Crustacean endocrinology

Crustaceans express a diverse array of endocrine factors, such as neuropeptides, biogenic amines, and growth factors, which are mediated by an equally diverse array of membrane receptors, such as receptor tyrosine kinases (RTKs) and G protein-coupled receptors (GPCRs). The X-organ/sinus gland (XO/SG) in the eyestalk ganglia secretes crustacean hyperglycemic hormone (CHH) family neuropeptides that inhibit synthesis of molting hormones (ecdysteroids) by the Y-organ (molt-inhibiting hormone); inhibit synthesis of methyl farnesoate by the mandibular organ (MO-inhibiting hormone); and inhibit vitellogenesis and oogenesis in the hepatopancreas and ovary, respectively (gonad/vitellogenesis-inhibiting hormone). Other neuropeptides control carbohydrate and lipid metabolism (CHH), cardiovascular activity (crustacean cardioactive peptide and FMRFamide), gill ventilation (proctolin), osmoregulation (CHH), ecdysis behaviors and cuticle tanning (eclosion hormone, ecdysis triggering hormone, and bursicon), pigmentation (red pigment concentrating hormone and pigment dispersing hormone), and stress responses (CHH). Biogenic amines (serotonin, octopamine, and dopamine) may act as endocrine factors controlling cardiac output, gill ventilation, and osmoregulation. Growth factors (GFs), such as insulin-like peptides, epidermal GFs, fibroblast GFs, and platelet-derived GFs/vascular endothelial GFs control growth, sex determination, regeneration, and innate immunity. Understanding the control of muscle differentiation and growth by hormones and growth factors is key to the development of cultivated crustacean meat. The actions of neuropeptides and biogenic amines generally involve GPCR signaling, while the actions of growth factors involve RTK signaling. Methyl farnesoate, Methoprene tolerant/Krüppel homolog 1/E93 and ecdysteroid-responsive transcription factors have roles in molting, development, and reproduction.