PHYLUM CNIDARIA Flashcards
What are the three main classes of the Phylum Cnidarians?
Hydrozoa, Scyphozoa, Anthozoa
What are the two body forms that predominate in the phylum?
polyp (benthic)
Medusa (pelagic)
What are the key characteristics of the basic body plans of all cnidarians?
Radial Symmetry
The gut has one opening (mouth only, no anus)
Tentacles (hollow or solid) surround the end bearing the mouth
Gastrovascular cavity with associated canals
What are the functions of the tentacles?
Digestion
Distribution of nutrients
Cnidarians exhibit a true ______________.
Tissue level of organization
How are Cnidarians considered diploblastic?
Their body is composed of two tissue layers:
Epidermis (outer) and gastrodermis (inner) are true epithelial tissues
Describe the middle layer of the Cnidarians?
Mesoglea is mostly noncellular and not true tissue (simple basal lamina or massive and gelatinous)
Describe the cnidocyte cell.
Derived from the gastrodermal interstitial cells. And bears the nematocyst (capsule with inverted coiled tube & operculum) and cnidocil (sensory cilium)
What is the function of the nematocyst?
May aid in feeding (mainly), defense and agression and is used only once so the body has to regenerate
What is an ephithilio-muscular cell?
Epithelial cells with basal myofibrils and functions as the skin and muscle.
Differentiate the difference between the myofibrils found in the epidermis and gastrodermis.
Myofibrils are longitudinal in epidermis and circular in gastrodermis.
What are interstitial cells?
Totipotent cells which produce gametes and cnidocytes.
What are receptor cells?
Often have sensory cilium with no myofibrils
Describe the nerve cells found int he cnidarians.
Form a loosely organized note with no myofibrils
What are gland cells?
Gland cells are found mainly in the gastrodermis. They have no myofibrils.
What are amoeboid cells?
Mobile cells in mesoglea found in the epidermis of the Scyphozoa.
Describe the polyp phase of the Hydrozoa.
Cylindrical polyp form Simple mouth & pharynx No gastrovascular septae No gastric filaments with cnidocytes Solid tentacle form
Describe the medusa phase of the hydrozoans?
Has velum Simple bell margin Simple manubrium Unbranched gastrovascular canals No gastric filaments with cnidocytes Tentacles are used mainly for prey capture
Where are the hydrozoan gonads found?
Epidermal
The hydrozians are typically found in:
Mostly marine, some fresh water
Describe the polyp phase of the scyphozoans
Funnel-shaped polyp form Has simple mouth & pharynx Gastrovasculal septae are present Has gastric filaments with cnidocytes Has solid tentacle form
Describe the scyphozoan medusa phase.
No velum
Notched bell margin (rhopalia)
Has a comple manubrium (mouth lobes + cnidocytes)
Branched gasrtrovascular canals
Has gastric filaments with cnidocytes
Mouth lobes and tentacles are used for prey capture
Gonads are found gastrodermal
Where are scyphozoans typically found?
Gastrodermis
Describe the anthozoans polyp form.
Cylindrical polyp form Has tubular + siphonoglyph in the mouth and pharynx Has grovascular septae Has gastric filaments with cnidocytes Has hollow tentacles Gonads are found in the gastrodermal
