SEASONAL-VARIATION IN THE REPRODUCTIVE ACTIVITY OF OCTODRILUS-COMPLANATUS (OLIGOCHAETA, LUMBRICIDAE)

Octodrilus complanatus (Duges, 1828) a holandric species of the family Lumbricidae, follows according to Olive and Clark (1972) the reproductive strategy of continuous or semicontinuous reproduction. The lowest value of the water content during the annual cycle, was observed during August (27.58 % of the body weight), while the highest value was observed during May (78.82 % of the body weight). No change was noticed in the testes during the summer months. Changes were observed in the seminal vesicles. Their size decreases during summer and they display a characteristic brown tint. During the remaining months they have an intense white colour and are strongly swollen. A high degree of correlation between body mass and size of seminal vesicles was observed in mature individuals. The correlation, however, decreases during the summer months. No structural changes were observed in the seminal funnels during summer. During this period sperm ducts contain amoebocytes. The characteristic changes observed in the ovaries during the annual cycle are located at their extreme ends. A few germinal cells of small diameter were observed. There is no correlation between the body weight and the number or diameter of the ova in the samples taken during the summer months. No characteristic chain of mature ova was observed at the extreme end of the ovary during the summer months. Egg sacs and oviducts are small in size and seemingly are not functional. No spermatozoa were found in the seminal receptacles during the summer months. Their external diameter diminishes significantly at this time, A low correlation between body weight and the diameter of the third seminal receptacle was observed in the samples during the time interval between June and September.