Overview

Birth of a Coral Island

Nature of Coral

Flowers of the Reef

The Echinoderms

Amazing Defensive Weapon

Turtles of the Reef

Strange Behavior of Reef Crabs

A Deadly Killer

World's Largest Shellfish

Strange Oysters of the Reef

Rare fish of the Coral Seas

Unusual Vegetation

Birds in Millions

Angling Unsurpassed

the echinoderms

The great group of Echinoderms, embracing sea stars, brittle stars, sea urchins and beche-de-mer, is prolifically represented throughout the whole Barrier Reef area, and, as obtains with most other forms of life abounding there, are distinguished by their diversity of form and curious habits.

Sea Stars. The sea stars may be almost circular, like huge pin-cushions, several pounds in weight, with the five arms characteristic of the race reduced to mere vestiges. On the other hand, they may have a central disk so reduced that it is scarcely recognizable as such, with long spreading arms radiating from it. One of the latter, known as Linckia, is a beautiful cobalt blue, and is a conspicuous object throughout the entire length of the Barrier Reef.

Brittle Stars. Equally common are the brittle stars, the long and delicate arms of which are so frail that if you pick the animal up it is almost inevitable that some of the arms will break off in your fingers. It can snap off the arms or portions of them at will, but it is not discomfited for long because they are quickly regenerated. This replacement of lost parts is one of the most curious features of the whole group of Echinoderms, and it reaches its greatest degree of development in the beche-de­mer, described in the following pages.

Sea Urchins. Abundant, also, are the sea urchins, the large, limy cases of which are occasionally found washed up on beaches round the Australian coast, where they have received the popular name of "sea-eggs." Projecting through holes in this case, when the animal is alive, is a series of spines. In some Barrier Reef species they are heavy and blunt like slate pencils, but in others they are as long as knitting needles and very sharp. It is almost impossible to handle a needle-spined sea-urchin without some of the spines breaking off in one's fingers. These spines afford the animal most effective protection, and they are also the means by which it is able to crawl about. In addition to spines, sea urchins have small, fleshy, tentacular-like structures, known as tube-feet, projecting through pores in their shells. These gather up the food and convey it to the mouth which is situated in the centre of the under surface of the case.

Beche-De-Mer. 'Amongst the most common of all forms of life on the Great Barrier Reef is the beche-de-mer, also known as trepang and sea-cucumber. There are many species, some a few inches in length, others up to two feet long. The skin of the beche-de-mer is tough and leathery, and protruding through the lower surface are great numbers of tube-feet by means of which it is able to crawl slowly over the sand. In color, beche-de-mer range from a mottled creamy white, through various shades of yellow, orange and brown, to black. The majority are dark and drab, and the commonest species in the pools on the Reef flats is black above and bright crimson below.

Wherever you go on the Reef, beche­de-mer will be found in abundance; and as you gaze on them you will probably decide that amongst the brilliant gems you have found a creature that is drab and uninteresting. So you pick one up to examine it more closely. There is no danger because they are quite harmless. From one end you will find a stream of water oozes, leaving the animal soft and flabby in your hands. Then, your inter­est aroused no further, you throw it back into the water, and suddenly you find a great stream of white threads issuing from its hinder end. They appear to be never-ending, and spread out in the water in all directions, adhering closely to everything they touch.

It would seem that this cotton-spinning is a protective device, for if the beche-de-mer is attacked, its pursuer is likely to become entangled in the sticky threads and, intent on its own escape from the enveloping mesh, completely forget about its intended victim.