Leptochiton kerguelensis Haddon 1886

Leptochiton kerguelensis Haddon, 1886

(Figs 1–4)

Leptochiton kerguelensis Haddon 1886: 12, pl.1, fig.2, pl.2, figs 3a–c; Sirenko & Schrödl 2001: 85–95, fig. 51, 4; Sirenko 2006: 82.

Leptochiton pagenstecheri Pfeffer 1886: 107, pl.3, figs 3a–b.

Lepidopleurus kerguelensis; Carcelles 1953: 158; Leloup 1956: 12, fig.1; Dell 1964: 113;

Leptochiton kerguelensis; Kaas & Van Belle 1985: 78 –80, fig.34, map 31 (bibliography and synonymy); Sirenko 2006: 82.

Type. Syntype (NHM 1889.11.9.4) (not examined).

Type locality. Kerguelen Islands, Royal Sound, Balfour Bay, 49°32’N, 70°E, 108 m.

Material examined. Kerguelen Islands, RV Skif, cruise 3, SCUBA, 48°45’S, 69°00’E, 3–15 m, 5 spms, 18.12.1970, leg. A. Pushkin; Crozet Islands., RV Skif., cruise 6, 46°28.4’S, 49°36.8’E, 280 m, 1 spm, 21.09.1973; Falkland Islands. Sedge Island, 51°08’67’’S, 60°22’76’’W, 14–18 m, 1 spm, 0 1.12.2002, leg. V. Laptikhovskyi; Steeple Jason Island., 51°01’42’’S, 61°13’14’’W, 19–24 m, 1 spm, 0 5.12.2002, leg. V. Laptikhovskyi; Magellan Strait and Beagle Channel. Bahia Felipe, 52°39’01’’S, 69°56’36’’W, 38–40 m, 30 spms, 29.03.2000; 52°44’54’’S, 69°52’16’’W, 12.2 m, 4 spms, 27.03.2000; 52°44’54’’S, 69°52’08’’W, 9.7 m, 21 spms, 27.03.2000; Bahia Gregorio, 52°34’32’’S, 69°52’08’’W, 19 m, 6 spms, 27.03.2000; Bahia Laredo, 52°57’S, 70°48’W, 0.5–3.0 m, 1 spm, 20.05.2000, leg. B. Sirenko; Fuerte Bulnes, 53°37’S, 70°56’W, 0–2.5 m, 2 spms, 17.05.2000, leg. B. Sirenko; RV Victor Hensen, st. 1045, EBS, 54°51.8’S, 69°55.6’W, 210 m, 3 spms, 0 4.11.1994, leg. K. Linse; st. 1213, EBS, 54°06.89’S, 66°39.956’W, 63 m, 240 spms, 0 5.11.1994, leg. A. Brandt; st. 1247, EBS, 54°59.43’S, 69°04.64’W, 100 m, 32 spms, 19.11.1994, leg. A. Brandt; st. 1200, EBS, 55°38.52’S, 67°12.86’W, 39 m, 101 spms, 14.11.1994, leg. A. Brandt; st. 1178, EBS, 55°07.30’S, 66°52.78’W, 25 m, 3 spms, 12.11.1994, leg. A. Brandt; st. 1237, EBS, 55°00.51’S, 66°53.14’W, 103 m, 1 spm, 18.11.1994, leg. A. Brandt; st. 1270, EBS, 54°55.17’S, 70°45.15’W, 135 m, 1 spm, 21.11.1994, leg. A. Brandt; st. 1246, EBS, 54°58.00’S, 68°49.31’W, 253 m, 1 spm, 19.11.1994, leg. A. Brandt; st. 1040, EBS, 54°51.00’S, 69°55.7’W, 30 m, 10 spms, 0 4.11.1994, leg. K. Linse; st. 1176, EBS, 55°07.3’S, 66°53.0’W, 25 m, 4 spms, 12.11.1994, leg. K. Linse; st. 1156, EBS, 55°05.4’S, 66°45.5’W, 27 m, 6 spms, 11.11.1994, leg. K. Linse; st. 1232, EBS, 55°00.7’S, 66°54.8’W, 13 m, 1 spm, 18.11.1994, leg. K. Linse; st. 1221, EBS, 55°07.6’S, 66°44.6’W, 33 m, 18 spms, 15.11.1994, leg. K. Linse; st. 1192, EBS, 55°06.6’S, 67°01.6’W, 40 m, 2 spms, 13.11.1994, leg. K. Linse; st.884, EBS, 53°42.6’S, 70°57.5’W, 51 m, 10 spms, 26.10.1994, leg. K. Linse; st. 972, EBS, 53°28.8’S, 70°21.9’W, 92 m, 21 spms, 0 1.11.1994, leg. K. Linse; st. 963, EBS, 53°57.9’S, 70°43.5’W, 38 m, 23 spms, 31.10.1994, leg. K. Linse; st. 958, EBS, 52°58.0’S, 70°41.1’W, 111 m, 1 spms, 31.10.1994, leg. K. Linse; st. 1291, EBS, 54°31.5’S, 72°05.9’W, 484 m, 1 spm, 22.11.1994, leg. K. Linse; Isla de los Estados. RV Eltanin, cruise 5, st. 217, Petersen grab, 55°47’S, 66°17’W, 115 m, 3 spms, 23.09.1962; st. 222, Otter trawl, 53°15’S, 66°51’W, 79–80 m, 2 spms, 27.09.1962; RV Hero, cruise 712, st. 665, 54°44.8’S, 63°52.9’W, 44 m, 7 spms, 11.05.1971; South Georgia Islands. RV Evrika, cruise 22, dredge 34, 53°38’S, 38°07’W, 160–170 m, 1 spm, 30.03.1987, leg. I. Smirnov; dredge 37, 53°45’S, 38°29’W, 270 m, 1 spm, 0 7.04.1987, leg. I. Smirnov; dredge 38, 53°45’S, 39°00’W, 267 m, 1 spm, 0 8.04.1987, leg. I. Smirnov; trawl 139, 54°36’S, 35°30’W, 147 m, 47 spms, 0 3.04.1987, leg. I. Smirnov; trawl 149, 53°52’S, 38°47’W, 179–190 m, 1 spm, 0 7.04.1987, leg. I. Smirnov; trawl 151, 53°43’S, 38°27’W, 158–205 m, 100 spms, 0 7.04.1987, leg. I. Smirnov; dredge 42, 53°39’S, 40°57’W, 140 m, 2 spms, 0 9.04.1987, leg. I. Smirnov; trawl 34, 54°10’S, 35°35’W, 140–150 m, 36 spms, 21.01.1987, leg. I. Smirnov; RV Islas Orcada, cruise 575, st. 8, 10’ Blake trawl, 53°35.8’S, 37°35.2’W, 254–366 m, 3 spms, 11.05.1975; st. 9, 10’ Blake trawl, 53°44.2’S, 37°59.5’W, 132–143 m, 3 spms, 12.05.1975; st. 16, 10’ Blake trawl, 53°38.2’S, 38°01,1’W, 130–135 m, 11 spms, 14.05.1975; RV Professor Siedlecki, cruise 601, st. 23, trawl, 54°06’S, 38°41’W, 197–207 m, 1 spm, 02.12.1986; st.63, trawl, 55°16’S, 34°51’W, 63 m, 1 spm, 08.12.1986; RV Eltanin, cruise 22, st. 1535, Blake trawl, 53°51’S, 37°38.2’W, 97–101 m, 4 spms, 07.02.1966; South Sandwich Islands. RV Evrika, cruise 22, dredge 2, 57°38’S, 26°18’W, 370 m, 3 spms, 0 9.01.1987, leg. I. Smirnov; RV Eltanin, cruise 575, st. 70, 5’ Blake trawl, 56°23.8’S, 27°24.6’W, 161–210 m, 2 spms, 02.06.1975; st. 73, 5’ Blake trawl, 56°16.0’S, 27°30.0’W, 208–375 m, 1 spm, 02.06.1975; st. 74, 5’ Blake trawl, 56°12.0’S, 27°23.9’W, 179–238 m, 9 spms, 03.06.1975; South Shetland Islands. RV Palmer Stat, st. AH4–20, 64°46’36’’S, 64°03’24’W, 6 m, 16 spms, 25.01.1969; st. AH4–30, 64°46’36’’S, 64°03’29’W, 9 m, 11 spms, 25.01.1969; RV Hero, cruise 721, st. 936, Petersen grab, 64°47’5’’S, 64°20’W, 60 m, 2 spms, 04.12.1971; cruise 731, st. 1864, Try Net, 65°45.2’S, 64°06.0’W, 31–45 m, 1 spm, 01.04.1973; cruise 824, st. 13-1, 65°14.00’S, 64°12.00’W, 310–360 m, 1 spm, 19.04.1982; RV Polarstern, ANT VII/3, st. 155-1, small dredge, 63°04.5’S, 57°31.2’W, 98 m, 1 spm, 25.04.2000, leg. M. Rauschert; 56 RAE, King George Id, SCUBA, sample 2, 62°11.683’S, 58°55.303’W, 5 m, 1 spm, 26.01.2011, leg. B. Sirenko; sample 11, 62°11.709’S, 58°55.267’W, 10 m, 2 spms, 27.01.2011, leg. B. Sirenko; sample 17, 62°11.728’S, 58°55.229’W, 15 m, 1 spm, 28.01.2011, leg. B. Sirenko; sample 26, 62°11.782’S, 58°55.179’W, 42 m, 2 spms, 30.01.2011, leg. B. Sirenko; sample 27, 62°11.783’S, 58°55.181’W, 35 m, 1 spm, 30.01.2011, leg. O. Savinkin; sample 37, 62°12.372’S, 58°56.918’W, 4 m, 2 spms, 0 2.02.2011, leg. B. Sirenko; sample 46, 62°12.374’S, 58°56.897’W, 12 m, 1 spm, 0 3.02.2011, leg. B. Sirenko; sample 51, 62°12.359’S, 58°56.806’W, 21 m, 2 spms, 0 7.02.2011, leg. B. Sirenko; sample 65, 62°12.626’S, 58°54.813’W, 9 m, 1 spm, 0 8.02.2011, leg. B. Sirenko; sample 73, 62°12.620’S, 58°54.703’W, 25 m, 1 spm, 0 9.02.2011, leg. B. Sirenko; sample 77, 62°12.641’S, 58°54.626’W, 40 m, 4 spms, 11.02.2011, leg. B. Sirenko; small trawl, sample 83, 62°14.190’S, 58°58.363’W, 70–80 m, 1 spm, 12.02.2011, leg. S. Grebelnyi; Weddell Sea. RV Polarstern, ANT VII/3, st. 111-18, TV grab5, 71°07.50’S, 11°28.00’W, 106 m, 5 spms, 0 5.04.2000, leg. B. Sirenko; st. 111-5, TV grab1, 71°07.50’S, 11°28.40’W, 112 m, 2 spms, 0 5.04.2000, leg. B. Sirenko; Ross Sea. RV Eltanin, cruise 27, st. 1867, 10’Blake trawl, 70°54’S, 171°55’E, 2273 m, 1 spm, 13.01.1967; st. 1930, 74°19’S, 176°39’E, 831–836 m, 1 spm, 28.01.1967; st. 1832, 75°27’S, 168°50’E, 364–366 m, 1 spm, 18.01.1967; Antarctica, Enderby Land. RV Ob, off Molodezhnaya station, st. 346/6, SCUBA, 67°25’S, 45°40’E, 20 m, 1 spm, 17.12.1967, leg. E. Gruzov.

Distribution. Leptochiton kerguelensis is one of the most widely distributed chitons of the Southern Ocean. It inhabits Magellan Strait, Beagle Channel, Terra del Fuego, Isla de los Estados, Falkland Islands, South Georgia Islands, South Sandwich Islands, South Orkney Islands, South Shetland Islands, west part of the Antarctic Peninsula, the Weddell, Dumont d’ Urville, Ross seas, off Enderby Land, Kerguelen, Crozet, Bouvet, Macquarie, Prince Edward and Gough Islands. The species lives at depth from 0.5–3.0 m (Magellan Strait and South Shetland Islands) to 2273 m (the Ross Sea) mainly 25–150 m on muddy sand with stones and gravels. The species was very abundant near South Georgia Islands at a depth of 140– 205 m.

Remarks. Two shell shapes of the species are known: roundly arched (like South Georgian specimen used by Kaas & Van Belle (1985) and subcarinated which were observed in specimens from South Sandwich and South Georgia Islands. Often both shell types may co-occur in the same sample. The specimens of L. kerguelensis figured here and several hundred other studied specimens from different portions of Antarctic and Subantarctic waters revealed some differences in armature of the girdle of specimens collected off Kerguelen Islands (type locality) and the description provided by Kaas & Van Belle (1985). The studied specimens from the Beagle Channel and from the Weddell Sea (RV Polarstern, st 111-18, 05.04.2000) have wider dorsal scales (53 x 37 µm with 8–9 riblets), than specimens from off Kerguelen; sutural and marginal needles as well as ventral scales are smooth without any longitudinal grooves. The specimen from South Georgia which was reported by Kaas & Van Belle (1985) has scales (56 x 20 µm) with 4–6 riblets, striated spicules and ventral scales with weak longitudinal grooves. Specimens from off Kerguelen Islands have longer and narrower dorsal scales (55– 70 x 20 µm with 6–8 riblets) than studied specimens from Beagle Channel and the Weddell Sea. Leptochiton kerguelensis differs from many other species of the genus by having only one megalaesthete without micraesthetes and a very long and thin radula about half the body length and with more than 150 transverse rows of mature teeth. This is one of the smallest chiton species of this fauna. Most specimens studied have BL less than 4.0 mm. Only a few specimens from South Shetland Islands extend to 5.5–6.2 mm. All studied specimens of L. kerguelensis with BL— 4.0– 4.5 mm have only 6–7 gills per side. The largest specimen (BL— 6.2 mm) has 7 gills per side.