Selective feeding of bay scallop Argopecten irradians on phytoplankton community revealed by HPLC analysis of phytopigments in Bohai Sea, China

Abstract

Understanding the feeding selectivity on phytoplankton by shellfish is currently a big challenge. In order to investigate the feeding behavior of bay scallop (Argopecten irradians) on phytoplankton, we compared its compositions of phytopigments in digestive glands with those in the surrounding seawater, and conducted five consecutive investigations between July and November 2016 in a bay scallop culture area along coast of Qinghuangdao City, northwest of the Bohai Sea, China. Phytopigments in four-size fractionated phytoplankton of seawater (micro- (20–200 µm); nano(L)-[10–20 µm]; nano(S)-[2.7–10 µm], and pico-[<2.7 µm]) and digestive glands of A. irradians were examined to investigate the selective feeding of A. irradians. Results show that fucoxanthin and peridinin constituted the major part of taxonomically diagnostic carotenoids (TDCs) in the micro- and nano(L)-phytoplankton in seawater. Compared with total phytoplankton biomass of seawater (TPB, sum of the four sizes), a substantial decrease of fucoxanthin proportion to total DCs in digestive glands was observed while that of peridinin, 19′-butanoyloxyfucoxanthin, alloxanthin and 19′-hexanoyloxy-fucoxanthin showed an obvious increase when those pigments were mainly confined to micro-sized phytoplankton (20–200 µm). However, zeaxanthin and prasinoxanthin were mainly confined to nano(s)- and pico-phytoplankton, of which the proportions in digestive glands were usually lower in TPB. The contribution of lutein to total DCs in digestive glands (with an average of 7.23%) increased compared with TPB of seawater (with an average of 0.63%) during all five sampling times.