The taxonomic status of the headshield slug genus Nakamigawaia Kuroda and Habe, 1961 (Gastropoda: Cephalaspidea: Aglajidae), with the description of a new species from the Western Pacific

Nakamigawaia is a poorly understood genus of Aglajidae sea slugs with only two species formally ascribed. In this paper we explore new morpho-anatomical characters using stereo and scanning electron microscopy and employ different molecular approaches (a cytochrome c oxidase sub-unit I gene phylogeny, the Automatic Barcode Gap Discovery species delimitation method, and genetic distances) to compare specimens across the geographical span of the genus and from two distinct chromatic morphotypes occurring in the Western Pacific (blackish morph and white-dotted morph). Our results support the conspecificity of these two morphs and show they belong to an undescribed species here named Nakamigawaia nakanoae sp. nov. The species differs from the type species of the genus, N. spiralis, by the presence of a distinct open-dilated shell and differs from its Western Atlantic congener N. felis by subtle differences in the shell, male reproductive system and caudal lobes. Genetically (COI uncorrected p-distance) the two species (N. nakanoae and N. felis) are 18.8–20.1% distinct. The definition of the genus Nakamigawaia is discussed and the current assignment to the latter of lineages other than the type species is questioned.publishedVersio

Molecular phylogeny of the marine snail genus Haminoea (Gastropoda, Cephalaspidea): A framework to study marine diversity and speciation

Haminoea are herbivorous, coastal snails occurring in temperate and tropical waters of the Atlantic and Eastern Pacific oceans, with one species present in temperate South Africa (Indian Ocean). The genus is taxonomically difficult as several available nominal species were introduced based on shell descriptions alone, or described based on subtle differences in morpho-anatomical features, without a phylogenetic molecular framework. Fifteen species are currently accepted as valid in recent scientific literature and field guides (eight Eastern Atlantic, one temperate Indian Ocean, four Western Atlantic and three Eastern Pacific). Here we generate the first complete phylogeny (Bayesian and Maximum Likelihood) of this genus based on multilocus molecular data (COI, 12S rRNA, 16S rRNA, 28S rRNA) using a taxon set accumulated over a period of 15 years, coupled with species delimitation analyses methods (ABGD, ASAP, bPTP) and morpho-anatomical studies. The goal of this study is to provide insights into the taxonomy, phylogenetic relationships and geographical distributions of species while generating a framework for future systematic reviews of the genus, as well as to study speciation and historical biogeography. Our results rendered four possible hypotheses of species diversity: with 14, 15, 19 and 20 candidate species and point to the fact that several taxa presently regarded as valid might be conspecific (e.g. H. orteai–H. templadoi–H. exigua; and H. alfredensis–H. antillarum–H. orbignyana), while highlighting the existence of a complex of four or five species often identified as H. elegans. Pervasive nomenclatural problems in the genus, including with the type species H. hydatis, are highlighted and discussed.publishedVersio

Molecular and morphological analyses reveal pseudocryptic diversity in Micromelo undatus (Brugui ere, 1792) (Gastropoda: Heterobranchia: Aplustridae)

The genus Micromelo (family Aplustridae) occurs in almost all tropical and subtropical waters across the globe, with the exception of the Eastern Pacific. Most authors consider Micromelo undatus (Bruguière, 1792) as the only valid species in this genus. This study examines populations of specimens identified as M. undatus across its geographic range, using morphological and genetic data from two mitochondrial genes (16S and CO1) and one nuclear gene (Histone H3). The results reveal that M. undatus is a complex of four species with consistent genetic and anatomical differences. A literature review and evaluation of type material indicates that available names exist for three of the four species. Micromelo guamensis, M. undatus and M. scriptus are resurrected for species found in the Western Pacific, the Atlantic Ocean, and widespread in the Indo-Pacific, respectively. A new name is introduced for another species found in the Western Pacific, namely Micromelo barbarae sp. nov. and a neotype is designated for the type species of the genus M. undatus.publishedVersio

Assessment of mitochondrial genomes for heterobranch gastropod phylogenetics

Background Heterobranchia is a diverse clade of marine, freshwater, and terrestrial gastropod molluscs. It includes such disparate taxa as nudibranchs, sea hares, bubble snails, pulmonate land snails and slugs, and a number of (mostly small-bodied) poorly known snails and slugs collectively referred to as the “lower heterobranchs”. Evolutionary relationships within Heterobranchia have been challenging to resolve and the group has been subject to frequent and significant taxonomic revision. Mitochondrial (mt) genomes can be a useful molecular marker for phylogenetics but, to date, sequences have been available for only a relatively small subset of Heterobranchia. Results To assess the utility of mitochondrial genomes for resolving evolutionary relationships within this clade, eleven new mt genomes were sequenced including representatives of several groups of “lower heterobranchs”. Maximum likelihood analyses of concatenated matrices of the thirteen protein coding genes found weak support for most higher-level relationships even after several taxa with extremely high rates of evolution were excluded. Bayesian inference with the CAT + GTR model resulted in a reconstruction that is much more consistent with the current understanding of heterobranch phylogeny. Notably, this analysis recovered Valvatoidea and Orbitestelloidea in a polytomy with a clade including all other heterobranchs, highlighting these taxa as important to understanding early heterobranch evolution. Also, dramatic gene rearrangements were detected within and between multiple clades. However, a single gene order is conserved across the majority of heterobranch clades. Conclusions Analysis of mitochondrial genomes in a Bayesian framework with the site heterogeneous CAT + GTR model resulted in a topology largely consistent with the current understanding of heterobranch phylogeny. However, mitochondrial genomes appear to be too variable to serve as good phylogenetic markers for robustly resolving a number of deeper splits within this clade.publishedVersio

Neither slugs nor snails: a molecular reappraisal of the gastropod family Velutinidae

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

The bubble snails (Gastropoda, Heterobranchia) of Mozambique: an overlooked biodiversity hotspot

This first account, dedicated to the shallow water marine heterobranch gastropods of Mozambique is presented with a focus on the clades Acteonoidea and Cephalaspidea. Specimens were obtained as a result of sporadic sampling and two dedicated field campaigns between the years of 2012 and 2015, conducted along the northern and southern coasts of Mozambique. Specimens were collected by hand in the intertidal and subtidal reefs by snorkelling or SCUBA diving down to a depth of 33 m. Thirty-two species were found, of which 22 are new records to Mozambique and five are new for the Western Indian Ocean. This account raises the total number of shallow water Acteonoidea and Cephalaspidea known in Mozambique to 39 species, which represents approximately 50 % of the Indian Ocean diversity and 83 % of the diversity of these molluscs found in the Red Sea. A gap in sampling was identified in the central swamp/mangrove bio-region of Mozambique, and therefore, we suggest that future research efforts concentrate on or at least consider this region.publishedVersio

The taxonomic status of the headshield slug genus Nakamigawaia Kuroda and Habe, 1961 (Gastropoda: Cephalaspidea: Aglajidae), with the description of a new species from the Western Pacific

Nakamigawaia is a poorly understood genus of Aglajidae sea slugs with only two species formally ascribed. In this paper we explore new morpho-anatomical characters using stereo and scanning electron microscopy and employ different molecular approaches (a cytochrome c oxidase sub-unit I gene phylogeny, the Automatic Barcode Gap Discovery species delimitation method, and genetic distances) to compare specimens across the geographical span of the genus and from two distinct chromatic morphotypes occurring in the Western Pacific (blackish morph and white-dotted morph). Our results support the conspecificity of these two morphs and show they belong to an undescribed species here named Nakamigawaia nakanoae sp. nov. The species differs from the type species of the genus, N. spiralis, by the presence of a distinct open-dilated shell and differs from its Western Atlantic congener N. felis by subtle differences in the shell, male reproductive system and caudal lobes. Genetically (COI uncorrected p-distance) the two species (N. nakanoae and N. felis) are 18.8–20.1% distinct. The definition of the genus Nakamigawaia is discussed and the current assignment to the latter of lineages other than the type species is questioned

Diaphana lactea Jeffreys 1877

Diaphana lactea (Jeffreys, 1877) (Figs 5 A–D, 6 A–D) Utriculus lacteus Jeffreys 1877: 334. Retusa lactea — Sykes 1905: 31, pl. 3, fig. 4 Diaphana lactea — Bouchet & Warén 1979: 229 –231, 237. Høisaeter 1986: 100. Schiøtte 1998: 122, figs 22 A, 24 A–C. Sneli et al. 2005: 96. Diaphana jonica Geronimo 1974: 151, 152, pl. 2 fig. 2 (based on Schiøtte 1998). Diagnosis. Shell external, white to transparent, elongate cylindrical, smooth. Body white. Foot posteriorly bifurcated, cephalic shield with tentacular lobes. Rachidian tooth denticulate, asymmetrical, lateral teeth with minute denticulation, teeth on left side smaller than on the right. Type locality. Station 12, Valorous expedition. Material examined. Norwegian Sea, off Trondheim (64 ° 16 ' 54 ’’ N, 00° 11 ' 42 ’’ W), 3 spcs (dissected), ZMBN 85923, H = 3.7, 3.8 mm. SE of Jan Mayen (70 ° 26 ' 12 ’’ N, 06° 31 ' 48 ’’ W), 1 spc (dissected), ZMBN 85934, H = 5.8 mm. Norwegian Sea, Trondheim area (63 ° 58 ' 12 ’’ N, 00° 23 ' 42 ’’ W), 1 spc (dissected), ZMBN 85932, H = 3.9 mm. North of Faroe Islands (63 ° 45 ' 12 ’’ N, 00°07' 60 ’’ W), 1 spc (dissected), ZMBN 85933, H = 3.9 mm. Between Iceland and Jan Mayen (68 ° 46 ' 57 " N, 012° 31 ' 39.6 " W), 3 sh, ZMBN 90574, H = 2.14–2.26 mm. Shell (Fig. 5 A–D): Maximum H = 5.8 mm. External, thick; white to whitish transparent; elongate cylindrical in shape, middle part of shell straight, narrowing anteriorly and posteriorly, other side uniformly rounded, aperture wide with thin parietal callus, columellar lip straight, apex sunken, mammillate, but protoconch not protruding top of last whorl, umbilicated; shell surface smooth. Animal: Body white. Foot posteriorly bifurcated. Cephalic shield with tentacular lobes posteriorly. Radula (Fig. 6 A–C): Radular formula 11 x 1.1. 1. Rachidian tooth with two flat denticulate lobes separated by gap with a pointed small cusp, lobes asymmetrical, right lobe larger. Lateral teeth long, inner edge denticulate. Radula asymmetrical with left inner laterals much smaller than the right laterals, one large denticle on tip of left laterals only. Male reproductive system (Fig. 6 D): Prostate emerging as undivided lump from penial sheath in a right angle, external seminal groove continuing as open groove through penial sheath. Ecology. Specimen examined by Schiøtte (1998) were found on mud, sand, silty sand, shell sand, clay, foraminifera, gravel and silt from 559–4268 m depth. Distribution. Reported from the Norwegian Sea, the Faroe Islands, the Denmark Strait, North Atlantic and the Mediterranean Sea (Schiøtte 1998; Høisaeter 2009; Sneli et al. 2005; present study). Remarks. This species was redescribed by Schiøtte (1998). Lemche (1948) did not include Diaphana lactea in his review of northern Atlantic species. During the present study denticulation of the rachidian tooth was found to be variable from almost absent to coarsely denticulate (fig. 6 F, G). The seminal groove continued as open channel in the penial sheath, which was not the case in the other Diaphana species studied here. It is most abundant below 2000 m depth and therefore considered a species of abyssal affinities (Høisaeter 2010).Published as part of Ohnheiser, Lena Tina & Malaquias, Manuel António E., 2014, The family Diaphanidae (Gastropoda: Heterobranchia: Cephalaspidea) in Europe, with a redescription of the enigmatic species C olobocephalus costellatus M. Sars, 1870, pp. 501-522 in Zootaxa 3774 (6) on pages 507-509, DOI: 10.11646/zootaxa.3774.6.1, http://zenodo.org/record/22721

FIGURE 4. Diaphana hiemalis. A in The family Diaphanidae (Gastropoda: Heterobranchia: Cephalaspidea) in Europe, with a redescription of the enigmatic species C olobocephalus costellatus M. Sars, 1870

FIGURE 4. Diaphana hiemalis. A. radula (LM). B. rachidian tooth (SEM). C. detail of lateral tooth (SEM). D. male reproductive system (drawing). Abbreviations: ga, genital aperture; pr, prostate; ps, penial sheath. Scale bars: A = 25 Μm; B = 3 Μm; C = 2 Μm; D = 250 Μm.Published as part of Ohnheiser, Lena Tina & Malaquias, Manuel António E., 2014, The family Diaphanidae (Gastropoda: Heterobranchia: Cephalaspidea) in Europe, with a redescription of the enigmatic species C olobocephalus costellatus M. Sars, 1870, pp. 501-522 in Zootaxa 3774 (6) on page 506, DOI: 10.11646/zootaxa.3774.6.1, http://zenodo.org/record/22721