phylum annelida. ancestral traits –coelomate –lophotrochozoan –protostome –closed...
TRANSCRIPT
Phylum Annelida
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 giganteusChristmas tree worm
Annelid Taxomony
• Class Polychaeta (many bristles)– most numerous # species– marine
Hermodice Hermodice crunculatacrunculata
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/CO3 materials
Bispira bunneasabellid worm
Polychaete Anatomy
Polychaete Anatomy (cross section)
Polychaeta
Amphitrite
Polychaeta
Lugworm (Arenicola sp)
Polychaeta
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
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)• Red marsh wormRed marsh worm (Lumbricus rubellus)• Dew-worm or nightcrawlerDew-worm or nightcrawler (Lumbricus terrestris) • Pink soil wormPink soil worm (Aporrectodea rosea)• Canadian wormCanadian worm (Aporrectodea tuberculata)• Pasture wormPasture worm (Aporrectodea turgida) • Woodland white wormWoodland 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
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