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Chapter 30 More Invertebrates More Invertebrates Outline The coelom Molluscs Bivalves Cephalopods Gastropods Annelids Arthropods Crustaceans Uniramians Chelicerates Echinoderms 2 More Invertebrates Advantages of Coelom Protostomes vs. deuterostomes Differentiated according to three major events in embryological development 1 Cleavage - Spiral cleavage in protostomes - Radial cleavage in deuterostomes 3 Protostomes Compared to Deuterostomes 4 More Invertebrates Advantages of Coelom 2 Fate of blastopore - Mouth appears near blastopore in protostomes - Anus appears near blastopore in deuterstomes 3 Coelom Formation - Schizocoelom forms in protostomes - Enterocoelom forms in deuterstomes 5 More Invertebrates 6 Mollusks Mollusks (phylum Mollusca) Have three-part body plan - Visceral Mass Contains internal organs - Mantle May secrete shell and/or contribute to development of gills or lungs - Foot Muscle capture adapted for locomotion, attachment, or food Body Plan of Mollusks 7 More Invertebrates Mollusks Mollusks (cont.) Nervous system consists of several ganglia connected by nerve cords Coelom is reduced, and largely limited to the region around the heart Heart pumps hemolymph through vessels into hemocoel 8 More Invertebrates Bivalves Clams, oysters, mussels, and scallops Shell of two hinged parts, closed by powerful muscles No head, no radula Circulatory system open Sexes are separate Ciliated gills hang down within mantle cavity on either side of visceral mass Beating of cilia causes water to enter cavity Filter Feeders – capture tiny food particles suspended in water 9 Bivalve Diversity 10 More Invertebrates Cephalopods Head Footed Force water out mantle cavity Tentacles and arms capture prey by adhesive secretions or suckers Beak used to tear prey apart Well-developed sense organs Closed circulatory system Spermatophore packets passed from males to females 11 Cephalopod Diversity 12 More Invertebrates 13 Gastropods, cont. Have elongated, flattened foot Well-developed head region Eyes and tentacles project from coiled shell Gills are found in mantle cavity in aquatic gastropods Mantle functions as lung in terrestrial gastropods Gastropod Diversity 14 More Invertebrates Annelids Phylum Annelida are Segmented partitions (septa) divide the welldeveloped, fluid-filled coelom, which acts as hydrostatic skeleton Specialized digestive tract Closed circulatory system Ventral solid nerve cord Most are marine Setae (bristles) help in movement 15 Polychaete Diversity 16 More Invertebrates Earthworms Do not have well-developed head or parapodia Setae protrude in pairs directly from surface of body Food drawn into mouth by action of muscular pharynx Digestion and absorption occur in long internal intestine - Typhlosole increases surface for absorption 17 Earthworm, Lumbricus terrestris 18 More Invertebrates Earthworms Segmentaion evidenced by: Body rings Coelom divided by septa Setae on most segments Gangli and lateral nerves in each segment Nephridia in most segments Branch blood vessels in each segment 19 More Invertebrates Earthworms Reproduction Hermaphroditic Two worms lie in parallel to each other facing in opposite directions - Fused midbody segment (clitellum) secretes mucus, protecting sperm from dessication 20 More Invertebrates 21 Leeches Usually found in fresh water Same body plan as other annelids No setae Two additional suckers - Some parasitic - Keep blood flowing and prevent clotting by means of hirudin, a powerful anticoagulant Medicinal Leeches, Hirudo medicinalis 22 More Invertebrates Arthropods Arthropods (phylum Arthropoda) have freely movable jointed appendages Very successful due to many characteristics Rigid, jointed exoskeleton - Must molt as they grow Segmented, but some segments are fused into regions - Head, thorax, abdomen Well-developed nervous system 23 Arthropod Skeleton and Eye 24 More Invertebrates Arthropods Variety of respiratory organs Occurrence of metamorphosis Three major arthropod subphyla Crustaceans - Crayfish Uniramians - Centipedes Chelicerates - Spiders 25 More Invertebrates 26 Crustaceans Decapods are the most familiar and numerous of crustaceans Shrimp, lobsters, crayfish, and crabs Thorax bears five pairs of walking legs Head and thorax fused into cephalothorax - Covered by nonsegmented carapace - Abdominal segments equipped with swimmerets Respiratory system consists of gills Crustacean Diversity 27 Male crayfish, Cambarus 28 More Invertebrates 29 Uniramians Include insects, millipedes, and centipedes Appendages attached to the thorax and abdomen only have one branch Head appendages include: Only one pair of antennae One pair of mandibles, and One or two pairs of maxillae Live on land and breathe by tracheae Insect Diversity 30 Two Types of Insect Mouthparts 31 Female Grasshopper, Romalea 32 Centipede and Millipede 33 More Invertebrates 34 Chelicerates Include terrestrial spiders, scorpions, ticks, mites, horseshoe crabs and sea spiders All appendages attached to cephalothorax; none on head First pair (chelicerae) are feeding organs Second pair (pedipalps) function in feeding or sensory Chelicerate Diversity 35 More Invertebrates 36 Echinoderms Sea stars, sea urchins, sea cucumbers, and sea lilies Radial symmetry as adults (not as larvae) Internal calcium-rich plates with spines Central nerve ring with branches Water vascular system for locomotion Echinoderms 37 More Invertebrates Review The coelom Mollusks Bivalves Cephalopods Gastropods Annelids Arthropods Crustaceans Uniramians Chelicerates Echinoderms 38 Ending Slide Chapter 30 More Invertebrates
