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Internal Features of Insects 1 Major Internal Systems of the Insect Body Respiration Digestion Circulation Excretion INSECT INTERNAL ANATOMY Reproduction Nervous System Hormones 2 1 Insect Respiratory System Insect Muscles – • Most muscles attach to the inside walls of the exoskeleton. • These muscles control movement: – Mouthparts, legs and wings – Air through the trachea – Food through the digestive system • Most muscle activity is controlled by the nervous system (just as with humans). Insects breathe through small openings called spiracles that are found along the thorax and abdomen http://www.cals.ncsu.edu/course/ent425/library/tutorials/external_anatomy/locomotion.html 3 4 Drain fly larvae University of Nebraska-Lincoln Air travels throughout the body through tubes called tracheae Unit 3 5 Internal Features of Insects 2 Insect Respiratory System Insect Respiratory System • Some aquatic insects breathe through gills discoverlife.org • Mosquitoes larvae breathe through siphons photobucket.com Respiratory Video Digestive System The digestive system is a tube that is divided basically into three sections: Foregut Midgut Hindgut 10 Digestive System Foregut – mostly used for temporary storage, mixing and grinding. Digestive System Midgut - where most digestion and absorption of food occurs Internal Features of Insects 3 Insect Digestive System Digestive System Hindgut - where wastes are removed. University of Nebraska-Lincoln Insect Digestion of Food Insect Circulatory System Most insects digest carbohydrates, proteins and fats. Some insects, such as termites, have microorganisms called “symbionts” in their gut that digest cellulose or other materials for them to use as nutrients. Insects have an “open” circulatory system. – Their blood is about 90% liquid (plasma) – Blood travels through some blood vessels, then dumps into an open cavity. – Insects have a dorsal blood vessel that serves as their “heart”. – Accessory pulsating organs help push the blood through the legs, wings and antennae 15 Circulatory Video Dorsal Blood Vessel Aorta 16 “Heart” 17 Internal Features of Insects 4 The Insect Circulatory System The Insect Circulatory System – With most insects, blood is not used to transport oxygen – Bloodworms - Hemoglobin binds and holds a reserve supply of oxygen for times when oxygen in water is low. •Transports nutrients and waste products •Transports chemicals that are important for insect growth and development (hormones). •Certain cells in the blood heal wounds and also dispose of bacteria and other organisms •Maintains or changes the pressure inside the body 19 Flyguys.net Insect Excretory System 20 Insect Excretory System Malpighian tubules – insect “kidneys” located at the junction of the midgut and hindgut Purpose - similar to our kidneys – Remove wastes from the blood and digestive systems. – Filter out water for recycling through the body. 22 21 Reproductive System Reproductive System Most insect species have two genders (sexes) - male and female Some insects can control the gender of their offspring. For example - bees – unfertilized eggs produce males (drones) – fertilized eggs produce females – they may produce males at certain times of the year only 23 Parthenogenesis - reproduction without mating All offspring from one female are genetically identical to her. (Example – aphids and whiteflies) Can increases the likelihood of pesticide resistance developing. 24 Internal Features of Insects 5 Nervous System Nervous System • Insects have a ventral nerve cord (the opposite of mammals and other vertebrates) Role of the nervous system: • They have a collection of nerve cells that compose a “brain” • They have a pair of nerve centers in each body segment, called ganglia – Collect and transmit sensory information such as: – Temperature, light, chemicals, etc. – Control responses (movement, molting, eating, etc.) 25 How the Nervous System Works 1. Nerves control the muscles 2. A nerve impulse moves along the nerve cell (neuron). 26 How the Nervous System Works 1. Acetylcholine acts as “chemical bridge” across the gap. 2. Acetylcholinesterase - resets the synapse 3. The impulse then travels across a gap (synapse) between the neuron and the muscle that it controls Unit 3 University of Nebraska-Lincoln 28 27 How the Nervous System Works Hormone Production Organophosphate pesticides (e.g, Dursban and diazinon, Orthene) inhibit or interfere with acetylcholinesterase and prevent the nerves from resetting. Result: – nerve keeps sending signals (doesn’t reset) – muscles keep twitching – insect dies Same affect on human nervous systems HORMONE - a chemical formed in an organ or body tissue that travels through the body and causes some effect on another body part. Some hormones control – Molting – Growth and maturation to adulthood 29 30 Internal Features of Insects 6 INSECT GROWTH & METAMORPHOSIS Hormone Production Some insecticides mimic these hormones - prevent the insect from molting or maturing or cause it to become an adult too quickly. ADULT NYMPH EGG 31 Questions? 32