Phylum Annelida

PoriferaPoriferaPoriferaPorifera

CycliophoraCycliophoraCycliophoraCycliophora

CnidariaCnidariaCnidariaCnidariaCtenophoraCtenophoraCtenophoraCtenophora

SipunculaSipunculaSipunculaSipunculaMolluscaMolluscaMolluscaMolluscaAnnelidaAnnelidaAnnelidaAnnelida

OnychophoraOnychophoraOnychophoraOnychophoraTardigradaTardigradaTardigradaTardigrada

BryozoaBryozoaBryozoaBryozoa

PlatyhelminthesPlatyhelminthesPlatyhelminthesPlatyhelminthes

NemerteaNemerteaNemerteaNemertea

RotiferaRotiferaRotiferaRotifera

GnathostomulidaGnathostomulidaGnathostomulidaGnathostomulidaGastrotrichaGastrotrichaGastrotrichaGastrotricha

NematodaNematodaNematodaNematodaNematomorphaNematomorphaNematomorphaNematomorpha

PriapulidaPriapulidaPriapulidaPriapulidaKinorhynchaKinorhynchaKinorhynchaKinorhynchaLoriciferaLoriciferaLoriciferaLoricifera

PhoronidaPhoronidaPhoronidaPhoronidaBrachiopodaBrachiopodaBrachiopodaBrachiopoda

EchinodermataEchinodermataEchinodermataEchinodermata

ChordataChordataChordataChordataHemichordataHemichordataHemichordataHemichordata

ArthropodaArthropodaArthropodaArthropoda

Adapted from Lesser Known ProtostomeAdapted from Lesser Known ProtostomePhyla. SICB 2001. J.R. Garey. Phyla. SICB 2001. J.R. Garey.

Possess trochophore larvaePossess trochophore larvae

Mollusca and Annelida are closely allied phyla

Echinodermata

Ciliophora

Chordata

Mollusca

Platyhelminthes

Nematoda

PoriferaAnnelida

Other

Apicomplex

Sarcomastigophora

Arthropoda

Phylum Annelida: 12,500 spp: 3 classes = Class Polychaeta (8000 spp)Class Clitellata;

subclass Oligochaeta (3500 spp)subclass Hirudinea (630 spp)

Annelid characteristics

• Trochophore larvae• Closed circulatory system • True coelom• Annuli refer to segmented, metameric body plan

– Each segment has metanephridia, branches of nerves and blood vessels, chitinous setae / chaetae

– Segments partially divided by septa

→ efficient hydrostatic skeleton

→ Pre-adapted for regional specialization and tagmatization

Metamerism

Circular musc.

Longitudinal musc.

Septa provide regional control over hydrostatic skeleton

setae

From this pic, know: metameric repetition of body segments (septa, metanephridia, nerves, blood vessels), modest cephalization, limited regional specialization

Polychaeta

• Mostly marine

• Errant and sedentary spp

Possess parapodia:

acicula = chitinous rods for support

Capillaries for gas exchange

setae

SwimmingCrawlingBurrowing

Cephalization

Jaws Ocelli (photoreceptors)

Tentacles:MechanoreceptorsChemoreceptors

Tube worms: The sedentary polychaetes

Parapodia reduced (no acicula, vascularization)

Feathery appendages at anterior end for feeding, gas exchange

Giant tube worms

• Discovered in 1977• Ocean floor 8000 ft

deep• 4 ft tall • No mouth. Get food

from endosymbiotic bacteria that feed on sulphur released at deep sea vents

Polychaete reproductionSeparate sexes

1. Conventional sexual reproduction:• Sperm + egg released into water →

trochophore larva

2. Epitoky:– Epitokous individual forms an

epitoke bya. Transformation of posterior portionb. Asexual budding– Mature indiv = atoke– Gamete-bearing part = epitoke

capable of swimming about in search of mates (timed w lunar cycle)

atokeepitoke

Class Clitellata

• Possess cylindrical ring used in reproduction– Formation of a cocoon for the embryos

• Permanent gonads

• Two subclasses:

1. Oligochaeta

2. Hirudinea

Oligochaeta

• Mostly fossorial, some aquatic

• little cephalization

• No specialized organs for gas exchange

• Feed on detritus, organic debris

• Hermaphroditic– Sperm exchanged between two mating

individuals

Sperm exchange between mating earthworms:

• Sperm from testis stored in, and later released from, seminal vesicles• Sperm from other worm stored in seminal receptacles• After separation, sperm from other worm used to fertilize eggs from the ovary

• Eggs and sperm from other worm released into forming cocoon

• Many terrestrial forms can be parthenogenic

Hirudinea

• Occur in freshwater or moist terrestrial habitats• Highly streamlined• No special organs for gas exchange, sensory

except ocelli• Have 2 suckers for feeding, locomotion

– 3-toothed jaws

• Ectoparasitic, but many

are predaceous or scavenge

Leech reproduction

• Reproduction similar to oligochaetes (use of clitellum to form cocoons)

Class(?) Echiura: spoon worms

• Have trochophore larva but lack segments or any indication of metamerism as adults

• Briefly segmented period as embryos

• Molecular data links Echiura to Annelida

• Reproduction similar to polychaeta

-140 spp-Marine-Burrow in sand, mud