Factors Affecting in Vitro Maturation of Minke Whale (Balaenoptera acutorostrata) Follicular Oocytes

Abstract

Factors affecting in vitro maturation (IVM) of minke whale (Balaenopetra acutorostrata) follicular oocytes were investigated. In experiment 1, recovery rates for oocytes from follicles of different sizes (small, 1-5 mm; medium, 6-10 mm; large, > or = 11 mm) were similar in both immature (54.7%) and mature (53.5%) females, and the follicular sizes did not affect recovery rate. Approximately half the oocytes recovered from small follicles in immature (55.5%) and mature (52.1%) whales were surrounded by at least a few layers of cumulus cells. Before culture, 71.7% and 61.2% of oocytes from immature and mature whales, respectively, were at the germinal vesicle stage. For IVM, effects of serum type, hormones, and additional cumulus cells (experiment 2) and effects of culture durations (24-120 h, experiment 3) were investigated. The three factors investigated in experiment 2 did not affect maturation rates. TCM199 supplemented with fetal whale serum, hormones, and additional cumulus cells showed the highest rate (21.6%) of matured oocytes and resulted in a significant difference from the rate in medium with only fetal calf serum added (6.6%). The first oocyte with an extruded polar body was observed after 84 h of culture. The maximum rate (27.3%) of matured oocytes was obtained by 96 h of culture, but there was no significant difference in the proportions of matured oocytes between 90 and 120 h in culture. These results indicate that in vitro nuclear maturation of immature follicular oocytes in minke whales can be induced.

Effects of cryodevice type and donors' sexual maturity on vitrification of minke whale (Balaenoptera bonaerensis) oocytes at germinal vesicle stage

“…The previous IVM system for whale oocytes (Fukui et al, 1997a;Asada et al, 2001a) included approximately 310 mosmol M199 supplemented with 15-20% fetal whale serum (FWS) for the IVM medium and 96-120 h as the culture period, resulting in an approximately 30% IVM rate in fresh oocytes. The preliminary measurement of osmolarity for wFF led us to prepare a modified IVM medium in the present study.…”

“…The nuclear maturation rate of minke whale oocytes is approximately 30%, even after 120 h of in vitro maturation (IVM) culture (Fukui et al, 1997a; 4 Kato Ladies Clinic, Tokyo 160-0023, Japan. 5 The Institute of Cetacean Research, Tokyo 104-0055, Japan.…”

Morphological Observations of Frozen-Thawed Spermatozoa of Southern Minke Whales (Balaenoptera acutorostrata).

“…Fukui et al [14,15] attempted in vitro fertilization (IVF) of in vitro matured minke whale follicular oocytes using frozen-thawed spermatozoa, but the number of cleaved oocytes following IVF was low (5-6% of inseminated oocytes). This low cleavage rate may be due to the high proportion of morphologically abnormal spermatozoa ascertained in the present study.…”

Attempt at Intracytoplasmic Sperm Injection of In Vitro Matured Oocytes in Common Minke Whales (Balaenoptera acutorostrata) Captured During the Kushiro Coast Survey

“…The present study was conducted to produce common minke whale embryos by determining the appropriate duration for IVM (30 or 40 h: Experiment 1) and by intracytoplasmic sperm injection (ICSI) and assessment of embryonic development after IVM culture (40 or 48 h) of maturted oocytes from prepubertal and adult common minke whales (Experiment 2). Regarding the duration of IVM culture, our previous reports [1,3] showed that the nuclear maturation rate of Antarctic minke whale oocytes is approximately 30%, even after 96-120 h of IVM culture. In those studies, 15-20% fetal whale serum was incorporated into the IVM media with osmolarity of approximately 310 mOsm, but the IVM media was not supplemented with whale follicular fluid (wFF).…”

“…tudies of in vitro maturation (IVM), in vitro fertilization (IVF) and development of Antarctic minke whale (Balaenopetera bonaerensis) oocytes have previously been conducted in our laboratory [1][2][3]. Although minke whale oocytes developed to the early morula stage following IVM and IVF [3], no blastocyst stage embryos have been obtained.…”