Internal Transport

• have well-developed heart
• open circulatory system: blood not always within vessels
• In spiders and some insects...
  --->heart is long and narrow which stretches along abdomen
• In lobsters and crayfish...
  --->blood pumps through arteries and go into smaller vessels
  --->enters tissues and then leaves vessels into sinuses (spaces in tissue)
  --->the blood is found in a cavity around heart where it re-enters heart through openings