- Phylum Cnidarian
- Class Hydrozoa
Notable: attach to rocks with a pedal disk
, a mouth at the end of a raised region called the hypostome
Feed: predatory- prey contacts a tentacle and is immobilized by exploding cnidocytes.
It is then slowly engulfed into the mouth. Body cavity: coelenteron
Reproduction: asexual budding
. Sexual: temporary ovaries or testes grow in epidermis. Eggs are fertilized and dropped off with a thin chitin coating.
Development: alternates between medusa and polyp stage. Polyps
form branching hydroid colonies
, a highly branched coelenteron. Some form hydranths
with a mouth surrounded by tentacles for feeding. Others form gonangia
for reproduction. Tiny medusa
bud and escape.
Movement: glide on pedal disc. Somersaulting end-over-end. Walking on their tentacles. Float by extruding a bubble.