Zoology 10th Edition by Stephen Miller,John Harley

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Because annelids have a well-developed and cephalized nervous system, a well-developed circulatory system, and a large coelom, their well-developed endocrine control of physiological functions, compared to the molluscs or nematodes, is not surprising. In invertebrates, the endocrine system of a crustacean, such as a crayfish, controls such functions as molting, sex determination, and color changes. In order to better understand this molting process, see figures 25.5 and 25.6.
Explain several functions regulated by invertebrate endocrine systems.
FIGURE 25.5 Control of Ecdysis (Molting) in Crustaceans. ( a ) Neurosecretory apparatus in a crustacean eyestalk. ( b ) Flow diagram of the events inhibiting molting and ( c ) causing molting. (MIH = molt-inhibiting hormone.) Redrawn with permission from Richard C. Brusca and Gary J. Brusca. INVERVERTEBRATES. Copyright © 1990 Sinauer Associates. Inc., Sunderland, MA.
FIGURE 25.6 Control of Ecdysis (Molting) and Development (Metamorphosis) in an Insect. ( a ) Anterior end of an insect, showing the location of the brain hormone, juvenile hormone, and ecdysone secretory centers. ( b ) Flow diagram of the events initiating molting in an insect. ( c ) Flow diagram of the events of insect metamorphosis as regulated by a decrease in the production of juvenile hormone.