Platydoris cruenta (Quoy & Gaimard, 1832)
Platydoris arrogans (Bergh): Bergh, 1890: 912, pl. 86, fig. 6 (Ambon, Indonesia).
Platydoris cruenta Bergh, 1905: 136, pl. 1 fig. 3; Marshall & Willan, 1999: 80, fig. 141; Dorgan et al., 2002: 80, figs 2f, 6b, 9, 10.
Material.— RMNH.MOL.131656, RBE Stn 27, Hutumuri, Leitimur, 2 m depth “nudibranch with spicules, between corals,” 17.xi.1990, two specimens 75 × 45 mm and 52 × 37 mm pres., leg. and photos M. Lavaleye 33-32/34; Derawan, East Borneo, iv.1997, photos of one individual J. Hinterkircher.
Non-Indonesian material.— Bohol, Philippines, iii.2004, photos of one individual, J. Hinterkircher; Bohol, Philippines, xi.2005, photos of one individual 60 mm, J. Hinterkircher.
Fig. 11. Platydoris cruenta. View of head and oral tentacles of 60 mm specimen.Doris cruenta Quoy & Gaimard, 1832: 260, pl. 18, figs 5-7.
Description.— Platydoris cruenta is characterized by a very oval dorsum covered with thin short wavy brown lines and bright red blotches (pl. 5 fig. 6). The rhinophores and gills are creamy white with brown axes; the rhinophores have 37-39 lamellae. The specimens, stiff and rough to the touch, are well preserved: the dorsum is identical to the photographs but only lacking the red blotches. Ventrally, the top of the foot is covered in fine wavy brown lines which extend partly onto both the hyponotum and the sole (pl. 6 fig. 1) where they are arranged more or less longitudinally; those on the top of the foot are arranged at right angles to the margin. The head and oral tentacles also have brown lines (fig. 11).
Remarks.— Platydoris cruenta is not common but it is an easily recognized species widely distributed in the tropical Pacific; it was previously recorded from Ambon by Bergh (1890). I disagree with Dorgan et al. (2002) that P. striata Kelaart (1858) is a synonym: it lacks the red blotches on the dorsum and there are probably internal differences, but it appears these were not compared. Additionally, their geographical distributions do not overlap: currently, P. striata is found only in the western Indian Ocean and Red Sea (Yonow, 2008) whilst P. cruenta is found only in the western Pacific. One does not see a gradual clinal change in morphology from east to west as in some species (e.g. Peltodoris atromaculata (Bergh) in the Mediterranean), nor do we see an overlapping of distributions of different colour patterns (e.g. Thuridilla gracilis (Risbec) across the Indo-West Pacific, as ratna (Marcus) and bayeri (Marcus)). As stated previously (Yonow et al., 2002), taxonomy is a tool for identifying and classifying animals: higher systematics is in a constant state of flux as a result, but combining species which clearly differ in geographical and/or morphological criteria is not helpful at this stage.