174 RECOVERY OF LONG-BEAKED COMMON DOLPHIN OOCYTES FROM KOREAN WATERS

Abstract

The aims of this study were to collect oocytes from ovaries of Delphinus capensis (long-beaked common dolphin) and to examine the morphological characteristics of their reproductive organ. Female genital organs were collected from 2 incidentally caught Delphinus capensis (ID-96: estimated 5–6 years, and ID-97: estimated 7–8 years). Collected ovaries were transported to the laboratory over 3.5 h in 0.9% saline at 39°C. To perform assisted reproductive techniques in wild animals, it is important to maximize the number of oocyte recovered per ovary. In this study, Delphinus capensis oocytes were collected by 2 methods: (1) aspiration of visible follicles (2 to 3 mm in diameter) and (2) remnant dissection, in which the ovary is finely dissected. The collected cumulus–oocyte complexes (COC) were separated by ovary of origin and collection method. Oocytes were subjected to in vitro maturation (IVM). Immature oocytes were placed into IVM medium [TCM-199 supplemented with 10% (vol/vol) fetal bovine serum, 0.5 IU mL^–1 LH, and 0.5 IU mL^–1 porcine FSH] in the 4-well dish for 120 h at 37°C in 5% CO₂ in a humidified atmosphere. The uterus type was observed to be a uterus bicornis. Morphology of ovary was similar to the bovine ovary among land animals. In total, 114 oocytes were obtained. From the ovary of ID-97, the number of oocytes recovered by aspiration and ovary dissection were 15 and 57, respectively. However, only 42 oocytes were recovered by ovary dissection from the ovary of ID-96. The number of oocytes recovered per ovary by dissection (49.5 ± 7.5) was higher than that by the aspiration (7.5 ± 7.5) method, but not significantly different (P = 0.06). For accurate statistical analysis, additional trials will be performed. Most oocytes had either no cumulus cells or had only 1 to 2 layers attached to the zona pellucida enclosing a homogeneous cytoplasm. After IVM, all oocytes were at the metaphase I stage, with even fewer attached cumulus cells than at recovery. To summarise, we describe the gross morphology of the female reproductive tract of the long-beaked common dolphin and determined that dissection of the ovary is required for maximal recovery of oocytes.

This work was supported, in part, by a grant from the Next-Generation Bio Green 21 Program (No. PJ00956901), Rural Development Administration, and the National Research Foundation of Korea Grant funded by the Korean Government (NRF-2012R1A1A4A01004885, NRF-2013R1A2A2A04008751), Republic of Korea.