Lygdamis giardi ( McIntosh, 1885 )

Hutchings, Pat, Capa, María & Peart, Rachael, 2012, 3306, Zootaxa 3306, pp. 1-60 : 26-29

Lygdamis giardi ( McIntosh, 1885)

Figures 6B, 11 D, E, 14, 15, Table 2

Sabellaria (Pallasia) giardi McIntosh, 1885: 421 , pl. 26, figs 13–15, pl. 47, fig. 7, pl. 26A, figs 13–15.

Pallasia giardi .— McIntosh, 1922: 64; Caullery, 1913: 200.

Lygdamis giardi .— Johansson, 1927, 86; Imajima & Hartman, 1964: 324; Kirtley, 1994: 126.

Material examined. HOLOTYPE: as Sabellaria (Pallasia) giardi McIntosh 1885 ; off Port Jackson , New South Wales: 33°51'S 151°22'E; 03.vi.1874; 64 m, BMNH 1885.12 .1.6. Specimen described as 7 mm in length, 2 mm in width and damaged, but currently in worse condition and only anterior end and posterior chaetigers are in vial.

Additional material examined. New South Wales: Sydney, Malabar , 33°49'30"S 151°21'36"E, 27.ii. 1973, 66 m, 8, AM W6191 *; 22.v. 1972, 28 m, 6, AM W6185 *; North Head , 33°49'25"S 151°20'43"E, 27.ii. 1973, 63 m, 81, AM W26682 (mounted for SEM) ; 7, AM W6192 *, 2 km east of Long Bay , 33°58'S 151°15'E, 66 m, 2, AM W6188 *, 5, AM W6189 *; off Maroubra , 33°57'06"S 151°17'37"E, 20.vii. 1972, 58 m, 1, AM W6190 *; Tasman Sea, off Sydney , 33°53'06"S 151°21'54"E, 30.iii.1972, 76.8 m, 2, AM W27553 *, from gritty calcareous mud; off Eden , 36°39'30"S 150°37'48"E, 01.iv. 1972, 86 m, 1, AM W27554 , from muddy quartz sand; off Broken Bay , 33°37'–39'S 152°04–02'E, 10.xii.1980, 1, AM W27555 *; Sydney, off North Head , 33°48'46"S 151°20'59"E, 60 m, 13.iv.1989, 1, AM W20677 *, from sandy substratum; 15.ii. 1973, 66 m, 2, AM W27556 *; Malabar , 33°58'S 151°19'E, 1973, 1, AM W27557 *; 2, AM W27558 *; 45 m, 1, AM W27559 ; 17.v. 1972, 69 m, 3, AM W27560 *; 22.v. 1972, 75 m, 1, AM W27561 ; 02.i.1973, 54.9 – 60.3 m, 4, AM W27562 *; off Tuggerah Lakes , 33°20'S 151°39'24"E, 11.iii. 1972, 60 m, 5, AM W27563 . Tasmania, Bass Strait: King Island , 35 km northeast of Cape Wickham , 39°16'00"S 144°05'24"E, 23.xi. 1981, 82 m, 1, MV F78887 *, from sandy shell. Northern Territory: 11 km, NE of Cape Ford, Anson Bay, Beagle Gulf , 13˚25'02"S 129˚55'.98"E, 16 m, 01.x.1993, NTM 23481 .

Description. As the holotype is incomplete and cut into portions, this description is largely based on material collected from off the NSW coast in the region of the type locality. Body robust, preserved material pale cream, paleae golden with dark brown pigmentation on opercular lobes and tentacular filaments in some specimens. Operculum completely divided into two free long lobes with distal ends oblique ( Figs 11E, 15B). Operculum with two rows of paleae, outer row with 20 pairs of paleae, cylindrical at base and flattened, with nearly symmetrical pointed tips, with smooth margins ( Fig. 15C); inner row with ten pairs of paleae, smooth cylindrical shafts with blunt tips ( Fig. 15D). Opercular papillae, 11 pairs, peripheral to outer paleae of each lobe ( Figs 11D, E, 14E, F). One pair of nuchal spines on each side ( Figs 11D, 14F), stout, strongly recurved without sharp limbations on concave margin. Tentacular filaments compound, arranged in 15–19 rows ( Fig. 14C). Median organ present, with eyespots on either side. Pair of ringed palps, less than quarter length of opercular lobes ( Fig. 14B). Segment 1 with lobe shaped neuropodia ( Fig. 14A), chaetae absent. Segment 2 with three pairs of triangular shaped lateral lobes, connecting branchiae to neuropodia ( Figs 11E, 14D). Fourteen pairs of branchiae present from segment 2 ( Fig. 14D) not extending to posterior segments. Branchiae, taper gently and evenly to subacute tip ( Fig. 14D). Segments 3–6 (parathoracic), with two types of notochaetae arranged transversely, 7–8 lanceolate, with frayed twisted tips, interspersed with 7–8 capillaries ( Fig. 15E). Segments 3–6 with two types of neurochaetae arranged transversely, five lanceolate and five thinner capillaries with compact thecae alternating with lanceolate ( Fig. 15F). Abdominal notopodia with uncini decreasing in number posteriorly, each uncinus with two vertical rows each with about 7–9 teeth ( Fig. 15H). Neuropodia with capillaries, ornamented with irregular thecal laminar extensions ( Fig. 15G), similar in structure on all abdominal chaetigers. Cauda smooth about the length of five posterior abdomen segments ( Figs 11E, 14H).

Variations. Material examined, including sexually mature specimens, varies from 12–43 mm in length (without cauda), 2–5 mm in width, with 17–32 chaetigers, 16–20 pairs of outer paleae, 12–14 pairs of inner paleae, 8–12 pairs of opercular papillae, 17–19 pairs of tentacular filaments and 9–10 pairs of dorsal branchiae.

Remarks. McIntosh (1885) dissected the holotype and cut up the body into sections and not all are still present in the vial, hence we have also illustrated a complete specimen from the same location (AM W6191). The diagnostic characters of L.giardi are the presence of 16–20 pairs of outer paleae which are straight, nearly symmetrical with distally smooth margins and pointed tips, 15–19 rows of tentacular filaments and three pairs of lateral lobes on segment 2. Lygdamis giardi can be separated from L. augeneri by the number of outer paleae, 16– 20 and 42–44 respectively and by the structure of their tips L. giardi having flattened nearly symmetrical tips whereas L. augeneri has sharply bent outer paleae with broad, blunt flattened tips (see Fig. 15C and 13C).

Distribution. Lygdamis giardi has a discontinuous distribution around Australia, and this may represent a true record or reflect the lack of collecting on the shelf around Australia; currently reported from New South Wales, Tasmania and Northern Territory. This species has also been recorded from the Moluccas Islands, Indonesia ( Caullery, 1913) although this material has not been checked.

Habitat. Inshore at depths of 16– 86 m, in sediments ranging from coarse sand to muddy sand. Most records of solitary individuals but one sample of 81 individuals suggesting they can form small colonies.