Cnidaria, Questions

What are Alcyonaria?

=Octocorals = soft corals and their relatives (only 8 tentacles, branched & feathery; skeleton is internal spicules, tubes, or rods in mesoglea (if present)

What is a polyp?

Benthic cnidarian body form that attaches to a surface; mouth oriented upward, surrounded by tentacles

What are Scyphozoa?

Class of Cnidaria containing jellyfish; mostly medusal form (some with larval polyp); relatively large & muscular, umbrella shaped; GVC branches into many radial canals; mouth surrounded by oral arms; feeding mostly with nematocysts & tentacles (some use cilia & mucus); larvae are planula

What are Cubozoa?

Class of Cnidaria containing stinging jellyfish with squarish bell; fish predator; toxic to humans - can kill adult

What are Hydrozoa?

Class of Cnidaria with morphologially diverse members; may have complex life histories with medusae and polyps; GVC not divided by septa; polyp stage if present almost always colonial & polymorphis; covered by perisarc (chitin); margin of hydromedusa has tentacles & sensory structures (ocelli & statocysts); velum present

What kinds of animals are Cnidaria?

Corals, jellyfish, hydroids, anemones

What is the GVC?

Gastovascular cavity; functions for respiration, waste management, absorption, and as hydrostatic skeleton

What are key features of the Cnidarian body plan?

General structure is sac with tentacles; coloniality and polymorphism are common

What kind of skeleton do Cnidaria have?

Hydrostatic - muscles around a fluid filled mass; can have internal rods or spicules for support (organic or CaCO3) or extracellular CaCO3 or chitin

What are Anthozoa?

Largest class of Cnidaria; all are marine; includes corals and sea anemones (no medusa form; thick mesoglea; GVC divided by septa); many have symbionts; some filter feed or use mucus net; monecious or dioecious; invididual or colonial; subclass: Zooanthera (anemones & stony corals; many tentacles; external skeleton if present); subclass Alcyonaria (= octocorals, soft corals & relatives; 8 tentacles; internal skeleton when present)

How do Cnidaria reproduce?

Many types of asexual reprodution as well as regeneration; Sexual reproduction present - most are dioecious; gonads in either epidermis or gastrodermis; free spawn; produce planula larvae.

How do Cnidaria feed?

Most are carnivores (plankton, fish, etc.); capture food using nematocysts and tentacles; bring into GVC; digest & absorb; spit remains back out of mouth

What kind of nervous system and sensory equipment do Cnidaria have?

Nerve net; sensory structures on tentacles and base of bell in medusa; can sense light, balance (statocysts), chemosenors?

What does the name Cnidaria mean?

Nettle (stinging) animals

What kind of body cavity do Cnidaria have?

None (GVC is not a body cavity)

What kind of circulatory system do Cnidaria have?

None; diffusion & gastrovascular cavity; many ciliate cells lining GVC help to move fluids

What are some examples of hydrozoa life histories?

Only medusa form (Liriope); produces eggs & sperm; larvae forms medusa Large medusa; produces eggs & sperm; larvae form tiny feeding polyp that then produces medusa Medusa produces eggs & sperm; larvae forms into colonial polyp which buds off medusae (Obelia) Medusa is small, short-lived; produces eggs & sperm; larva forms colonial polyp (Millepora) Polyp produces medusa that remain attached to polyp colony; medusa produces eggs & sperm; larva forms colonial polyp (Hydractinia)

What is a medusa?

Pelagic cnidarian body form with a bell shape; mouth pointing downward surrounded by tentacles

What kind of digestive system do Cnidaria have?

Simple sac (single opening)

What are Zooantheria?

Subclass of Anthozoa that contains sea anemones, stony corals (numerous unbranched tentacles; skeleton when present is external

What kind of organization do Cnidarian have?

Tissue-level organization; diploblastic (2 layers of epithelium - epidermis + gastodermis, with mesoglea in between layers)

What are nematocysts?

Unique organelle in specialized cnidaria cells (cnidocytes); when triggered by touch, nematocyst explodes out of the cell; shoots out thread with "harpoon" that can ofter deliver poisons; captures prey; nematocyst size & shape is species specific

What is Mesoglea?

acellular "jelly" between epidermis and gastrodermis in cnidaria; contains protein fibers and polysaccharides, similar to vertebrate extracellular matrix

What is the ecology of Cnidaria?

almost all marine: common in pelagic & benthic habitats; many are important habitat engineers & predators

What is polymorphism?

condition in which individuals in a group can have different morphologies and functions (specilized cells in hydroids, such as the gonagium, for example) ASK MEGAN for verification

What kind of symmetry do Cnidaria have?

radial