Abstract
Characterization of the feeding preferences of bivalve larvae would help improving the bivalve aquaculture and hatchery by providing appropriate microalgal diets. However, inaccurate and laborious identification and counting of microalgal species have challenged the selective feeding of bivalves. In the present study, we developed a highly specific and sensitive assay using quantitative polymerase chain reaction (qPCR) to assess the selective feeding of bivalve larvae based on species-specific primers targeting to microalgal 18S rDNA sequences. The assay exhibited good specificity. The detection limits of the qPCR assay were 769, 71, 781 and 21 18S rDNA copies for Chaetoceros calcitrans, Isochrysis galbana, Platymonas helgolandica and Nannochloropsis oculata, respectively. Using such assay, we found that C. calcitrans and I. galbana were preferentially ingested, whereas N. oculata was preferentially rejected in biodeposits of four bivalve species, Tegillarca gransa, Cyclina sinensis, Scapharca subcrenata and Sinonovacula constricta. Furthermore, our growth experiments revealed that C. calcitrans and I. galbana could significantly promote the shell growth, whereas feeding of N. oculata resulted in poorer growth of four bivalve species. These data indicated that qPCR might be useful in screening of efficient and reliable microalgal species for each bivalve species, leading to improved bivalve aquaculture and hatchery.
Highlights
Live microalgae are the fundamental food sources for bivalves [1,2,3]
Genomic DNA was extracted from C. calcitrans, I. galbana, P. helgolandica and N. oculata
About 300 bp of 18S rDNA PCR product was amplified from genomic DNA of C. calcitrans, I. galbana, P. helgolandica and N. oculata and sequenced (Fig 2)
Summary
Live microalgae are the fundamental food sources for bivalves [1,2,3]. Previous study has revealed that some bivalves can distinguish their food from various types of particles, preferentially ingesting the high-quality ones, while rejecting those undesirable such as pseudofeces [4]. It is important that the microalgae chosen as foods for bivalve aquaculture are preferentially ingested, and the characterization of feeding preferences of bivalves should help improving the bivalve aquaculture and hatchery by providing appropriate microalgal diets [5]. Several technologies have been developed to assess the feeding selection of bivalves, including particle counter, electronic particle counter and flow cytometry [4]. The first two methods are highly laborious and time-intensive, and do not accurately differentiate.
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