Progesterone induces activation in Octopus vulgaris spermatozoa

The purpose of the present study was to determine whether Octopus vulgaris spermatozoa are activated by progesterone stimulation. Spermatozoa were col lected from the spermatophores in the Needham's sac of the male (MS) and fr om the spermathecae of oviducal glands of the female (FS). We used transmis sion (TEM) and scanning (SEM) electron microscopy to study the morphology o f untreated, Ca2+ ionophore A23187 and progesterone-treated MS spermatozoa, and untreated FS spermatozoa. We showed that ionophore and progesterone st imulation of MS spermatozoa induce breakdown of the membranes overlapping t he acrosomal region, exposing the spiralized acrosome. These modifications resemble the acrosome reaction observed in other species. FS stored in the spermathecae did not show the membranes covering the acrosomal region prese nt in the MS spermatozoa. When ionophore and progesterone treatments were p erformed in Ca2+-iree artificial sea water, no changes were observed, sugge sting the role of external calcium in modifying membrane morphology. Lectin studies showed a different fluorescence distribution and membrane arrangem ent of FS-untreated spermatozoa with respect to the MS, suggesting that spe rmatozoa transferred in the female genital tract after mating, are stored i n a pre-activated state. The plasma membrane of the untreated MS and FS spe rmatozoa was labelled with Progesterone-BSA-FITC, indicating the presence o f plasma membrane progesterone receptor. Taken together these data suggest that progesterone induces an acrosome-like reaction in MS spermatozoa simil ar to that induced by calcium elevation. In addition progesterone may play a role in the pre-activation of spermatozoa stored in the female tract, fur ther supporting the hypothesized parallelism between cephalopods and verteb rates. Mol. Reprod. Dev. 59:97-105, 2001. (C) 2001 Wiley-Liss, Inc.