Invertebrate Diversity I
Porifera, Cnidaria, Ctenophora,
Platyhelminthes, Rotifera,
Nematoda
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:
• Eumetazoa:
– no symmetry
– all symmetrical
• radial or bilateral
– no true tissues or
organs
– almost all have
tissues
– 1 phylum: Porifera
– 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
spiral,
determinate
radial,
indeterminate
Coelom formation
schizocoelous
enterocoelous
Fate of blastopore
protostome
deuterostome
mouth
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)
2)
3)
4)
cell walls
multicellular
heterotrophic
tissues
Q2: Which of the following is NOT a basis
for traditional animal taxonomy
1)
2)
3)
4)
tissue specialization/number of germ layers
body symmetry
molecular similarities
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. Cnidaria
formerly 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)
Comb jelly
Retractable tentacles!
Ctenophore
Comb Jelly (“Sea gooseberry”)
Q3: Phylum Cnidaria is named for the
characteristic
1)
2)
3)
4)
bag-like structure
medusa and polyp life stages
two germ layers
stinging cells
Q4: True jellyfish belong to the class
1)
2)
3)
4)
Hydrozoa
Scyphozoa
Anthozoa
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)
&
(or, what do
politicians and
parasites have in
common?)
Political Cycle
of the
Blood Fluke
(Schistosoma
mansoni)
Class Cestoidea: tapeworms
Tapeworm
encysted in
muscle
Q5: Cestodes (tapeworms) differ from the
other flatworms in that they
1)
2)
3)
4)
lack digestive organs
lack a cephalized nervous system
have a segmented body plan
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 nematodes
Transfer via mosquitoes
Adults live in blood stream & large lymphatic vessels
Larvae infest peripheral lymphatic capillaries - crepuscular
Body’s reaction is overgrowth of connective tissue
Q6: Pseudocoelomate phyla include the
1)
2)
3)
4)
Protista and Porifera
Cnidaria and Ctenophora
Platyhelminthyes and Chordata
Rotifera and Nematoda
Q7: All of the eumetazoan invertebrates we
have discussed so far are
1)
2)
3)
4)
acoelomates
protostomes
segmented
secretly vertebrates