Invertebrate Diversity IInvertebrate Diversity I

Porifera, Cnidaria, Ctenophora, Porifera, Cnidaria, Ctenophora, Platyhelminthes, Rotifera, Platyhelminthes, Rotifera,

NematodaNematoda

Kingdom Animalia• Heterotrophic ingesters• Multicellular

– “higher” groups have tissues – tissues arranged into organs in some groups

• No cell walls – flexible• Nervous tissue & Muscle tissue• No alternation of generations• Common early embryological development

2 Sub-kingdoms in Animalia

• Parazoa:– no symmetry

– no true tissues or organs

– 1 phylum: Porifera

• Eumetazoa:

– all symmetrical• radial or bilateral

– almost all have tissues

– all other animal phyla (~35 phyla)

Bases for traditional invertebrate taxonomy

1 Tissue specialization– Aggregates– Diploblastic – 2 germ layers– Triploblastic – 3 germ layers

Choanoflagellate Colony (Protist)

Bases for traditional invertebrate taxonomy

2 Body symmetry

None Radial Bilateral

Bases for traditional invertebrate taxonomy

3 Body Cavity

Bases for traditional invertebrate taxonomy

4 Early embryology

Cleavage

Coelom formation

Fate of blastopore

radial, indeterminate

enterocoelous

deuterostome

spiral, determinate

schizocoelous

protostomemouth anus

Two alternative family trees

morphological, developmental

Biochemical, molecular

Vertebrates vs. Invertebrates

• Invertebrates– “animals without backbones”

– 35.001 modern animal phyla

– origin of all modern phyla in Cambrian Explosion (~540mya)

• Vertebrates– “animals with backbones”

– one diverse subphylum of Ph. Chordata

– staggered evolution of vertebrate classes

Q1: Which of the following is NOT a common feature of the eumetazoan animals

1) cell walls

2) multicellular

3) heterotrophic

4) tissues

Q2: Which of the following is NOT a basis for traditional animal taxonomy

1) tissue specialization/number of germ layers

2) body symmetry

3) molecular similarities

4) early embryology

Ph. Porifera: the sponges

Anatomy of a Sponge

Spicules

Classes of Poriferans

• Calcarea – small, calcium spicules• Demospongae – larger, silica spicules

– the includes the bath sponges and flower baskets

• Hexactinellidae – hexagonal spicule array

– the “glass sponges”

Some poriferans . . .

Ph. Cnidariaformerly Colenterata (bag animals)

• true tissues - diploblastic (2 layers)

• no organs

• radially symmetric

• gastrovascular cavity with single opening

• cnidocytes, nematocysts, and tentacles

• 2 main body forms: polyp & medusa

Polyp -sessile, asexual

Medusa - motile, sexual

Cnidocytes: stinging cells

Classes of Cnidarians:

• Cl. Hydrozoa: hydroids (dominant polyp stage)

• Cl. Scyphozoa: true jellyfish

(dominant medusa stage)

• Cl. Anthozoa: sea anemones, corals (no medusa stage)

Class Hydrozoa

• The polypoid body form dominates

• Hydra

• Portuguese man o’ war

Man o’ war

A colonial hydroid!

Cl Scyphozoa: jellyfish

Cl Anthozoa -- anemone

Class Anthozoa:

Coral

Coral Polyps

Ph. Ctenophora: comb jellies

• 8 rows of ciliary plates

• digestive tube – 2 openings

• colloblasts (adhesive structures on tentacles)

Retractable tentacles!

Comb jelly

Ctenophore

Comb Jelly (“Sea gooseberry”)

Q3: Phylum Cnidaria is named for the characteristic

1) bag-like structure

2) medusa and polyp life stages

3) two germ layers

4) stinging cells

Q4: True jellyfish belong to the class

1) Hydrozoa

2) Scyphozoa

3) Anthozoa

4) Ctenophora

Ph. Platyhelminthes: flatworms

• Bilaterally symmetric• 3 tissue layers; organs• no body cavity: are acoelomates• dorsoventrally flattened (thus the name . . . )• primitive cephalization (but not in Class

Cestoidea)• blind-ended gut (also not in Cl. Cestoidea)• hermaphroditic (mostly)

4 classes of flatworms:

• Cl .Turbellaria: free-living flatworms, e.g., Planaria

• Cls. Trematoda & Monogenea: flukes

• Cl. Cestoidea: tapeworms

Planaria

Class Trematoda: flukes(digenetic – intermediate and definitive hosts)

Life Cycle of the

Blood Fluke(Schistosoma)

Political Cycle of the

Blood Fluke(Schistosoma

mansoni)

&

(or, what do politicians and parasites have in common?)

Class Cestoidea: tapeworms

Tapeworm encysted in muscle

Q5: Cestodes (tapeworms) differ from the other flatworms in that they

1) lack digestive organs

2) lack a cephalized nervous system

3) have a segmented body plan

4) all of the above

Ph. Rotifera: the rotifers

• Pseudocoelomates

• Mostly freshwater, but also on moss, lichens

• very small! But have complete digestive tract

• have a “crown of cilia” that draws food in toward their jaws

Rotifers

Rotifer

Ph. Acanthocephala – spiny-headed worms:

• barbed proboscis

• rudimentary gut

• intestinal parasites

• genomics suggests they are giant, modified rotifers

Ph. Nematoda:

• Unsegmented roundworms• pseudocoelomates• hydrostatic skeleton• many are animal parasites, e.g.,

pinworms, hook worms, Trichinella, Ascaris

• many are plant parasites

Nematode

Trichinella

Filariasis (Elephantiasis)

Microfilarial nematodesTransfer via mosquitoes

Adults live in blood stream & large lymphatic vesselsLarvae infest peripheral lymphatic capillaries - crepuscular

Body’s reaction is overgrowth of connective tissue

Q6: Pseudocoelomate phyla include the

1) Protista and Porifera

2) Cnidaria and Ctenophora

3) Platyhelminthyes and Chordata

4) Rotifera and Nematoda

Q7: All of the eumetazoan invertebrates we have discussed so far are

1) acoelomates

2) protostomes

3) segmented

4) secretly vertebrates