gonopods

Gonopods are specialized reproductive appendages found in various arthropods, most notably crustaceans and myriapods. They are modified limbs that function in the transfer of sperm during reproduction and often differ in form from ordinary walking legs. The exact position, number, and structure of gonopods vary among groups, and their morphology is frequently used in species and genus identification.

In crustaceans, gonopods are typically modified appendages associated with the male reproductive system. They may be specialized pleopods or thoracic legs used to transfer sperm to the female during copulation. The gonopods often form part of a coordinated copulatory apparatus, and their arrangement can differ markedly between different crustacean lineages, contributing to taxonomic distinctions.

In millipedes (class Diplopoda), the gonopods are usually the posterior pair(s) of legs in males. These modified legs function to transfer sperm to the female, frequently by presenting or guiding a spermatophore to the female’s genital opening. The form and arrangement of millipede gonopods show considerable diversity and are important for species-level identification.

In other myriapods and certain crustaceans, gonopods may appear on different body segments and can take a range of forms from simple to highly specialized structures. Across groups, gonopods are a key feature of reproductive biology, reflecting adaptations to mating behavior and sperm transfer.

Etymology: the term derives from Greek gonos (seed, offspring) and pous (foot).