Chelidonura cf. castanea Yonow, 1994

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

* Chelidonura cf. castanea Yonow, 1994 Figure 7E

Material examined.

Two specimens 62-74 mm, TT.

Ecology.

In soft sediment habitats outside the coral reef. Depth 22-26 m.

Distribution.

Chelidonura castanea is currently known only from the Maldives ( Yonow 1994). Unconfirmed sightings have also been made from Mozambique and Myanmar ( iNaturalist 2011; TSS 2020). Here representing a first record for Thai waters (but see below).

Remarks.

Specimens from Koh Tao differ from those originally described by lacking orange spots across the dorsum, instead having only two tiny orange spots on the anterior portion of the head, on either side of the mouth. Additionally, the body is uniformly deep reddish brown with a thin white line on the upper margin of the cephalic shield. In the larger specimen (74 mm), both orange spots and the white line were markedly less distinct. The presence and absence of yellow/orange spots in such Aglajids has been shown to be an unreliable character for species delimitations ( Turner and Wilson 2012). To date, C. castanea is only known from the Indian Ocean; however, a distribution from Thailand was recorded, without reference to any source, by Gosliner et al. (2008) but omitted in later versions ( Gosliner et al. 2018). Therefore, we hereby provide details of a similar species from the Gulf of Thailand waters as a first record.

Figures

Figure 7. A Haloa sp. 5 mm B Lamprohaminoea ovalis 18 mm C L. ovalis 9 mm (photograph by Elouise Haskin) D L. ovalis 4 mm E Chelidonura cf. castanea 62 mm F Chelidonura punctata 32 and 34 mm G Niparaya sp. 4 mm H Philinopsis speciosa 18 mm I ' Philinopsis ' Philinopsis coronata 35 mm (photograph by Phannee Mccarthy) J Tubulophilinopsis lineolata 38 mm K Tubulophilinopsis pilsbryi 35 mm L Tubulophilinopsis reticulata 30 mm (photograph by Kirsty Magson).