Choanoflagellates Fungi Choanoflagellates ANIMALIA Porifera (sponges) ANIMALIA Multicellularity Ctenophora (comb jellies) Diploblasty Cnidaria (jellyfish, corals, sea anemones) Acoela (acoels) Triploblasty Protostome development LOPHOTROCHOZOA Rotifera (rotifers) Loss of coelom Platyhelminthes (flatworms) Segmentation Annelida (segmented worms) Mollusca (snails, clams, squid) ECDYSOZOA Nematoda (roundworms) PROTOSTOMES BILATERIA Cephalization, CNS, coelom Segmentation Arthropoda (insects, spiders, crustaceans) Deuterostome development DEUTEROSTOMES Radial symmetry Echinodermata (in adults) (sea stars, sand dollars) Segmentation Chordata (vertebrates, tunicates) DEUTEROSTOMES
A ctenophore, or comb jelly Phylum Ctenophora
Ctenophore
Cnidarians: Hydrozoans (top left), jelly (top right), sea anemone (bottom left), coral polyps (bottom right)
General Cnidarian characteristics Radially Symmetric Diploblastic (epidermis, gastrodermis) No cephalization, No central nervous system No special respiratory, excretory or circulatory organs Primarily Carnivores Polyp and Medusa body forms
Polyp and medusa forms of cnidarians sessile pelagic
Have no separate gut, (just GV cavity/body wall) and only one body opening. This has several consequences: Food and undigested waste pass through same opening in different directions Movements of body cause distortion of GV cavity GV cavity serves for both circulation and digestion Gametes and embryos must be released through the same opening
The Hydrostatic Skeleton Uses fluid (water) in a body compartment for support and transmission of muscular forces Fluid is incompressible, force generated by displacement of fluid in one region, can be used to do work in another
Figure 5.2 11
Figure 5.3 12
Figure 6.23 14
Epithelio-muscular cells (longitudinal) Nutritive-muscle cells (circular) 15
Many Cnidarians have endosymbiotic dinoflagellates (zooxanthellae) within their cells very important mutualism! Sea anemone
Coral polyps with endosymbiotic zooxanthellae (algae)
Endosymbiotic dinoflagellates (zooxanthellae) inside jellyfish cells
Hydra with endosymbiotic green algae
Almost all Cnidarians have cells called Cnidocytes which have organelles called nematocysts.
A cnidocyte of a hydra
22
Some Nematocyst types
Hydra capturing Daphnid Ingestion and Digestion
Cnidarian Nerve Nets
Mostly non-polar synapses, so impulses can travel in either direction Signal diminishes with distance 26
Nerve cells in epithelial tissue of Velella
28
Phylum Cnidaria Subphylum Medusozoa Class Scyphozoa Class Cubozoa Class Hydrozoa Subphylum Anthozoa (used to be Class) Subclass Hexacorallia Subclass Octocorallia
Class Scyphozoa Jelly medusa
Purple striped jelly, Pelagia panopyra
Gastric filaments on the gonads secrete enzymes and then phagocytize partially digested food. Digestion occurs intracellularly within food vacuoles.
Scyphozoan Rhompalia
Figure 6.9 Senses light Balance organ 35
Class Scyphozoa Most Scyphozoans are Dioecious Aurelia life cycle Strobila
Class Cubozoa Highly Toxic Nematocysts
Class Hydrozoa
Hydromedusae velum Scyphozoan medusae
Hydra: an atypical Hydrozoan
Thecate hydroid Athecate hydroid
Class Hydrozoa Obelia colony ephyra
Colonial Hydroid
Figure 33.7 The life cycle of the hydrozoan Obelia (Layer 1)
Figure 33.7 The life cycle of the hydrozoan Obelia (Layer 2)
Figure 33.7 The life cycle of the hydrozoan Obelia (Layer 3)
Physalia, Portugese man-of-war Order Siphonophora
Subphylum (class) Anthozoa Coral polyps Sea anemones
Anthozoan polyps are larger and more complex than Hydrozoan polyps No Medusa stage
Pharynx with siphonoglyphs GV cavity has mesenteries Cross section
A variety of Anthozoans
Subclass Octocorallia Have 8 pinnate tentacles Some are called Gorgonians (sea fans, sea whips)
Subclass Octocorallia Sea Fan, a gorgonian Sea Pens, a soft coral
Coral Polyps are often retracted in the daylight Renilla, the sea pansy
Subclass Hexacorallia Many tentacles, in multiples of 6 Scleractinian corals may build reefs
Secrete CaCO 3 at the base
Subclass Hexacorallia Anemone Shrimp Papua New Guinea