Optimizing dietary levels of menhaden and soybean oils and soybean lecithin for pre-gonadal somatic growth in juveniles of the sea urchin Lytechinus 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 juvenile Lytechinus 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 juvenile L. 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 juvenile L. variegatus.

Effects of lipid sources on the growth performance, gonad development, fatty acid profile and transcription of related genes in juvenile sea urchin ( Strongylocentrotus intermedius )

“…Consistently, Gibbs et al. (2015) found that WGR of juvenile Lytechinus variegatus fed SO was reduced compared to that fed FO, and further reduced with the increasing amount of SO. However, the present study showed no significance in the digestive capacity in response to different lipid sources.…”

“…WGR of juvenile S. intermedius fed SO was lower than that fed LO and FO. Consistently,Gibbs et al (2015) found that WGR of F I G U R E 1 Transcription of fatty acid synthesis related genes in the intestine (a) and gonad (b) of juvenile sea urchin (Strongylocentrotus intermedius) in response to different lipid sources Transcription of major yolk protein (MYP) in the gonad and digestive tract of juvenile sea urchin (Strongylocentrotus intermedius) in response to different lipid sources Lytechinus variegatus fed SO was reduced compared to that fed FO, and further reduced with the increasing amount of SO.…”

Effects of dietary carbohydrate on weight gain and gonad production in small sea urchins,Lytechinus variegatus

“…; Gibbs et al . ). In the current study, carbohydrate levels were adjusted by covarying the levels of acid‐washed diatomaceous earth.…”

Inducers of settlement and metamorphosis of the shrimp Hippolyte inermis Leach in Posidonia oceanica

“…The presence of biofilms 18 and in particular, specific metabolites released by bacteria and protozoans, are important settlement 19 cues for larvae of sponges 20 and an effect of chemical cues (e.g., humic acids, volatile infochemicals, ammonia and various ions, dissolved gases, organic compounds) on various invertebrate larvae 4,13,21 was demonstrated. A nearly universal mechanism of settlement induction by bacterial cues has been proposed, able to strongly influence such different taxa of invertebrates as cnidarians 17,22 , bryozoans 23 , molluscs 16 , annelids 24 , echinoderms 19,25 , crustaceans 26 and even ascidians 27 . A non-polar metabolite extracted from bacteria (Tetrabromopyrrole) 28 is also responsible for partial or complete metamorphosis in coral planulae, which demonstrated a highly specific response to single infochemicals 29 .…”