Phylum Porifera – Characteristics Multi-cellular, but cells totipotent; evolutionary origin likely from colonial Protozoa (choanoflagellates); good fossil record from as early as Cambrian; asymmetrical, but many vase-shaped with excurrent hole (osculum) Cell Differentiation Choanocyte: “collar cell” with flagellum and microvilli Archaeocyte: amoeboid cell; can differentiate into sclerocytes (secrete spicules) and other cell types Pinacocyte: flattened, epithelial-like cell; form pinacoderm (epithelium) Body Structures (increasing efficiency of filtration) 1. Asconoid: choanocytes in central chamber (spongocoel) 2. Syconoid: choanocytes in canals leading to spongocoel 3. Leuconoid: choanocytes in multiple chambers

Newly Discovered Sponge Species: Bobospongia isrealensis

CO 12

Fig FIGURE 12.1, page 248

Fig. 12.9

Fig. 12.2

Fig. 12.5

Phylum Porifera – Diversity and Physiology Diversity: ~ 15,000 extant species, most marine Class Calcarea: spicules are calcium carbonate; small sponges (< 10 cm high); ex. Scypha, Leucosolenia Class Hexactinellida (Glass Sponges): six-rayed siliceous (SiO 2 ) spicules, often bound together in network ; ex. Euplectella Class Demospongiae: 95% of sponge species; siliceous spicules and/or spongin; ex. Spongia (bath sponges) Physiology Reproduction: asexually via external buds or gemmules, or sexually with sperm and oocytes (most sponges monoecious); most with planktonic larval stage (parenchymula) Feeding: most are suspension feeders; some in nutrient-poor waters are carnivorous; others contain photosynthetic endosymbionts Many harbor commensal organisms; few predators (ex. angelfishes)

Fig. 12.4

Fig. 12.3

Fig

Fig

Phylum Cnidaria – Characteristics Cell Types: cnidocytes (stinging cells) contain nematocysts (venom-injecting barbs); sensory and nerve cells; few with muscle tissue Body Forms: sessile, attached polyp, and free- swimming or planktonic medusa; both exhibit radial symmetry; polymorphism common in colonial hydroids (siphonophores, ex. Physalia) Life Cycles: zygote develops into planula larva, which settles on substratum and develops into polyp; polyp produces medusae in most taxa; some without medusa stage (ex. sea anemones)

Fig. 13.4

Fig. 13.6

Fig. 13.3

Fig. 13.7

Fig

Phylum Cnidaria – Diversity and Physiology Diversity Class Hydrozoa (hydroids; hydrocorals): most marine and colonial Class Scyphozoa (jellyfishes): most marine; adult is medusa Class Cubozoa (box jellyfishes): all marine; Chironex fleckeri deadly Class Staurozoa: stalked polyp with medusa-like appearance Class Anthozoa (corals, sea anemones, sea pens, sea pansies): all marine; no medusa stage Physiology Reproduction: asexual via budding or fission; medusae typically sexual; polyps of anthozoans reproduce either sexually or asexually Feeding: capture prey with tentacles (sting); gut with mouth only (four gastric pouches in jellyfishes); hermatypic (reef-building) corals obtain sugars from endosymbiotic dinoflagellates Coral Reefs: built by scleractinian corals; secretions of calcium carbonate based on relationship with mutualistic endosymbionts (zooxanthellae) Reef Evolution (Darwin): Fringing reefs  Barrier reefs  Atolls

Hydroids - Diversity

Class Staurozoa  Class Scyphozoa

Fig – Class Cubozoa

Class Anthozoa - Diversity

Class Anthozoa - Diversity of Corals

Fig. 13.2

Fig

Fig

Fig

RED CLONE YELLOW CLONE ORANGE CLONE

Fig

Fig

Fig

Phylum Ctenophora – Characteristics and Diversity Characteristics: bi-radial symmetry; eight rows of ctenes (combs of cilia); most capture prey with two tentacles armed with adhesive cells (colloblasts); iridescent and luminescent (used in transgenics) Diversity About 150 species; entirely marine (major component of gelatinous zooplankton) Common names: comb jellies, sea walnuts Examples: Pleurobrachia, Beroe (predator), Cestum Population explosions of Mnemiopsis leidyi have led to fishery declines; spread via ship ballast

Fig

Fig