Overview

Brief Summary

Diadema - overview

Diadema is a genus of tropical sea urchins.

These echinoids are quite common in shallow waters throughout all the tropics, as well in the Atlantic (D. antillarum, D. ascensionis) as in the Indian (D. setosum, D. savignyi, D. paucispinum) and Pacific oceans (D. setosum, D. savignyi, D. paucispinum, D. palmeri, D. mexicanum). They usually live at snorkelling depths in coral ecosystems, but can be found as deep as 70m. They are mainly grazers, but can eat a wide variety of foods.

These species all share a distinctive shape, with a rather small test (5-10cm) but very long and slender spines (up to 30cm in D. setosum). However, some related species such as Centrostephanus longispinus have a similar shape, and in a lesser extent some species of Echinostrephus or cidaroids (with stouter spines).

Most species are dark colored, eventually with a slight tinge, but some specimens can be greyish or even white ; D. palmeri however is distinctly bright red.

Most species have a particular pattern of electric blue on the aboral part of the test, called "iridophores" : it is especillally obvious on D. savignyi. Like all diadematids, they wear a characteristic "anal papilla" at the top of the test. Still a characteristic of the family, some of their spines are venomous and painful, but not really dangerous.

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Ecology

Habitat

Depth range based on 724 specimens in 11 taxa.
Water temperature and chemistry ranges based on 681 samples.

Environmental ranges
  Depth range (m): 0.2 - 1814
  Temperature range (°C): 4.280 - 28.546
  Nitrate (umol/L): 0.008 - 39.707
  Salinity (PPS): 32.593 - 36.548
  Oxygen (ml/l): 0.171 - 4.984
  Phosphate (umol/l): 0.055 - 3.255
  Silicate (umol/l): 0.869 - 72.834

Graphical representation

Depth range (m): 0.2 - 1814

Temperature range (°C): 4.280 - 28.546

Nitrate (umol/L): 0.008 - 39.707

Salinity (PPS): 32.593 - 36.548

Oxygen (ml/l): 0.171 - 4.984

Phosphate (umol/l): 0.055 - 3.255

Silicate (umol/l): 0.869 - 72.834
 
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
Specimen Records: 62
Specimens with Sequences: 39
Specimens with Barcodes: 39
Species: 7
Species With Barcodes: 7
Public Records: 14
Public Species: 5
Public BINs: 4
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Barcode data

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Wikipedia

Diadema (genus)

Diadema is a genus of sea urchins of the Family Diadematidae.

Characteristics[edit]

It 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 70 m. However each species inhabits roughly separate areas of ocean.

Long-spined urchins Diadema, London Zoo.

Speciation within the genus can be difficult to confirm, partly due to hybridisation, which is at least known to occur between Diadema savignyi and Diadema setosum.

The species vary in types of sea bed they inhabit, with Diadema savignyi inhabiting sandy beds and back reef where damaged; while Diadema setosum can also commonly be found among seagrass.

Fossil record[edit]

The fossil record of Diadema is extremely poor, consisting only of spines that possibly belong to the genus, some of which go back to the Miocene, 5 to 24 million years ago.

Species list[edit]

According to World Register of Marine Species :


References[edit]

Bibliography[edit]

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