[Mollusca • 2022] Dendronotus shpataki • A New Species of the Genus Dendronotus (Gastropoda: Nudibranchia) from the Sea of Japan: a contribution of citizen science to marine zoology

  

Dendronotus shpataki sp. nov. in natural environment.

Ekimova, Mikhlina, Antokhina & Schepetov, 2022

 

DOI: doi.org/10.31610/zsr/2022.31.1.3 

  Researchgate.net/publication/358210579

Photos by Andrey Shpatak.

Abstract

 The nudibranch genus Dendronotus Alder et Hancock, 1845 is a common component of boreal and arctic ecosystems, which has recently received a considerable attention due to its high cryptic diversity. Here we describe a new species Dendronotus shpataki sp. nov. from the northwestern Sea of Japan, using the material and observations provided by Andrey Shpatak, a local citizen, diver and underwater photographer. We studied morphological features of the new species, including external morphology, coloration, jaw and radular morphology, and configuration of the reproductive system, as well as its ecological traits including possible diet preferences. We obtained DNA sequences and reconstructed the phylogeny by Bayesian Inference and Maximum Likelihood approaches using four molecular markers (mitochondrial COI and 16S rRNA, and nuclear histone H3 and 28S rRNA), and tested the boundaries between the species by calculating the uncorrected p-distances and automatic species delimitation methods ABGD and GMYC. Our results show that D. shpataki sp. nov. differs both morphologically and genetically from all other Dendronotus species. The new species possibly represents a unique example of local endemism, being found in a single locality, while other local Dendronotus species demonstrate wide distribution in the North-West Pacific. We also report on a considerable wearing of the radular teeth during feeding, which is a remarkable case for the Dendronotus.

Key words: North-West Pacific, biodiversity, morphology, radula, molecular markers, phylogeny, Nudibranchia, Dendronotidae, Dendronotus, new species

Dendronotus shpataki sp. nov., general appearance of living specimens.
 Holotype: dorsal view (A), lateral view (B) and ventral view (C).
Paratypes, dorsal view: adult specimens MIMB42309 (D), MIMB42308 (E), MIMB42305 (F)
and juvenile MIMB42306 (G). 

Scale bar: 5 mm.

Dendronotus shpataki sp. nov. in natural environment.
 Paratype MIMB42302 (A–C); the first documented finding of the new species in May 2015,
 the specimen was not collected (D); paratypes MIMB42303 (E, F).

Photos by Andrey Shpatak.

Dendronotus shpataki sp. nov.

I.A. Ekimova, A.L. Mikhlina, T.I. Antokhina and D.M. Schepetov. 2022. A Description of Dendronotus shpataki sp. nov. (Gastropoda: Nudibranchia) from the Sea of Japan: a contribution of citizen science to marine zoology. Zoosystematica Rossica. 31(1); 3–19. DOI: 10.31610/zsr/2022.31.1.3 

  Researchgate.net/publication/358210579_A_description_of_Dendronotus_shpataki_from_the_Sea_of_Japan

[Mollusca • 2026] Thecacera sesama • A New Species of the Genus Thecacera (Nudibranchia: Polyceridae) from Taiwan, evident from morphology and phylogenetic analyses of the 16S rDNA and cytochrome c oxidase I gene

 

Thecacera sesama Chan & Lee,

in Chan, Lee, Chen, Chang, Shao et Pang, 2026. 

 DOI: doi.org/10.3897/zookeys.1279.184298

Abstract

Thecacera sesama Chan & Lee, sp. nov. (Nudibranchia, Polyceridae) is described from north-eastern Taiwan based on an integrative taxonomic approach combining morphological and molecular data. The new species is distinguished from its congeners by a unique colour pattern consisting of a translucent white body covered with numerous small, round, black pigment spots and fewer, larger, yellow spots and five gills. While sharing a similar spotted colour pattern with Thecacera pennigera, the new species can be clearly distinguished by its significantly smaller body size (maximum length < 3 mm). Phylogenetic analyses of two mitochondrial genes, cytochrome c oxidase subunit I (COI) and 16S rRNA, confirmed it as a new species in Thecacera. The molecular data places Thecacera sesama sp. nov. as a sister species to Thecacera picta, with a significant interspecific COI divergence of 14.17%. This discovery highlights the rich, yet under documented, marine biodiversity of Taiwan and underscores the value of combining traditional morphological examination with molecular phylogenetics for accurate species delimitation in cryptic nudibranch lineages.

Key words: bryozoans, COI, cryptic diversity, Heterobranchia, phylogeny, systematics, taxonomy

Living specimens of Thecacera sesama sp. nov.
A. Ecological photos; B. ASIZM0001722; C. ASIZM0001721. Scale bars: 1 mm.

Thecacera sesama sp. nov.
Details of appearance and morphological features, hand-drawn on a tablet PC by Chen-Lu Lee. 

Thecacera sesama Chan & Lee, sp. nov.

 

Diagnosis. Thecacera sesama sp. nov. is distinguished by a unique combination of the following external morphological characters: (1) maximum preserved length of specimens is 2.83 mm; (2) body colour is translucent whitish, allowing some internal organs to be faintly visible; (3) entire body, as well as the rhinophores, rhinophoral sheaths, gills, post-branchial appendages, propodial tentacles, and tail are covered with numerous, discrete, small, circular, black spots and large yellow spots, as well as many white, snowflake-shaped pigment patches scattered on the body; (4) rhinophores and rhinophoral sheaths are translucent whitish, with small black spots and large yellow spots; (5) rhinophoral lamellae number 9–12; (6) gills number 5 and are translucent whitish, and the branchial plumes are pinnate; (7) post-branchial appendages are translucent whitish; (8) the head is translucent whitish, with short, blunt propodial tentacles at the corners.

Etymology. The specific epithet sesama is derived from the Latin word for sesame seed, referring to the characteristic small, rounded, seed-like spots that cover the dorsal surface of this species, resembling scattered sesame seeds on the animal’s body.

 Ho-Yeung Chan, Chen-Lu Lee, Wei-Cheng Chen, Chia-Hao Chang, Yi-Ta Shao and Ka-Lai Pang. 2026. Thecacera sesama sp. nov. (Nudibranchia, Polyceridae) from Taiwan, evident from morphology and phylogenetic analyses of the 16S rDNA and cytochrome c oxidase I gene. ZooKeys. 1279: 269-284. DOI: doi.org/10.3897/zookeys.1279.184298 [11 May 2026]

[Mollusca • 2019] Okenia longiductis & O. problematica • What is really out there? Review of the Genus Okenia Menke, 1830 (Nudibranchia: Goniodorididae) in the Mediterranean Sea with Description of Two New Species

[A-D] Okenia longiductis 
Okenia problematica 

 Pola, Paz-Sedano, Macali, Minchin, Marchini, Vitale, Licchelli & Crocetta, 2019 

 DOI: 10.1371/journal.pone.0215037

Abstract

The precise number of Okenia taxa inhabiting the Mediterranean Sea, as well as their general taxonomy, varies according to different specialists. So far, eight valid species have been reported from the area: Okenia aspersa (Alder & Hancock, 1845), Okenia cupella (Vogel & Schultz, 1970), Okenia elegans (Leuckart, 1828), Okenia hispanica Valdés & Ortea, 1995, Okenia impexa Er. Marcus, 1957, Okenia leachii (Alder & Hancock, 1854), Okenia mediterranea (Ihering, 1886), and Okenia zoobotryon (Smallwood, 1910). Of these, only three (O. elegans, O. hispanica, and O. mediterranea) have their type localities in the Mediterranean Sea, whereas the others were described from different biogeographic areas and later included in the Mediterranean biota. We carried out a review on Mediterranean Okenia species through an integrative approach, based on a wide literature search and a morphological and molecular analysis of available type material and samples collected recently. The present study confirmed the presence of O. aspersa, O. elegans, O. hispanica, and O. mediterranea in the Mediterranean Sea, although leaving remaining questions about some of those taxa. The distribution of O. cupella, O. impexa, and O. zoobotryon is limited to the western Atlantic, and of O. leachii to the eastern Atlantic. All specimens previously identified as O. cupella, O. impexa, and O. zoobotryon by different authors in the Mediterranean Sea were repeatedly misidentified. Thus, we describe Okenia problematica sp. nov. and Okenia longiductis sp. nov., from the “Mediterranean” Okenia cupella/impexa and O. zoobotryon. We also consider here Okenia pusilla Sordi, 1974 a nomen dubium and include a redescription of the holotype of O. cupella. A molecular phylogeny, including all the sequenced Okenia species, was performed in order to evaluate the evolutionary relationships of the newly described species with the other congeneric taxa.

Systematics

Order Nudibranchia Cuvier, 1817

Family Goniodorididae H. Adams & A. Adams, 1854

Genus Okenia Menke, 1830

Type species: Idalia elegans Leuckart, 1828 by monotypy

 Okenia longiductis sp. nov.
A. Specimen from Lago di Sabaudia (Italy). Photograph by A. Macali. B. Specimen from La Grande-Motte (France). Photograph by D. Minchin. C. Egg-masses on Amathia verticillata from La Grande-Motte (France). Photograph by D. Minchin. D. Specimen from Mar Piccolo, Taranto (Italy). Photograph by G. Colucci. Size (alcohol-preserved specimens) ~9 mm maximum length.

Okenia longiductis sp. nov.

Etymology: Named longiductis due to its long reproductive ducts.

Ecology: We always found this species living in the infralittoral zone (up to 5 m depth) on the arborescent bryozoan Amathia verticillata (delle Chiaje, 1822) (Fig 3B and 3D). The same depths and feeding association hold for previous records belonging to Okenia zoobotryon. White and ring-shaped egg-masses were present on this bryozoan (Fig 3C).

 Okenia problematica sp. nov. Living animals from Gallipoli (Italy).
A. Holotype (MNCN15.05/200034); B. Paratype (SZN-MOL0001).
Photographs by F. Vitale. Size (alcohol-preserved specimens) ~2.5 mm maximum length.

Okenia problematica sp. nov.

Etymology: Named problematica due to its complex taxonomic history.

Ecology: We always found Okenia problematica sp. nov. at depths below 10 m. The specimens collected in Gallipoli (Italy) were found on an artificial reef located on a sandy bottom, amidst unidentified hydrozoans and encrusting bryozoans. ...

 Marta Pola, Sofía Paz-Sedano , Armando Macali, Dan Minchin, Agnese Marchini, Fabio Vitale, Cataldo Licchelli and Fabio Crocetta. 2019. What is really out there? Review of the Genus Okenia Menke, 1830 (Nudibranchia: Goniodorididae) in the Mediterranean Sea with Description of Two New Species.  PLoS ONE. 14(5): e0215037. DOI: 10.1371/journal.pone.0215037

[Mollusca • 2024] Bathydevius caudactylus • A remarkable bathypelagic Nudibranch (Nudibranchia: Bathydeviidae fam. nov.) from the North Pacific Ocean

 

Bathydevius caudactylus  

Robison & Haddock, 2024 

  

 DOI: doi.org/10.1016/j.dsr.2024.104414

Highlights: 

• We present a previously undescribed genus and species of deep-sea nudibranch.

• It has unique morphology and is not closely related to any known families.

• In a molecular phylogeny, it resolves as a distinct sister to the rest of known nudibranchs.

• The species is bioluminescent and represents the third independent origin of bioluminescence among nudibranchs.

Abstract

We describe an exceptional nudibranch, new to science, from bathypelagic depths in the eastern North Pacific Ocean. More than 100 individuals of Bathydevius caudactylus gen. et. sp. nov. have been observed in the water column at depths between 1013 and 3272 m. Twenty spawning individuals were observed on the seafloor at depths between 2269 and 4009 m. Anatomy, diet, behavior, bioluminescence, and habitat distinguish this surprising nudibranch from all previously described species, and genetic evidence supports its placement in a new family.

 

Keywords: Nudibranch, Bathypelagic, bioluminescence, Deep-sea, New species, New genus, New family

 

 Bathydevius caudactylus gen et sp. nov. in situ, from a video frame grab.

 Hood configuration modes for Bathydevius caudactylus gen et sp. nov.:
 (a) fully expanded; (b) the hood is closed around an open sphincter; (c) the hood is bi-lobed, closed along its vertical axis; (d) invagination in the upper margin with a pinched projection in the lower margin; (e) the peripheral lip of the hood is rolled back against the outer surface of the bell; (f) in a propulsive pulse.

Systematics

Class GASTROPODA.

Subclass HETEROBRANCHIA.

Order NUDIBRANCHIA

Suborder incertae sedis.

Family Bathydeviidae fam. nov.

Bathydevius gen. nov.

Bathydevius caudactylus sp. nov.

 Diagnosis: Bathydevius caudactylus gen. et sp. nov. (Fig. 1) is a mostly transparent, gelatinous nudibranch composed of three distinct regions: the head, supporting a voluminous, bell-shaped oral hood; a body enclosing the internal organs and bearing the columnar ventral foot; and a spatulate tail fringed with 9–16 caudal appendages “dactyls.” The dorsal surface has two stubby, unsheathed rhinophores and a gently curved ridge of gills with the anal opening just posterior to the center of the gill ridge. Ventrally, the body merges into a short, cylindrical foot. Visible through the transparent body, the stomach is typically red, the rugose digestive gland is orange or brown, and in mature individuals, gonadal tissue on the right side of the digestive gland is opaque white.

 

 Etymology: The generic name Bathydevius gen. nov. describes a deep-living deviation, to reflect its diversion from the evolutionary path of its relatives in appearance, molecular signature, and natural history. The species name caudactylus sp. nov. refers to the finger-like projections that line the posterior margin of the tail.

Bathydevius caudactylus gen et sp. nov. on the seafloor in the posture associated with the release of an egg-bearing ribbon. Distance between the red laser dots is 29 cm.

 Bioluminescence of Bathydevius caudactylus gen et sp. nov., recorded in situ. Light emanates from the surface of the oral hood and within the dactyls (at left).

Bruce H. Robison and Steven H.D. Haddock. 2024. Discovery and Description of A remarkable bathypelagic Nudibranch, Bathydevius caudactylus, gen. et. sp. nov. Deep Sea Research Part I: Oceanographic Research Papers. 214; 104414.  DOI: doi.org/10.1016/j.dsr.2024.104414

[Mollusca • 2023] Eubranchus flexus • A New Species of the Genus Eubranchus (Gastropoda: Nudibranchia) from Vietnamese Coastal Waters

Eubranchus flexus 

Grishina, Antokhina & Ekimova, 2023

  ruthenica.net/node/5976

 Researchgate.net/publication/366823950

A new species belonging to the Fionidae (sensu Cella et al., 2016), Eubranchus flexus sp. nov. is described based on specimens collected in Nha Trang, Vietnam, South China Sea, Indo-West Pacific, from the upper sublittoral depth. An integrative analysis was conducted, including a molecular phylogenetic analysis based on three markers (COI, 16S, H3), and an analysis of the external and internal morphology using light and scanning electron microscopy. The distinctiveness of Eubranchus flexus sp. nov. is well established both morphologically and genetically. Phylogenetically Eubranchus flexus sp. nov. represents a derived branch in the phylogeny of Eubranchus, but its relationships with other Eubranchus species are unresolved likely due to low taxon sampling. Eubranchus flexus sp. nov. is the first representative of the genus ifor the nudibranch fauna of Vietnam and for now its range is restricted only to the type locality.

Keywords: Indo-West Pacific; Fionidae; Mollusca; integrative systematics; biodiversity; species delimitation;

Living specimens of Eubranchus flexus sp. nov.
 A. Holotype ZMMU WS19111, dorsal view. B. Paratype ZMMUWS19112, dorsal view, specimens was damaged during collection. Size of the fixed specimens is around 4 mm.
C. Eubranchus flexus sp. nov. specimens with egg mass and the host hydrozoan colony; white arrows point to egg masses, black arrows with a white outline point to specimens.

Eubranchus flexus sp. nov.

Etymology. From Latin “flexus” (bending, winding, curvilinear), referring to specific shape of cerata in this species.

Darya Grishina, Tatiana Antokhina and Irina Ekimova. 2023. A New Species of the Genus Eubranchus (Gastropoda: Nudibranchia) from Vietnamese Coastal Waters. Ruthenica Russian Malacological Journal. 33(1):1-8. ruthenica.net/node/5976

DOI: 10.35885/ruthenica.2023.33(1).1

 Researchgate.net/publication/366823950_A_new_species_of_Eubranchus_from_Vietnamese_coastal_waters

[Mollusca • 2024] Phestilla arnoldi • Parasites or Predators? Gastropod Ectoparasites (Nudibranchia: Trinchesiidae) and their scleractinian host Corals at Koh Tao, Gulf of Thailand, with the Description of A New Species

Phestilla arnoldi Mehrotra & Caballer, 

in Mehrotra, Caballer, Kaullysing, Jualaong & Hoeksema, 2024.

DOI: 10.1007/s13199-023-00967-z

 facebook.com/ATMECorg 

Abstract

Recent years have seen a rapid increase in the study of coral-associated gastropods. In particular, the description of several new species in conjunction with their host specificity or dietary variability, has raised questions pertaining to their impact on reef health. These corallivores have been labelled as both ‘parasite’ and ‘predator’ by different studies, due to the tendency of some species to entirely consume their ‘host’ corals. Here we present new findings of corallivory and parasitism based on surveys conducted on the reefs of Koh Tao, Gulf of Thailand. A total of 6566 corals were assessed for their tendency to host gastropods of the nudibranch genus Phestilla and the caenogastropod family Epitoniidae. Thirteen gastropod species were found to be associated with 20 scleractinian coral species, including six that do not match the original description of previously known taxa. Herein we describe one of them, the first nudibranch proven to be associated with corals of the scleractinian genus Acropora and discuss conservation implications of these coral/gastropod relationships. Additionally, we explore the complex topic of defining these relationships as parasitic versus predatory and the merits of using these labels to better understand the ecology of these relationships.

 

Keywords: Acropora, Coral-associated gastropods, Corallivory, Epitoniidae, Phestilla, Predation

Phestilla arnoldi Mehrotra & Caballer sp. nov.
A–C: Pigmentation differences as mediated by recent feeding and the relative presence of endosymbiotic Symbiodiniaceae.
 D–F: Specimens in situ on their Acropora host, egg bundles indicated by black arrow. G: Right-anterior of a specimen under light microscopy with living Symbiodiniaceae cells along lateral digestive ducts, with an eye visible in the top right.

 Scale bars: A, B = 1 mm; C = 2 mm; D, E = 4 mm; F = 2 mm; G = 0.1 mm

Order Nudibranchia Cuvier, 1817

Superfamily Fionoidea Gray, 1857

Family Trinchesiidae Nordsieck, 1972

Genus Phestilla Bergh, 1874

Phestilla arnoldi Mehrotra & Caballer sp. nov.

 Etymology: Phestilla arnoldi Mehrotra & Caballer sp. nov. is named in honour of Mr. Spencer Arnold for his discovery of this highly cryptic species at Koh Tao, alongside contributing significantly to ectoparasite observations and records at Koh Tao during the survey period. In addition, Mr. Arnold has supported marine biology education and research, and has played an important role in biodiversity monitoring at Koh Tao and elsewhere.

 Rahul Mehrotra, Manuel Caballer, Deepeeka Kaullysing, Suthep Jualaong and Bert W. Hoeksema. 2024. Parasites or Predators? Gastropod Ectoparasites and their scleractinian host Corals at Koh Tao, Gulf of Thailand, with the Description of A New Species. Symbiosis. DOI: 10.1007/s13199-023-00967-z

 facebook.com/ATMECorg/posts/895366715924485

[Mollusca • 2022] Battle of the Bands: Systematics and Phylogeny of the white Goniobranchus nudibranchs with marginal bands (Nudibranchia: Chromodorididae)

[a–d] Goniobranchus fabulus

 Soong, Bonomo, Reimer & Gosliner, 2022 

Goniobranchus sinensis

DOI: 10.3897/zookeys.1083.72939

Abstract

Species identities of Goniobranchus nudibranchs with white bodies and various marginal bands have long been problematic. In this study, specimens of these Goniobranchus nudibranchs from the Philippines, Peninsular Malaysia, Japan, Papua New Guinea, and Madagascar were analyzed and molecular data were obtained in order to re-examine the relationships between species within this “white Goniobranchus with marginal bands” group. The analyses clearly recovered six species groups corresponding to the described species Goniobranchus albonares, G. preciosus, G. rubrocornutus, G. sinensis, and G. verrieri as well as one new species, G. fabulus Soong & Gosliner, sp. nov. Notably, G. preciosus, G. sinensis, G. rubrocornutus, G. verrieri, and G. fabulus Soong & Gosliner, sp. nov. exhibit color variation and polymorphism, suggesting that some aspects of color patterns (e.g., presence or absence of dorsal spots) may not always be useful in the identification of species in the “white Goniobranchus with marginal bands” group, whereas other features such as gill and rhinophore colors and the arrangement and colors of the mantle marginal bands are more diagnostic for each species.

Keywords: Biodiversity, coral reefs, mtDNA, species delimitation, taxonomy

a, b Goniobranchus albonares a CASIZ 191440, Papua New Guinea b CASIZ 228939, Philippines
c–f Goniobranchus preciosus c CASIZ 208415, Morphotype A, Philippines d CASIZ 208574, Morphotype B, Philippines e CASIZ 176752, Morphotype C, Peninsular Malaysia f CASIZ 176761, Morphotype D, Peninsular Malaysia
g, h Goniobranchus rubrocornutus g CASIZ 203047, Morphotype A, Philippines h CASIZ 208563, Morphotype B, Philippines.

Photographs Terrence M. Gosliner. Scale bars: 1 cm.

a–d Goniobranchus sinensis a CASIZ 176759, morphotype A, Peninsular Malaysia b MISE-018-19, morphotype B, Okinawa, Japan c MISE-55-19, morphotype B, Okinawa, Japan d MISE-039-19, morphotype C, Kagoshima, Japan
e, f Goniobranchus verrieri e CASIZ 203059, morphotype A, Philippines f CASIZ 208442, morphotype B, Philippines.

 Photographs a, e, f Terrence M. Gosliner; b–d Giun Yee Soong. Scale bars: 1 cm.

Goniobranchus fabulus sp. nov.
 a CASIZ 177517, morphotype A, Philippines b CASIZ 177685, morphotype A, Philippines c CASIZ 201949, morphotype A, Philippines d CASIZ 191118, morphotype B, Papua New Guinea.

 Photographs Terrence M. Gosliner. Scale bars: 1 cm.

 Giun Yee Soong, Lynn J. Bonomo, James D. Reimer and Terrence M. Gosliner. 2022. Battle of the Bands: Systematics and Phylogeny of the white Goniobranchus nudibranchs with marginal bands (Nudibranchia, Chromodorididae). ZooKeys. 1083: 169-210. DOI: 10.3897/zookeys.1083.72939

[Mollusca • 2023] Jorunna liviae • Can you find me? A New Sponge-like Nudibranch from the Genus Jorunna Bergh, 1876 (Gastropoda: Discodorididae)

Jorunna liviae

Tibiriçá, Strömvoll & Cervera, 2023

C. Jorunna liviae sp. nov. near its egg mass, and Favorinus sp. feeding on it; D. Close-up of Favorinus sp.; E. Jorunna liviae sp. nov. mating; F. Details of Jorunna liviae sp. nov. egg mass.

 DOI: 10.3897/zse.99.95222

Abstract

The nudibranch diversity of the western Indian Ocean is comparatively one of the least studied in the world. In this paper a sponge-like Discodoridae nudibranch Jorunna liviae sp. nov. is described. The description is based on integrative anatomy, including molecular analysis of two genes (the mitochondrial COI and the nuclear H3), dissections, electron microscopy (SEM) of buccal elements, micro tomography of the spicule’s arrangements and ecological observations. This study provides the first ever molecular data of Jorunna species from the western Indian Ocean, helping to fill the gap to further understand this apparent paraphyletic genus.

Key Words: biodiversity, Heterobranchia, Mozambique, new species, phylogeny, sea slugs

Jorunna liviae sp. nov. (MNCN15.05/200187) external morphology.
A. Dorsal view; B. Ventral view; C. SEM photography of dorsal caryophyllids; D. Rhinophores sheath details; E. Rhinophore; F. Gill branches.

Jorunna liviae sp. nov. in situ.
 A. Hosting sponge Amphimedon brevispiculifera (Dendy, 1905); B. Jorunna liviae sp. nov. resting on sponge; C. Jorunna liviae sp. nov. near its egg mass, and Favorinus sp. feeding on it; D. Close-up of Favorinus sp.; E. Jorunna liviae sp. nov. mating; F. Details of Jorunna liviae sp. nov. egg mass.

Order Nudibranchia Cuvier, 1817

Superfamily Doridoidea Rafinesque, 1815

Family Discodorididae Bergh, 1891

Genus Jorunna Bergh, 1876

Jorunna liviae Tibiriçá, Strömvoll & Cervera, sp. nov.

Diagnosis: Body elongate-ovulated. Dorsum pale gray to pink, covered on highly dense caryphyllidia; rhinophores short, with up to nine lamellae, ending in a knob apex; six to nine bipinnate branchial leaves encircling the anal pore. Radula with five to seven very thin pectinated outermost teeth bearing long bundled fibrous denticles. Labial cuticle smooth. Copulatory spine with bifid apex.

Etymology: This species is dedicated to Livia Renée Cornelius, daughter of the second author of this paper.

Habitat: Specimens were collected on submerged subtropical compressed sandstone reefs in Ponta do Ouro, Mozambique.

 Yara Tibiriçá, Jenny Strömvoll and Juan Lucas Cervera. 2023. Can you find me? A New Sponge-like Nudibranch from the Genus Jorunna Bergh, 1876 (Mollusca, Gastropoda, Discodorididae). Zoosystematics and Evolution 99(1): 63-75. DOI: 10.3897/zse.99.95222

[Mollusca • 2022] The First Phylogenetic and Species Delimitation Study of the Nudibranch Genus Gymnodoris (Gastropoda: Nudibranchia) reveals High Species Diversity

in Knutson & Gosliner, 2022. 

DOI: 10.1016/j.ympev.2022.107470

Highlights: 

• First phylogenetic study of the nudibranch genus Gymnodoris.

• Gymnodoris comprises three main clades and is most closely related to the genera Vayssierea and Lecithophorus.

• A linear gill arrangement appears to have evolved multiple times within Gymnodoris.

• Genus Analogium, defined by a linear gill arrangement, is maintained as a junior synonym of Gymnodoris.

• At least 81% of Gymnodoris is undescribed.

Abstract

Nudibranchs are charismatic marine gastropods that lack a shell in the adult stage. While most nudibranchs feed on sessile animals such as sponges, bryozoans, and cnidarians, the nudibranch genus Gymnodoris Stimpson, 1855 evolved a more active and predatory lifestyle, including sea slug predation, cannibalism, and oddly enough, fish-fin parasitism. At the beginning of our work, no phylogenetic hypothesis existed for the genus, nor a clear picture of how Gymnodoris is related to other nudibranchs. Here we set out to reconstruct Gymnodoris phylogeny, investigate species diversity, and clarify the status of the genus name Analogium, which had been proposed for members of the genus with a linear gill filament arrangement. We present the first phylogenetic hypothesis for Gymnodoris, reconstructed by maximum likelihood and Bayesian inference using two mitochondrial and two nuclear loci, with gill filament arrangement plotted on the phylogeny. The backbone of the phylogeny remains unresolved with theseloci, however, we found that Gymnodoris comprises three main well-supported clades, which we refer to as the “subornata”, “citrina” and “varied” clade, the latter two clades being comprised of several well-supported subclades. The sister group to Gymnodoris is a clade including the genera Vayssierea and Lecithophorus. Based on ABGD and PTP species delimitation methods, we conservatively estimate 65–70 species comprise our dataset. We further estimate that approximately 81% of the species we sampled are undescribed, and note that a linear gill filament arrangement has evolved multiple times within the genus. Gymnodoris is only monophyletic when the species with a linear gill arrangement are included. Therefore, at this time, we agree with the synonymy of Analogium striata with Gymnodoris striata by Rudman and Darvell (1990) and that the genus name Analogium is warranted as a junior synonym of Gymnodoris. Given the extensive undescribed diversity, and lack of resolution at some of the nodes in the phylogeny, patterns of diversification in diet are impossible to discern at this time and will require a large effort to both describe Gymnodoris species diversity and the diets of these candidate species.

 

Keywords: Opisthobranch, Heterobranchia, Cryptic diversity, Indo-Pacific, Polyceridae

Conservation statement and conclusion: 

Undescribed and undocumented diversity is cause for concern on many levels; it hinders our understanding of evolutionary and ecological processes and our ability to communicate that information within and outside of the scientific community. The latter is perhaps most pressing of all in today’s world, as this lack of data directly impacts conservation. Without a robust assessment of the diversity of species in many locations, coastal communities lack information that can inform conservation decisions. This is particularly true in developing regions with high pressure on marine resources, which is characteristic of the highly diverse Western Pacific and specifically the Coral Triangle, the center of marine diversity (Carpenter et al., 2010) where Gymnodoris and many of its relatives are found.

We provide here the first ever phylogenetic hypothesis for the genus Gymnodoris, which has enabled us to begin to clarify Gymnodoris taxonomy and provided evidence supporting the synonymy of Analogium with Gymnodoris. We can now begin to ask what the significance is, if any, of linear gill arrangement in this lineage, and continue to determine the diets of Gymnodoris species, including of all of the newly distinguished species we have identified here. The results of our species delimitations provide taxonomic hypotheses that will help researchers distinguish between and describe diversity within Gymnodoris and ultimately help us to study and understand the role that diet and feeding have played in the evolution of this highly diverse group of nudibranchs.

 

  

 Vanessa L. Knutson and Terrence M. Gosliner. 2022. The First Phylogenetic and Species Delimitation Study of the Nudibranch Genus Gymnodoris reveals High Species Diversity (Gastropoda: Nudibranchia). Molecular Phylogenetics and Evolution. 171; 107470. DOI: 10.1016/j.ympev.2022.107470

[Mollusca • 2021] Jorunna artsdatabankia • The Genus Jorunna (Nudibranchia: Discodorididae) in Europe: A New Species and A possible Case of Incipient Speciation

Jorunna artsdatabankia 

 Neuhaus, Rauch, Bakken, Picton, Pola & Malaquias, 2021

DOI: 10.1093/mollus/eyab028 

 twitter.com/RauchCessa 

 invertebrate.w.UIB.no

ABSTRACT

To investigate the conspecificity of different morphotypes of Jorunna tomentosa (Cuvier, 1804) (type species of genus Jorunna Bergh, 1876), we studied specimens sampled from across part of the geographical distribution of the species, using a combination of morphoanatomical characters and molecular phylogenetics. Bayesian and maximum likelihood phylograms were inferred based on the mitochondrial genes cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA, and the nuclear gene histone H3. We used the automatic barcode gap discovery method to aid in species delimitation. COI genetic uncorrected p-distances were estimated between and within species. Animals were dissected and the reproductive system, radulae and labial cuticles were examined; scanning electron microscopy was employed to study ultrastructural elements of anatomical characters. The results revealed the presence of a new species (Jorunna artsdatabankia n. sp.) and a possible case of incipient speciation in J. tomentosa with our COI data indicating the presence of two morphoanatomically indistinct lineages that are separated from each other by distances of 3.2–5.0%. The genetic distance between J. artsdatabankia n. sp. and its sister species J. tomentosa was 9.0–12.3%; the former species is characterized by a plain white to yellow background colour with irregularly placed small brown spots, smooth radular teeth and a longer vas deferens, wider vagina and a longer copulatory spine (up to 600 μm longer) than the latter. A diagnostic comparison of all species of European Jorunna is included, as well as a discussion of the assignment of J. lemchei to the genus Gargamella.

Jorunna artsdatabankia n. sp.

 

Jenny Neuhaus, Cessa Rauch, Torkild Bakken, Bernard Picton, Marta Pola and Manuel António E Malaquias. 2021. The Genus Jorunna (Nudibranchia: Discodorididae) in Europe: A New Species and A possible Case of Incipient Speciation. Journal of Molluscan Studies. 87(4); eyab028. DOI: 10.1093/mollus/eyab028 

 twitter.com/RauchCessa/status/1447470016249671683 

Hello Jorunna artsdatabankia; new sea slug for Norway and to the World!

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[Mollusca • 2020] Habitat, Morphology and Trophism of Tritonia callogorgiae sp. nov., A Large Nudibranch Inhabiting Callogorgia verticillata Forests in the Mediterranean Sea

Tritonia callogorgiae Chimienti, Furfaro & Taviani

in Chimienti, Angeletti, Furfaro, Canese & Taviani, 2020. 

DOI: 10.1016/j.dsr.2020.103364 

 facebook.com/GioChimienti 

 

Highlights

• A forest of the Primnoidae Callogorgia verticillata was found in the Adriatic Sea.

• The forest develops between 420 and 426 m depth, with a mean density of 1.34 colonies m−2.

• The nudibranch Tritonia callogorgiae sp. nov. is described strictly associated with the corals.

• Our study describes the first deep-sea tritoniid in the Mediterranean Sea.

• Stomach content analysis showed that Tritonia callogorgiae sp. nov. feeds on C. verticillata.

Abstract

The continuing exploration of the Mediterranean deep sea reveals that a complete census of the biodiversity of one of the most studied marine areas in the world is yet to be fully accomplished. A tritoniid nudibranch new to science is described upon material recovered off the Montenegro margin, Adriatic Sea, associated with the alcyonacean Primnoidae Callogorgia verticillata (Pallas, 1766). Here, a coral forest dominated by C. verticillata, together with other alcyonaceans, antipatharians and scleractinians, represents the habitat of the new species. As documented by Remotely Operated Vehicle (ROV) observations, the coral forest covers an area of 600 m2 at 420–426 m depth, with dense growth of C. verticillata colonies (1.34 ± 0.08 colonies m−2). As many as 66 nudibranch specimens have been observed on C. verticillata. Tritonia callogorgiae sp. nov. (Gastropoda, Nudibranchia, Tritoniidae) is up to 12 cm long, yellow to orange/reddish in colour with white papillae all over the body. It has a velum with six appendages (three per side), and 4–5 pairs of dichotomous gills. Internally, the species is distinguished from other tritoniids for the absence of stomach plates and a distinctive radula with formula 50 × 110.1.1.1.108. It represents the first case of Tritonia species living in the deep Mediterranean Sea and the only one associated to C. verticillata. Stomach content documents that Tritonia callogorgiae sp. nov. feeds on C. verticillata. Further visual ROV records from other sectors of the Mediterranean Sea indicate that the distribution of this new described species is almost basin-wide. The discovery of another undescribed member of the benthic megafauna related to deep-sea coral grounds further highlights the need for conservation of such habitats.

 

Keywords: Coral forest, Alcyonacea, Primnoidae, Mollusca, Nudibranchia, Mediterranean sea

Tritonia callogorgiae sp. nov. (paratype A_31_1; MUZAC-6555). in vivo.

Order Nudibranchia Cuvier, 1817

Family Tritoniidae Lamarck, 1809.

Genus Tritonia Cuvier, 1798

Tritonia callogorgiae Chimienti, Furfaro & Taviani, sp. nov.

Etymology: The name identifies the consistent association of the news species with the Primnoidae sea fan Callogorgia verticillata.

 Conclusions: 

The presence of rare or uncommon taxa represents a robust argument for the consideration of their host habitats as meritorious for proper conservation measures. In this respect, forests of C. verticillata represent a unique habitat for several associated species, including the newly discovered Tritonia callogorgiae sp. nov. This study provides the elements to identify this noticeable species even based solely on images and without the need of complex sampling operations. It is expected that further records of T. callogorgiae sp. nov. will be added in the future, as part of new deep-sea explorations and monitoring programs all over the Mediterranean Sea. Colorful and extravagant invertebrates like nudibranchs are often noted for their vibrant colour palettes and widely appreciated from an aesthetic point of view. They could thus act as ‘flag species’ to push general public and decision makers towards the importance to protect the vulnerable habitats where they live.

Giovanni Chimienti, Lorenzo Angeletti, Giulia Furfaro, Simonepietro Canese and Marco Taviani. 2020. Habitat, Morphology and Trophism of Tritonia callogorgiae sp. nov., A Large Nudibranch Inhabiting Callogorgia verticillata Forests in the Mediterranean Sea. Deep Sea Research Part I: Oceanographic Research Papers. 165: 103364. DOI: 10.1016/j.dsr.2020.103364

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