Co-treatment with androgens during artificial induction of maturation in female eel, Anguilla anguilla: effects on egg production and early development

• Published in: Aquaculture
• Main Authors: Di Biase, Andrea, Lokman, P. Mark, GOVONI, NADIA, CASALINI, ANTONIO, EMMANUELE, PIETRO, PARMEGGIANI, ALBAMARIA, MORDENTI, OLIVIERO
• Other Authors: Govoni, Nadia, Casalini, Antonio, Emmanuele, Pietro, Parmeggiani, Albamaria, Mordenti, Oliviero
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: 17-Methyltestosterone; Androgen; Anguilla anguilla; Egg quality; Fertilization; Induced maturation
• Online Access: http://hdl.handle.net/11585/611450; https://doi.org/10.1016/j.aquaculture.2017.06.030; https://www.sciencedirect.com/science/article/abs/pii/S0044848616308821?via%3Dihub

Inclusion of sustained-release androgen implants into fertility treatment regimes of female freshwater eels has been proposed to benefit artificial maturation outcomes. This study sought to test whether co-administration of the androgen 17-methyltestosterone (17-MT) in combination with ‘traditional’ hypophysation of female European silver eels would affect egg quality and subsequent larval survival. Implants, containing 1 mg 17-methyltestosterone (17α-methyl-4-androsten-17β-ol-3-one in a matrix of cholesterol:cellulose = 95:5), were administered twice, at 1 and 5 weeks after onset of experimentation (MTA- and MTB-groups); control eels (Ctrl) were given a blank implant. Female eels received weekly injections with carp pituitary homogenates (CPH) from either Week 1 (MTA- and Ctrl groups) or Week 5 onwards (MTB-group). First 4 injections were made with 10 mg CPH/kg body weight (BW) in sterile physiological saline (0.9% NaCl); the subsequent 12 injections with 30 mg/kg CPH and thereafter, 40 mg/kg CPH was injected until fish were considered ready for induction of final maturation. Bi-weekly blood samples were collected (Day 0 onwards) and analyzed for levels of testosterone (T) and estradiol-17β (E2) by radioimmunoassay. After reaching maturity, fertilized eggs were obtained upon spontaneous spawning of co-housed breeders and egg performance (fertilization, hatching, survival rates) was recorded. No differences were observed between eels from the MTA- and MTB-groups; however, egg performance was notably better in eels treated with 17-MT + CPH compared to eels receiving CPH only, with hatching rates reaching mean values as high as around 70% for both 17-MT and CPH co-treated groups, but only averaging 21.0 ± 8.4% for eggs from the Ctrl-group. Furthermore, 17-MT treated eels displayed a more distinct pre-spawning peak for levels of plasma T and E2 and for body weight, the latter being indicative of increased batch fecundity. We conclude that androgen co-treatment holds promise for future development of eel captive ...