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 * Migaya sp. Figure 8A Material examined. One specimen 3 mm , LB. Ecology. In soft sediment habitats outside the coral reef. Depth 24 m. Distribution. Currently known only from the Gulf of Thailand, documented here for the first time. Remarks. Ortea Rato et al. (2014) described the genus Migaya to hold all the Caribbean and Indo-Pacific cephalaspideans that were found to cluster (subclade B.2.) with Aglaja felis Er. Marcus & Ev. Marcus, 1970 in the molecular phylogeny inferred by Camacho-Garcia et al. (2013) . These authors transferred A. felis to the genus Nakamigawaia Kuroda & Habe, 1961 based on the apparently wide distribution of A. felis in the Indo-Pacific, assuming that they could only belong to the Japanese genus Nakamigawaia because of the similarities in their external morphology and colouration, but they did not include representatives of the type species of the genus, N. spiralis Kuroda & Habe, 1961, in their study, nor any other co-generic species coming from Japan. Ortea Rato et al. (2014) compared the shells N. spiralis with those of A. felis in the context of a wide-range shell comparison including all the Aglajidae , and concluded that both species belonged to different genera, consequently describing the genus Migaya . Afterwards, Zamora-Silva and Malaquias (2018) published a new molecular phylogeny based on a wider taxonomical sampling within the Aglajidae in which they synonymised the genus Migaya and transferred A. felis to the genus Nakamigawaia . Again, these authors did not include representatives of N. spiralis from Japan, but similar species from Australia and Papua New Guinea, without checking their internal anatomies. For these reasons, given the high rate of endemicity of the Japanese sea slugs, and after the study of the shell of the specimen from Thailand (bearing a similar shell to that of M. felis ), we prefer to maintain the genus Migaya until representatives of N. spiralis from Japan are sequenced and compared in a phylogenetic context. Figure 8. A Migaya sp. 3 mm B Siphopteron makisig 3 mm C Siphopteron sp. 3 mm (photograph by Will Malsukum) D Philine orca 3 mm E Aplysia kurodai 30 mm (photograph by Geoffrey Chamayou) F Aplysia nigrocincta 9 mm G Bursatella cf. ocelligera 65 mm (photograph by Elouise Haskin) H Stylocheilus longicauda 45 mm (photograph by Kirsty Magson) I Stylocheilus striatus 29 mm J Berthella cf. caledonica 10 mm K Berthella martensi 60 mm (photograph by Paddy Steele) L Pleurobranchus forskalii 130 mm (photograph by Tine Kvamme).