Phylum Annelida Phylum Annelida Terrestrial marine freshwater Repeating

Phylum Annelida

Phylum Annelida Terrestrial, marine, freshwater. Repeating segments. Triploblastic. True coelomates – complete gut. Closed circulatory system. Well developed nervous system. Respiratory organs. Protostome development. Metamerism (unspecialized) segmentation. One or more pairs of setae.

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

Systems • Integument epidermis is one cell layer with mucous gland that secrete a moist cuticle. • Skeletal -hydrostatic (using coelom) • Muscle longitudinal and circular muscles Each segments muscles are independent of the other segments. • Digestive complete, complex, with absorption and digestive glands and excretory cells.

Systems (continue) • Excretory a pair of nephridia per segment. • Respiratory -through skin, some through parapodia; tubeworms have gills. • Circulatory closed system, use hemoglobin as oxygen carrier. • Nervous dorsal brain; ventral, double, solid nerve cord, with ganglia in each segment. • Endocrine hormones secreted by nervous system. • Reproductive – Dioecious in Polychaeta; no special organs, posterior end becomes gonads. – Monoecious in Oligochaeta and Hirudinea; Clitellium.

Annelid Taxonomy • Phylum Annelida (an-nel-i-da) – Class Polychaeta (poly-key-ta) • Nereis, Aphrodita, Chaetopterus, Arenicola, Amphitrite – Class Clitellata – Subclass Oligochaeta (ol-e-go-key-ta) • Lumbricus, Tubifex – Subclass Hirudinea (hi-ru-din-e-a) • Hirudo, leech • Earthworm dissection

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

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

Annelid Taxomony • Class Polychaeta • Class Clitellata – Subclass Oligochaeta – Subclass 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 Bispira bunnea (parapodia) sabellid worm • Often tube-dwelling – Burrow into substrate and secrete mucus/CO 3 materials

Polychaete Anatomy

Polychaete Anatomy (cross section)

Polychaeta Amphitrite

Polychaeta Lugworm (Arenicola sp)

Polychaeta

Polychaeta

Clade Siboglinidae (Phylum Annelida? ) Riftia pachyptila Ridgea sp

Giant tube worms (Vestimentifera) trophosome Riftia pachyptila

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

Class Oligochaeta • Defining characteristics – Pronounced cylindrical glandular region of the body = clitellum • Second largest class in the phylum Annelida • Most spp. are earthworms, very few are marine 24 Phylum Annelida

Polychaetes and Oligochaetes • Oligochaetes differ from polychaetes in several ways: – No parapods, fewer setae (if at all) – Hermaphroditic with sex cells produced in a separate section – No larval stages 25 Phylum Annelida

Oligochaete Anatomy

Oligochaete Anatomy

Setae: a. k. a. Bristles

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 worm (Dendrobaena octaedra) Red marsh worm (Lumbricus rubellus) Dew-worm or nightcrawler (Lumbricus terrestris) Pink soil worm (Aporrectodea rosea) Canadian worm (Aporrectodea tuberculata) Pasture worm (Aporrectodea turgida) Woodland white worm (Octolasion tyrtaeum) Redworm (Eisenia fetida )

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

Earthworm Dissection Return to taxonomy Cross section

Aquatic Oligocheates

Subclass Hirudinea • Defining characteristics – Posterior sucker • Predominately freshwater, but do occur in all seas and moist soil • Leeches do not burrow or crawl, lack parapods and setae 35 Phylum Annelida

Subclass Hirudinea

Leech Anatomy • Anterior sucker is small and contains the mouth – Anterior sucker creates a wound with saw like jaws • Leeches drink other animals’ blood, usually vertebrates – Can be carnivores, or scavengers; leeches are not set in their feeding habits 37 Phylum Annelida

Hirudo medicinalis

Leech Reproduction • Leeches are simultaneous hermaphrodites that lack a free-living larvae stage • Fertilization is internal through copulation • Development occurs in a cocoon similar to the Oligochaetes 40 Phylum Annelida