Lycenchelys renatae, Thiel & Knebelsberger & Chernova & Eidus, 2025

Lycenchelys renatae sp. nov.

Common name: Renate´s eelpout

( Figures 1 View FIGURE 1 & 4–6 View FIGURE 4 View FIGURE 5 View FIGURE 6 ; Table 2 View TABLE 2 )

Holotype. ZMH 26281 View Materials , female, 196 mm SL, voucher specimen code MT 10111 , RV ‘Akademik M.A. Lavrentyev’, AGT haul 9–10, Bussol Strait, southern of Simushir Island , Agassiz trawl, 46˚15.7΄N; 152˚03.1΄E, 3517 m depth, 27 July 2015.

Paratypes. Three specimens; ZMH 26282 View Materials , female, 158 mm SL, voucher specimen code MT 10109 , RV ‘Akademik M.A. Lavrentyev’, AGT haul 9-9, Bussol Strait, southern of Simushir Island , Agassiz trawl, 46˚15.7΄N; 152˚03.1΄E, 3580 m depth, 27 July 2015. ZMH 26283 View Materials , male, 161 mm SL, voucher specimen code MT 10108 , same collection data as ZMH 26282. ZMH 26284 View Materials , female, 183 mm SL, voucher specimen code MT 10110 , same collection data as holotype .

Diagnosis. A species of Lycenchelys from the Western North Pacific, distinguished from its congeners by the following combination of characters: vertebrae 26–27+ 99–103 = 125–130; suborbital pores 6–9; postorbital pores 1–4; interorbital pores 0–1; occipital pores absent; preoperculomandibular pores 3–4 + 5; dorsal-fin rays 115–122, 1–3 free pterygiophores at the beginning of dorsal fin; anal-fin rays 102–106; pelvic-fin rays two; pectoral-fin rays 16–17; lateral line mediolateral.

Description. Counts and measurements are provided in Table 2 View TABLE 2 . Body relatively long ( Fig. 4 View FIGURE 4 ), its cross section almost round at nape, elliptical at both abdominal and caudal regions and compressed laterally near tail. Head moderately long, ovoid, flat top, dorsal profile evenly declined from behind eye to steeply sloping snout tip; nape somewhat hunched ( Fig. 5 View FIGURE 5 ). Eye ovoid, entering dorsal profile of head. Interorbital space convex. Gill slit extending ventrally to level of lower pectoral base. Opercular flap at upper end of gill slit well developed.

Mouth inferior, upper jaw extending to middle of eye. Nostril tube not or just barely reaching upper lip when depressed forward. Snout rounded and somewhat triangular in dorsal profile of three largest specimens. Labial lobe of lower jaw developed. Teeth conical, relatively large on jaws; upper jaw with single continuous row, anteriormost teeth somewhat larger than posterior teeth, additional shorter row with 4–7 smaller teeth behind anteriormost teeth; lower jaw with 2–3 irregular rows anteriorly and single row posteriorly; 6–8 small and conical vomerine teeth irregularly arranged; palatine teeth absent.

Small but clearly identifiable head pores. Two nasal pores, anterior one set just in front of nostril tube, other situated dorsoposteriorly ( Fig. 5 View FIGURE 5 ). Suborbital pores 6–9, 6–7 pores arising from ventral ramus of bone chain under eye, and if present, the eighth and ninth pore from ascending ramus behind eye. Postorbital pores 1–4. Mandibular pores on lower jaw 5, 4 arising from dentary, one from anguloarticular. Preopercular pores 3–4. Interorbital pores 0–1. Occipital pores absent. Body lateral line mediolateral, poorly developed, only detectable from above upper end of gill opening to end of pectoral fin.

Dorsal fin origin above anterior third of pectoral fin; 1–3 free pterygiophores at beginning of dorsal fin; lower tip of pterygiophore of first dorsal-fin ray between tips of neural spines of fourth and fifth or fifth and sixth vertebrae. Pterygiophore of last dorsal ray associated with fourth preural vertebra. Anal fin origin associated with first caudal vertebra or ultimate precaudal vertebra. 4 pterygiophores of anal fin inserted anteriorly to haemal spine of first caudal vertebrae or ultimate precaudal vertebra; pterygiophore of last anal ray associated with second preural vertebra. Pectoral fin origin at body midline. Ray tips of pectoral fin exserted, middle and lower ones significantly more than upper ones. Pelvic fin small, its length shorter than snout. Caudal fin with 2 epural, 4 upper and 3 lower hypural rays.

Scales absent on head, nape, thorax, pelvic fin, pectoral fin, base and its axil, and anteriorly on dorsal and anal fins. Scales small and cycloid, present on body, on abdomen not reaching line connecting pectoral bases ( Fig. 5 View FIGURE 5 ). Scales also present on tail and posterior parts of dorsal and anal fins, extending to about two third of their height. Belly scaled; extending anteriorly not quite to the basis of pectoral fin ( Fig. 5 View FIGURE 5 ).

Gill rakers short, those on upper limb narrower and more pointed than those on lower limb. Pseudobranch filaments absent. Pyloric caeca not developed.

Fresh color ( Fig. 4 View FIGURE 4 ). Head and pectoral fin light brown, head pores lighter. Body light beige colored posteriorly from head. Eyes black.

Preserved color ( Fig. 4 View FIGURE 4 & 5 View FIGURE 5 ). Specimens faded in comparison to fresh color. Head, pectoral fin and body leight beige colored. Eyes black. Peritoneum and lining of orobranchial cavity brown.

Etymology. The new species is named after the first name of Renate Thiel, the wife of the first author, in recognition of her 23 years of outstanding data processing work in the context of ichthyology research projects.

Distribution. Lycenchelys renatae sp. nov. is known only from two very closely spaced AGT hauls performed at station 9 of SokhoBio expedition at the western slope of the upper margin of the Kuril-Kamchatka Trench.

Environmental conditions. Same as for L. delanglei sp. nov.

Feeding ecology. As in the case of L. delanglei sp. nov., it is highly probable that the mussel shells seen on the radiographs ( Fig. 6 View FIGURE 6 ) belong to Yoldiella sp. Three out of the four type specimens of L. renatae sp. nov. contained one to two shells of Yoldiella sp. in their stomachs, therefore this species is part of the prey spectrum of L. renatae sp. nov. in this habitat.

DNA barcode. For the holotype ZMH 26281 View Materials and the three paratypes ZMH 26282–84 View Materials of Lycenchelys renatae sp. nov., full COI barcodes (652 bp) were obtained and uploaded to GenBank (https://www.ncbi.nlm. nih.gov/genbank/) with the following accessions: ZMH 26281 View Materials : PQ585660, ZMH 26282 View Materials : PQ585661, ZMH 26283 View Materials : PQ585662, ZMH 26284 View Materials : PQ585663. Tissue samples and DNA isolates were stored in the DNA and tissue collection of the DZMB.

The four analysed types share the same mitochondrial haplotype and have a sequence similarity of 97.39% with haplotypes of L. delanglei sp. nov.. The comparisons of the haplotype sequence of L. renatae sp. nov. with all published DNA sequences on NCBI using MegaBLSAT algorithm showed the closest matches with two specimens of Lycenchelys jordani with sequence similarities of 98.62 (GeneBank accession: FJ164744.1) and 98.47% (GeneBank accession: FJ164740.1), followed by four specimens of Lycenchelys lenzeni Thiel, Knebelsberger & Eidus, 2018 (GeneBank accessions: MG650294.1, MG650295.1, MG650296.1, MG650297.1) with a sequence similarity of 97.24% and eight specimens of Lycenchelys aratrirostris Andriashev & Permitin, 1968 (sequence similarities 96.29–96.60%; GeneBank accessions: HQ713029.1, HQ713030.1, HQ713032.1, HQ713033.1, HQ713034.1, HQ713035.1, HQ713036.1, HQ713037.1).

Comparative notes. Lycenchelys renatae sp. nov. has been compared with 25 other Lycenchelys species known from the Western North Pacific ( Table 3 View TABLE 3 ). The most significant differences are summarized below.

The new species has fewer total vertebrae (125–130 total vertebrae) than the following five species (vertebrae counts for each species in parentheses): Lycenchelys albeola Andriashev, 1958 (133), L. fedorovi Anderson & Balanov, 2000 (132–139), L. maculata Toyoshima, 1985 (136–144), L. makushok Fedorov & Andriashev, 1993 (132–139) and L. rosea Toyoshima, 1985 (136–137) and higher total vertebrae than the following ten species: Lycenchelys delanglei sp. nov. (120–121), L. alta Toyoshima, 1985 (88), L. aurantiaca Shinohara & Matsuura, 1998 (85–89), L. melanostomias Toyoshima, 1983 (117–123), L. ratmanovi Andriashev, 1995 (110–115), L. ryukyuensis Shinohara & Anderson, 2007 (118–124), L. squamosa, Toyoshima, 1983 (91–95), L. tohokuensis, Anderson & Imamura, 2002 (116–119), L. uschakovi Andriashev, 1958 (122) and L. vitiazi Andriashev, 1955 (114–116). Only the following ten species of Lycenchelys from the Western North Pacific overlap with L. renatae sp. nov. in vertebral count (number of compared characters for each of the following species in parentheses): L. albomaculata Toyshima, 1983 (122– 128), L. camchatica (Gilbert & Burke, 1912) (118–125), L. hippopotamus Schmidt, 1950 (128–138), L. lenzeni Thiel, Knebelsberger & Eidus, 2018 (126–130), L. micropora Andriashev, 1955 (123–135), L. parini Fedorov, 1995 (125), L. plicifera Andriashev, 1955 (122–126), L. rassi Andriashev, 1955 (122–134), L. remissaria Fedorov, 1995 (124–130) and L. volki Andriashev, 1955 (126). However, the new species differs from L. albomaculata in having more precaudal vertebrae (26–27 vs. 22–25) and free pterygiophores at the beginning of dorsal fin (1–3 vs. 0) as well as fewer pelvic-fin rays (2 vs. 3) and occipital pores (0 vs. 3). The new species differs from L. camchatica in having more precaudal vertebrae (26–27 vs. 21–24), free pterygiophores (1–3 vs. 0), pectoral-fin rays (16–17 vs. 12–15) as well as a higher number of pelvic-fin rays (3 vs. 2). Lycenchelys renatae sp. nov. has a higher number of free pterygiophores (1–3 vs. 0) and another type of lateral line (mediolateral vs. double) than L. lenzeni . The new species has more precaudal vertebrae (26–27 vs. 23–24), more pectoral-fin rays (16–17 vs. 13–15), less caudal vertebrae (99–103 vs. 105–115), less dorsal-fin rays (115–122 vs. 124–133), less anal-fin rays (102–106 vs. 111– 120) and less occipital pores (0 vs. 2) than L. hippopotamus . Lycenchelys renatae sp. nov. has a higher number of free pterygiophores (1–3 vs. 0) and a lower number of pelvic-fin rays (2 vs. 3) than L. micropora . The new species has a higher number of free pterygiophores (1–3 vs. 0) and in addition a higher number of precaudal vertebrae (26– 27 vs. 24), but a lower number of pelvic-fin rays (2 vs. 3) and occipital pores (0 vs. 2) than L. parini . Lycenchelys renatae sp. nov. has lower numbers of free pterygiophores (1–3 vs. 6–7) and precaudal vertebrae (26–27 vs. 28–30) as well as a higher number of caudal vertebrae (99–103 vs. 92–98) than L. plicifera . The new species differs from L. rassi in having more precaudal vertebrae (26–27 vs. 23–25), free pterygiophores (1–3 vs. 0) as well as less occipital pores (0 vs. 2). Lycenchelys renatae sp. nov. has more free pterygiophores (1–3 vs. 0) and less pelvic-fin rays (2 vs. 3) than L. remissaria and has less precaudal vertebrae (26–27 vs. 30) and free pterygiophores at the beginning of the dorsal fin (1–3 vs. 7) as well as more caudal vertebrae (99–103 vs. 96) and dorsal-fin rays (115–122 vs. 113) than L. volki .

The analysis distinguished L. renatae from other eelpout species using DNA barcoding. There is relatively high sequence similarity with two species from the Western North Pacific ( L. lenzeni , L. delanglei sp. nov.; Table 3 View TABLE 3 ) and with L. jordani from the Eastern North Pacific (less than 3% different), as well as with L. aratrirostris from the Southern Ocean. The morphological differences between L. lenzeni and L. renatae sp. nov. have already been described above.

Lycenchelys renatae sp. nov. differs from the sympatric L. delanglei sp. nov. by a higher number of total vertebrae (125–130 vs. 120–121), caudal vertebrae (99–103 vs. 91–93) and anal-fin rays (102–106 vs. 96–98), as well as lower number of precaudal vertebrae (26–27 vs. 28–29) and by the presence of a lateral line (versus its absence) and fewer suborbital pores (6–9 versus 10–12). The new species has a lower number of pelvic-fin rays (2 vs. 3), a higher number of free pterygiophores at the beginning of dorsal fin (1–3 vs. 0) and another type of the lateral line (mediolateral vs. double) than L. jordani . Lycenchelys renatae sp. nov. differs from the L. aratrirostris in having higher numbers of dorsal-fin rays (115–122 vs. 97–107), anal-fin rays (102–106 vs. 79–89), total vertebrae (125–130 vs. 101–110) and a lower number of pelvic-fin rays (2 vs. 3).