Differential impacts of carp and salmon pituitary extracts on induced oogenesis, egg quality, molecular ontogeny and embryonic developmental competence in European eel

The differences in offspring production and performance reported in this study show that pituitary extracts composition impacts egg quality and embryogenesis and in particular, the transition from initial maternal transcripts to zygotic transcription

Johanna S. Kottmann; Michelle G. P. Jørgensen; Francesca Bertolini; Adrian Loh; Jonna Tomkiewicz

2020

Scholarcy highlights

  • The aquaculture sector has expanded rapidly and further development relies on diversification and on closing the life cycle for aquatic species in captivity
  • While the influence of maternal nutrition and egg nutrient composition on offspring quality is well established, studies of embryogenesis continue to uncover vital functions of different cytoplasmic factors such as messenger RNAs that are incorporated into the developing oocyte. These maternal mRNA transcripts deposited into the egg during oocyte development have proven to be essential drivers of zygotic and early embryonic development until the mid-blastula transition
  • Studies of molecular ontogeny during early embryogenesis have documented a tight relationship between the abundance of specific maternal mRNA transcripts, egg quality, and embryonic developmental competence
  • Captive offspring production requires assisted reproduction protocols, with administration of exogenous gonadotropins to induce sexual maturation and sustain gamete development. While such assisted reproduction protocols have led to stable production of viable eggs and larvae reaching the first-feeding stage for European eel, and production of glass eels for the Japanese eel, shortcomings in egg quality and offspring survival persist with a major bottleneck during the embryonic development
  • For female eels, assisted reproduction protocols commonly use pituitary extracts from carp or salmon as source of follicle stimulating hormone and luteinizing hormone to induce vitellogenesis, while follicular maturation is completed by administration of a maturation-inducing steroid, e.g. 17α,20ß-dihydroxy-4-pregnen-3-one
  • We compared the effects of constant dose treatment schemes on reproductive parameters including egg characteristics, fertilization success, occurrence of cleavage abnormalities, embryonic survival, and hatch success in a standardized experimental design
  • The effects of hormonal treatment on initial length, initial weight, time until spawning, oil droplet stage at priming and at DHP stage, weight increase of females, stripped eggs, floating eggs, dry-weight of unfertilized eggs, fertilization success, cleavage abnormalities and hatch success were tested using student t-tests

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