Chaetoceros Muelleri Research Articles

Characterization of exogenous lactate addition on the growth, photosynthetic performance, and biochemical composition of four bait microalgae strains.

To quickly obtain the biomass of bait microalgae with high value-added products, researchers have examined the influence of biochemical and environmental factors on the growth rates and biochemical composition of microalgae. Previous studies have shown that lactate plays an important role in metabolic regulation in Phaeodactylum tricornutum. In this study, we investigated the effect of exogenous lactate on the growth rates, photosynthetic efficiency, and biochemical composition of four commonly used bait microalgae in aquaculture. The optical density of the algal cultures at specific time points, YII, Fv/Fm, and the total lipid, protein, soluble sugar, insoluble sugar, chlorophyll a, and carotenoid content of P. tricornutum, Isochrysis galbana (I. galbana), Chaetoceros muelleri, and Cylindrotheca fusiformis were determined. In I. galbana, the growth rate was enhanced with the addition of lactate, even though higher concentrations of lactate were associated with a decrease in YII and Fv/Fm. In general, the total lipid content of these microalgal strains increased gradually in a concentration-dependent manner over the range of lactate concentrations. In addition, higher concentrations of lactate also induced significant changes in the total soluble and insoluble sugar levels in all microalgal strains. However, chlorophyll a and carotenoid contents increased at lower but decreased at higher concentrations of lactate in all microalgal strains. The total protein content was significantly elevated at all concentrations of lactate in P. tricornutum, whereas there were no significant differences in that of C. fusiformis. Lactate effective influences in the growth, metabolism, and synthesis of important biochemical components in the four microalgal strains under investigation.

Artificial spawning, hatchery and culture of the tropical sea cucumber (Holothuria leucospilota) using non-living food

Artificial breeding and farming of sea cucumber is considered as a sustainable way to meet market demand and minimize the pressure on wild populations. This study reports a method for large-scale artificial spawning, hatchery and culture of the tropical sea cucumber (Holothuria leucospilota). Spawning induction was performed by constant stimulation and dry shock. Both methods could obtain active and healthy fertilized eggs, but constant stimulation could get a greater oviposition amount of H. leucospilota. Among the six tested non-living food, the Spirulina platensis meal contains the highest contents of crude protein and total amino acids, and the Chlorella pyrenoidosa powder contains most abundant types of fatty acid. However, only the C. pyrenoidosa powder fed larvae could successfully develop to doliolaria stage. H. leucospilota fed C. pyrenoidosa powder had similar (P > 0.05) growth rate and survival rate but higher (P < 0.05) metamorphosis rate than that fed living Chaetoceros muelleri. The contents of crude protein and total amino acids of Saccharomyces cerevisiae yeast meal between that of C. muelleri and C. pyrenoidosa powder, but it failed to induce larval metamorphosis. The best diet scheme was mixing C. pyrenoidosa powder, S. cerevisiae yeast powder and sea mud followed by the ratio of 2:1:2 with the installment feeding mode, which reached the highest development rate of H. leucospilota. In summary, a simple and successful technology for large-scale artificial reproduction of H. leucospilota is set up in this study, which not only provide an excellent candidate for aquaculture in tropical regions, but also conducive to recover and reconstruct the wild population of sea cucumber.

Effects of Marine Microalgae on the Developmental Growth of the Sea Urchin Larviculture Anthocidaris crassipina

The sea urchin is a very important aquatic economic organism in many countries and has high food value. However, it has recently been heavily fished, and it would be of great importance to the sustainable development of coral reefs to develop large-scale aquaculture of sea urchins. Sea urchins are prone to death during larval development. Therefore, in this study, three kinds of microalgae were used as the initial food for sea urchins to evaluate whether different kinds of microalgae can improve their survival and growth rates. Chaetoceros muelleri (C), Isochrysis galbana tml (I), and Dunaliella salina (D) were fed to A. crassipina at concentrations of 5000, 10,000, 20,000, and 30,000 cell mL−1. A fasted group was used as control (N). The final body length, final body width, final stomach length, rudiment length, survival rate and morphology were measured to evaluate development and growth. The results showed that feeding with C. muelleri resulted in better growth and survival. After 9 days of feeding with C(20,000 cells mL−1), the rudiment length reached 203.33 ± 12.47 µm. The onset of metamorphosis was observed 12 days post-feeding. The survival rate after feeding C was also significantly higher than that after feeding I and D. In summary, when sea urchins are breeding, it is recommended to choose C(20,000 cells mL−1) or C(30,000 cells mL−1) as the initial feed for larvae to increase the growth and survival of sea urchin seedlings.

Contrasting benthic ecological functions in deep-sea canyon and non-canyon habitats: Macrofaunal diversity and nutrient cycling

Understanding ecosystem functioning and stability of continental slope environments requires assessing the effects of habitat heterogeneity (canyon and non-canyon habitats) on benthic macrofaunal communities and ecosystem functioning. We evaluated the importance of habitat heterogeneity and phytodetrital enrichment in canyon, channel, and inter-canyon habitats of the Gulf of Maine, Northwest Atlantic. Using an ROV, we collected sediment cores at five seafloor sites in the Gulf of Maine (663–969 m depth). Over ∼24 h, we incubated ∼6 cores per site, three of which were enriched with the diatom Chaetoceros muelleri. For all core treatments, we measured macrofaunal composition, functional diversity indices (functional richness, evenness, and divergence), and benthic nutrient fluxes (ammonium, nitrate, phosphate, and silicate), as well as oxygen consumption. We also dedicated two non-incubated cores to quantifying sedimentary and chemical-physical characteristics. We found that benthic communities differed among the three habitats, but these differences and our phytodetrital additions did not translate to significant differences in rates of benthic fluxes among habitats., expect for nitrate and phosphate fluxes. Total organic carbon and chlorophyll-a explained most of the variation in oxygen consumption, which was similar in enriched and control cores. We conclude that large-scale habitat heterogeneity contributes to variation in benthic community composition, but with no consistent effect on nutrient fluxes. These results also suggest that phytodetrital deposition influences oxygen consumption but plays a lesser role in short-term nutrient cycling in deep-sea heterogeneous habitats, perhaps masked by other environmental variables. Moreover, sediments with high functional richness and relatively high functional divergence may sometimes lack the specific trait types that rapidly enhance nutrient regeneration and thus contribute to ecosystem functioning of deep-sea sediments.

CRISPR/Cas9-Mediated Genome Editing via Homologous Recombination in a Centric Diatom Chaetoceros muelleri

Chaetoceros, the most abundant genus of marine planktonic diatoms, can be used in mariculture. An effective genetic transformation system with a short transformation period was established in Chaetoceros muelleri by electroporation in our previous study. In this study, a sequence-specific clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 vector applicable for C. muelleri was constructed, and the expressions of sgRNA, resistance gene, and Cas9 gene were driven by the endogenous promoters U6, acetyl-CoA acetyltransferase, and fucoxanthin chlorophyll a/c binding protein, respectively, in the vector. Nitrate reductase (NR) and urease (URE) genes were edited in C. muelleri, and the NR knockout and NR/URE double-knockout lines displayed the strict auxotrophic phenotype. In addition, the DNA double-strand break was repaired by homologous recombination when a donor DNA was introduced. CRISPR/Cas9 technology was successfully applied to C. muelleri with an editing efficiency of up to 86%, providing a molecular tool for the study of basic biology in C. muelleri and its synthetic biology applications.

Integrative effects of morphology, silicification, and light on diatom vertical movements.

Diatoms represent the most abundant and diversified class of primary producers in present oceans; their distinctive trait is the ability to incorporate silicic acid in a silica outer shell called frustule. Numerous adaptative functions are ascribed to frustules, including the control of vertical movements through the water column; this indirectly determines cell access to fundamental resources such as light and nutrients, and favors diatom escape from predators. At the same time, light guides phototroph movements in the water column by affecting cell density (e.g., by modulating Si deposition in diatoms, vacuole volume, and/or solution). We investigated how the tremendous diversity in morphology and silicification that characterizes the frustule and the crucial role of light in diatom spatial distribution govern diatom sinking capacity. To test their integrative effects, we acclimated four diatoms distinguished by frustule traits (Chaetoceros muelleri, Conticribra weissflogii, Phaeodactylum tricornutum, and Cylindrotheca fusiformis) to different light conditions and evaluated their physiological performance in terms of growth, elemental composition, morphological changes, and their in vivo sinking capacity. What emerged from this study was that silicification, more than other morphological characteristics, controls species vertical movements, while a higher energy availability enhances cell floating independently from the silica content.

The effects of light intensity and nitrogen concentration to enhance lipid production in four tropical microalgae

The manipulation of nutritional and culture parameters is one of the most promising methods for enhancing microalgal biomass and biofuel production. An earlier study analysed the ability of eight locally isolated microalgae to utilize standard nutrient sources in culture media to produce lipids. Four microalgae, Ankistrodesmus falcatus, Chlorella emersonii, Chaetoceros muelleri, and Isochrysis galbana, showed the desired biofuel properties (lipid/mass productivity, lipid content, and fatty acid profiles) and were selected for the present study. In this study, light intensity and nitrogen concentration were optimised to increase the growth rate, biomass, and lipid content of the four selected microalgae. Under optimal conditions of 135 μmol/m2/s light intensity and 5 g/l nitrogen, the isolates exhibited biomass productivity of 0.31–0.56 g/l/day, lipid content of 20.30–40.95% dry weight, and lipid productivity of 85.26–180.18 mg/l/day. Using the optimised parameters, the microalgae was further cultured with an upscaled volume of 5 L. The study found that C. muelleri and I. galbana produced the most promising results, with the highest lipid content, up to 43.40% dry weight, and the desired fatty acid profiles, which included a high concentration of saturated fatty acids (43.89–48.00%) and monounsaturated fatty acids (35.30–38.44%). Regardless, C. muelleri was chosen as a promising candidate for biodiesel application because of its high oleic acid proportion (27.68%), which was significantly higher than the other three microalgae (only 2.37–3.62% oleic acid). The study demonstrates the potential use of the tropical marine microalga C. muelleri as a feedstock for the production of biofuels.

Application of 1H HR-MAS NMR-Based Metabolite Fingerprinting of Marine Microalgae

Natural products from the marine environment as well as microalgae, have been known for the complexity of the metabolites they produce due to their adaptability to different environmental conditions, which has been an inexhaustible source of several bioactive properties, such as antioxidant, anti-tumor, and antimicrobial. This study aims to characterize the main metabolites of three species of microalgae (Nannochloropsis oceanica, Chaetoceros muelleri, and Conticribra weissflogii), which have important applications in the biofuel and nutrition industries, by 1H High-resolution magic angle spinning nuclear magnetic resonance (1H HR-MAS NMR), a method which is non-destructive, is highly reproducible, and requires minimal sample preparation. Even though the three species were found in the same ecosystem and a superior production of lipid compounds was observed, important differences were identified in relation to the production of specialized metabolites. These distinct properties favor the use of these compounds as leaders in the development of new bioactive compounds, especially against environmental, human, and animal pathogens (One Health), and demonstrate their potential in the development of alternatives for aquaculture.

APLIKASI PAKAN ALAMI DAN BUATAN PADA PEMELIHARAAN LARVA UDANG VANNAME (Litopenaeus vannamei) DI HATCHERY PT. SURI TANI PEMUKA UNIT HATCHERY NEGARA, BALI

This study aims to determine the application of live and artificial feed in the rearing of vanname shrimp larvae (Litopenaeus vannamei). The work consists of preparation of rearing media, nauplii stocking, feed management and monitoring of larval rearing. A total of 2,000,000 nauplii were used and reared in concrete tanks with a water volume capacity of 14 tons equipped with a filtration system and water changes carried out by flowtrough and circulation. The feed used consisted of livel feed including Chaetoceros muelleri, Thalassiosira sp and Artemia sp. and also artificial feed (commercial feed). The results showed that the application of live and artificial feed during larval rearing was positively correlated with larval stadia development and larval survival rate. Larval development in each stadia, including zoea, mysis and post larvae, showed normal development. The total larval population at each stadia decreased with a final mortality value of 40%. Nevertheless, the survival rate until the end of the PL-10 rearing period was observed to be 60% and this condition was in optimal condition

Sulfated Polysaccharides from Chaetoceros muelleri: Macromolecular Characteristics and Bioactive Properties.

Simple SummaryAlgae are an important source of bioactive compounds. The interest in microalgae is increasing due to their high-value products and the advantage of biomass cultivation under controlled conditions. Polysaccharides are released by algae and microalgae species and have been reported to have bioactivities found beneficial to human health. Despite the recognized importance of these organisms, the structure of polysaccharides in microalgae has been practically unexplored in contrast to that of macroalgae. Only a few microalgae polysaccharide structures have been solved due to the difficulties in the extraction of pure samples and the complexity of their chemical structures. Reports emphasize how the molecular weight, the content of sulfate groups, and the negative charge may be responsible for their multiple bioactivities. To better understand the uses and potential applications of extracellular polysaccharides, it is necessary to know their structure and physicochemical properties, which include molecular weight and chain conformation, since they are decisive in their biochemical behavior.In the present study, a culture of Chaetoceros muelleri, a cosmopolitan planktonic diatom microalga present in the Sea of Cortez, was established under controlled laboratory conditions. A sulfated polysaccharide (CMSP) extraction was carried out from the biomass obtained, resulting in a yield of 2.2% (w/w of dry biomass). The CMSP sample was analyzed by Fourier transform infrared spectroscopy, showing bands ranging from 3405 to 590 cm−1 and a sulfate substitution degree of 0.10. Scanning electron microscopy with elemental analysis revealed that the CMSP particles are irregularly shaped with non-acute angles and contain sulfur. High-performance liquid chromatography coupled to a dynamic light-scattering detector yielded molecular weight (Mw), polydispersity index (PDI), intrinsic viscosity [η], and hydrodynamic radius (Rh) values of 4.13 kDa, 2.0, 4.68 mL/g, and 1.3 nm, respectively, for the CMSP. This polysaccharide did not present cytotoxicity in CCD-841 colon cells. The antioxidant activity and the glycemic index of the CMSP were 23% and 49, respectively, which gives this molecule an added value by keeping low glycemic levels and exerting antioxidant activity simultaneously.

Effects of Diet on Larval Survival, Growth, and Development of the Sea Cucumber Holothuria leucospilota.

Because most tropical sea cucumbers have been overexploited around the world, the sea cucumber Holothuria leucospilota has become increasingly commercially important in recent years. Restocking and aquaculture of H. leucospilota using hatchery-produced seeds could both enhance declining wild populations and provide sufficient beche-de-mer product to satisfy increasing market demand. Identifying an appropriate diet is important for successful hatchery culture of the H. leucospilota. In this study, we trialed different ratios of microalgae Chaetoceros muelleri (2.00-2.50 × 106 cells/mL) and yeast (Saccharomyces cerevisiae, ~2.00 × 106 cells/mL) in diets for H. leucospilota larvae (6 d after fertilization, referred to as "day 0") at proportions 4 : 0, 3 : 1, 2 : 2, 1 : 3, and 0 : 4 by volume, in 5 treatments (A, B, C, D, and E, respectively). Larval survival rates in these treatments decreased over time, with the survival highest in treatment B (59.24 ± 2.49%) on day 15 (double that of the lowest rate in treatment E (28.47 ± 4.23%)). For any sampling event, larval body length in treatment A was always the lowest after day 3, and that for treatment B was always the highest, except on day 15. The maximum percentage of doliolaria larvae occurred in treatment B (23.33%) on day 15, followed by treatments C, D, and E (20.00%, 10.00%, and 6.67%, respectively). No doliolaria larvae occurred in treatment A, and pentactula larvae occurred only in treatment B (3.33%). On day 15 in all treatments, late auricularia larvae had hyaline spheres, but these were not prominent in treatment A. Densities of juveniles attaching to settlement plates varied with treatments, and the values were very low for the larvae only fed microalgae (A, 2.39 ± 1.95 ind per plate) or yeast (E, 2.13 ± 1.05 ind per plate)-only ~5% of the maximum number settling in treatment B (45.56 ± 7.24 ind per plate). Increased larval growth, survival and development, and juvenile attachment indicates that diets combining microalgae and yeast are more nutritionally balanced than single diets for hatchery of H. leucospilota. A combined diet of C. muelleri and S. cerevisiae at a 3 : 1 ratio is optimum for the larvae. Based on our results, we propose a larval rearing protocol to facilitate mass production of H. leucospilota.

Effect of feeding different types of β-glucans derived from two marine diatoms (Chaetoceros muelleri and Thalassiosira weissflogii) on growth performance and immunity of banana shrimp (Penaeus merguiensis)

β-glucans are produced by many organisms and could be used as supplementary feed to enhance immunity and growth in some aquatic animals. This study aimed to compare the effectiveness of β-glucans derived from two marine diatoms (Chaetoceros muelleri and Thalassiosira weissflogii) as growth promoters and immunity enhancers in banana shrimp (Penaeus merguiensis). Shrimp were divided into 3 groups: the control group was fed without β-glucan; the second and the third group were fed with 2 g kg−1 of β-glucan derived from C. muelleri and T. weissflogii, respectively. Shrimp were fed over a 30-day period to determine growth performance (final weight, weight gain, average daily gain (ADG), and feed conversion ratio (FCR)) at day 15 and day 30, respectively. The immune parameters determined were total hemocyte count (THC), phenoloxidase activity (PO) and immune gene expression. Survival rates were measured after 14 days of the feeding trial and Vibrio parahaemolyticus infection (6, 24, 48 h post infection). There was no significant difference (P > 0.05) for growth stimulation of shrimps between the two types of β-glucans (C. muelleri or T. weissflogii). Notably, shrimps fed with β-glucans had a higher final weight, weight gain, and ADG (P < 0.05) than shrimps fed with the control diet, while FCR of shrimps fed with both β-glucans was lower when compared to the control diet. Immune parameters, THC, PO, and gene expression of anti-lipopolysaccharide factor (ALF) and crustin were significantly higher (P < 0.05) in shrimps fed with β-glucans, especially with β-glucans from C. muelleri than the control group both before and after V. parahaemolyticus infection. Expression of penaeidin 3 and peroxiredoxin genes was significantly higher in shrimps fed with β-glucans after bacterial infection. Histopathology of hepatopancreas revealed an increase in blasenzellen hepatopancreatic epithelial cells (B cells) after 14 days of feeding which remained higher following infection with V. parahaemolyticus. The survival rate of shrimps fed with the diet containing β-glucan derived from either C. muelleri (82.2%) or T. weissflogii (77.8%) after V. parahaemolyticus infection was significantly higher than for the control group (51.1%) (P < 0.05). In conclusion, we propose that feeding banana shrimps with β-glucans derived from marine diatoms either C. muelleri or T. weissflogii at a 2 g kg−1 diet can significantly improve their growth performance and immunity.

Evaluation of suitable micro‐algal diets for intensive culture of the calanoid copepod Acartia bilobata

Copepods are alternative live feed in marine fish hatcheries, and the quality and type of micro-algal diets influence their culture productivity. Three algal species of different groups including prymnesiophyte: Isochrysis galbana (Iso), the diatom: Chaetoceros muelleri (Cht) and eustigmatophyte: Nannochloropsis occulata (Nan) were fed to the calanoid copepod Acartia bilobata. Selected algae were offered as mono-algal diets: T1-Iso, T2-Cht and T3-Nan or as mixed algal diets: T4-Nan + Cht, T5-Nan + Iso, T6-Iso + Cht and T7-Iso + Cht + Nan. Reproductive parameters, egg production, hatching success, nauplii and copepodite survival, development and first maturity, were closely monitored. Results illustrated that I. galbana was the most suitable diet for this copepod species, supporting higher average relative egg production (5631.62 ± 133.49 egg L−1 day−1), hatching success (96.32 ± 1.40%) and superior adult survival (44.44 ± 3.20%). Different algal diets influenced the nauplii and copepodite survival rate. Maximum survival to adults (56.67 ± 3.78%) and shortened development time (5.75 ± 0.12 days) and time to first maturity (4.50 ± 0.12 days) were observed when fed with I. galbana. The groups fed with C. muelleri exhibited lower survival (6.67 ± 0.67%) during development into adults, and the group fed with N. occulata alone or with C. muelleri did not survived till the adults. Amongst seven algal diets tested, I. galbana was found ideal for maximizing culture productivity, and hence recommended for intensive culture of A. bilobata.

Perbedaan konsentrasi nitrat dan intensitas cahaya terhadap laju pertumbuhan diatom Chaetoceros muelleri

Microalgae are cultured as natural feed for the cultivation of mollusks, crustaceans (early larval stages), and zooplankton. Diatoms are phytoplankton groups commonly used as feed, one of which is Chaetoceros muelleri. This study aims to identify the optimal nitrate concentrations and light level (irradiance) for the growth rate of C. muelleri. Culture was placed in nitrate 1,330; 5,305; and 27,030 mg/L (N1, N2, N3, respectively); and light 50, 100, and 150 µmol/m2/s, with three replications for each treatment. The response variable observed was the growth rate of C. muelleri and nitrate uptake. Each nitrate treatment resulted in a significant difference in the growth rate of C. muelleri (LSD, p &lt; 0.01). The N3 treatment produced the highest growth rate (average 0,188-0,193 cells/day), while N1 produced the lowest specific growth rate (average 0,149-0,157 /day). In light treatment, a significant difference was only seen in the light level of 150 µmol/m2/s (LSD, p &lt; 0.05) which produced the highest growth rate (average 0.157-0.193 cells/day), especially in the nitrate N1 and N2. Meanwhile based on the significance test, the interaction between nitrate and light treatment was not significant.Keywords: Chaetoceros muelleri; Growth rate; Irradiance; Nitrate

Variation of nitrate concentration and light level on growth rate of diatom Chaetoceros muelleri

Microalgae are cultured as natural feed for the cultivation of mollusks, crustaceans (early larval stages), and zooplankton. Diatoms are phytoplankton groups commonly used as feed, one of which is Chaetoceros muelleri. This study aims to identify the optimal nitrate concentrations and light level (irradiance) for the growth rate of C. muelleri. Culture was placed in nitrate 1,330; 5,305; and 27,030 mg/L (N1, N2, N3, respectively); and light 50, 100, and 150 µmol/m2/s, with three replications for each treatment. The response variable observed was the growth rate of C. muelleri and nitrate uptake. Each nitrate treatment resulted in a significant difference in the growth rate of C. muelleri (LSD, p &lt; 0.01). The N3 treatment produced the highest growth rate (average 0,188-0,193 cells/day), while N1 produced the lowest specific growth rate (average 0,149-0,157 /day). In light treatment, a significant difference was only seen in the light levelof 150 µmol/m2/s (LSD, p &lt; 0.05) which produced the highest growth rate (average 0.157-0.193 cells/day), especially in the nitrate N1 and N2. Meanwhile based on the significance test, the interaction between nitrate and light treatment was not significant.Keywords: Chaetoceros muelleri; Growth rate; Irradiance; Nitrate

Comparative Effects of Microalgal Species on Growth, Feeding, and Metabolism of Pearl Oysters, Pinctada fucata martensii and Pinctada maxima

Pinctada fucata martensii and P. maxima are two main traditional pearl oyster species that can produce seawater pearls. Our previous study showed a higher clearance rate (CR) and growth performance in P. f. martensii than in P. maxima fed with Isochrysis galbana. In this study, the P. f. martensii and P. maxima juveniles of two sizes (large and small) were fed with six different microalgae diets [I. galbana (I), Platymonas subcordiformis (P), Chaetoceros muelleri I, I+P, I+C, and P+C] to evaluate the differences in growth, feeding, and metabolism between two pearl oyster species. After 60 d of the rearing period, P. f. martensii and P. maxima fed with mixed microalgae showed a significantly higher relative growth rate (RGR) than those fed with single microalgae (P&amp;lt; 0.05). The RGRs were significantly higher in P. f. martensii than those in P. maxima fed with the same diets (P&amp;lt; 0.05). The RGRs showed a decreasing tendency with the growth in both pearl oyster species. The CRs of pearl oysters fed with mixed microalgae were significantly higher than those fed with single microalgae (P&amp;lt; 0.05), and the CRs of P. f. martensii were significantly higher than those of P. maxima fed with the same diets (P&amp;lt; 0.05). Significantly lower respiration rates (RRs) were observed in small-size P. f. martensii groups fed with I, P, and I+P diets and all large P. f. martensii groups compared to P. maxima fed with the same diets (P&amp;lt; 0.05). Higher activities of amylase, cellulase, lipase, and pepsin in P. f. martensiiwere observed compared to P. maxima fed with the same diets at two sizes. The pepsin activities in P. maxima decreased with the growth, while there were no consistent pepsin activities of P. f. martensii with the growth. The carbonic anhydrase activities in P. maxima were significantly higher than those in P. f. martensii fed with the same diets (P&amp;lt; 0.05). The carbonic anhydrase activities were highest in the I+C diet group, followed by C+P and I+P, I, C, and P groups. Significant differences were observed among different diet groups in the same pearl oyster species (P&amp;lt; 0.05). Our results suggest that the lower CR and activities of digestive enzymes and higher RRs and activities of carbonic anhydrase may cause a lower growth rate of P. maxima compared to P. f. martensii.

Selection of Tropical Microalgae Species for Mass Production Based on Lipid and Fatty Acid Profiles

Numerous recent studies have identified microalgae biofuel as one of the major renewable energy sources for sustainable development due to their high biomass productivity, high lipid content, and availability of locally adapted strains in various geographical locations. There have been minimal studies on the fatty acid composition of lipid production on local microalgae species in Sabah, Malaysia. Thus, screening for local microalgae species capable of producing biodiesel can aid in the selection of suitable species. This study aimed to isolate and identify promising local microalga as biodiesel feedstock for mass cultivation. Eight microalgae species,Acutodesmus obliquus,Chaetoceros muelleri,Isochrysis galbana,Ankistrodesmus falcatus,Chlamydomonas monadina,Chlorella emersonii,Nannochloropsis oculata, andTetraselmis chuii,were successfully isolated and identified from Kota Kinabalu, Sabah. The isolated microalgae were characterized based on the lipid/biomass productivity, lipid content and fatty acid profiles. These isolates had biomass productivity of 0.11–0.78 g/L/day, lipid content of 11.69–39.00% dry weight, and lipid productivity of 21.11–252.64 mg/L/day. According to GC-MS analyses, four isolates produced more than 80% of C14–C18fatty acids, which wereA. falcatus(95%),C. emersonii(93%),A. obliquus(91%), andC. muelleri(81%). Despite its low biomass productivity,C. muelleriwas chosen as the best biodiesel species candidate because of its moderately high lipid productivity (42.90 mg/L/day), highest lipid content (39% dry weight), high level of MUFAs and C14–C18FAs (81.47%), with the highest oleic acid proportion (28.38%), all of which are desirable characteristics for producing high-quality biodiesel.

Larval cultivation of Periglypta chemnitzii based on microalgal dietary selection

Periglypta chemnitzii is an edible shellfish whose hardy nature makes it an ideal species for cultivation by aquaculture. The crucial factor determining whether a species is appropriate for aquaculture is successful breeding of the offspring. In this study, we gathered information regarding reproduction and larval cultivation of P. chemnitzii and assessed the suitability of different microalgae diets to serve as a baseline for the purpose of artificial breeding of the offspring. The embryonic and larval development, larval morphological changes, movement, and feeding behaviour of P. chemnitzii were observed under an optical microscope. Eight microalgal species (Chlorella vulgaris, Nannochloropsis oculata, Dunaliella salina, Platymonas subcordiformis, Pavlova viridis, Dicrateria zhanjianggensis, Isochrysis galbana, and Chaetoceros muelleri) were fed to the larvae at different ages to observe the ingestion and digestion by the larvae. Four kinds of single microalgae diets (C. vulgaris, P. subcordiformis, C. muelleri, and D. zhanjianggensis) and three kinds of mixed diets (P. subcordiformis + C. muelleri, P. subcordiformis + D. zhanjianggensis, and C. muelleri + D. zhanjianggensis) were fed to larvae respectively, and their growth and survival rate was monitored. We found that the fertilised eggs of P. chemnitzii hatched into D-shaped larvae after 11 h 26 min; the larvae then developed to the metamorphic stage at 6 days post hatch (dph) and began settlement at 7 dph. The larvae could ingest C. vulgaris, N. oculata, D. salina, P. viridis, D. zhanjianggensis, and I. galbana at 1 dph; some larvae could also ingest P. subcordiformis and C. muelleri at 2 dph. Notably, C. vulgaris and N. oculata were more difficult to digest. Further, mixed diets were more beneficial than single diets for larval growth and survival. In particular, the mixed combination of P. subcordiformis + C. muelleri afforded the fastest growth and the highest survival rate. In single diets, the fastest growth was attained with C. muelleri; whereas the highest survival rate was obtained with P. subcordiformis. Compared with other bivalve molluscs, the clam P. chemnitzii has larger embryos and larger-sized newly hatched larvae, and its embryonic development and planktonic larval stage are also shorter than that of other species. P. chemnitzii larvae were more likely to ingest the smaller, round-shaped microalgal species and digest the species without cell walls, and therefore, D. zhanjianggensis should be the first choice as an opening diet for P. chemnitzii larval cultivation, followed by a mixed microalgal diet of P. subcordiformis + C. muelleri from 3 dph onwards.

Corrigendum to: Investigating the impact of light quality on macromolecular of Chaetoceros muelleri.

Diatoms (Bacillariophyceae) are important to primary productivity of aquatic ecosystems. This algal group is also a valuable source of high value compounds that are utilised as aquaculture feed. The productivity of diatoms is strongly driven by light and CO2 availability, and macro- and micronutrient concentrations. The light dependency of biomass productivity and metabolite composition is well researched in diatoms, but information on the impact of light quality, particularly the productivity return on energy invested when using different monochromatic light sources, remains scarce. In this work, the productivity return on energy invested of improving growth rate, photosynthetic activity, and metabolite productivity of the diatom Chaetoceros muelleri under defined wavelengths (blue, red, and green) as well as while light is analysed. By adjusting the different light qualities to equal photosynthetically utilisable radiation, it was found that the growth rate and photosynthetic oxygen evolution was unchanged under white, blue, and green light, but it was lower under red light. Blue light improved the productivity return on energy invested for biomass, total protein, total lipid, total carbohydrate, and in fatty acids production, which would suggest that blue light should be used for aquaculture feed production.

Chemical Profile and Antimicrobial Activity of the Marine Diatom Chaetoceros muelleri

Microalgae, due to its rapid growth, low nutritional requirements, and versatility of adaptation to different environmental conditions, has aroused the biotechnological interest, synthesizing novel molecules with antioxidant, anticoagulant, anti-inflammatory, anti-tumor, and antimicrobial activities. In this sense, we carried out the bioprospection of Chaetoceros muelleri , a marine diatom employed in aquaculture, as a candidate to the development of new drugs for the treatment of bacterial infections. The chemical profile of extracts in different solvents (hexane, chloroform, methylene chloride, ethyl acetate, methanol, and acetone) were analyzed by 1 H NMR. The hexanic extract was the most active against all bacteria species tested, including Mycobacterium tuberculosis , with a minimum inhibitory concentration of 100 µg/ml. Contrarily, the methanol extract was inactive against all tested microorganisms and, in addition, was the only one with IC50 > 800 µg/mL, showing no cytotoxicity in VERO cell line. All other extracts showed antibacterial potential and IC50 values varying between 267.58 and 142.47 µg/ml. The fact that C. muelleri is a microalga easily grown on bioreactors on a large scale may promote its biotechnological use, especially as scaffolds for the development of new compounds against bacterial species of clinical and public health interest.