BIOL 112 Lecture 29

« previous | Wednesday, November 7, 2012 | next »

Ecdysozoa: Arthropoda

Cataglyphis fortis (desert ant)

Counts number of strides and uses polarized light orientation (ocelli sensory organ) to navigate over a featureless environment.

Circulation and Gas Exchange

triploblastic invertebrates have 2 types of circulation:

1. open - most invertebrates
2. closed - veins and arteries (annelids and cephalopods)

Arthropods

• open tubular heart
• true coelom
• Heme-type molecules (equiv. blood)
• spiracles (external opening) circulate air through trachea directly to muscle tissue

Nematodes

• no heart

Aquatic

small

Gas exchange across body surface

large

gills - thin endodermal tissue filled with coelomic fluid

exchange occurs directly with water

Evolution

Appeared during devonian

1. Oldest fossils were annelid-like
2. Appendages (millipede-like)
3. Specialization of segments

Subphylum Hexapoda

most successful sub-phylum

• 6 legs
• wings - exaptation of thermoregulators or gills?
  • equipped with sensory hairs

Reproduction

typically dioecious

Behaviors:

• courtship: complex signals (olfactory, mechanosensory (touch), gustatory (taste), visual) determine conspecific and fitness
• copulation
• internal fertilization

Best studies in Drosophila melanogaster