Lipid Composition and Utilization in Early Stage Leptocephalus Larvae of Bonefish (Albula vulpes)

Abstract

In order to encourage the survival of both captive and wild populations of bonefish (Albula vulpes), a deeper understanding of the species' early developmental characteristics is necessary. During ontogenesis, bonefish utilize lipids as a source of energy before the start of exogenous feeding. The goal of this study is to gain insight into the energetic needs of bonefish leptocephalus larvae in the post‐hatch larval stage. Broodstock were collected in the wild and hormone induced. Spawning yielded eggs that were fertilized and were then incubated until hatching. Larval development was monitored throughout the duration of the trial until all larvae perished. Samples of larval tissue were taken to the lab for lipid analysis and composition was compared at different developmental stages. Larval lipid composition was significantly different across sample groups showing a change in lipid content related to development. After hatching, larvae gradually depleted wax esters‐sterol ester (WE‐SE) reserves over a period of 4 days, while simultaneously increasing hydrocarbon (HC). The role of WE‐SE is seemingly tied to both buoyancy and energy reserves due to its high abundance immediately post‐hatch and selective catabolism. As larvae weaned off of the nutrition provided by the yolk, exogenous feeding began to diversify lipid composition and overall lipid reserves were depleted. Future directions included the development of optimal larval feeds based on this analysis in order to gain more insight into the nutritional needs and requirements during the critical leptocephalus stages.

A comprehensive biochemical characterization of settlement stage leptocephalus larvae of bonefish (Albula vulpes)

“…It is reasonable that WE-SE content is significantly lower in these late stage bonefish larval samples, as it is known that WE-SE reserves deplete over time during development due to its use in metabolic processes relating to growth (Glencross, 2009;Padr on et al, 1996). This is also supported by earlier findings by our group showing WE-SE as the main metabolite group during stages of development leading up to the settlement stage (Mejri et al, 2018(Mejri et al, , 2021.…”

“…Although prior studies have been conducted on the biochemical composition of other members of Elopomorpha, such as eels (Deibel et al, 2012) and other bonefish species (Mejri et al, 2018(Mejri et al, , 2021Padr on et al, 1996), this is the first study of this kind focused on A. vulpes. This study therefore provides an initial definition of the biochemical composition of settlement-stage A. vulpes that can be used for comparison with wild-caught larvae from other regions and can serve as guide for understanding the dietary requirements of leptocephali reared in aquaculture settings.…”

“…This study therefore provides an initial definition of the biochemical composition of settlement-stage A. vulpes that can be used for comparison with wild-caught larvae from other regions and can serve as guide for understanding the dietary requirements of leptocephali reared in aquaculture settings. This study primarily focused on defining lipid characteristics because it is known that lipids are the main metabolic driver in leptocephalus larvae (Bishop et al, 2000;Glencross, 2009;Mejri et al, 2021;Tocher, 2003).…”

“…The mean TAG:ST ratio (energy storage:cell structure ratio) was 0.2, which is close to that of other teleostean omnivores, suggesting a mixed diet (Carre on- et al, 2018). Prior studies regarding early bonefish development have determined that wild bonefish oocyte lipid class and fatty acids have high levels of wax esters/steryl esters at the beginning of embryonic and early larvae development (Mejri et al, 2018(Mejri et al, , 2019(Mejri et al, , 2021. It is reasonable that WE-SE content is significantly lower in these late stage bonefish larval samples, as it is known that WE-SE reserves deplete over time during development due to its use in metabolic processes relating to growth (Glencross, 2009;Padr on et al, 1996).…”

“…Studies regarding the influence of broodstock diets on spawn quality have demonstrated the direct effects of available nutrients in maternal diets on egg and larval survival and development (Mejri et al, 2018). Lipid profiles within eggs and larvae are important because at the embryonic and early larval stages, before the onset of exogenous feeding, young bonefish rely on lipid reserves for energetic and metabolic needs (Dahlgren et al, 2007;Mejri et al, 2018Mejri et al, , 2021. In the postmetamorphic settlement stage, leptocephali have limited lipid reserves and begin metabolizing complex structural carbohydrates called glycosaminoglycans (GAGs) as fuel for metabolism and cellular development (Bishop et al, 2000;Glencross, 2009).…”