Phylum Annelida

Ancestral Traits –Coelomate –Lophotrochozoan –Protostome –Closed circulatory system –Cephalization Derived Traits –Segmentation Metamerism Septa –Setae Bristles –Myelinated neurons ~ 40K species of annelids Spirobranchus giganteus Christmas tree worm

Annelid Taxomony Class Polychaeta (many bristles) –most numerous # species –marine Hermodice crunculata

Annelid Taxomony Class Polychaeta Class Oligochaeta (few bristles) –Freshwater, marine & terrestrial Lumbricus terrestris

Annelid Taxomony Class Polychaeta Class Oligochaeta Class Hirudinea –Fixed # segments (34) –Setae absent Hirudo medicinalis

Annelid Phylogeny

Annelid Body Plan Setae

Class Polychaeta Highly specialized head regions –Antennae –Sensory palps –Feeding appendages Paired extensions of body (parapodia) Often tube-dwelling –Burrow into substrate and secrete mucus/CO 3 materials Bispira bunnea sabellid worm

Polychaete Anatomy

Polychaete Anatomy (cross section)

Polychaeta Amphitrite

Polychaeta Lugworm (Arenicola sp)

Polychaeta

Clade Siboglinidae (Phylum Pogonophora) Ridgea sp Riftia pachyptila

Giant tube worms (Vestimentifera) Riftia pachyptila trophosome

Polychaete Reproduction Dioecious Trochophore larvae Some species develop specialized segments containing gametes –Epitokes –Segments are released and gametes burst out

Polychaete Asexual Reproduction Epitokes are essentially buds Clues to ancestral origin of segmentation –Segmentation may have been derived from incomplete budding processes

Class Oligochaeta

Oligochaete Anatomy

Seta: a.k.a. Bristles

Oligochaete Excretory System

Oligochaete Nervous System

Oligochaete Nerve Cord

Oligochaete Reproduction

Oligochaete Development For terrestrial oligochaetes, development is direct without any larval forms Some aquatic oligochaetes retain a trochophore-like larval stage

Common Terrestrial Oligocheates: Earthworms Octagonal-tail wormOctagonal-tail worm (Dendrobaena octaedra)Octagonal-tail wormOctagonal-tail worm Red marsh wormRed marsh worm (Lumbricus rubellus)Red marsh wormRed marsh worm Dew-worm or nightcrawlerDew-worm or nightcrawler (Lumbricus terrestris)Dew-worm or nightcrawlerDew-worm or nightcrawler Pink soil wormPink soil worm (Aporrectodea rosea)Pink soil wormPink soil worm Canadian wormCanadian worm (Aporrectodea tuberculata)Canadian wormCanadian worm Pasture wormPasture worm (Aporrectodea turgida)Pasture wormPasture worm Woodland white wormWoodland white worm (Octolasion tyrtaeum)Woodland white wormWoodland white worm Redworm (Eisenia fetida )

Quick and Easy Earthworm Morphology Guide Aporrectodea turgidaLumbricus rubellus Morphology Number & location of GTs and TPs, location & shape of clitellum Ecology Location of burrows

Aquatic Oligocheates

Class Hirudinea

Hirudo medicinalis

Phylum Sipuncula ~250 species Trochophore larvae

Sipunculan Internal Structures

Phylum Echiura ~140 species Closed circulatory system Trochophore larvae Echiurus sp

Phylum Echiura Bonellia viridis

Echiuran Anatomy

Oddities Sex determination & dimorphism in echiurans