell morphology, configuration of the glandular oviduct, and a distinctly undulating anterior vas deferens, the latter a possible autapomorphy for the genus. Maximum Likelihood and Bayesian Inference analyses of a COI mitochondrial fragment (625 bp) suggest evolutionary affinities of the two Australian taxa to the Australian genus Cryptassiminea Fukuda & Ponder, 2005 and Assiminea grayana Fleming, 1828. Of the two new species, O. annulata possesses stronger spiral sculpture, a more pronounced internal protuberance on the operculum, and three pairs of basal cusps on the radula as opposed to two in O. miskellyi. Both species share a long penial papilla that is absent in O. dohrniana. The two species are not sympatric, with O. annulata occurring from the western Gulf of Carpentaria to Darwin, Northern Territory, and with O. miskellyi known from northern Kimberley and the Preston Peninsula, Pilbara, Western Australia.Ovassiminea annulata http://zoobank.org/urn:lsid:zoobank.org:act:256B4E59-076B-4B5B-A93F-14F0DB3CD6F2Ovassiminea miskellyi http://zoobank.org/urn:lsid:zoobank.org:act:C997758A-BE45-4B71-BE27-4565D7F391DE

Morphology, molecules and taxonomy: extreme incongruence in pleurocerids (Gastropoda, Cerithioidea, Pleuroceridae)

Pronounced mitochondrial heterogeneity within putative species of Pleuroceridae has prevented meaningful systematic revisions of this critically imperilled freshwater family. Previous studies have demonstrated that this mitochondrial diversity often produces polyphyletic species on mitochondrial gene trees, but its significance is unclear. Hypotheses advanced to explain this pattern have included cryptic species, retained ancestral polymorphisms and introgression; other possible explanations such as doubly uniparental inheritance or the presence of pseudogenes have not been given due consideration. Previous analyses have not included adequate sampling, neither in terms of number of individuals nor in geographic coverage, to adequately test any of these hypotheses. To fully characterize mitochondrial heterogeneity in pleurocerids and robustly assess possible causal explanations, we collected 239 individuals representing four putative species from seven sites and sequenced the COI and 16S rRNA mitochondrial genes and the H3 nuclear gene for all individuals. We also used whole‐genome shotgun sequencing to construct and annotate a mitochondrial genome for one individual. Characters with demonstrated utility in morphospecies delineation of gastropods (head–foot coloration, shell and radular morphology, pallial oviduct anatomy) were examined for a subset of individuals to determine whether morphology co‐varied by haplotype clade. We found pronounced mitochondrial heterogeneity at both the population level and species level in three of the species examined, but our data reject paralogous nuclear copies of mitochondrial genes (NUMTs) and doubly uniparental inheritance as causal mechanisms, and there was no evidence of cryptic diversity. Mutation rates were found to differ significantly among mitochondrial lineages, and population genetic statistics revealed a signature of balancing selection that could be acting to maintain this diversity. The observed pattern is similar to that seen in lineages with inherited endosymbionts like Wolbachia infections, which merits further investigation. Although questions remain concerning the precise cause(s) of intraspecific mitochondrial diversity in pleurocerids, nuclear and/or genomic data, combined with anatomical and life history investigations in an integrative phylogenetic context, is the most promising avenue for resolving pleurocerid systematics.

First record and description of a new species of the land snail genus Pearsonia Kobelt, 1902 (Cyclophoridae: Pterocyclinae) from Thailand, with a note on radula morphology

First record and description of a new species of the land snail genus Pearsonia Kobelt, 1902 (Cyclophoridae: Pterocyclinae) from Thailand, with a note on radula morphology