The lowest levels of plasma estradiol were verified in this photoperiod treatment, indicating that the permanent illumination affects the sexual hormones segregation, generating inhibitive effects upon the vitellogenesis
. This set of results agree with the observed in other species (Jourdan et al., 2000; Hansen et al., 2001; Rad et al., 2006; Taranger et al., 2006), where the absence of darkness has a generalized inhibitive effect on reproductive functions.
The differences found between ovary cells by qualitative and quantitative histological analyses lead us to classify Lithodes santolla oogenesis into five sequential stages (Table 2): 0 multiplication, I previtellogenesis, II vitellogenesis
, III maturity and IV spawning.
Stage II (vitellogenesis
) was characterized by the presence of early vitellogenic oocytes (Vol).
1C), atretic oocytes at stage 4 (atretic oocytes at early vitellogenesis
The resting ovary has small, mostly non-yolked oocytes and is ready for vitellogenesis
. In our study, maturity status of both sexes was assigned to each shark, at the time of dissection, on the basis of all previously described reproductive organ characteristics and was verified by comparison with measurements taken by Jensen et al.
Post-diapause females had ovaries with signs of vitellogenesis
, including partially developed oocytes.
As a consequence, high temperatures may also affect vitellogenesis
and reproductive performance in aquatic invertebrates.
2002): maturing (vitellogenesis
), uneyed (fertilized), eyed, spent, and resting (transitional).
Sex differences in lipid metabolism have been reported with laying hens showing an estrogen enhanced hepatic lipogenesis in order to meet the demand for vitellogenesis
Tissular and cellular structures in ovaries: NC, nuclear chromatin; P, perinucleolar; CA, cortical alveolus; Vt1, early vitellogenesis
; Vt2, late vitellogenesis
; MN, migrating-nucleus; POF, Post-ovulatory follicle; POF-L, late post-ovulatory follicle; AT, atresia; TR, tissue in reabsorption.
The gradual increase in the size of the ovarian cells has been attributed to the deposit of lipid in the ovaries during vitellogenesis
(Revathi, Iyapparaj, Munuswamy, & Krishnan, 2012; Castiglioni, & NegreirosFransozo, 2006; Gregati, Fransozo, Lopez-Greco, & Negreiros-Fransozo, 2010).
During progression of the follicles from the anterior to the posterior part of the vitellarium, vitellogenesis
takes place and the size of the oocyte increases (Figure 4(c)).