My Science School

On top of its head, the sea spider has a knobby projection bearing two, three, or four simple eyes. The head ends in a snout with a sucking mouth. Sea spiders feed by sucking the body juices of such marine animals as sea anemones, sponges, and sea squirts. They prefers a liquid diet which they eat standing up. They insert their long proboscis into their prey, sucking up the nutrients.

Most sea spiders eat other animals and attack invertebrates (in-VER-teh-brehts), or animals without backbones that are attached to the ocean bottom, such as corals, clams, and marine worms. A few species feed on red algae (AL-jee), a special group of plantlike ocean life that lacks true roots, stems, or leaves. Other sea spiders feed on bits of plant and animal tissues that build up under colonies of invertebrates. 

 

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Sea spiders can be identified by their long legs and tiny body. The sea spider has a small, narrow body. It usually has four pairs of long, thin legs attached to the abdomen. Attached to the head there are usually three other pairs of Appendages – a pair called chelicerae, used for grasping food; a pair of sensory projections called palps; and a pair of egg-carrying legs (sometimes underdeveloped or absent in the female). The female lays round masses of eggs on the egg-carrying legs of the male, which carries the eggs until they hatch.

Sea spiders usually come in amazingly beautiful colours. The yellow-kneed sea spider, for example, has bright yellow stripes contrasting a red body. Other sea spiders have purple stripes, bright yellow solid bodies, or black and white stripes, and so on.

 

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Pycnogonida (sea spiders) can be found all over the globe, from shallow tropical seas, to freezing oceans, to the deepest parts of the ocean over four miles below the surface. In fact, there are around 1,300 varieties of these creatures. Species found in coastal waters are usually small and have a leg span of about 1 inch (2.5 cm), those living at great depths, up to 24 inches (60 cm). The largest of them all the giant sea spider is found only in the icy water of the Antarctic. Sea spiders walk about on the ocean bottom on their slender legs or crawl among plants and animals; some may tread water.

Sea spiders either walk along the bottom with their stilt-like legs or swim just above it using an umbrella pulsing motion.[6] Sea spiders are mostly carnivorous predators or scavengers that feed on cnidarians, sponges, polychaetes, and bryozoans. Although they can feed by inserting their proboscis into sea anemones, which are much larger, most sea anemones survive this ordeal, making the sea spider a parasite rather than a predator of anemones.

 

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Sea spiders are related to insects, like ants or bees, as well as the arachnid group for which they are named, which contains spiders and centipedes. However, their name is a misnomer. Sea spiders are not actually spiders. They are marine arthropods of the class Pycnogonida. All living things are organized into groups, with successive groups sharing more characteristics in common. In one of the largest categories, kingdom, sea spiders are classified in Animalia. Many people are surprised to find out what scientists consider an animal! Although we usually think of dogs and cats as animals, any multicellular organism that is mobile and eats to get food is considered an animal in the scientific world. Animals are divided into smaller groups based on shared characteristics. Sea spiders are a member of the phylum Arthropoda. This means they are related to insects, like ants or bees, as well as the arachnid group for which they are named, which contains spiders and centipedes. However, their name is a misnomer. Sea spiders are not actually spiders. They fall in a different subgroup of Arthropoda, called Pycnogonida.

 

Picture Credit : Google