Krill are an important part of Antarctic food chains. These small crustaceans feed on microscopic plants and animals, and are eaten by whales, seals, birds, and fish. Krill live in the Antarctic Ocean, where they form gigantic swarms close to the water’s surface. these can contain 25 billion animals.
Red hermit crabs have soft abdomen unlike most crabs. They use old shells from other animals for protection. They grow during their adult life, and often have to move to a bigger shell. The red hermut crab is one of the largest species of crabs. It uses its long claws to catch small animals and pick up pieces of food.
Crustaceans is a group of arthropods that includes crayfish, lobsters, crabs, and shrimp. Most have a body with three parts - head, thorax, and abdomen - but in some species the head and thorax are joined. All live in the water, except wood lice and their relatives.
After insects, mollusks are the largest invertebrate group. They include gastripods, such as slugs and snails;
bivalves, such as clams and oysters; and cephalods, such as cuttlefish, octopuses, and squid. Many have a hard shell, and feed with a rasping, toothed tongue.
Echinoderms are the only animals that have five of each main body part. They have a hard, chalky case that
may be covered with spines. Echinoderms move by using hundreds of fluid-filled tube feet. Found only in the sea, they include brittle stars, starfish, sea urchins, and sea cucumbers. Most live in shallow water, but brittle stars live on the deep-sea floor.
Sponges and cnidarians are among the simplest kinds of invertebrates. All live in the water, usually the sea. Sponges consist of cells that work together to form a living food sieve. Cnidarians capture their prey by shooting out barbed, stinging threads from their tentacles. Some, such as jellyfish, can swim, while others, such as corals and sea anemones, stay in one place.
Two closely related groups of arthropods are centipedes and millipedes. Both have a body made up of many segments, and a head bearing simple eyes and antennae. Centipeded have a flattened body and one pair of legs on each segment.
Hemoglobin (Hob) is a respiratory pigment that vastly
Increases the binding power of the blood for oxygen. For example, in the Port Jackson shark (Heterogonous portjacksoni) at 20°C, 93% of the oxygen carried by the blood is reversibly bound to the hemoglobin while 7% is physically dissolved in the plasma at saturation.In colder environments the plasma percentage may increase (12% in the Antarctic nototheniid Tresnatomus bernacchii at -1.5°C). Indeed, the Antarctic crocodile ice fishes (family Channichthyidae) carry no hemoglobin in their blood at all. The ice fishes survive because (1) their metabolic oxygen requirements are low and the environmental dissolved oxygen is high in the consistently cold Antarctic waters; (2) their sluggish activity levels are adequate to catch sufficient quantities of the plentiful krill and small fish; and (3) special cardiovascular adaptations (e.g., comparatively large heart and blood volume with relatively low resistance capillaries) promote efficient movement of their blood.
Oxygen Fish need energy to move, to find and requirements digest food, to grow, and to reproduce in addition to maintaining the body and internal environment. Energy stored in their food must be metabolically converted to power for these various bodily functions. Oxygen, along with an organic substrate, is needed for all oxidative metabolic processes. Oxidative (or aerobic) metabolic pathways are dominant in organisms which have a fairly reliable oxygen source because they are bio-chemically more efficient than anaerobic pathways. The amount of oxygen which a fish requires for these processes over a given length of time is called its oxygen consumption rate. Oxygen consumption rate can be affected by a variety of factors. Three of the most significant of these are body weight, level of activity, and environmental temperature. In general, larger fish use more total oxygen per hour than smaller fish, although per unit body weight, smaller fish use more oxy-n than larger specimens. In similar manner, swimming fish use moneymen than resting animals
Gills are the main site of gas exchange in
almost all fishes. The gills consist of bonyor cartilaginous arches which anchor pairs of gill filaments. The numerous, minute secondary lamellae which protrude from both sides of each filament are the primary sites of gas exchange.