Coelorinchus inventionis Prokofiev & Iwamoto & Mishin 2022, sp. nov.
Creators: name: Prokofiev, Artem M.
name: Iwamoto, Tomio
name: Mishin, Alexey V.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Gadiformes
Macrouridae
Coelorinchus
Coelorinchus inventionis

description: Coelorinchus inventionis sp. nov.
Figs. 1, 2A–D, 3–6, 8; Tables 1–3, 7
Caelorinchus vityazae (in part): Iwamoto et al. 2004: 192 (Discovery Tablemount, “Bank Gulf”).
Holotype. IOM M.189–001, 41 mm HL, 181+ mm TL (Fig. 1), southeastern Atlantic Ocean, Discovery Tablemount, 42°30.5´S, 01°33´W, 400–445 m, bottom trawl, FRV Professor Mesyatsev, cruise 8, trawl 155, 10 December 1979, S. V. Busakhin (VNIRO).
Paratypes. IOM M.189–002 to 008, 7(30–47 mm HL, 137+–202+ mm TL), the same data as for the holotype. ZIN 48772, paratypes of C. vityazae, 11 (51–70 mm HL, 212+–314+ mm TL), Gough Bank [erroneously cited as “Bank Gulf” in Iwamoto et al. (2004: 193)], 39°37´S, 06°38.2´W, 190–335 m, FRV Evrika, cruise 3, AtlantNIRO.
Note. Three specimens from the Discovery Tablemount (ZMMGU P-15650, 39–44 mm HL) listed as the paratypes of C. vityazae in the original description of that species (Iwamoto et al. 2004: 193) were not found. According to the superscription on an empty jar in IOM these specimens were sent to CAS but we were unable to find them.
Diagnosis. A species of the Coelorinchus fasciatus group with snout moderately short, 27.7–33.9 % (mean 31.6 %) HL, tipped with short, weakly tripartite terminal scute, broader than long, with medial prong only slightly longer than lateral ones, not pointed (Fig. 2A–C); underside of head completely scaleless; lips uniformly thick, unpigmented (Fig. 2D); no enlarged predorsal scales; flank scales with 6–12 parallel rows of spinules (number increasing with growth); pectoral-fin rays, modally i+17 or i+18; 12–17 pyloric caeca; small oval dermal window of light organ in front of anus, one-third to one-half of pelvic-anal length; up to eight faint saddle marks on body, anal-fin rays darkened distally.
Description. General features of fish seen in Fig. 1. Counts: first dorsal-fin rays, II+9 [II+9–11, usually II+9]; pectoral-fin rays, i+18 [i+17–20, frequency shown in Table 1]; pelvic-fin rays, 7; gill-rakers (inner) on 1 st arch, 8 [8–9, usually 8]; gill-rakers on 2 nd arch, 8 [6–9, usually 8] (outer) / 7 [7–10, usually 7 or 8] (inner); transverse scale rows below origin of first dorsal fin, 4.5 [4.0–5.5, usually 4.5 or 5.0]; ditto, below midbase of first dorsal fin, 3.5 [3.5–4.5, usually 3.5 or 4.0]; ditto, below origin of second dorsal fin, 4.0 [4.0–4.5]; ditto, between origin of anal fin and lateral line, 13 [10(?),11–13]; lateral-line scales before origin of second dorsal fin, 15 [13–16]; pyloric caeca, 12–17 (n = 3). Measurements shown in Tables 2 and 3. Head 4.4 [4.0–4.6] times in TL. Snout short, 3.2 [3.0–3.6] times in HL, 1.1 [1.1–1.4] times in orbit, broadly triangular in dorsal view, with sides strongly convergent along lateral nasal ridges; dorsal contour of snout gently sloping from level of anterior margin of orbit towards tip (Fig. 2A, B). Snout tipped with short and broad terminal scute, 5.7 [5.6–7.4 (IOM M.189) or 6.3–9.5 (ZIN 48772)] times in snout length, armed with strong, straight to somewhat recurved denticles; medial prong of terminal scute only slightly longer than lateral ones, not pointed (Fig. 2C). Postorbital length of head 0.9 [0.8–1.2, usually 0.9–1.0] times longer than snout. Anterolateral margins of snout not completely supported by bone. Orbit elliptical, 2.6 [2.5–2.9] times in HL, 1.3 [1.1–1.4] times exceeding postorbital length of head. Suborbital shelf sharply angulated; shelf depth 1.7 [1.5–2.2] times in suborbital depth. Lateral nasal ridge 3.8 [3.4–4.8, usually 3.8–4.4] times shorter than suborbital ridge. Mouth moderately large, posterior tip of maxilla ending at level of posterior border of pupil to mid-way between posterior border of pupil and mid-orbit. Jaw teeth uniformly short, needle-like, densely clustered in bands that are broadened toward symphysis, outermost teeth not enlarged; teeth on premaxilla larger than those on dentary; premaxillary teeth fully hidden in mass of upper lip; tips of dentary teeth expressed through lower-lip margin. Premaxillary tooth band 1.8 [1.5–2.0, usually 1.8 or more] times shorter than length of rictus; dentary tooth band reaching rictus. Lips uniformly thick, finely papillose along whole length; lower lip almost as thick as upper lip (Fig. 2D). Preopercle margin inclined backward at about 50°, with posteroventral lobe somewhat tapered, rounded at tip; subopercle forming a ventral projection. Chin barbel slender, 3.5 [3.1–5.2 (usually 3.5–4.4) (IOM M.189) or 2.5–4.2 (usually 3.0–3.4) (ZIN 48772)] times in orbit.
First dorsal-fin base 1.2 [1.4–1.6 (IOM M.189) or 0.8–1.6 (ZIN 48772)] times longer than interdorsal space; second dorsal-fin spine 1.4 [1.5–2.0] times in HL, not extended into filament. Rays of second dorsal fin much shorter and thinner than those of anal fin. Pectoral fin narrow based, reaching slightly behind anal-fin origin. Pelvic fins originate at vertical of pectoral-fin origin or slightly behind, on same vertical with first dorsal-fin origin or slightly before it. Outermost pelvic-fin ray filamentous, ending beyond anal-fin origin. Anus near anal-fin origin. Light organ externally evident as elongate-oval scaleless fossa in front of anus, 2.9 [2.1, 2.7–3.9 (IOM M.189) or 1.3–2.1 (ZIN 48772)] times in pelvic-anal length (Fig. 3). Swimbladder bipartite anteriorly.
Flank scales rather loosely attached, bearing 6–12 parallel rows of small aciculate adpressed spinules (number of rows increased with growth); spinules in rows uniform in size and shape, separated from each other; all rows complete; medial row of spinules not enlarged (Fig. 4). Tips of posteriormost spinules in rows extending well behind hind margin of scale. Spinules on scales from isthmus are smaller and arranged in diverging rows. Predorsal scales with larger and more erect spinules arranged in 5–8 (usually 6 or 7) diverging rows, medial row sometimes very slightly enlarged. Scales on top of head with 2–7 (usually 3 to 5; when more than 3, outermost rows usually incomplete) diverging rows of sharp erect spinules, mostly slightly increasing in size in posterior direction per row. Supraoccipital and postoccipital scutes not discernible. Spinulation on cheek and opercle scales in strongly diverging rows (up to 9 rows on opercle, up to 7 rows on cheek), spinules per row minute and depressed. Dorsal surface of snout lacking scaleless areas; nasal fossa scaled except along anterior margin (but sometimes few scales can be present in front of anterior nostril), in smallest specimens (HL 30–34 mm) a narrow bare strip also present below anterior nostril; underside of head scaleless. Suborbital shelf formed by small squarish to somewhat dorsoventrally extended scutes, a row of small spinulose scales between scutes of suborbital ridge and lower margin of orbit; scutes of medial nasal ridge 8 [7–9, usually 8] in number (including terminal scute), with radiating rows of spinules.
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Body color in preservative pale with brownish markings; margins of scale pockets densely pigmented. Up to eight faint transverse bars on dorsum. First dorsal fin dusky; anal-fin rays pigmented by brownish melanophores, usually more concentrated distally; paired fins slightly infuscated with fin-rays peppered by melanophores. Orbit encircled by brown. Free neuromasts on head not pigmented. Underside of head finely peppered by melanophores, almost uniform in density everywhere but becoming larger posterially. Lips, gums and oral cavity pale, unpigmented; inside of gill cover brownish-black; peritoneum dark-brownish; stomach uniformly dusky, intestine and pyloric caeca unpigmented.
Etymology. Species is named from its type locality, Discovery Tablemount, in turn named in honour of the famous British oceanographic vessel Discovery (inventio (Latin) means discovery).
Distribution. Currently known from two seamounts in the southeastern Atlantic Ocean: Discovery Tablemount and Gough Bank (Fig. 5). Depth range about 300(?)– 445 m.
Remarks. Two available samples of C. inventionis come from different localities and are considerably different in size. The specimens collected on the Discovery Tablemount (IOM M.189) are much smaller than those from the Gough Bank (ZIN 48772) (30–47, vs. 51–70 mm HL). The difference in number of spinule rows on flank scales between the Discovery and Gough specimens (up to 8 vs. up to 12) clearly represents ontogenetic variation. Although largely overlapping, many measurements show differences in mean values, particularly the eye is larger, the suborbital depth is smaller, the isthmus-anal and interdorsal distances are shorter in the smaller specimens, etc. (Table 3). Many of these differences may also be a subject of growth changes, and the smaller and larger specimens of C. vityazae show similar trends (Table 4). However, we found a drastic difference in the length of the light organ between specimens from the Discovery and from the Gough seamounts although there was slight overlap in the outer limits: the light organ is considerably longer in Gough specimens (14.9–28.6, mean 24.6, vs. 10.5–15.2, mean 13.0) (Fig. 3; Table 3). This difference cannot be explained by growth; furthermore, in both the Discovery and Gough populations the length of the light organ decreases with growth, while in C. vityazae this parameter shows a slight trend towards increasing with growth (Fig. 6A). It is possible that this difference reflects an initial stage of speciation within C. inventionis.
description: Published as part of Prokofiev, Artem M., Iwamoto, Tomio & Mishin, Alexey V., 2022, A new species of the grenadier genus Coelorinchus from the seamounts in the southeastern Atlantic Ocean, with redefinition of C. vityazae (Teleostei: Gadiformes: Macrouridae), pp. 130-148 in Zootaxa 5213 (2) on pages 131-136, DOI: 10.11646/zootaxa.5213.2.2, http://zenodo.org/record/7354190