E3.BugsF10 - Arthropods Arachnids Principle Classes of...

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Unformatted text preview: Arthropods Arachnids Principle Classes of Arthropods – includes spiders, scorpions, ticks, and mites • Crustacea 50 µ m • Arachnida • Myriopoda • Insecta (a) Scorpions have pedipalps that are pincers (b) Dust mites are ubiquitous scavengers in (c) Web-building spiders are generally specialized for defense and the capture of human dwellings but are harmless except most active during the daytime. food. The tip of the tail bears a poisonous to those people who are allergic to them stinger. (colorized SEM). Figure 33.31a –c Myriopoda Arachnids • Two tagmata: cephalothorax & abdomen Centipedes & millipedes – six pairs of appendages: • 1 pair chelicerae w/ venom fangs or claws • 1 pair pedipalps — sensory / food manipulation • 4 pairs walking legs Digestive gland Intestine Heart Stomach • Two tagmata: head & trunk (= thorax + abdomen) • Head w/ 4 segments & 4 pairs of appendages • Trunk w/ many segments — 1 pair of legs/segment Brain Eyes Poison gland Ovary Anus Book lung Gonopore Sperm Chelicera receptacle Silk gland (exit for eggs) Spinnerets Pedipalp Figure 33.34 Figure 33.33 Figure 33.32 Myriopoda Insects Centipedes & millipedes • Two tagmata: head & trunk • Head : • External anatomy The insect body has three tagmata : head , thorax , and abdomen . • The segmentation of the thorax and abdomen are obvious, but the segments that form the head are fused . – 1 pair of antennae – Mouth parts: 1 pair of mandibles (jaws) + 2 pair of maxillae • Trunk: Abdomen Thorax Head – Legs of first trunk segment = maxillipeds • Feeding limbs • Venom claws in centipedes Compound eye – Remaining segments have walking legs Antennae Figure 33.35 Heyer 1 Arthropods Insects Insects • External anatomy • External anatomy — head Head: 6 segments Thorax: 3 segments Abdomen: 11 segments External morphology of insects http:// ltreadwell. ifas .ufl .edu/insects/03external.htm Insects • Mouthparts & feeding behavior Insects • Mouthparts & feeding behavior Heyer External morphology of insects http:// ltreadwell. ifas .ufl .edu/insects/03external.htm Insects • Mouthparts & feeding behavior Insects • Mouthparts & feeding behavior 2 Arthropods Insects Insects • Mouthparts & feeding behavior • Mouthparts & feeding behavior Insects Metamorphic Development Cerebral ganglion. The two nerve cords meet in the head, where the ganglia of several anterior segments are fused into a cerebral ganglion (brain). The antennae, eyes, and other sense organs are concentrated on the head. • Internal anatomy • Ametabolous: direct development without metamorphosis • Hemimetabolous: gradual or incomplete metamorphosis • Holometabolous: complete metamorphosis Heart. Ovary Dorsal artery Crop Anus Malpighian tubules. Excretory organs— out-pocketings of the digestive tract. Vagina Tracheal tubes. Gas exchange by a system of branched, chitin-lined tubes that infiltrate the body and carry oxygen directly to cells. Opens to the outside of the body through spiracles that can control air flow and water loss by opening or closing. Nerve cords. A pair of ventral nerve cords with several segmental ganglia. Mouthparts . Formed from several pairs of modified appendages. Insect Biology and Ecology: A Primer http://www.nysaes .cornell.edu /ent/biocontrol/info/primer.html Figure 33.35 Once again, Holometabolous Development • Metamorphosis occurs during a pupal stage Conflicting phylogenetic data! III II (a) Larva (caterpillar) (b) Pupa (c) Pupa (d) Emerging adult q Figure 33.6a – e Heyer (e) Adult q I I. Traditional taxonomy from mouth parts & development II. Revised taxonomy based on mitochondrial DNA sequences III. Revised taxonomy based on comprehensive comparisons of anatomy, neurology, development & DNA. Did terrestrial arthropods arise independently? Did crustaceans derive from terrestrial arthropods? 3 ...
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