BIOL 2030 Chapter Notes - Chapter 2: Hydroida, Planula, Osculum
26 Apr 2016
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Grantia: has calcareous spicules (see below: the body wall highly folded; fingerlike projections. Class hydrozoa contains both polyp and medusoid forms that occur in successive stages of the life cycle. The polyps are of two main types: gastrozooids ( feeding polyps) and gonozooids (for asexual reproduction) the medusoid dstage of the life cycle reproduces sexually to produce a planula larva. Order hydroida are well developed polypoid generation either solitary or colonial which usually buds off as free medusa. E. g. , hydra which is solitary with no medusoid stage; velella and porita, which are free floating polymorphic colonies; obelia. Order siphonophora consisting of polyps and medusa; upper ends of the colony is usually a supporting float;medusa are attached to the stem, rarely free;marine. Class scyphozoa cnidarians with the medusoid stage as the main stage in the life cycle. The polypoid form is limted to a larval stage.
