For instance, in the genus Thor, a clade that includes 12 species worldwide (De Grave et al., 2009), two species have been confirmed as
gonochoric (T.
edule is a
gonochoric species and, although hermaphrodites or even sex reversals have been found occasionally (Kingston 1974, Fernandez Castro et al.
Alternatively,
gonochoric zooids are known to occur in certain species (e.g., Dyrynda and Ryland, 1982; Hughes and Hughes, 1986).
Results from different lines of investigation indicate that determining gender is essential in gonad determination either in
gonochoric or hermaphrodite species, but fewer studies have been done on the mechanisms of sex ratio variations in pearl oysters.
In brief, colonies are
gonochoric. Females release eggs during predictable spawning events that on San Salvador, Bahamas, occur in November and December, usually during the week following the new moon.
Some exhibit hermaphroditism, but the majority are
gonochoric, whereas some display sex reversal under certain conditions (Pouvreau & Gangnery 2000).
The
gonochoric, free-spawning mode of reproduction seen in C.
irus is
gonochoric. In January, most clams were in the resting phase, although a small number of females showed small oogonia on their follicular epithelium.
Methanoaricia dendrobranchiata is a
gonochoric species, but the sexes cannot be distinguished externally.
According to that study, this species is
gonochoric and, unlike in other bivalves, spawning takes place during times of low food availability.
The intertidal snail Littorina obtusata is
gonochoric. Females lay benthic egg masses containing 50-150 eggs (Bandel, 1974) in which embryos undergo direct development and emerge as crawling juveniles.
It is
gonochoric with internal fertilization and direct embryonic development, with the presence of nurse eggs in the egg capsule as supplementary food (Penchaszadeh 1976).