what are some general body traits of cnidarians?
- two cell layers (epidermis and gastrodermis) and mesoglea in between
- radial symmetry
- tentacles around mouth
- one body opening (mouth = anus)
- gametes produced and stored in gastrovascular cavity
- nerve nets but no CNS
- muscles formed from specialized dermal cells
- carnivorous
what are some unique body traits of cnidarians?
- two potential body plans (polyp/medusa) + alternation of generations
- cnidae (organelles) found in cnidocysts (cells)
what are the two main types of cnidarian skeletons?
- calcium carbonate
- hydrostatic
what is the genus name of the symbiotic dinoflagellate found in many corals?
symbiodinium
what are the three types of specialized polyps in hydrozoic colonies?
gonozooids = reproduction
gastrozooids = digestion
dactylozooid = defense
what are the two layers of cnidarian bodies and the matrix in between?
- epidermis (outermost) and gastrodermis (innermost)
- mesoglea in between
what symmetry do cnidarians have?
radial
what is the structure of a cnidocyte?
contains a cnida that consists of a capsule and tube with coiled thread structures inside
describe how cnidae can be triggered
- mechanoreceptors and chemoreceptors on cnidocil (modified cilia) detect triggers
- shaft shoots out and expels thread
what are the three types of cnidae?
- nematocyst (penetrant and toxic)
- ptychocyst (adheres to prey)
- spirocyte (lassos prey)
what are the four classes of cnidarians?
anthozoa, cubozoa, scyphozoa, hydrozoa
what traits does anthozoa have?
- anemones, corals
- solitary or in colonies
- no medusa life stage
- can have either a hydroskeleton or calcified skeleton
- mesenteries in gut from aboral to oral ends
- three types of nematocyst containing tentacles: acontia (thin structures from stalk), acrorhagi (stubby structures forming a ring), catch tentacles (long structures near mouth)
what traits does hydrozoa have?
- polyp is dominant life stage, uses medusa for reproduction
- colonial polyps connected by stolons and shares gastrovascular system
- polyps can specialize (polymorphism) into gastrozooids, gonozooids or dactylozooids
- colony encased in perisarc sheath (chitin + protein)
what traits does scyphozoa have?
- jellyfish
- dominant medusa life stage
- planula develops into scyphistoma (polyp)
- scyphistomae stobilate to release ephyra (new medusa)
- use rhopalia containing statocysts to sense gravity
- additional sensory cells are ocelli (light) and tactile lappets (touch)
how are myxozoans unique?
- parasitic
- polar capsules release spores into host that rupture
what traits does cubozoa have?
- box-like medusa form with tentacles at each corner
- more developed nervous system
- no strobilation
- planula forms polyps which bud off to form medusae
what function does the mesoglea have?
- structural support
- forms connective tissue between two body layers
- helps circulate nutrients
what is the manubrium?
tube like structure that connects mouth to stomach
