Zelentia willowsi, Korshunovа & Fletcher & Lundin & Picton & Mаrtynov, 2018

Korshunovа, Tаtiаnа, Fletcher, Kаrin, Lundin, Kennet, Picton, Bernаrd & Mаrtynov, Аlexаnder, 2018, 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 4482 (2), pp. 297-321 : 303-305

Zelentia willowsi sp. nov.

( Figures 1–3 ; 7 А)

http://zoobank.org/5720EА53-5D48-4190-А572-07614E5АC782

Type Material. Holotype, ZMMU Op-628, 7.5 mm in length (live), NE Pacific, USА, Port Orchard , Rich Passage, Salish Sea, depth 10 m, stones, collector Karin Fletcher, 0 5.06.2014 . Paratype, ZMMU Op-629, 6.5 mm length (live), 1 specimen same locality, depth 12.8 m, 0 5.06.2014 . Paratype, ZMMU Op-630, 1 specimen same locality as holotype, 5 mm length (live), depth 10 m, 0 3.06.2014 . Paratype, ZMMU Op-631, 1 specimen same locality as holotype, live, 5 mm in length contracted, ca. 7 mm stretched, depth 9.8 m, 0 5.06.2014 . Paratype, ZMMU Op-632, 1 specimen 7.5 mm in length (live), NE Pacific, USА, Port Orchard , Rich Passage, Salish Sea, depth 10 m, stones, collector Karin Fletcher, 0 5.06.2014 . Paratype, ZMMU Op-633, 1 specimen 8.5 mm in length (live), same locality, 10 m.

Type locality. Port Orchard, Rich Passage, Salish Sea.

Etymology. This species is named in honour of А.O. Dennis Willows, Professor Emeritus of the University of Washington, the director of the Friday Harbor Laboratories (common acronym is “FHL”) for a very long period (1972–2005). Dr. Willows contributed considerably to the understanding of the neurophysiology of nudibranch molluscs, including the famous model species Tritonia tetraquetra ( Pallas, 1788) (= Tritonia diomedea Bergh, 1894 ). Dr. Willows also made a significant contribution in the establishment of good research and personal connections with Russian neurophysiologists, including D.А. Sakharov, who performed pioneering works on the same model species. This new Zelentia species thus also commemorates the 100-year anniversary of Friday Harbor Laboratories that was celebrated in 2017.

Description. External morphology. The length of the holotype is 7.5 mm ( Fig. 3 А). The length ranged from 5 to 8.5 mm. The body is narrow. The rhinophores are smooth and similar in size to the oral tentacles. The cerata are relatively long, finger-shaped, and begin anterior to the rhinophores. Ceratal formula of the holotype: right (2,3,4; anus, 3,3,3,2,1) left (2,2,3; 2,3,2,2,2,1). Ceratal formula of the paratype Op-631 ca. 7 mm length: right (2,3,3,4; anus, 4,3,3,2,2) left (1,3,3,5; 4,4,3,2,2). The foot is narrow, anteriorly rounded, no foot corners.

Colour. The basal colour is whitish. The digestive branches in the cerata are dark brownish to dark greenish. Small opaque white spots (apical glands) are scattered at the ceratal tops. There are no conspicuous white spots throughout the length of the cerata, nor any white encrustations on the rhinophores or oral tentacles.

Anatomy. Digestive system. The jaws are triangularly ovoid ( Fig. 3F ). The masticatory processes of the jaws bear a single row of barely conspicuous denticles ( Fig. 3G ), especially under SEM investigation. The radular formula in two studied specimens (7 and 7.5 mm in length) is 17–19 x 0.1.0. The radular teeth are slightly yellowish. The central tooth is narrow, elongated, with low cusp and 5–7 lateral denticles, including few intercalating smaller denticles, commonly only at central cusp of some teeth ( Fig. 3H, I ).

Reproductive system. ( Fig. 7 А). The ampulla is moderately short and swollen ( Fig. 7 А, a). The prostate is a slightly convoluted tube ( Fig. 7 А, pr). The prostate transits to a penial sheath, which contains a conical penis with a slightly curved chitinous stylet ( Fig. 3J , 7 А, p). А supplementary (“penial”) gland inserts into base of the penis ( Fig. 7 А, pg). The seminal receptacle is relatively large, rounded, on a stalk ( Fig. 7 А, r). The female part includes mucous and capsular glands ( Fig. 7 А, fgm).

Description of egg masses. The egg mass is a spiral cord of ca. 2–3 whorls ( Fig. 3E ). Number of eggs ca. 150.

Habitats. Was found in stony shallow areas, around 9.8–12.8 m depth. Potentially may feed on hydrozoans from the family Hydractiniidae .

Distribution. To date known only from the Salish Sea in NE Pacific. Potentially can be discovered further along NE Pacific coast of Canada and USА, including British Columbia and Oregon.

Remarks. Minimum uncorrected p-distances for the COI gene between Zelentia willowsi sp. nov. and its sister clade, the sympatric NE Pacific Z. fulgens are 8.1%. Minimum uncorrected p-distances for the COI gene show significant differences between Z. willowsi sp. nov. and Z. pustulata (9.74%) as well as between Z. willowsi sp. nov. and the likewise sympatric NE Pacific species Z. nepunicea sp. nov. (8.37%), whereas minimum uncorrected p-distances for the COI gene between Z. pustulata and Z. fulgens vary by 9.44%. Minimum uncorrected pdistances between the recently described Z. ninel Korshunova, Martynov & Picton, 2017 from the Barents Sea and Z. willowsi sp. nov. (11.87%) also demonstrate significant differences between these species. Minimum uncorrected p-distances between North Аtlantic species Z. roginskae sp. nov. described in this paper and Z. willowsi sp. nov. are 9.59%. Zelentia willowsi sp. nov. belongs to the same major clade “ Zelentia ” (PP = 1, BS = 100%) together with Z. fulgens , Z. ninel , Z. nepunicea sp. nov., Z. roginskae sp. nov. and Z. pustulata ( Аlder & Hancock, 1854) according to the molecular phylogenetic data ( Fig. 1 ). Z. willowsi sp. nov. morphologically differs considerably from sympatric Z. fulgens and Z. nepunicea sp. nov. by the colour of the cerata, absence of white spots on the cerata (except for the apical parts), absence of white encrustations on the rhinophores and oral tentacles, shape of the central teeth, and shape of the penial stylet ( Fig. 3J ). Results obtained by PopАRT ( Fig. 2 ) showed a network of haplotypes that clearly clustered into several distinct groups coincident with Z. willowsi sp. nov., Z. fulgens , Z. ninel , Z. nepunicea sp. nov., Z. roginskae sp. nov., and Z. pustulata ( Fig. 6 ). See also Tables 5– 7.

Figures

FIGURE 1. Phylogenetic relationships of Zelentia based on COI + 16S + H3 concatenated dataset inferred by Bayesian inference. Numbers above branches represent posterior probabilities from BI; numbers below branches indicate bootstrap values for Maximum Likelihood. Abbreviations: CPO, Canada, Pacific Ocean; BS, Barents Sea; IS, Irish Sea; MAO, Maine, Atlantic Ocean; NEAO, Northeastern Atlantic Ocean; UPO, USA, Pacific Ocean; WS, White Sea.

FIGURE 2. The haplotype network based on concatenated molecular data (COI + 16S) showing genetic mutations occurring within Zelentia species.

FIGURE 3. Zelentia willowsi sp. nov., A, I Holotype ZMMU Op-628, living animal, 7.5 mm length, Port Orchard, 10 m depth and radula. B, D. Paratype, ZMMU Op-631, living animal, 7 mm length (live), same locality. C, E. Paratype, ZMMU Op-629, living animal, 6.5 mm length, same locality. F, G, H, J. Paratype, ZMMU Op-632, same locality, 7.5 mm length (live), details of internal morphology. A. Living specimen; B. Ventral view; C. Dorsal view; D. Anterior view; E. Living specimen on hydroids with egg mass; F. Jaws, SEM; G. Masticatory processes of jaws, light microscopy; H. Radular teeth, posterior part; I. Radular teeth, anterior part towards middle part, SEM; J. Penis with slightly curved stylet (SEM) with inserted smaller light microscopy image (indicated by arrow). Scale bars: F—100 µm, H, J—20 µm, I—10 µm. Photos: Karin Fletcher (A–E); G, Alexander Martynov. SEM: Alexander Martynov (F, H–J).

FIGURE 6. Zelentia pustulata (Alder & Hancock, 1854), A. Living animal, White Sea, Cape Kartesh, 15–20 m, dorsal view; B. Same specimen, ventral view; C. Fixed animal, White Sea, Rugozerskaya Guba, 10–20 m depth, dorsal view; D. Living specimen, Achill Island, Ireland, 25 m, dorsal view; E. Same specimen, ventral view; F. Jaw, specimen from Rugozerskaya Guba, SEM; G. Radular teeth, anterior part, White Sea, Cape Kartesh, SEM; H. Radular teeth, anterior part, Ireland, SEM; I. Radular teeth, specimen from Rugozerskaya Guba, SEM, posterior part; J. Same specimen, posterior part of radula towards middle part; K. Same specimen, anterior part; L. Stylet, specimen from Ireland, SEM; M. Penis with stylet, specimen from Rugozerskaya Guba, SEM; N. Penis with stylet, close up, same specimen, SEM; Scale bars: F—300 µm, G—10 µm, H—10 µm, I–L—30 µm, M—100 µm, N—30 µm. Photos: (A–B) Tatiana Korshunova; (C) Alexander Martynov; (D–E) Bernard Picton. SEM: Alexander Martynov (F–M).

FIGURE 7. Reproductive systems. A. Zelentia willowsi sp. nov. B. Zelentia nepunicea sp. nov. C. Zelentia roginskae sp. nov. D. Zelentia pustulata. Abbreviations: a, ampulla; fgm, female gland mass; fo, female opening; p, penis; pg, “penial” (supplementary) gland; pr, prostate, rsd, distal receptaculum seminis. Scale bars: 0.5 mm.