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Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8 Bilateria, Revisited Rotation at the Proto-Deutero Node

Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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Page 1: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

1

Biology 222Invertebrate Zoology II

Fall 2004Stephen M. Shuster

Northern Arizona University

Lecture 8

Bilateria, Revisited

Rotation at the Proto-Deutero Node

Page 2: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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BlastoporeFormation

a. This is an important part of earlier classification schemes

based on developmental characteristics.

b. Fate of blastopore differs among two major lines of

animals.1. Blastopore becomes mouth

- Protostomes2. Blastopore becomes anus -

Deuterostomes

Deuterostomes:

Lophophorates (?)

Chaetognatha

Echinodermata

Hemichordata

Chordata

Phylum Phoronida

Page 3: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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Phylum Brachiopoda

Phylum Ectoprocta (Bryozoa)

Phylum Chaetognatha1. Also known as “arrow worms” –small, highly voracious predators2. Will not be considered in great detail.

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Phylum Echinodermata

Hemichordates and Chordates

1. Highly specialized groups

with clear relationships to

each other

Hemichordates and Chordates

2. Synapomorphies:a. 22 – epithelia that binds to iodineb. 46 – pharyngeal gill slitsc. 52(4) – nervous system concentrated

dorsally

Page 5: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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Hemichordates and ChordatesClass EnteropneustaClass Pterobranchia

Subphylum UrochordataSubphylum

CephalochordataSubphylum Vertebrata

Hemichordates and ChordatesClass EnteropneustaClass Pterobranchia

Subphylum UrochordataSubphylum

CephalochordataSubphylum Vertebrata

Phylum Hemichordata1. Marine filter feeders2. Synapomorphiesa. 15 – preoral gut diverticulum that

supports anterior body - stomochordb. 51 –glomerulus as excretory organ.3. Classesa. Enteropneustab. Pterobranchia

Page 6: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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Phylum Hemichordata

Hemichordates and ChordatesClass EnteropneustaClass Pterobranchia

Subphylum UrochordataSubphylum

CephalochordataSubphylum Vertebrata

Phylum Chordata1. Ancestrally marine, sessile filter

feeders with motile larvae2. Synapomorphies:a. 39(1) – tripartite body cavity (again)b. 47 – notochordc. 48 – endostyle (becomes thyroid

gland in vertebrates)d. 63 – muscular, locomotory tail (in

larvae in urochordates)

Page 7: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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Phylum Chordata1. Representative Subphyla:

a. Urochordata – sea squirts and other ascidians

b. Cephalochordata - lanceletsc. Vertebrata – vertebrates

Hemichordates and ChordatesClass EnteropneustaClass Pterobranchia

Subphylum UrochordataSubphylum

CephalochordataSubphylum Vertebrata

Hemichordates and ChordatesClass EnteropneustaClass Pterobranchia

Subphylum UrochordataSubphylum

CephalochordataSubphylum Vertebrata

Page 8: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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Phylum Chordata1. Synapomorphies separating

Urochordates from Cephalochordates and Vertebrates:

a. 21 – myotomes – blocks of muscles arranges in segments.

b. 37 – longitudinal musculature derived from segmental enterocoelicpouching.

c. 94(6) – dorsal hollow nerve chord.

Subhylum Urochordata

Subphylum Cephalochordata

Page 9: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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νν

Subphylum VertebrataSubphylum Vertebrata

Protostomia

Protostomia1. Synapomorphiesa. 18(0) – Cleavage pattern spiral.b. 52(3) – Ventral or ventrolateral

synaptic nervous system.c. 74(1) – Entomesoderm derived from a

single mesentoblast (4d) cell.d. 75(1) – Subepidermal muscle in

sheets, derived (at least in part) from 4d cell.

Page 10: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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Protostomia1. Synapomorphies:a. 18(0) – Cleavage

pattern spiral.

CleavageCleavage1. After fertilization zygote must go from unicellular to

multicellular state.

2. Divisions are called cleavage because,

a. Cell size is reduced -reduction division.

b. No growth between cell divisions.

Blastomeresd. blastomeres vary in size

depending on type of cleavage and amount

of yolk present in ovum.

Page 11: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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BlastomeresBlastomeresvary in size

depending on type of

cleavage and amountof yolk

present in ovum.

Directions of Cleavage Planes and Blastomere

Fate

Two types of cleavage:

RadialSpiral

Directions of Cleavage Planes and Blastomere

Fate

Two types of cleavage:

RadialSpiral

Page 12: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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Directions of Cleavage planes and Blastomere

Fate

a. Radial Cleavage

1. Cell divisions occur along latitudinal or longitudinal

axes.

Radial Cleavage

3. Developmental fate of cells is indeterminate.

a. Cells can be separated and develop into

complete organisms.

b. Vertebrate zygotes are like this.

Spiral Cleavage1. Cell divisions are

longitudinal for first two divisions.

2. Then mitotic axes are transverse.

a. this causes blastomeres to appear to rotate.

b. usually dextropic; then levotropic; alternates to 64

cells.

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Spiral Cleavage

3. Developmental fate of cells is determinate.

4. After cleavage, you get a ball of cells.

Protostomia• Synapomorphies:• b. 52(3) – Ventral or

ventrolateral synaptic nervous system.

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Protostomia1. Synapomorphies:c. 74(1) – Entomesoderm derived from a single

mesentoblast (4d) cell.

Mesoderm and Coelom Formation

1. Mesoderm is derived from different sources in different

taxa.

2. An important aspect of development.

a. Third germ layer -represents an advance in structural organization.

MesodermSource of this layer is

associated with type and complexity of

coelom- the internal body cavity.

Page 15: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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Coelom

1. Involved in structural support.

2. Provides space for organs, movement,

gametes.c. Patterns of formation are

important in tracing phylogenies.

Sources of Mesoderm

3. In general, mesoderm sources

are:a. Protostomes: from

mesentoblast -endodermal cells near

anus.b. Deterostomes:

form enteric pouches.

Coelom FormationProtostomes

1. Mesoderm arises from vegetal cell (4d).

2. Arises near future anus.3. Forms two masses that later delaminate to form

coelom.a. Mesoderm spreads out to

form musculature and mesenteries.

Page 16: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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CoelomFormation

5. Mesodermal splitting to form coelom is called schizocoely.

Coelom FormationDeuterostomes

1. Mesoderm from enterocoelic pouches.2. Secondary schizocoely may occur.

3. Process proceeds the same as before.4. Mesodermal formation from pouches is enterocoely.

Page 17: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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Coelom Formation

Note: we now have some additional

characteristics that can be used

to classify Protostomes and Deuterostomes.

Protostomesa. Usually spiral,

determinate cleavage.b. Name from "first mouth"; blastopore

becomes mouth.c. Coelom formation by

schizocoely.d. Represent a major evolutionary lineage.

1. Some exceptions are now known; e.g. Lophophorates.

Deuterostomesa. Usually with radial, indeterminate cleavageb. Name from "second

mouth" blastoporebecomes anus, mouth

forms later.c. coelom formation by

enterocoelyd. also represent a major

evolutionary lineage1. again with some

exceptions.

Page 18: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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Protostomia1. Synapomorphies:75(1) – Subepidermal

muscle in sheets, derived (at least in part) from 4d cell.

Protostomia

Phylum Platyhelminthes

Page 19: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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Coelomate Protostomia

Coelomate Protostomia1. Synapomorphiesa. 77(1) – Schizocoelous coelom with body

cavity lined with mesodermally derived epithelium (peritoneum).

b. 95 – With trochophore larvae.

“Blastocoelomates”

Page 20: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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Blastocoelomates1. Gnathostomulida2. Entoprocta3. Cycliophora4. Rotifera5. Acanthocephala

6. Cycloneuraliaa. Gasterotrichab. Nematac. Nematomorphad. Priapulae. Kinorhynchaf. Loricifera

Phylum Nemertea

“Higher Protostomes”

Page 21: Biology 222 - jan.ucc.nau.edujan.ucc.nau.edu/~bio222-c/LecturePDFs/Lec08.pdf1 Biology 222 Invertebrate Zoology II Fall 2004 Stephen M. Shuster Northern Arizona University Lecture 8

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“Higher Protostomes”

SipunculaMolluscaEchiuraAnnelida

ArthropodaTardigrada

Onychophora