The crustacean endocrine system and pleiotropic chemical messengers

Abstract

In this chapter, I first present a brief overview of the hormones (intraorganismal chemical signals) and endocrine glands that have been described in crustaceans. This overview focuses on decapods and the physiological processes of molting, metabolism, reproduction, and pigmentation. The hormones include ecdysteroids (molting hormones), molt-inhibiting hormone, methyl farnesoate, crustacean hyperglycemic hormone, androgenic gland hormone (AGH), and chromatophorotropins. I briefly discuss some of the work on the regulation of crustacean behavior by neurotransmitters, especially in respect to aggressive behavior. Evidence is then presented supporting the role of crustacean hormones as pheromones (intraspecific chemical signals). In particular, I describe the experiments demonstrating that ecdysteroids have pleiotropic activities. These experiments include the observations that ecdysteroids (1) are present in urine in varying amounts over the course of the molt cycle; (2) modulate aggressive behavior in a manner that correlates with hemolymph and urinary hormone levels; and (3) can be detected in the environment by olfactory neurons. There is evidence that the AGH may also act as a mating pheromone. I conclude my chapter by describing how the arthropod molting hormone can act as an allelochemical (interspecific chemical signal) in a pycnogonid (sea spider). Pycnogonids can accumulate high concentrations of ecdysteroids that serve as feeding deterrents against crustaceans that are potential predators.