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Notes:  This is an outline of my class notes - details and visuals will be given in class!

Read: Chapter 12 in Hickman, Roberts & Larson.

1. Phylum Mesozoa
1. Gr. mesos - middle + zoon, animal
2. mes-o-zo'a
3. Figures 12-1 to 12-2 pp. 242-243
4. 50 species.
5. No symmetry
6. No body cavity
7. to 7mm long, 20 to 30 cells
8. No organs
9. Extracellular digestion
10. Simple excretion
11. Simple respiration by diffusion
12. No skeleton
13. Reproduction can be sexual or asexual
14. Parasitic on marine invertebrates
15. Parasitic in a variety of marine invertebrates, including cephalopods, brittle stars, bivalves, polychaetes, and nemerteans
16. Endoparasitic feeding
17. Mesozoans may have arisen from ciliated protozoa, or may have evolved from Platyhelminthes
18. Are mesozoans degenerate flatworms or primitive multicellular organisms?
19. Classes
1. Rhombozoa
1. Figure 12-1 p. 242
2. Gr. rhombos, a spinning top + zoon, animal
3. rom-bo-zo'-a
4. Parasitic on benthic cephalopods
2. Orthonectids
1. Figure 12-2 p. 243
2. Gr. orthos, straight + nektos, swimming
3. or-tho-neck'-ti-da
4. Parasitic on flatworms, brittle stars, bivalves, polychaetes, nemerteans

Some authorities think the two classes belong in separate phyla.

2. Phylum Placozoa
1. Gr. plax, plakos, tablet or plate, + zoon, animal
2. plack'-o-zo-a
3. Figure 12-3 p. 243
4. 1 species, described in 1971.
5. No symmetry
6. No body cavity
7. to 3 mm long
8. No organs
9. Extracellular digestion
10. Simple excretion
11. Simple respiration by diffusion
12. No skeleton
13. Reproduction asexual, fission and budding
14. no larvae
15. Marine, benthic - 1 known species, Trichoplax adhaerens
16. Detritivore, glides over food and secretes digestive enzymes
17. Related to Cnidaria (based on molecular evidence)?
3. Phylum Porifera - Sponges
1. plax, porus, pore, + fera, bearing
2. po-rif'-er-a
3. Figures 12-4 - 12-14 pp. 244-251
4. 5000 species.
5. Radial or no symmetry
6. Spongocoel and extensive canal systems
7. mm to 2 m across
8. No organs
9. Intracellular digestion
10. Simple excretion by diffusion
11. Simple respiration by diffusion
12. Skeleton of spicules and collagen
13. Asexual reproduction by budding and fragmentation. Monoecious sexual reproduction.
14. Parenchymula larvae
15. Marine, freshwater: benthic
16. Sessile, growing attached to the substrate
17. Filter feeders, water current created by choanocytes
18. Pores in the sponge are known as ostia.
19. The large central opening is the osculum.
20. The three growth forms are asconoid, syconoid, and leuconoid. Spicules may be siliceous or calcareous.
21. Spongin is an elastic form of collagen.
22. classes:
1. Class Calcarea
1. calcis, lime
2. cal-ca'-re-a
3. Figure 12-6, p 246
4. To 10 cm in height
5. Marine: benthic
6. Spicules made of calcium carbonate
2. Class Hexactinellida - glass sponges
1. Gr. hex, six + aktis, ray + L. ellus, diminutive suffix
2. hex-ak-tin-el'-i-da
3. 1 cm to 1.3 m in length
4. Skeleton of calcareous spicules and collagen
5. Asexual reproduction by budding and fragmentation.
6. Marine: benthic, deep-water
7. The glass sponges are deep-water marine forms. Venus' flower basket is in this class.
3. Class Demospongiae
1. Gr. demos, people + spongos, sponge
2. de-mo-spun'-je-e
3. Fig. 12-8 p. 247; 12-12 p. 249; 12-13 p. 250; 12-14 p. 250.
4. species.
5. Radial or no symmetry, leuconoid
6. To 2 m across
7. Skeleton of siliceous spicules and collagen
8. Marine, freshwater: benthic
9. This class includes 95% of the sponge species, the bath sponges, and all of the 150 freshwater sponges.
4. Class Sclerospongiae
1. Gr. skleros, hard + spongos, sponge
2. skler'-o-spun'-je-e
3. Radial or no symmetry, leuconoid
4. Form huge structures; only a thin "skin" of living tissue
5. Skeleton of calcareous spicules and collagen
6. Sessile, growing attached to the substrate, often in dark areas under coral reefs.
7. This class is a major constituent of coral reefs.

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09/04/00

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