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Spineless Sea Urchin

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The Spineless Sea Urchin (Abatus cordatus) is a marine (saltwater) invertebrate echinoderm. It is also known as the Kangaroo Sea Urchin because the female keeps her eggs in a pocket or pouch. It is related to starfish (sea stars). 

The Spineless Sea Urchin has a hard, spherical (ball-shaped) shell, called a test, with no backbone and no spines sticking out of its body (like the Spiny Sea Urchin). Its mouth, with a small jaw, is in the centre of the urchin on its underside. It does not have eyes. It is sensitive to touch, light, and chemicals, due to the numerous sense cells around its mouth.

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Brittle Star

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The Bristle Star (Ophiomastix janualis) is a tropical marine (saltwater) echinoderm, related to the starfish. It is also called a Serpent (Snake) Star. It is not a fish. It is an invertebrate (animal with no backbone) and an ophiuroid.

The Bristle Star has five long, slender whip-like arms radiating symmetrically from a central coin-shaped or disc-shaped body. The body contains its mouth and internal organs. Its mouth, on the underside of the body, has five toothed jaws. Its mouth is both the entrance to its internal organs and the exit to release waste.

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Organ-Pipe Coral

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The Organ-Pipe Coral (Tubipora musica) is a soft marine (saltwater) coral. It is related to the sea fan.

The Organ-Pipe Coral is a mat coral – it looks like a carpet or mat on the bottom of the ocean. The polyps live inside long, bright red parallel tubes, called sclerites, connected by horizontal platforms. The tubes calcify into a hard, red external skeleton (often used in jewelry), which makes it seem like a stony coral instead of a soft coral. Therefore, it is a soft coral with a unique hard skeleton.

It lives in a colony (the mat is actually many polyps). The series of polyps have an eight-fold symmetry – eight feather-like tentacles. The tubes look like the pipes of a musical organ. The polyps can be white, silver, cream or green. Mostly the tubes can’t be seen during the day because the tentacles cover the tubes. At night, the tentacles go inside the tubes.

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Scallop

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The Scallop (Chlamys opercularis) is a small marine (saltwater) bivalve mollusc. It is also called a Clam, but it is not a true clam (a true clam does not live near the bottom of the ocean).

The Scallop has a white-creamy-yellowish-brown shell, called a mantle, with bilateral symmetry – its two valves are the same – connected by two hinge-type adductor muscles that enable it to open and close. Near the hinge are auricles. Auricles, like ears, are triangular protusions. The mantle has many ridges, called ribs, that fan out from the hinge. It has a foot which helps it to bury itself on the ocean floor.

The Scallop has 10–100 very small eyes along the edge of its mantle, which can detect light and motion. Each eye has a lens, a two-layered retina, and a concave mirror.

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Common Sea Urchin

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The Common Sea Urchin (Echinus esculentus) is a spiny marine (saltwater) echinoderm in the Echinidae family. It is an animal that lives on the bottom of the ocean. It is related to the Starfish (Sea Star). It is also called a Sea Hedgehog.

The Common Sea Urchin has a hard shell, called a test. It is spherical (round like a globe), shiny and spiny. Young urchins have bilateral symmetry, and as they become adults, they have fivefold symmetry (similar to starfish with five appendages). Its mouth, with a small jaw, is in the centre of the urchin on its underside.

It does not have eyes. It is sensitive to touch, light, and chemicals, due to the numerous sensitive cells in its spines, tube feet, and around its mouth.

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RESEARCH: The wing of a bird may determine the shape of her eggs

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Eggs can be big or small, round or pointy.

There are many explanations for the variety of birds’ egg shapes.

Mary Caswell Stoddard and her researchers of Princeton University analysed the shape almost 50,000 eggs from around 1,400 species of birds in museum collections. She thinks the shape of a female bird’s wing determines the shape of the eggs.

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