Typically, reproductive potential is estimated by strip spawning and quantifying the number of eggs recovered from each female; however, strip spawning involves soaking the gonad in a chemical such as dithiothreitol (DTT) which induces germinal vesicle breakdown, a disintegration of the coating around the egg that would be removed naturally by passage through the gonoduct
(Courtney 1927, Johnson & Johnson 1950, Smiley 1986).
Eggs were removed first from the gonoduct
and rinsed with fresh seawater using a 60-[micro]m mesh as precaution to remove any possible allosperm from the eggs.
The gonadal lobes are horizontally positioned since the gonopore (gonoduct
connection) to posterior area of visceral cavity, and the narrower lobe is lying on the ventral side (lower lobe) of the cavity and the wider is up (upper lobe) (Fig.
In individuals having a gonad predominated by oogenic tissue and various developmental stages of oocytes, a small region appearing identical to inactive (non-secreting) TG tissue was present in the caudal region of the gonad closest to the gonoduct
. Among reproductively inactive individuals within the above group, only primary growth (PG) oocytes were present.
Alterations of the germinal epithelium during the adult reproductive life history: The reproductive cycle of the golden mussel was classified in phases based on the alterations of the germinal epithelium (Boltovskoy et al., 2015) considering the stages (and steps) of the germ cell differentiation, predominant type of germ cell, repletion of gonadal tubules, and the presence of mature germ cells in the gonoduct
. Therefore, reproductive phases of males were recognized according to the presence of spermatogonia, primary and secondary spermatocytes, spermatids and spermatozoa.
During development, the gonoduct
begins to form and grows from the gonad to the dorsal region of the body wall.
In the spawning season some post-ovulatory follicles had an opening to the ciliated gonoduct
through which mature oocytes had been released (Fig.
The extent of anatomical malformations is dependent on the concentration of TBT in the environment (Gibbs & Bryan, 1986) and can range from mild, forming a pseudopenis primordium to very severe obstruction of the gonoduct
(Oberdorster & McClellan-Green, 2002).
The description of morphological aspects of the female gonadal portion was based on the observation of: (a) the macroscopic aspects: coloration, granulation and appearance of the gonad; and (b) the microscopic aspects: the aspects of oocytes, follicle walls, inter and intra follicular spaces, tube (gonoduct
), connective tissue and disintegration of the gametes.
On the posterior part, the ovaries continue in a short gonoduct
. Immature ovaries are whitecoloured with small black dots due to melanophore cells that, during development, start to proliferate and cover the whole surface, in consequence, the gonads become completely black.
californica, a simultaneous hermaphrodite, possess two evaginations of the common genital gonoduct
: the seminal receptacle and the copulatory bursa (Hadfield and Switzer-DunSap, 1984).
Ziegenhorn & Thiem determined that the reproductive system in Fissurella crassa Lamarck, 1822 consisted of a gonad that opened to the right kidney through a gonoduct
which contained a gland in its internal wall, and which was also observed in females of Fissurella oriens Sowerby, 1835 (under Fissurella alba Philippi, 1845) and Fissurella limbata Sowerby, 1835.