Arthropods Chapter 46 Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Jointed Appendages and Exoskeleton Arthropods all have jointed appendages. Rigid external skeleton (exoskeleton). Protects animal and provides sites for muscle attachment. Brittle, thus there is a limit to arthropod body size due to exoskeleton thickness. Estimates of a quintillion insects alive at any one time. 1,000,000 species. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

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Classification of the Arthropods Traditional Classification Three subphyla based on morphology. Trilobites (extinct) Chelicerates - (pointed mouthparts,sometimes connected to venom glands) Mandibulates - (chewing mouthparts, sometimes modified) Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Classification of the Arthropods Doubts About Traditional Classification Key morphological traits are not as powerful as previously assumed. Revised taxonomy places insects and crustaceans as sister groups. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

General Characteristics of Arthropods Exoskeleton Molting (Ecdysis) Compound Eye-insects Composed of many ommatidia. Each covered with a lens and linked to a complex of eight retinal cells and a light sensitive core rhabdom. Apposition Eyes - Daylight Superposition Eyes - Night Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

General Characteristics of Arthropods Circulatory System Greatly reduced coelom. Open circulatory system. Nervous System Double chain of segmented ganglia running along the animal’s ventral surface. Brain appears to be inhibitor rather than stimulator. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

General Characteristics of Arthropods Respiratory System No single major respiratory organ. Small branched air ducts - tracheae. Air passes into trachea through spiracles. Spiders contain book lungs (series of leaflike plates within a chamber). Excretory System Malpighian Tubes Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Class Arachnida Major Orders Order Araneae: Spiders Order Opiliones: Daddy Longlegs Order Scorpiones: Scorpions Order Acari: Mites & ticks Have 2 body sections One pair of chelicerae & one pair of pedipalps Four pairs of walking legs. Most are carnivorous, except for mites. Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Class Arachnida Order Opiliones: Daddy Longlegs Acari: Mites and Ticks Order Scorpiones: Scorpions Order Araneae: Spiders Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Live in deep water, but migrate to shallow water in the spring. Class Merostomata Horseshoe Crabs Ancient Group. Live in deep water, but migrate to shallow water in the spring. Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Body almost entirely cephalothorax. Class Pycnogonida Sea Spiders Very small (1-3 cm). Body almost entirely cephalothorax. Completely lack excretory and respiratory systems. Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

All pass through nauplius larval stage. Class Crustacea Most have two pairs of antennae, three types of chewing appendages, and various numbers of leg pairs. All pass through nauplius larval stage. Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Crustaceans Decapods “Ten footed” Exoskeleton usually reinforced with calcium carbonate. Most body segments are fused into cephalothorax covered by carapace. Lobsters and crayfish have swimmers and uropods to aid in swimming, and may have a telson (tail spine). Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

The Myriapods Diplopoda-millipedes Class Chilopoda-centipedes Head region followed by many identical body segments. Two pairs of walking legs per segment, tubular body Not venomous Scavengers, herbivores Class Chilopoda-centipedes Head and many identical body segments One pair of walking legs per segment, body flattened Venomous Carnivores Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Largest group of organisms on earth. Class Insecta Largest group of organisms on earth. More than half of all named species on earth are insects. Hectare of lowland tropical rainforest is estimated to be inhabited by as many as 41,000 insect species. Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Head, Thorax, and Abdomen Three pairs of legs. One pair of antennae. Class Insecta External Features Three body segments Head, Thorax, and Abdomen Three pairs of legs. One pair of antennae. Modified mouthparts Solid wings Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Internal Organization Tubular digestive system. Class Insecta Internal Organization Tubular digestive system. Dilute digestive enzymes. Trachea extends throughout body. Fat Body for food storage. Sense Receptors Sensory Hairs - Linked to nerve cells. Tympanum - Found with tracheal air sacs. Pheromones - Communication signals. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Insect Life Histories Most hatch from fertilized eggs laid outside mother’s body. Undergo edysis multiple times. Instars Metamorphosis Simple Nymphs Complete Pupa (chrysalis) Larvae Controlled by hormones. Molting hormone (ecdysone). Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

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