Research Article |
Corresponding author: Claude B. Renaud ( crenaud@nature.ca ) Academic editor: Nina Bogutskaya
© 2020 Alexander M. Naseka, Claude B. Renaud.
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Citation:
Naseka AM, Renaud CB (2020) Morphology-based taxonomic re-assessment of the Arctic lamprey, Lethenteron camtschaticum (Tilesius, 1811) and taxonomic position of other members of the genus. ZooKeys 991: 1-67. https://doi.org/10.3897/zookeys.991.54938
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The lamprey genus Lethenteron Creaser & Hubbs, 1922 is widespread across Eurasia and North America, but the number and distribution of its constituent species is not firmly established. After a morphological examination of extant type material of the currently recognized species and their synonyms, Lethenteron mitsukurii (Hatta, 1901) is resurrected with Le. matsubarai Vladykov & Kott, 1978 as its junior synonym. Amongst nonparasitic species Le. reissneri (Dybowski, 1869) and Le. mitsukurii are confirmed as present in Japan and the former is also present on Sakhalin. An in-depth study of large samples of nonparasitic lamprey adults from Japan and Sakhalin Island is needed to determine whether the lower trunk myomere (< 66) individuals from these areas represent one or more undescribed species, or Le. mitsukurii, or Le. reissneri, or a mixture of these three alternatives. The material from the Anadyr Estuary identified by
Arctic lamprey, Lethenteron species, synonyms, taxonomic key
The lamprey genus Lethenteron Creaser & Hubbs, 1922 is widely distributed across the Northern Hemisphere, but the number and distribution of its constituent species is not firmly established. Originally erected by
The goals of this study are to:
Molecular data of
The remaining three species recognized by
Material examined follows the method of
The morphometric, countable, shape, and pigmentary character states for the extant adult type material of Petromyzon marinus camtschaticus, P. japonicus, P. kessleri, and La. j. septentrionalis are given in Tables
The morphometric, countable, shape, and pigmentary character states in all non-type adults identified by
The morphometric, countable, shape, and pigmentary character states for extant adult type material of La. mitsukurii and Le. matsubarai are given in Tables
The common name in Itelmen, formerly Kamchadal, a language spoken in Kamchatka, is Canaháisch. The written description and the drawings of the body (life size) and of the oral disc (enlarged) are based on a metamorphosed specimen collected 30 July 1804 (Julian calendar; 11 August 1804 Gregorian calendar) from marine waters in the harbor of Petropavlovsk-Kamchatsky, Russia. The drawing of the body in side view is thrown into three curves and by using a string along the curves we estimated the total length to be 308 mm. Disc length is ca. 16 mm (≈ 5.2% TL) and urogenital papilla length ca. 9.5 mm (≈ 3.1% TL). The two dorsal fins are separate; the interspace being ca. 22 mm. Caudal fin is lanceolate (= spade-like). Dentition: teeth are yellow; supraoral lamina with two bicuspid teeth separated by a wide bridge; two bicuspid endolaterals on each side; infraoral lamina with seven unicuspid teeth; transverse lingual lamina u-shaped, with seven blunt unicuspid teeth, the median one not enlarged in the figure, but noted as distinct in the text. The figure of the oral disc also shows a total of eleven anterials arranged in two rows; the first one consisting of five unicuspid teeth. Posterial and marginal teeth are not mentioned in the text, nor are they shown in the figure of the oral disc. Body pigmentation is not mottled, dorsal surface of head olive-brown, ventral body surface bluish-silvery, and tips of fins blackish; further on in the text he specifies that the posterior (= second) dorsal fin is blackish. The type specimen is lost, but
Morphometrics in adult types of Petromyzon marinus camtschaticus Tilesius, 1811, Petromyzon japonicus von Martens, 1868, Petromyzon kessleri Anikin, 1905, Lampetra japonica septentrionalis Berg, 1931 and adult topotypes of the latter. Numbers in parentheses are sample sizes.
Petromyzon marinus camtschaticus |
Petromyzon japonicus |
Petromyzon kessleri |
Lampetra japonica septentrionalis |
La. j. septentrionalis |
|
---|---|---|---|---|---|
Type locality | Tokyo and Yokohama, Japan | Tokyo and Yokohama, Japan | Tom’ and Kirgizka rivers, Russia | Onega River, Russia | Onega River, Russia |
Total length (TL, mm) | 418.3 | 397.3 | 128–182 (7) | 281–374 (8) | 290–347 (11) |
Dorsal fin interspace (D1–D2, mm) | 12.4 | 10.2 | undetermined (7) | undetermined (8) | 4.0–21.2 (11) |
Intestinal diameter, mm | undetermined | undetermined | 0.5 (3) | 1.0–4.5 (8) | 1.6–4.9 (11) |
% TL | |||||
Prebranchial length (d–B1) | 9.8 | 9.3 | 9.1–13.7 (5) | 9.0–10.9 (8) | 9.6–10.6 (11) |
Branchial length (B1–B7) | 10.5 | 11.4 | 9.7–11.2 (4) | 9.1–10.9 (8) | 8.7–10.6 (11) |
Trunk length (B7–a) | 53.0 | 52.2 | 46.8–47.4 (2) | 50.6–55.6 (8) | 51.4–56.2 (11) |
Cloacal slit length (a) | 1.6 | 1.6 | 1.5 (1) | 0.8–1.2 (8) | 0.8–1.3 (11) |
Tail length (a–C) | 25.2 | 27.6 | 29.5 (1) | 23.4–27.9 (8) | 24.9–27.5 (11) |
Disc length (d) | 4.8 | 4.1 | 4.2–6.0 (5) | 4.6–5.5 (8) | 4.0–5.7 (11) |
Prenostril length (d–n) | 5.6 | 5.1 | 1.9–6.9 (5) | 5.0–6.8 (8) | 5.4–6.3 (11) |
Snout length (d–O) | 6.2 | 5.8 | 4.8–7.8 (5) | 5.7–7.1 (8) | 6.1–7.0 (11) |
Eye length (O) | 1.5 | 1.5 | 2.0–2.4 (5) | 1.3–2.0 (8) | 1.1–1.5 (11) |
Postocular length (O–B1) | 2.7 | 2.8 | 1.9–3.2 (5) | 2.2–2.9 (8) | 2.4–2.8 (11) |
Interbranchial opening length (B1–B2) | 1.4 | 1.2 | 1.3–1.6 (4) | 1.1–1.5 (8) | 1.2–1.5 (11) |
Interocular width (I) | 3.3 | 3.0 | 2.5–3.2 (5) | 2.6–3.4 (8) | 2.9–3.8 (11) |
Urogenital papilla length | undetermined | 0.7 | 0.5–0.8 (3) | 0.0–0.8 (8) | 0.4–0.7 (11) |
Geographic distribution of the lamprey genus Lethenteron in Eurasia based strictly on the examination of type material of Petromyzon marinus camtschaticus (●), Petromyzon kessleri (■), Lampetra japonica septentrionalis (▲) and
The Japanese common name is Yats’-me-anango meaning eight-eyes-eel, in reference to the eye and seven branchial openings on the side of the body and eel-like body shape. The written description and the drawing of the oral disc (scale not provided) are based on an unspecified number of metamorphosed specimens collected between 1860 and 1863 from Tokyo (appeared as Jeddo) and Yokohama, Honshu Island, Japan. It is not clearly stated whether von Martens collected these himself or if they were obtained from the fish market. The habitat from which they came (i.e., freshwater, brackish or marine) is, therefore, not certain. Total length, 454 mm; snout length, 29 mm (= 6.4% TL). The two dorsal fins are separate, the interspace is 2.5 times the eye diameter (eye diameter not provided). Dentition (Fig.
Trunk myomeres, dentition, oral papillae and oral fimbriae in adult types of Petromyzon marinus camtschaticus Tilesius, 1811, Petromyzon japonicus von Martens, 1868, Petromyzon kessleri Anikin, 1905, Lampetra japonica septentrionalis Berg, 1931, and adult topotypes of the latter. Numbers in parentheses are frequencies of character states. Abbreviations: b, bicuspid; u, unicuspid.
Petromyzon marinus camtschaticus |
Petromyzon japonicus |
Petromyzon kessleri |
Lampetra japonica septentrionalis |
La. j. septentrionalis |
|
---|---|---|---|---|---|
Type locality | Tokyo and Yokohama, Japan | Tokyo and Yokohama, Japan | Tom’ and Kirgizka rivers, Russia | Onega River, Russia | Onega River, Russia |
Trunk myomeres | 75 | 70 | 70 (2), 73, 74, undetermined (3) | undetermined (8) | 68, 71, 72 (4), 73, 74 (3), 76 |
Supraoral lamina | 1u–1u | 1u–1u | 1u–1u (5), undetermined (2) | 1u–1u (8) | 1u–1u (11) |
Endolateral formula | 2–2–2 (2) | 2–2–2 (2) | 2–2–2 (9), 2–2–3, undetermined (4) | 2–2–2 (14), 2–2–1 (2) | 2–2–2 (22) |
Infraoral lamina | 1b4u1b | 1b5u | 1b4u1b (3), 1b5u1b (2), undetermined (2) | 1b4u1b (8) | 1b4u1b (10), 1b7u |
Rows of anterials | 2 | 2 | 2 (2), 3 (3), undetermined (2) | 2 (6), 3 (2) | 2 (4), 3 (7) |
Rows of exolaterals | 0 (2) | 0 (2) | 0 (10), undetermined (4) | 0 (16) | 0 (22) |
Rows of posterials | 1 | 1 | 1 (3), undetermined (4) | 1 (8) | 1 (11) |
First anterial row | 5u | 3u | 5u (5), undetermined (2) | 3u (4), 4u (3), 5u | 3u (9), 4u, 5u |
First posterial row | 20u | 19u | 24u (2), 29u, undetermined (4) | 19u (3), 20u, 21u (2), 22u, 24u | 18u, 19u, 20u (2), 21u, 22u (4), 23u (2) |
Transverse lingual lamina | 2u–I–6u | 2u–I–3u | 5u–I–7u, 7u–I–7u, undetermined (5) | 4u–I–4u (2), 4u–I–5u, 6u–I–7u, 7u–I–6u, 7u–I–7u (2), 7u–I–8u | 6u–I–5u, 6u–I–6u (2), 7u–I–6u (3), 7u–I–7u (2), 7u–I–8u (2), 8u–I–8u |
Longitudinal lingual laminae | undetermined (2) | 7u, 8u | undetermined (14) | undetermined (16) | 9u (3), 10u (5), 11u, 12u (2), 13u, undetermined (10) |
Oral papillae | undetermined | undetermined | undetermined (7) | 13, 16 (3), 18 (4) | 12, 14, 15 (2), 16, 18 (2), 21, undetermined (3) |
Oral fimbriae | undetermined | undetermined | undetermined (7) | 85, 91, 94, 97 (2), 98, 102, 103 | 88, 89 (2), 90, 92, 94 (2), 96, undetermined (3) |
The written description is based on 16 metamorphosed specimens (Fig.
Shape and pigmentary characters in adult types of Petromyzon marinus camtschaticus Tilesius, 1811, Petromyzon japonicus von Martens, 1868, Petromyzon kessleri Anikin, 1905 and Lampetra japonica septentrionalis Berg, 1931 and adult topotypes of the latter. Numbers in parentheses are frequencies of character states. Pigmentation coverage as follows: -, absent to < 1%; +, 1 to < 25%; +++, ≥ 75%.
Petromyzon marinus camtschaticus |
Petromyzon japonicus |
Petromyzon kessleri |
Lampetra japonica septentrionalis |
La. j. septentrionalis |
|
---|---|---|---|---|---|
Type locality | Tokyo and Yokohama, Japan | Tokyo and Yokohama, Japan | Tom’ and Kirgizka rivers, Russia | Onega River, Russia | Onega River, Russia |
Caudal fin shape | spade-like | spade-like | undetermined (7) | spade-like (8) | spade-like (11) |
Pigmentation | |||||
Caudal fin | +++ | +++ | undetermined (7) | +++ (7), undetermined | +++ (10), undetermined |
Second dorsal fin | with blotch | with blotch | undetermined (7) | no blotch, with blotch (6), undetermined | with blotch (10), undetermined |
Lateral line neuromasts | undetermined | undetermined | undetermined (7) | pigmented, undetermined (7) | unpigmented (2), pigmented, undetermined (8) |
Gular | undetermined | undetermined | undetermined (7) | - (7), undetermined | - (7), + (2), +++, undetermined |
The written description is based on ten metamorphosed specimens from the Onega River at Podporozh’e, White Sea basin, Russia, collected December 1901 by N.A. Varpakhovskiy (
Morphometrics in adults identified by
Lampetra japonica japonica | Lampetra japonica kessleri | Lampetra japonica septentrionalis | |||||||
---|---|---|---|---|---|---|---|---|---|
Locality | Amur River | Kamchatka River | Ob’ River | Irtysh River system | Yenisei River | Anadyr Estuary | Tobol River | Vyg River | Shapkina River |
|
15188 | 23440, 23441, 23590 | 6174, 6310 | 6311, 7815 | 14441 | 143711 | 7814 | 8545 | 20802 |
Total length (TL, mm) | 391.5–436.5 (5) | 154.5–198 (4) | 187.5–212 (4) | 144–186 (2) | 122.5 (1) | 144 (1) | 351 (1) | 301.5 (1) | 334 (1) |
Intestinal diameter, mm | 1.0–2.5 (5) | 2.5–4.5 (4) | 0.7–1.3 (3), undetermined | 0.7, undetermined | 0.5 | 0.5 | 5.0 | 2.5 | 3.0 |
% TL | |||||||||
Prebranchial length (d–B1) | 9.4–10.8 (5) | 12.6–14.2 (4) | 9.6–12.0 (4) | 10.8–11.8 (2) | 11.4 | 12.8 | 11.0 | 10.6 | 9.9 |
Branchial length (B1–B7) | 10.0–10.9 (5) | 9.4–10.4 (4) | 8.2–9.6 (4) | 9.0–9.1 (2) | 10.6 | 9.4 | 9.3 | 10.9 | 9.6 |
Trunk length (B7–a) | 54.1–55.3 (5) | 46.9–51.8 (4) | 49.1–51.2 (4) | 47.3–47.9 (2) | 51.4 | 50.7 | 49.7 | 50.9 | 50.6 |
Cloacal slit length (a) | 0.7–0.9 (5) | 0.8–1.2 (4) | 0.5–1.2 (4) | 0.7–1.1 (2) | 0.8 | 0.7 | 0.6 | 1.0 | 0.7 |
Tail length (a–C) | 24.1–25.9 (5) | 24.2–27.8 (4) | 29.2–30.3 (4) | 30.2–31.7 (2) | 26.5 | 27.4 | 28.1 | 25.5 | 29.0 |
Disc length (d) | 4.6–5.4 (5) | 6.4–7.1 (4) | 4.0–6.7 (4) | 5.6–5.9 (2) | 4.1 | 4.5 | 5.8 | 5.6 | 4.6 |
Prenostril length (d–n) | 5.6–6.8 (5) | 7.2–8.1 (4) | 5.2–7.2 (4) | 6.2–6.4 (2) | 6.1 | 6.6 | 6.0 | 5.6 | 5.5 |
Snout length (d–O) | 5.6–7.0 (5) | 8.0–9.1 (4) | 5.4–7.7 (4) | 6.7–6.9 (2) | 6.1 | 7.6 | 7.1 | 6.6 | 6.4 |
Eye length (O) | 1.2–1.4 (5) | 2.1–2.5 (4) | 1.7–2.4 (4) | 2.7–2.8 (2) | 2.4 | 2.4 | 1.6 | 1.8 | 1.2 |
Postocular length (O–B1) | 2.6–2.9 (5) | 2.7–3.0 (4) | 2.0–2.7 (4) | 2.4 (2) | 3.3 | 3.1 | 2.3 | 2.3 | 2.7 |
Interbranchial opening length (B1–B2) | 1.1–1.4 (5) | 1.2–1.3 (4) | 1.1–1.6 (4) | 1.0–1.1 (2) | 1.6 | 1.4 | 1.1 | 1.3 | 1.2 |
Interocular width (I) | 3.2–3.8 (5) | 3.2–3.7 (4) | 2.2–3.7 (4) | 2.7–2.8 (2) | 3.7 | 2.1 | 2.7 | 3.6 | 3.1 |
Urogenital papilla length | 0.0–0.4 (5) | 0.5–0.8 (4) | 0.0–1.0 (4) | 0.7–1.1 (2) | 1.2 | 0.02 | 0.6 | 0.7 | 0.6 |
The written description is based on a 310 mm TL metamorphosed specimen from the mouth of the Amur River, Russia. At the periphery of the suctorial disc is a series of small pointed teeth (= marginals); a second more centrally-located circular series of teeth consists in its lower zone of a row of small pointed teeth (= posterials), in its central zone, on each side, of three transversely-positioned tooth plates (= endolaterals), of which only the top two are bicuspid (the condition of the bottom endolateral is not given), and in its upper zone of two rows of more pointed conical teeth (= anterials) numbering eleven. Maxillary arch (= supraoral lamina) with two strong, sharp canine teeth. Mandibular arch (= infraoral lamina) with an average (therefore, the description involved more than one individual, but only one measuring 310 mm TL is mentioned) of four smaller-pointed teeth, and on either side a strong bicuspid tooth. Tongue crescent bar (= transverse lingual lamina) with 19 teeth; a narrow, weakly convex-concave (= parenthesis-shaped) bar (longitudinal lingual lamina) with 12 pointed teeth at both extremities of the crescent bar. First dorsal fin separated from the higher second dorsal fin by a wide gap. Body ash gray colored above and silvery below. The whereabouts of the type specimen is unknown and is presumed lost.
Trunk myomeres, dentition, oral papillae and oral fimbriae in adults identified by
Lampetra japonica japonica | Lampetra japonica kessleri | Lampetra japonica septentrionalis | |||||||
---|---|---|---|---|---|---|---|---|---|
Locality | Amur River | Kamchatka River | Ob’ River | Irtysh River system | Yenisei River | Anadyr Estuary | Tobol River | Vyg River | Shapkina River |
|
15188 | 23440, 23441, 23590 | 6174, 6310 | 6311, 7815 | 14441 | 143711 | 7814 | 8545 | 20802 |
Trunk myomeres | undetermined (5) | 73, undetermined (3) | 76–77 (2), undetermined (2) | 75, undetermined | 76 | undetermined | undetermined | undetermined | undetermined |
Supraoral lamina | 1u–1u (5) | 1u–1u (4) | 1u–1u (3), | 1u–1u (2) | 1u–1u | 1u–1u | 1u–1u | 1u–1u | 1u–1u |
1u–1u–1u | |||||||||
Endolateral formula | 2–2–2 (10) | 2–2–2 (8) | 2–2–2 (8) | 2–2–2 (3), 2–2–? |
2–2–2 (2) | 2–2–2 (2) | 2–2–2 (2) | 2–2–2 (2) | 2–2–2 (2) |
Infraoral lamina | 1b4u1b (3), | 1b4u1b, 1b5u1b | 1b4u1b, 1b5u1b | 1b4u1b, 1b5u1b | 1b3u1b | 1b5u1b | 1b4u1b | 1b4u1b | 1b4u1b |
1b5u1b, | (2), | (3) | |||||||
1b6u1b | 1b1u1b2u1b | ||||||||
Rows of anterials | 2, 3 (4) | 2 (3), 3 | 3 (4) | 2 (2) | 2 | 2 | 3 | 2 | 2 |
Rows of exolaterals | 0 (10) | 0 (8)2 | 0 (8)3 | 0 (3), undetermined | 0 (2) | 0 (2) | 0 (2)4 | 0 (2) | 0 (2) |
Rows of posterials | 1 (5) | 1(3), 25 | 1 (4) | 1 (2) | 1 | 1 | 1 | 1 | 1 |
First anterial row | 3u (3), 4u (2) | 3u (3), 5u | 3u (2), 4u, 6u | 4u, undetermined | 2u | 5u | 3u | 4u | 1u |
First posterial row | 18u, 19u (2), 20u, 22u | 20u, 21u, 22u, 7u2b13u | 25u, 28u, 31u, undetermined | 21u, ≈30u | 18u | undetermined | 23u | 20u | 21u |
Transverse lingual lamina | 6u–I–7u, | 8u–I–7u, | 7u–I–7u (2), | 6u–I–5u, | undetermined | 8u–I–8u | 8u–I–9u | ?–I–? | 4u–I–4u |
7u–I–6u, | ?–I–8u, | 7u–I–8u, | 6u–I–6u | ||||||
7u–I–7u (2), | undetermined (2) | 9u–I–7u | |||||||
?–I–? | |||||||||
Longitudinal lingual laminae | undetermined (10) | undetermined (8) | 12u (2), undetermined (6) | 7u (2), ≈13u (2) | undetermined | undetermined | undetermined | undetermined | undetermined |
Oral papillae | 16, 17 (2), 22, undetermined | 18, 20, undetermined (2) | 17, 26, undetermined (2) | undetermined (2) | undetermined | undetermined | undetermined | undetermined | 19 |
Oral fimbriae | 96, 100, 111, 126, undetermined | 92, undetermined (3) | ≈110, 121, 122, undetermined | >120, undetermined | ≈82 | undetermined | undetermined | undetermined | 98 |
Shape and pigmentary characters in adults identified by
Lampetra japonica japonica | Lampetra japonica kessleri | Lampetra japonica septentrionalis | |||||||
---|---|---|---|---|---|---|---|---|---|
Locality | Amur River | Kamchatka River | Ob’ River | Irtysh River system | Yenisei River | Anadyr Estuary | Tobol River | Vyg River | Shapkina River |
|
15188 | 23440, 23441, 23590 | 6174, 6310 | 6311, 7815 | 14441 | 143711 | 7814 | 8545 | 20802 |
Caudal fin shape | spade-like (2), undetermined (3) | spade-like (4) | spade-like (3), undetermined | spade-like (2) | spade-like | undetermined | spade-like | spade-like | spade-like |
Pigmentation: | |||||||||
Caudal fin | +++ (4), undetermined | +++ (4) | +++, undetermined (3) | +++ (2) | +++ | undetermined | undetermined | +++ | +++ |
Second dorsal fin | with blotch (5) | with blotch (4) | with blotch, undetermined (3) | with blotch, undetermined | with blotch | with blotch | undetermined | with blotch | with blotch |
Lateral line neuromasts | undetermined (5) | unpigmented (2), undetermined (2) | unpigmented, undetermined (3) | unpigmented, undetermined | undetermined | undetermined | undetermined | undetermined | unpigmented |
Gular | - (4), + | -, + (2), ++ | - (2), +, undetermined | +, +++ | +++ | undetermined | - | + | - |
The written description is based on two metamorphosed specimens ca. 160 mm long collected in the summer of 1903 at the mouth of the Yenisei River near Gol’chikha, Russia. These specimens were presumed to have come from the digestive system of a bird or a fish because their mucous layer was absent and all the fins were destroyed, leaving only occasional shreds. The dorsal body surface was black and the ventral surface yellowish white, with a sharp boundary between the two areas. The posterior end of the body and the tip of the caudal fin were black. Dentition is identical to that of P. kessleri in terms of number and arrangement of teeth in the upper jaw (= supraoral lamina), lower jaw (= infraoral lamina), paired lateral teeth (= endolaterals) and all the fine teeth (= anterials and posterials), but resembles that of Petromyzon (= Lampetra) fluviatilis in the teeth being larger and sharp. It may be assumed that the Siberian lampreys are represented by two forms, parallel to the European Petromyzon (= Lampetra) planeri and P. fluviatilis; P. planeri corresponds to P. kessleri and P. fluviatilis corresponds to P. dentex. The teeth are brown. The number of teeth on the infraoral lamina is not the same in the two specimens; one has six teeth, and the other has eight teeth, with two of the inside teeth being incompletely separated. This indicates that each of these incompletely divided teeth originate from a single tooth, resulting in the total number of eight instead of six teeth. The outermost teeth of the infraoral lamina have two inconspicuous cusps (i.e., bicuspid) in both specimens. There are 17–20 anterials arranged in four oblique rows and these teeth decrease in size from the center to the periphery of the oral disc. The row of small posterial teeth extends from one side to the other, its ends reaching the lower lateral pairs of teeth (= endolaterals). The two syntypes are presumed lost because
The written description is based on one metamorphosed specimen (holotype, USNM 21524) 15 inches (= 381 mm) TL collected in 1877 (
The written description is based on an unspecified number of metamorphosed specimens measuring 80–156 mm TL and collected from small watercourses (streamlets between fields, springs, and small canals) on Hondo [= Honshu], Shikoku, Kyushu, and Hokkaido islands, Japan.
The written description of Lampetra mitsukurii minor is based on an unspecified number of metamorphosed specimens measuring 80–165 mm TL from 14 localities across Japan as follows: Sapporo (Hokkaido Island), Tsuyama, Takayama, Akita, Aganogawa, Tamagawa, Kawagoye, Yamagata, Yamaguchi, Sakura, Hamamatsu, Gifu (eleven localities on Honshu Island), Matsuyama (Shikoku Island), Kumamoto (Kyushu Island). It is supplemented by drawings of the body of a spawning male and a spawning female from Sapporo in side-view, as well as close-ups of their cloacal regions (
Morphometrics in adult types of Lampetra mitsukurii Hatta, 1901 and Lethenteron matsubarai Vladykov & Kott, 1978. Numbers in parentheses are sample sizes.
Lampetra mitsukurii | Lethenteron matsubarai | |
---|---|---|
|
|
|
Type locality | Japan | Shokotsu River, Hokkaido Island, Japan |
Total length (TL, mm) | 138.3–140.1 | 147.5–163.5 |
Dorsal fin interspace (D1–D2, mm) | 0.0 (2) | 0.0 (2) |
Intestinal diameter, mm | undetermined (2) | 0.5, undetermined |
% TL | ||
Prebranchial length (d–B1) | 9.9–10.6 | 11.9(2) |
Branchial length (B1–B7) | 10.7–10.9 | 8.9–9.2 |
Trunk length (B7–a) | 49.1–51.0 | 48.1–48.6 |
Cloacal slit length (a) | 0.8–1.1 | 0.7–1.2 |
Tail length (a–C) | 27.6–28.8 | 30.2–31.2 |
Disc length (d) | 4.9–5.2 | 5.4–5.5 |
Prenostril length (d–n) | 4.8–5.3 | 5.8–6.1 |
Snout length (d–O) | 5.9–6.7 | 7.0–7.1 |
Eye length (O) | 1.6–1.7 | 1.5–2.4 |
Postocular length (O–B1) | 2.6–2.7 | 3.1 (2) |
Interbranchial opening length (B1–B2) | 1.2–1.3 | 1.2–1.4 |
Interocular width (I) | 3.3–3.6 | 2.7–3.1 |
Urogenital papilla length | undetermined (2) | 0.0–0.6 |
The written description is based on seven metamorphosed specimens (holotype + six paratypes) measuring 150–174 mm TL collected in 1950–1952 from Shokotsu River, Hokkaido Island, Japan (44°22'N, 143°20'E). It is supplemented by photographs of the holotype (whole body in side-view and oral disc) and paratypes (intestine and velar apparatus). Lethenteron matsubarai is diagnosable from five metamorphosed Le. japonicum (= Le. camtschaticum) collected sympatrically and measuring 172–372 mm TL by being nonparasitic (intestinal diameter < 1 mm versus 3.5 mm), having weaker dentition (poorly cornified, pale yellow blunt cusps versus strongly cornified, orange sharp cusps) and by the absence of pigmentation versus dark pigmentation on the second dorsal and caudal fins. Additionally, disc length and eye diameter, as a percentage of TL, was respectively, 4.4–5.3 and 1.7–2.3 in Le. matsubarai measuring 150–174 mm TL versus 5.3–6.0 and 2.6–3.2 in sympatric Le. camtschaticum measuring 172–193 mm TL. Dentition: supraoral lamina with one cusp at each end; three bicuspid endolaterals on each side; infraoral lamina with six cusps; single row of 18–23 unicuspid posterials; transverse lingual lamina with an enlarged median cusp and up of eleven cusps in total. Body pigmentation in 4–5% formalin is light brown on back and sides and very light brown on ventral aspect. Trunk myomeres are 66–70 and velar tentacles seven or eight.
Trunk myomeres, dentition, oral papillae, and oral fimbriae in adult types of Lampetra mitsukurii Hatta, 1901 and Lethenteron matsubarai Vladykov & Kott, 1978. Numbers in parentheses are frequencies of character states. Abbreviation: u, unicuspid.
Lampetra mitsukurii | Lethenteron matsubarai | |
---|---|---|
|
|
|
Type locality | Japan | Shokotsu River, Hokkaido Island, Japan |
Trunk myomeres | 66–67 | 69–70 |
Supraoral lamina | 1u–1u (2) | 1u–1u (2) |
Endolateral formula | 2–2–2 (4) | 2–2–2 (3), 2–2–1 |
Infraoral lamina | 6u (2) | 6u (2) |
Rows of anterials | 1, 2 | 2 (2) |
Rows of exolaterals | 0 (4)1 | 0 (4) |
Rows of posterials | 1, 22 | 1 (2) |
First anterial row | 4u, 5u | 3u, 4u |
First posterial row | 20u, 21u | 18u, 19u |
Transverse lingual lamina | undetermined (2) | 2u–I–4u, 3u–I–3u |
Longitudinal lingual laminae | undetermined (2) | 4u, undetermined |
Oral papillae | 11, 23 | 19, 20 |
Oral fimbriae | 87, 106 | undetermined (2) |
A number of individuals of various Lethenteron species possess exolaterals [see
Shape and pigmentary characters in adult types of Lampetra mitsukurii Hatta, 1901 and Lethenteron matsubarai Vladykov & Kott, 1978. Numbers in parentheses are frequencies of character states. Pigmentation coverage as follows: -, absent to < 1%.
Lampetra mitsukurii | Lethenteron matsubarai | |
---|---|---|
|
|
|
Type locality | Japan | Shokotsu River, Hokkaido Island, Japan |
Caudal fin shape | spade-like (2) | spade-like, undetermined |
Pigmentation | ||
Caudal fin | - (2) | - (2) |
Second dorsal fin | no blotch, undetermined | no blotch (2) |
Lateral line neuromasts | unpigmented (2) | unpigmented (2) |
Gular | undetermined (2) | - (2) |
The original description of P. marinus camtschaticus based on a single adult (now lost) is very different from that of P. japonicus represented by two extant adult syntypes, one of which was selected as the neotype of the former taxon by
Because
We reject the hypothesis proposed by
Petromyzon ernstii is considered a junior synonym of Le. camtschaticum on the basis of its adult total length of 310 mm (
In regard to the wide discontinuity in the distributions of the populations of parasitic Le. camtschaticum reported by
Although
The presence of well-developed lower labial teeth (= posterial row) in Le. kessleri versus weakly developed or completely absent lower labial teeth in Le. reissneri was the diagnostic character used by
We suggest that the ten syntypes of P. kessleri retrieved in relatively good condition from the digestive tract of a Common gull [
Similar to the case reported above in the Utkholok River drainage,
Despite having been placed in the genus Ammocoetes, A. aureus is clearly based on an adult individual. The holotype measures 381 mm TL, and it possesses supraoral and infraoral laminae and eyes. Even though the original description is fragmentary, the size of the adult individual, the condition of its supraoral (two cusps) and infraoral (seven cusps, the lateralmost one on either end enlarged) laminae indicate that A. aureus is a junior synonym of Le. camtschaticum.
Because no character was found to distinguish the adults of Le. kessleri from those of Le. alaskense, we provisionally consider the latter to be a junior synonym of the former despite the fact that they occur on separate, but adjoining continents; Le. kessleri in Eurasia and Le. alaskense in North America. Further study is required to test this hypothesis. Interestingly,
A comparison of the original descriptions and extant type material of these two nominal taxa (this study;
In their redescription of the species,
Lampetra mitsukurii is placed by us in the genus Lethenteron because it possesses a row of posterials according to the original description (
In our opinion Le. matsubarai is a junior synonym of Le. mitsukurii because both possess only unicuspid teeth on the infraoral lamina (Table
According to
The nonparasitic Le. reissneri has long been reported from Japan (
Synonyms, new combinations, and misidentifications are included.
Petromyzon marinus Camtschaticus Tilesius, 1811: 240–247, pl. IX, figs I, II [original description, marine waters of St. Peter and Paul Camtschatici (= Petropavlovsk-Kamchatsky) harbor, Russia].
Petromyzon Fluvialis (non Linnaeus, 1758) –
Petromyzon borealis Girard, 1858: 377 [available by indication to Petromyzon fluviatilis Richardson, 1836].
Petromyzon Japonicus von Martens, 1868: 3–5, pl. I, fig. 2 [original description, Tokyo (appeared as Jeddo) and Yokohama, Honshu Island, Japan].
Petromyzon Kameraticus – Dybowski, 1869: 948 [misspelling of P. camtschaticus Tilesius, 1811; treated as a distinct species, not a subspecies of P. marinus as
Petromyzon fluviatilis (non Linnaeus, 1758) –
Petromyzon Ernstii Dybowski, 1872: 220 [original description, mouth of the Amur River, Russia].
Petromyzon Kameralicus –
Petromyzon kamtschaticus –
Ammocoetes aureus Bean, 1881: 159 [original description, Yukon River at Anvik (63°N, 160°W), Alaska, U.S.A.].
Petromyzon (Ammocoetes) fluviatilis var. (non Linnaeus, 1758) –
Lampetra aurea – Jordan and Evermann, 1896: 13 [comb. nov., Yukon River]; Jordan and Gilbert, 1899: 434 [Yukon River];
Entosphenus camtschaticus – Jordan and Gilbert, 1899: 434 [comb. nov., allocation to Entosphenus is proposed as probable, but not certain, Kamchatka].
Lampetra japonica –
Lampetra mitsukurii (non Hatta, 1901) –
Entosphenes camtschaticus –
Petromyzon dentex Anikin, 1905: 15–17 [original description, mouth of the Yenisei River, near Gol’chikha, Russia].
Lampetra fluviatilis (non Linnaeus, 1758) –
Lampetra mitsukurii major Hatta, 1911: 266–268, pl. IX, figs 1, 2, 5, 6 [original description, Sapporo, Hokkaido Island, Japan, spawning male and female].
Entosphenus japonicus –
Lampetra fluviatilis japonica –
Entosphenus (Lethenteron) japonicus –
Lampetra borealis –
Lampetra (Lampetra) japonica septentrionalis
Lampetra (Lampetra) japonica japonica –
Lampetra (Lampetra) japonica kessleri (non Anikin, 1905) –
Lampetra (Lampetra) reissneri (non Dybowski, 1869) –
Lampetra fluviatilis septentrionalis (non Berg, 1931) – Ioganzen 1935a: 369 [comb. nov.].
Lampetra japonica japonica –
Entosphenus japonicus septentrionalis –
Entosphenus lamottei japonicus –
Alaska, Bering Sea, north and east Asia].
Lampetra (Lethenteron) japonica –
Lethenteron japonicum –
Lethenteron japonica –
Lampetra (Lethenteron) camtschatica –
Lethenteron camtschaticum –
Lampetra camtschatica –
Lethenteron reissneri (non Dybowki, 1869) –
Synonyms, new combinations, and misidentifications are included.
Lampetra mitsukurii Hatta, 1901: 22–24 [original description, Hondo [= Honshu], Shikoku, Kyushu, and Hokkaido islands, Japan]
Lampetra mitsukurii –
Lampetra mitsukurii minor Hatta, 1911: 263–266, 268, pl. IX, figs 3, 4, 7, 8 [trinomial based on Lampetra mitsukurii Hatta, 1901].
Lampetra planeri (non Bloch, 1784) –
Entosphenus appendix (non DeKay, 1842) –
Entosphenus mitsukurii –
Lampetra (Lethenteron) mitsukurii –
Lethenteron matsubarai Vladykov & Kott, 1978: 1792–1800 [original description, Shokotsu River, Hokkaido Island, Japan (44°22'N, 143°20'E)];
Lampetra reissneri (non Dybowski, 1869) –
Lethenteron kessleri (non Anikin, 1905) –
Petromyzon mitsukurii –
Possible synonym, new combinations, and misidentifications are included.
Petromyzon kessleri Anikin, 1905: 10–15 [original description, Tom’ River and at the mouth of its tributary the Kirgizka River, Ob’ River drainage, near Tomsk, Russia].
Lampetra planeri (non Bloch, 1784) –
Lampetra planeri reissneri (non Dybowki, 1869) –
Lampetra (Lampetra) japonica kessleri –
Lampetra japonica kessleri –
Lampetra kessleri –
Lampetra japonica (non von Martens, 1868) –
? Lethenteron alaskense Vladykov & Kott, 1978: 7–9, fig. 3 [original description, West Creek, a tributary to Brooks Lake, Naknek River system, Alaska, U.S.A.];
Lethenteron kessleri –
Lethenteron camtschaticum (non Tilesius, 1811) –
Lethenteron reissneri (non Dybowki, 1869) –
A more extensive synonymy is given in
Lampetra reissneri –
Lethenteron japonica kessleri (non Anikin, 1905) –
Lethenteron kessleri (non Anikin, 1905) –
When
Later studies based on the mitochondrial DNA (
Lethenteron adults are characterized by the presence of two dorsal fins; spade-like caudal fin; supraoral lamina with a wide bridge bearing a unicuspid (rarely bicuspid) tooth at each end and rarely one or two unicuspid teeth on the bridge; three (rarely four) endolateral bicuspid teeth on either side of the oral disc (rarely the third tooth may be unicuspid or tricuspid and the fourth tooth unicuspid); infraoral lamina usually with lateralmost bicuspid teeth and unicuspid teeth internally, but much variability exists within the genus (see Table
Character matrix of species of Lethenteron. Abbreviations: b, bicuspid; u, unicuspid. Pigmentation coverage as follows: -, absent to < 1%; +, 1% to < 25%; ++, 25% to < 75%; +++, ≥ 75%. Percentages in parentheses are percentages of occurrence of character states.
Species | Trunk Myomeres | Infraoral Lamina | Transverse Lingual Lamina | Pigmentation | ||
---|---|---|---|---|---|---|
Gular | Second Dorsal Fin | Caudal Fin | ||||
Le. alaskense | 66–721 | 6–11 teeth (the lateralmost and sometimes an internal one bicuspid; the others unicuspid)1 | 9–15 teeth, the median one enlarged1 | -1 | with blotch (94%)1, no blotch (6%)1 | +(17%)1, ++(37%)1, +++(46%)1 |
Le. appendix | 64–702, 66–743 | 6–10 teeth (the lateralmost unicuspid or bicuspid; the others unicuspid)2,3 | 9–15 teeth, the median one enlarged2,3 | +++3 | with blotch (38%)3, no blotch (62%)3 | +(44%)3, ++(26%)3, +++(30%)3 |
Le. camtschaticum | 65–734, 70–755, 72–776 | 1b4u1b5, 1b5u5, 6u1b6 | 6u–I–2u5, 3u–I–2u5, 4u–I–4u6 | -4 | with blotch (100%)4, 15 | +(27%)4, ++(53%)4, +++(20%)4, 18 |
Le. kessleri | 70–747 | 1b4u1b7, 1b5u1b7 | 5u–I–7u7, 7u–I–7u7 | -12, +12 | with blotch (100%)16 | +++(100%)19 |
Le. mitsukurii | 66–708 | 6u8 | 2u–I–4u10, 3u–I–3u10 | -13 | no blotch (100%)17 | -(100%)17 |
Le. ninae | 58–629 | 7u9, 1b3u1b9, 5u1b9, 1b5u9, 6u1b9, 1b4u1b9, 3u1b3u9, 1b1u1b1u1b9 | 6u–I–5u9, 4u–I–4u9, 4u–I–5u9, 5u–I–5u9, 5u–I–6u9, 7u–I–7u9, 2u–I–2u9, 3u–I–2u9, 4u–I–3u9, 5u–I–4u9, 7u–I–5u9, 8u–I–7u9 | -14 | with blotch (100%)9 | +(60%)20, ++(33%)20, +++(7%)20 |
Le. reissneri | 70–726 | 1b5u6, 1b4u1b6 | 2u–I–2u11 | -11 | no blotch (100%)11 | +++(100%)11 |
1 | Caudal fin pigmentation absent to < 1% coverage (i.e., -) [Japan] | Le. mitsukurii |
– | Caudal fin pigmentation between 1% and 100% coverage (i.e., +, ++, +++) | 2 |
2 | Trunk myomeres 58–62 [western Transcaucasia] | Le. ninae |
– | Trunk myomeres > 63 | 3 |
3 | Gular pigmentation between 75 and 100% coverage (i.e., +++) [eastern North America] | Le. appendix |
– | Gular pigmentation absent to < 25% coverage (i.e., -, +) | 4 |
4 | Second dorsal fin unpigmented (no blotch at the apex) [Asia] | Le. reissneri |
– | Second dorsal fin pigmented (blotch at the apex) | 5 |
5 | Parasitic mode of life; individuals reaching up to 790 |
Le. camtschaticum |
– | Nonparasitic mode of life; individuals reaching ≤ 230 mm TL [Eurasia and western North America] | Le. kessleri , Le. alaskense |
The three phylogenetic studies that examined the most comprehensive sets of Lethenteron species (
The authors thank the following who made available material: V. Romanov and O. Karmanova (