Leitoscoloplos kerguelensis McIntosh 1885

Leitoscoloplos kerguelensis (McIntosh, 1885)

Figures 8, 9 A–E

Scoloplos kerguelensis McIntosh, 1885: 355, pl. 43, figs. 6–8, pl. 22A, fig. 19; Ehlers 1897: 97; 1901: 169: 1913: 522; Gravier 1911: 108, pl. 5, figs. 60–63; Augener 1932a: 41. Not Fauvel 1916: 433, pl. 8, figs. 23–35; 1932: 165; 1953: 307–308, fig. 160 a–c.

Haploscoloplos kerguelensis: Monro 1939: 124 (in part); Hartman 1957: 275 –276, figs. 1–3; 1966: 9–10, pl. 2, figs. 1–2; 1967: 104 (in part, not Eltanin Sta. 311, 428, 558, 732, 1003, 1009, 1063 and Staten Island Sta. 63-32, 63-63); 1978: 156 (in part, not Glacier Sta. 68-18, 68-55, 69-1; part of 68-1); Bellan 1972: 76; 1975: 789; Arnaud 1974: 552, 563, 638; Averincev 1982: 25 –26, figs. 19–21, pl. III, figs. 6–8, table.

Haploscoloplos kerguelensis minutus Hartman, 1953: 37, figs. 11a–c; Hartmann-Schröder 1965: 194.

Haploscoloplos minutus: Hartman 1978: 156 (in part). New synonymy.

Leitoscoloplos kerguelensis: Hartmann-Schröder & Rosenfeldt 1988: 53 (in part); 1990: 105–106 (in part); Mackie 1987: 3 –4, fig. 2.

Leitoscoloplos kerguelensis minutus: Mackie 1987: 4 –5, Fig. 3. New synonymy.

Leitoscoloplos banzareae Mackie 1987: 8, fig. 7. New synonymy.

Material examined. Chile, South Pacific Ocean, W of Isla Guafo, R /V Vema Sta. V-17 - 10, 397- 501 m, (2, LACM- AHF Poly 5038).—Straits of Magellan, R/V Vema Sta. V-17-18, 248- 262 m (2, LACM-AHP Poly 5002); East of Isla Dawson, R/V Vema Sta. V-17-23, 273 – 280 m (3, LACM-AHF Poly 5003).— South Atlantic, SE of Falkland Islands, R/V Vema Sta. V- 14 - 12, 361 m (1, LACM-AHF Poly 5029).—N of South Georgia, Eltanin Sta. 9-732, 220 – 265 m (1, USNM 56507); Sta. 9-734, 1299– 1400 m (1, USNM 56508).— South Georgia, off Cumberland Bay, 54°11′S, 36°18′W, Swedish Antarctic Expedition, Sta. 34, 252– 310 m, syntype of Haploscoloplos kerguelensis minutus (SMNH 3703). — East Antarctic Peninsula, Prince Gustav Channel, RVIB Nathaniel B. Palmer, Station NBP-35, 64°10.471′S, 058°505′W, 25 May 2000, Smith McIntyre grab, 651 m, (1, JAB) — South Orkney Islands, Eltanin Sta. 7-500, 489– 490 m (1, USNM 56505); Sta. 14-1079, 593– 598 m (1, USNM 56525); Sta. 12-1082, 298– 302 m (2, USNM 56526); Sta. 12-1084, 298– 403 m (12, USNM 56527).— South Shetland Islands, Hero Sta. 721- 726 (1, USNM 60170); Sta. 721-742 (2, USNM 60169); Sta. 721-758 (2, USNM 60172); Sta. 721-964 (1, USNM 60166); Sta. 721-972 (3, USNM 60158); Sta. 1032 (1, USNM 60167); Eltanin Sta. 6-418, 311– 426 m (1, USNM 56501); Eastwind Sta. 0 44, 19 Feb 1966, 62°11′S, 57°49.5′W, 747 m, coll. D. Pawson and D. Squires (1, USNM 69350); off Smith Island, R/V Vema Sta. V-17-43, 21 Apr 1961, 655– 673 m (9, LACM-AHF-Poly 5037).— Bransfield Strait, Eltanin Sta. 6-410, 220 – 240 m (14, USNM 56521); Sta. 6-428, (1, USNM 56502); Sta. 6-437, 267– 311 m (5, USNM 56503). — West Antarctic Peninsula, Hero Sta. 1120 (26, USNM 69381); Eltanin Sta. 5-272 (1, USNM 56499); Sta. 6-439 (8, USNM 56504); off Adelaide Island, Eastwind Sta. 004A, 24 Jan 1966, 67°53′S, 069°10′30″W, 330 m, coll. D. Pawson and D. Squires (12, USNM 69349).— Ross Sea, McMurdo Sound, W of Inaccessible Island, Deep-Freeze II, Glacier Sta. 2, 420 m (2, USNM 1013658).—Weddell Sea, Glacier Sta. 68- 1, 650 m (12 USNM 46601); Sta. 69- 8, 585 m (2, USNM 46605).

Description. A moderate-sized species, up to 30 mm long and 2 mm wide for about 100 setigers; average size 14 mm long and 0.9 mm wide for about 65 setigers. Color in alcohol: brown. Thoracic region inflated, not depressed, with 8–10 setigers, slightly wider than abdominal region (Figs. 8 A, 9A).

Prostomium short, conical, pointed, but not acute on tip (Fig. 8 A); two nuchal slits sometimes apparent in dorsolateral locations; without eyespots. Peristomium a single achaetous ring, twice as long as setiger 1 (Fig. 8 A).

Thoracic parapodia all similar, inconspicuous; notopodia with short, triangular-shaped postsetal lobes, narrow at first, then becoming thicker in last thoracic setigers (Figs. 8 B, 9A); neuropodia with papillate postsetal lobe arising from basal cushion (Fig. 8 B). Abdominal notopodia with thin, narrow, fingerlike postsetal lobes and single, thickened, elongated neuropodia (Figs. 8 C, 9C–D), sometimes with apical notch, never strongly bifurcated (Fig. 8 C). Subpodial flange small, but inflated, continuous with neuropodial lobe (Figs. 8 C, 9C–D).

Branchiae from setiger 13–17, short at first, increasing in length posteriorly. Branchiae more or less symmetrical, sometimes curved towards dorsal mid-line (Fig. 8 C).

Thoracic setae including crenulated capillaries; neurosetae arising from broad cushion, in two rows, with some capillaries of first row short, thin, straight; setae of second row longer, thicker, and curved (Fig. 9 B); notosetae similarly arranged. Abdominal notosetae including crenulated capillaries and furcate setae; in light microscope, furcate setae observed with unequal tynes connected by membrane of fine needles (Fig. 8 D–E), with SEM 7–8 needles observed, individually with sharp tapering tips, lateral needles merging with tynes; tips of tynes expanded, with distinct apical opening (Fig. 9 E). Abdominal neurosetae thin, weakly crenulated; aciculae sometimes with tip emergent.

Pygidium a simple ring, lacking cirri (Fig. 9 D).

Remarks. Leitoscoloplos kerguelensis belongs to a group of species with branchiae from anterior abdominal setigers. This species includes individuals having 8–10 thoracic setigers and branchiae from setiger 13–17. Specimens having branchiae from earlier setigers or from setiger 18 or more posteriorly are here referred to other species (see below). There are numerous records of L. kerguelensis globally, but the species is here restricted to sub-Antarctic and Antarctic locations; some Antarctic and sub-Antarctic records are referred to other species. Leitoscoloplos kerguelensis has, rather than lacks furcate setae (as sometimes stated) and the prostomium is more elongate than its closest relatives. In Antarctica, L. kerguelensis is most closely related to L. geminus and L. mawsoni, differing primarily in having branchiae from setiger 13–17 instead of 10–12. There are further differences in details of the abdominal neuropodia, shape of the posterior branchiae, and general shape of the prostomium. There may also be important differences in details of the structure of the furcate setae, but further study is needed. However, all three species are similar and separated with difficulty. Both L. geminus and L. mawsoni are limited to relatively shallow waters, ca. 0–200 m, whereas L. kerguelensis has been collected from the intertidal to 1400 m, and occurs frequently in samples along the Antarctic Peninsula from 500– 600 m.

Leitoscoloplos banzareae agrees well with L. kerguelensis and is here placed in synonymy. Mackie (1987) stated that the thoracic region of L. kerguelensis contained 8–9 setigers compared to 10 for L. banzareae. In the much larger collection of L. kerguelensis examined here, thoracic regions with 10 setigers have been seen, thus overlapping with the stated differences with L. banzareae. Furthermore, the first occurrence of branchiae on L. banzareae is 14–15 according to Mackie (1987), within the range of 13–17 for L. kerguelensis.

Haploscoloplos kerguelensis minutus was originally distinguished from the stem species on the basis of its smaller size (Hartman, 1953). It was elevated to full species status by Hartman (1978). The present collections contain mature specimens that overlap the size ranges of both the stem form and the subspecies. For that reason and the lack of any other distinguishing features, H. minutus is referred to synonymy with L. kerguelensis.

Many of the published records of L. kerguelensis from Antarctica probably include a mixture of species. For example, records of L. kerguelensis by Hartmann-Schröder & Rosenfeldt (1988, 1990) from the Antarctic Peninsula and Elephant Island appear to be a mixture of L. kerguelensis and L. geminus because branchiae are reported to begin from setigers 10–14.

Scoloplos kerguelensis sensu Fauvel (1916) from the Falkland Islands has branchiae from setiger 18–20 and is likely an undescribed species. The records of S. kerguelensis from India by Fauvel (1932; 1953) refer to yet another unknown species because the thorax consists of 12–19 setigers and branchiae begin from setiger 20–22.

Haploscoloplos kerguelensis sensu Ramos (1976) from the eastern Mediterranean is another undescribed species having eight thoracic setigers, branchiae from setiger 14, bilobed neuropodia, and furcate setae. Haploscoloplos kerguelensis sensu Fauchald (1972) from deep water off Western Mexico differs from typical shallower forms in having a distinct postsetal lobe on abdominal neuropodia, and is most certainly an unnamed species. Haploscoloplos kerguelensis sensu Okuda (1937; 1938; 1939; 1946) is believed to represent another undescribed species.

Leitoscoloplos normalis from Australia is closely related to L. kerguelensis, but differs in having a distinctly bilobed abdominal neuropodium in which the inner lobe is considerably longer than the outer one (Day, 1977: 224– 225, fig. 1C).

Biology. Despite being one of the most common orbiniids in Antarctica and certain subantarctic locations, little information is available on the biology of this species. Averincev (1982) identified Leitoscoloplos kerguelensis (as Haploscoloplos) from shallow sites in the Davis Sea, an area off the coasts of Queen Mary Land and Wilhelm II Land, between the Shackleton Ice Shelf and the West Ice Shelf. Russian scientists have maintained research facilities in the area since the 1960s. As part of annual collections from subtidal collections in depths of 3– 45 m, Averincev (1982) concluded that the life cycle of this species was short with a one-time recruitment in January–February and a life span of approximately one year. Abundance and biomass ranged from 10– 400 specimens per m2 with a biomass of 0.12 to 4 g /m2.

Distribution. Widespread in Antarctic and subantarctic seas: Strait of Magellan, South Georgia, Kerguelen Islands, South Orkney Islands; South Shetland Islands; Antarctic Peninsula; Ross Sea; Weddell Sea. Intertidal to 1400 m.