2/17/2017. Lecture 10: Chapter 31 Protostome Diversity

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1 1 Lecture 10: Chapter 31 Protostome Diversity 2 3 Protostomes: one of two monophyletic groups of bilaterally symmetrical, coelomate animals The other group is the Deuterostomes Differ in pattern of early embryonic development Protostomes are divided into two main groups: Lophotrochozoa Flatworms, annelids, molluscs, and others Ecdysozoa Nematodes, arthropods, and others 8 9 The Protostomes have a greater number of species and number of individuals than any other group of living things Due largely to the Phylum Arthropoda, and especially the Class Insecta Over half of all species are insects! (not including the prokaryotes) Fun with Insects! Giant Insects! E.O. Wilson on Ants First, we will study the Lophotrochozoan lineage Named for 2 main shared characteristics: Lophophore (feeding structure) Suspension feeding Found in 3 phyla Trochophore larvae Has ring of cilia around middle Functions in feeding and swimming Found in many phyla within this lineage They grow continuously and incrementally and their skeletons grow with them 1

2 Rotifera Characteristics Bilateral symmetry True tissues Triploblastic Pseudocoelomate - body cavity not lined with mesoderm Alimentary canal (through-gut with mouth and anus) Corona cluster of cilia for suspension feeding Most are parthenogenic no males needed for reproduction, offspring develop from unfertilized egg When males are formed, usually to produce resistant zygote for harsh conditions Rotifera Rotifer Cyclomorphosis Change in morphology over seasonal generations Growth in spines, head structures reduce predation risk Response to selection from fish and filter-feeding predators (including other rotifers) Platyhelminthes Characteristics Bilateral symmetry Some (limited) cephalization True tissues Triploblastic: three cell layers (ectoderm, mesoderm, endoderm) Acoelomate: no body cavity Gastrovascular cavity for digestion, circulation of nutrients Same opening for intake and elimination Some free living but many parasitic Basic body plan World s Greatest Weight-Loss Supplement Maria Callas, famous opera singer Lost a significant amount of weight rumor had it by consuming a tapeworm! Sadly, she did become infected with tapeworms, but likely not intentionally (she also liked rare stake and liver tartare, raw meat dishes that were likely the source of her infection) This lead others, however, to try this fad diet! Phylum Annelida the segmented worms Bilateral symmetry Cephalization and CNS 2

3 Coelomate Segmented Parapodia and/or chaetae (varies) Regionalized digestive tract Circulatory system but no respiratory system Respiration through body wall 25 Metamerism segmentation Serial repetition of body parts Compartmentalized coelom Hydrostatic skeleton Digestive system Mollusca Characteristics Bilateral symmetry Cephalization and CNS True tissues Triploblastic Coelomate Complete digestive system, circulatory system, respiratory system Feed using radula (rasping organ) Body with three parts: foot, visceral mass, mantle H.A.M. (Hypothetical Ancestral Mollusc) Phylum Mollusca, Class Bivalva 2-part shells Clams, mussels, scallops and oysters Phylum Mollusca, Class Gastropoda Single spiral shell, or lacking shell Snails, slugs, nudibranchs Phylum Mollusca, Class Cephalopoda Muscular foot modified to form tentacles Highly intelligent predators Have a beak in addition to the radula Include squid and octopuses 35 3

4 Amazing Octopuses! Octopus opens jar: Bipedal Octopus: Octopus Camouflage Bonus Activity: 1. Name the two groups of Protostomes 2. What type of symmetry do Protostomes have? 3. Are Protostomes diploblastic or triploblastic? 4. What is a lophophore? Do all Lophotrochozoans have them? 5. Name four groups of Lophotrochozoans 6. How do Lophotrochozoans grow? Continuously, or by molting? 7. Now we will examine the Ecdysozoan lineage Shared trait: growth by molting Nematoda Characteristics Bilateral symmetry True tissues Triploblastic Psuedocoelomate Through-gut with mouth and anus, but no respiratory or circulatory structures Body covered with tough cuticle Molt to grow (hence ecdysozoa) Have longitudinal but no circular muscles Importance of Nematodes Ecologically diverse and extremely abundant Decomposers, scavengers, fungivores in detritus food webs of terrestrial systems Agricultural pest species Important parasites of plants and animals (including humans) 4

5 43 Important nematode parasites Ascaris lumbricoides human roundworm Trichinella spiralis - trichinosis Necator americanus - hookworm Dirofilaria immutis - heartworm Phylum Arthropoda - characteristics Coelomates Developmental metamorphosis Metamerism - compartmentalized coelom Tagmatization fusion of segments into 2 or 3 functional regions (head/thorax/abdomen or cephalothorax/abdomen) Exoskeleton with jointed appendages (paired) Open circulatory system (hemocoel) Respiratory system Well-developed sense organs and CNS Excretory system Tagmatization fusion of segments into functional regions Tagmatization Why are the arthropods so successful? Exoskeleton and Jointed Appendages Strength, armor plating (protection) Resistance to desiccation Function as levers (efficient locomotion); adaptable as tools Basic body design plasticity (tagmatization) Morphological modification exploit different niches Small size; Short life span Rapid change in genetic structure of populations Advantages of exoskeleton Strength armor plating Waterproof and nearly impermeable Prevents desiccation Enables terrestrial life When compartmentalized and/or jointed, functions to apply force Locomotion Use as tool Disadvantages of exoskeleton Weight of exoskeleton External seal 5

6 Respiration limits Must be shed in order to grow Vulnerability Phylum Arthropoda, Class Myriapoda Millipedes & Centipedes Long, segmented bodies with each segment bearing one or two pairs of appendages Millipedes detritivores; two pairs legs/segment Centipedes Carnivores with poison fangs; one pair of legs/segment Phylum Arthropoda, Class Chelicerata Ticks, spiders, mites, scorpions, horseshoe crabs, daddy longlegs Four pairs of walking legs Named for chelicerae structure near mouth Various functions, including feeding, movement, defense, and sensory perception Phylum Arthropoda, Class Crustacea Shrimp, lobster, crabs, isopods, copepods Cephalothorax (covered with carapace) and abdomen Phylum Arthropoda, Class Insecta ~1 million species identified; maybe as many as 10 million species! Many of these species are beetles (1/3 of all species on the planet!) Have a three-part body: head, thorax and abdomen Have 3-pairs walking legs May have other appendages for flight and/or feeding All for today Next time, Deuterostome Animals 6