title: Optimizing dietary levels of menhaden and soybean oils and soybean lecithin for pre-gonadal somatic growth in juveniles of the sea urchinLytechinus variegatus.
abstract: Dietary lipids serve as important sources of energy and essential fatty acids for aquatic animals. Sources of animal and plant oils are increasingly limited as well as expensive, and dietary requirements associated with the inclusion of these oils must be carefully evaluated to facilitate sustainable and affordable formulations. In this study, we investigated quantities of menhaden oil (MO) with and without soybean lecithin or soybean oil (SO) to determine appropriate levels for optimal somatic growth for pre-gonadal juvenileLytechinus variegatus. We prepared semi-purified diets that varied in neutral lipid content (0, 2, 4, or 8% dry matter) and soy lecithin (0 or 2%) and exchanged lipids reciprocally with purified starch while holding constant all other nutrients. We maintained laboratory-reared juvenileL. variegatus(average initial wet weight 82 ± 0.7 mg, mean ± SE ,n= 9 treatment-1) in recirculating seawater systems and fed each daily a sub-satiation ration for five weeks. We assessed wet weights and test diameters every two weeks and at the end of the experiment (5 wk). Level of MO with or without soybean lecithin did not significantly affect wet weight gain; however, increasing levels of SO in the diet reduced wet weight gain and dry matter production efficiency and increased feed conversion ratio. Dry gut weight was positively correlated with level of MO. Lipid level in the gut increased with increasing dietary lipid level, regardless of source. These data suggest the composition of the SO is inhibitory for either nutrient absorption or metabolic processes associated with growth at this life stage. Diets containing total lipid levels of approximately 5 to 6% that include sources of n-3 fatty acids may support optimal growth for pre-gonadal juvenileL. variegatus.
authors.affiliation: Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, Alabama, 35294, USA.
authors.forename: Victoria K
authors.initials: VK
authors.lastname: Gibbs
authors.affiliation: Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, Alabama, 35294, USA.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Heflin
authors.affiliation: Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, Alabama, 35294, USA.
authors.forename: Warren T
authors.initials: WT
authors.lastname: Jones
authors.affiliation: Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, Alabama, 35294, USA.
authors.forename: Mickie L
authors.initials: ML
authors.lastname: Powell
authors.affiliation: Texas AgriLife Mariculture Research Laboratory, Texas A&M University System, 1300 Port Street, Port Aransas, Texas, 78373, USA.
authors.forename: Addison L
authors.initials: AL
authors.lastname: Lawrence
authors.affiliation: Department of Biostatistics, University of Alabama at Birmingham, 1665 University Boulevard, Birmingham, Alabama, 35294, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Makowsky
authors.affiliation: Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, Alabama, 35294, USA.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Watts
keywords: Lytechinus variegates; echinoid; fish oil; lipid; nutrition; production efficiency; soybean oil