Holothuria (Halodeima) signata Ludwig, 1875

O’Loughlin, P. Mark, Paulay, Gustav, Vandenspiegel, Didier & Samyn, Yves, 2007, New Holothuria species from Australia (Echinodermata: Holothuroidea: Holothuriidae), with comments on the origin of deep and cool holothuriids, Memoirs of Museum Victoria 64, pp. 35-52 : 49

Holothuria (Halodeima) signata Ludwig, 1875

Figures 4 , 8 , 9 , Tables 1, 4, 5.

Holothuria signata Ludwig, 1875: 99 , pl. V7, fig. 36.— Lampert, 1885: 64.— Théel, 1886: 222–223.— Ludwig, 1889 –92: 330.— Lampert, 1896: 53.— Ekman, 1926: 438, fig. Dl.

Holothuria edulis . — Ludwig, 1899: 559–560.— Domantay, 1933: 63 (part, H. signata treated as a junior synonym of H. edulis ).

Holothuria (Halodeima) signata .— Paulay, 1989: 10, 27.— Paulay, 2003: 577.— Pawson, 1995: 188.—Samyn 2003: 35.

Holothuria sp. (?) signata .— Erhardt and Baensch, 1998: 1088.

Material examined. Lectotype ( UH E2638 here designated): Pacific Ocean, Tahiti, UH E2638 .

Other material. Mariana Is, Guam I., Asan, reef slope, in crevice on sand, night, 22 Jul 1992, RBINS IG30817 ; Orote Peninsula, south side, under rubble, 15–25 m, 22 Aug 1994, UF E173 ; Piti Bombholes, reef flat, moat, or lagoon, 5–10 m, 19 Jul 2003, UF E4713 ; Saipan I., outside Managaha Survey Site, forereef, under rubble, 8–12 m, 5 Jan 2003, UF E3447 ; Tinian I., Unai Babui, forereef, under rocks on sand, 15 m, 12 May 2005, UF E4640 .

Niue I., off Alofi wharf, outer reef slope, on reef rock, 14 m, 20 May 1986, UF E1333 ; Namukulu , Limu Reef flat, pools, undersides of rocks, 0–5 m, 7 Oct 1991, UF E1406 ; reef flat at Tuapa , <10 m from shore, 27 Aug 1986, UF E1886 ; off Alofi wharf, outer reef slope, 12–15 m, 9 Mar 1986, UF E1663 .

Cook Is, Rarotonga I., Nikao, outer fringing reef, exposed in shallow pools, 20 May 1984, USNM E37966 ; Mauke I., Taunganui Harbor, 15–20 m, 3 Dec 1984, USNM E37968 ; Mauke I., Taunganui Harbor, 12 Dec 1984, UF E1831 .

Society Is, Tahiti I., Tautira, in coral rubble zone, under dead coral blocks, 0.5–1.5 m, 3 Sep 1984, UF E4999; Moorea I., NE corner of Moorea, Aroa, 200–300 m E of channel, 6–15 m, 7 May 2006, UF E5015; Moorea I., barrier reef between Cook’s and Opunohu Bays (Vaipahu), outer part of barrier reef, within 1–60m of reef crest, 0–2 m, 3 Jul 2006, UF E4986.

Tuamotu Is, Rangiroa Atoll, off Hotua Ura Motu, ca. 1 km W. of Avatoru Pass, outer reef slope, under rocks, 15–21 m, 10 Oct 2001, UF E325; Rangiroa Atoll, ca. 1 km S of NW point of atoll, off Motu Maeherehonae, outer reef slope, under rocks, 6–12 m, 10 Nov 2001, UF E329; Rangiroa Atoll, ca. 2 km S of NW point of atoll, at southernmost storm lock zone, off Motu Maeherehonae, outer reef slope, exposed, 3–12 m, 26 Oct 2001, UF E591.

Pitcairn Is, Henderson I., outer reef slope off North Beach , 15 m, 17 May 1987, USNM E50251 ; outer reef slope off Northwest Beach, 10–14 m, 15 May 1987, USNM E50252 ; Oeno Atoll, lagoon near south shore of main island, 2.5 m, 28 May 1987, USNM E50253 ; Pitcairn I., 8–20 m, May 1987, USNM E50254 .

Description (anatomy based on UF E173 only). Cylindrical,>5 times as long as wide (14.5 cm x 2.5 cm in UF E173), with rounded anterior and posterior; anus terminal, mouth ventral; body wall smooth, with velvety texture provided by dense layer of table crowns arranged right beneath the surface, 0.5–2 mm thick, thicker dorsally than ventrally. Interior of body wall off-white, with conspicuous, large, scattered, black spots that do not positionally correspond to location of tube feet. Ventral and dorsal tube feet in rough rows, but spread out, all small, not elevated on tubercles. Pedicels with well developed terminal disc; dorsal tube feet also with terminal discs, but narrow, reduced. 2 stone canals and madreporites on left side, 4 on right side; single, ampulliform, 11 mm long, polian vesicle ventrally. Gonad on left side. Ring canal 9 mm posterior to calcareous ring. 18–21 peltate oral tentacles ( UF E173 - 21, UF E325 - 18). No specialized perianal tube feet. No cuvierian tubules. Longitudinal muscles narrow, bifid, attached only medially, with broad free margins.

Dorsal body wall with abundant tables and sparser rosettes. Tables with well developed crown of maltese cross with double ring of 8 spines typical of species group; spire elongate, comprised of 4 pillars joined at ends and by mid-level cross beam; base of table with smooth knob, lacking disk. Tables 1.75 +/-0.10 times as long as wide, 51.5+/-2.3 um (N=10, range: 47.5–55 um) long, 29.5+/-2.7 um (N=10, range: 25–35 um) in diameter (at crown). Rosettes usually simple, with two parallel perforations, one of these subdivided in some, with 1 or 2 additional, terminal perforations developed in some, rarely more complex. Respiratory tree with abundant, thin, spiny rods. Longitudinal muscles, circular muscles, polian vesicles, and tentacle ampullae without ossicles.

Colour. In life: greyish-brown, somewhat lighter ventrally than dorsally; with small, round, cream to light tan spots surrounding each pedicel and papilla, both dorsally and ventrally. Tentacles yellowish to cream. Pedicels light tan basally, like the spot from which they arise, rapidly darkening to black-brown terminally, but with light tan terminal disc. Papillae same.

Distribution. Oceania, at least from the Mariana Is and Niue I. in the west, to the Pitcairn Is in the east ( Paulay, 1989, 2003, herein).

Remarks. Holothuria signata was relegated into the synonymy of H. edulis soon after its description. Ludwig himself later (1899) considered his species synonymous with H. edulis , based in part on Lampert’s (1896) suggestion that they may be conspecific. Most literature records subsequent to the original description (such as Lampert, 1896) are secondary citations, or records of specimens that, on the basis of their description, are referrable to Holothuria edulis . The only records of additional specimens of H. signata are Paulay’s (1989, 2003) records from the Pitcairn and Mariana Is, although little information was provided in those papers, and Erhardt and Baensch’s (1998) record.

During the preparation of this paper, we re-examined the description and, remotely, the type specimen of H. signata and were able to confirm its identity, as well as its distinctiveness from H. edulis . Ludwig (1875) clearly describes the unusual and unique colour pattern of this species, a pattern that, albeit faded, is still discernible in the lectotype today. Ludwig also illustrates the body wall tables, which are distinctly narrower than those of H. edulis . Finally, the identity of the species is also suggested on biogeographical grounds. Only two species of Holothuria (Halodeima) are known from French Polynesia, the type locality of H. signata : H. signata and the quite different H. atra . As far as we know H. edulis does not reach this area. One of us ( GP) has studied the holothurians of French Polynesia on several occasions over the past 25 years, including a 2-month survey in 2006 of Moorea I. (just 17 km from Tahiti), and has never seen H. edulis in the area. In contrast H. signata is fairly common there.

Holothuria signata is a relatively small species that conceals itself during the day within the reef matrix (including under rocks), emerging at night to feed on the reef surface. Its habit thus contrasts markedly with that of H. edulis , a dayactive, exposed animal that prefers pockets of soft sediments within the reef, often in a lagoonal setting. The 2 species are immediately distinguishable on colour pattern, the shape of table ossicles, as well as genetically. Holothuria signata also does not grow as large as H. edulis .

Figures

Figure 4. Bayesian phylogram of species studied together with selected outgroup taxa, with posterior probability values (10 million generations, GTR-I-Gamma, and uninformative prior) above branches, and parsimony bootstrap values (100 replicates) below.

Figure 8. a, preserved lectotype of Holothuria signata Ludwig, 1875 from Tahiti, French Polynesia (100 mm long in Ludwig, 1875; UH E2638; photo by Peter Stiewe). b, live H. (Halodeima) signata, from Moorea, French Polynesia (UF E4986; photo by Gustav Paulay). c, close-up of preserved lectotype of H. signata (UH E2638). d, close-up of live H. (Halodeima) signata (UF E4986).

Figure 9. Holothuria (Halodeima) signata Ludwig, 1875 (SEM of ossicles from UF 173). A, dorsal body wall; B, ventral body wall; C, anal body wall; D, papillae; E, tube feet; F, tentacles; G, madreporite.