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Chapter 39: Annelids, molluscs, nematodes and arthropods Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-1 Fig. 39.1: Phylogeny of the protostomes Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-2 Body cavities • Internal body cavity surrounding organs • Coelom – body cavity entirely lined with mesoderm – examples: annelids, molluscs, arthropods • Pseudocoel – body cavity not entirely lined with mesoderm – example: nematodes Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-3 Phylum Annelida • Segmented worms – marine worms, earthworms, leeches • Metameric segmentation – repetition of functional units in body • Characteristics – – – – – closed vascular (circulatory) system through-gut epidermal setae/chaetae (bristles) hydrostatic skeleton septa Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-4 Classification • Class Polychaeta (marine worms, bristle worms) • Class Clitellata (worms with clitellum) – subclass Oligochaeta (earthworms) – subclass Hirudinea (leeches) Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-5 The annelid body • Body divided into three parts • Prostomium – presegmental – contains brain • Soma – segmented body • Pygidium – postsegmental – contains anus Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-6 Fig. 39.3: Structure of earthworm (a) General body morphology (b) Three-dimensional structure of individual segments Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-7 Fig. 39.3: Structure of earthworm (cont.) (c) Dorsal view inside the body Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-8 Locomotion • Transverse septa divide body cavity into separate units – allow hydrostatic pressure to vary between segments • Body wall can change shape – elongation – contraction • Movement by peristaltic locomotion – crawling – burrowing Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-9 Respiration and circulation • Transverse septa prevent free circulation of body fluid – dissolved gases, nutrients etc. cannot circulate • Requires system for transport – closed circulatory system – passes through septa • Respiratory pigments – erythrocruorin – chlorocruorin Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-10 Excretion • Excretory products in body fluid – paired excretory organs (nephridia) in each segment – protonephridia blind tubes with flagellated cells embryos some polychaetes – metanephridia funnel-shaped oligochaetes, leeches, many polychaetes Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-11 Phylum Mollusca • Molluscs – clams, mussels, snails, slugs, octopus, squid, chitons • Diverse group • Characteristics – – – – – – mantle visceral mass foot radula shell veliger Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-12 Fig. 39.10: Phylogeny of major mollusc groups Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-13 Classification • • • • • • Mollusca is the second-largest phylum Class Polyplacophora (chitons) Class Bivalvia (clams, mussels, oysters) Class Gastropoda (snails, slugs, sea slugs) Class Cephalopoda (squid, octopus, cuttlefish) Other classes (Neopilina, tusk shells) Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-14 Molluscan body plan • Mantle – fold of body wall enclosing mantle cavity – secretes shell • Visceral mass – contains body organs – organs open into mantle cavity • Foot – locomotion – may be highly modified Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-15 Molluscan body plan (cont.) • Radula – feeding structure – rasping teeth on flexible strip • Shell – one, two or eight elements – may be absent • Veliger – second larval stage Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-16 Fig. 39.11: Body structure of molluscs (a) (d) (b) (e) (c) Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-17 Bivalvia (bivalves) • Adaptations to sessile existence as adults • Locomotion – reduced, laterally-compressed foot burrowing • Feeding – – – – most species are filter-feeders lack radula gill surfaces expanded for food gathering and sorting cilia sort and transport particles to mouth Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-18 Gastropoda (gastropods) • Most diverse group of molluscs – only group with terrestrial species • Single coiled shell – reduced or lost in some species • Visceral mass undergoes torsion – – – – rotation through 180° brings posterior structures to anterior secondary detorsion in some species torsion not the same as coiling in shells Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-19 Fig. 39.19b: Land snail Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-20 Cephalopoda (cephalopods) • Octopus, squid, cuttlefish, nautilus • Arms and tentacles for manipulating prey • Complex brains and eyes – colour vision – visual communication – chromatophores under nervous and hormonal control • High metabolic rate – closed circulatory system – accessory branchial heart at base of each gill Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-21 Phylum Nematoda • Roundworms • Free-living or endoparasitic • Characteristics – – – – – not segmented fixed number of cells (eutely) lack cilia lack circular muscle covered in cuticle Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-22 Phylum Arthropoda • Most diverse phylum • Spiders, crabs, millipedes, insects • Characteristics – – – – jointed limbs chitinous exoskeleton, sometimes with calcium metameric segmentation tagmatisation (segments clustered into functional regions or tagmata) Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-23 Fig. 39.24: Arthropod phylogeny Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-24 Classification • Chelicerate arthropods (arthropods with chelicerae) – subphylum Chelicerata (spiders, horseshoe crabs) • Mandibulate arthropods (arthropods with mandibles) – subphylum Myriapoda (millipedes, centipedes) – subphylum Crustacea (prawns, crabs, yabbies) – subphylum Insecta (insects) Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-25 Features of the arthropod body • Exoskeleton – continuous integument – thickened and rigid in regions (sclerites) – thin and flexible between sclerites • Does not expand as animal grows – must be shed (moulted) periodically to allow growth Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-26 Subphylum Chelicerata • Class Pycnogonida (sea spiders) • Class Merostomata (horseshoe crabs) • Class Arachnida (spiders and allies) – – – – – spiders scorpions pseudoscorpions ticks and mites others Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-27 Fig. 39.29a: Spider anatomy Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-28 The chelicerate body • Body divided into – prosoma (cephalothorax) – opisthosoma (abdomen) • Appendages – 1st pair = chelicerae (claw-like for feeding) – 2nd pair = pedipalps (manipulation) – 3rd to 6th pair = legs • Book lungs or book gills for respiration • Excretion by coxal glands and Malpighian tubules Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-29 Mandibulate arthropods (Mandibulata) • Mouthparts with mandibles not chelicerae • One or two pairs of antennae • Compound eyes Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-30 Subphylum Myriapoda • Class Chilopoda (centipedes) – – – – typically dorso-ventrally flattened one pair of legs per segment poison claws at anterior carnivorous • Class Diplopoda (millipedes) – – – – typically rounded in cross-section two pairs of legs per segment may produce fluid from repugnatorial glands herbivorous Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-31 Subphylum Crustacea • • • • • Class Branchiopoda (water fleas) Class Copepoda (copepods) Class Ostracoda (seed shrimps) Class Malacostraca (crabs, crayfish, prawns) Other classes Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-32 The crustacean body • Multiple pairs of biramous (branched) appendages – each appendage with endopodite and exopodite – 2 pairs antennae, 1 pair mandibles, 2 pairs maxillae • Compound eyes, simple ocelli (clustered as median eye) • Body surface and gills for gas exchange • Antennal and maxillary glands for excretion Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-33 Reproduction • Sexes usually separate – some hermaphroditic (e.g. barnacles) – some parthenogenetic (e.g. branchiopods) • Egg-brooding common • Nauplius larva – one eye, three pairs of appendages – complex larvae in decapods and barnacles • Larval stage sometimes suppressed Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-34 Subphylum Hexapoda (insects and their relatives) • Class Apterygota (wingless insects) – springtails, silverfish, others • Class Pterygota (winged insects) – exopterygotes cockroaches, mantids, grasshoppers, others – endopterygotes beetles, flies, butterflies, moths, ants, others Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-35 Insect body structure • Three pairs of uniramous (unbranched) appendages • One or two pairs of wings • Compound eyes, simple ocelli • Tracheal system for gas exchange • Malpighian tubules excreting insoluble uric acid Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-36 Fig. 39.34: External features of a grasshopper Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-37 Metamorphosis • Some insect groups undergo a change in form between the larval and adult stages • Exopterygotes change form gradually, developing adult characteristics with each moult – incomplete metamorphosis • Endopterygotes undergo a major change between the last larval stage and the adult stage – complete metamorphosis Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-38 Complete metamorphosis Larva (caterpillar, maggot, grub) Pupa (chrysalis) Imago (adult butterfly, fly, beetle) Larva and adult occupy different niches Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-39 Fig. 39.38: Butterfly life stages Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-40 Question 1: Which characteristic is probably the most important for allowing insects to diversify on land? a) Antennae b) Wings c) Eyes d) Exoskeleton e) Bilateral symmetry Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-41 Summary • Annelid and arthropod bodies show metameric segmentation with serial repetition on functional units • Molluscs are a diverse group of aquatic and terrestrial animals with complex and varied body plans • Arthropods are the most abundant phylum and can be found in all habitats • Arthropods include two major lines of evolution: the chelicerata and mandibulata Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 39-42