It is considered highly dangerous, as it is capable of delivering extremely painful and medically significant stings when touched.

Its common name is derived from its numerous and distinctively flower-like pedicellariae, which are usually pinkish-white to yellowish-white in color with a central purple dot.

The rigid "shell" (test) is a variegated deep red and gray in color, though in rare cases it may be greenish to light purple.

It was originally described as Echinus pileolus by the French naturalist Jean-Baptiste Lamarck in 1816, in the second book of his Histoire naturelle des animaux sans vertèbres series.

[6][7] It is also known as tapumiti in Samoan;[8] tehe-tehe batu in Sinama and Tausug;[9] rappa-uni (ラッパウニ) or dokugaze (毒ガゼ) in Japanese;[1][10] and lǎbā dú jí hǎi dǎn (喇叭毒棘海膽) in Chinese.

[12][13] Like most echinoderms, the body of adult flower urchins is equally divided into identical segments around a central axis in multiples of five (pentaradial symmetry).

The tube feet are individually composed of a thin muscular stalk (podia) tipped with a small suction cup (ampulla).

Surrounding the anal opening are five smaller holes (the genital pores) which are directly connected to the gonads inside the body cavity.

One of the few organisms capable of consuming flower urchins with no apparent adverse effects is the predatory corallimorph Paracorynactis hoplites.

They cling to the spines on the outer surface of the sea urchin test using their highly specialized walking legs.

Because their ability to walk on substrates like sand is impaired, zebra crabs spend their entire benthic life stage attached to sea urchins, switching between hosts only during the mating season.

The area of the test they inhabit is characteristically smooth; completely devoid of spines, pedicellariae, tube feet, and even epidermis.

It is unknown if they physically destroy and/or consume these appendages or if they use other stimuli to induce the host sea urchins to autotomize.

In addition to the visible external damage, a 1974 study also observed abnormal behavior and coloration among infected sea urchins.

Males and females release free-swimming gametes (eggs and sperm) directly into the water currents in mass spawning events.

[38] In Okinawa, Japan, a 1994 study identified the spawning season of flower urchins as occurring in winter, at the same time as the closely related and sympatric Toxopneustes elegans.

[38] Another study published in 2013 did not find any obvious correlation between lunar and tidal cycles to the mass spawning behavior of the flower urchin populations in southern Taiwan.

[29][34][41] Flower urchins are usually found almost completely covered in objects like dead coral fragments, shells, seaweed, and rocks.

It was found to interfere with the transmission of signals at nerve endings as well as cause hemagglutination (clumping of the red blood cells).

At low doses to mice, pedoxin was found to result in markedly lower body temperatures, muscle relaxation, sedation, and anesthetic coma.

The claws of the pedicellariae may also break off from their stalks and adhere to the point of contact, retaining the ability to continually inject venom for several hours.

[21] In 1930, the Japanese marine biologist Tsutomu Fujiwara accidentally envenomated himself with seven or eight flower urchin pedicellariae while working in a fishing boat.

He described his experience in a paper published in 1935:[34][52][53] On June 26, 1930, while I was working on a fishing boat on the coast of Tsutajima in Saganoseki, I scooped up with my bare hand an individual of the sea-urchin which had been carried up by a diver with a fishing implement on the water surface from the sea-bottom about 20 fathoms in depth, and I transferred the sea-urchin into a small tank in the boat.

After a while, I experienced a faint giddiness, difficulty of respiration, paralysis of the lips, tongue and eyelids, relaxation of muscles in the limbs, was hardly able to speak or control my facial expression, and felt almost as if I were going to die.

[54] One such report was the purported drowning of a pearl diver after being rendered unconscious from accidental contact with a flower urchin.

The severe debilitating pain of the flower urchin sting compounded by muscular paralysis, breathing problems, numbness, and disorientation can result in accidental drowning among divers and swimmers.

[9] In Okinawa, fishermen observed numerous individuals of the predatory crown-of-thorns starfish (Acanthaster planci) gathering around the remains of the internal organs of flower urchins.

[63] A follow-up study by Japanese researchers in 2001 confirmed that the viscera of flower urchins could indeed attract crown-of-thorns starfish in both aquarium and open sea experiments.

The authors believe that this discovery may be used to augment population control measures of the crown-of-thorns starfish, which are highly destructive to coral reefs.