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Final

BIOL 111 Study Guide - Final Guide: Sternum, Hydrostatic Skeleton, Planula


Department
Biology (Sci)
Course Code
BIOL 111
Professor
Suzanne Gray
Study Guide
Final

Page:
of 1
Organism
Phylum Cnidarian Class Hydrozoan Gonionemus
Brief
Description
Medusa Stage, yet spends most of its time clinging to sea-grasses
Contains a thick mesoglea (acts as a hydrostatic skeleton and provides
buoyancy)
Can be poisonous due to toxins in the nematocysts
Reproduction
Sexual Reproduction: sperm and egg are released into the water
Egg produces a small, larvae called a planula
Planula attaches to an object and begins its life as small polyp
Soon develops into a medusa form, when ready
Body
Structures
Bell: dome-shaped structure that contains the epidermis, gastrodermis
and mesoglea
Tentacles: arms that hang out of the bell, used for capturing prey and
attaching to objects
Tentacular bulbs: dark swellings at the base of each tentacle, contain
interstitial cells that develop into cnidocytes when old ones get
discharged
Adhesive pads: at the tip of each tentacles, used to attach to objects
Cnidocytes: stinging cells that occur in spiral swellings (batteries) along
the length of the tentacles
Velum: shelf underneath the bell, assists in contractions up, downwards
is passive movement = sinking
Manubrium: tube that hangs down, ending with the mouth, homologous
to the hypostome (dark square)
Mouth: located at the base of the mouth, ingestion occurs, contains
fleshy projectiles around it called oral lobes that assist in digestion
Ring Canal: four canals radiating from the manubrium (extensions of the
stomach)
Statocysts: small swellings between the bases of the tentacles, sensory
cells that perceive the direction of gravity
Gonads: four light brown-colored gonads that hang down like ruffles
parallel to the ring canal