Fundamental of Biology : Respiration in Invertebrate Animals There are invertebrate animals that do not have a special respiratory system, such as Porifera and some worms (Vermes). Generally, these animals breathe directly, namely by diffusion through the surface of their body. However, higher animals, such as Mollusca and Arthropoda, already have special respiratory systems, even though they are still simple. For example, Insecta and Myriapoda breathe using trachea, Arachnida animals, for example spiders, breathe using book lungs. Animals that live in water, for example Crustacea (crustaceans) and Mollusca (snails and clams) breathe using gills. a. Porifera Porifera breathe by entering water through pores (ostia) located on the entire surface of their body, into the spongocoel cavity. The next respiratory process is carried out by the neck cells (choanocytes), namely the cells that are directly adjacent to the spongocoel cavity. The flow of water that enters through the ostium into the spongocoel cavity carries oxygen as well as food substances.Binding of O2 and release of CO2 is carried out by neck cells (choanocytes). Apart from carrying out respiratory functions, neck cells also carry out the process of digestion and circulation of food substances. Next, water comes out through the osculum. b. Vermes (Worms) Most Vermes breathe using the surface of their bodies, for example members of the Platyhelminthes phylum, namely Planaria, and members of the Annelida phylum, namely earthworms (Pheretima sp.). However, some annelids breathe with gills, for example, annelids that live in water, namely Polychaeta (a group of worms with many hairs), breathe using a pair of porapodia which turn into gills. In planaria, O2 dissolved in water diffuses through the surface of the body. Likewise with CO2 emissions. In earthworms, O2 diffuses through the surface of their bodies which are wet, thin and have blood vessels. Next, O2 is circulated throughout the body by the circulatory system. CO2 as a waste of respiration is removed from the tissues by the blood vessels, then out through the body surface by diffusion. The surface of an earthworm's body is always wet. This functions to facilitate the process of O2 diffusion through the surface of the body. Try doing the following activities to prove it. c. Mollusca Soft-bodied animals (Mollusca) that live in water, such as snails, squid and shellfish (Bivalves) breathe using gills. Water flows into the gills and air exchange occurs in the gill lamellae. Molluscs that live on land, such as land snails (snails), breathe using their lungs. d. Arthropods 1) Insecta Insecta breathe using a trachea system. The tracheal system in insects, for example grasshoppers, consists of spiracles, tubes (tracheal vessels), and tracheoli.The spiracle or stigma is a way for air to enter and exit the tracheal system, found in the outer skeleton (exoskeleton), in the form of cylindrical vessels coated with chitin, located in pairs on each body segment, and is where the tracheal vessels open.In general, the spiracles are open when the insect is flying, and closed when the insect is resting. Air enters through the four pairs of front spiracles and exits through the six pairs of back spiracles. Oxygen from outside enters through the spiracles, then into the tracheal vessels, then the tracheal vessels branch oxygen can reach all tissues and internal organs of the body.Tracheoli are the smallest branches measuring ± 0.1 mn from the tracheal tube which are in direct contact with body tissue and are not coated with chitin. This tracheolus is where respiratory air exchange occurs. Tracheoli have the same function as capillaries in the transport system in vertebrates. The breathing mechanism in grasshoppers is regulated by the abdominal muscles. When the stomach muscles (abdomen) relax, the volume of the trachea is normal so that air enters.Conversely, when the abdominal muscles contract, the volume of the trachea decreases so that air comes out. The path through which respiratory air passes is external air, stigma/spiracles, tracheal tubes/vessels, tracheoli, body tissue. So, the trachea system functions to transport O2 and distribute it throughout the body, and vice versa to transport CO2 from breathing to be excreted from the body. Thus, blood in insects only functions to transport food essence and not to transport breathing air.In aquatic insects, such as mosquito larvae, air is obtained by extending a breathing tube to the surface of the water to take in air. Certain water insects have air bubbles, so they can dive underwater for long periods. For example, ladybugs Notonecta sp. have air bubbles in hair-like organs on the ventral surface.During diving, O2 in air bubbles is transferred through the tracheal system to the respiratory cells.There are also insects that have trachea gills which function to absorb air from water, or take air through fine branches similar to gills. Next, O2 is circulated through the trachea. 2) Other Arthropods Spiders (Arachnida) and scorpions (Scorpionida) breathe with book lungs. This book lung is an invagination (inward bend) of the abdomen.Book lungs have many lamellae like book pages separated by rods so that air can move freely. Air from outside enters through the spiracles by diffusion. Next, air enters between the lamella cells and diffuses with the blood vessels around the lamella. Arthropods that live in water, for example from the crustacean group (crustaceans), such as shrimp and crabs, breathe with gills. These gills grow from the base of the limb and the adjacent body wall, and extend upward into the branchial space. Each gill consists of a central axis where the lamellae or filaments connect. The flow of water is produced by the rowing movement of the dipper's gills, which are crescent-shaped extensions from one of the mouth extensions (second maxilla). In shrimp, water enters the branchial chambers behind the carapace and between the legs. Furthermore, channels within the gill axes carry blood to and from the spaces within the lamellae, respiratory air exchange taking place through the thin walls of the lamellae. The entry and exit of air is caused by muscle movements that occur regularly.Both book lungs and book gills have the same function as the function of the lungs in vertebrates.