1. Phylum Annelida – Phylum and Class Characteristics
Lecture: Segmented Worms and Allies
Phylum Annelida – Phylum and Class Characteristics
Phylum Characteristics: coelomate body divided into segments (metameres) via septa; repeated arrangements of organs and structures within segments (excl. digestive system); setae (bristles) and hydrostatic skeleton (excl. leeches); closed circulatory system; paired, ventral nerve cords and cerebral ganglia; paired nephridia in each segment (excretion)
Diversity and Overview of Class Characteristics
Class Polychaeta: most marine (“sea worms”); parapodia (paddle-like appendages); well-developed sensory organs
Class Oligochaeta: most terrestrial (earthworms); secrete cocoon from clitellum (reproduction); hermaphroditic
Class Hirudinida: most aquatic (leeches); dorso-ventrally flattened body; suckers for attachment; suck blood/body fluids; clitellum forms only during reproductive season

2. Fig. 17.1

3. Lecture: Segmented Worms and Allies
Class Polychaeta
Diversity: approx. 10,000 species, many create burrows
Clam worms: most predatory with proboscis and chitinous jaws; include Nereis and Eunice spp. (ex. bobbit worm)
Scale worms: flat bodies covered with plates
Fireworms: toxins secreted through hollow setae
Lugworms: deposit feeders (ingest organics from sediment)
Tubeworms: sedentary; composition of tubes vary (ex., CaCO3, leathery, chitinous)
Featherduster worms: filter feed with extended radioles (fan); include Christmas-tree worms
Spaghetti worms: capture food particles with extended tentacles
Parchment worm (Chaetopterus): captures food with mucous net within tube; fan-like parapodia create water flow
Pogonophorans (beardworms): discovered around deep-sea vents; no digestive tract; symbiosis with chemosynthetic bacteria (located in trophosome); chitinous tubes

4. Class Polychaeta (“Sea Worms”)

5. The Bobbit Worm (Eunice sp.)

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13. Earthworms and Leeches
Lecture: Segmented Worms and Allies
Earthworms and Leeches
Class Oligochaeta: approx species; earthworms burrow  soil turnover and aeration; loss of parapodia and pronounced heads/sense organs
Setae extend from pores in body wall (muscular control)
Digestive system compartmentalized (incl. crop, gizzard)
Dorsal blood vessel pumps blood; aortic arches stabilize blood pressure; some with hemoglobin; gas exchange through moist skin
Class Hirudinea: fixed number of segments with superficial annuli; lack setae; possess anterior and posterior suckers for attachment to host
Medicinal leeches (Hirudo medicinalis): used to promote growth of capillaries and reduce congestion in veins; once used for bloodletting (fevers thought to result from excess of blood)

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24. Annelid/Arthropod Allied Phyla
Lecture: Segmented Worms and Allies
Annelid/Arthropod Allied Phyla
Phylum Echiura (spoon worms): approx. 140 species, all are marine burrowing worms, widespread deposit feeders; spoon- shaped proboscis; lack segmentation, but molecular evidence suggests derived from annelids
Phylum Sipuncula (peanut worms): all marine burrowing worms; eversible introvert at anterior end bearing tentacles
Phylum Onychophora (velvet worms): most are predators on insects in rain forests; so-called “living fossils” with little change in morphology since Cambrian Period; some with segmented bodies (ex. Peripatus); unsegmented, paired legs with claws; nephridia and ventral nerve cord
Phylum Tardigrada (water bears): minute (< 1mm) cylindrical bodies; live in film surrounding mosses or in damp soils; cuticle molted; buccal tube adapted for sucking; separate sexes; terrestrial forms can undergo cryptobiosis (state of suspended animation)

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29. My Squishy Friend the Tardigrade