Follicle Size-Dependent Changes in Follicular Fluid Components and Oocyte Diameter in Antarctic Minke Whales (Balaenoptera bonaerensis)

Abstract

Abstract. The concentrations of various components of follicular fluid were compared among three groups of follicles (small, <5 mm; medium: 5-10 mm; large, >10 mm) with a control that consisted of the components of umbilical serum using seven pregnant Antarctic minke whales. Follicular oocytes recovered from the follicles were also used for measurement of oocyte diameter after removing the cumulus cells. The mean diameter of the ooplasm in the oocytes from the large follicles (143.2 µm) was significantly greater than those from the small (127.1 µm) and medium (131.7 µm) follicles, although there were no significant differences in diameter of the whole oocyte and thickness of the zona pellucida among the three follicular sizes. The osmolarity of the follicular fluid from the small follicles (363.3 mOsmol) was significantly lower than that of the medium follicles (388.9 mOsmol) and tended to be lower than that of large (381.9 mOsmol) follicles, respectively, both of which were similar to that of the umbilical serum (379.5 mOsmol). There was no significant difference in the concentrations of all components of the follicular fluid between the medium and large follicles. As compared with the values of the umbilical serum, the total-protein, glucose, albumin and chlorine concentrations of the follicular fluid from the medium and large follicles were significantly higher, and the total cholesterol and calcium concentrations were significantly lower. The concentrations of lactic acid (85.3-136.0 mg/dl) of the follicular fluid from the three groups of follicles were significantly lower than that of the umbilical serum (360.0 mg/dl). Among the follicles, the follicular fluid from the small follicles (136.0 mg/dl) contained a significantly higher concentration of lactic acid than that from the large follicles (85.3 mg/dl). The progesterone concentrations were not significantly different among the fluid from the three group of follicles and the umbilical serum: however, the estradiol 17-β concentrations of the follicular fluid increased with the size of the follicle (14.3 and 34.6 ng/ml for small and large follicles, respectively). These results offer new information concerning whale reproductive physiology, especially for improvement of in vitro oocyte maturation and related technologies in whales.

Production of cloned sei whale (Balaenoptera borealis) embryos by interspecies somatic cell nuclear transfer using enucleated pig oocytes

“…We previously showed [22] that the osmolarities of follicular fluid (363.3~388.9 mOsm) and umbilical serum (379.5 mOsm) in Antarctic minke whales exceeded the serum or plasma value in other domestic species (300 mOsm) [11,23]. Based on the high osmolarity of whale follicular fluid and serum, we designed a new medium with a high osmolarity for the culture of iSCNT whale embryos.…”

“…Whales differ from other mammals in terms of their follicle size, serum and follicular fluid compositions, and the oocyte maturation process [14,22]. In contrast to other domestic and experimental animals, few studies of whales have been conducted in the fields of gamete biology and assisted reproductive technology due to difficulties in obtaining somatic cells, spermatozoa, and oocytes.…”

Effect of Ovarian Status and Follicular Size on Grade and Maturation In Vitro of Bovine Oocytes in Relation with Follicular Fluid Composition.

“…(2014). However, concentration of lactic acid was determined using commercial kit (Determiner LA; Kyowa-Hakkou,Osaka, Japan) after Nagai et al (2007).…”

“…Concentration of P4 and testosterone were significantly (P≤0.05) higher in FF from the LF than SF. Also, the FF from SF contained significantly higher concentration of lactic acid than that from LF (Nagai et al, 2007). During the luteal phase, P4 is secreted in high concentrations by the CLs (Pradeep et al, 2009) from the granulosa and theca cells of bovine follicles (Hunter et al, 2004).…”

Recent progress in reproduction of whale oocytes

“…The osmolarity of whale follicular fluid (wFF) from the three follicle types is 363.3–388.9 mOsmol. Follicular fluid from large follicles has a lower concentration of lactic acid than that from the small follicles, but the estradiol-17beta (E 2 ) concentration of wFF increases as the follicle size increases (Nagai et al ., 2007).…”