Phyllidia coelestis Bergh, 1905
Phyllidia honloni Risbec, 1956: part of syntype series (although description and figures are of P. varicosa (see below in Non-Indonesian material, typical form).
Phyllidia varicosa Risbec, 1956: part of specimens (see below in Non-Indonesian material, typical form) (non varicosa Lamarck).
Phyllidia alia Yonow, 1984: 224, figs 6D, E, 7A, 8F, G.
Material.— typical form – RMNH.MOL.130163, Hatuhuran, Piru Bay, Ceram, 2-3 m depth, 28-30.xi.1997, 30 × 14 mm pres., leg. & photo H. Strack.
Non-Indonesian material.— typical form— RMNH.MOL.130158, NW of Orpheus Island, GBR, Australia, 8 m depth, 8.xi.1986, 35 × 15 mm pres., leg. & photo R. Cattaneo-Vietti (RC-V#17); Zoological Museum University Copenhagen, Kata Beach, Phuket, Thailand, 17.ii.1982, 24 × 10 mm pres.; WAM 64/89, Horsburgh Is., Cocos Keeling, 20.ii.1989, leg. C. Bryce, 25 × 7 mm; Negros Island, Philippines, 3.iii.1983, photos of two individuals, B. Picton (BEP PH/17 and BEP/54; 41 mm and 27 mm specimens AM C142660, 20 m depth); RMNH.MOL.130160, Panglao Island, S of Bohol, Philippines, x.2008, 18 × 7 m pres., leg. & photos J. Hinterkircher; Bohol, Philippines, iii.2004, photos of one individual, J. Hinterkircher; MNHN 16066 and MNHN 34206, Viet-Nam, Risbec, 1956 as P. varicosa; MNHN 1491.E34201 and MNHN 1502.E.34888, Viet-Nam, Risbec, 1956 as P. honloni syntypes.
Non-Indonesian material.— dark form – RMNH.MOL.130162, in Tridacna tank, Orpheus Island, GBR, Australia, 6.xi.1986, 60 × 30 mm (47 × 16 mm pres.), leg. & photo R. Cattaneo-Vietti (RC-V#03); WAM 1048-85, 4.5 km S of Vlaming Head Lighthouse, North West Cape, Western Australia, Stn. 3, 28.v.1981, leg. & photo Slack-Smith & C. Bryce, two specimens 35 × 16 mm pres. and 25 × 12 mm pres., curled; WAM 210-88, Robray Reef, Kimberley, Western Australia, 15.vii.1988, leg. & photo F. Wells & C. Bryce, two specimens 30 × 14 and 17 × 9 mm pres.
Fig. 15. Phyllidia coelestis (dark). a, right rhinophore of 60 mm specimen (RC-V#03); b, dissected 60 mm specimen (RC-V#03); c, dissected 35 mm specimen (WAM 1048-85). Phyllidia coelestis Bergh, 1905: 182, pl. 3 fig. 16 (Selayer, Indonesia); Lin, 1983: 152, pl. 1 fig. 5; Fahrner & Beck, 2000: 199, 202, pl 3 fig. 1; Yonow et al., 2002: 862, fig. 16b; Domínguez et al., 2007; 93, figs 1D, 4.
Description.— Typical colour form: the ground colour was blue white with two continuous black lines, a central interrupted black line, and a black U-shaped mark in front of the rhinophores (pl. 7 fig. 1) which may be incomplete as illustrated in fig. 14a. The tubercles were orange-tipped, and the remainder of the mantle skirt had scattered small tubercles and few black flecks. The orange rhinophores are curved and bear up to 19 lamellae (fig. 14b). The anus is located on the last or penultimate midline tubercle. Ventrally the anterior margin of the foot is deeply notched or concave, and the head has long oral tentacles which are grooved laterally and bear black pigment basally on their dorsal surfaces (fig. 14c-f).
The dark form is represented by several specimens with a central oval black region surrounded by a broad blue white border. The central region bears three rows of yellow tubercles with white bases (pl. 7 fig. 2). The edges of the central black area undulate and may form short rays extending into the blue white band bearing scattered pustules, some of the larger with yellow on their tips, and small black spots and patches. The yellow-orange rhinophores are squared with 20 tightly layered lamellae (fig. 15a). The anus is located on a posterior midline tubercle. Ventrally the foot is deeply concave anteriorly and can appear notched. The long oral tentacles have their dorsal surfaces pigmented with black (see fig. 15c) extending ventrally at the base of the tentacles.
Anatomically, the two forms also differ slightly: one noticeable feature is that there is more black pigment internally and on the oral tentacles and along the oral tube in the specimens with more black dorsally. Camera lucida figures of individual dissections are presented of both forms for comparison (fig. 14e, f and fig. 15b, c). In the typical form, the long oral tube bears a continuous black band posteriorly and/or spots and streaks along its length; in the dark form it is black with a concentrated band at the base. The pharyngeal bulb is approximately symmetrical and relatively smooth, less so in the darker specimens, and there are two large retractor muscles on either side, attached posteriorly and dorsally. In all specimens, the pharynx is thick and swollen, inserted posteriorly and centrally on the slightly flattened area of the bulb, and loops up, narrowing abruptly through the nerve ring, and then down to enter the digestive gland dorsally. The pericardium is located just below the centre of the digestive gland and the intestine originates beneath it; it can be traced for most of its length, disappearing beneath the digestive gland for part of its length.
Remarks.— This widely distributed and common Indo-West Pacific species is well known and has been recorded previously from Indonesia by Bergh (1905), Fahrner & Beck (2000), Tonozuka (2003), and Debelius & Kuiter (2007), all as the typical form.