Petroschmidtia teraoi Katayama 1943

Petroschmidtia teraoi (Katayama, 1943)

[Japanese name: Hinagenge]

(Fig. 6, Tables 1–2)

Lycodes sp.: Schmidt 1904: 201 (ex parte: 80 mm specimen).

Lycodes schmidti Gratzianov 1907: 430 (ex parte: 80 mm specimen).

Lycodes teraoi Katayama 1943: 103, fig. 2; Matsubara & Iwai 1951: 373; Matsubara 1955: 775; Lindberg & Krasyukova 1975: 147, fig. 117; Toyoshima & Honma 1980: 48; Toyoshima, 1984: 307, pl. 359-A; Toyoshima 1985: 188, fig. 37; Anderson 1994: 119; Hatooka 2002: 1034, fig.; Anderson & Fedorov 2004: 30; Fedorov 2004: S95; Shinohara et al. 2011: 52.

Lycodes sadoensis Toyoshima & Honma 1980: 48, fig. 1; Toyoshima 1984: 307, pl. 359-B; Toyoshima 1985: 189, fig. 38; Anderson 1994: 119; Hatooka 2002: 1031, fig.; Anderson & Fedorov 2004: 29; Fedorov 2004: S95; Balanov et al. 2011: 38.

Diagnosis. A dwarf species of Petroschmidtia (up to 168 mm TL) with the following combination of characters: vomerine and palatine teeth present; outer row teeth of lower jaw antrorse; interorbital and occipital pores usually absent; scales present on nape, body and vertical fins, absent on head, pectoral fin base and belly; peritoneum dusky; vertebrae 83–88; abdominal vertebrae asymmetrical; dorsal fin rays 74–81; anal fin rays 63–68; pectoral fin rays 14–17; pelvic fin rays 3, first ray spine-like.

Description. Counts and measurements are shown in Tables 2–3. Body moderately elongated, height 10–13 times in SL at anal fin origin. Preanal length usually less than 45% TL. Head small, length usually about 5 times in SL. Males becoming larger than 130 mm TL, usually with considerably swollen cheeks. Snout short, rounded, length 1.5 times eye diameter. Interorbital space much narrower than eye diameter. Eye oval, included in dorsal profile of head. Nostril tube short, not or just reaching upper margin of lip when depressed. Upper jaw extending anteriorly beyond lower jaw, posteriorly usually to posterior margin of pupil, rarely to posterior margin of eye. Upper jaw length not exceeding 38% HL (32.1–40.5%, average 35.7%) in females, usually more than 40% HL (32.7–47.6%, average 43.0%) in males. Upper jaw not reaching posteriorly to middle of eye in specimens smaller than 126 mm TL. Upper lip continuous across snout, lower lip with moderately developed labial lobe. Oral valve absent. Submental crests high, united anteriorly forming small lateral ledges.

Gill opening large, inclined anteroventrally, ventral edge located anteriorly (rarely at same level) and lateral to pelvic fin base. Isthmus width about half eye diameter. Opercular lobe pointed or rounded. Gill rakers 2–3 + 9–13 = 12–15 (average 13.7 in 12 specimens), triangular, slightly flattened laterally, without spinules. Pseudobranchial filaments 3–6 (average 4.9 in 10 specimens). Branchiostegal rays 6. A slit behind 4th gill arch. Pyloric caeca usually absent, a single very short appendage in 13 specimens examined.

Teeth on jaws, vomer and palatines. Jaw teeth slightly recurved, blunt. Upper jaw with 5–17 large teeth in outer row (average 10.7 in 79 specimens), 0–4 (0.4) in inner row, anterior teeth of outer row largest. Dentary with 5–17 (10.8) teeth in long inner row, 1–12 (6.1) in short outer row [sometimes up to 6 (0.6) teeth in intermediate row]. External and internal rows usually separated by space equal to external row width. Teeth of external row oriented outward and downward in horizontal plane. Vomer with an irregular patch of 1–5 (1.2) teeth (one specimen from Sea of Okhotsk (NSMT-P 67503) lacking vomerine teeth). Palatine with 2–8 (4.2) conical teeth in a single very short row.

Vertebrae 18–21 (19.5) + 61–69 (65.4) = 80–88 (84.9). Dorsal fin rays 71–81 (76.8). Dorsal fin originating above posterior quarter of pectoral fin, vertically above vertebrae 9–12; 1 or 2 anteriormost pterygiophores associated with neural spines 5–9 (usually 7); posteriormost pterygiophore associated with preural centra 3–5 (usually 4). All specimens with a dorsal pterygiophore absent from interneural space between 3rd and 14th preural centra. Anal fin rays 61–70 (66.0). Anal fin origin anterior to midbody, vertically below vertebrae 22–24; 0–3 (usually 2) anal fin pterygiophores preceding 1st haemal spine, last pterygiophore associated with haemal spine of 3rd to 5th preural centra. Caudal fin rays 9–13 (11.0): 1–2 rays on epural, 3–5 on upper and 4–6 on lower hypural plates. All vertical fin rays branched, except for 1st–4th anal fin ray(s) and 1st–6th dorsal fin ray(s). Anteriormost dorsal and anal fin rays unsegmented, appearing as flexible spines.

Pectoral fin small, its length about half of head length, without notch, consisting of 14–17 (usually 15–16) branched rays, membranes of lower 4–5 rays weakly incised. Pelvic fin base usually posterior to isthmus. Pelvic fin long, its length about 60–70% of eye diameter, slightly pointed posteriorly, not reaching pectoral fin base, consisting of 1 unsegmented outer ray and 2 segmented rays with innermost ray longest and branched (Fig. 7).

Head pore system slightly reduced compared to most Lycodes (Fig. 8). Interorbital pore usually absent (present in 2 specimens from the Sea of Okhotsk: HUMZ 196187, 196197). Occipital pores usually absent (6 specimens with 1 medial pore, 3 with 2 pores, 4 with 3 pores: FAKU 131656, 130847; HUMZ 196048, 196059, 196187, 196193, 196194, 196197, 196199, 196200; NSMT-P 67501, 67503, 99923). Occipital pores more often observed in Sea of Okhotsk specimens. Two or 3 nasal pores, 1 anteromedial and remainder posteromedial to nostril tube. Posteriormost nasal pore absent from one or both sides in 41 specimens, including paratype of L. sadoensis (HUMZ 65830). Lectotype with 2 anteromedial nasal pores on left side (Fig. 8 A). Postorbital pores usually 2 (positions 1 and 4). Four Sea of Japan specimens, including lectotype, and 14 Sea of Okhotsk specimens with all 4 pores on one or both sides of head. Suborbital pores 6–8, including six along ventral ramus and 0–2 along ascending ramus of canal. Preoperculomandibular pores 8, rarely 7 (upper preopercular pore absent). Fifth and 6th suborbital pores and 6th and 7th preoperculomandibular pores with short associated tubes. Pores in ascending part of suborbital canal, first postorbital, upper preopercular and occipital pores microscopic (much smaller than others, almost same size as neuromasts). Preoperculomandibular canal autonomous.

Three head neuromasts located posterodorsally to nostril tube, 6 backward and medial to eye, 1 dorsal to upper preopercular pore and 4 posterior to occipital pores.

Body lateral line system represented by 3 rows of neuromasts. Principal row longest, mediolateral, indistinct, containing 65–69 neuromasts, disappearing at about 5% TL before caudal fin base, 23–26 neuromasts anterior to a vertical through 1st anal fin ray, passing more or less on mid-body, sometimes slightly below, lower scale row numbers usually less than upper scale rows. Predorsal row with 3–4 neuromasts. Dorsolateral row with 11 neuromasts at least, about 7 anterior to a vertical through 1st anal fin ray.

Head without scales. Body scaled, except for belly and pectoral fin base. Scale cover on sides of body usually reaching (rarely just short of) opercular lobe. Ten to 23 scale rows between dorsal fin base and anal fin base at level of first anal ray. Usually 1 to 19 scale rows on nape before dorsal origin (13 specimens, 98.7–146.0 mm SL lacking scales on nape, scale cover on sides of body dorsally discontinuous). Belly usually completely naked; scale cover on sides of body united just anterior to anus, forming 1–7 transverse scale rows in 13 specimens [HUMZ 65830 (paratype of L. sadoensis), 81284, 196048, 196058, 196189, 196194, 196195, 196198, 196201; FAKU 130813, 130847; OMNH-P 6403; NSMT-P 105704]. HUMZ 196200, FAKU 25729 and HUMZ 196193 with 15, 18 and 24 scale rows before anus, respectively. Partly scaled belly more often observed in specimens from Sea of Okhotsk. Pectoral fin usually completely naked [4 specimens, including paratype of L. sadoensis (HUMZ 64826, 65830, 196187, 196200), with a few scales on fin base on one side only, 2 specimens (NSMT-P 98032, HUMZ 196058) with 3 or 4 scale rows on both sides]. Scales covering dorsal and anal fin bases posteriorly up to 10–50% of fin height.

Osteology. Abdominal and a few (1–15) anteriormost caudal vertebrae slightly, but distinctly asymmetrical. Neural spine of first vertebra fused with centrum. Neural spines of 2nd to 4–8th anterior vertebrae flattened laterally, expanded. Pleural ribs from 3rd to ultimate or penultimate abdominal vertebrae; epipleurals from 1st to 9– 15th abdominal vertebrae. Infraorbital bones 7, weakly ossified; ossified regions of anterior 4 contacting (Fig. 9).

Neurocranium (Fig. 10) moderately elongate, maximum depth 3.7 times in length, maximum width 2.1, orbitorostral part length 1.5; otic capsules swollen. Frontals fused to each other along almost entire length, separated posteriorly by anterior projection of supraoccipital. Large single dorsomedial opening in orbital region; no other openings of supraorbital canal on dorsal surface of frontals. Parietals separated by supraoccipital. Prootic separated from intercalar. Connection of prootic and pterotic slightly interdigitated. Prootic and exoccipital separated by thin non-ossified tissue. Parasphenoid with a sharp ventral keel; ascending wing high, reaching to level of upper border of trigeminofacial foramen. Postorbital canal of seismosensory system behind pterotic continued in two tube-like extrascapulars.

Palatopterygoid series (Fig. 11) well developed; ectopterygoid and entopterygoid overlapping more than half of anterior and upper margins of quadrate, respectively. Entopterygoid slightly overlapping antero-ventral margin of metapterygoid. Metapterygoid large, in contact with almost entire anterior margin of hyomandibular. Distal margins of subopercle, interopercle and opercle weakly ossified. All openings of mandibular canal in dentary notably larger than the preceding bony bridges. Ventral margin of dentary forming submental crest base unossified, anteriorly weakly folded and with weakly serrated antero-ventral edge (Fig. 11).

Ceratohyal and epihyal separated by narrow cartilage without interdigitation. Six branchiostegal rays: 4 on ceratohyal and 2 on epihyal; anterior two attached to hyoid medially, remaining attachments lateral. Tooth plates on 5th ceratobranchial and pharyngobranchials 2–4 (Fig. 12).

Three interradial openings (Fig. 13). Scapular strut present. Scapular foramen enclosed. Upper lobe of supracleithrum weakly ossified. Ventral process of posttemporal tubercular. Postcleithrum single, thin and Sshaped.

In caudal skeleton, lower hypural plate fused with terminal vertebra; upper hypural plate autonomous (Fig. 14). Epural single.

Coloration. As described above.

Distribution. Eastern Sea of Japan off Honshu Island, southern Sea of Okhotsk off Hokkaido, Japan; Terpenia Bay, Sakhalin Island, Russia. In depths between 107– 322 m.

Remarks. Schmidt (1904) briefly described characters of Lycodes sp. based on two juvenile specimens (ZIN 13010, 80– 120 mm TL) from the Sea of Okhotsk (Eastern Sakhalin, Terpenia Bay near Senyavina Cape). Subsequently, Gratzianov (1907) established a new species (Lycodes schmidti Gratzianov, 1907) based on Schmidt’s description. Our re-examination revealed that the two syntypes of L. schmidti in fact represent two distinct species. Both Schmidt’s (1904) and Gratzianov’s (1907) descriptions and diagnostic characters for L.

schmidti were undoubtedly based on the larger specimen (120 mm TL), which is here designated as the lectotype for L. schmidti. The 80 mm syntype was an example of P. teraoi, being characterized as follows: submental crests high and joined anteriorly; pelvic fin situated slightly behind isthmus; teeth present on vomer and palatines; 4 light vertical stripes in caudal region, vertebrae 20 + 65 = 85; dorsal fin rays 78; anal fin rays 67. This specimen represents the northernmost and shallowest record for P. teraoi.

Their similar counts and proportional measurements suggest that P. teraoi is closely related to L. uschakovi Popov, 1931, another dwarf species inhabiting the northern Sea of Okhotsk. This species is also characterized by high continuous submental crests, large gill openings, a medial lateral line and light vertical stripes on the body (Popov 1931; Taranetz & Andriashev 1934). We confirmed that L. uschakovi lacks dorso-lateral openings of the supraorbital canal on the frontals, and possesses serrated antero-ventral corners on the dentary, expanded neural spines on a few anterior vertebrae, the unsegmented outermost pelvic fin ray and pyloric caeca absent or reduced in size. These characters strongly suggest that L. uschakovi should also be included to Petroschmidtia instead of Lycodes. Lycodes uschakovi differs from P. teraoi in having labially flattened jaw teeth and vomerine teeth absent.

Thus, we consider 4 species as belonging to the genus Petroschmidtia: P. albonotata Taranetz & Andriashev, 1934, P. toyamensis Katayama, 1941, P. teraoi (Katayama, 1943) and P. uschakovi (Popov, 1931).

Petroschmidtia teraoi is characterized by a fully extended medial lateral line (instead of anterolateral only), sharing that character with L. heinemanni Soldatov, L. jugoricus Knipowitsch, L. knipowitschi Popov, L. lavalaei Vladykov & Tremblay, L. luetkenii Collett, L. mucosus Richardson, L. polaris (Sabine), L. raridens Taranetz & Andriashev, L. reticulatus Reinhardt, L. rossii Malmgren, L. seminudus Reinhardt, L. tanakae Jordan & Thompson and L. turneri Bean. However, P. teraoi is distinguished from the above by the following characters: fused submental crests, preanal length usually less than 45% TL, pigmented peritoneum, narrow interorbital space (interorbital width less than eye diameter), larger gill opening, abdominal vertebral number less than 23 and total vertebral number less than 90. Joined submental crests unite P. teraoi with L. caudimaculatus Matsubara, L. hubbsi Matsubara, L. japonicus Matsubara & Iwai, L. microporus Toyoshima, L. ocellatus Toyoshima and L. semenovi Popov, some of the latter also possessing wide gill openings and the pelvic fins located behind the isthmus (L. caudimaculatus and L. hubbsi), or being dwarf species (L. japonicus and L. semenovi). Petroschmidtia teraoi can be distinguished from all of them by the following characters: lateral line medial (vs. ventral), submental crests high (vs. low), and the oral and branchial cavities light (vs. dark brown or blackish).