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Internal anatomy and physiology Internal anatomy and physiology We will not be going over all of these in class! Check out these slides and your course notes, and just let me know if you have questions. Most of this is fairly straightforward. Muscles and Locomotion • Sole purpose: convert stored energy into mechanical energy • Do this by contracting Internal anatomy and physiology 3.1 3.2 3.3 3.4 3.5 3.6 Muscles and locomotion The nervous system The endocrine system The circulatory system The tracheal system The gut, digestion, and nutrition Muscles and Locomotion Questions • How do direct and indirect muscles operate differently in powering flight? • How are larval insects able to get around without a sclerotized cuticle? Muscles need an anchor… how do they do this in insects? o Muscle receives signal from nervous system o Muscle then shortens (or contracts) • Contractions vary depending on location and orientation of muscles Figure 3.2 in textbook 1 A focus on flight… FLIGHT Insects power flight by: Direct flight mechanism (muscles attach to wing) o Ancestral insects use only this o More derived insects use this and… Indirect flight mechansim (wings and muscles don’t attach) 3.2 Nervous system Setae/eyes/antennae 3.1 Muscles and Locomotion 2 ways muscles can attach (both appendages and organs) o EXTRINSIC • Muscle attaches appendage to body cavity o INTRINSIC • Muscle remains in appendage or in a single structure Central Nervous System Brain- Dorsal ganglionic center of the head. Afferent neurons Ganglia Subesophageal ganglion- located below INTERNEURONS the pharynx. Ventral nerve cord- contains chain of Efferent neurons thoracic and abdominal ganglia. Muscles/glands How do larvae get around with such thin, flexible cuticle? DIRECT FLIGHT MECHANISM INDIRECT FLIGHT MECHANISM 2 The hydrostatic skeleton 3.2 Nervous system Insect nervous system is decentralized o Instead of going to and from central brain, signals go to and from GANGLIA Variable Arrangement of CNS in Different Insects Most specialized Least specialized The endocrine system Questions • How are endocrine and exocrine glands similar and different in function? • Why would an insect secrete chemicals to the outside world? • What are the major endocrine glands? • Which glands release JH, Ecdysone, and PTTH? Why are these hormones important? Cockroach Fusion of ganglia Scarab beetle The endocrine system • System = glands and what they produce • 2 classes of GLANDS o Both innervated by nervous system The endocrine system EXOCRINE GLANDS Emit - single cells or aggregations of cells • Can be anywhere in body but usually an association with epidermal layer… why? EXOCRINE GLANDS o Send chemicals/signals outside body ENDOCRINE GLANDS o Send chemicals/signals inside body 3 The endocrine system The endocrine system EXOCRINE GLANDS What would an insect excrete? Pheromones: used in intraspecific communication only! (used incorrectly by David Attenborough /) There are several types of pheromones, and we will talk about these in the Sensory Systems section of the course. Below, insects using sex pheromones (left) and aggregation pheromones (right). EXOCRINE GLANDS What would an insect excrete? Semiochemicals: Chemical odors important in both interspecific and intraspecific communication (both across and within species). The endocrine system The endocrine system EXOCRINE GLANDS What would an insect excrete? Allelochemicals: Chemical odors important to interspecific communication only. EXOCRINE GLANDS Many chemicals released from the exocrine glands are Semiochemicals. Some examples include… 1) Defense chemicals/signals o venoms, alarm pheromones o Bombardier beetles The endocrine system EXOCRINE GLANDS Many chemicals released from the exocrine glands are Semiochemicals. Some examples include… 2) Mate attraction chemicals/signals - Sex Pheromones The endocrine system EXOCRINE GLANDS Many chemicals released from the exocrine glands are Semiochemicals. Some examples include… 3) Trail-marking pheromones, aggregation pheromones 4 The endocrine system ENDOCRINE GLANDS • Can be one cell or clusters of cells • No “ducts” and no association with epidermis • A LOT more complex than exocrine system • Cascading affects • Complex combinations of hormones • All endocrine functions started and regulated by nervous system! Internal anatomy and physiology 3.4 The circulatory system The endocrine system MAJOR ENDOCRINE GLANDS CORPORA CARDIACA • Pair of glands behind brain • Store and release NEUROHORMONES • Major one: PTTH (prothoraciotropic hormones) CORPORA ALLATA • Smaller, secrete JH (Juvenile Hormone) PROTHORACIC GLANDS • Large glands in thorax • Secrete ECDYSONE (molting hormone) 3.4 The circulatory system • What is a major difference between the circulatory systems of insects and vertebrates? • What does hemolymph contain, and what are its functions? • How does hemolymph provide protection and defense? 5 3.4 The circulatory system 3.4 The circulatory system VERY different from vertebrates Slow doesn’t mean random or stagnant… • DORSAL VESSEL maintains flow o Blood not confined in vessels/capillaries OPEN Circulatory System o “blood” called HEMOLYMPH o Functions of both blood and lymph • Do NOT rely on circulatory system for O2 o Long tube along dorsal midline o It doesn’t have to be fast! 3.4 The circulatory system 3.4 The circulatory system DORSAL VESSEL It’s divided into two parts: Hemolymph Flows posterior to anterior o AORTA (anterior) o HEART (posterior) • ALARY MUSCLES on both ends of heart • OSTIA (valves) at posterior ends o i.e. rear to head o Force forward creates a current inside insect o Hemolymph infuses organs on its return flow Accessory pumping structures – o Next to/in appendages, aid with circulation o Blood circulates through legs, antennae and o WINGS 3.4 The circulatory system 6 Hemolymph Hemolymph contains an array of proteins, lipids, hormones, carbohydrates, salts, etc ¾ Functions ¾ ¾ ¾ ¾ Hormone transport Nutrient storage and distribution Waste removal Insect defense ¾ 20 - 40% of body weight in soft – bodied larvae ¾ < 20% of body weight in nymphs and adults ¾ Usually clear but also green, blue, yellow, red Internal anatomy and physiology 3.4 The circulatory system Insect immune system Hemolymph provides protection and defense from: • Physical injury • Entry of disease organisms, parasites, and foreign substances 3.5 The tracheal system How does it do this? 3.5 The tracheal system Questions • How does gas exchange occur in insects? • How does oxygen get all the way into the center of an insect? • Do all insects have spiracles? Why or why not? 3.5 The tracheal system System responsible for O2 and CO2 transport in MOST insects • Internal duct-like tubes called TRACHEA • Trachea extend out into millions of tiny branches called TRACHEOLES o Tracheoles permeate body tissues, organs, muscles, etc. o Fluid-filled, blind ends o Less than 1μm in diameter! 7 3.5 The tracheal system 3.5 The tracheal system Air enters system through SPIRACLES • Usually have an ATRIUM (chamber) with a VALVE • Some have filters to protect atrium Gas Transfer/Air Flow millions of tracheoles diffuse passively across surface How does O2 get in/CO2 get all the way in and out of there? 3.5 The tracheal system 3.5 The tracheal system How does O2 get in/CO2 get all the way in and out of there? 1. Natural diffusion gradients • O2 gradient higher on outside of insect • CO2 gradient higher on inside of insect 2. Pumping movements of the abdomen http://www.youtube.com/watch?v=lEMQxsHm8gY 3.5 The tracheal system 3.5 The tracheal system • Open versus closed tracheal system • Open versus closed tracheal system • Modifications may include the formation of air sacs or bladders GILLS Open Closed 8