DHA Accumulation in the Polar Lipids of the Euryhaline Copepod Pseudodiaptomus inopinus and Its Transfer to Red Sea Bream Pagrus major Larvae

The euryhaline copepod Pseudodiaptomus inopinus play important roles in coastal waters as vectors of docosahexanoic (DHA) and eicosapentaenoic (EPA) acids for larval fish. While DHA and EPA in polar lipids (PLs) are more effective for fish larval development than non-polar lipid forms (NLs), there is little knowledge how much these lipids are accumulated in copepods from microalgae and are effective for early development of fish larvae. We report PLs fatty acid profiles of P. inopinus fed DHA-poor microalgae and evaluate its significance as a food source for larvae development of Pagrus major, compared with DHA-enriched rotifers. Copepods and rotifers were fed a mixed diet of three algal species (Phaeodactylum tricornutum, Tisochrysis lutea, and Pavlova lutheri), in addition of DHA-supplemented Super Fresh Chlorella (SFC) for rotifers. Compared with SFC, the algal mixture had higher EPA but lower DHA. Copepods had higher DHA and EPA in total lipids than rotifers fed each diet. Copepod PLs were specifically enriched with DHA and their contents were higher than both rotifers. On the other hand, PLs EPA contents were comparable between preys, indicating that copepods selectively fortified the PLs. Fish culture experiment showed that larvae fed copepods had higher growth than those fed SFC-enriched rotifers. Principal component analysis for each organism fatty acid composition emphasized trophic modification of DHA by copepods toward larval fish. This study highlighted that P. inopinus contribute to enhanced growth of coastal larval fish by efficiently transferring DHA via copepod fatty acid metabolism.

Effect of species diversity on particle clearance and productivity in farmed bivalves

Most bivalve farms are designed as monocultures, yet diverse communities often outperform monocultures in various metrics of ecosystem functioning, including particle clearance and productivity. This study tested the feasibility of bivalve polyculture by examining particle clearance, growth, and survival of 4 species that are economically important to the northeastern USA. Three particle depletion experiments were conducted to determine if more diverse bivalve assemblages had greater clearance rates than those which were less diverse. Different assemblages of Crassostrea virginica, Spisula solidissima, Mercenaria mercenaria, and Mya arenaria were supplied with a single cultured algal species, a mix of 2 cultured algal species, or natural seston. To determine how species richness affects bivalve productivity, growth and survival were monitored in a flow-through mesocosm experiment, which simulated farm conditions. In the cultured algae experiments, more diverse assemblages did not exhibit significantly greater clearance rates than those that were less diverse. Instead, the clearance rates of each species were additive across assemblages. Surprisingly, most assemblages did not display a significant preference for the larger microalgae species, Pavlova lutheri (4.0-6.0 µm), over Nannochloropsis oculata (1.90-3.75 µm). Most notably, when supplied with natural seston, the 4-species polyculture demonstrated a significantly greater tank-level clearance rate for particles <25 µm compared to most monocultures. However, nearly all productivity metrics were not significantly affected by species richness. This work suggests that some degree of complementarity exists among these bivalves, and that in non-food limited systems, these bivalves could be co-cultured without outcompeting one another.

Marine Microalgae Biomolecules and Their Adhesion Capacity to Salmonella enterica sv. Typhimurium

Different molecules have been tested as analog receptors due to their capacity to bind bacteria and prevent cell adhesion. By using in vitro assays, the present study characterized the aqueous and alkaline extracts from microalgae Pavlova lutheri and Pavlova gyrans and evaluated the capacity of these extracts to adhere to enterobacteria (Salmonella Typhimurium). The aqueous and alkaline extracts of both species were fractionated via freeze-thawing, giving rise to soluble and insoluble (precipitate) fractions in cold water. The obtained fractions were studied using thermogravimetric, methylation analyses, and using 1D and 2D NMR techniques. The cold-water-soluble fractions obtained from the aqueous extracts were mainly composed of highly branched (1→3),(1→6)-β-glucans, whereas the cold-water-precipitate fractions were constituted by (1→3)-β-glucans. The alkaline extract fractions showed similar compositions with a high protein content, and the presence of glycosides (sulfoquinovosylglycerol (SQG), digalactosylglycerol (DGG)), and free fatty acids. The linear (1→3)-β-glucans and the alkaline extract fractions showed an adhesion capacity toward Salmonella. The chemical composition of the active fractions suggested that the presence of three-linked β-glucose units, as well as microalgal proteins and glycosides, could be important in the adhesion process. Therefore, these microalgal species possess a high potential to serve as a source of anti-adhesive compounds.

ANALISIS KECEPATAN FILTRASI DENGAN JENIS PAKAN YANG BERBEDA TERHADAP KELANGSUNGAN HIDUP SPAT KERANG MUTIARA (Pinctada maxima)

Penelitian ini bertujuan untuk mengetahui kecepatan filtrasi kerang mutiara dengan jenis pakan yang berbeda, untuk selanjutnya ditentukan jenis pakan yang disukai oleh spat kerang mutiara (Pinctada maxima). Penelitian ini dilaksanakan di PT. Autore Pearl Culture, Kecamatan Pemenang, Kabupaten Lombok Utara, NTB pada tanggal 25 April hingga 25 Mei 2017. Penelitian ini menggunakan faktor uji jenis pakan yang berbeda, masing-masing faktor uji terdiri dari 3 perlakuan yaitu pemberian pakan alami dengan jenisIsochrysis galbana, Pavlova lutheri, Chaetoceros sp., dengan kepadatan 270.000 sel/ml. Setiap unit percobaan selanjutnya disusun dalam Rancangan Acak Lengkap (RAL), dengan media pemeliharaan berupa toples plastik volume 5000 ml. Pemeliharaan dilakukan selama 30 hari. Parameter yang diamati adalah clearance rate, filtration rate, aktivitas makan, tingkat konsumsi pakan dan tingkat kelangsungan hidup. Data dianalisis menggunakan analisis sidik ragam (ANOVA) dengan taraf nyata 5%. Hasil penelitian menunjukkan bahwa kecepatan filtrasi dengan pemberian jenis pakan yang berbeda selama pemeliharaan spat kerang mutiara (P. maxima) memberikan pengaruh nyata (p<0,05) terhadap kelangsungan hidup spat. Dengan nilai kelangsungan hidup rata-rata tertinggi diperoleh dari pemberian pakan Chaetoceros sp. yaitu sebesar 76.67% ±19.66 dibandingkan dengan pemberian Isochrysis galbana, Pavlova lutheri.