Mader: Biology 8 th Ed. The Protostomes Chapter 30

Mader: Biology 8 th Ed. Outline Molluscs – Bivalves Cephalopods Gastropods Annelids Arthropods – Crustaceans – Uniramians – Chelicerates

Mader: Biology 8 th Ed. Advantages of Coelom Protostomes and deuterostomes are differentiated according to three major events in embryological development. – Cleavage  Spiral cleavage in protostomes.  Radial cleavage in deuterostomes.

Mader: Biology 8 th Ed. Advantages of Coelom – Fate of blastopore  Mouth appears near blastopore in protostomes.  Anus appears near blastopore in deuterstomes. – Coelom Formation  Schizocoelom forms in protostomes.  Enterocoelom forms in deuterstomes.

Mader: Biology 8 th Ed. Molluscs Molluscs (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.

Mader: Biology 8 th Ed. Molluscs – 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.

Mader: Biology 8 th Ed. Body Plan of Molluscs

Mader: Biology 8 th Ed. Bivalves Possess two-part shell that is hinged and closed by powerful muscles. Have no head, radula, and very little cephalization. Within mantle cavity, ciliated gills hang down on either side of visceral mass. – Beating of cilia causes water to enter cavity.  Filter Feeders

Mader: Biology 8 th Ed. Bivalves Open circulatory system Sexes are separate Clams, oysters, mussels, and scallops

Mader: Biology 8 th Ed. Bivalve Diversity

Mader: Biology 8 th Ed. 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

Mader: Biology 8 th Ed. Cephalopod Diversity

Mader: Biology 8 th Ed. Gastropods 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.

Mader: Biology 8 th Ed. Gastropod Diversity

Mader: Biology 8 th Ed. Annelids 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

Mader: Biology 8 th Ed. Polychaete Diversity

Mader: Biology 8 th Ed. 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.

Mader: Biology 8 th Ed. Earthworms

Mader: Biology 8 th Ed. 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

Mader: Biology 8 th Ed. Earthworms Reproduction – Hermaphroditic – Two worms lie in parallel to each other facing in opposite directions.  Fused midbody segment (clitellum) secretes mucus, protecting sperm from drying out as they pass between worms.

Mader: Biology 8 th Ed. Earthworm Reproduction

Mader: Biology 8 th Ed. Leeches Usually found in fresh water. Same body plan as other annelids. – No setae – Two additional suckers.  Keep blood flowing and prevent clotting by means of hirudin, a powerful anticoagulant.

Mader: Biology 8 th Ed. 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.

Mader: Biology 8 th Ed. Arthropods – Variety of respiratory organs. – Occurrence of metamorphosis. Three major arthropod subphyla – Crustaceans  Crayfish – Uniramians  Centipedes – Chelicerates  Spiders

Mader: Biology 8 th Ed. 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.

Mader: Biology 8 th Ed. Crustaceans

Mader: Biology 8 th Ed. Crustaceans

Mader: Biology 8 th Ed. 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.

Mader: Biology 8 th Ed. Female Grasshopper

Mader: Biology 8 th Ed. Female Grasshopper

Mader: Biology 8 th Ed. Centipede and Millipede

Mader: Biology 8 th Ed. Chelicerates Include terrestrial spiders, scorpions, ticks, mites, horseshoe crabs and sea spiders. – First pair of appendages (chelicerae) are feeding organs. – Second pair of appendages (pedipalps) function in feeding or sensory.  All appendages attached to cephalothorax. – No appendages on heads.

Mader: Biology 8 th Ed. Chelicerate Diversity

Mader: Biology 8 th Ed. Review Molluscs – Bivalves Cephalopods Gastropods Annelids Arthropods – Crustaceans – Uniramians – Chelicerates

Mader: Biology 8 th Ed.