Edible Sea-Urchin
Echinus esculentus
Sadly, the beautifully colored edible sea-urchin has become a familiar sight in beach souvenir shops. The animal is collected extensively because its test (shell-like internal skeleton) makes popular decorative objects and souvenirs. Sea-urchins are spiny-skinned invertebrates that are in the same phylum Echinodermata-as sea lilies, starfish, brittle stars, and sea cucumbers. Like other echinoderms, they have no head and no true brain, and their bodies have a skeleton of chalky plates. There are about 800 species of sea-urchin. Sea-urchins are important grazers in marine communities. By eating young and developing algae (plants without true stems, roots, and leaves), they play a major role in controlling vegetation growth in the sea. They also feed on encrusting animals such as barnacles and sea mats. A lack of sea-urchins in a given area can result in rapid alga) growth, and in some sensitive habitats such as coral reefs this can have serious effects on other organisms; the plants quickly outcompete the slower-growing corals for light and space. The edible sea-urchin is a temperate species, living on hard substrates and among larger algae in coastal waters around northwestern Europe. Compared with other species of sea-urchin, it is quite large and has a pale, rosy-pink test. The test is the shell-like internal skeleton that is so close to the outside of the animal that it appears to be a shell. However, it is covered by thin living tissue. The skeleton of sea-urchins, as in other echinoderms, is made up of crystals of calcium carbonate perforated by spaces. (As a result, it is easily occupied by minerals after the animal’s death, so it fossilizes well.) The sea-urchin’s test bears whitish-pink needle shaped spines with purple tips. They are used for defense against predators and as an aid to the animal’s movement. Between the spines are the pedicellariae minute pincerlike organs carried on stalks-that are used for grooming. As well as spines sea-urchins also have many long, branched tentacles, called tube-feet, with suckers on the end, which are arranged in rows up and down the animals. They are hollow and can be filled with water from inside the animal and extended by hydraulic pressure. They are used for movement and balance, and in some species help act as a sort of camouflage. Like other sea-urchins, the edible sea-urchin has a mouth on the underside of the test with a complex arrangement of five jaws with teeth that are extruded (thrust out) to scrape algae and other encrusting plant and animal life from the rocks. When removed from the test but still joined together, the jaws resemble a Greek lantern; Aristotle referred to them as lantern teeth, and today the jaw arrangement is called an Aristotle’s lantern.
Hunted Out
The edible sea-urchin was for centuries fished for its roe (eggs); the food was considered a delicacy in Tudor times (between 1485 and 1603). Unlike the smaller Mediterranean species Paracentrotus lividus, which has a more delicate roe, the relatively coarse roe of the edible sea-urchin is no longer considered desirable to eat. The species is easily seen and collected under water. When the test is cleaned out by removing the intestine and reproductive organs, it makes an attractive ornament. In recent decades divers have collected edible sea-urchins from southwestern Britain in such large numbers that scientists now believe that a population crash may be imminent. However, further information is needed about the state of the natural populations of edible sea-urchin around northwestern Europe and the sea-urchin’s life span so that measures can be taken to protect them.
DATA PANEL
Edible sea-urchin
- Related endangered species: Probably several, including the rock borer Paracentrotus lividus (no common name) not listed by IUCN. The species has been seriously overfished for its edible roe in parts of France and Ireland
- Habitat: Rocks and seaweeds from the low tide mark down to 164 ft (50 m)
- Diet: Encrusting animals such as barnacles; large algae
- Breeding: Seasonal spawning; fertilization occurs in the open water;
- World population: Unknown
- Distribution: Northeastern Atlantic
- Size: Up to 6.7 in (17 cm) diameter; often smaller
- Family: Echinidae
- Form: Globular body with calcareous test bearing movable spines and extendible tube-feet ending in suckers
- Breeding: Seasonal spawning; fertilization occurs in the open water free-swimming larva feeds on minute drifting plants until it metamorphoses to form a juvenile urchin
Have seen 6in or more of sea urchins along the coast of the heart of Philippines, Romblon they are white in appearance with the tip of the spines purple. I was wondering if those sea urchins are edible as they are like ripe for the picking.