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Biology 222Invertebrate Zoology II

Fall 2004Stephen M. Shuster

Northern Arizona University

Lecture 12

Annelid SystematicsThree primary groups

a. Class Polychaetab. Class Oligochaetac. Class Hirudinida

“The Older Version”

Annelid SystematicsThree primary groups

a. Class Polychaetab. Class Clitellata

1. Subclass Oligochaeta2. Subclass Hirudinoidea

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Subclass HirudinoideaThree Orders:a. Order

Acanthobdellida1. Small groups, but

apparently ancestral.2. Posterior sucker only.3. Occasional parasite

on freshwater fish.

Class HirudinoideaThree Orders:b. Order Branchiobdellida1. Small group, single family2. Ectoparasitic on crayfish3. Occasionally placed with

oligochaetes.

Class HirudinoideaThree

Orders:c. Order

Hirudinea1.Considered

the “true leeches.”

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Order Hirudinea2. Two subordersa. Rhynchobdellae -

with proboscisb. Arhynchobdellae -

without proboscis.

Hirudinoid Reproduction1. Male and female reproductive

anatomy2. Like oligochaetesa. Hermaphroditismb. Differential allocation of energy to

sperm, ova (S>>O).c. Sex Allocation.

Hirudinoid Reproduction1. Usually with copulation 2. or occasionally with hypodermic

insemination

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HirudinoidReproductiona. Rhynchobdellae1. male and female

copulatorystructures

HirudinoidReproduction

b. Arhynchobdellae1. reduced female

structures2. vector tissue

Vector Tissue 1. Receives sperm

after hypodermic insemination.

a. Responsible for transporting sperm (or spermatophore) to ovaries

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Parental Care 2. Many leeches provide parental care

to younga. Broods are guarded and fed by the

parent.b. Some species for creches.

Baby Leeches with Mom/Dad

I thought I saw a forest rat

Which hopped just out of reach

I looked again, and saw it was

A giant sucking leach.

If that should come to dine, I thought

'Twould drink us all and each

Leech Poetry

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I took a leach to bed with me,

I fed it all night through,

But when by light I chanced to see,

I squashed it with my shoe.

Brush off your leaches, start bleeding right now,

Brush off your leaches, and the women you will wow.

Leech Poetry

Annelid Evolution

1. Annelids appear to be derived from ancestors that may have occupiedfreshwater or brackish environments

Annelid Evolutiona. Similar to polychaetes - had setaeb. Probably didn't arise from full

polychaetes because it would require loss of parapodia.

c. However, polychaetes have trochophore larvae.

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TrochophoreLarvae

1. Possessed by several coelomateprotostomes.

TrochophoreLarvae

1. Phylum Annelidaa. Class Polychaeta

2. Phylum Echiura3. Phylum Sipuncula4. Phylum Mollusca

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Annelid Evolutiona. Similar to polychaetes - had setaeb. Probably didn't arise from full

polychaetes because it would require loss of parapodia.

c. Possess specialized structures associated with copulation.

2. Seem to be ancestral to other clitellate worms (leeches).

1. Unique annelid head2. Parapodia3. Elaboration of

polychaete head.

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4. Hermaphroditism5. Clitellum6. Direct development7. Cerebral ganglion shift8. Reproductive anatomy9. Fixed segment number

10. Fusion of coelomiccompartments

11. Posterior sucker12. Superficial annuli13. Loss of chetae

Coelomate Worms1. Four Major Phylaa. Phylum Echiurab. Phylum Sipunculac. Phylum Pogonophorad. Phylum Vestimentifera

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Coelomate Worms1. Four Major Phylaa. Phylum Echiurab. Phylum Sipunculac. Phylum Pogonophorad. Phylum Vestimentifera

Are actually Are actually PolychaetesPolychaetes!!

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“Higher Protostomes”

“Higher Protostomes”

SipunculaMolluscaEchiuraAnnelida

ArthropodaTardigrada

Onychophora

“Higher Protostomes”

SipunculaMolluscaEchiuraAnnelida

ArthropodaTardigrada

Onychophora

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“Higher Protostomes”

SipunculaMolluscaEchiuraAnnelida

ArthropodaTardigrada

Onychophora

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“Higher Protostomes”

SipunculaMolluscaEchiuraAnnelida

ArthropodaTardigrada

Onychophora

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