Lipid (energy) reserves, utilisation and provisioning during oocyte maturation and early embryonic development of deepwater chondrichthyans

We studied the lipid dynamics (lipid contents, classes and fatty acids) during oogenesis and early embryogenesis of 7 viviparous and 3 oviparous deepwater chondrichthyans. Mature pre-ovulated ovarian follicles of all species were high in lipid content, indicative of large energetic expenditure and high maternal investment. Larger lipid reserves were found in viviparous dogshark (28-36% wet weight, ww) compared to oviparous chimaeras (19- 24% ww) and catshark, F. boardmani (18% ww). Neutral lipids and monounsaturated fatty acids were the main source of lipidic energy during vitellogenesis and gestation. For most species, there was a peak in total lipid content, levels of storage lipids and essential fatty acids at time of ovulation. InterspeciWc variation of total lipid yolk reserves and lipid class proWles was largely explained by diVerences in parity mode, reproductive (continuous vs. non-continuous oocytes development) strategy and depth-related physiological adaptations. Fatty acid proWles were less variable among species with the most important fatty acids including: 16:0, 18:1w9, 20:1w9, 20:4w6 and 22:6w3. These Wndings provide a greater biochemical understanding of diVerent maternal-embryonic relationships among chondrichthyans, which can be used as a baseline for subsequent comparative studies.