Changes in milt volume and sperm quality with time after an injection of recombinant Japanese eel luteinizing hormone in male Japanese eels

Improvement of techniques for sperm evaluation and cryobanking in European eel.

“…On the other hand, new hormonal therapies using specific recombinant gonadotropins are being developed to induce spermiation in eel species. Although results in European eel has not been good enough for applying in aquaculture purposes (Peñaranda et al, 2018), recombinant Japanese eel LH induced a much higher amount of high-quality sperm when compared to hCG injections in this species (Ohta et al, 2017). In this context, studies into alternative hormonal treatments must be ongoing in order to improve current methods for inducing the successful artificial maturation of endangered species, such as the European eel.…”

Development of innovative methods for induction of European eel (Anguilla anguilla) spermatogenesis

“…In particular, both gonadotropins induced spermatogenesis until spermatozoa; however, only minor increases in GSI and no spermiation was seen (Kobayashi et al 2010). Full Japanese eel spermiation was recently achieved using injections of 500 µg/kg bodyweight recombinant Lh, produced by CHO cells (Ohta et al 2017), similar to the protocol described in Chapter 1. Ohta et al (2017) further hypothesized that a possible reason for the poor in vivo results of previous experiments may be a high metabolic clearance of protein with a non-vertebrate type of glycosylation (Ohta et al 2017).…”

“…Therefore, homologous recombinant gonadotropins in optimized concentrations might improve artificial eel maturation (Ohta et al 2017).…”

“…However, the reverse result of the aarLhtreatment (with no aarFsh injection) was more surprising. In particular, because hCG (an Lh-analog; Pérez et al 2000), goldfish recombinant Lh (Hayakawa et al 2008b) and Japanese eel recombinant Lh (Ohta et al 2017) can induce full spermatogenesis in Japanese eels. Potentially, higher hormone dosages could improve sperm quality in our study (Chapter 1) in general, and especially in the case of our aarLh-treatment, potentially to account for the longer half-life of hCG in circulation (Ohta and Tanaka 1997).…”

“…Higher LH dosages have been used with better results in Japanese eel e.g. Kobayashi et al (2010) used 2000 µg/kg and Ohta et al (2017) used 500 µg/kg recombinant Lh, the latter example being a ~20 fold dosage compared to our aarLh-treatment (22.2 µg/kg; Chapter 1). This difference in concentration might explain why our aarLh-treatment only induced spermatogenesis to the pre-meiosis spermatogonial proliferation stage (Chapter 1), despite elevated steroid levels.…”