Tag Archives: Long-spined sea urchin Grand Bahama

URCHIN RESEARCHIN’: SEA HEDGEHOGS OF THE REEF

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Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

 

URCHIN RESEARCHIN’: SEA HEDGEHOGS OF THE REEF

The long-spined sea urchin Diadema antillarum featured in this post is one of those creatures that handily offers its USP in its name, so you know what you are dealing with. Something prickly, for a start. These are creatures of the reef, and many places in the Caribbean and in the western Atlantic generally sustain healthy populations.

Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

These animals are essentially herbivores, and their value to vulnerable coral reefs cannot be overstated. Where there is a healthy population of these urchins, the reef will be kept clean from smothering algae by their methodical grazing. They also eat sea grass.

Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

HOW DO THE SPINES OF DIFFERENT KINDS OF URCHIN COMPARE?

Small sea urchin species have spines a few cms long at most. The long-spine variety can exceed 10 cms, and the largest may have spines up to 30 cms (= 1 foot) long. The length, as shown here, means that when the creatures are safely lodged in crevices near their algae supply, their spines remain very visible.
 
Long-spined sea urchin Diadema antillarum (Melinda Riger / G B Scuba)
 
Anatomy of a long-spined sea urchin. You may possess a few of these organs yourself…

Long-spined sea urchin Diadema antillarum anatomy diagram (wiki)

Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

CAN YOU GIVE US A TEST, PLEASE?

As with SAND DOLLARS and similar creatures, the skeleton of a sea urchin is known as a ‘test’. Urchin tests are remarkably beautiful, especially seen in sunlight. Here are 2 examples I photographed a while ago. You’ll immediately notice the delicate colours and the amazing complexity of the pattern and symmetry. The top one is (or is most like) a long-spined urchin test.
 
 
Long-spined sea urchin Test / Skeleton Diadema antillarum (Keith Salvesen / Rolling Harbour) Long-spined sea urchin Test / Skeleton Diadema antillarum (Keith Salvesen / Rolling Harbour)

A BIT ABOUT SYMMETRY

Sea urchins are born with bilateral symmetry – in effect, you could fold one in half. If you wear gloves. As they grow to adulthood, they retain symmetry but develop so-called ‘fivefold symmetry’, rather as if an orange contained 5 equal-sized segments. The graphic above gives a good idea of how the interior is arranged inside the segments.

Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

A FEW FACTS TO HAND DOWN TO YOUR CHILDREN

  • Urchin fossil records date the species back to the Ordivician period c 40m years ago
  • In the ’90s the population was decimated and still has not recovered fully
  • Urchins feel stress: a bad sign that the spines here are white rather than black
  • Urchins are not only warm water creatures: some kinds live in polar regions
  • Urchins are of particular use in scientific research, including genome studies
  • Some urchins end up in aquariums / aquaria, where I doubt the algae is so tasty
  • Kindest not to prod or tread on them
  • Their nearest relative (surprisingly) is said to be the Sea Cucumber 

Sea Cucumber (Melinda Riger / G B Scuba)

ARE THEY EDIBLE?

They are eaten in some parts of the world, but only where the gonads and roe are considered a delicacy. Personally, I could leave them or leave them.

CREDITS: Melinda Rogers / Dive Abaco (1, 2, 3, 6, 9) taken Abaco; Melinda Riger / G B Scuba (4, 10, 11) taken Grand Bahama; Keith Salvesen / Rolling Harbour (7, 8) taken Abaco; Wiki graphic (5) CC . RESEARCH Fred Riger for detailed  information; otherwise magpie pickings… This is an archive post

Long-spined sea urchin Diadema antillarum (Melinda Riger / G B Scuba)

SEA URCHINS: PICTURE PERFECT ABACO (11)

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SEA URCHINS: PICTURE PERFECT ABACO (11)

Sea Urchin, Abaco, Bahamas (Melinda Rogers / Dive Abaco)

As every swimmer knows, or eventually finds out the hard way, it’s not only Blue Suede Shoes that should not be stepped on. But however painful the consequences of a misstep, it’s hard not to find some beauty in an urchin living in a thriving reef environment. The wonderful anatomical diagram by Alex Ries shows everything you could conceivably want to know about one of nature’s most proficient foot-stabbers (if only all such diagrams were presented so simply and clearly).

Sea urchin anatomy (Alex Ries)

The internal organs depicted resemble a bad trip in the bowels of a vacuum cleaner; or (narrow your eyes) an experimental painting from one of the less successful schools of early c20 modern art, soon to be swept aside by Cubism. Note that the mouth is located where you might expect to find the opposite end, and vice versa.

I photographed the urchin test (skeleton) below at Delphi. It was large and almost entirely undamaged (very rare in my experience). The bright faintly greenish white is set off by the palest of pinks. Whatever your view of how creatures came to exist, imagine the creation or evolution of calcium carbonate into a small symmetrical structure as beautiful, detailed and complex as this. If you are short of a lockdown recreation, maybe try to draw it.

Sea Urchin Test / Skeleton, Abaco Bahamas (Keith Salvesen / Rolling Harbour Abaco)

Photo credits: #1 Melinda Rogers / Dive Abaco; #2 Anatomy Diagram, Alex Reis (5 stars for making it available free on Wikimedia); #3 Keith Salvesen / Rolling Harbour Abaco

URCHIN RESEARCHIN’: SEA HEDGEHOGS OF THE REEF

by

Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

URCHIN RESEARCHIN’: SEA HEDGEHOGS OF THE REEF

The long-spined sea urchin Diadema antillarum featured in this post is one of those creatures that handily offers its USP in its name, so you know what you are dealing with. Something prickly, for a start. These are creatures of the reef, and many places in the Caribbean and in the western Atlantic generally sustain healthy populations.

Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

These animals are essentially herbivores, and their value to vulnerable coral reefs cannot be overstated. Where there is a healthy population of these urchins, the reef will be kept clean from smothering algae by their methodical grazing. They also eat sea grass.

Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

HOW DO THE SPINES OF DIFFERENT KINDS OF URCHIN COMPARE?

Small sea urchins species have spines a few cms long at most. The long-spine variety exceed 10 cms, and the largest may have spines up to 30 cms (= 1 foot) long. The length, as shown here, means that when the creatures are safely lodged in crevices near their algae supply, their spines remain very visible.
Long-spined sea urchin Diadema antillarum (Melinda Riger / G B Scuba)
Anatomy of a long-spined sea urchin. You may possess a few of these organs yourself…

Long-spined sea urchin Diadema antillarum anatomy diagram (wiki)

Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

CAN YOU GIVE US A TEST, PLEASE?

As with SAND DOLLARS and similar creatures, the skeleton of a sea urchin is known as a ‘test’. Urchin tests are remarkably beautiful, especially seen in sunlight. Here are 2 examples I photographed a while ago. You’ll immediately notice the delicate colours and the amazing complexity of the pattern and symmetry. The top one is (or is most like) a long-spined urchin test.
Long-spined sea urchin Test / Skeleton Diadema antillarum (Keith Salvesen / Rolling Harbour) Long-spined sea urchin Test / Skeleton Diadema antillarum (Keith Salvesen / Rolling Harbour)

A BIT ABOUT SYMMETRY

Sea urchins are born with bilateral symmetry – in effect, you could fold one in half. As they grow to adulthood, they retain symmetry but develop so-called ‘fivefold symmetry’, rather as if an orange contained 5 equal-sized segments. The graphic above gives a good idea of how the interior is arranged inside the segments.

Long-spined sea urchin Diadema antillarum (Melinda Rodgers / Dive Abaco)

A FEW FACTS TO HAND DOWN TO YOUR CHILDREN

  • Urchin fossil records date the species back to the Ordivician period, c 40m years ago
  • In the ’90s the population was decimated and still has not recovered fully
  • Urchins feel stress: a bad sign that the spines here are white rather than black
  • Urchins are not only warm water creatures: some kinds live in polar regions
  • Urchins are of particular use in scientific research, including genome studies
  • Some urchins end up in aquariums / aquaria, where I doubt the algae is so tasty
  • Kindest not to prod or tread on them
  • Their nearest relative (surprisingly) is said to be the Sea Cucumber 

Sea Cucumber (Melinda Riger / G B Scuba)

ARE THEY EDIBLE?

Apparently they are eaten in some parts of the world; their gonads and roe are considered a delicacy. As far as I know, they are not generally on the menu in the Bahamas. Correction invited. Personally, I could leave them or leave them.

CREDITS: Melinda Rodgers / Dive Abaco (1, 2, 3, 6, 9) taken Abaco; Melinda Riger / G B Scuba (4, 10, 11) taken Grand Bahama; Keith Salvesen / Rolling Harbour (7, 8) taken Abaco; Wiki graphic (5) taken from internet. RESEARCH Fred Riger for detailed  information; otherwise the usual magpie pickings…

Long-spined sea urchin Diadema antillarum (Melinda Riger / G B Scuba)