Cuthonellidae Miller, 1977

Korshunova, Tatiana, Fletcher, Karin & Martynov, Alexander, 2025, The endless forms are the most differentiated-how taxonomic pseudo-optimization masked natural diversity and evolution: the nudibranch case, Zoological Journal of the Linnean Society 204 (4) : -

publication ID

https://doi.org/10.1093/zoolinnean/zlaf057

publication LSID

lsid:zoobank.org:pub:D09886E-5D7C-40D1-B86A-118A3ADE5773

persistent identifier

https://treatment.plazi.org/id/03EF87FE-FFA6-FFF9-FC5D-F913FAE8F83D

treatment provided by

Plazi

scientific name

Cuthonellidae Miller, 1977
status

 

Family Cuthonellidae Miller, 1977 View in CoL

( Figs 1, 2; Table 4)

Subfamily Cuthonellinae Miller 1977: 200 . FamilyCuthonellidae,restored:Korshunova etal. 2017c: 9, 14, 17, 18. Korshunova et al. 2021: 223.

Korshunova et al. 2017a: 73–8, supplementary materials.

Diagnosis: Body wide to narrow. Notal edge completely reduced. Cerata non-elevated, numerous per row. Ceratal rows branched or simple. Rhinophores smooth to wrinkled. Anus acleioproctic, more rarely cleioproctic. Masticatory edges of jaws bear several to single row of distinct, sharpened to compound denticles. Radula formula 0.1.0. Central teeth usually with strong to moderately distinct cusp, not compressed by adjacent lateral denticles. Distal receptaculum seminis. Vas deferens usually moderate, prostate indistinct. Supplementary gland present, inserts into vas deferens in all confirmed cases. Massive external permanent penial collar absent. Penis internal, commonly narrow, unarmed, in one unique case very broad with a ring of lobes at the tip.

Genera included: Cuthonella Bergh, 1884 , type species, C. abyssicola Bergh, 1884 , diagnosis is ‘body wide with branched pre-anal ceratal rows, with up to at least 17 branched rows in the type species (minimum no less than c. seven to eight in included species), cleioproctic anus, protruding cusp of central teeth of radula with strong cusp not clearly delineated from lateral denticles in type species, to more distinct cusp, supplementary gland inserts to vas deferens on a considerable distance, penial sheath and penis non-widened, receptaculum seminis commonly distinct, on a very long, or a long stalk’, species and subspecies included C. abyssicola abyssicola Bergh, 1884 , C. abyssicola kryos Korshunova et al., 2020 , C. punicea ( Millen, 1986) , C. sandrae Korshunova et al., 2020 . Fiocuthona Martynov, 1992 , and type species F. concinna (Alder and Hancock, 1843) , diagnosis is ‘body narrow, up to six unbranched pre-anal rows, anus acleioproctic, radular teeth with commonly protruding, distinct cusp, penis with narrow base and supplementary gland insert to vas deferens relatively closer to penial sheath, commonly nonstalked, indistinct from very short stalk receptaculum seminis’, subspecies include F. concinna concinna (Alder and Hancock, 1843) , F. concinna bellatula (Korshunova et al., 2020) . Margina Martynov and Korshunova, 2025 , and type species Margina cocoachroma ( Williams and Gosliner, 1979) , diagnosis is ‘body narrow, up to four unbranched pre-anal rows, anus acleioproctic, radular teeth with commonly moderate to non-protruding cusp, penial sheath and penis with broadened base and supplementary gland inserted to the penis, the latter feature is unique for the family Cuthonellidae , but not confirmed independently, receptaculum seminis distinct with short stalk’. Nella Martynov and Korshunova, 2025, type species N. soboli (Martynov, 1992) , diagnosis is ‘body moderately wide to narrow, usually less than eight pre-anal ceratal rows, ceratal rows commonly unbranched to rarely partly branched, anus commonly acleioproctic (rarely cleioproctic), central teeth with distinct cusp and denticles, supplementary gland inserts into vas deferens commonly on a moderate distance, penial sheath not widened significantly, penis commonly elongated conical, without circle of lobes at the tip, receptaculum seminis distinct with a moderate stalk’; besides from type species, includes N. ainu (Korshunova et al., 2020) , N. anastasia ( Ekimova et al., 2024) , N. benedykti (Korshunova et al., 2020) , N. denbei (Korshunova et al., 2020) , N. georgstelleri (Korshunova et al., 2020) , N. hiemalis ( Roginskaya, 1987) , N. orientosiberica (Korshunova et al., 2020) comb. nov., N. osyoro (Baba, 1940) , N. rgo ( Korshunova and Martynov, 2022) , N. yermolyevae Martynov and Korshunova, 2025 . Penistella Martynov and Korshunova, 2025, and type species P. elenae (Martynov, 2000) , diagnosis is ‘body wide, ceratal rows mostly unbranched, but branched rows also present, more than 15 pre-anal rows, cleioproctic anus, radular teeth with protruding cusp and distinct denticles, supplementary gland inserts to vas deferens, but placed on penial sheath, penial sheath and penis very wide, tip of penis with star-like ring of papillae, receptaculum seminis distinct with a long stalk’. Developmentally, the genus Nella, including the type species N. soboli and at least several closely related species ( Martynov 1992a, Korshunova et al. 2021), exhibits direct development, whereas all so far known species of the genera Fiocuthona and Margina , and at least one species of the genus Cuthonella proper, undergo planctonic development ( Millen 1986, Goddard 1991, Martynov and Korshunova 2011). These differences are consistent with the phylogeographic patterns, since Nella inhabits coldest true Arctic and NW Pacific shallow waters, whereas Fiocuthona inhabits boreal, temperate waters of the North Atlantic and NE Pacific, and Margina the single cuthonellid genus known so far, which definitely penetrates subtropical waters ( Korshunova et al. 2021, Martynov and Korshunova 2025). Victima Martynov and Korshunova, 2025 , type species V. vasentsovichi (Korshunova et al., 2020) , diagnosis is ‘body wide, ceratal rows branched, 10 and more branched and unbranched pre-anal ceratal rows, anus cleioproctic, central teeth with strong cusp and distinct denticles, supplementary gland inserts into vas deferens on a moderate distance, penial sheath not widened, penis elongated conical, unarmed, without circle of lobes at the tip, receptaculum seminis distinct with a moderate stalk’.

Remarks: The family Cuthonellidae is the only family within Fionoidea with a number of species in which a supplementary gland is inserted into the vas deferens and not into penis ( Martynov 1992a, Korshunova et al. 2021). As mentioned above, such a character within Fionoidea is so far only reliably documented in a single restricted genus, Eubranchus , of the family Eubranchidae , which is distantly related to Cuthonellidae , and in the phylogenetically related, but otherwise dramatically different, family Calmidae , which itself contains only a few species (see below). Thus, we propose that insertion of a supplementary gland into the vas deferens is an ancestral feature, and potentially may be discovered within other taxa, which by no means can be considered as a basis for a family-level synonymyzation, because in every family there is a particular combination of characters of different levels. For instance, the family Cuthonellidae , represents a coherent, well-defined morphological and molecular ( Figs 1, 2) taxonomic unit, combining in various genera, branched-to-simple ceratal rows, cleioproctic or acleioproctic anus, radula with protruding cusp, unarmed penis, and predominant presence of a supplementary gland inserted into the vas deferens (see genera Cuthonellidae synopsis above, and molecular phylogenetic analysis in: Korshunova et al. 2021). Therefore, if the family Cuthonellidae were lumped into putative ‘Fionidae’, it would fundamentally obscure the unique combination of the ancestral insertion of a supplementary gland into the vas deferens plus various degrees of simplification of the initial branched ceratal pattern, thus fundamentally undermining any possibility for reliable diagnostics within any family of the superfamily Fionoidea and the suborder Aeolidacea because the true family Fionidae , with the inclusion of the stem-name bearing genus Fiona , does not possess any supplementary gland at all (see: Korshunova et al. 2017c, 2021, 2022, Martynov and Korshunova 2025, present study, Synopsis above and below).

Kingdom

Animalia

Phylum

Mollusca

Class

Gastropoda

Order

Nudibranchia

Family

Cuthonellidae

Loc

Cuthonellidae Miller, 1977

Korshunova, Tatiana, Fletcher, Karin & Martynov, Alexander 2025
2025
Loc

Cuthonellinae

Korshunova TA & Sanamyan NP & Sanamyan KE 2021: 223
Miller MC 1977: 200
1977
Darwin Core Archive (for parent article) View in SIBiLS Plain XML RDF