Arthropodetics (cont)

Arguably the most successful and diverse phylum of animals, comprising 3/4 of animal species colonising all available media (earth, air, water). This Phylum includes insects, spiders, scorpions, trilobites, crustaceans.



An aesthetically pleasing diagram of one proposed arthropod taxonomy here
Vetted arthropod links- quite good:

http://faculty.fmcc.suny.edu/mcdarby/Animals&PlantsBook/Animals/07-Arthropods.htm
http://www.biology-online.org/10/6_arthropods.htm
http://www.peripatus.gen.nz/Taxa/Arthropoda/Index.html
http://www.palaeos.com/Invertebrates/Arthropods/Arthropoda.htm
http://www.ucmp.berkeley.edu/arthropoda/arthropoda.html

As alluded, homeobox (hox) genes seem to allow shorthand for the repetition of segments, often specialised in tagmentation.



Just as in shell shapes, small changes in hox genes can result in major morphological differences. Lobsters and crabs, both decapods, while strikingly different in shape are strikingly similar in form and structure.

What features aided arthropods' success?

This is the best all-round resource trawled.

Primal features (shared with annelids, molluscs)-
Mass-limited, large surface area to volume ratio
Haemocoele circulation (no vascularisation)
Electrotonic synapses

Novel features-
Moultable exoskeleton
Antennae/ sense organs
Spiracles/brachiae with oxygenation by contact between haematocoele and tissues
Repetition and specialisation of a primal segment(haemocoele, neural tract, muscle, pair of appendages)
Jointed limbs to provide leverage and more rapid motility
Wings (insects)