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Bernard Picton

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I am the curator of marine invertebrates at NMNI, formerly the Ulster Museum. My interests are in the systematics and identification of Nudibranch molluscs, Porifera (sponges), Cnidaria (sea anemones and hydroids), Tunicata (sea squirts) and Echinoderms. I work mostly on the NE Atlantic fauna and have an interest in relational databases and internet applications.
Address: Department of Natural Sciences,
National Museums Northern Ireland,
Cultra, Holywood, Co. Down, BT18 0EU

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Christian Meyer

Natural History Museum Basel

Universidade dos Açores

Royal Ontario Museum

Sérgio Stampar

Universidade Estadual Paulista "Júlio de Mesquita Filho"

Guillaume Jacques

Centre National de la Recherche Scientifique / French National Centre for Scientific Research

Vicencio de la Cruz Francisco

Universidad Veracruzana

Viacheslav Kuleshov

Stockholm University

Universiti Kebangsaan Malaysia

Ege University

Makamas Sutthacheep

Ramkhamhaeng university

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Papers by Bernard Picton

Figure 20 from: Korshunova T, Martynov A, Bakken T, Evertsen J, Fletcher K, Mudianta WI, Saito H, Lundin K, Schrödl M, Picton B (2017) Polyphyly of the traditional family Flabellinidae affects a major group of Nudibranchia: aeolidacean taxonomic reassessment with descriptions of several new famil...

A new species of Sakuraeolis from Mozambique, described using 3D reconstruction of anatomy and phylogenetic analysis

Journal of Molluscan Studies

Here we describe a new species of shallow-subtidal nudibranch from south-eastern Africa. The stri... more Here we describe a new species of shallow-subtidal nudibranch from south-eastern Africa. The strikingly vivid orange sea slug with white markings belongs to the long-disputed family Facelinidae, and has been photographed and recorded in the region by divers for some time. Tomographic modelling was applied to produce a 3D anatomical reconstruction of the reproductive and digestive organs from serial sections. A molecular phylogeny using multiple markers (cytochrome c oxidase subunit I, 16S rRNA and histone H3) recovered three distinct clades within the paraphyletic Facelinidae, in agreement with other recent studies. This topology supported a genus-level clade, including the type species of Sakuraeolis Baba, 1965, S. enosimensis Baba, 1930, the new species described herein, S. arcana n. sp., and an undescribed sibling species that shares morphological resemblance to S. arcana n. sp. Facelina quatrefagesi Vayssière, 1888 is also recognized as Caloria quatrefagesi n. comb. on the basis...

Multiple paedomorphic lineages of soft-substrate burrowing invertebrates: parallels in the origin of Xenocratena and Xenoturbella

PLOS ONE

Research Infrastructures offer capacity to address scientific questions never attempted before: Are all taxa equal?

Research Infrastructures (RIs) are facilities, resources and services used by the scientific comm... more Research Infrastructures (RIs) are facilities, resources and services used by the scientific community to conduct research and foster innovation. LifeWatch ERIC has developed various virtual research environments, which include many virtual laboratories (vLabs) offering high computational capacity and comprehensive collaborative platforms that supporting the needs of digital biodiversity science. Over its 250 years of history, the taxonomic research community has developed a system for describing, classifying and naming taxa across multiple levels. For the marine biota, taxonomic information is organized and made publicly available through the World Register of Marine Species (WoRMS) that records more than 250,000 described valid species. Although scientists tend to assign an equal status (in terms of contribution to overall diversity) to each taxon used in taxonomy, biogeography, ecology and biodiversity, the question “are all taxa equal?” has never been tested at a global scale. W...

Multilevel fine-scale diversity challenges the ‘cryptic species’ concept

Scientific Reports

Cryptic' species are an emerging biological problem that is broadly discussed in the present stud... more Cryptic' species are an emerging biological problem that is broadly discussed in the present study. Recently, a cryptic species definition was suggested for those species which manifest low morphological, but considerable genetic, disparity. As a case study we present unique material from a charismatic group of nudibranch molluscs of the genus Trinchesia from European waters to reveal three new species and demonstrate that they show a dual nature: on one hand, they can be considered a 'cryptic' species complex due to their overall similarity, but on the other hand, stable morphological differences as well as molecular differences are demonstrated for every species in that complex. Thus, this species complex can equally be named 'cryptic', 'pseudocryptic' or 'non-cryptic'. We also present evidence for an extremely rapid speciation rate in this species complex and link the species problem with epigenetics. Available metazoan-wide data, which are broadly discussed in the present study, show the unsuitability of a 'cryptic' species concept because the degree of crypticity represents a continuum when a finer multilevel morphological and molecular scale is applied to uncover more narrowly defined species making the 'cryptic' addition to 'species' redundant. Morphological and molecular methods should be applied in concordance to form a fine-scale multilevel taxonomic framework, and not necessarily implying only an a posteriori transformation of exclusively molecularbased 'cryptic' species into morphologically-defined 'pseudocryptic' ones. Implications of the present study have importance for many fields, including conservation biology and fine-scale biodiversity assessments. The 'cryptic species' concept is widely used in modern biodiversity studies 1 and implies that there are morphologically indistinguishable species that can be recognized only by molecular data 2,3. The term 'cryptic species' became popular relatively recently 4,5 and has supplanted the term 'sibling species' which was commonly used in previous cases with difficult-to-distinguish species 6. Despite the fact that the 'cryptic species' concept has received considerable attention and is now used in various applications, it is intrinsically contradictory and might also be confused with other uses of the word 'cryptic'. For example, the exact same 'cryptic species' term is used in ecology to denote that some species are very well camouflaged on some substrates 7. Recently, the difficulty of delineating the 'cryptic species' concept from the basic biological species definition was highlighted, and it was suggested that this concept should be used with care and only as a temporary formalization for taxonomic complexes for which a robust morphological framework is not yet established 8. In a further discussion, Struck et al. 9 rather disagreed and attempted to build a definition of 'cryptic' species on a lower degree of phenotypic (morphological) disparity than non-cryptic relatives. However, to define an exact degree of morphological disparity is very difficult, if it is possible at all, so Heethoff 10 further concluded that the current 'cryptic

The formerly enigmatic Unidentiidae in the limelight again: a new species of the genus Unidentia from Thailand (Gastropoda: Nudibranchia)

Zootaxa

An integrative molecular and morphological study is presented for the family Unidentiidae. Molecu... more An integrative molecular and morphological study is presented for the family Unidentiidae. Molecular phylogenetic analyses were conducted with the inclusion of all previous and newly obtained molecular data for the family Unidentiidae Millen & Hermosillo 2012. A new species of the genus Unidentia Millen & Hermosillo 2012, U. aliciae sp. nov., is described from Thailand as part of an inventory of sea slugs at Koh Tao. All up-to-date available morphological data for the species of the genus Unidentia is for the first time summarized. Morphological differences among the different species of Unidentia are clarified showing that every species has its own distinguishable morphological traits. According to the new molecular and morphological data, the family Unidentiidae is re-confirmed as a well-supported taxon of the aeolidacean nudibranchs. The taxonomy and phylogeny of the Aeolidacea in the light of the family Unidentiidae is briefly discussed and necessity of a fine-scale and narrowly...

Figure 3 from: Martynov A, Mehrotra R, Chavanich S, Nakano R, Kashio S, Lundin K, Picton B, Korshunova T (2019) The extraordinary genus Myja is not a tergipedid, but related to the Facelinidae s. str. with the addition of two new species from Japan (Mollusca, Nudibranchia). ZooKeys 818: 89-116. h...

Morphological and molecular data are presented for the first time in an integrative way for the g... more Morphological and molecular data are presented for the first time in an integrative way for the genus Myja Bergh, 1896. In accordance with the new molecular phylogenies, the traditional Facelinidae is paraphyletic. Herein is presented the phylogenetic placement of true Facelinidae s. str., including the first molecular data for F. auriculata (Müller, 1776), type species of the genus Facelina Alder & Hancock, 1855. The taxonomic history of F. auriculata is reviewed. The genus Myja is related to the clade Facelinidae s. str., but shows disparate morphological traits. Two new species of the genus Myja, M. karin sp. n., and M. hyotan sp. n., are described from the Pacific waters of Japan (middle Honshu), and M. cf. longicornis Bergh, 1896 is investigated from Thailand. According to molecular analysis and review of available morphological information, the genus Myja contains more hidden diversity. The family-level relationship within aeolidacean nudibranchs with emphasis on the family Facelinidae is outlined. The problem of the relationship between Facelinidae Bergh,

Figure 5 from: Martynov A, Mehrotra R, Chavanich S, Nakano R, Kashio S, Lundin K, Picton B, Korshunova T (2019) The extraordinary genus Myja is not a tergipedid, but related to the Facelinidae s. str. with the addition of two new species from Japan (Mollusca, Nudibranchia). ZooKeys 818: 89-116. h...

Morphological and molecular data are presented for the first time in an integrative way for the g... more Morphological and molecular data are presented for the first time in an integrative way for the genus Myja Bergh, 1896. In accordance with the new molecular phylogenies, the traditional Facelinidae is paraphyletic. Herein is presented the phylogenetic placement of true Facelinidae s. str., including the first molecular data for F. auriculata (Müller, 1776), type species of the genus Facelina Alder & Hancock, 1855. The taxonomic history of F. auriculata is reviewed. The genus Myja is related to the clade Facelinidae s. str., but shows disparate morphological traits. Two new species of the genus Myja, M. karin sp. n., and M. hyotan sp. n., are described from the Pacific waters of Japan (middle Honshu), and M. cf. longicornis Bergh, 1896 is investigated from Thailand. According to molecular analysis and review of available morphological information, the genus Myja contains more hidden diversity. The family-level relationship within aeolidacean nudibranchs with emphasis on the family Facelinidae is outlined. The problem of the relationship between Facelinidae Bergh,

Figure 2 from: Martynov A, Mehrotra R, Chavanich S, Nakano R, Kashio S, Lundin K, Picton B, Korshunova T (2019) The extraordinary genus Myja is not a tergipedid, but related to the Facelinidae s. str. with the addition of two new species from Japan (Mollusca, Nudibranchia). ZooKeys 818: 89-116. h...

Morphological and molecular data are presented for the first time in an integrative way for the g... more Morphological and molecular data are presented for the first time in an integrative way for the genus Myja Bergh, 1896. In accordance with the new molecular phylogenies, the traditional Facelinidae is paraphyletic. Herein is presented the phylogenetic placement of true Facelinidae s. str., including the first molecular data for F. auriculata (Müller, 1776), type species of the genus Facelina Alder & Hancock, 1855. The taxonomic history of F. auriculata is reviewed. The genus Myja is related to the clade Facelinidae s. str., but shows disparate morphological traits. Two new species of the genus Myja, M. karin sp. n., and M. hyotan sp. n., are described from the Pacific waters of Japan (middle Honshu), and M. cf. longicornis Bergh, 1896 is investigated from Thailand. According to molecular analysis and review of available morphological information, the genus Myja contains more hidden diversity. The family-level relationship within aeolidacean nudibranchs with emphasis on the family Facelinidae is outlined. The problem of the relationship between Facelinidae Bergh,

Figure 1 from: Martynov A, Mehrotra R, Chavanich S, Nakano R, Kashio S, Lundin K, Picton B, Korshunova T (2019) The extraordinary genus Myja is not a tergipedid, but related to the Facelinidae s. str. with the addition of two new species from Japan (Mollusca, Nudibranchia). ZooKeys 818: 89-116. h...

Morphological and molecular data are presented for the first time in an integrative way for the g... more Morphological and molecular data are presented for the first time in an integrative way for the genus Myja Bergh, 1896. In accordance with the new molecular phylogenies, the traditional Facelinidae is paraphyletic. Herein is presented the phylogenetic placement of true Facelinidae s. str., including the first molecular data for F. auriculata (Müller, 1776), type species of the genus Facelina Alder & Hancock, 1855. The taxonomic history of F. auriculata is reviewed. The genus Myja is related to the clade Facelinidae s. str., but shows disparate morphological traits. Two new species of the genus Myja, M. karin sp. n., and M. hyotan sp. n., are described from the Pacific waters of Japan (middle Honshu), and M. cf. longicornis Bergh, 1896 is investigated from Thailand. According to molecular analysis and review of available morphological information, the genus Myja contains more hidden diversity. The family-level relationship within aeolidacean nudibranchs with emphasis on the family Facelinidae is outlined. The problem of the relationship between Facelinidae Bergh,

Figure 4 from: Martynov A, Mehrotra R, Chavanich S, Nakano R, Kashio S, Lundin K, Picton B, Korshunova T (2019) The extraordinary genus Myja is not a tergipedid, but related to the Facelinidae s. str. with the addition of two new species from Japan (Mollusca, Nudibranchia). ZooKeys 818: 89-116. h...

Morphological and molecular data are presented for the first time in an integrative way for the g... more Morphological and molecular data are presented for the first time in an integrative way for the genus Myja Bergh, 1896. In accordance with the new molecular phylogenies, the traditional Facelinidae is paraphyletic. Herein is presented the phylogenetic placement of true Facelinidae s. str., including the first molecular data for F. auriculata (Müller, 1776), type species of the genus Facelina Alder & Hancock, 1855. The taxonomic history of F. auriculata is reviewed. The genus Myja is related to the clade Facelinidae s. str., but shows disparate morphological traits. Two new species of the genus Myja, M. karin sp. n., and M. hyotan sp. n., are described from the Pacific waters of Japan (middle Honshu), and M. cf. longicornis Bergh, 1896 is investigated from Thailand. According to molecular analysis and review of available morphological information, the genus Myja contains more hidden diversity. The family-level relationship within aeolidacean nudibranchs with emphasis on the family Facelinidae is outlined. The problem of the relationship between Facelinidae Bergh,

The extraordinary genus Myja is not a tergipedid, but related to the Facelinidae s. str. with the addition of two new species from Japan (Mollusca, Nudibranchia)

ZooKeys

Morphological and molecular data are presented for the first time in an integrative way for the g... more Morphological and molecular data are presented for the first time in an integrative way for the genus Myja Bergh, 1896. In accordance with the new molecular phylogenies, the traditional Facelinidae is paraphyletic. Herein is presented the phylogenetic placement of true Facelinidae s. str., including the first molecular data for F.auriculata (Müller, 1776), type species of the genus Facelina Alder & Hancock, 1855. The taxonomic history of F.auriculata is reviewed. The genus Myja is related to the clade Facelinidae s. str., but shows disparate morphological traits. Two new species of the genus Myja, M.karinsp. n., and M.hyotansp. n., are described from the Pacific waters of Japan (middle Honshu), and M.cf.longicornis Bergh, 1896 is investigated from Thailand. According to molecular analysis and review of available morphological information, the genus Myja contains more hidden diversity. The family-level relationship within aeolidacean nudibranchs with emphasis on the family Facelinida...

The genus Zelentia is an amphi-boreal taxon expanded to include three new species from the North Pacific and Atlantic oceans (Gastropoda: Nudibranchia: Trinchesiidae)

Zootaxa

The taxonomy of Zelentia Korshunova, Martynov & Picton, 2017, a genus of aeolidacean nudibranchs ... more The taxonomy of Zelentia Korshunova, Martynov & Picton, 2017, a genus of aeolidacean nudibranchs recently separated from Trinchesia Ihering, 1879, is reviewed. Using previous and novel data, including the defining morphological characters of a supplementary gland inserted into the penis, which is also armed with stylet, it is demonstrated that the genus Zelentia is a well-established amphi-boreal taxon. A phylogenetic tree and haplotype network for species of the genus Zelentia are provided. A new species from the Northeastern Pacific, Zelentia willowsi sp. nov. and a second Northeastern Pacific species, Zelentia nepunicea sp. nov., previously thought to be “Cuthona” pustulata (Alder & Hancock, 1854), are described using morphological and molecular data. A new species from the North Atlantic and sub-Arctic White Sea, Zelentia roginskae sp. nov., is also described using morphological and molecular data. The Northeastern Pacific Zelentia nepunicea sp. nov. and“Cuthona” punicea Millen,...

First true brackish-water nudibranch mollusc provides new insights for phylogeny and biogeography and reveals paedomorphosis-driven evolution

PLOS ONE

A unique example of brackish water fjord-related diversification of a new nudibranch genus and sp... more A unique example of brackish water fjord-related diversification of a new nudibranch genus and species Bohuslania matsmichaeli gen. n., sp. n. is presented. There are only few previously known brackish-water opisthobranchs and B. matsmichaeli gen. n., sp. n. is the first ever described brackish-water nudibranch with such an extremely limited known geographical range and apparently strict adherence to salinity levels lower than 20 per mille. Up to date the new taxon has been found only in a very restricted area in the Idefjord, bordering Sweden and Norway, but not in any other apparently suitable localities along the Swedish and Norwegian coasts. We also show in this study for the first time the molecular phylogenetic sister relationship between the newly discovered genus Bohuslania and the genus Cuthona. This supports the validity of the family Cuthonidae, which was re-established recently. Furthermore, it contributes to the understanding of the evolutionary patterns and classification of the whole group Nudibranchia. Molecular and morphological data indicate that brackish water speciation was triggered by paedomorphic evolution among aeolidacean nudibranchs at least two times independently. Thus, the present discovery of this new nudibranch genus contributes to several biological fields, including integration of molecular and morphological data as well as phylogenetic and biogeographical patterns.

Pycnoclavella stolonialis n. sp. (Tunicata: Ascidiacea), with phylogenetic and distributional remarks on the genus in Europe

Zootaxa

Morphological and molecular data based on the COI gene were used to describe a new species of the... more Morphological and molecular data based on the COI gene were used to describe a new species of the colonial ascidian genus Pycnoclavella. The new species, P. stolonialis, is widespread sublittorally in the Irish Sea and also occurs on the western Irish coast, Wales and eastern England and may be locally common. It has been commonly known as the ‘pin head’ sea squirt since first recorded from Northern Ireland in 1984 but has not yet been formally described. P. stolonialis is the only described species of Pycnoclavella combining the presence of stolons, peribranchial incubation mode and a larva lacking an otolith. In addition, it features ca. 10% sequence divergence with the closest species of the genus in our phylogenetic trees. P. stolonialis showed intermediate characters between two groups of Pycnoclavella; the stanleyi and the aurilucens groups. Larval morphology and molecular data supported the inclusion of P. stolonialis within the aurilucens group, but the stolonial colony stru...

Polyphyly of the traditional family Flabellinidae affects a major group of Nudibranchia: aeolidacean taxonomic reassessment with descriptions of several new families, genera, and species (Mollusca, Gastropoda)

ZooKeys, 2017

The Flabellinidae, a heterogeneous assembly of supposedly plesiomorphic to very derived sea slug ... more The Flabellinidae, a heterogeneous assembly of supposedly plesiomorphic to very derived sea slug groups, have not yet been addressed by integrative studies. Here novel material of rarely seen Arctic taxa as well as North Atlantic, North and South Pacific, and tropical Indo-West Pacific flabellinid species is investigated morpho-anatomically and with multi-locus markers (partial COI, 16S rDNA, 28S rDNA and H3) which were generated and analysed in a comprehensive aeolid taxon sampling. It was found that the current family Flabellinidae is polyphyletic and its phylogeny and taxonomic patterns cannot be understood without considering members from all the Aeolidacean families and, based on a robust phylogenetic hypothesis, morpho-anatomical evolution of aeolids is more complex than suspected in earlier works and requires reclassification of the taxon. Morphological diversity of Flabellinidae is corroborated by molecular divergence rates and supports establishing three new families (Apata...

Corrigenda: Polyphyly of the traditional family Flabellinidae affects a major group of Nudibranchia: aeolidacean taxonomic reassessment with descriptions of several new families, genera, and species (Mollusca, Gastropoda). https://doi.org/10.3897/zookeys.717.21885

ZooKeys, 2017

In our recently published study the traditional Flabellinidae underwent a major revision and 17 n... more

External diversity is restrained by internal conservatism: New nudibranch mollusc contributes to the cryptic species problem

Zoologica Scripta

The most northern records of the exotic ascidian Perophora japonica Oka, 1927 (Ascidiacea: Perophoridae) in the north-east Atlantic

BioInvasions Records

Ontogeny as an important part of integrative taxonomy in tergipedid aeolidaceans (Gastropoda: Nudibranchia) with a description of a new genus and species from the Barents Sea

Zootaxa

The taxonomy of aeolidacean nudibranchs of the traditional group previously known as Tergipedidae... more The taxonomy of aeolidacean nudibranchs of the traditional group previously known as Tergipedidae is discussed. To integrate the diverse molecular phylogenetic pattern and morphological disparity in a broadly ontogenetic context a revised classification at the family level is presented. The families Calmidae Iredale & O'Donoghue, 1923, Eubranchidae Odhner, 1934, Fionidae Gray, 1857 s. str. (restricted, with the genus Fiona only), and Tergipedidae Bergh, 1889 s.str. (restricted, with inclusion of the genus Tergipes only) are restored. The families Cuthonidae Odhner, 1934 s.str. (restricted, with only single genus Cuthona), Cuthonellidae Miller, 1971, stat. nov., and Trinchesiidae Nordsieck, 1972 (with inclusion of the genera Catriona, Diaphoreolis, Phestilla, Tenellia, Trinchesia) are reinstated. At the genus level, the family Trinchesiidae appears as a most diverse assemblage that needs to be further divided. In the present study, the “Eolis” pustulata species complex is particu...

Figure 20 from: Korshunova T, Martynov A, Bakken T, Evertsen J, Fletcher K, Mudianta WI, Saito H, Lundin K, Schrödl M, Picton B (2017) Polyphyly of the traditional family Flabellinidae affects a major group of Nudibranchia: aeolidacean taxonomic reassessment with descriptions of several new famil...

A new species of Sakuraeolis from Mozambique, described using 3D reconstruction of anatomy and phylogenetic analysis

Journal of Molluscan Studies

Here we describe a new species of shallow-subtidal nudibranch from south-eastern Africa. The stri... more Here we describe a new species of shallow-subtidal nudibranch from south-eastern Africa. The strikingly vivid orange sea slug with white markings belongs to the long-disputed family Facelinidae, and has been photographed and recorded in the region by divers for some time. Tomographic modelling was applied to produce a 3D anatomical reconstruction of the reproductive and digestive organs from serial sections. A molecular phylogeny using multiple markers (cytochrome c oxidase subunit I, 16S rRNA and histone H3) recovered three distinct clades within the paraphyletic Facelinidae, in agreement with other recent studies. This topology supported a genus-level clade, including the type species of Sakuraeolis Baba, 1965, S. enosimensis Baba, 1930, the new species described herein, S. arcana n. sp., and an undescribed sibling species that shares morphological resemblance to S. arcana n. sp. Facelina quatrefagesi Vayssière, 1888 is also recognized as Caloria quatrefagesi n. comb. on the basis...

Multiple paedomorphic lineages of soft-substrate burrowing invertebrates: parallels in the origin of Xenocratena and Xenoturbella

PLOS ONE

Research Infrastructures offer capacity to address scientific questions never attempted before: Are all taxa equal?

Research Infrastructures (RIs) are facilities, resources and services used by the scientific comm... more Research Infrastructures (RIs) are facilities, resources and services used by the scientific community to conduct research and foster innovation. LifeWatch ERIC has developed various virtual research environments, which include many virtual laboratories (vLabs) offering high computational capacity and comprehensive collaborative platforms that supporting the needs of digital biodiversity science. Over its 250 years of history, the taxonomic research community has developed a system for describing, classifying and naming taxa across multiple levels. For the marine biota, taxonomic information is organized and made publicly available through the World Register of Marine Species (WoRMS) that records more than 250,000 described valid species. Although scientists tend to assign an equal status (in terms of contribution to overall diversity) to each taxon used in taxonomy, biogeography, ecology and biodiversity, the question “are all taxa equal?” has never been tested at a global scale. W...

Multilevel fine-scale diversity challenges the ‘cryptic species’ concept

Scientific Reports

Cryptic' species are an emerging biological problem that is broadly discussed in the present stud... more Cryptic' species are an emerging biological problem that is broadly discussed in the present study. Recently, a cryptic species definition was suggested for those species which manifest low morphological, but considerable genetic, disparity. As a case study we present unique material from a charismatic group of nudibranch molluscs of the genus Trinchesia from European waters to reveal three new species and demonstrate that they show a dual nature: on one hand, they can be considered a 'cryptic' species complex due to their overall similarity, but on the other hand, stable morphological differences as well as molecular differences are demonstrated for every species in that complex. Thus, this species complex can equally be named 'cryptic', 'pseudocryptic' or 'non-cryptic'. We also present evidence for an extremely rapid speciation rate in this species complex and link the species problem with epigenetics. Available metazoan-wide data, which are broadly discussed in the present study, show the unsuitability of a 'cryptic' species concept because the degree of crypticity represents a continuum when a finer multilevel morphological and molecular scale is applied to uncover more narrowly defined species making the 'cryptic' addition to 'species' redundant. Morphological and molecular methods should be applied in concordance to form a fine-scale multilevel taxonomic framework, and not necessarily implying only an a posteriori transformation of exclusively molecularbased 'cryptic' species into morphologically-defined 'pseudocryptic' ones. Implications of the present study have importance for many fields, including conservation biology and fine-scale biodiversity assessments. The 'cryptic species' concept is widely used in modern biodiversity studies 1 and implies that there are morphologically indistinguishable species that can be recognized only by molecular data 2,3. The term 'cryptic species' became popular relatively recently 4,5 and has supplanted the term 'sibling species' which was commonly used in previous cases with difficult-to-distinguish species 6. Despite the fact that the 'cryptic species' concept has received considerable attention and is now used in various applications, it is intrinsically contradictory and might also be confused with other uses of the word 'cryptic'. For example, the exact same 'cryptic species' term is used in ecology to denote that some species are very well camouflaged on some substrates 7. Recently, the difficulty of delineating the 'cryptic species' concept from the basic biological species definition was highlighted, and it was suggested that this concept should be used with care and only as a temporary formalization for taxonomic complexes for which a robust morphological framework is not yet established 8. In a further discussion, Struck et al. 9 rather disagreed and attempted to build a definition of 'cryptic' species on a lower degree of phenotypic (morphological) disparity than non-cryptic relatives. However, to define an exact degree of morphological disparity is very difficult, if it is possible at all, so Heethoff 10 further concluded that the current 'cryptic

The formerly enigmatic Unidentiidae in the limelight again: a new species of the genus Unidentia from Thailand (Gastropoda: Nudibranchia)

Zootaxa

An integrative molecular and morphological study is presented for the family Unidentiidae. Molecu... more An integrative molecular and morphological study is presented for the family Unidentiidae. Molecular phylogenetic analyses were conducted with the inclusion of all previous and newly obtained molecular data for the family Unidentiidae Millen & Hermosillo 2012. A new species of the genus Unidentia Millen & Hermosillo 2012, U. aliciae sp. nov., is described from Thailand as part of an inventory of sea slugs at Koh Tao. All up-to-date available morphological data for the species of the genus Unidentia is for the first time summarized. Morphological differences among the different species of Unidentia are clarified showing that every species has its own distinguishable morphological traits. According to the new molecular and morphological data, the family Unidentiidae is re-confirmed as a well-supported taxon of the aeolidacean nudibranchs. The taxonomy and phylogeny of the Aeolidacea in the light of the family Unidentiidae is briefly discussed and necessity of a fine-scale and narrowly...

Figure 3 from: Martynov A, Mehrotra R, Chavanich S, Nakano R, Kashio S, Lundin K, Picton B, Korshunova T (2019) The extraordinary genus Myja is not a tergipedid, but related to the Facelinidae s. str. with the addition of two new species from Japan (Mollusca, Nudibranchia). ZooKeys 818: 89-116. h...

Morphological and molecular data are presented for the first time in an integrative way for the g... more Morphological and molecular data are presented for the first time in an integrative way for the genus Myja Bergh, 1896. In accordance with the new molecular phylogenies, the traditional Facelinidae is paraphyletic. Herein is presented the phylogenetic placement of true Facelinidae s. str., including the first molecular data for F. auriculata (Müller, 1776), type species of the genus Facelina Alder & Hancock, 1855. The taxonomic history of F. auriculata is reviewed. The genus Myja is related to the clade Facelinidae s. str., but shows disparate morphological traits. Two new species of the genus Myja, M. karin sp. n., and M. hyotan sp. n., are described from the Pacific waters of Japan (middle Honshu), and M. cf. longicornis Bergh, 1896 is investigated from Thailand. According to molecular analysis and review of available morphological information, the genus Myja contains more hidden diversity. The family-level relationship within aeolidacean nudibranchs with emphasis on the family Facelinidae is outlined. The problem of the relationship between Facelinidae Bergh,

Figure 5 from: Martynov A, Mehrotra R, Chavanich S, Nakano R, Kashio S, Lundin K, Picton B, Korshunova T (2019) The extraordinary genus Myja is not a tergipedid, but related to the Facelinidae s. str. with the addition of two new species from Japan (Mollusca, Nudibranchia). ZooKeys 818: 89-116. h...

Morphological and molecular data are presented for the first time in an integrative way for the g... more Morphological and molecular data are presented for the first time in an integrative way for the genus Myja Bergh, 1896. In accordance with the new molecular phylogenies, the traditional Facelinidae is paraphyletic. Herein is presented the phylogenetic placement of true Facelinidae s. str., including the first molecular data for F. auriculata (Müller, 1776), type species of the genus Facelina Alder & Hancock, 1855. The taxonomic history of F. auriculata is reviewed. The genus Myja is related to the clade Facelinidae s. str., but shows disparate morphological traits. Two new species of the genus Myja, M. karin sp. n., and M. hyotan sp. n., are described from the Pacific waters of Japan (middle Honshu), and M. cf. longicornis Bergh, 1896 is investigated from Thailand. According to molecular analysis and review of available morphological information, the genus Myja contains more hidden diversity. The family-level relationship within aeolidacean nudibranchs with emphasis on the family Facelinidae is outlined. The problem of the relationship between Facelinidae Bergh,

Figure 2 from: Martynov A, Mehrotra R, Chavanich S, Nakano R, Kashio S, Lundin K, Picton B, Korshunova T (2019) The extraordinary genus Myja is not a tergipedid, but related to the Facelinidae s. str. with the addition of two new species from Japan (Mollusca, Nudibranchia). ZooKeys 818: 89-116. h...

Morphological and molecular data are presented for the first time in an integrative way for the g... more Morphological and molecular data are presented for the first time in an integrative way for the genus Myja Bergh, 1896. In accordance with the new molecular phylogenies, the traditional Facelinidae is paraphyletic. Herein is presented the phylogenetic placement of true Facelinidae s. str., including the first molecular data for F. auriculata (Müller, 1776), type species of the genus Facelina Alder & Hancock, 1855. The taxonomic history of F. auriculata is reviewed. The genus Myja is related to the clade Facelinidae s. str., but shows disparate morphological traits. Two new species of the genus Myja, M. karin sp. n., and M. hyotan sp. n., are described from the Pacific waters of Japan (middle Honshu), and M. cf. longicornis Bergh, 1896 is investigated from Thailand. According to molecular analysis and review of available morphological information, the genus Myja contains more hidden diversity. The family-level relationship within aeolidacean nudibranchs with emphasis on the family Facelinidae is outlined. The problem of the relationship between Facelinidae Bergh,

Figure 1 from: Martynov A, Mehrotra R, Chavanich S, Nakano R, Kashio S, Lundin K, Picton B, Korshunova T (2019) The extraordinary genus Myja is not a tergipedid, but related to the Facelinidae s. str. with the addition of two new species from Japan (Mollusca, Nudibranchia). ZooKeys 818: 89-116. h...

Morphological and molecular data are presented for the first time in an integrative way for the g... more Morphological and molecular data are presented for the first time in an integrative way for the genus Myja Bergh, 1896. In accordance with the new molecular phylogenies, the traditional Facelinidae is paraphyletic. Herein is presented the phylogenetic placement of true Facelinidae s. str., including the first molecular data for F. auriculata (Müller, 1776), type species of the genus Facelina Alder & Hancock, 1855. The taxonomic history of F. auriculata is reviewed. The genus Myja is related to the clade Facelinidae s. str., but shows disparate morphological traits. Two new species of the genus Myja, M. karin sp. n., and M. hyotan sp. n., are described from the Pacific waters of Japan (middle Honshu), and M. cf. longicornis Bergh, 1896 is investigated from Thailand. According to molecular analysis and review of available morphological information, the genus Myja contains more hidden diversity. The family-level relationship within aeolidacean nudibranchs with emphasis on the family Facelinidae is outlined. The problem of the relationship between Facelinidae Bergh,

Figure 4 from: Martynov A, Mehrotra R, Chavanich S, Nakano R, Kashio S, Lundin K, Picton B, Korshunova T (2019) The extraordinary genus Myja is not a tergipedid, but related to the Facelinidae s. str. with the addition of two new species from Japan (Mollusca, Nudibranchia). ZooKeys 818: 89-116. h...

Morphological and molecular data are presented for the first time in an integrative way for the g... more Morphological and molecular data are presented for the first time in an integrative way for the genus Myja Bergh, 1896. In accordance with the new molecular phylogenies, the traditional Facelinidae is paraphyletic. Herein is presented the phylogenetic placement of true Facelinidae s. str., including the first molecular data for F. auriculata (Müller, 1776), type species of the genus Facelina Alder & Hancock, 1855. The taxonomic history of F. auriculata is reviewed. The genus Myja is related to the clade Facelinidae s. str., but shows disparate morphological traits. Two new species of the genus Myja, M. karin sp. n., and M. hyotan sp. n., are described from the Pacific waters of Japan (middle Honshu), and M. cf. longicornis Bergh, 1896 is investigated from Thailand. According to molecular analysis and review of available morphological information, the genus Myja contains more hidden diversity. The family-level relationship within aeolidacean nudibranchs with emphasis on the family Facelinidae is outlined. The problem of the relationship between Facelinidae Bergh,

The extraordinary genus Myja is not a tergipedid, but related to the Facelinidae s. str. with the addition of two new species from Japan (Mollusca, Nudibranchia)

ZooKeys

Morphological and molecular data are presented for the first time in an integrative way for the g... more Morphological and molecular data are presented for the first time in an integrative way for the genus Myja Bergh, 1896. In accordance with the new molecular phylogenies, the traditional Facelinidae is paraphyletic. Herein is presented the phylogenetic placement of true Facelinidae s. str., including the first molecular data for F.auriculata (Müller, 1776), type species of the genus Facelina Alder & Hancock, 1855. The taxonomic history of F.auriculata is reviewed. The genus Myja is related to the clade Facelinidae s. str., but shows disparate morphological traits. Two new species of the genus Myja, M.karinsp. n., and M.hyotansp. n., are described from the Pacific waters of Japan (middle Honshu), and M.cf.longicornis Bergh, 1896 is investigated from Thailand. According to molecular analysis and review of available morphological information, the genus Myja contains more hidden diversity. The family-level relationship within aeolidacean nudibranchs with emphasis on the family Facelinida...

The genus Zelentia is an amphi-boreal taxon expanded to include three new species from the North Pacific and Atlantic oceans (Gastropoda: Nudibranchia: Trinchesiidae)

Zootaxa

The taxonomy of Zelentia Korshunova, Martynov & Picton, 2017, a genus of aeolidacean nudibranchs ... more The taxonomy of Zelentia Korshunova, Martynov & Picton, 2017, a genus of aeolidacean nudibranchs recently separated from Trinchesia Ihering, 1879, is reviewed. Using previous and novel data, including the defining morphological characters of a supplementary gland inserted into the penis, which is also armed with stylet, it is demonstrated that the genus Zelentia is a well-established amphi-boreal taxon. A phylogenetic tree and haplotype network for species of the genus Zelentia are provided. A new species from the Northeastern Pacific, Zelentia willowsi sp. nov. and a second Northeastern Pacific species, Zelentia nepunicea sp. nov., previously thought to be “Cuthona” pustulata (Alder & Hancock, 1854), are described using morphological and molecular data. A new species from the North Atlantic and sub-Arctic White Sea, Zelentia roginskae sp. nov., is also described using morphological and molecular data. The Northeastern Pacific Zelentia nepunicea sp. nov. and“Cuthona” punicea Millen,...

First true brackish-water nudibranch mollusc provides new insights for phylogeny and biogeography and reveals paedomorphosis-driven evolution

PLOS ONE

A unique example of brackish water fjord-related diversification of a new nudibranch genus and sp... more A unique example of brackish water fjord-related diversification of a new nudibranch genus and species Bohuslania matsmichaeli gen. n., sp. n. is presented. There are only few previously known brackish-water opisthobranchs and B. matsmichaeli gen. n., sp. n. is the first ever described brackish-water nudibranch with such an extremely limited known geographical range and apparently strict adherence to salinity levels lower than 20 per mille. Up to date the new taxon has been found only in a very restricted area in the Idefjord, bordering Sweden and Norway, but not in any other apparently suitable localities along the Swedish and Norwegian coasts. We also show in this study for the first time the molecular phylogenetic sister relationship between the newly discovered genus Bohuslania and the genus Cuthona. This supports the validity of the family Cuthonidae, which was re-established recently. Furthermore, it contributes to the understanding of the evolutionary patterns and classification of the whole group Nudibranchia. Molecular and morphological data indicate that brackish water speciation was triggered by paedomorphic evolution among aeolidacean nudibranchs at least two times independently. Thus, the present discovery of this new nudibranch genus contributes to several biological fields, including integration of molecular and morphological data as well as phylogenetic and biogeographical patterns.

Pycnoclavella stolonialis n. sp. (Tunicata: Ascidiacea), with phylogenetic and distributional remarks on the genus in Europe

Zootaxa

Morphological and molecular data based on the COI gene were used to describe a new species of the... more Morphological and molecular data based on the COI gene were used to describe a new species of the colonial ascidian genus Pycnoclavella. The new species, P. stolonialis, is widespread sublittorally in the Irish Sea and also occurs on the western Irish coast, Wales and eastern England and may be locally common. It has been commonly known as the ‘pin head’ sea squirt since first recorded from Northern Ireland in 1984 but has not yet been formally described. P. stolonialis is the only described species of Pycnoclavella combining the presence of stolons, peribranchial incubation mode and a larva lacking an otolith. In addition, it features ca. 10% sequence divergence with the closest species of the genus in our phylogenetic trees. P. stolonialis showed intermediate characters between two groups of Pycnoclavella; the stanleyi and the aurilucens groups. Larval morphology and molecular data supported the inclusion of P. stolonialis within the aurilucens group, but the stolonial colony stru...

Polyphyly of the traditional family Flabellinidae affects a major group of Nudibranchia: aeolidacean taxonomic reassessment with descriptions of several new families, genera, and species (Mollusca, Gastropoda)

ZooKeys, 2017

The Flabellinidae, a heterogeneous assembly of supposedly plesiomorphic to very derived sea slug ... more The Flabellinidae, a heterogeneous assembly of supposedly plesiomorphic to very derived sea slug groups, have not yet been addressed by integrative studies. Here novel material of rarely seen Arctic taxa as well as North Atlantic, North and South Pacific, and tropical Indo-West Pacific flabellinid species is investigated morpho-anatomically and with multi-locus markers (partial COI, 16S rDNA, 28S rDNA and H3) which were generated and analysed in a comprehensive aeolid taxon sampling. It was found that the current family Flabellinidae is polyphyletic and its phylogeny and taxonomic patterns cannot be understood without considering members from all the Aeolidacean families and, based on a robust phylogenetic hypothesis, morpho-anatomical evolution of aeolids is more complex than suspected in earlier works and requires reclassification of the taxon. Morphological diversity of Flabellinidae is corroborated by molecular divergence rates and supports establishing three new families (Apata...

Corrigenda: Polyphyly of the traditional family Flabellinidae affects a major group of Nudibranchia: aeolidacean taxonomic reassessment with descriptions of several new families, genera, and species (Mollusca, Gastropoda). https://doi.org/10.3897/zookeys.717.21885

ZooKeys, 2017

In our recently published study the traditional Flabellinidae underwent a major revision and 17 n... more

External diversity is restrained by internal conservatism: New nudibranch mollusc contributes to the cryptic species problem

Zoologica Scripta

The most northern records of the exotic ascidian Perophora japonica Oka, 1927 (Ascidiacea: Perophoridae) in the north-east Atlantic

BioInvasions Records

Ontogeny as an important part of integrative taxonomy in tergipedid aeolidaceans (Gastropoda: Nudibranchia) with a description of a new genus and species from the Barents Sea

Zootaxa

The taxonomy of aeolidacean nudibranchs of the traditional group previously known as Tergipedidae... more The taxonomy of aeolidacean nudibranchs of the traditional group previously known as Tergipedidae is discussed. To integrate the diverse molecular phylogenetic pattern and morphological disparity in a broadly ontogenetic context a revised classification at the family level is presented. The families Calmidae Iredale & O'Donoghue, 1923, Eubranchidae Odhner, 1934, Fionidae Gray, 1857 s. str. (restricted, with the genus Fiona only), and Tergipedidae Bergh, 1889 s.str. (restricted, with inclusion of the genus Tergipes only) are restored. The families Cuthonidae Odhner, 1934 s.str. (restricted, with only single genus Cuthona), Cuthonellidae Miller, 1971, stat. nov., and Trinchesiidae Nordsieck, 1972 (with inclusion of the genera Catriona, Diaphoreolis, Phestilla, Tenellia, Trinchesia) are reinstated. At the genus level, the family Trinchesiidae appears as a most diverse assemblage that needs to be further divided. In the present study, the “Eolis” pustulata species complex is particu...