Diadema setosum
Encyclopedia
Diadema setosum is a species of long-spined sea urchin
belonging to the family Diadematidae
. It is a typical sea urchin, with extremely long, hollow spines that are mildly venom
ous. D. setosum differs from other Diadema
with five, characteristic white dots that can be found on its body. The species can be found throughout the Indo-Pacific
region, from Australia
and Africa
to Japan
and the Red Sea
. Despite capable of painful stings when stepped upon, the urchin is only slightly venomous and does not pose a serious threat to humans.
As a member of the class Echinoidea, the anatomy of Diadema setosum is that of a typical sea urchin
. All of the animal's internal organs are enclosed within the spherical, black test
that is essentially the body of the organism. However, the body is not perfectly spherical – Diadema tests are slightly dorso-ventrally compressed. Protruding outwards from the central body are the long spines iconic of a sea urchin's appearance. Like the other members of the family Diadematidae
, the spines of D. setosum are extremely long and narrow in proportion to its body. The spines, oftentimes black but sometimes brown-banded, are hollow and contain a mild venom
. D. setosum can be distinguished from other species in the genus
Diadema by the presence of five white spots on the animal's test, strategically located between the urchin's ambulacral grooves.
In addition, a clear distinguishing characteristic of the species is the presence of a bright, orange ring around the urchin's periproctal cone, a structure commonly referred to as the urchin's "anus
". A few other minor characteristics in D. setosum include bluish spots on the organism's genital plates and similar blue spots (iridophores) arranged in linear fashion along its test. An apical ring is absent in the species, along with calcareous
platelets on its apical cone. Sexually mature Diadema setosum specimens average from 35 to 80 grams in weight. Adults average a size of no more than 70 millemeters in test diameter and around 40 millemeters high.
Diadema setosum is a widely-distributed species of sea urchin. Its range
stretches throughout the Indo-Pacific
basin, longitudinally
from the Red Sea
and then eastward to the Australia
n coast. Latitudinally
, the species can be found as far north as Japan
and its range extends as south as the southern tip of the Africa
n east coast.
The species has been introduced into other localities not within its natural range. In 2006, two living specimens of Diadema setosum were found in waters off the Kaş
peninsula in Turkey
. The discovery and subsequent collection of these individuals makes D. setosum the first invasive
Erythrean sea urchin in the Mediterranean. Several hypotheses have been proposed for the finding of these individuals. Larva
e of the species may have traveled through the Suez Canal
into the Mediterranean from the Gulf of Suez
, where the species has a thriving natural population. Another proposed vector is that of foreign ships bringing in individuals via their ballast
s. A final possibility proposed was that the individual specimens were intentionally released by aquarists.
Diadema setosum is commonly associated with coral reef
s, but is also found on sand flats and in seagrass beds. Along with the other members of the family, D. setosum is a prolific grazer. They are known to feed on a variety of algal
species common on tropical coral reefs. The ecological importance of the taxon as a whole has been stressed because of its herbivorous habits.
The species has been known to spawn both seasonally and year-round depending on the location of the spawning population. It has been suggested that Diadema setosum populations are temperature-dependent in their spawning seasonalities. Temperatures higher than 25oC have been cited as a possible spawning cue. Equatorial populations are those recorded to spawn at no particular times throughout the entire year. This is true for the Philippine populations of D. setosum. For a population in the Persian Gulf, spawning occurs during the months of April to May. Other cues, such as the phases of the moon have been observed to affect the spawning of D. setosum populations. The species has been found to trigger spawning events in concordance with the appearance of a full moon
.
Evolutionarily, Diadema setosum is considered one of the oldest of the known extant species in the genus Diadema. Genetic analysis of the Diadema have placed D. setosum at a basal branch on a cladogram, having it as the sister group to all the other remaining members of the genus. Morphological analysis confirms this conclusion, adding weight to the concept of D. setosum being the most basal of the Diadema and possibly the oldest extant species in the genus.
Like other venomous sea urchins, the venom
of Diadema setosum is only mild and not at all fatal to human
s. The toxin mostly causes swelling and pain, and gradually diffuses over several hours. More danger is presented by the delivery system – the urchin's spines which are extremely brittle and needle-like. They easily break off within flesh and are quite a challenge to extract.
Sea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...
belonging to the family Diadematidae
Diadematidae
Diadematidae is a family of sea urchins.* Astropyga **Astropyga radiata , extant**Astropyga pulvinata , extant**Astropyga magnifica , extant*Centrostephanus...
. It is a typical sea urchin, with extremely long, hollow spines that are mildly venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
ous. D. setosum differs from other Diadema
Diadema (genus)
Diadema is a genus of sea urchins of the Family Diadematidae and is one of the most abundant, widespread, and ecologically important shallow water genera of tropical sea urchins. It is found in all tropical oceans, although is ubiquitous in the Indo-Pacific region, where it inhabits depths down to...
with five, characteristic white dots that can be found on its body. The species can be found throughout the Indo-Pacific
Indo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
region, from Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
to Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
. Despite capable of painful stings when stepped upon, the urchin is only slightly venomous and does not pose a serious threat to humans.
As a member of the class Echinoidea, the anatomy of Diadema setosum is that of a typical sea urchin
Sea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...
. All of the animal's internal organs are enclosed within the spherical, black test
Test (biology)
A test is a term used to refer to the shell of sea urchins, and also the shell of certain microorganisms, such as testate foraminifera and testate amoebae....
that is essentially the body of the organism. However, the body is not perfectly spherical – Diadema tests are slightly dorso-ventrally compressed. Protruding outwards from the central body are the long spines iconic of a sea urchin's appearance. Like the other members of the family Diadematidae
Diadematidae
Diadematidae is a family of sea urchins.* Astropyga **Astropyga radiata , extant**Astropyga pulvinata , extant**Astropyga magnifica , extant*Centrostephanus...
, the spines of D. setosum are extremely long and narrow in proportion to its body. The spines, oftentimes black but sometimes brown-banded, are hollow and contain a mild venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
. D. setosum can be distinguished from other species in the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Diadema by the presence of five white spots on the animal's test, strategically located between the urchin's ambulacral grooves.
In addition, a clear distinguishing characteristic of the species is the presence of a bright, orange ring around the urchin's periproctal cone, a structure commonly referred to as the urchin's "anus
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
". A few other minor characteristics in D. setosum include bluish spots on the organism's genital plates and similar blue spots (iridophores) arranged in linear fashion along its test. An apical ring is absent in the species, along with calcareous
Calcareous
Calcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.-In zoology:...
platelets on its apical cone. Sexually mature Diadema setosum specimens average from 35 to 80 grams in weight. Adults average a size of no more than 70 millemeters in test diameter and around 40 millemeters high.
Diadema setosum is a widely-distributed species of sea urchin. Its range
Range (biology)
In biology, the range or distribution of a species is the geographical area within which that species can be found. Within that range, dispersion is variation in local density.The term is often qualified:...
stretches throughout the Indo-Pacific
Indo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
basin, longitudinally
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....
from the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
and then eastward to the Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
n coast. Latitudinally
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
, the species can be found as far north as Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and its range extends as south as the southern tip of the Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
n east coast.
The species has been introduced into other localities not within its natural range. In 2006, two living specimens of Diadema setosum were found in waters off the Kaş
Kas
Kas is the brand name of soft drink produced by PepsiCo. It comes in grapefruit, orange , lemon , bitter , and apple flavors. Kasfruit juices are also offered in multiple flavors...
peninsula in Turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...
. The discovery and subsequent collection of these individuals makes D. setosum the first invasive
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
Erythrean sea urchin in the Mediterranean. Several hypotheses have been proposed for the finding of these individuals. Larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e of the species may have traveled through the Suez Canal
Suez Canal
The Suez Canal , also known by the nickname "The Highway to India", is an artificial sea-level waterway in Egypt, connecting the Mediterranean Sea and the Red Sea. Opened in November 1869 after 10 years of construction work, it allows water transportation between Europe and Asia without navigation...
into the Mediterranean from the Gulf of Suez
Gulf of Suez
The northern end of the Red Sea is bifurcated by the Sinai Peninsula, creating the Gulf of Suez in the west and the Gulf of Aqaba to the east. The Gulf of Suez is formed within a relatively young, but now inactive rift basin, the Gulf of Suez Rift, dating back about 28 million years...
, where the species has a thriving natural population. Another proposed vector is that of foreign ships bringing in individuals via their ballast
Ballast tank
A ballast tank is a compartment within a boat, ship or other floating structure that holds water.-History:The basic concept behind the ballast tank can be seen in many forms of aquatic life, such as the blowfish or argonaut octopus, and the concept has been invented and reinvented many times by...
s. A final possibility proposed was that the individual specimens were intentionally released by aquarists.
Diadema setosum is commonly associated with coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
s, but is also found on sand flats and in seagrass beds. Along with the other members of the family, D. setosum is a prolific grazer. They are known to feed on a variety of algal
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
species common on tropical coral reefs. The ecological importance of the taxon as a whole has been stressed because of its herbivorous habits.
The species has been known to spawn both seasonally and year-round depending on the location of the spawning population. It has been suggested that Diadema setosum populations are temperature-dependent in their spawning seasonalities. Temperatures higher than 25oC have been cited as a possible spawning cue. Equatorial populations are those recorded to spawn at no particular times throughout the entire year. This is true for the Philippine populations of D. setosum. For a population in the Persian Gulf, spawning occurs during the months of April to May. Other cues, such as the phases of the moon have been observed to affect the spawning of D. setosum populations. The species has been found to trigger spawning events in concordance with the appearance of a full moon
Full moon
Full moon lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. More precisely, a full moon occurs when the geocentric apparent longitudes of the Sun and Moon differ by 180 degrees; the Moon is then in opposition with the Sun.Lunar eclipses can only occur at...
.
Evolutionarily, Diadema setosum is considered one of the oldest of the known extant species in the genus Diadema. Genetic analysis of the Diadema have placed D. setosum at a basal branch on a cladogram, having it as the sister group to all the other remaining members of the genus. Morphological analysis confirms this conclusion, adding weight to the concept of D. setosum being the most basal of the Diadema and possibly the oldest extant species in the genus.
Like other venomous sea urchins, the venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
of Diadema setosum is only mild and not at all fatal to human
Human
Humans are the only living species in the Homo genus...
s. The toxin mostly causes swelling and pain, and gradually diffuses over several hours. More danger is presented by the delivery system – the urchin's spines which are extremely brittle and needle-like. They easily break off within flesh and are quite a challenge to extract.