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 * Myja cf. longicornis Bergh, 1896 Figure 18A Material examined. One specimen GR, 9 mm . Ecology. Found exclusively on its prey hydroid Pennaria disticha (Goldfuss, 1820) uncommonly found in both coral reef and deeper soft sediment habitats. Depth 8-25 m. Distribution. Myja longicornis is known from Indonesia ( Bergh 1896 ), Australia ( Nimbs and Smith 2016 ), Japan, and Papua New Guinea ( Gosliner et al. 2008 ). A similar species Myja cf. longicornis was recently documented from the Gulf of Thailand ( Martynov et al. 2019 ). Remarks. This genus was recently reviewed and expanded based on specimens from Japan and the Gulf of Thailand ( Martynov et al. 2019 ). In that study, authors concluded that the studied specimens from the Gulf of Thailand have a close resemblance to the description of M. longicornis by Bergh, with some internal and external differences that would require examination of specimens from the type locality of Ambon. The single specimen found at Koh Tao closely resembles other specimens found in the Gulf of Thailand, and thus its species designation remains unresolved in the absence of contemporary studies of the genus from closer to the type locality. Figure 18. A Myja cf. longicornis 9 mm (photograph by Phannee Mccarthy) B, C Noumeaella sp. 1 5 mm D, E Noumeaella sp. 2 5 mm (photographs by Tony Myshlyaev) F Phidiana militaris 35 mm (photograph by Pau Urgell Plaza) G Phidiana sp. 7 mm H Phyllodesmium magnum 30 mm I Phyllodesmium cf. magnum 35 mm (photograph by Pau Urgell Plaza) J Phyllodesmium opalescens 35 mm, (photograph by Guillaume Gandoin) K Phyllodesmium sp. 55 mm (photograph by Pau Urgell Plaza) L Armina occulta 65 mm.