Xorgansinus

Xorgansinus, often written as the X-organ–sinus gland complex, is a crustacean neuroendocrine structure that coordinates growth, metabolism, and development. It comprises the X-organ, a cluster of neurosecretory cells in the eyestalk, and the sinus gland, a terminal reservoir that releases hormones into the hemolymph.

Location and structure: In most decapod crustaceans, the X-organ lies in the frontal portion of the eyestalk’s nervous tissue; the sinus gland extends into the adjacent hemocoel via the sinus. The two components function as a functional unit in neuroendocrine signaling.

Hormones and function: The complex secretes members of the crustacean hyperglycemic hormone (CHH) family and molt-inhibiting hormone (MIH). CHH peptides regulate carbohydrate metabolism and osmoregulation; MIH inhibits the molting process by suppressing ecdysteroid production by the Y-organ. Together, these hormones help synchronize molting cycles with energy reserves and environmental conditions.

Regulation and significance: Secretion is modulated by photoperiod, circadian rhythms, nutrition, temperature, and salinity. The X-organ–sinus gland complex thus links environmental cues to physiological state, influencing growth, reproduction, and stress responses. The structure is a focus of crustacean endocrinology and has implications for aquaculture, where manipulation of molt cycles can affect growth rates.

Taxonomy and distribution: The X-organ–sinus gland complex is described in many crustaceans, including lobsters, shrimps, and crabs, but precise anatomy and hormone repertoires vary among taxa.

Related topics include crustacean endocrinology, X-organ, sinus gland, crustacean hyperglycemic hormone, and molting in crustaceans.