Platydoris cf. formosa (Alder & Hancock, 1864)

Mehrotra, Rahul, A. Caballer Gutierrez, Manuel, M. Scott, Chad, Arnold, Spencer, Monchanin, Coline, Viyakarn, Voranop & Chavanich, Suchana, 2021, An updated inventory of sea slugs from Koh Tao, Thailand, with notes on their ecology and a dramatic biodiversity increase for Thai waters, ZooKeys 1042, pp. 73-188 : 73

* Platydoris cf. formosa (Alder & Hancock, 1864) Figure 12K, L

Material examined.

One specimen 20 mm, CA; two specimens 35-40 mm, SI.

Ecology.

Among rubble at the coral reef edge. Depth 8-16 m.

Distribution.

Platydoris formosa is known from Australia ( Nimbs and Smith 2016), Tanzania, India, Indonesia, the Philippines, Samoa, New Caledonia, and Hawaii ( Gosliner et al. 2008). Platydoris cinereobranchiata Dorgan et al., 2002 is known from the Philippines, Australia, the Solomon Islands ( Gosliner et al. 2008), and Indonesia ( Yonow 2011). Neither species has yet been documented in Thai waters.

Remarks.

Externally, the specimens bear similarity to Platydoris formosa , as detailed by Dorgan et al. (2002) although differ in numerous ways. The rhinophores of the present species are yellow to pale brown, sometimes with red spots near the apex, with no black spots between them. Rhinophores have 33-35 lamellae. The gills are grey with dark brownish red lines running along the rachises, with no black spots anterior to the gill sheath. A white ring is present around the rims of the rhinophore and gill sheaths. Most of the caryophyllidia covering the dorsum are a dark reddish colour with a few white patches randomly distributed. Larger bright red patches are more numerous and also randomly distributed across the dorsal surface. Ventrally white with large red spots which become more diffuse and concentrated towards the foot. Based on these characteristics, it appears that the specimens from Koh Tao bear characteristics of both P. formosa and P. cinereobranchiata .

Figures

Figure 12. A Atagema intecta 25 mm (photograph by Nick Tringham) B Atagema spongiosa 95 mm C Atagema sp. 32 mm D Carminodoris cf. bifurcata 9 mm E Discodoris cebuensis 30 mm (photograph by Kirsty Magson) F Discodoris boholiensis 55 mm G Halgerda bacalusia (unknown size, photograph by Stephan Pelletier) H Jorunna funebris 87 mm I Jorunna sp. 10 mm J Peltodoris murrea 30 mm K, L Platydoris cf. formosa 35 mm, dorsal and ventral views (photographs by Kirsty Magson).