Males were defined as those whelk with a penis, and females were defined as those whelk with a nidamental gland.
The nidamental gland is essential for forming egg cases and may require channeled whelk females to spend more energy on reproduction than do males.
Castagna and Kraeuter (1994) reported the seasonal gonad index of nidamental gland per meat weight (N/MW) at a range of 9.
During dissections of channeled whelk in our study, there were no signs of hermaphroditism; all whelk had either a penis or a nidamental gland.
After recording the total body weight (TW), each specimen was dissected to separate different organs and the following measurements of weight were recorded in grams: mantle weight (MW); head weight, including arms and tentacles (HW); viscera weight, including gills, stomach, cecum, hepatopancreas, and ink sac (VW); ovary weight, including oviduct and oviducal gland (OW); testis weight (TW); and nidamental gland weight (NGW).
where GW is the gonad weight, BW is the body weight, and NGW is the nidamental gland weight.
Besides indices, 1 of 3 maturity stages was assigned to the specimen collected in different seasons based on the color of accessory nidamental glands and size of the gonads according to Lipinski (1979).
There was a negative correlation between Gonado Somatic Index and Nidamental gland Somatic Index and each of total protein and lipids in different sexes (P = 0.
The presence of a spermatophoric sac in males and the orange or pink color of the accessory nidamental gland in females indicated the mature stage (Richard 1967; Riad 1993).
Total protein, lipids, and carbohydrates were plotted against the GonadoSomatic Index (GSI) and Nidamental Gland Somatic Index (NSI) documented in Gabr and Riad (2008) to link the temporal variation of these parameters to the animal's reproduction.
The seasonal variation of the same biochemical contents showed a similar trend in comparison with the Nidamental Gland Index (NSI) as shown in Figure 5.