An updated inventory of sea slugs from Koh Tao, Thailand, with notes on their ecology and a dramatic biodiversity increase for Thai waters Author Mehrotra, Rahul Reef Biology Research Group. Department of Marine Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand & Aow Thai Marine Ecology Center, Koh Mun Nai, Kram, Klaeng District, Rayong 21110, Thailand Author A. Caballer Gutierrez, Manuel American University of Paris, Department of Computer Science Math and Environmental Science, 6 rue du Colonel Combes, 75007 Paris, France & Museum national d'Histoire naturelle, 55 rue de Buffon, 75005 Paris, France Author M. Scott, Chad Conservation Diver. 7321 Timber Trail Road, Evergreen, Colorado, 80439, USA Author Arnold, Spencer Conservation Diver. 7321 Timber Trail Road, Evergreen, Colorado, 80439, USA Author Monchanin, Coline Aow Thai Marine Ecology Center, Koh Mun Nai, Kram, Klaeng District, Rayong 21110, Thailand & Research Center on Animal Cognition (CRCA), Center for Integrative Biology (CBI); CNRS, University Paul Sabatier, Toulouse III, France Author Viyakarn, Voranop https://orcid.org/0000-0002-2089-6356 Reef Biology Research Group. Department of Marine Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand Author Chavanich, Suchana https://orcid.org/0000-0001-6266-7300 Reef Biology Research Group. Department of Marine Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand & Center of Excellence for Marine Biotechnology, Department of Marine Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand suchana.c@chula.ac.th text ZooKeys 2021 2021-06-09 1042 73 188 http://dx.doi.org/10.3897/zookeys.1042.64474 journal article http://dx.doi.org/10.3897/zookeys.1042.64474 1313-2970-1042-73 9CF986D86A474E179A67245C78FB8AFD 1BB0A10A35DD5541850FDAFFDB7119C2 * Bursatella cf. ocelligera (Bergh, 1902) Figure 8G Material examined. One specimen 65 mm , SB. Ecology. In soft sediment habitats where it grazes on cyanobacterial mats on the benthos. Depth 18-25 m. Distribution. Bursatella ocelligera is known only from the Philippines ( Bazzicalupo et al. 2020 ) and the Gulf of Thailand ( Bergh 1902 ). Bursatella leachii is circumtropical ( Bazzicalupo et al. 2020 ) including Brazil ( Galvao Filho et al. 2015 ), Guadeloupe ( Ortea Rato et al. 2012 ), Spain ( Gonzalez-Wangueemert et al. 2014 ), Italy ( Travaglini and Crocetta 2019 ), Tunisia ( Zakhama-Sraieb 2009 ), Morocco ( Selfati et al. 2017 ), Ghana ( Bebbington 1969 ), Iran ( Rezai et al. 2016 ), India ( Sethi et al. 2015 ), Vietnam ( Martynov and Korshunova 2012 ), Australia ( Nimbs and Smith 2016 ), New Zealand ( Appleton et al. 2002 ), South Africa, Madagascar, and Hawaii ( Gosliner et al. 2008 ). Remarks. Eales and Engel (1935) synonymised all species of Bursatella into the single circumtropical species B. leachii . Recent evidence ( Bazzicalupo et al. 2020 ) has supported the presence of a second species, B. ocelligera , based on internal morphological differences such as an unarmed penis and supported by molecular data. This name was attributed to specimens described from the Gulf of Thailand by Bergh (1902) , who was the first to describe specimens with an unarmed penis. At present, there is no reliable way of discerning between the two species based on external morphology alone, and no available molecular data for specimens from the Gulf of Thailand. The internal anatomy of specimens from Koh Tao could not be investigated as part of the present study; however, the proximity to the type locality (Koh Chang) supports the need for comprehensive analyses of specimens from the Gulf of Thailand in particular, given the wide geographical range of B. leachii and the recent separation of other 'circumtropical' aplysiids.