Georgette Douwma / Kaleidoscopic image of Fire urchin (Asthenosoma varium). This sea urchin has venomous spines and is able to inflict painful stings. Komodo National Park, Indonesia.

David Hall / Brooks urchin shrimp (Allopontonia brooki), commensal among the venomous spines of Variable sea urchin (Asthenosoma varium). On sea floor, Komodo, Indonesia.

Shane Gross / Fire urchin (Asthenosoma varium) close-up detail showing the color and pattern of spines on its surface, off Alor, Indonesia

Alex Mustard / Pair of Coleman shrimps (Periclimenes colemani) make their home in a fire urchin (Asthenosoma varium). The female is larger. Fire urchins are one of the largest and most venomous urchins, their bright...

Alex Mustard / Brook's urchin shrimp (Allopontonia brooki) crawling over the surface of a fire urchin (Asthenosoma varium). Anilao, Batangas, Luzon, Philippines. Verde Island Passages, Tropical West Pacific Ocean.

Alex Mustard / Pair of Coleman shrimps (Periclimenes colemani) living in a fire urchin (Asthenosoma varium). The female is the larger shrimp. Fire urchins are one of the largest and most venomous urchins, their brig...

Alex Mustard / Coleman shrimp (Periclimenes colemani) close up, on a fire urchin (Asthenosoma varium). Anilao, Batangas, Luzon, Philippines. Verde Island Passages, Tropical West Pacific Ocean.

Franco Banfi / Urchin crabs (Zebrida adamsii) in Fire urchin (Asthenosoma varium) Raja Ampat, Irian Jaya, West Papua, Indonesia, Pacific Ocean

Alex Mustard / Orange painted frogfish (Antennarius pictus) resting between the venemous spines of a Fire urchin (Asthenosoma varium), Batangas marine protected area, Luzon, Philippines. Verde Island Passages, Pacif...

Alex Mustard / Coleman shrimp (Periclimenes colemani) female, with smaller male on left, living in a Fire urchin (Asthenosoma varium), Bitung, North Sulawesi, Indonesia, Lembeh Strait, Molucca Sea.

Georgette Douwma / Composite image of echinoderms on black background. top left to right: Pineapple sea cucumber (Thelenota ananas), Yellow sea cucumber (Colochirus robustus), Frianti's starfish (Nardoa frianti),...

Georgette Douwma / Composite image of echinoderms on black background. Top row from left: Featherstar (Crinoidea), Sea apple (Pseudocolochirus violaceus). Central row from left: Mosaic cushion star (Halityle regu...