Icelus crassus Andriashev, 1937

Chernova, Natalia, Kai, Yoshiaki & Zorina, Anna, 2025, Validation of Icelus crassus Andriashev (Cottiformes: Cottidae), described from the Sea of Okhotsk, Zootaxa 5569 (2), pp. 282-298 : 285-296

Icelus crassus Andriashev, 1937 —Stocky Sculpin ( Figs. 2–7 )

Icelus uncinalis (non Gilbert & Burke, 1912): Schmidt 1927: 3 (part: Penzhina Bay [ZIN 21910], northeast of Sakhalin Island [ZIN 21905]). Soldatov & Lindberg 1930: 176 (part: Sea of Okhotsk).

Icelus ochotensis (non Schmidt, 1927): Schmidt 1927: 4, figs. 1, 2 (part: figures [ZIN 21900]).

Icelus uncinalis crassus Andriashev, 1937: 265 , pl. 5, fig. 2 (dorsal-fin rays VIII–X 19–21, anal-fin rays 14–16 and pectoral-fin rays 18–19, lateral-line scales 41–43, dorsal-row scales 23–28 based on 11 spec.; % head length in TL 29.4–30.9, head height 15.9–18.1, caudal-peduncle length 15.7–17.2; caudal-peduncle height 25.0–29.4% of caudal-peduncle length; % eye diameter in head length 30.0–33.0, nuchal-tubercle length 4.8–6.6, interorbital width 5.4–6.9, based on 7 spec. TL 73–131 mm; % urogenital-papilla length in head length 24.1–32.2 from spec. ca. TL 60 mm; Penzhina Bay, northeast of Sakhalin Island, Sea of Okhotsk ; depth to 115 m, temperature -0.7°С).

Icelus uncinalis crassus : Schmidt 1950: 134 (after Andriashev 1937).

Holotype (confirmed herein): ZIN 21900, adult male TL 106 mm, SL 88 mm, western part of Sea of Okhotsk , 57°36′ N, 140°34′ E, depth 97 m, 14 Aug. 1918; st. 9, silt substrate, Hydrographic Expedition of the Pacific Ocean, collector G.R. Meder.

Paratypes (7 spec., Sea of Okhotsk ): ZIN 21905 (3), F, TL 68 mm and 2 M, 98 and 97 mm, 54°14’ N, 143°45’ E [ northeast of Sakhalin Island ], depth 146 m, 12 Jul.1918, st. I, stone and sand substrate, Hydrographic Expedition of the Pacific Ocean, collector G.R. Meder ; ZIN 21910 (2), F, TL 94 and 107 mm, Penzhina Bay , 61°15′ N, 162°56′ E, 23 Jul. 1915, hydrographic vessel “Okhotsk,” Hydrographic Expedition of the Pacific Ocean; ZIN 24468 (1), F, TL 132 mm, Sakhalin Island, Cape Elizabeth , 54°36′ N, 143°48′ E, depth 165 m, 8 Sep. 1932; fishing trawler “Ara,” st. 27, silt and sand substrate; bottom temperature 2.15°С; collector M.N. Krivobok.

CAS-SU (ICH) 40933 (1, from ZIN 21905), M, photo available ( Catania & Fong 2024).

Additional material (12 spec. from 10 st.). Sea of Okhotsk—vicinity of Sakhalin Island: ZIN 44541 (3), 2 F, TL 172 and 100 mm, M, 127 mm, 14 Jul. 1978, depth 240 m, fishing trawler “Poseidon,” st. 4, otter trawl, stone substrate, collector V.D. Tabunkov; ZIN 50228 (1), F, SL 138 mm, 51°40′ N, 144°17.7′ E, 19 Aug. 1991, 170 m, fishing trawler “Shursha,” bottom temperature 0°C, collector I. Mukhametov. North of Hokkaido: FAKU 144694 (1), M, TL 51.9 mm, off Abashiri , 170 m; FAKU 201397 (1), F, TL 97.5 mm, 45°0′42″ N 143°56′35″ E, 202 m; HUMZ 124321 (1), F, TL 152.7 mm, off Kitami , 159 m; HUMZ 125962 (1), F, TL 163.6 mm, off Kitami , 208 m; HUMZ 125963 (1), F, TL 190.5 mm, off Kitami , 208 m; HUMZ 125964 (1), F, TL 160.4 mm, off Kitami , 208 m; HUMZ 232686 (1), M, TL 72.3 mm, off Abashiri , 327 m. Sea of Japan —ZIN 25281 (1), F, TL 125 mm, 46°26′ N, 138°35′ E [Strait of Tartary, south], depth 124 m, 9 Mar. 1913, security cruiser “Lieutenant Dydymov,” st. 432, Far Eastern Expedition of the Department of Agriculture .

Etymology. From the Latin “ crassus ” (adjective), meaning heavyset or stocky.

Diagnosis. Icelus crassus is a member of “ I. bicornis ” group, characterized by absence of suborbital and lacrimal spines, additional body scale rows (except for dorsal and lateral-line rows), and lack of single sharp spines on dorsal-row scales. Icelus crassus is further distinguished by absence of parietal spines; nuchal spines tubercle-like, covered by skin; supraorbital cirri broadening from narrow base, distally dissected; dorsal scale row incomplete does not reach head at distance equal to eye diameter, its first scale above 3rd–6th lateral-line scales; precaudal lateral-line scales finely serrated below canal pore, with up to 5 or 6 spinules; posteriormost lateral-line scale usually on caudal-fin base; vertebrae 38–41, dorsal-fin rays VIII–IX 18–21, anal-fin rays 15 or 16, pectoral-fin rays 17–19; 25–31 scales in dorsal row, 40–43 in lateral line, axillary scales 10–18; urogenital papilla in males cylindrical, with short claw-like terminal appendage.

Redescription of holotype. Body dorsally humpback under dorsal-fin origin, depth 3.7 times in SL, preanal portion greater than half body length (53.4% SL). Head massive, 2.8 in SL, barely compressed (depth at occiput 66.7% head length), snout 1.1 times longer than eye diameter, rounded in dorsal view; eye 3.1 times in head length; supraorbital ridge well developed, posteriorly with narrowly-based cirrus, broadening and distally dissected. Interorbital space slightly concave, narrow, its width slightly less than pupil diameter. Small papillae or granules dotting upper part of eye, in 4 longitudinal rows in interorbital space; pit-like occipital depression; nasal spines short, sharp, directed dorsally and posteriorly. Anterior pair of nostrils tubular; posterior pair with elevated margin, directed anteriorly. Parietal spines not developed; parietal cirri usually present, short and simple (barbel-like). Nuchal spines forming apically rounded conical tubercles under skin, directed dorsally and posteriorly, their length (2.5% head length) less than pupil diameter, cirri absent on surface. Preopercular spines 4, pointed; first (bifurcated) and second directed dorsally, third and fourth directed ventrally. Supraorbital, lacrimal, and suborbital spines absent. Lower jaw subterminal. Upper jaw reaching vertical at posterior margin of orbit. Fine granules dotted on snout and dorsolateral surface of head, also scattered anteriorly on back (abundant under dorsal fin) almost to posterior end of caudal peduncle. Skin bare between dorsal and lateral-line scale rows; ventral surface of head and abdomen naked.

Dorsal row of large scales incomplete anteriorly (distance from head equal to eye diameter, first scale above 3rd–4th lateral-line scale or under dorsal-fin spine VI), posteriorly just short of end of caudal peduncle; all scales of dorsal row with finely serrated, rounded or angular dorsal edges ( Fig. 6A ). Precaudal lateral-line scales with up to 10–13 small spinules along dorsal margin, up to 4–6 spinules on posterior margin below canal pore ( Fig. 6B ); spinules less numerous thereafter, almost disappearing below canal pores on caudal peduncle ( Fig. 6C–D ). Lateral line continuing onto caudal-fin base usually by one scale. Two precaudal scales on caudal peduncle in front of caudal-fin base, one each above and below lateral line ( Fig. 4 ). Sides of body under pectoral fins with 15/14 axillary scales, in 5 rows, with 5 scales in each upper row.

First ray of dorsal fin located above base of opercular lobe. Anal-fin origin under third soft dorsal-fin ray. Anal-fin length 14.8% SL. Caudal peduncle longer than anal-fin base (19.3% SL), its depth 31.8% of caudal-peduncle length. Urogenital papilla cylindrical, not widening posteriorly, terminating with short claw-like appendage; length of papilla 11.3% SL. Counts and measurements shown in Tables 1–3 .

Characters / Materials Holotype Paratypes Entire series Strait of Tartary North of Entire materials Hokkaido Precaudal 1+1 1+1 (4) 1+1 (5) 0+0 (6) 0+0 (6) scales, 1+0 (2) 1+0 (2) 1+0 1+1 (1) 1+0 (1) dorsal+ventral 1+1 (1) Lateral-line 1 1 (4) 1 (5) 0 0 (4) 0 (5) scales on 0 (2) 0 (2) 1 (3) 1 (3) caudal fin

Type series Additional materials

Radiograph ( Fig. 3B ). As in other Icelus species ( Nelson 1984), first vertebra with shortened neural process. Bases of two anteriormost spinous rays of dorsal fin close together, associated pterygiophores in front of first neural process. Pterygiophore of first soft dorsal-fin ray in front of neural spine of 8th vertebrae. Anal-fin rays 15, one ray in precaudal region. Caudal fin with 11 (6+5) primary rays, 7 upper and 5 lower secondary rays; hypural plates fused at base, with distal slit.

Paratypes (4 females TL 68–132 mm and 2 males TL 97–98 mm). Body high, dorsally humped. Preanal portion 53.4–60.0 % (average 56.3) SL. Head barely compressed, depth 63.2–81.7 % (average 71.3) HL. Parietal spines not developed (indistinct and smooth in 2 specimens, TL 94 and 98 mm), replaced by cirri ( Fig. 5 ). Nuchal spines well developed, directed posteriorly, hidden under skin, length 7.9–12.3% (average 10.7) HL. Supraorbital cirri broadening from narrow base, distally divided into 4 or 5 branches. Gill rakers 7–10 (average 8.7). Tiny interorbital granules in 4–6 (average 5) longitudinal rows. Dorsal row of scales incomplete anteriorly, usually beginning above 4–6th lateral-line scales ( Fig. 5 ) [one female (TL 132 mm) with first conventional scale of dorsal row above 5th lateral-line scale, and four scales (one-third size of former) anteriorly]. Usually a single lateral-line scale on caudal fin (in 4 spec.), but occasionally absent (2 spec., TL 68 and 98 mm). Lateral-line scales serrated along dorsal and posterior margin (below canal pore); number of spinules decreasing posteriorly, especially below pores ( Fig. 6 ). Skin on body finely granulated above lateral line. Number of precaudal scales usually 1+1 above and below lateral line; rarely lower scale absent, 1+0 (n=2). Axillary scales 10–18 (average 13.5), of which 4–7 scales in the upper row. Anal-fin length 12.9–15.1% (average 14.1) SL. Caudal peduncle longer than anal-fin base, 14.0–19.3% (average 17.0) SL; caudal-peduncle depth 31.8–43.1% (average 36.1) of caudal-peduncle length. In a large specimen (TL 132 mm) with the pectoral fin reaching 3rd or 4th anal-fin ray, pelvic fin reaching anus. In a smaller specimen (TL 94 mm) with shorter fins, pectoral fin reaching 2nd–3rd anal-fin ray, pelvic fin not reaching anus. Pelvic-fin rays I,3. Urogenital papilla as described for holotype, its length 11.4–12.5 % (average 11.8, n=4) SL.

Cephalic sensory system ( Fig. 7 ). Nasal canal with 2 pores (n1–2), in front of and behind nasal spine; n2 with additional smaller medial pore. Supraorbital canal with 5 pores (so1–5); so1 with additional medial pore; so4 and so5 with 2 additional pores posteriorly. Temporal canal with 6 pores (t1–6); t1 with 3 openings at confluence of infraorbital, supraorbital, and temporal canals; t2–4 each with medial and lateral openings. Infraorbital canal (io1–6) with 8 large terminal pores and 2 rows of smaller canal pores. Preoperculo-mandibular canal with 10 large pores [mandibular (pm1–4) and preopercular (pm5–10)]. Chin pores (pm1 on each side) open in common pit. Coronal commissure with double pore (anterior, posterior). Occipital commissure with five double pores (anterior and posterior), including the central pore, and lateral and centrolateral pores on each side.

Radiograph. Counts shown in Tables 1 and 2 . First pterygiophore of dorsal fin usually located in front of first elongate neural process (in one specimen between processes 1 and 2); pterygiophore of first soft dorsal-fin ray between vertebrae 9 and 10 (n=2) or 10 and 11 (n=4). Precaudal region with 2 anal-fin rays. Caudal fin usually with 11 (6+5) principal rays, less often 12 (6+6) (n=2).

Additional material

Diagnostic characters as described ( Fig. 6 ; Table 1 ).

However, the number of precaudal scales on the caudal peduncle varied ( Table 2 ), usually absent both above and below the lateral line (0+0, n=6), less often present (1+1, n=1). Additionally, lateral-line scales on the caudal-fin base were usually absent ( Table 2 ), may be attributable to geographic variability as the specimens were collected in a more southerly location than the type series. Morphometric measurements showed small differences in some average values compared with the type series, including relative head length, and body height and width ( Table 3 ). However, given the small sample size and larger average fish size in the supplemental material, any conclusions are premature.

Size. The maximum length recorded were 190.5 mm TL for females ( HUMZ 125963) and 127 mm TL for males (ZIN 44541).

Distribution and habitat

The holotype was collected in the western part of the Sea of Okhotsk, paratypes were collected northeast of Sakhalin Island and at the top of Shelikhov Gulf (Penzhina Bay) ( Fig. 8 ). Additional specimens collected east of central Sakhalin and north of Hokkaido, as well as in the Sea of Japan (Strait of Tartary).

The holotype was caught at a depth of 97 m, paratypes at 146–165 m, and additional specimens at 124–327 m, a total bathymetric range of 97– 327 m. Although Schmidt (1950) indicated depths of 10–115 m for I. crassus from the northeastern part of the Sea of Okhotsk, the occurrence of the species in shallow water (10 m) requires verification (possibly a typographical error for 100 m?). The substrate in the collection areas comprised silt, stone, and sand. Bottom water temperatures (3 measurements available) ranged from -0.7°C to 2.15°C.

Comparisons

Icelus crassus shares the distinguishing characters, including numerical counts (see Table 4 ), of the “ I. bicornis ” group (sensu Nelson 1984): suborbital and lacrimal spines absent, additional scale rows absent (except dorsal-row and lateral-line scales), and dorsal-row scales lacking large sharp spines. Differences among species of the “ I. bicornis ” group are summarized in Table 5 .

Icelus crassus differs from I. ochotensis in the absence of parietal spines (vs. present in I. ochotensis ); dorsal scale row incomplete anteriorly (vs. complete, reaching head); parietal cirri broadening and distally dissected (vs. simple barbel-like, if present); axillary scales usually more than 10 (average 13.5) (vs. fewer than 10, average 8.8); lateral-line scales in the middle third of body serrated below canal pore, bearing up to 5 or 6 spinules (vs. usually not serrated, embedded in skin).

Icelus crassus differs from I. bicornis in urogenital-papilla shape (without elongated terminal appendage, Fig. 2B ) (vs. with thin terminal appendage longer than basal part); parietal spines absent (vs. present), supraorbital cirri widened, distally dissected (vs. simple); lateral line on or just short of caudal-fin base (vs. at least 4 or 5 scales short of caudal-fin base) ( Table 5 ).

Icelus crassus differs from I. spatula in urogenital-papilla shape (cylindrical vs. spatulate, flattened and distally widening), absence of parietal spines (vs. present), supraorbital cirri widened and distally dissected (vs. simple). Icelus crassus differs from I. spatula bispinis in absence of parietal spines (vs. present) and nuchal-spine shape (rounded medium-sized tubercles vs. large sharp conical spines).

Icelus crassus differs from I. uncinalis in the absence of parietal spines (vs. present) and nuchal-spine shape (rounded medium-sized tubercles vs. large sharp spines); dorsal scale row incomplete anteriorly (vs. complete).

Icelus crassus differs from I. stenosomus in having a deeper body, average depth 24.2–27.4% SL (vs. low, slender, average depth 20.0 % SL); nuchal-spine shape (rounded tubercles vs. sharp spines); occipital pit present (vs. absent); parietal cirri present (vs. absent); supraorbital cirri widened, distally dissected (vs. simple barbels); dorsal scale row incomplete anteriorly (vs. complete, reaching head).

The “ I. bicornis ” group includes two pairs of species with similar supraorbital cirri and lateral-line scales structure. Icelus ochotensis and I. spatula both have simple supraorbital cirri, and precaudal lateral-line scales below the canal pore embedded in skin and usually lacking spinules (at most 1 or 2) ( Jensen & Volsøe 1949; Chernova & Zorina 2024). Icelus uncinalis and I. crassus , however, have widened and distally dissected supraorbital cirri, and precaudal lateral-line scales below the canal pore with up to 5–6 small spinules. Apparently, this combination of characters led Andriashev (1937) to consider I. ochotensis as a subspecies of I. spatula , and I. crassus as a subspecies of I. uncinalis , all of which are considered here as separate species.

Icelus crassus also differs from I. cataphractus (Pavlenko) and I. spiniger Gilbert (“ I. spiniger ” group), and I. euryops Bean , I. canaliculatus Gilbert , I. rastrinoides Taranetz , and I. perminovi Taranetz (“ I. euryops ” group) (sensu Nelson 1984) by the absence of suborbital spines (vs. present in all of the latter) and absence of sharp spines on the dorsal-row scales (vs present).

Furthermore, I. crassus differs from I. armatus (Schmidt) by lacking additional scale rows above and below the lateral line (vs. 2–5 additional rows both above and below the lateral line), and large spines on the dorsal-row scales (vs single, large serrated spines present on each scale). The former differs from I. gilberti Taranetz in having the first preopercular spine bifurcated (vs. not bifurcated), and lacking additional rows of body scales (vs. 2–5 rows present between dorsal row and lateral line).

Further differences from species not noted by Nelson (1984) include a pair of spines (nuchal tubercles) on the occiput in I. crassus , but absent in I. ecornis Tsutsui & Yabe , I. mororanis ( Jordan & Seale), and I. sekii Tsuruoka, Munehara & Yabe ( Tsutsui & Yabe 1996; Tsuruoka et al. 2006, 2009). In addition, I. crassus differs from I. ecornis in the number of axillary scales (10–18 vs. 26–48) ( Tsutsui & Yabe 1996); from I. mororanis in the number of vertebrae (38–41 vs. 35–37), anal-fin rays (15–16 vs. 10–13), and lateral-line scales (40–43 vs. 35–39), plus the first preopercular spine bifurcated (vs. not bifurcated) ( Tsuruoka et al. 2006, 2009); from I. sekii in the number of vertebrae (38–41 vs. 36–37), anal-fin rays (15–16 vs. 12–14), and lateral-line scales (40–43 vs. 38–40), plus the first preopercular spine bifurcated (vs. not bifurcated) ( Tsuruoka et al. 2006, 2009); from I. hypselopterus Fukuzawa, Mori, Matsuzaki & Kai in having only two rows of body scales (vs. scales scattered over the body above and below the lateral line), fewer anal-fin rays (15–16 vs. 20–21), lower jaw subterminal (vs. protruding beyond the upper jaw), and first preopercular spine bifurcated (vs. not bifurcated) ( Fukuzawa et al. 2022); and from I. mandibularis Yabe in the number of soft dorsal-fin rays (18–21 vs. 22–24) and anal-fin rays (15–16 vs. 19–21), the first preopercular spine bifurcated (vs. not bifurcated), and lower jaw subterminal (vs. protruding beyond the upper jaw) ( Yabe 1983; Masuda et al. 1984).

Figures

FIGURE 2. Drawings of Icelus crassus: male, lateral view (A) and ventral view of urogenital papilla (B) (from Schmidt 1927: figs. 1, 2; as “I. ochotensis sp. nov.”). The lateral view was reproduced as “Icelus uncinalis crassus subsp. nov. Typus” by Andriashev (1937, pl. 5 fig. 2). Depicted specimen is ZIN 21900, the holotype of I. crassus.

FIGURE 3. Icelus crassus, holotype, ZIN 21900, male TL 106 mm, lateral view (A) and radiograph (B). Abbreviations: first scales of lateral line (a) and dorsal row (b).

FIGURE 4. Icelus crassus, holotype, ZIN 21900, male TL 106 mm, caudal region.Abbreviations: locations of precaudal scales above (a) and below (b) lateral line; terminal pore of lateral line (c). Shapes of precaudal scales are shown in insets, with digitally enhanced outlines of their appearance.

FIGURE 5. Icelus crassus, paratype ZIN 21910, female TL 94 mm, lateral (A) and dorsal (B) views. Abbreviations: first scales of lateral line (a) and dorsal row (b); parietal cirrus (c) and nuchal tubercle (d).

FIGURE 6. Icelus crassus, scales of dorsal row (A) and lateral line (B–D): precaudal (B) and caudal region, in anterior (C) and posterior (D) parts; pores of lateral-line canal (arrows) and spinules under pore (oval) are shown.

FIGURE 7. Cephalic sensory system of Icelus crassus, paratype ZIN 21910. Abbreviations: nasal pores (n 1–2); supraorbital pores (so 1–5); infraorbital pores (io 1–8, with terminal openings and two rows of small additional pores on canal); temporal pores (t 1–6, t1 being a cluster of 3 openings and t 2–4 double, medial and lateral); pore on first scale of lateral-line canal (Ll 1); coronal pore (c) with anterior and posterior openings; five pores on occipital commissure (double, anterior and posterior): central pore (occ), lateral (ocl) and centrolateral pores (occl) of right and left sides; preoperculo-mandibular pores (five of ten depictured, pm 5–10); pores n2, so1, and so 4–5 with one additional opening each.

FIGURE 8. Distribution of Icelus crassus: holotype (red triangle), paratypes (red circles) and additional materials (yellow circles).

Tables

TABLE 1. Meristics of Icelus crassus type series and additional materials, with ranges, averages and standard deviations (SD).

Characters /		Type series		Additional materials			All specimens
Materials	Holotype	Paratypes1	Entire series	Strait of Tartary	North of Hokkaido2
	ZIN 21900	Ranges	Average (SD)	ZIN 25281	Ranges	Average (SD)	Ranges	Average (SD)
Number of specimens	1	6	7	1	7		15
Total length, mm	106	68–132	100.3	125	51.9–190.5	127.0	51.9–190.5
Sex	M	4F, 2M		F	5F, 2M		10F, 5M
Vertebrae
precaudal	12	11–13	12.3 (0.8)	12	-	-	11–13	12.1 (0.64)
caudal	28	27–28	27.3 (0.5)	28	-	-	27–28	27.5 (0.53)
total	40	38–41	39.6 (1.0)	40	-	-	38–41	39.6 (0.92)
Fin rays
dorsal spines	IX	IX	9.0 (0)	IX	VIII– IX	8.6 (53)	VIII– IX	8.8 (0.41)
dorsal soft rays	19	18–20	18.9 (0.69)	19	19–21	20.1 (0.69)	18–21	19.5 (0.83)
anal	15	15–16	15.4 (0.54)	15	15–16	15.7 (0.49)	15–16	15.5 (0.52)
caudal	11	11–12	11.3 (0.5)	12	-	-	11–12	11.3 (0.49)
pectoral	19	17–19	18.1 (0.69)	18	18–19	18.1 (0.38)	17–19	18.1 (0.52)
Scale number
dorsal row	27	25–31	28.4 (3.1)	31	26–33	29.0 (2.65)	25–33	28.5 (2.36)
lateral line	43	41–43	42.1 (1.2)	42	40–42	41.0 (0.58)	40–43	41.4 (0.83)

1 Specimens ZIN 21905 (3); 21910 (2) and 24468 (1). 2 Specimens FAKU