Use of an Emulsion Prepared with Lipophilized Gelatin for the Induction of Ovarian Maturation in the Japanese Eel <i>Anguilla japonica</i>

Abstract

A new type of water-in-oil-in-water (W/O/W) emulsion using lipophilized gelatin (LG) and cotton seed oil was developed for the administration of salmon gonadotropin (sGtH) to induce ovarian matura tion in the Japanese eel. Hormone-releasing properties of the LG emulsion were compared with a W/O type emulsion prepared with Freund's incomplete adjuvant (FIA) and saline solution in in vitro and in vivo experiments. These results indicated that the LG emulsion had hormone-releasing properties differ ent from those of the saline solution and the FIA emulsion. Cultured immature female Japanese eel (BW, 566 to 1017 g) received a weekly intramuscular injection (total of 10 injections) of the LG emul sion, the FIA emulsion or the saline solution, each of which contained sGtH. In the group treated with LG emulsion containing sGtH, all fish matured showing small individual variations in GSI and percent increases in body weight. Although the FIA emulsion was also effective in inducing ovarian maturation, it is possible that ovarian maturation was inhibited by antibodies produced against sGtH. Administra tion of sGtH in saline solution required a longer period of time for the completion of ovarian matura tion. Therefore, it appeared that the LG emulsion containing sGtH was more effective than other prepa rations in inducing ovarian maturation in eel.

Adequate interval of sGTH administration to induce vitellogenesis, and induction of ovulation by simultaneous administration of sGTH and 17alpha-hydroxyprogesterone in the Japanese eel

“…These profiles were similar to those of results previously reported. 5,12,13 In the groups injected biweekly, the BW and plasma levels of T and E 2 repeated biweekly cyclic fluctuations responding to the sGTH injection. These results clearly indicated that changes in the BW and plasma steroids were artificially caused by exogenous hormone (sGTH) treatments.…”

“…LG was prepared using fine gelatin powder (Wako Chemical Industries, Osaka, Japan) and palmitic anhydride (Sigma, St Louis, MO, USA) according to Kawazoe et al 3 The LG emulsion was prepared by mixing LG solution and cottonseed oil (Kanto Chemical Co., Tokyo, Japan) and the sGTH was prepared from salmon pituitary according to methods described previously. 5 Emulsion for the simultaneous injection of sGTH and 17αP in the release test and induction of ovulation was prepared by mixing LG solution containing sGTH and cottonseed oil containing 17αP. Emulsion for a single injection of sGTH alone in the release test and induction of vitellogenesis was prepared by mixing LG solution containing sGTH and cottonseed oil.…”

“…17αP, testosterone (T) and estradiol‐17β (E 2 )) and sGTH II were measured by radioimmunoassay (RIA) following the methods described previously. 4–6 Data were treated statistically using the Student's t ‐test and the Cochran‐cox test.…”

“… 4–6 We found that weekly injections of LG emulsion containing sGTH were effective for inducing ovarian maturation in the Japanese eel. 5 The LG emulsion was thus expected to be effective for more than 1 week.…”

Skin lectin and the lymphoid tissues in the leptocephalus larvae of the Japanese eel Anguilla japonica

“…Eel is one of the most important fish species cultured in Japan. Although much effort has been directed to its breeding under artificial rearing conditions and in the laboratory of one of the authors, 14,15 such that fertilized eggs and preleptocephalous larvae can be obtained fairly constantly, there is still no success in cultivating the larval fish to adults ( i.e. culturing it to the leptocephalus stage has not yet been possible).…”