''Toxopneustes pileolus'', commonly known as the flower urchin, is a widespread and commonly encountered

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

sea urchin Sea urchins or urchins () are echinoderms in the class (biology), class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal zone to deep seas of . They typically have a globular body cove ...

from the

Indo-West Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the s ...

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

coral reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in group ...

seagrass Seagrasses are the only flowering plants which grow in marine (ocean), marine environments. There are about 60 species of fully marine seagrasses which belong to four Family (biology), families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and ...

beds, and rocky or sandy environments at depths of up to . It feeds on

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

, bryozoans, and organic detritus. Its common name is derived from its numerous and distinctively flower-like

pedicellaria A pedicellaria (: pedicellariae) is a small wrench- or claw-shaped appendage with movable jaws, called valves, commonly found on echinoderms (phylum Echinodermata), particularly in sea stars (class Asteroidea) and sea urchins (class Echinoidea). ...

e, which are usually pinkish-white to yellowish-white in color with a central purple dot. It possesses short and blunt spines, though these are commonly hidden beneath the pedicellariae. The rigid "shell" (

test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film) ...

) is a variegated deep red and gray in color, though in rare cases it may be greenish to light purple.

Taxonomy

''Toxopneustes pileolus'' is one of four species belonging to the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

'' Toxopneustes''. It belongs to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Toxopneustidae Toxopneustidae is a family of globular sea urchins in the class Echinoidea. Characteristics All Camarodonts have imperforate tubercles and compound ambulacral plates. In addition, the Toxopneustids are characterised by the peristome, or opening t ...

in the

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Camarodonta The Camarodonta are an Order (biology), order of globular sea urchins in the class (biology), class Echinoidea. The fossil record shows that camarodonts have been in existence since the Lower Cretaceous.French

naturalist Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is cal ...

Jean-Baptiste Lamarck Jean-Baptiste Pierre Antoine de Monet, chevalier de Lamarck (1 August 1744 – 18 December 1829), often known simply as Lamarck (; ), was a French naturalist, biologist, academic, and soldier. He was an early proponent of the idea that biologi ...

in 1816, in the second book of his ''Histoire naturelle des animaux sans vertèbres'' series. It was later used as the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

for the newly created genus ''Toxopneustes'' by the

Swiss American Swiss Americans are Americans of Swiss descent. Swiss emigration to America predates the formation of the United States, notably in connection with the persecution of Anabaptism during the Swiss Reformation and the formation of the Amish commu ...

biologist A biologist is a scientist who conducts research in biology. Biologists are interested in studying life on Earth, whether it is an individual Cell (biology), cell, a multicellular organism, or a Community (ecology), community of Biological inter ...

Louis Agassiz Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born American biologist and geologist who is recognized as a scholar of Earth's natural history. Spending his early life in Switzerland, he recei ...

. The generic name ''Toxopneustes'' literally means "poison breath", derived from

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

τοξικόν �άρμακον(''toksikón hármakon', "arrow oison) and πνευστος (''pneustos'', "breath"). The specific name ''pileolus'' means "little cap" or "skullcap", from

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

'' pileus'', a kind of brimless conical felt cap. In English, ''Toxopneustes pileolus'' is most widely known as the "flower urchin". It is also sometimes known under various other common names, including "trumpet sea urchin", "flower tip urchin", "felt cap sea urchin", and "poison claw sea urchin". In the seashell collecting trade, ''Toxopneustes pileolus'' is known as the "mushroom urchin", due to their spineless empty shells (

tests Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film) ...

) resembling the caps of

mushrooms A mushroom or toadstool is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or another food source. ''Toadstool'' generally refers to a poisonous mushroom. The standard for the name "mushroom" is ...

. It is also known as ''tapumiti'' in Samoan; ''tehe-tehe batu'' in Sinama and Tausug; ''rappa-uni'' (ラッパウニ) or ''dokugaze'' (毒ガゼ) in

Japanese Japanese may refer to: * Something from or related to Japan, an island country in East Asia * Japanese language, spoken mainly in Japan * Japanese people, the ethnic group that identifies with Japan through ancestry or culture ** Japanese diaspor ...

; and ''lǎbā dú jí hǎi dǎn'' (喇叭毒棘海膽) in Chinese.

Description

Flower urchins are relatively large sea urchins. They can reach a maximum diameter of around . Like most

echinoderm An echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as ...

s, the body of adult flower urchins is equally divided into identical segments around a central axis in multiples of five (

pentaradial symmetry Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, the face of a human being has a plane of symme ...

). The rigid "shell" (

) has five interambulacral segments separated from each other by five

ambulacral Ambulacral is a term typically used in the context of anatomical parts of the phylum Echinodermata or class Asteroidea and Edrioasteroidea. Echinoderms can have ambulacral parts that include ossicles, plates, spines, and suckers. For example, sea ...

segments, each of them are composed of smaller regularly interlocking plates. It is overlaid by a thin layer of skin in living individuals. The test is variegated in coloration, usually deep red and grey, though there are rare instances of green and pale purple. Each ambulacral segment is ornamented by a large purple zigzag pattern running along its length. Two rows of

tube feet Tube or tubes may refer to: * Tube (2003 film), ''Tube'' (2003 film), a 2003 Korean film * "Tubes" (Peter Dale), performer on the Soccer AM#Tubes, Soccer AM television show * Tube (band), a Japanese rock band * Tube & Berger, the alias of dance/e ...

emerge from the grooves on either side of each of the ambulacral segments (for a total of ten rows). The tube feet are individually composed of a thin muscular stalk (podia) tipped with a small suction cup (ampulla). The

mouth A mouth also referred to as the oral is the body orifice through which many animals ingest food and animal communication#Auditory, vocalize. The body cavity immediately behind the mouth opening, known as the oral cavity (or in Latin), is also t ...

is centrally located in the bottom (oral) surface of the test. It is surrounded by a ring of small plates overlaid by softer tissue known as the

peristome Peristome (from the Greek language, Greek ''peri'', meaning 'around' or 'about', and ''stoma'', 'mouth') is an anatomical feature that surrounds an opening to an organ or structure. Some plants, fungi, and shelled gastropods have peristomes. In mo ...

. Embedded in the peristome are five

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines. In zoology ''Calcare ...

"teeth" collectively known as

Aristotle's lantern Sea urchins or urchins () are echinoderms in the class (biology), class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal zone to deep seas of . They typically have a globular body cove ...

. These are used for grinding the flower urchin's food. The

anus In mammals, invertebrates and most fish, the anus (: anuses or ani; from Latin, 'ring' or 'circle') is the external body orifice at the ''exit'' end of the digestive tract (bowel), i.e. the opposite end from the mouth. Its function is to facil ...

is situated on the upper (aboral) surface of the test, directly opposite the mouth. Like the mouth, it is surrounded by a ring of small plates known as the periproct. Surrounding the anal opening are five smaller holes (the genital pores) which are directly connected to the

gonad A gonad, sex gland, or reproductive gland is a Heterocrine gland, mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gon ...

s inside the body cavity. The most conspicuous feature of flower urchins are their

pedicellariae A pedicellaria (: pedicellariae) is a small wrench- or claw-shaped appendage with movable jaws, called valves, commonly found on echinoderms (phylum Echinodermata), particularly in sea stars (class Asteroidea) and sea urchins (class Echinoidea). ...

(stalked grasping appendages). Flower urchins possess four types of pedicellariae, distinguished by form and function, but only two are abundant. The first type are the ophicephalous pedicellariae. They resemble tube feet, except they end in three small claws (called valves) rather than suction cups. These are used to keep the body surface clear of algae, encrusting organisms, and unwanted debris. The second type are the globiferous pedicellariae which superficially resemble flowers (hence its common name). These are more specialized and are used for defense against

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

s and larger

ectoparasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

s. Globiferous pedicellariae also end in a three-valved claw-like grasping appendage, like they do in ophicephalous pedicellariae, but they are much larger. The valves are connected to each other by a distinctive circular membrane around in diameter. They are pinkish-white to yellowish-white in color with a central purple dot and a bright white rim. Each valve ends in a sharp fang-like tip which is capable of penetrating human skin. The base of the valves also house venom glands. Some authors further subdivide globiferous pedicellariae into two subtypes based on size - the trumpet pedicellariae and the giant pedicellariae. The other two types of pedicellariae - tridentate and triphyllous - are rare or restricted only to certain areas of the test. The relatively blunt spines are quite short and are usually hidden below the flower-like pedicellariae. They can vary from white, pink, yellow, light green, to purple in coloration with lighter-colored tips. Other members of the genus ''Toxopneustes'' are similar in appearance and can be mistaken for flower urchins. '' Toxopneustes roseus'' can be distinguished by the uniform coloration of their tests of pink, brown, or purple. It is also restricted to the East Pacific and thus aren't found together with flower urchins. '' Toxopneustes elegans'', which is only found around

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

, can be distinguished by the presence of a distinctive dark stripe just below the tips of their spines. '' Toxopneustes maculatus'' is a very rare species known only from specimens from

Réunion Réunion (; ; ; known as before 1848) is an island in the Indian Ocean that is an overseas departments and regions of France, overseas department and region of France. Part of the Mascarene Islands, it is located approximately east of the isl ...

Christmas Island Christmas Island, officially the Territory of Christmas Island, is an States and territories of Australia#External territories, Australian external territory in the Indian Ocean comprising the island of the same name. It is about south o ...

, and the

Palmyra Atoll Palmyra Atoll (), also referred to as Palmyra Island, is one of the Line Islands, Northern Line Islands (southeast of Kingman Reef and north of Kiribati). It is located almost due south of the Hawaiian Islands, roughly one-third of the way be ...

. It can be distinguished by the bright violet coloration on the bottom and in a band around the middle of their tests.

Distribution and habitat

Flower urchins are widespread and common in the

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

. They can be found north from

Okinawa most commonly refers to: * Okinawa Prefecture, Japan's southernmost prefecture * Okinawa Island, the largest island of Okinawa Prefecture * Okinawa Islands, an island group including Okinawa itself * Okinawa (city), the second largest city in th ...

, to

Tasmania Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

in the south; and west from the

Red Sea The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...

and the

East Africa East Africa, also known as Eastern Africa or the East of Africa, is a region at the eastern edge of the Africa, African continent, distinguished by its unique geographical, historical, and cultural landscape. Defined in varying scopes, the regi ...

n coast, to

Rarotonga Rarotonga is the largest and most populous of the Cook Islands. The island is volcanic, with an area of , and is home to almost 75% of the country's population, with 10,898 of a total population of 15,040. The Parliament of the Cook Islands, Coo ...

in the

Cook Islands The Cook Islands is an island country in Polynesia, part of Oceania in the South Pacific Ocean. It consists of 15 islands whose total land area is approximately . The Cook Islands' Exclusive Economic Zone (EEZ) covers of ocean. Avarua is its ...

in the east. In Mexican waters, the Flower Urchin can be found in every waters of the Pacific with the exception that they are absent from

Guerrero Negro Guerrero Negro (English: Black Warrior) is the largest town located in the municipality of Mulegé in the Mexican state of Baja California Sur (BCS). It had a population of 13,596 in the 2020 census. The town is served by Guerrero Negro Airport. ...

(Bahia Tortugas),

Baja California Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...

, northward along the central and northwest coasts of Baja. They are found among

s, coral rubble, rocks, sand, and

beds at depths of from the water's surface. They may sometimes partially bury themselves on the substrate.

Ecology and behavior

Diet

Flower urchins feed on

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic animal, aquatic invertebrate animals, nearly all living in sedentary Colony (biology), colonies. Typically about long, they have a spe ...

ns, and organic detritus.

Predators

Flower urchins have few predators. They are known to be toxic to fish. One of the few organisms capable of consuming flower urchins with no apparent adverse effects is the predatory corallimorph '' Paracorynactis hoplites''. However it is unknown if flower urchins are among its natural prey.

Associated species

The

commensal Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit f ...

alpheid

shrimp A shrimp (: shrimp (American English, US) or shrimps (British English, UK)) is a crustacean with an elongated body and a primarily Aquatic locomotion, swimming mode of locomotion – typically Decapods belonging to the Caridea or Dendrobranchi ...

'' Athanas areteformis'', can sometimes be found living among the spines of flower urchins (as well as burrowing urchins and collector urchins). The

intestines The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascular system. ...

of flower urchins can also serve as habitats for the commensal

flatworm Platyhelminthes (from the Greek language, Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") is a Phylum (biology), phylum of relatively simple bilaterian, Segmentation (biology), ...

'' Syndesmis longicanalis''. Flower urchins are also common hosts of the zebra crab, ''Zebrida adamsii''. These tiny crabs are

obligate symbiont Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term

autotomize. Although previously considered harmless commensals, authors have since reclassified them as

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

s. In addition to the visible external damage, a 1974 study also observed abnormal behavior and coloration among infected sea urchins. They also appear to be immune to the flower urchin's venom.

Reproduction

Flower urchins are

dioecious Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is ...

(having separate male and female individuals), but it is almost impossible to determine the sex of an individual by external characteristics alone. A possible method is by examining the external characteristics of the genital pores (

gonopore A gonopore, sometimes called a gonadopore, is a genital pore in many invertebrates. Hexapods, including insects, have a single common gonopore, except mayflies, which have a pair of gonopores. More specifically, in the unmodified female, it is ...

s). In males, they are generally short, cone-shaped, and extrude above the body surface; while in females they are usually sunken. However this is not reliable, as 15% of the cases can exhibit the opposite characteristics. All other external features, like shape and size of the tests or color of the spines are indistinguishable between the two sexes. Flower urchins have a

chromosome number Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, ...

of 2n = 42. Relatively little is known of the

spawning Spawn is the Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is ...

behavior of flower urchins. Like other sea urchins, fertilization happens externally. Males and females release free-swimming

gamete A gamete ( ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also referred to as s ...

s (eggs and sperm) directly into the water currents in mass spawning events. In

, a 1994 study identified the spawning season of flower urchins as occurring in winter, at the same time as the closely related and

sympatric In biology, two closely related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter each other. An initially interbreeding population that splits into two or more distinct spe ...

'' Toxopneustes elegans''. It also recorded possible

natural hybrid In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different varieties, subspecies, species or genera through sexual reproduction. Generally, it means that each cell has genetic material from two dif ...

s resulting from instances where the eggs of ''Toxopneustes pileolus'' are fertilized by the sperm of ''Toxopneustes elegans''. In

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...

, a 2010 study observed flower urchins spawning in May on the years 2007 and 2009. They occurred on highly similar conditions: in the afternoon

low tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables c ...

of the

spring tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables ...

immediately after a

new moon In astronomy, the new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the naked eye, except when it is silhouetted against the Sun during a solar eclipse. ...

. During the event, spawning individuals discard the debris that usually cover their bodies before releasing their gametes into the water. 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. It did note that the spawning patterns appeared to be non-random, with higher spawning rates on daytime on certain dates. However, the study was conducted within a span of only five months (from April to August 2010).

"Covering" behavior

Flower urchins are among the numerous species of sea urchins known as "collector urchins", so named because they frequently cover the upper surfaces of their bodies with debris from their surroundings. This behavior is usually referred to as "covering" or "heaping". Flower urchins are usually found almost completely covered in objects like dead

coral Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important Coral ...

fragments, shells,

seaweed Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of ''Rhodophyta'' (red), '' Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...

, and rocks. These are held fast to their bodies using their tube feet and pedicellariae. The function of this behavior is not well understood. Some authors believe that the debris serve as

ballast Ballast is dense material used as a weight to provide stability to a vehicle or structure. Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within ...

, preventing them from being swept away by wave surges when feeding; while others believe that they may function as some sort of defense against predation. A 2007 study has hypothesized that the behavior may serve as protection from

UV radiation Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of t ...

during daytime.

Venom

Bioactive components

At least two active

toxin A toxin is a naturally occurring poison produced by metabolic activities of living cells or organisms. They occur especially as proteins, often conjugated. The term was first used by organic chemist Ludwig Brieger (1849–1919), derived ...

s have been purified from the pedicellarial venom of flower urchins in two studies. The first was discovered in 1991 and named Contractin A. It was found to interfere with the transmission of signals at nerve endings as well as cause

hemagglutination Hemagglutination, or haemagglutination, is a specific form of agglutination that involves red blood cells (RBCs). It has two common uses in the laboratory: blood typing and the quantification of virus dilutions in a haemagglutination assay. Blo ...

(clumping of the

red blood cell Red blood cells (RBCs), referred to as erythrocytes (, with -''cyte'' translated as 'cell' in modern usage) in academia and medical publishing, also known as red cells, erythroid cells, and rarely haematids, are the most common type of blood cel ...

s). When administered to

guinea pig The guinea pig or domestic guinea pig (''Cavia porcellus''), also known as the cavy or domestic cavy ( ), is a species of rodent belonging to the genus ''Cavia'', family Caviidae. Animal fancy, Breeders tend to use the name "cavy" for the ani ...

s, it resulted in contractions in the

smooth muscles Smooth muscle is one of the three major types of vertebrate muscle tissue, the others being skeletal and cardiac muscle. It can also be found in invertebrates and is controlled by the autonomic nervous system. It is non- striated, so-called becau ...

. The second, discovered in 1994, is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

toxin named peditoxin. It is composed of the protein pedin and the active

prosthetic group A prosthetic group is the non-amino acid component that is part of the structure of the heteroproteins or conjugated proteins, being tightly linked to the apoprotein. Not to be confused with the cosubstrate that binds to the enzyme apoenzyme (e ...

pedoxin. At low doses to mice, pedoxin was found to result in markedly lower body temperatures,

muscle relaxation Muscle contraction is the activation of tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as ...

sedation Sedation is the reduction of irritability or agitation by administration of sedative drugs, generally to facilitate a medical procedure or diagnostic procedure. Examples of drugs which can be used for sedation include isoflurane, diethyl ether, ...

, and

anesthetic An anesthetic (American English) or anaesthetic (British English; see spelling differences) is a drug used to induce anesthesia ⁠— ⁠in other words, to result in a temporary loss of sensation or awareness. They may be divided into t ...

coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to Nociception, respond normally to Pain, painful stimuli, light, or sound, lacks a normal Circadian rhythm, sleep-wake cycle and does not initiate ...

. At higher doses it resulted in

convulsion A convulsion is a medical condition where the body muscles contract and relax rapidly and repeatedly, resulting in uncontrolled shaking. Because epileptic seizures typically include convulsions, the term ''convulsion'' is often used as a synony ...

s and death. Pedin itself is non-toxic, but it magnifies the effects of pedoxin. When combined into the holoprotein peditoxin, even low doses resulted in

anaphylaxis Anaphylaxis (Greek: 'up' + 'guarding') is a serious, potentially fatal allergic reaction and medical emergency that is rapid in onset and requires immediate medical attention regardless of the use of emergency medication on site. It typicall ...

-like

shock Shock may refer to: Common uses Healthcare * Acute stress reaction, also known as psychological or mental shock ** Shell shock, soldiers' reaction to battle trauma * Circulatory shock, a medical emergency ** Cardiogenic shock, resulting from ...

and death. UT841, a possible third toxin isolated in 2001, has been shown to affect brain metabolism in chicks. However, the authors are unclear on whether UT841 may actually be the same compound as Contractin A, since both have the same

molecular weight A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...

of 18,000 Da and an almost identical N-terminal sequence. In addition to these toxins,

lectin Lectins are carbohydrate-binding proteins that are highly specific for sugar Moiety (chemistry), groups that are part of other molecules, so cause agglutination (biology), agglutination of particular cells or precipitation of glycoconjugates an ...

s have also been isolated from flower urchin venom. Among them is SUL-I, SUL-II, SUL-IA, and SUL-III (SUL stands for "sea urchin lectin"). These lectins may be valuable as research tools for investigating the functions of cell processes. Podia de Toxopneustes pileolus

Envenomation mechanism

Unlike most other venomous sea urchins, flower urchins and related toxopneustids do not deliver their venom through spines. Instead, the venom is administered through the flower-like globiferous pedicellariae. If undisturbed, the tips of the globiferous pedicellariae are usually expanded into round cup-like shapes. They possess tiny sensors on their inside surfaces which can detect threats by touch and chemical stimuli. When agitated or brushed against by a potential threat, the pedicellariae will immediately snap shut and inject venom. 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. The potency of the pedicellarial venom is believed to be directly related to the size of the pedicellariae. Thus individuals with larger globiferous pedicellariae are considered to be more dangerous than individuals with more numerous but smaller globiferous pedicellariae.

Effects on humans

In 1930, the

marine biologist Marine biology is the scientific study of the biology of marine life, organisms that inhabit the sea. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology clas ...

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: There have been reports of fatalities resulting from flower urchin envenomation. One such report was the purported drowning of a pearl diver after being rendered unconscious from accidental contact with a flower urchin. But it remains difficult to confirm if these incidents actually occurred since no documentation or details of the deaths have been uncovered so far. Nevertheless, flower urchins are still considered highly dangerous. 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. The flower urchin was named the "most dangerous sea urchin" in the 2014 ''

Guinness World Records ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a British reference book published annually, list ...

''.

Edibility

Despite being venomous, flower urchins are sometimes harvested in

East Asia East Asia is a geocultural region of Asia. It includes China, Japan, Mongolia, North Korea, South Korea, and Taiwan, plus two special administrative regions of China, Hong Kong and Macau. The economies of Economy of China, China, Economy of Ja ...

Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...

, and the

Pacific Island The Pacific islands are a group of islands in the Pacific Ocean. They are further categorized into three major island groups: Melanesia, Micronesia, and Polynesia. Depending on the context, the term ''Pacific Islands'' may refer to one of several ...

s for their edible gonads. In the

Sulu Archipelago The Sulu Archipelago ( Tausug: Kapū'-pūan sin Sūg Sulat Sūg: , ) is a chain of islands in the Pacific Ocean, in the southwestern Philippines. The archipelago forms the northern limit of the Celebes Sea and southern limit of the Sulu Se ...

of the

Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...

and eastern

Sabah Sabah () is a States and federal territories of Malaysia, state of Malaysia located in northern Borneo, in the region of East Malaysia. Sabah has land borders with the Malaysian state of Sarawak to the southwest and Indonesia's North Kalima ...

Malaysia Malaysia is a country in Southeast Asia. Featuring the Tanjung Piai, southernmost point of continental Eurasia, it is a federation, federal constitutional monarchy consisting of States and federal territories of Malaysia, 13 states and thre ...

, flower urchins are among the species of edible sea urchins used by the

Sama-Bajau The Sama-Bajau include several Austronesian ethnic groups of Maritime Southeast Asia. The name collectively refers to related people who usually call themselves the Sama or Samah (formally A'a Sama, "Sama people"); or are known by the exonym ...

and Tausug people to make a traditional delicacy known as '' oko-oko'' or ''ketupat tehe tehe''. This is prepared by degutting the test and then filling it with

glutinous rice Domestication syndrome refers to two sets of phenotypic traits that are common to either domesticated plants or domesticated animals. Domesticated animals tend to be smaller and less aggressive than their wild counterparts; they may also hav ...

and

coconut milk Coconut milk is a plant milk extracted from the grated pulp of mature coconuts. The opacity and rich taste of the milky-white liquid are due to its high oil content, most of which is saturated fat. Coconut milk is a traditional food ingred ...

before boiling.

Other uses

In Okinawa, fishermen observed numerous individuals of the predatory

crown-of-thorns starfish The crown-of-thorns starfish (frequently abbreviated to COTS), ''Acanthaster planci'', is a large starfish that preys upon hard, or stony, coral polyps (Scleractinia). The crown-of-thorns starfish receives its name from venomous thornlike spines ...

(''Acanthaster planci'') gathering around the remains of the internal organs of flower urchins. A follow-up study by Japanese researchers in 2001 confirmed that the

viscera In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to a ...

of flower urchins could indeed attract crown-of-thorns starfish in both aquarium and open sea experiments. The attractant compounds were isolated and identified as

arachidonic acid Arachidonic acid (AA, sometimes ARA) is a polyunsaturated omega−6 fatty acid 20:4(ω−6), or 20:4(5,8,11,14). It is a precursor in the formation of leukotrienes, prostaglandins, and thromboxanes. Together with omega−3 fatty acids an ...

and

α-linolenic acid α-Linolenic acid, also known as ''alpha''-linolenic acid (ALA) (from Greek ''alpha'' denoting "first" and ''linon'' meaning flax), is an ''n''−3, or omega-3, essential fatty acid. ALA is found in many seeds and oils, including flaxseed, ...

. 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.

References

External links

*
Video of a live flower urchin in its natural habitat
(YouTube)
Video of a live captive flower urchin
(YouTube)
Video of a flower urchin with a zebra crab
(YouTube) * {{Taxonbar, from=Q2488394 Toxopneustidae Echinoderms of the Indian Ocean Echinoderms of the Pacific Ocean Echinoderms described in 1816 Taxa named by Jean-Baptiste Lamarck