Fatty acid and sterol composition reveal food selectivity of juvenile ark shell Tegillarca granosa Linnaeus after feeding with mixed microalgae

Abstract

The successful care and breeding of intertidal shellfish is determined by the variety and quality of the microalgae used as feed. Practice has found obvious feeding selectivity in different intertidal shellfish for diet microalgae, so screening for microalgal species with high food value is a priority for research related to the culture of hatchery shellfish.In this work, the effects of four different microalgae, Chaetoceros calcitrans, Isochrysis galbana, Nannochloropsis oculata and Diacronema viridis, on the growth of juvenile ark shells (Tegillarca granosa Linnaeus) was studied. The microalgal diets were applied in three different types of treatments: a mixture of all four microalgae, single species, and binary combinations of C. calcitrans or I. galbana with the other individual species. The best feeding effects were observed with the mixture of all four microalgae, and binary algal diets were second best. When fed with single-species diets, the most favorable results were observed with C. calcitrans followed by I. galbana. Single-species diets of D. viridis or N. oculata were the least beneficial.Fatty acid and sterol compositions of the microalgae and juvenile ark shells were analyzed by gas chromatography–mass spectrometry (GC–MS) after feeding, and 32 fatty acids and 12 sterols were identified. The results of a principal components analysis (PCA) of the fatty acid and sterol compositions in juvenile ark shells, using the SIMCA-P+ software package, revealed that these contents were affected by their microalgal diets. In the PCA score scatter plots for the first and third components, the samples fed with the full mixture of microalgae were grouped near the samples fed with binary-species diets of C. calcitrans and I. galbana. The samples fed with binary-species diets of C. calcitrans and N. oculata or D. viridis were located near the samples fed with only C. calcitrans, and the samples fed with binary-species diets of I. galbana and N. oculata or D. viridis were near the samples fed with only I. galbana. The samples fed with only N. oculata or D. viridis were located far from the other samples. These results demonstrate that the lipid compositions of juveniles fed with binary-species diets were similar to those of the shells fed with single microalgae, which had a more favorable feeding effect on the shell. This study highlights the feeding selectivity of the shells, and the results shown in the PCA scatter plot based on the fatty acid and sterol compositions demonstrate that the high-quality microalgae candidates for use in hatchery culture can be selected by comparing samples fed with single and mixed microalgae. Statement of relevanceThis study demonstrated that the fatty acids and sterols of the shellfish were largely determined by its diet microalgae. Based on the characteristics of the lipid composition of the microalgae candidates, by using GC–MS and principal components analysis (PCA), a precise method can be applied in shellfish hatchery culture when screening the potential microalgal diets of high quality.