Hypselodoris jacksoni, Wilson, Nerida G. & Willan, Richard C., 2007

Wilson, Nerida G. & Willan, Richard C., 2007, Hypselodoris jacksoni, a new species from the south-western Pacific Ocean (Nudibranchia: Chromodorididae), with a discussion on intraspecific variation in mantle glands in Chromodoris willani Rudman, 1982, Zootaxa 1549, pp. 29-42 : 30-39

Hypselodoris jacksoni sp. nov.

( Figs 2–5 )

Chromodoris geometrica Coleman 1981: 32 , 98 (misidentification; not Risbec, 1928). Chromodoris cf. geometrica Ellis 2001: 32 (2) (misidentification; not Risbec, 1928). Hypselodoris sp. Coleman, 2001: 82; Wilson, 2002: 296.

Hypselodoris sp 1. Cobb and Willan, 2006: 165.

Material Examined (the number of individuals examined from each locality is given in brackets at the end of each entry):

Holotype. “Shag Rocks” dive site, off northeast coast North Stradbroke Island, Queensland, Australia, 27º26’S 153º32’E, 17 Jun. 1981, 7.5–8 m depth ( NTM P23398).

Paratype. “Hanging Gardens” dive site, Gneering Shoals, off Mooloolaba, Queensland, Australia, 26º46’S 153º03’E, 4 Sept. 1999, 18.5 m depth (QM MO.71813).

Other material (non-type). AUSTRALIA: QUEENSLAND: southwest side Wolf Rock, off Double Island Point, 25º54’S 153º12’E, 15 m, 24 Oct. 1982, NTM P23376 (2). west side Mudjimba Island, off Maroochydore, 26º39’S 153º07’E, 10 m, 12 Jul. 1982 (1—photo only). South side Mudjimba Island, off Maroochydore, 26º39’S 153º07’E, 6 m, 7 Jul. 1990, NTM P23387 (1). 200 m off Point Cartwright, 26º42’S 153º08’E, 10 m, 26 Oct. 1980, NTM P23399 (1). Northeast Outer Gneering Shoals, off Mooloolaba, 26º46’S 153º03’E, 15–18 m, 25 Aug. 1984 (4—photos only). Inner Gneering Shoals, off Mooloolaba, 26º46’S 153º03’E, 8–15 m, 10 Jul. 1982, NTM P23390 (5); 10.6 m, 13 Oct 1984, NTM P23388 (1); 8 m, 25 Aug. 2000, SAM D19271 (2); 8 m, 3 Sep. 2000, SAM D19272 (1); 14.5–18.5 m, 6 Oct. 1980 (1—photo only); 14.5 m, 9 Jan. 2000, SAM D19273 (1). “Murphy’s Shoal” dive site, off Mooloolaba, 26º46’S 153º03’E, 18 m, 11 Jul. 1982, NTM P23389 (2). Northwest side Flinders Reef, northeast Cape Moreton, 26º58’S 153º30’E, 9– 12.5 m, 12 Nov. 1983, NTM P23394 (1); 9–10.6 m, 31 Mar 1984, NTM P23395 (1). Southwest side Flinders Reef, northeast Cape Moreton, 26º58’S 153º30’E, 9 m, 23 Aug. 1980, NTM P23376 (2). Brennan Shoal, northeast Cape Moreton, 27º02’S 153º28’E, 17–18 m, 27 Aug. 1982, NTM P23397 (3). Smith Reef, northeast Cape Moreton, 27º02’S 153º28’E, 9–12 m, 23 Aug. 1980, NTM P23385 (2). “The Wrecks” dive site, Tangalooma, northwest coast Moreton Island, 27º12’S 153º22’E, 2–7.5 m, 26 May 1981, NTM P23381 (3); 2 m, 9 Jun. 1982, NTM P23392 (1); 6 m, 12 Nov. 1983, NTM P23391 (1). “Crayfish Rocks” dive site, off southeast coast Moreton Island, 27º20’S 153º28’E, 13.5 m, 22 Sep. 1981, NTM (1). Amity Point, northwest coast North Stradbroke Island, 27º24’S 153º26’E, 7.5 m, 13 Jul. 1980, NTM (1); 6 m, 5 Aug. 1980, NTM (1). “Shag Rocks” dive site, off northeast coast North Stradbroke Island, 27º24’S 153º32’E, 7.5–8 m, 19 Nov. 1985, NTM P23386 (1). Myora, west coast North Stradbroke Island, 27º29’S 153º25’E, 2–3 m, Jun. 1980, NTM (1). NEW SOUTH WALES: Julian Rocks, off Cape Byron, 28º36’S 153º45’E, 18 m, 29 Mar. 1975, NMV F30558; 30 Mar. 1975, AMPI no. 491 (1—photo only). South West Solitary Island, north Coffs Harbour, 30º10’S 153º14’E, 18 m, May 1988 (1—photo only). Split Solitary Island, north Coffs Harbour, 30º15’S 153º11’E, 13.5 m, 1986 (1—photo only). South West Rocks, July 2000 (1—photo only). LORD HOWE ISLAND: Malabar, 28º00’S 159º00’E, 10–15 m, 29 Nov. 1979, AMPI no. 813 (1—photo only); 30 Nov. 1979, AMPI no. 824 (1). Roach Island, 28º00’S 159º00’E, 25 m, 22 Feb. 1979, AMPI no. 740 (1—photo only). Far Rocks, 28º00’S 159º00’E, 1 m, Feb. 1990 (1—photo only). NORFOLK ISLAND: 29º02’S 167º57’E, Nov. 1991 (1—photo only). “The Fireplace” dive site, Duncombe Bay, northeast coast Norfolk Island, 29º02’S 167º57’E, 15 m, 22 Mar. 1992, NTM (2). West “The Cord” dive site, Duncombe Bay, northeast coast Norfolk Island, 29º02’S 167º57’E, 15 m, Jun. 1991, NTM P23396 (2). West “Black Bank” dive site, northwest corner Norfolk Island, 29º02’S 167º57’E, 16 m, Aug. 1991, NTM (2—photos only). Sail Rock, north coast Philip Island, 29º60’S 167º60’E, 12–22 m, Jun. 1991, NTM P23393 (1); 21–22 m, 4 Aug. 1991, NTM P23377 (2).

Etymology: The specific epithet honours Daniel Jackson, of Melbourne, Australia, for providing much field assistance and support to NGW.

Geographic range and depth range: Hypselodoris jacksoni occurs on the eastern coast of Australia from Double Island Point (southern Queensland) to South West Rocks (central New South Wales) ( Fig. 1 ). It also occurs at Norfolk and Lord Howe Islands. Although specimens have been collected from the intertidal zone to 25 m in depth, it is predominantly a subtidal species.

External morphology ( Fig. 2 ): Length of adult 18–39 mm (n = 36) [One exceptionally large specimen, measuring 65 mm alive, was found at Mooloolaba after this description was completed. It was not collected, and so is not included under Material Examined, but its size is mentioned here for the record.] Body very soft, elongate, relatively high, with relatively narrow overlap along the sides. Foot elongate, rounded and expanded slightly anteriorly, projecting a considerable distance at rear of mantle when animal crawling (foot approx. half length of mantle), tip pointed. Head with cylindrical oral tentacles flanking mouth; oral tentacles never extend beyond mantle edge in life. Mantle elongate, widening anteriorly, margins parallel laterally, rounded posteriorly, entirely smooth. Sheath of rhinophoral pocket slightly raised above surrounding mantle notum, rim entirely smooth. Sheath of branchial pocket conical, well elevated above surrounding mantle notum, rim entirely smooth. Transparent, spherical, subdermal glands present typically in single row around entire margin of mantle, largest and most closely-packed at rear behind gills ( Fig. 3 A). Paratype with double row of mantle glands posteriorly ( Fig. 3 B). Rhinophores tall, straight, slightly outward pointing when extended; clavus lamellate, 2/3 height of stalk. Gills 7–9 in number (mean = 7.8, n = 26), simply pinnate, triangular in cross section, forming a continuous circle around anus, held vertically erect when extended. Neither mantle margin nor gills observed to move rhythmically in life.

Colouration ( Fig. 2 ): Background colour of mantle and body opaque white, sometimes with a greyish tinge. Ill-defined, translucent patch present on mantle behind each rhinophore, but eyespots not visible through notum. Mantle bordered by a thin, orange-red band, interrupted in some specimens but not expanded around anterior end. Opaque white submarginal band most pronounced at anterior and posterior regions of mantle dorsum abutting orange-red band. Laterally, this white band extends irregularly inward to form smooth convex hemispherical patches. Central and medio-lateral sections of mantle bear reticulum of intense brown or black reticulum arranged around three principal longitudinal lines. Edges of reticulum extend to touch orange-red marginal band laterally. Spaces within reticulum containing (usually) one, or few, chrome yellow spots or specks. Purple patch present on undersurface of anterior end of mantle. Reticulate pattern maintained on sides of body, but with horizontal dark purple or black lines predominating. Dorsal side of foot with narrow, translucent marginal band and slightly wider opaque white submarginal band. Central section of tail dorsum with black reticulum similar to mantle dorsum. Oral tentacles white. Rim of rhinophoral pocket bordered with thin orange-red band followed by wider black band. Coloration of branchial sheath not differentiated from surrounding mantle notum. Rhinophores uniformly dark orange-red to orange-brown with white apex. Outer face of gill rachis orange-red or orange-brown, most frequently with one white spot near base on each pinna. Other patterns observed include a dash, a long stripe, 1–5 spots, or no markings. Inner face of rachis opaque white with thin orange-red to orange-brown border.

Radula and jaws ( Fig. 4 ): Muscular portion of buccal mass almost as long as oral tube (NTM P23391 and NTM P23392). Radular formula 53 x 86.0.86 (SAM D19271): 62 x 93.0.93 (NTM P23391), 60 x 86.0.86 (NTM P23392). Midline of radula smooth ( Fig. 4 A), without rachidian tooth. Innermost lateral tooth ( Fig. 4 A) with narrow, strongly recurved cusp bearing single strong denticle on outer side and, correspondingly, single denticle (two denticles in some rows; second denticle arrowed in Fig. 4 A) on inner side. Middle ( Fig. 4 B) and outer lateral teeth bicuspid ( Fig. 4 C), progressively smaller, erect, cusp progressively more rounded, bearing single relatively weak denticle on outer side but no denticle on inner side. Jaws composed of multiple, erect, cuticularised rodlets ( Fig. 4 D). Shaft of rodlet elongate. Cusp slightly curved, sharp-pointed. Rodlet circular in section, without lateral flange(s), all undivided (i.e., none bifid).

Reproductive System ( Fig. 5 ): Triaulic. Ampulla long and curved, dividing distally into long, wide, convoluted prostate gland and short oviduct. Prostatic section of vas deferens narrowing into long, narrow, convoluted ejaculatory portion which terminates in slightly bulbous penial sac. Penial sac relatively small, slightly more expanded than immediately proximal section of vas deferens. Uterine duct long, narrow, entering female gland mass below entrance of oviduct, but close to genital opening. Female gland mass partly overlaid on one side by large, lobulate vestibular gland. Vaginal duct elongate, widest at genital opening, apparently neither thickened nor muscular. Bursa copulatrix large, spherical. Receptaculum seminis minute (much smaller than bursa), elongate and pyriform; inserting onto vaginal duct by short duct just below bursa.

Spawn and Development: Hypselodoris jacksoni lays an upright, crenulated egg mass. Individual egg masses vary in colour, from dark orange-red (Wilson 2002: p. 296) to pale pink ( Cobb & Willan 2006). The larvae show lecithotrophic development and hatch after 9–11 days at 20–22ºC (Wilson 2002).

Remarks: Even though the scope and phylogeny of the family Chromodorididae remains uncertain ( Gosliner & Johnson 1999; Schrödl & Millen 2001; Wilson & Healy 2002), the understanding of a few constituent genera (i.e., Ceratosoma and Hypselodoris ) is approaching some level of systematic maturity founded on testable hypotheses ( Gosliner 1996; Gosliner & Johnson 1999; Johnson & Valdés 2001; Wilson & Lee 2005; Alejandrino & Valdés 2006). The new species described here fits unequivocally into Hypselodoris and conforms to the Indo-Pacific Ocean clade, as defined by Gosliner and Johnson (1999), by possessing a minute receptaculum seminis.

The coloration of Hypselodoris jacksoni is distinctive, but there is also great intraspecific variation present. The extent, intensity, and width of the dark reticulum on the mantle varies greatly, as does the number and intensity of the yellow spots contained within the spaces of the reticulum. The gills can have up to five spots on the outer face of each pinna, or none at all, or there can be a dash or a longer stripe. The width of the orange-red band does not alter anywhere around the edge of the mantle. Specimens from Norfolk Island ( Fig. 2 B) differ in pigmentation from those from the eastern Australian mainland. The Norfolk specimens have black lines composed of rows of closely spaced black spots instead of a reticulum on the central section of the mantle notum, and the white submarginal markings are broken into dashes in adults.

The degree of spotting on the outer face of the gill pinnae described above does not vary obviously with latitude ( Table 1). A single spot near the base of all the pinnae was by far most common state throughout the entire range, but this could vary from two to five spots, or a dash, or a stripe could rarely replace the spot/s. Three individuals examined even had different markings between different pinnae on their branchial plumes; for example one individual from Norfolk Island had two, three and five spots on adjacent gills. Intra-individual and inter-individual variation at any particular locality encompassed all possible phenotypes.

The radula of a specimen from Mooloolaba (SAM D19271), displayed intra-individual variation in the structure of the innermost lateral teeth. Teeth in most rows had a single denticle on the inner side (i.e., the side closest to the midline), but some had two denticles (see Fig. 4 A). This identifies similarities to H. krakatoa Gosliner and Johnson, 1999 , whose inner lateral teeth may have between one and seven denticles on the inner side ( Gosliner & Johnson 1999).

Locality Markings on outer side of gill rachis Wolf Rock, Queensland (stripe)

Gneering Shoals, Queensland (1); (none) Murphy’s Shoal, Queensland (1)

Point Cartwright, Queensland (1)

Flinders Reef, Queensland (1); (1); (1) Tangalooma, Queensland (dash)

Shag Rocks, Queensland (stripe)

Myora, Queensland (2,5)

SW Solitary Island, New South Wales (dash)

Norfolk Island (2); (3); (1,3); (2,3,5); (none) The specimen from Heron Island, Great Barrier Reef, described and figured by Marshall and Willan (1999) as Hypselodoris sp. 1 shows similarities in colouration to H. jacksoni . Both have a reticulate colour pattern and elevated branchial pocket. However, the species described by Marshall and Willan apparently differs in having a relatively more tight reticulate mantle pattern (more like H. reidi ), brown blotches submarginally, white spots (instead of stripes) on the inner faces of the branchial pinnae, and more numerous (10–12) gill pinnae. Currently, no preserved material of the Great Barrier Reef taxon is available for further comparison (but see Table 2 ).

Hypselodoris jacksoni shows many morphological similarities with a clade of Hypselodoris species with elevated branchial sheaths (e.g., H. krakatoa , H. reidi Gosliner & Johnson, 1999, H. regina Ev. & Er. Marcus, 1970 ). Hypselodoris reidi (presently known from the Philippines and Indonesia) has a network of yellowbrown pigment on the mantle that produces the effect of a tight reticulum similar to that we have seen in some individuals of H. jacksoni and the specimen from Heron Island. However, H. reidi is diagnosable by a thin pink marginal band on both the mantle and foot that widens around the anterior end of the mantle, the reticulum darkens into extensive blotches mid-centrally on the mantle and behind the gills, the tail has numerous white spots, the gill and rhinophoral colouration are the same as the general body. Additionally, there are white spots on the inner sides of the pinnae of the gills, and the inner denticle on the innermost lateral radular tooth is merely a small projection.

Hypselodoris krakatoa (presently known from the Philippines, Thailand, Malaysia, Japan, Indonesia and Papua New Guinea), although also showing great intraspecific colour variation, is quite different in external appearance, and possesses irregular brown patches on the dorsum with black lines and opaque white spots.

Similarly, H. regina (presently known from Madagascar, Tanzania, South Africa and Mozambique) has longitudinal black lines and a brown marginal band (which may be absent, or thin and pink), and is unlikely to be confused with H. jacksoni .

Marginal band on mantle Thin orange-red Broad brown patches, or thin pink Thin pink or absent Number of pinnae 7–9 7 7 There are also internal differences between the species. Hypselodoris jacksoni has a vaginal duct that is markedly wider than the penial duct, and the condition is reversed in H. krakatoa . Hypselodoris reidi has a bulbous penis but the vagina and lower portion of the ejaculatory duct are similar in width. Hypselodoris regina also has both ducts of equal width. There are also radular differences between the four species with H. jacksoni having 1–2 inner denticles on the inner lateral teeth, H. reidi and H. regina having one denticle and H. krakatoa having up to seven denticles.

Coleman (1981) misidentified Hypselodoris jacksoni as Chromodoris geometrica Risbec , presumably on the basis of the dark reticulate pattern on the mantle. But C. geometrica , which has a wide Indo-Pacific distribution, has a broader mantle with considerable overlap of the underlying foot, the rhinophores and gills are green or greenish-yellow distally, the branchial pocket is not elevated, and the radula is entirely different ( Yonow 1994, 2001). A distinctive characteristic of living C. geometrica (absent in H. jacksoni ) is that, when crawling, the anterior edge of the mantle is rhythmically raised and lowered.

Hypselodoris jacksoni sp. nov. shows some similarities to the enigmatic Doris elegans (type locality Tongatapu, Friendly Islands, Pacific Ocean) because of a similar body shape, raised branchial pocket and dorsal reticulate pattern. The holotype of D. elegans is in the MNHM ( Valdés & Héros 1998: 722). According to the original text by Quoy and Gaimard (1832), and original figure ( Quoy & Gaimard 1833), and redescription by Pruvot-Fol (1934), D. elegans is likely to be a chromodorid in the genus Hypselodoris , rather than Glossodoris as that genus is presently interpreted ( Rudman 1984), because of its high and slender body, relatively small mantle overlap above the foot and raised branchial pocket. However, compared to H. jacksoni , it shows differences in colour pattern and external morphology that negate synonymy. Doris elegans has a single zigzag median line on the mantle with thin diagonal lines radiating towards the margin like the secondary veins of a leaf. These diagonal lines produce the black reticulum with cream pustules occupying the spaces. The anterior end of the mantle has a black band with white embayments. The margin of the mantle has a cyclamen pink border (even though Pruvot-Fol 1934 stated it was "brown-purple") that is interrupted by pale spots. Pink areas also enclose regular, paired black rings with white interspaces. There is also a dark chain-like pattern on the sides of the foot. The base of the rhinophores is aquamarine blue. The rhinophoral clavus is uniformly cream with a flush of olive green. The six gill pinnae are white with black lateral pinnules. Hypselodoris jacksoni differs in pattern and colouration as described above, and possesses 7–9 gill pinnae. In view of these morphological differences, D. elegans and H. jacksoni do not appear to be the same species, and it seems likely that D. elegans has not been rediscovered since its original description.

Figures

FIGURE 1. Distribution map for Hypselodoris jacksoni sp. nov. Area shaded dark grey represents limits of observed occurrence.

FIGURE 2. Hypselodoris jacksoni sp. nov. (A) 35 mm, Split Solitary Island, northern New South Wales, Australia, 1986. Photo C. Buchanan. (B) 39 mm, “ The Fireplace ”, Duncombe Bay, Norfolk Island, 22 March 1992. Photo R. C. Willan. (C) upper animal 35 mm, Flinders Reef, southern Queensland, Australia, 12 November 1983; lower animal 33 mm, Tangalooma, southern Queensland, Australia, 12 November 1983. Photo R. C. Willan. (D) Holotype. NTM P 23398, 34 mm, “ Shag Rocks ”, North Stradbroke Island, southern Queensland, Australia, 17 June 1981. Photo R. C. Willan.

FIGURE 3. Hypselodoris jacksoni sp. nov. (A) Schematic arrangement of mantle glands; (B) Light micrograph of double row of posterior mantle glands (arrowed) (paratype QM, MO. 71813).

FIGURE 4. Hypselodoris jacksoni sp. nov. (SAM D 19271) SEMs of radula and jaws (A) Central section of radula; note two denticles on inner face of innermost lateral (arrowed); (B) Middle section of half row of radula showing middle lateral teeth; (C) Outer edge of half row of radula showing detail of outermost lateral teeth; (D) Inner face of jaw showing detail of mandibular rodlets.

FIGURE 5. Hypselodoris jacksoni sp. nov. (SAM D 19271) Reproductive system of a mature individual. Abbreviations: a, ampulla; bc, bursa copulatrix; ej, ejaculatory portion of vas deferens; fg, female gland mass; p, penial sac; pr, prostatic portion of vas deferens; rs, receptaculum seminis; u, uterine duct; v, vaginal duct; vg, vestibular gland.

Tables

TABLE 2. Comparison of congeners similar to Hypselodoris jacksoni sp. nov.

	H. jacksoni	H. krakatoa	H. reidi
Data source	Present study	Gosliner & Johnson 1999 Rudman 2000	Gosliner & Johnson 1999 Rudman 2002
Reticulate colour pattern	Present	Absent	Present
Stripe on inner face of gills	Present	Absent	Absent