Gonadal Development and Fertility of Triploid Grass Puffer Takifugu niphobles Induced by Cold Shock Treatment

Abstract

Tiger puffer Takifugu rubripes is one of the most valuable fish species in Japan; however, there has not been much progress in their selective breeding until recently despite their potential in aquaculture. Their long generation time and the large body size of their broodstock make breeding difficult. Recently, we made a surrogate broodstock, which produced gametes of different species in salmonids. Therefore, by using closely related recipients, which have small body sizes and short generation times, it is possible to accelerate breeding of the tiger puffer. Thus, we considered the grass puffer Takifugu niphobles, which has a short generation time and a small maturation size, as a potential recipient for gamete production of the tiger puffer. Furthermore, if sterile triploid individuals are used as recipients, the resulting surrogate broodstock would produce only donor-derived gametes. Therefore, we examined conditions for inducing triploidy by suppressing meiosis II to retain the second polar body in grass puffer. We found that cold shock treatment, which is 5°C for 30 min starting from 5 min after fertilization, is optimal to obtain high triploidization and hatching rates. Although the resulting triploid grass puffers produced small amounts of gametes in both sexes, the offspring derived from the gametes could not live for over 3 days. Furthermore, we found that triploid grass puffer showed normal plasma sex steroid levels compared with diploids. These are important characteristics of triploid grass puffer as surrogate recipients used for germ cell transplantation.

Maturation and Gonad Development of Yellowspotted Puffer Torquigener flavimaculosus (Osteichthyes: Tetraodontidae) from Iskenderun Bay, North-eastern Mediterranean

“…Maturation in males was concomitant with maturation in females. These findings were similar to those reported by Hamasaki et al (2013), Matsunaga et al (2014). In the ovary, the level of tetrodotoxin was reported to be highest (Thattiyaphong et al, 2014;Itoi et al, 2017;Acar et al, 2017).…”

“…Oogonia of T. flavimaculosus divided and turned into prenucleolus stage, which subsequently grow within follicles, formed cortical alveoli, entered vitellogenesis underwent maturation and finally ovulated. The changes that occurred during these phases were similar to those reported for other pufferfish (Hamasaki et al, 2013;Matsunaga et al, 2014). Based on histological observations, maturation in T. flavimaculosus occurred from June to October, which was suggested as a spawning season.…”

Meiotic gynogenesis with heterologous sperm in the mandarin fish Siniperca chuatsi and evidence for female homogamety

“…An optimal combination of temperature, duration and initiation time is critical for the cold shock treatment since even small variations may result in remarkable changes in the number of gynogenetic diploids obtained (Chen et al, ). The suitable cold shock temperature to successfully inhibit the extrusion of the second polar body is strongly affected by the optimal spawning temperature and the gap between the optimal cold shock temperature and the spawning temperature is approximately 15°C (Hamasaki, Takeuchi, Miyaki, & Yoshizaki, ). Since natural spawning of the mandarin fish generally occurs (Spring) between 18°C and 25°C in Wuhan, an optimal cold shock temperature for this species is likely to be between 3°C and 10°C.…”

Modeling the reproductive impact of aquaculture-produced sexually fertile triploids on conspecific diploid populations

“…In species where triploid sterility is incomplete, gametes can be released and produce non-viable progeny (Lozano et al 1987, Guo & Allen 1994a, Momotani et al 2002, Meng et al 2012, Hamasaki et al 2013 or offspring with varying degrees of aneuploidy (He et al 2004). If one or both sexes in a triploid population produce functional gametes, they could interfere with the normal reproductive process in a conspecific diploid population that shares the same habitat.…”