Absorption of different macroalgae by sea cucumber Apostichopus japonicus (Selenka): Evidence from analyses of fatty acid profiles

Abstract

Fatty acids (FAs) were used as trophic markers to examine the absorption of different algae species, including brown alga Sargassum muticum (S), red alga Gracilaria lemaneiformis (G) and green alga Ulva lactuca (U) by sea cucumber Apostichopus japonicus. A 56-day feeding experiment was carried out to investigate the FA profile of the A. japonicus feeding on 6 different types of diets with the ingredient of either pure powder of single algae species or mixtures of 3 algae species, i.e., the mixtures (1:1) of S. muticum and G. lemaneiformis (SG), S. muticum and U. lactuca (SU), and G. lemaneiformis and U. lactuca (GU). The FA profile of A. japonicus showed obvious changes over the experimental period and was remarkably affected by the different diets. Analyses of variations in the specific FAs and the multidimensional scaling (MDS) ordination of the overall FA profiles revealed that A. japonicus preferentially absorbed U. lactuca relative to S. muticum in the diet group SU while showed the discrimination against G. lemaneiformis in the diet groups SG and GU. Moreover, A. japonicus fed with U. lactuca displayed a similar or higher specific growth rate (SGR) than those fed on S. muticum or G. lemaneiformis, respectively. The results of the present study suggested that green alga U. lactuca might be used as a suitable substitute for replacing the traditional ingredient brown alga Sargassum thunbergii in the artificial feed for A. japonicus farming. Statement of relevanceThe results of the present study could be used to further optimize the ingredient of A. japonicus artificial feeds.