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Phytoplankton composition is an important factor affecting the growth and physiological biochemical characteristics of filter-feeding bivalves. With the increasing trend in dinoflagellate biomass and blooms in mariculture areas, how the physio-biochemical traits and seafood quality of the mariculture organism are affected by the dinoflagellates, especially those at nonfatal levels, is not well understood. Different densities of two Karlodinium species, namely K. veneficum (KV) and K. zhouanum (KZ), mixed with high quality microalgal food Isochrysis galbana was applied in feeding manila clam Ruditapes philippinarum in a 14-day temporary culture, to comparatively study how the critical biochemical metabolites such as glycogen, free amino acids (FAAs), fatty acids (FAs), volatile organic compounds (VOCs) in the clam were affected. The survival rate of the clam showed dinoflagellate density and species specificity. The high-density KV group inhibited survival to 32% lower than that of the pure I. galbana control, respectively, while KZ at low concentrations did not significantly affect the survival compared with the control. In the high-density KV group, the glycogen and FAA contents decreased (p < 0.05), indicating that energy and protein metabolism were significantly affected. Amount of carnosine (49.91 ± 14.64 to 84.74 ± 8.59 μg/g of muscle wet weight) was detected in all the dinoflagellate-mixed groups, while it was not present in the field samples or in the pure I. galbana control, showing that carnosine participated in the anti-stress activities when the clam was exposed to the dinoflagellates. The global composition of FAs did not significantly vary among the groups. However, contents of the endogenous C 18 PUFA precursors linoleic acid and α-linolenic acid significantly decreased in the high-density KV group compared to all the other groups, indicating that high density of KV affected the metabolisms of fatty acids. From the results of the changed VOC composition, oxidation of fatty acids and degradation of free amino acids might occur in the clams exposed to dinoflagellates. The increased VOCs, such as aldehydes, and decreased 1-octen-3-ol probably produced a more fishy taste and reduced food flavor quality when the clam was exposed to the dinoflagellates. This present study demonstrated that the biochemical metabolism and seafood qulity of the clam were affected. However, KZ with moderate density in the feed seemed to be beneficial in aquaculture for increasing the content of carnosine, a high-valued substance with multiple bioactivities., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Background: Steryl glycosides (SGs) are sterol conjugates found in various plants, especially in those making up human diets. It has been demonstrated that SGs have potential health benefits, and they could be used as food supplements in a variety of food matrixes. Marine microalgae are a potential resource for human food and ingredients. In this study, gas chromatography-triple quadrupole mass spectrometry (GC-QQQ-MS) was used to characterize unknown SGs in eight microalgae belonging to different classes (Isochrysis galbana 3011, Pavlova viridis, Platymonas helgolandica, Conticribra weissflogii, Thalassiosira pseudonana, Nitzschia closterium, Gymnodinium sp., and Karlodinum veneficum)., Results: The SGs were first extracted from lyophilized algae with chloroform-methanol, purified by solid-phase extraction and analyzed as trimethylsilyl derivatives. Nine SGs have been identified. In particular, new SGs like occelasteryl glycoside and stellasteryl glycoside were found in Gymnodinium sp., 24-methylene cholesteryl glycoside was detected in P. helgolandica, and 4,24-dimethylcholestan-3-yl glycoside was identified as the main constituent of microalga K. veneficum. The results also showed that the compositions of SGs in different microalgae varied, with a range of 5.234 to 0.036 g kg -1 , and microalga P. viridis contained the most abundant SGs., Conclusion: GC-QQQ-MS is a powerful tool to detect SGs with different structures from a variety of microalgae. The compositions of SGs in different microalgae varied greatly. Microalgae are a good source of highly valued SGs. © 2017 Society of Chemical Industry., (© 2017 Society of Chemical Industry.)

Sphingolipid compositions are crucial for the structural and physiological properties of microalgae membranes. In the present study, we developed a quadrupole time-of-flight (Q-TOF) mass spectrometric method based on MS E data collection for the identification of sphingolipids with high efficiency, selectivity, sensitivity and mass accuracy and applied this method for precise structural identification and quantitative profiling of ceramides and glycosphingolipids in total lipid extracts from 17 strains of microalgae, including 11 strains of diatom, 3 strains of dinoflagellate and 3 strains of haptophyta. Using this method, four species of sphingolipids including 27 ceramides, 13 monosaccharide ceramides, 18 disaccharide ceramides and 18 trisaccharide ceramides were identified. The compositions of sphingolipid-included glycosyl moieties, long chain bases and N-acyl chains showed a significant difference among different microalgae categories. Some long chain bases including d19:2, d19:3 and d19:4, glycosyl moieties including disaccharide and trisaccharide, and N-acyl chains such as 14:0, 14:1, 24:0, 24:1, h18:1, h19:1 and h22:0-2 can be chosen as the molecular signature for microalgae from three major phyla. This methodology will be useful for a wide range of physiological and pathological studies of sphingolipids. Furthermore, the diversity of sphingolipid structure could provide a new criterion for microalgae chemotaxonomy., (Copyright © 2017. Published by Elsevier B.V.)

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.

Background: Head space solid-phase microextraction-gas chromatography-mass spectrometry has been applied to analyze the volatile components of six marine microalgae (Thalassiosira weissflogii, Nitzschia closterium, Chaetoceros calcitrans, Platymonas helgolandica, Nannochloropsis spp. and Dicrateria inornata) from Bacillariophyta, Chlorophyta and Chrysophyta, respectively, in different growth phases., Results: All volatile compounds were identified by database searching in the NIST08 Mass Spectral Library and analyzed by principal component analysis with SIMCA-P software (Umetrics, Umea, Sweden). The results clearly revealed that the volatile components of the six microalgae were significantly different in the exponential, stationary and declining phases. Aldehydes, alkanes, some esters and dimethyl sulfide significantly changed in different growth phases., Conclusion: This is the first report on the comprehensive characteristics of volatile components in different microalgae and in different growth phases. The results may provide reference data for studies on the flavor of cultivated aquatic organism, odor formation in nature water, choice of feeding period and microalgae species selection for the artificial rearing of marine organisms. © 2016 Society of Chemical Industry., (© 2016 Society of Chemical Industry.)

Rationale: Glycosphingolipids (GSLs) are important components of the cell membrane; however, little is known about GSLs in microalgae. We analyzed GSLs in three strains of Skeletonema microalgae by liquid chromatography coupled with mass spectrometry., Methods: Total lipid was extracted from Skeletonema microalgae. Separation of lipids was achieved via reversed-phase liquid chromatography, and mass spectrometric analysis of the lithium adduct of GSLs was conducted to determine their structures., Results: Two types of novel glycosphingolipids were identified from three strains of Skeletonema microalgae. The N-acyl groups were primarily long-chain saturated or monoenoic fatty acids (monounsaturated fatty acids) with 16C and 20 to 24C. The sphingoid long-chain bases (LCB) were sphingosine, sphingadienine and sphingatrienine. The saccharide polar head groups of glycosphingolipids were disaccharide (heptose-hexose) or trisaccharide (heptose-hexose-hexose). Semi-quantitative analysis of GLSs in the three strains of microalgae showed that GSL contents ranged from 0.09 to 8.79 nmol/mg dry microalgae powder., Conclusions: A qualitative method was developed for the identification of GSLs in microalgae. Two types of novel GSLs were identified from three strains of Skeletonema, which might have important biological functions. It could also provide a reliable tool for chemotaxonomy of microalgae., (Copyright © 2013 John Wiley & Sons, Ltd.)

A facile method based on liquid chromatography coupled with electrospray ionization tandem triple quadrupole mass spectrometry working in selected reaction monitoring mode has been established to analyze toxins in the algae and water samples. Twelve types of toxins (anatoxin, cylindrospermopsin, dinophysistoxin-1, nodularin, okadaic acid, microcystins) were efficiently separated under optimized liquid chromatography coupled with mass spectrometry conditions in the selected reaction monitoring mode. Correlation coefficients of the calibration curves, all felt in the range of 0.9958-0.9998, indicated good linearity. The detection limits of toxins in this method were all lower than 0.20 ng/mL and the quantification limits were in the range from 0.04 to 0.60 ng/mL. Except for anatoxin, cylindrospermopsin, and nodularin, the other toxins' recoveries varied from 55.45 to 140.85%. And the relative standard deviations of interday and intraday precision were at 8.61% (n = 5). The high-performance liquid chromatography (HPLC)/electrospray ionization (ESI)-mass spectrometery (MS) method was also successfully applied to analyze the algae and water samples. Owing to its exclusive selectivity and excellent sensitivity, the developed method is a tool for comprehensive analyses of the 12 types of toxins at nanogram levels., (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This study has investigated the effects of six different unialgal diets ( Chaetoceros calcitrans , Platymonas helgolandica , Chlorella sp., Isochrysis galbana , Nannochloropsis oculata , and Pavlova viridis ) on the composition of fatty acids and sterols in juvenile ark shell Tegillarca granosa Linnaeus. The best feeding effects on the growth of shellfish were found in C. calcitrans, followed by I. galbana and P. viridis, whereas Chlorella sp. and N. oculata exhibited relatively poor effects. The fatty acid and sterol compositions in the six microalgae and the juvenile ark shell after feeding were analyzed, and 39 fatty acids and 18 sterols were identified. Although the results demonstrate a close correlation between the sterol compositions in algal species and juvenile ark shell, a similar correlation was not observed between fatty acids. In the juvenile ark shell fed microalgae, the ratio of total saturated fatty acids (SFA) rapidly decreases, whereas the proportion of total polyunsaturated fatty acids (PUFAs) increases considerably. The abundances of AA, EPA, and DHA increase most significantly in shellfish with better growth (fed C. calcitrans, I. galbana, and P. viridis). The number of sterol species is reduced, but the total sterol content in groups fed corresponding microalgae increases, and abundant plant sterols, instead of cholesterol, are accumulated in juvenile ark shell fed appropriate microalgae I. galbana and P. viridis. Therefore, to be more conducive to human health, I. galbana and P. viridis, of the six experimental microalgae, are recommended for artificial ark shell culture.

The razor clam Sinonovacula constricta is the first marine mollusk demonstrated to possess the complete long-chain polyunsaturated fatty acids (LC-PUFA) biosynthetic pathway. This study explored the impact of different microalgae on growth, Fad and Elovl expressions, and fatty acid (FA) profiles in juvenile S. constricta. Results revealed that juveniles fed with Isochrysis galbana (rich in DHA) or Chaetoceros calcitrans (rich in EPA) consistently exhibited higher growth than those fed Chlorella sp. (rich in LA and ALA), underscoring the importance of dietary LC-PUFA in S. constricta's development. Expression of most Fad and Elovl in C. calcitrans and I. galbana-fed juveniles were initially up-regulated, then down-regulated, suggesting LC-PUFA demand for faster growth. Although Chlorella sp.-fed juveniles exhibited decreased mRNA levels for most genes, levels were notably higher lately compared to those fed C. calcitrans or I. galbana, hinting at potential LC-PUFA biosynthesis induction. FA profiles in S. constricta generally mirrored those in ingested microalgae, implying direct FA accumulation from diets. Some microalgal FA were absent in farmed S. constricta, while others emerged, indicating S. constricta's ability to selectively accumulate and synthesize FA. This study enhances the understanding of dietary FA metabolism in S. constricta, valuable for selecting appropriate microalgae in its farming practices. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Steryl glycosides (SGs) are sterol conjugates found in various plants, especially in those making up human diets. It has been demonstrated that SGs have potential health benefits, and they could be used as food supplements in a variety of food matrixes. Marine microalgae are a potential resource for human food and ingredients. In this study, gas chromatography–triple quadrupole mass spectrometry (GC–QQQ‐MS) was used to characterize unknown SGs in eight microalgae belonging to different classes (Isochrysis galbana 3011, Pavlova viridis, Platymonas helgolandica, Conticribra weissflogii, Thalassiosira pseudonana, Nitzschia closterium, Gymnodinium sp., and Karlodinum veneficum). RESULTS: The SGs were first extracted from lyophilized algae with chloroform–methanol, purified by solid‐phase extraction and analyzed as trimethylsilyl derivatives. Nine SGs have been identified. In particular, new SGs like occelasteryl glycoside and stellasteryl glycoside were found in Gymnodinium sp., 24‐methylene cholesteryl glycoside was detected in P. helgolandica, and 4,24‐dimethylcholestan‐3‐yl glycoside was identified as the main constituent of microalga K. veneficum. The results also showed that the compositions of SGs in different microalgae varied, with a range of 5.234 to 0.036 g kg−1, and microalga P. viridis contained the most abundant SGs. CONCLUSION: GC–QQQ‐MS is a powerful tool to detect SGs with different structures from a variety of microalgae. The compositions of SGs in different microalgae varied greatly. Microalgae are a good source of highly valued SGs. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Rationale Diacylgycerol- N-trimethylhomoserine (DGTS) and diacylglycerylhydroxymethyl- N,N,N-trimethyl-β-alanine (DGTA) are structural isomers that are the most commonly described betaine lipids in microalgae. The structural differentiation and precise identification of DGTS and DGTA in microalgae need to be established during mass spectrometry analysis. Methods Total lipid was extracted from Amphora spp. with CHCl3/CH3OH (1:1, v/v). The qualitative analysis of DGTS and DGTA in Amphora spp. was carried out using Li+/H+ dual mode by ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry operating in MSE mode (UPLC/QTOF MSE). Results Characteristic fragment ions [C10H22O5N]+ at m/z 236.15 and [C7H14O2N]+ at m/z 144.10 from the [M + H]+ precursor ion can be used for the qualitative analysis of both DGTA and DGTS, whereas the loss of m/z 87 and 74 from the [M + Li]+ precursor ion are specific for DGTS, and the loss of m/z 103 from the [M + Li]+ precursor ion is only for DGTA. As a result, 9 DGTSs and 16 DGTAs with different fatty acids were identified simultaneously in Amphora spp. Semi-quantitative analysis of DGTS and DGTA in Amphora spp. showed that the contents of DGTS ranged from 0.003 to 0.438 nmol mg-1 dw, and that of DGTA from 0.004 to 0.414 nmol mg-1 dw. Conclusions This is the first report to achieve the ambiguous structural identification of DGTS and DGTA by UPLC/QTOF MSE using dual Li+/H+ adduct ion mode, which has remained a challenge in the past. It could provide new insights into their phylogeny and be helpful to characterize the natural phytoplankton communities as intact polar lipid biomarkers. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Isochrysis galbana is a species of marine microalgae that is principally used to feed the larvae and early juveniles of bivalve mollusks (e.g., ark shells, clams, mussels, oysters and scallops). The artificial hatchery stages of most of these larvae are primarily occur during high-temperature seasons, when the water temperature in the breeding pool frequently exceeds 30 °C and even reaches 35 °C, which may change the lipid composition of I. galbana, thus affecting its nutritional value. In this experiment, we investigated changes in the lipid composition of I. galbana Parke at high temperature using ultra-performance liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry. The results showed that the sulfoquinovosyldiacylglycerol (SQDG), monogalactosyldiacylglycerol (MGDG), diacylglycerylcarboxyhydroxymethylcholine (DGCC) and digalactosyldiacylglycerol (DGDG) contents increased during growth at 20 and 35 °C. Conversely, the lyso-SQDG, lyso-MGDG, lyso-DGDG, lyso-DGCC and triacylglycerol (TAG) contents clearly decreased. Moreover, higher SQDG, MGDG, DGDG and DGCC contents and lower lyso-lipid and TAG contents were observed in I. galbana Parke grown at 35 versus 20 °C. In addition, the content of docosahexaenoic acid (DHA) improved at 20 and 35 °C during growth, and DHA accumulated to greater levels at 35 °C than at 20 °C at the same time points. These results revealed an increase in DHA content as the temperature rose, which indicated that the nutritional value of I. galbana Parke during logarithmic phase improved in the same cultured time with an increasing temperature. [ABSTRACT FROM AUTHOR]

The two morphologically similar microalgae NMBluh014 and NMBluh-X belong to two different strains of Nannochloropsis oceanica. They possess obviously different feeding effects on bivalves, but are indistinguishable by 18S rRNA and morphological features. In this work, lipidomic analysis followed by principal component analysis and orthogonal projections to latent structures discriminant analysis provided a clear distinction between these strains. Metabolites that definitively contribute to the classification were selected as potential biomarkers. The most important difference in polar lipids were sulfoquinovosyldiacylglycerol (containing 18:1/16:0 and 18:3/16:0) and monogalactosyldiacylglycerol (containing 18:3/16:3 and 20:5/14:0), which were detected only in NMBluh-X. Additionally, an exhaustive qualitative and quantitative profiling of the neutral lipid triacylglycerol ( TAG) in the two strains was carried out. The predominant species of TAG containing 16:1/16:1/16:1 acyl groups was detected only in NMBluh-X with a content of ~93.67 ± 11.85 nmol · mg−1 dry algae at the onset of stationary phase. Meanwhile, TAG containing 16:0/16:0/16:0 was the main TAG in NMBluh014 with a content of 40.25 ± 3.92 nmol · mg−1. These results provided the most straightforward evidence for differentiating the two species. The metabolomic profiling indicated that NMBluh-X underwent significant chemical and physiological changes during the growth process, whereas NMBluh014 did not show such noticeable time-dependent metabolite change. This study is the first using Ultra Performance Liquid Chromatography coupled with Electrospray ionization-Quadrupole-Time of Flight Mass Spectrometry (UPLC-Q-TOF-MS) for lipidomic profiling with multivariate statistical analysis to explore lipidomic differences of plesiomorphous microalgae. Our results demonstrate that lipidomic profiling is a valid chemotaxonomic tool in the study of microalgal systematics. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, we investigated the major lipid changes of six important diet microalgae (Chlorella sp., Nannochloropsis oculata, Nannochloropsis sp., Isochrysis galbana, Phaeodactylum tricornutum Bohlin and Chaetoceros calcitrans) during the entire growth phase using UPLC-Q-TOF MS system. Our results suggested that EPA/AA-rich lipids were largely detected in both Nannochloropsis sp. and N. oculata as a component of diacylglyceryl-N,N,N-trimethylhomoserine (DGTS). Moreover, docosahexaenoic acids (DHAs) were detected only in I. galbana mainly as a component of monogalactosyldiacylglycerol (MGDG) and sulphoquinovosyldiacylglycerol (SQDG). Besides, the growth phase of microalgae could be a useful variable for the content enrichment of EFA-rich lipids. A higher content EPA/AA-rich DGTS could be obtained at the end of stationary phase for Nannochloropsis sp. and N. oculata, and a higher content of DHA-rich lipids could be obtained at the end of stationary phase for I. galbana. However, EPA/AA-rich lipids were mainly detected in both P. tricornutum and C. calcitrans mainly as a component of TAG and MGDG, respectively. In addition, a higher content of EPA-rich TAG could be obtained at the end of the stationary phase for P. tricornutum. A higher content of EPA-rich MGDG could be obtained at the end of stationary phase for C. calcitrans. Taken together, considering the high EFA requirement for artificial rearing of marine organisms, Nannochloropsis sp., N. oculata, P. tricornutum, C. calcitrans and I. galbana would be highly recommended to be harvested at the end of the stationary phase. The distribution characteristics of EFA-rich lipids related to 6 microalgae are described in detail. [Copyright &y& Elsevier]

Bivalve lectins perform a crucial function in recognition of foreign particles, such as microalgae and pathogenic bacteria. In this study, a novel C-type lectin form Sinonovacula constricta (ScCL) was characterized. The full-length cDNA of ScCL was 1645 bp, encoding a predicted polypeptide of 273 amino acids with one typical carbohydrate-recognition domain. ScCL has the highest similarity and closest phylogenetic relationship with the C-type lectin from Solen grandis. Real-time PCR analysis showed that ScCL was expressed in all tested tissues, with the highest expression in the foot and the lowest expression in hemocytes. Agglutination activity of ScCL was Ca2+-independent. ScCL showed the strongest agglutination on Chlorella vulgaris , the modest agglutination on Platymonas subcordiformis , Nannochloropsis sp., and Thalassiosira pseudonana , the weakest agglutination on Chaetoceros sp., and no agglutination on Isochrysis zhanjiangensis. Meanwhile, agglutination tests and western blot analysis revealed that the recombinant ScCL protein could agglutinate Staphylococcus aureus and Vibrio harveyi , but could not agglutinate Vibrio anguillarum , Bacillus cereus , or Vibrio parahaemolyticus. Furthermore, ScCL had a high binding activity with LPS and mannose, a low binding activity with LTA, and no binding activity with PGN. The expression of ScCL in the gill of S. constricta fed with C. vulgaris and T. pseudonana was significantly increased at 1 and/or 3 h. After injection with S. aureus , the expression of ScCL in the gill was significantly increased at 3, 6, and 24 h. These results indicated that ScCL was involved in food particle recognition and immunity of S. constricta. • A novel C-type lectin from Sinonovacula constricta (ScCL) was characterized. • ScCL protein could bind to several PAMPs and bacteria. • ScCL protein could agglutinate several microalgae and bacteria in Ca2+-independent. • After feeding Chlorella vulgaris and Thalassiosira pseudonana , or after challenged with staphylococcus aureus , the expression of ScCL was up-regulated. • ScCL may be involved in food recognition and innate immunity. [ABSTRACT FROM AUTHOR]

Sinonovacula constricta is the first marine mollusc demonstrated to possess all fatty acyl desaturase (Fad) and elongase of very long chain fatty acids (Elovl) activities required for long-chain polyunsaturated fatty acids (LC-PUFA) biosynthesis via the Sprecher pathway, providing a good opportunity to investigate the essential fatty acids (FA) for its larval development. In the present study, we analyzed the Fad and Elovl expressions, FA compositions, and the feed effects of three representative microalgae (Chlorella sp. , Chaetoceros calcitrans and Isochrysis galbana) in S. constricta at early developmental stages. The results showed that S. constricta Fad and Elovl were all highly expressed in zygotes, which might occur from maternal transfer. Compared to transcripts of Elovl4 activity, Elovl2/5 was only expressed relatively high in zygotes, indicating that C ≥ 22 LC-PUFA were more important than C ≤ 20 LC-PUFA for S. constricta larval development. The zygotes accumulated abundant FA from parents, especially eicosapentaenoic acid (EPA), but with small amount of docosahexaenoic acid (DHA). Meanwhile, the trochophore larva fed with single or mixed microalgae with I. galbana (rich in DHA) exhibited significantly higher growth and survival rate compared to those fed with single Chlorella sp. (rich in 18:2n-6 and 18:3n-3) and C. calcitrans (rich in EPA) or both of them. Those findings suggested that the highly expressed Fad and Elovl might be largely responsible for DHA biosynthesis, but this capability was limited to meet the developmental requirement and the dietary DHA was necessary. Taken together, our results compellingly demonstrated that DHA was essential for S. constricta larval development, which is important to guide its breeding. • Fad and Elovl expressions were examined in developing S. constricta. • Fatty acid compositions were analyzed in developing S. constricta. • Trochophore larval growth and survival were evaluated by first-feeding diet. • DHA still appeared to be essential for S. constricta larval development. • Microalgae rich in EPA and DHA were critical for S. constricta breeding. [ABSTRACT FROM AUTHOR]

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 relevance This 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. [ABSTRACT FROM AUTHOR]