BIOL 112 Lecture 27

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Cnidarians

Bioluminescent Proteins

Green Fluorescent Protein (GFP) isolated from jellyfish

Very small: ~280 amino acids

Emits green light in response to UV light

Allows us to look at dynamic processes (specific cells and specific processes) non-invasively by inserting GFP gene into genome sequence

Eumetazoa/Bilateria/Ecdysozoa

Nematodes and Arthropods

Tough exoskeleton (cuticle) that is molted periodically (ecdysis; hence the name)

• Prevents dessication and microbes.
• made of collagen in nematodes
• chitin in arthropods

Muscles attach to cuticle through epidermis via complexes

Metamorphosis:

Incomplete

juveniles look like adults, only smaller

e.g. nematodes

Complete

juveniles look totally different from adults

e.g. butterflies

Molting is hormonally regulated

• tissue growth is coordinated with timing of molt
• pesticies mess with this hormonal process without killing the plants

Nematodes

roundworms

General characteristics:

• Non-segmented
• either parasitic or free-living
• triploblastic: ectoderm = hypodermis (beneath cuticle); mesoderm = muscle, endoderm = gut
• pseudocoelomate

Best-understood is Caenorhabditis elegans

• 1mm long
• ~1095 cells
• ~302 (hermaphrodite) / 383 (male) neurons
• Move in a sinusoidal wave by relaxation/contraction wave in muscles; controlled by ventral nerve cord motor neurons
  • Compare to peristalsis movement of annelids by contraction of circular and longitudinal muscle.