Respiratory Pigments:
Respiratory pigments are organic compounds that have either metallic copper or iron that binds oxygen. These pigments may in solution within the blood or body fluids or they may be in specific blood cells. Pigments respond to high oxygen concentration by combining with oxygen but to low oxygen concentrations by releasing oxygen.
Haemoglobin is reddish pigment that contains iron as the oxygen binding metal. It is found in many invertebrates few fishes and all vertebrates. Haemoglobin may be carried within red blood cells (erythrocytes) or simple dissolved in blood.
Hemocyanin is commonly occurring pigment in molluscs and certain crustaceans. Hemocyanin contains metallic copper and has bluish colour when oxygenated and always occurs dissolved in hemolyph. It tends to release O2 easily and provides ready source of O2 to tissue as long as concentration of oxygen in environment.
Respiratory pigments raise the oxygen carrying capacity of body fluids.
Immunity in invertebrates and vertebrates:
Mechanisms (defenses) have evolved in animals that prevent unwanted cells, microorganisms or agents from upsetting the animals homeostasis. Invertebrates do not have immune system with special cells that recognize and destroy specific foreign agents. Many do have innate, internal defense mechanisms.
Molluscs and insects have granulocytes that are highly phagocytic to foreign agents and in arthropods e.g. insects these cells can encapsulate foreign agents. Nacrezation or Pearl formation is another innate defense mechanism of molluscs.
Vertebrates are continuously exposed to micro organisms, foreign macro molecules or cancer cells that can cause disease. They have immune system that defends against this exposure. Immunity (free of burden) refers to general ability of an animal to resist harmful attack. The immune response is large and specific complex of defensive elements, widely distributed throughout the body that helps the animal to defend against attack.
Specific and Non-specific defenses:
Specific Defenses: The immune response: In non-specific defenses are breached, the specific immune response is called upon for protection. This system consists of number of immunological mechanisms in which certain white blood cells (lymphocytes) recognize the presence of particular antigens and act to eliminate them. Lymphocytes may directly destroy antigens or specialized proteins (antibodies) may form to either destroy the invader or target it for destruction by other cells.
Non-specific defenses: They are those general mechanisms that are inherited as part of innate structure and function of each animal. These mechanisms act in concert as first line of defense against intruders before they can cause disease. They include biological barriers (inflammation and phagocytosis), chemical barriers (enzymatic action, interferons), general barriers (fever) and physical barriers (skin, mucous membrane).
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