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: –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 1Tissue specialization –Aggregates –Diploblastic – 2 germ layers –Triploblastic – 3 germ layers Choanoflagellate Colony (Protist)

Bases for traditional invertebrate taxonomy 2Body 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 protostome mouthanus

Two alternative family trees morphological, developmental Biochemical, molecular

Vertebrates vs. Invertebrates Invertebrates –“animals without backbones” – 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. 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)

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 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)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