CHAPTERs 12 & 13 PORIFERA, CNIDARIA AND CTENOPHORA

Phylum Porifera (pore-bearer) I. A. Characterisitics: Usually asymmetrical, sometimes radially symmetrical Contain no tissues, organs, or muscles Filter feeders: water moves in through the pores into the central body cavity and out through the osculum.

Phylum porifera supported by a skeletal system consisting of needle-like spicules composed of silicon salts (glass) or calcium carbonate (CaCO3), and/or a soft and pliable skeleton made of organic fibers composed of fibrous collagen or spongin.

Composition of Skeleton is used to classify porifera Contain three cell types: 1. pinacocytes: line the outer surface, may be mildly contractile

specialized for reproduction secreting skeletal elements 2. mesenchyme cells: amoeboid cells that move about in the mesohyl (middle cell layer) specialized for reproduction secreting skeletal elements transporting and storing food form contractile rings around openings (pores)

3. choanocytes: (collar cells) cells with flagella that create water currents and the collars the filter food out of the water (phagocytosis).

Maintenance Functions B. Digestion: the break down of food occurs inside food vacuoles/lysosomes (intracellular) Excretion: nitrogenous waste occurs by diffusion

Respiration: O2 and CO2 gas exchange occurs by diffusion Endocrine System: may use chemical messages for communication among cells

a. Sexual reproduction: Skeletal: spicules or spongin Reproduction *****(know in detail) a. Sexual reproduction: Sponges are monoecious (produce both sex cells in a single individual) but produce eggs and sperm at different times.

Zygote develops into a free-swimming larva that will settle to a substrate after 2 days.

b.Asexual reproduction: the formation of gemmules (resistant capsules that contain masses of amoeba- like mesenchyme cells) gemmules are formed when the sponge dies or is under environmentally stressful conditions.

gemmules are formed in the mesohyl

Asexual reproduction is also regeneration (an internal budding process producing identical clones of the parent).

3 Different types of anatomy C. Morphology of Sponges **** Body formation is based on the pathway of water currents flowing through the sponge

3 canal types: 1. Asconoid sponges: simplest body plan, water moves in ostia (pores)  spongocoel  out a single osculum 2. Syconoid sponges: water moves in ostia  incurrent canals  radial canals  spongocoel  out a single osculum

Leuconoid sponges: most complex with a branched canal system, water moves in ostia  incurrent canal  excurrent canals  smaller spongocoel  out multiple osculum

Cnidaria “Stinging celled” A. Characteristics: Radial or biradial symmetry Diploblastic (2 tissue layers), endoderm and ectoderm with gelatinous mesoglea in between Gastrovascular cavity (GVC) Nervous system: nerve net Have Cnidocytes which contain special organelles called nematocysts for attachment, feeding and defense, often contain toxins.

Maintenance Functions Digestion: begins in the gastrovascular cavity (GVC) and is completed in food vacuoles, undigested waste exits out the mouth (intracellular), no anus present Excretion: GVC also functions in the exchange of nitrogenous waste through diffusion Respiration: the exchange of gases (O2 & CO2) also functions through diffusion of the GVC

Reproduction: GVC functions to release the gametes (egg and sperm cells) Skeletal & locomotion: support and movement are aided by a hydrostatic skeleton (the GVC fills with water).

Exhibit alternation of generations Muscular: contraction of epitheliomuscular cells aid in movement. C. Reproduction *** Exhibit alternation of generations Each generation is a different body form  

2 different forms: polyp asexual and sessile cylindrical body with a mouth at the top surrounded by food-gathering tentacles reproduces by budding (the bud is the offspring of the polyp and becomes the next generation = medusa body plan

Medusa medusa dioecious (separate sexes), sexual, and free-swimming body shaped like an inverted bowl with the tentacles hanging down around the mouth underneath formed by budding from a polyp has sexual reproduction by releasing egg (female) and sperm (male) into the water

zygote develops into a planula larva (the offspring) Larva plants itself into the ground and will grow to become the next generation of polyp.

D. Classes Hydrozoa: ie) Obelia, Hydra, Portuguese man- of war (phasalia) 2. Scyphozoa: (true jellyfish) ie) Aurelia, Stinging nettle

4. Anthozoa: ie) sea anemones and stony and soft coral 3. Cubozoa: (medusa is cuboidal) ie) Sea wasp 4. Anthozoa: ie) sea anemones and stony and soft coral

Ctenophora III. Phylum Ctenophora A. Characteristics Biradial symmetry Diploblastic with gelantinous mesoglea Monoecious Gastrovascular cavity Nerve net

Adhesive structures called colloblasts that capture prey. Eight rows of ciliary band, called comb rows, for locomotion. Examples: Pleurobranchia, Boroe (Sea Fan and Sea Pin)