Alex Mustard / Sacoglossan sea slug (Costasiella sp.) tiny <5mm along, on algae. Anilao, Batangas marine protected area, Luzon, Philippines. Verde Island Passages, Tropical West Pacific Ocean.

Pascal Kobeh / Lined Thuridilla / Orange-edged sapsucking nudibranch / sea slug (Thuridilla lineolata), Sulu sea, Philippines

Linda Pitkin / Nudibranch (Thuridilla lineolata) Sangeang, off Sumbawa, Indonesia.

Georgette Douwma / Sea slug (Plakobranchus ocellatus) on sand. Raja Ampat, West Papua, Indonesia.

Alex Mustard / Tiny (7mm) herbivorous sap-sucking seaslug (Costasiella kuroshimae) crawling over piece of algae next to its circular egg ribbon. Seraya, Bali, Indonesia. Java Sea

Alex Mustard / Details of ruffled mantle extensions on the Sacoglossan sea slug (Tridachia crispata) These also contain the chloroplasts of their algae food, that continue to photosynthesise inside the mollusc and p...

Franco Banfi / Sap sucking seaslug (Plakobranchus ocellatus) Blue water mangrove, Raja Ampat, Irian Jaya, West Papua, Indonesia, Pacific Ocean

Juergen Freund / Seaslugs (Plakobranchus ocellatus) Raja Ampat, West Papua, Indonesia

Juergen Freund / Sap sucking sea slug (Elysia ornata) New Ireland, Papua New Guinea

Alex Mustard / Seaslug (Elysia sp.) portrait, Raja Ampat, West Papua, Pacific Ocean.

Alex Mustard / Sap-sucking slug / Shaun the sheep slug (Costasiella kuroshimae) crawling across algae (Avrainvillea sp.) on the seabed, Bitung, North Sulawesi, Indonesia, Lembeh Strait.

Alex Mustard / Sap-sucking slug / Shaun the sheep slug (Costasiella kuroshimae) crawling across green algae (Avrainvillea sp.) on seabed, Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.