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. 12.1
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 (SiO2)
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. 12.11
Fig. 12.12
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 freeswimming 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. 13.12
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. 13.21 – Class Cubozoa
Class Anthozoa - Diversity
Class
Anthozoa Diversity
of Corals
Fig. 13.2
Fig. 13.11
Fig. 13.19
Fig. 13.24
RED CLONE
YELLOW CLONE
ORANGE CLONE
Fig. 13.28
Fig. 13.32
Fig. 13.35
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. 13.37
Fig. 13.39