This is similar to the
gonopodium of freshwater poeciliids, which also have a modified anal fin ray with specialized muscles that allow the
gonopodium to rotate during copulation (Rosen and Gordon 1953).
(1999) Wa = abdomen width; Lplc = propodus length of the largest cheliped; Lg = length of
gonopodium.
In males the anal fin is modified to form a structure that is used to fertilize females (
gonopodium).
Maturation stages (juvenile and adult) were distinguished by the size at which differential growth of the secondary sexual characters (males =
gonopodium length; females = abdomen width) in relation to the independent variable (CW).
The researchers examined the role of a pair of claws at the tip of the
gonopodium of the male guppy (Poecilia reticulata) - essentially the fish's penis.
Most of the fin structure in the male fish is modified into bone, comprising the
gonopodium. This study represents an ultra-structural characterization of the internal morphology of the mosquitofish anal fin.
Phalloceros harpagos is a viviparous species and present marked sexual dimorphism in size, with larger and more robust females (ENDLER, 1983), and morphology, with the presence of a
gonopodium in males (LUCINDA, 2008), and beyond the continuous spawning, presents high fecundity, small size at first maturity and high metabolism, as intrinsic characteristics of the species.
Thrusting was defined as attempts to introduce the male's
gonopodium into the female's genital opening.
Mature male sailfin mollies have a modified anal fin called a
gonopodium, which they insert into the gonopore of a female during a mating attempt.
gracilis, being the modification of the anal fin in males to form a
gonopodium the main sexual distinctive characteristic.
The long-finned fish have problems with mating; the males have difficulty inserting the
gonopodium and transferring spermatophores.
The criterion of hook development on the
gonopodium (Angus et al.