Lecture 17: Porifera and Cnidaria
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What does phylum Porifera refer to?
the sponges
what are characteristics of porifera?
• lack symmetry • range in size • larvae stage is sessile (attached to one spot and don’t move)
what is the morphology of Porifera?
• no obvious tissues or organs (no gut, muscles or nerves) • structural support comes from spicules • tiny, hard needles or rods • calcium carbonate or silica • some sponges have only tough collagen protein networks for support (spongin)
what is Mesohyl?
• A gelatinous acellular layer b/w the outer ‘skin’ and the choanocyte layer • basically the filler that holds all the cells together
what is suspension feeding in porifera?
• tiny food particles are engulfed by phagocytosis at base of choanocyte cell • amoebocytes nudge up and take up food passed on by choanocyte • amoebocytes then carry the food and nutrients to other cells or use energy to make spicules or other structural material
what is the sponges reproduction like?
• mostly hermaphroditic (male and female at the same time) • they are sequential hermaphrodites meaning they are first one sex and then they change to the other • do not have ovaries or testes • eggs are modified from amoebocytes • sperm are modified from choanocytes • external or internal fertilization
what is the importance of sponges ecology?
• they filter feed which cleans the water • they have symbiotic mutualisms w/ single celled algae and other organisms • some are predatory • they help with pharmaceuticals like antibiotics and anticancer drugs
What does phylum cnidaria refer to?
Jelly fish, hydras, sea anemones, and corals
what are the characteristics of cnidaria?
• Eumetazoan: they have true tissues • radial symmetry • diploblastic: 2 germ layers and no mesoderm/coelom • organs are collective tissues specialized for different tasks • many house symbiotic algae
what are the 2 basic body forms of cnidaria?
Polyp (sessile form): oral end upwards, attached to a substrate (ex: sea anemone) Medusa (motile form): oral end downwards, moves freely through the water via hydrostatic skeleton (ex: jelly fish)
All cnidarians are _____ and are named for their unique cells called ____. These types of cells…
• predators and their unique cells are called cnidocytes • each cnidocyte contains very complex end-cellular structure and the most common type is nematocysts which help for catching prey
what do Cnidocytes do?
they act as a defence and catch prey • they do this one something triggers the spine of the cnidocyte by lighting touching the tip of the spine • they also have a stomach