Overview

Brief Summary

Diadema setosum - overview

Diadema setosum is one of the most common seashore sea urchins in the tropical indo-pacific, especially in coral ecosystems : hence, they are supposed to have an important ecological role, especially in algae grazing. It can be found from the red sea to Hawaii and Pacific archipelagos, from the shore to 20-30 meters deep (sometimes deeper).

Like most Diadema sea urchins, it is a big, dark regular echinoid, with a rather small test and very long spines, which can reach up to 30cm each. These are usually black but some or all of them can be grey or white, and they are banded in young individuals.

This sea urchins looks a lot like its relative Diadema savignyi, and they can be difficult to tell apart. D. setosum has longer spines compared to the test, and a distinct pattern of iridophores, usually with 5 white dots (whereas D. savignyi has more visible iridophores, blue or greyish, usually forming a star - but on some individuals iridophores can be absent in both species).

The most distinctive characteristic of D. setosum is to have an orange ring around its prominent anal papilla, but it may be less visible in some specimens.

Some of the shorter spines are slightly venomous (like in most diadematids), but not really dangerous.

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WhyReef - Lifestyle

Like the sea star, the long-spine sea urchin is an echinoderm, which means “spiny skin”.

It uses hundreds of flexible, straw-like tube feet to move around, eat and breathe.

Its hollow, hooked spines protect it by breaking off and stabbing anything that tries to touch it. These spines are very painful and difficult to remove.

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Comprehensive Description

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The long-spine sea urchin is all turned around: its behind is on its head and its mouth is down by its feet! It uses its tube feet to get a good grip on its food, and then moves its powerful mouth over the food to eat it. Its mouth is made up of fifty pieces of skeleton, sixty muscles, and five tooth plates! In fact, its mouth is so complicated that scientists even gave it its own special name—Aristotle’s Lantern.
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Physical Description

Diagnostic Description

Description

Colour in life: black, red ring around anus and white spot over each genital pore (Humphreys, 1981). One specimen with eight parastic eulimid gastropods Echineulima mittrei mittrei (Petit, 1851). Also distributed in Saudi Arabia (Clark, 1954); Australia (Kalk (1958) and Rowe & Gates (1995)); SE Arabia, Persian Gulf, Ceylon, Bay of Bengal, East Indies, north Australia, Philippine, China, south Japan and South Pacific Is. (Clark & Rowe, 1971); India (Sastry, 1996). General distribution: tropical Indo-Pacific in Kalk (1958); tropical, Indo-west-central Pacific Ocean, depth range 0-70 m. (Rowe & Gates, 1995). Ecology: benthic, inshore, continental shelf (Rowe & Gates, 1995).
  • Clark, A.M. and F.W.E. Rowe. (1971). Monograph of Shallow-water Indo-West Pacific Echinoderms. Trustees of the British Museum (Natural History): London. x + 238 p. + 30 pls.
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Ecology

Habitat

Depth range based on 8 specimens in 1 taxon.
Water temperature and chemistry ranges based on 2 samples.

Environmental ranges
  Depth range (m): 2 - 428
  Temperature range (°C): 25.015 - 27.956
  Nitrate (umol/L): 0.194 - 0.546
  Salinity (PPS): 34.598 - 36.334
  Oxygen (ml/l): 4.532 - 4.780
  Phosphate (umol/l): 0.090 - 0.408
  Silicate (umol/l): 2.543 - 5.805

Graphical representation

Depth range (m): 2 - 428

Temperature range (°C): 25.015 - 27.956

Nitrate (umol/L): 0.194 - 0.546

Salinity (PPS): 34.598 - 36.334

Oxygen (ml/l): 4.532 - 4.780

Phosphate (umol/l): 0.090 - 0.408

Silicate (umol/l): 2.543 - 5.805
 
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Associations

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The long-spine sea urchin dines on plants. It will eat turf algae, seagrass and calcareous seaweeds (like Halimeda tuna), but it also munches on coral. Because it eats both plants and animals, it is an omnivore.
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Diadema setosum

The following is a representative barcode sequence, the centroid of all available sequences for this species.


No available public DNA sequences.

Download FASTA File
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Statistics of barcoding coverage: Diadema setosum

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 2
Specimens with Barcodes: 4
Species With Barcodes: 1
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Conservation

Threats

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Too many long-spine sea urchins are bad for coral reefs, but too few of them can be a bad thing, too! They love to eat algae, and algae and corals compete for space in the reef. By eating the algae they make more room for the coral to grow. But if they eat too much algae, then there is no food left for the other animals that eat algae.
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Wikipedia

Diadema setosum

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 venomous. 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 being capable of causing painful stings when stepped upon, the urchin is only slightly venomous and does not pose a serious threat to humans.

Description[edit]

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, often 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.

Periproctal cone of Diadema setosum

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.[2][3] Sexually mature Diadema setosum specimens average from 35 to 80 grams in weight.[4] Adults average a size of no more than 70 millemeters in test diameter and around 40 millemeters high.[5]

Distribution and habitat[edit]

Diadema setosum, black spines color-morph

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 Australian coast. Latitudinally, the species can be found as far north as Japan and its range extends as far south as the southern tip of the African east coast.[2]

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.[2] Several hypotheses have been proposed for the finding of these individuals. Larvae 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 ballasts. A final possibility proposed was that the individual specimens were intentionally released by aquarists.[2]

Diadema setosum is commonly associated with coral reefs, 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.[5]

Biology[edit]

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.[6] 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.[7] For a population in the Persian Gulf, spawning occurs during the months of April to May.[4] 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.[8]

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.[9] 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.[5]

Like other venomous sea urchins, the venom of Diadema setosum is only mild and not at all fatal to humans. 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.[10]

Gallery[edit]

References[edit]

  1. ^ a b Kroh, Andreas (2013). "Diadema setosum (Leske, 1778)". In A. Kroh & R. Mooi. World Echinoidea Database. World Register of Marine Species. Retrieved 2013-11-22. 
  2. ^ a b c d Yokes, Baki; Bella S. Galil (2006). "The first record of the needle-spined urchin Diadema setosum (Leske, 1778) (Echinodermata: Echinoidea: Diadematidae) from the Mediterranean Sea". Aquatic Invasions (European Research Network on Aquatic Invasive Species) 1 (3): 188–190. doi:10.3391/ai.2006.1.3.15. 
  3. ^ Clark, HL (1925). A catalogue of the recent sea-urchins (Echinoidea) in the collection of the British Museum (Natural History). London: British Museum. p. 250. 
  4. ^ a b Alsaffar, Adel H.; Khalid P. Lone (2000). "Reproductive cycles of Diadema setosum and Echinometra mathaei (Echinoidea: Echinodermata) from Kuwait (Northern Arabian Gulf)". Bulletin of Marine Science 67 (2): 845–856. 
  5. ^ a b c Coppard, Simon Edward; Andrew C. Campbell (2006). "Taxonomic significance of test morphology in the echinoid genera Diadema Gray, 1825 and Echinothrix Peters, 1853 (Echinodermata)". Zoosystema 28 (1): 93–112. Retrieved 2009-01-12. 
  6. ^ Pearse, John S. (1974). "Reproductive patterns of tropical reef animals: three species of sea urchins". Proceedings of the 2nd International Coral Reef Symposium (Brisbane, Australia: ICRS) 1: 235–240. Retrieved 2009-01-12. 
  7. ^ Tuason, A. Y.; Ed D. Gomez (1979). "The reproductive biology of Tripneustes gratilla Linnaeus (Echinodermata: Echinoidea), with some notes on Diadema setosum". Proceedings of the International Symposium on Marine Biogeographic Evolution (Auckland, New Zealand) 2: 707–716. 
  8. ^ Lessios, H. A. (1981). "Reproductive periodicity of the echinoids Diadema and Echinometra on the two coasts of Panama". Journal of Experimental Marine Biology and Ecology 50 (1): 47–61. doi:10.1016/0022-0981(81)90062-9. 
  9. ^ Lessios, H. A.; B. D. Kessing and John S. Pearse (2001). "Population structure and speciation in tropical seas. Global phylogeography of the sea urchin Diadema". Evolution 55 (5): 955–975. doi:10.1554/0014-3820(2001)055[0955:PSASIT]2.0.CO;2. PMID 11430656. 
  10. ^ Williamson, JA; PJ Fenner, JW Burnett and JF Rifkin (1996). Venomous and poisonous marine animals: a medical and biological handbook. Sydney, Australia: University of New South Wales Press. p. 504. ISBN 0-86840-279-6. 

Bibliography[edit]

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