Elysia cf. tomentosa Jensen, 1997

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

* Elysia cf. tomentosa Jensen, 1997 Figure 6B

Material examined.

One specimen 37 mm, CB.

Ecology.

In soft sediment habitats outside the coral reef. Observed feeding on a pinnate form of Caulerpa racemosa ( Forsskål) J. Agardh, 1873 which is found chiefly in soft sediment habitats beyond the coral reef. A more lenticular/globular form of the algae can be abundant in some shallow, degraded reef habitats; however, specimens from Koh Tao not been observed associated with this variety. Depth 12-20 m.

Distribution.

At present Elysia tomentosa is considered widespread across the Indo-Pacific (but see remarks below) including Iran ( Oladi et al. 2018), Madagascar, Malaysia ( Gosliner et al. 2008), Australia ( Jensen 1997), Réunion, India, Singapore, the Philippines, Indonesia, Japan, New Caledonia, and Hawaii ( Jensen 2015). Likely introduced to the Mediterranean alongside the highly invasive Caulerpa spp. ( Zenetos et al. 2010). Here representing a first record for Thai waters.

Remarks.

Recent molecular investigations have found that specimens recognised as Elysia tomentosa likely correspond to a complex of at least six species ( Krug et al. 2013). Discussions about the identity of specimens identifiable by black marginal lines along the parapodia and the similar species Elysia expansa ( O’Donoghue, 1924) have yet to be resolved ( Rudman 2009a; Krug et al. 2013). Additionally, Oladi et al. (2018) recently documented a species in this complex from Iran that matches a sequence of E. cf. tomentosa from the Andaman coast of Thailand, by Cornelius Swennen (GenBank accession number KC573755.1); however, no record of this species from the waters of Thailand has been found in the literature to date. Greater sampling efforts from more locations, with an assessment of internal characters, are needed to clarify this complex, including specimens from Koh Tao.

Figures

Figure 6. A Elysia pusilla 7 mm B Elysia cf. tomentosa 37 mm C Thuridilla cf. gracilis 18 mm D Colinatys sp. 3 mm E Aliculastrum cylindricum 30 mm F Aliculastrum debilis 28 mm G A. debilis (shell 12 mm) captured alive and predated by Haptosquilla cf. nefanda H Roxaniella multistriata 9 mm I Atys semistriatus 8 mm J Atys sp. 11 mm K Diniatys dentifer 5 mm L Diniatys dubius 6 mm.