Marine Zoology Homework2: Contrast Porifera and Cnidarians

Differences Between Porifera and Cnidaria:

1. Porifera do not have specialized tissues.  Cnidaria do.

2. Porifera are sessile as adults.  Cnidaria vary.  Some are sessile as adults (e.g. anemones, corals), but some are planktonic as adults (e.g. jellyfish).

3. Porifera have hard skeletal elements called spicules.  Although corals build a hard exoskeleton, cnidaria do not have spicules.

4.  Cnidaria have powerful stinging cells called nematocysts.  Porifera do not.

5.  Cnidaria have tentacles.  Porifera do not.

6.  Porifera are asymmetrical.   Cnidaria have radial symmetry.

7.  Porifera have pores called ostia through which they take in water (and plankton), and an opening called an osculum through which filtered water is expelled.  Cnidaria do not have these structures.  They have a single opening that acts as both mouth and anus.

8.  Almost all sponges are filter feeders.  All cnidaria are predators.

9.  Porifera do not have any sort of a nervous system.  Cnidaria have a primitive response system.

10.  Their larvae are different.  Porifera have lavrae with long flagella.  Cnidarians have larvae with shorter cillia.