Dilatatiocauda multidenticulata, Harris, 2002

Harris, V. A., 2002, A New Genus Belonging to the Family Porcellidiidae (Crustacea: Copepoda: Harpacticoida) With Three New Species from Australia, Records of the Australian Museum 54, pp. 1-24 : 6-11

Dilatatiocauda multidenticulata n.sp.

Figs. 1, 3–6

Type material. HOLOTYPE adult female with egg mass removed, length 0.85 mm, AM P58798 . ALLOTYPE adult male, length 0.61 mm, AM P58799. Type population collected from Dictyopteris sp. , infralittoral fringe, Nambucca Heads reef, New South Wales (30°37'S 152°58'E), Australia, 5.11.82, V. A. Harris . PARATYPE material: NSM Tokyo Cr 13415, 30 ♀♀ & 33 + juveniles. Designated paratype material from Zonaria sp. , Ballina, N.S.W. (28°52'S 153°36'E), 2.11.82, AM P58801, 30♀♀ , 1133 + 7 coupled 33. Designated paratype material from Dictyopteris sp. , Ballina, N.S.W., 2.11.82, BMNH 2000.1190 – 1250 , 40 ♀♀ , 2133.

Material collected from Sydney and the northern coast of New South Wales by V.A. Harris: BALLINA, Pontoon rocks, (28°52'S 153°36'E), 1.11.82, washed from Pterocladia sp. , 1♀; Sargassum sp. , 384♀♀, 4833 + 113 coupled 33; unidentified red seaweed 42♀♀, 633 + 9 coupled 33; Ecklonia radiata 10♀♀, 233 + 2 coupled 33; Ecklonia radiata holdfast 14♀♀, 1033 + 7 coupled 33; Zonaria sp. , 21♀♀, 1233 + 9 coupled 33, 2.11.82, washed from Zonaria sp. , 124♀♀, 4533 + 17 coupled 33 [designated paratype material]; Dictyopteris sp. , 83♀♀, 4933 + 8 coupled 3 [designated paratype material]; Sargassum sp. , 12♀♀, 233; Rhodymenia australis 1♀, 13 + 2 coupled 33; washed from rocks encrusted with pink coralline weed 3♀, 13. ARRAWARRA HEADLAND, (30°03'S 153°02'E), 3.11.82, washed from Caulerpa sp. , 2♀♀, 13 + 3 coupled 33; Sargassum sp. , 2♀♀, 233 + 2 coupled 33; rocks encrusted with pink coralline weed 1♀, 4.11.1982, Dictyopteris sp. , 45♀♀, 4233 + 23 coupled 33; Dictyopteris sp. , + Lobophora sp. , 39♀♀, 1333 + 5 coupled 33; Caulerpa sp. , 18♀♀, 633 + 7 coupled 33; mixed weed from coral pool, 26♀♀, 733 + 4 coupled 33. NAMBUCCA, (30°39'S 153°01'E), 5.11.82, washed from Sargassum sp. , 13♀♀, 633 + 5 coupled 33; Dictyopteris sp. , 169♀♀, 8433 + 53 coupled 33 [type population]; Gelidium sp. , 3♀♀; mixed weed ( Hormosira , Sargassum , Caulerpa sp. ), 9♀♀, 233 + 8 coupled 33; Halimeda sp. , 1♀, 1 coupled 3; Sargassum sp. and Halimeda sp. growing under overhanging rocks, 141♀♀, 9733 + 63 coupled ♀♀; Ecklonia radiata 4♀♀, 13 + 1 coupled 3; Padina sp. , 33♀♀, 1033 + 6 coupled 33. CRONULLA, Shelly Beach rocks, Sydney, (34°03'S 151°11'E), 7.2.74, washed from Dilophus marginatus 3♀♀, 13; Sargassum sp. , 4♀♀, 233, 21.8.75, Dictyopteris sp. , 104♀♀, 3433 + 39 coupled 33, 17.2.77, Sargassum sp. , 81♀♀, 1533 + 32 coupled 33; Pterocladia sp. , 109♀♀, 3033 + 4 coupled 33; Dictyopteris sp. , 270♀♀, 15833 + 30 coupled 33; coralline weed 14♀♀, 833; Dictyopteris sp. , 390 animals (not sorted); Cystophora sp. , 20 animals (not sorted); Ecklonia radiata 25 animals (not sorted); rocks 17 animals (not sorted); 18.2.77, Sargassum sp. and other seaweeds 146 animals (not sorted); Lobophora sp. and Padina sp. , 20 animals (not sorted).

Diagnosis. Adult female: dorsal pits small, not conspicuous; comb plates on labrum with 4 or 5 ridges; sternal plate of metasomal segment 4 without ridges, posterior edge fimbriate; caudal rami elongate, rectangular (L/W = 4.0),

seta proximal (inserted 1 5 down ramus); terminal seta T1 short, thick, pinnate, T2, T3, and T4 pinnate, equal in size, seta T4 set in from medial corner (¼ width of ramus); longest geniculate seta on antenna not longer than endopod segment 2; lateral denticulate peg area on P1 endopod large (= ½ width of endopod), no denticulate pegs along medial edge; segments 2 and 3 of P4 endopod not fused; no chitinous striations along anterolateral edge of female P5. Adult male: antennule coupling apparatus with 3 conspicuous denticulate pads, dactylus with expanded lobe; P2 endopod with 2 terminal setae; rows of ventral setules absent at base of terminal setae on P5.

Dimensions. Females: mean length 0.84 mm (SD = 0.023, N = 30), cephalosome width 0.53 mm (SD = 0.013, N = 30), body length to width ratio 1.6. Rostrum width 0.15 mm, ratio of body width to rostrum 3.5. Urosome width to length ratio 1.37. Caudal ramus length to width ratio 4.0; dilation index 5.3. Males: mean length 0.58 mm (SD = 0.009, N = 21), width 0.43 mm (SD = 0.007, N = 21), ratio of body length to width 1.35.

Description. Adult female ( Fig. 4A). Pale amber yellow or colourless with red eye spot. Anterior of cephalosome semicircular. Rostrum prominent with hyaline border, projects 2 5 of width ( Fig. 5A). Dorsal pits small (about 1–2 µm in diameter). Scanning electron micrographs show a fine network of ridges surrounding pits and many sensory setae with basal collar (Plate 1A). Hyaline border of cephalosome 13 µm wide, granular. Comb plates on labrum short each with 4 or 5 ridges ( Fig. 4G). Sternal plate of metasomal segment 4 with hair-like setules along posterior edge (fimbriate), ridges absent ( Fig. 4C). Urosome broad ( Fig. 4B), division between anterior and posterior lobes marked by scar and very slight notch, no cleft, anterior lobe without marginal setules, posterior lobe with strong lanceolate marginal setules, one sensory seta on posterior border, medial corner square. Caudal arch very deep (57% of urosome length). Caudal ramus ( Fig. 6A) elongate, rectangular, dilation very small, sides almost parallel. Alpha seta proximally inserted (Hicks’ index = 80%). Alpha and beta setae very close (L/[] = 48). Terminal seta T1 short, thick, pinnate, setae T2, T3 & T4 pinnate, equal in size, setae T2 and T3 close together, seta T4 set in from medial corner of ramus (¼ of width), terminal fringe of fine setules present ( Fig. 4H).

Limbs typical of family. Antenna exopod with five plumulose setae plus spinous seta ( Fig. 4F). Segment 1 of endopod without seta or diagonal row of triangular setules, segment 2 with three lateral setae and six terminal setae, longest geniculate seta as long as segment 2, terminal portion straight, finely serrulate, fine comb on claw ( Fig. 4F shows the small terminal aesthetasc (*) which is present on all species, but usually obscured by the geniculate setae). Maxilliped ( Fig. 5E), coxal plates reduced, widely separated in mid-line, not fimbriate, basis broad, not fimbriate, fimbriate process absent. P1 ( Fig. 3A), first segment of exopod with plain ridge parallel to edge, endopod with large triangular denticulate peg area (= ½ width of endopod), no medial peg area, striated band parallel to fimbriate crescent V-shaped. P3 ( Fig. 5D), spinose seta on endopod segment 2 serrate, almost as long as endopod (0.9:1), J-shaped spinous seta on segment 3 serrate, longer than endopod (1.4:1), long straight spine-like terminal seta finely serrulate. P4 endopod segments 2 and 3 not fused ( Fig. 5C). P5 exopod lanceolate, three dorsal setae near posterior end (first very small) plus small apical seta ( Fig. 5I). Females with 10– 14 eggs in ovisac (mode 12, N = 35).

Adult male ( Fig. 4E). Yellow or colourless. Truncated anterior of cephalosome straight, shoulders angular with epaulet ( Fig. 5B), lateral angle of antennule socket not seen from dorsal view. Rostrum very narrow (0.03 mm wide), cephalosome width to rostrum ratio 14:1. Caudal ramus short, almost quadrate (L/W = 1.12), setation similar to female ( Fig. 4D). Anterior process and seta on compound segment project anteriorly ( Fig. 5F,G), ventral sensory lobe with short aesthetasc and seta (= length of compound segment), aesthetasc not bulbous at base, ventral process or blade present, coupling apparatus with three large, conspicuous, denticulate pads, dactylus with expanded lobe ( Fig. 5G). Endopod of P2 terminates in two plumose setae. First terminal seta of P5 with row of about 20 ventral setules, no setule rows at base of other setae ( Fig. 5H).

Remarks. Dilatatiocauda multidenticulata is easily distinguished from other members of the genus by three large, clearly visible, multi-denticulate coupling denticles on the male’s antennule. The specific name refers to this feature. Scanning electron micrographs reveal a fine surface network of ridges that surround the small, indistinct dorsal

Plate 1. Dilatatiocauda multidenticulata n.sp. A, dorsal surface of cephalosome (right side) showing dorsal pits (c. 1–2 µm) and network of ridges surrounding pits. Several collared sensillae are visible. B, part of urosome and caudal rami showing network of strong ridges and close proximity of & setae. Dilatatiocauda medialis n.sp. C, left “shoulder” of cephalosome showing pits, collared sensillae and dorsal folds. D, part of urosome and caudal rami showing pattern of strong ridges on caudal rami.

pits (Plate 1A,B), but the dorsal surface of the cephalosome lacks honeycomb-like structures.

Distribution and abundance. This species is widely distributed along the northern coast of New South Wales. It has been recorded as abundant from Ballina on the north coast down to Sydney, but it is not known from the southern coast of New South Wales. It has not been found in the Hervey Bay–Fraser Island region of Queensland (latitude 25°S). Large populations (100+)* have been found on many species of seaweed ( Cystophora sp. , Dictyopteris sp. , Dilophus sp. , Pterocladia sp. , Sargassum sp. , Zonaria sp. , and stones encrusted with pink coralline algae). Less frequently, it has been found on Ecklonia radiata , Caulerpa sp. , and Lobophora variegata . (* Sample size about 0.5 kg wet seaweed.)