Induced ovulation and embryonic development of ocellated puffer, Takifugu ocellatus

Abstract

Summary Acute injections of different hormones to induce ovulation in mature ocellated puffer, Takifugu ocellatus, collected from natural waters during the spawning season, were carried out to develop a reliable protocol for mass production of seed in this species. All experimental fish were divided into seven groups treated with: a saline injection (control), single or two injections of luteinizing hormone-releasing hormone analog (LHRH-a; single injection: 50 μg kg−1, two injections: 10 and 40 μg kg−1), single or two injections of pituitary (single injection: 6 mg kg−1, two injections: 1 and 5 mg kg−1) and single or two injections of human chorionic gonadotropin (hCG; single injection: 2500 IU kg−1, two injections: 500 and 2000 IU kg−1), respectively. The percentage of fish that ovulated in six hormonal treatments reached 100%, either with a single injection or with two injections whereas the fish in control group failed to spawn. There were no significant differences among all hormonal treatments in egg production, fertilization rate, or hatch rate (P > 0.05) except time to ovulation between a single injection group and the two-injection group (P < 0.05). The fertilized eggs of ocellated puffer were spherical, demersal, and adhesive. They had a mean oocyte diameter of 1.487 ± 0.106 mm (range: 1.404–1.560). The egg membrane was transparent and yolk was buff in color, containing a cluster of small oil globules. Thirty-four successive stages of embryonic development were identified and characterized. Fertilized eggs incubated at 18–20°C generally commenced hatching at 144 h after fertilization. Newly hatched larvae were about 3.26–3.45 mm in length. The induced ovulation technique using acute injections of hormones is an important step in the development of the culture of the ocellated puffer.