Biology, 9th ed, Sylvia Mader Chapter 30 Chapter 30 More Invertebrates More Invertebrates

Outline The coelom Molluscs Annelids Arthropods Echinoderms Bivalves Cephalopods Gastropods Annelids Arthropods Crustaceans Uniramians Chelicerates Echinoderms

Protostomes vs. deuterostomes 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

Protostomes Compared to Deuterostomes

Advantages of Coelom 2 Fate of blastopore 3 Coelom Formation Mouth appears near blastopore in protostomes Anus appears near blastopore in deuterstomes 3 Coelom Formation Schizocoelom forms in protostomes Enterocoelom forms in deuterstomes

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 adapted for locomotion, attachment, or food capture

Body Plan of Mollusks

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

Clams, oysters, mussels, and scallops 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

Bivalve Diversity

Tentacles and arms capture prey by adhesive secretions or suckers 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

Cephalopod Diversity

Have elongated, flattened foot Well-developed head region 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

Annelids Phylum Annelida are Segmented partitions (septa) divide the well- developed, 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

Polychaete Diversity

Do not have well-developed head or parapodia 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

Earthworm, Lumbricus terrestris

Segmentaion evidenced by: 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

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

Usually found in fresh water Same body plan as other annelids 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

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

Arthropod Skeleton and Eye

Three major arthropod subphyla Variety of respiratory organs Occurrence of metamorphosis Three major arthropod subphyla Crustaceans Crayfish Uniramians Centipedes Chelicerates Spiders

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

Male crayfish, Cambarus

Include insects, millipedes, and centipedes 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

Two Types of Insect Mouthparts

Female Grasshopper, Romalea

Centipede and Millipede

All appendages attached to cephalothorax; none on head 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

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

Review The coelom Mollusks Annelids Arthropods Echinoderms Bivalves Cephalopods Gastropods Annelids Arthropods Crustaceans Uniramians Chelicerates Echinoderms

Biology, 9th ed, Sylvia Mader Chapter 30 Ending Slide Chapter 30 More Invertebrates More Invertebrates