Melibe sp.

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

Melibe sp. Figure 20E

Material examined.

Two specimens 15-22 mm, TT.

Ecology.

In soft sediment habitats beyond the coral reef, grazing upon the substrate. Depth 17-22 m.

Distribution.

Melibe engeli Risbec, 1937 is known across the Indo-Pacific including Mozambique ( Tibiriçá et al. 2017), the Red Sea ( Burghardt and Wägele 2014), the Philippines, Indonesia, Japan, New Caledonia, and Hawaii ( Gosliner et al. 2008). Melibe sp. 1 ( Gosliner et al. 2008) is known from Indonesia only. Recorded from Koh Tao as Melibe sp. 1 by Mehrotra and Scott (2016: fig. 3D, E).

Remarks.

Externally similar to Melibe engeli and Melibe sp. 1 ( Gosliner et al. 2008, 2018) in shape and some morphology, with similarities between the two also being noted by Yonow (2017). Specimens recorded from Koh Tao range in colour from near colourless to strongly golden brown, although always at least slightly transparent. The body is covered in numerous small papillae, the oral hood is able to stretch to at least half of the length of the remaining body, which have four or five pairs of cerata. Cerata are mostly ovoid to cylindrical in shape, terminating in numerous large pointed white papillae. In smaller individuals, two papillae may dominate the apex of each ceras giving them a bifurcate appearance. Most intriguingly and substantially different from the morphology of M. engeli are the rhinophore sheaths which lack the ‘sail-like’ appendage but instead have a single long and thin almost ‘whip-like’ extension. While the overall body shape of M. engeli has been shown to go through numerous changes during development ( Burghardt and Wägele 2014), the specimens from Koh Tao do not entirely match M. engeli .

Figures

Figure 20. A Bornella stellifera 31 mm B Lomanotus vermiformis 25 mm C Scyllaea fulva 45 mm D Melibe viridis 97 mm E Melibe sp. 22 mm F Eubranchus ocellatus 22 mm G Eubranchus sp. 7 mm H Coryphellina exoptata 15 mm (photograph by Tine Kvamme) I, J Coryphellina cf. lotos variants 40 mm (I) and 35 mm (J) K Samla bicolor 12 mm L Phestilla fuscostriata 15 mm.