Gonopore

Definition

The external genital opening through which gametes are discharged; in arthropods, the terminal aperture of the reproductive tract. In most hexapods, including the vast majority of insects, a single median gonopore serves both sexes—females releasing eggs from the common oviduct, males emitting sperm via the ejaculatory duct. Mayflies (Ephemeroptera) are a notable exception, retaining paired gonopores, a plesiomorphic condition reflecting their basal phylogenetic position among winged insects.

Etymology

From Greek gonos (offspring, seed) + poros (passage, pore)

Example

In a female grasshopper, the gonopore lies on the posterior margin of the eighth abdominal sternite, concealed beneath the subgenital plate; in males, it opens at the apex of the aedeagus.

Synonyms

• gonadopore

Related Terms

• ovipore
• Aedeagus
• Oviduct
• Ejaculatory duct
• genital chamber
• spermatheca
• gonapophysis

Usage Notes

Specialists distinguish the gonopore (the actual pore) from surrounding structures such as the genital chamber or external genitalia; the term is sometimes used interchangeably with 'gonadopore' in older literature. Paired versus single gonopores carry phylogenetic significance in pterygote insects.