BSC 201L (15e, rev)
Lab #2: Radiate Animals
Use the text and figures in Exercise 8 (The Radiate Animals) to aid your study of the prepared
slides and preserved specimens; examine the additional specimens as indicated.
Things to know for Phylum Cnidaria:
Polyp or medusa? (or both?)
Solitary or colonial?
Marine water (MW) or fresh water (FW)?
Structures and their functions
Phylum Cnidaria - 5 classes; we will look at 3
Class Hydrozoa, hydroids and hydromedusae
– both polyp and medusa (dimorphism) typically present and of similar size (small)
– medusae have a velum
– solitary or colonial
– most are MW species; but all FW cnidarian species are in this class
Hydra – text pp. 120-123
– FW
– solitary polyp only (no medusa stage)
– – rings of cnidocytes on tentacles
1. Budding slide – Fig. 8-2
– a type of asexual reproduction
– LABELS: tentacles, mouth, and bud
2. Slide (x.s.)
– LABELS: epidermis and gastrodermis
Obelia – text pp. 123-124
– MW
– colonial polyps and solitary medusae
3. Polyps slide – Fig. 8-3
4. Medusa slide – Fig. 8-3
Gonionemus – text pp.124-126
– MW
– solitary medusoid form only (no attached polyp stage)
5. hydromedusa – Fig. 8-4
– LABEL: velum (tentacles have been removed on the specimen, to better see it)
– one of the largest hydromedusae
Physalia, Portuguese Man-of-War
– MW
– colonial polyps with attached medusae
– pneumatophore: float/air bladder (modified zooid)
6. Preserved polymorphic colony
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Class Scyphozoa, true jellyfish
– medusa dominates (large); no velum
– polyp reduced or absent (small); often long lived
– all solitary
– all MW
Aurelia aurita, moon jelly – text pp. 126-129
7. Preserved adult medusa – Figs. 8-5, 8-6
– LABELS: oral arms, mouth, gonads (pink circles surrounding the four gut pouches),
tentacles, rhopalium (contains a statocyst for equilibrium and an ocellus, which is
photosensitive)
8. Planula slide – Fig. 8-6 – free swimming larva
9. Scyphistoma slide – Fig. 8-6 – polyp stage, can bud laterally to form additional
polyps
10. Strobila slide – Fig. 8-6 – polyp buds distally to form ephyrae
11. Ephyra slide – Fig. 8-6 – young, small medusa
Stomolophus, cabbagehead or cannonball jellyfish
12. Preserved adult medusa – solitary
Class Anthozoa, anemones, stony corals, soft corals
– all with polyp stage only; no medusa stage (not dimorphic)
– solitary or colonial
– all MW
Subclass Zoantharia (=Subclass Hexacorallia), anemones, stony corals
Metridium, sea anemone – text pp. 129-131
– solitary polyp
13. Preserved, external view – Fig. 8-7
– LABELS: oral disc, tentacles, mouth, column, basal disc
14. Preserved, internal view – Fig. 8-7
– LABELS: mouth, pharynx, gastrovascular cavity
Astrangia – text p. 131
– colonial (but not reef building coral) – temperate waters
15. Preserved specimen (skeleton only) – Fig. 8-8A
16. Various stony coral skeletons – (cf. Fig. 8-8B) – draw any 2 specimens (identified by
tags)
– thin layer of colonial polyps cover the relatively massive endoskeleton
– the holes are where the polyps were attached when the coral was alive
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Subclass Alcyonaria (=Subclass Octocorallia), soft corals, sea whips, gorgonians
– all colonial
17. Preserved sea whips
– colonial polyps surround a central axial skeleton
18. Dried sea fan
Observation: Examine the Cnidarian (“Coelenterates”) Biosmount. (Not necessary to draw.)
Phylum Ctenophora, comb jellies
– comb plates and comb rows – used in locomotion
– typically with 1 pair of tentacles bearing colloblasts; tentacles may be absent – never
dimorphic
– all solitary
– all MW
Pleurobrachia, sea gooseberry
– tentacles either retracted or broken off
19. Preserved specimen
– LABELS: comb plates, comb rows
Beroë ovata, thimble jelly
– carnivorous, lacks tentacles
20. Preserved specimen
– LABELS: comb plates, comb rows
DIFFERENCES / SIMILARITIES between Phylum Cnidaria and Phylum Ctenophora
Phylum Cnidaria
– dimorphism (polyp & medusa body forms)
– from 4 to many tentacles
– nematocysts (cnidae) are stinging organelles in special cells (the cnidocytes) on the
tentacles for prey capture and for defense
– muscle cells used for swimming
Phylum Ctenophora
– NO dimorphism (only one body form)
– usually 1 pair of tentacles; absent in some species
– colloblasts (adhesive cells) on the tentacles for feeding
– comb plates arranged in 8 rows for swimming
*****
FOR NEXT LAB MEETING:
– download handout for Lab #3 and read Exercise 9 (Flatworms).
– write out each taxonomic summary in your Laboratory Specimen Notebook BEFORE lab
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