Metadromia wilsoni ( Fulton and Grant, 1902 ) Published, 2009

Published, First, 2009, New records of crabs (Decapoda: Brachyura) from the New Zealand region, including a new species of Rochinia A. Milne-Edwards, 1875 (Majidae), and a revision of the genus Dromia Weber, 1795 (Dromiidae), Zootaxa 2111, pp. 1-66 : 17-18

Metadromia wilsoni ( Fulton and Grant, 1902) new combination

( Figs. 4a, b)

Cryptodromia wilsoni Fulton & Grant, 1902: 61 , pl. 9. — Ihle l9l3: 91 (in list).

Cryptodromia lateralis Heller, 1865: 71 . — Miers 1876: 57. — Thomson, 1899: 170, pl.20, figs l, 2. — Chilton 1911: 49. Not Dromia lateralis Gray, 1831 .

Dromia pseudogibbosa Parisi , l9l5: 102, pl. 2, figs l, 2. — Balss 1922: 106. — Yokoya 1933: 97.

Petalomera lateralis — Richardson 1949b: 60, fig. 51. Not Dromia lateralis Gray, 1831 .

Petalomera wilsoni — Rathbun 1923:154, pl. 42, fig. 1. — Hale 1927: 113, fig. 111. — Sakai 1936a: 33, pl. l, fig. l; 1936b: 34, pl. l, fig. 4, text fig. 9; 1965: 9, pl. 4, fig. 2; 1976: 24, pl. 6, fig. 1. — Barnard 1947: 368; 1950: 313, fig. 59e. — Guiler 1952: 37. — Dell 1963: 22; 1968: 14, pl. 2. — Bennett 1964: 27, fig. l 4l. — Suzuki & Kurata 1967: 95 (list). — Kim 1970: 9, pl. 1, fig. 3; 1973: 608. — Wear 1979: l; 1977: 572. — Griffin 1972: 56. — Forest 1974: 89 (footnote). — Kensley 1978: 251; 1981: 37 (list). — Kim & Kim 1982: 136. — Miyake 1983: 6, pl. 3, fig. l. — Wear & Fielder 1985: 22, figs 54–57. — Baba in Baba, Hayashi & Toriyama 1986: 309, pl. 162. — McLay 1988: 68, fig. 10a–f; 1991: 470, pl. 1B, figs 6a–d, 7a–c, 8a–c.

Dromia wilsoni — McLay, 1993: 156, fig. 16e; 2001: 84. — McLay, Lim & Ng 2001: 737. — Ng et al. 2000: 159, fig. 2b. — Ng et al. 2001: 5 (list). — Brösing et al. 2002: 330, figs 1, 2. — Davie 2002: 162. — Takeda & Ueshima 2002: 163 (list). — Poore 2004: 304.

“ Dromia ” wilsoni — McLay & Ng 2005: 13 .

[ Dromia ] wilsoni — Guinot & Quenette 2005: 288 , figs 10A, B.

Material Examined. Tauranga Harbour: female, 16.2 mm x 13.0 mm, 37° 39’33.5” S, 176° 10’52.25” E, 2.6 m, wharf pile, TG017 CB, 5 Mar. 2002 ( NIWA 48745 ); female, 20.1 mm x 15.3 mm, 37° 38’34.25” S, 176° 10’53.26” E, 6.7 m, wharf pile, TG105 CB, 7 Mar. 2002 ( NIWA 48749 ); female, 19.3 mm x 14.6 mm, 37° 38’ 42.11” S, 176° 10’55.21” E, 6.4 m, wharf pile, TG113 CB, 7 Mar. 2002 ( NIWA 48750 ); male, 19.3 mm x 15.2 mm, 37° 38’37.50” S, 176° 10’54.55” E, 9 m, wharf pile, 2TRG032 CB , 5 Apr., 2005 ( NIWA 48751 ) .

Description (modified after McLay, 1993). Carapace distinctly wider than long, moderately convex, surface smooth, gently undulating under thick cover of soft, long setae giving surface an areolate appearance. Cardiac, branchial grooves well marked by depressions, one pair of medial cardiac pits, another one more posterior. Rostrum tridentate, median tooth small, blunt, on lower level, projecting as far forwards as lateral teeth separated by a U-shaped sinus, from which extends distinct frontal groove separating 2 rounded protuberances. Three strong anterolateral teeth extend back from level of suborbital tooth: first tooth directed forwards, last 2 upwardly directed.

Posterolateral tooth large, also projecting upward. Small tubercle on the ridge behind branchial groove close to base of posterolateral tooth. Posterolateral carapace margins convergent, posterior margin concave.

Lateral rostral teeth continuous with supraorbital margin, with broad, blunt supraorbital tooth. External orbital corner not produced, with small fissure separating it from strong suborbital tooth visible dorsally. In dorsal part of orbit, beneath supraorbital margin, vestige of parallel ridge meeting weak vertical ridge (an extension of the supraorbital tooth) at lateral end of ridge, which tends to divide off corneal region of orbit.

First article of antenna much wider than long, medially beaked, gaping, twisted. Antennal flagella length 0.43CW.

Subhepatic area of carapace convex with small, blunt tubercle beneath suborbital tooth, larger tubercle, lower, between it, first anterolateral tooth. Female sternal grooves ending wide apart on small raised tubercles between bases of P2, P3.

Chelipeds (P1) large, especially in male. Merus triangular in section, all 3 borders with small rounded granules. Carpus with 2 large distal nodules, inner angle with sharp tooth. Propodus smooth, upper border in male sparsely covered in rounded nodules, nodules rudimentary in females. Inner, outer surfaces of fingers longitudinally grooved, covered with tomentum, distal surface alone naked, glabrous. Fingers pink, hollowed out internally, armed with seven well developed teeth, gaping when closed; long, silky hairs on inner surface of propodus, fingers. Ratio of width of sternite 4 to length approximately 1.0.

P2, P3 shorter than chelipeds, first slightly longer than second. Carpi, propodi with tuberculiform nodules at distal ends of anterior borders. Dactyli approximately as long as propodi, inner margins with 5–7 small spines increasing in size distally.

P4, P5 much reduced, similar in size. One propodal spine opposing the P4 dactylus whose inner margin has 3 or 4 minute spines. P5 dactylus opposed by propodal spine. No spines on outer propodal margins of either leg.

Abdomen with 6 free somites. Telson much wider than long, male telson trigonal (width= 1.5length), female telson subtruncate (width = 1.7length). Uropod plates well developed, visible externally. Abdominal locking mechanism involves uropods fitting in front of well developed serrated flange on bases of P2. G1 as partially rolled tube with densely setose, broadly rounded tip armed with sharp horny tubercle. G2 simple, needle-like. Vestigial pleopods on somites 3–5 in males.

Remarks. Both Fulton and Grant (1902 b) and Rathbun (1923a) stated that there are four anterolateral teeth, but the first tooth is clearly subhepatic in position and only three teeth are actually on the anterolateral border. Vestigial pleopods are found on the abdominal somites 3–5 in males of G. wilsoni . Another feature that may well be plesiomorphic is the presence of small spines on the inner margin of the P4 dactylus. These are also found on the P4 and P5 dactyli in the species of Sphaerodromia ( McLay, 1991, Table 1), which have a number of ancestral character states. McLay (1991, 465) presented a hypothesis about the origin of the dromiid camouflage-carrying limbs from walking legs that normally have spines on their inner margins, and so according to this view the condition found in M. wilsoni is transitional between a walking limb and a limb solely adapted for carrying.

M. wilsoni occupies a wide range of depths and it is the only dromiid known in southern cooler temperate waters ( New Zealand). In higher latitudes it occurs intertidally, but in tropical waters it is only found in deeper water, presumably where temperatures are colder. Depth range for this species is 0–520 m.

Compared to crabs of similar size from other families, the reproductive strategy of M. wilsoni is not directed at producing large numbers of larvae: two ovigerous females from the Marquesas Is (CW = 46.5mm), carried approximately 3300 eggs (0.7mm diam.), and another (CW = 44.6mm), approximately 3500 eggs (0.65mm diam.) ( McLay, 1991). Wear (1970) reported slightly larger eggs ready to hatch (1.1 mm) from New Zealand. M. wilsoni has three or possibly four zoeal stages and a large megalopa ( Wear, 1970, 1977; Wear and Fielder, 1985), fewer zoeal stages than found in some other dromiids, but the length of the larval period is as yet unknown. Thus the exact reasons for its extraordinarily wide distribution are not clear: maybe some combination of longer larval duration, larger size and better survival.

Camouflage: small crabs (CW<15 mm) carry sponge or ascidian caps, but larger crabs often do not carry any camouflage. The very hirsute tomentum may be sufficient concealment. Dell (1968) suggested that large crabs may not camouflage and subsequent observations seem to support his hypothesis. His statement that the camouflage may be attached to the body in some sponge crabs is not correct since camouflage is always carried by the last two pairs of pereopods and periodically replaced.

Maximum size is 61.0 mm x 45.4 mm for males and 49.1 mm x 34.7 mm for females.

Distribution Metadromia wilsoni was first described from Port Phillip Heads, Melbourne, Australia but it has perhaps the widest distribution of any dromiid crab, including the coasts of Australia from southern Western Australia around the Great Australian Bight to New South Wales, including Tasmania. Its southernmost limit is off the Kaikoura coast, South I., New Zealand (42°25'S, 173°41'E, McLay, 1988). In the Indian Ocean M. wilsoni is known from the east coast of South Africa and even extending to St. Helena (15°58'S, 5°43'W) in the Atlantic Ocean ( Forest, 1974). In the Pacific Ocean it is known as far north as Sagami Bay, Japan, Taiwan and the Hawaiian Is, and as far west as the Tubuai Is, in French Polynesia (23°51.4'S, 147°44.5'W). Its distribution thus includes three oceans as well as both sides of equator in the Pacific. Depth range is 0– 520m.