ALBERT

Description: We present in depth data of the sea urchin population in the Arctic Porsangerfjord. Sea urchins were collected by hand from randomly chosen square meters of two present habitats: a sea urchin barren, characterized by stony ground without major algae growth, and the neighbouring kelp forest with a healthy macroalgae community. Both habitats are located near the shoreline of a bay in the Porsangerfjord, called the Holmfjord, and sampling took place in less than 1 m depth at low tide. Sampling was conducted in two consecutive years, summer 2022 and summer 2023. Data collected from the sea urchins includes the test-diameter, freshmass, species and morphotype.

Description: Transcripts of relevant enzymes of the storage lipid metabolism were obtained from already existing transcriptomes that are available in the NCBI database (https://blast.ncbi.nlm.nih.gov/Blast.cgi). Transcriptomes originate from pooled midgut gland samples of several individuals cought in the North Sea. The transcriptome of Crangon crangon is found in the BioProject PRJNA479562 and of Pandalus montagui under BioProject PRJNA798226. Transcripts identified as relevant enzymes are noted by their Trinity_ID and identified through Blastn and Blastp. The nucleotide sequences were translated into amino acid sequences wih the largest ORF. More information about each of the transcriptomes is provided under the individual BioProjects.

Description: The storage lipid metabolism of two caridean shrimp species (Crangon crangon and Pandalus montagui) was studied through a combination of enzyme assays, total lipid determination and transcriptome analyses. The initital sampling was carried out in June, July and August 2021 by the research vessel R/V Uthörn. Freshly caught shrimps from the North Sea were measured, weighted and dissected and brought back to the laboratory facilites of the Alfread-Wegener-Institute, Bremerhaven, Germany. Individual midgut glands were weighted to determine the wet mass and freeze-dried. Dry mass was termined and lipids were extracted after Hagen (2000, see in Postel et al. 2000). The total lipid content of individual midgut glands of Crangon crangon and Pandalus montagui was determined gravimetrically. The synthesis of the storage lipid triacylglycerol (TAG) was measured in pooled microsomal fraction of midgut gland tissue of both shrimp species through the activity of the enzyme diacylglycerol acyltransferase (DGAT) at 37 °C in a water bath (McFie & Stone 2011). Here a fluorescent activated fatty acid (NBD-palmitoyl-CoA, 810229 Avanti Polar Lipids) was used. Lipids in the reaction mix were extracted and lipid classes separated on a thin layer chromatography plate. DGAT activity was measured through arbitrary fluorescent units (AFU/min/mg protein) of the correscponding TAG product. Annotated transcriptomes of both species (C. crangon Bioproject: PRJNA479562, NCBI; P. montagui Bioproject PRJNA798226, NCBI) were screened for enzymes involved in the lipid metabolism. Transcripts identified as relevant enzymes using BLAST were translated into amino acid sequences.

Description: The accumulation of storage lipids is an important life history trait and a key function in the energy metabolism of crustaceans. The common storage lipid in species from temperate regions is the neutral lipid triacylglycerol (TAG). It is synthesized through the Kennedy pathway by the enzyme diacylglycerol acyltransferase (DGAT). This enzyme is ubiquitous in eukaryotic species and is expressed as two evolutionary separated forms, DGAT1 and DGAT2. The caridean shrimps Crangon crangon and Pandalus montagui share a similar habitat but follow different metabolic strategies. Previous studies showed significantly lower total lipid (TL) levels in the midgut gland of C. crangon compared to P. montagui. While TAGs are frequent in P. montagui, phospholipids are the prominent lipid class in C. crangon. It is hypothesized that the reason for this difference in lipid class composition are mutated DGAT enzymes in C. crangon, which impair the synthesis of TAGs in the midgut gland. Therefore, the enzyme was studied by nucleotide and amino acid sequence analysis from transcriptome data and enzyme activity measurements. Both species possess transcripts encoding for DGAT1 and DGAT2. In C. crangon, a mutation in one DGAT1 isoform as well as a mutated cysteine residue in DGAT2 was found. These mutations are capable of impairing enzyme functionality. Using a fluorescent labeled substrate, DGAT activity was shown in both species. However, the DGAT activity of C. crangon was lower than that of P. montagui. Furthermore, C. crangon exhibits higher DGAT activity in spring than in summer, which indicates a seasonal variation of DGAT expression. The metabo-lic traits of C. crangon and P. montagui were also discussed in respect to their reproductive strategies, food spectrum, and their distributional range. This study showed that the TAG synthesis of C. crangon is reduced, which, at least partly, is due amino acid point mutations in the DGAT enzyme. As a consequence, C. crangon is unable to accumulate high amounts of storage lipids and must rely on continuous food supply. Probably, the inability of lipid storage also influenced the reproduction strategy of C. crangon towards a continuous long lasting reproduction period. Nevertheless, future studies are required to investigate the expression of DGAT mRNA, the substrate specificity of the DGAT isoforms, and the apparent seasonal pattern of DGAT activity and TAG synthesis.

Description: Brown shrimp, Crangon crangon (L.), is the most valuable target of coastal fisheries in the southern North Sea. Annual landings exceeded 30,000 tons in the last decade, yielding up to 100 Mio Euro. The shrimp are boiled immediately after capture onboard the fishing vessel for preservation and easy peeling. After landing, the shrimp are collected by traders and exported for manual peeling. Only the muscle of the pleon is returned and sold as regional delicacy. The remains, comprising the cephalothorax, the shell of the pleon, and, in case, adhering eggs, account for up to 70% of the total body mass. This potential resource, for example as aquaculture feed, has not yet been considered for exploitation. In this respect, the fatty acid (FA) profile and the share of essential FAs are crucial quality factors. Since boiling alters the quality of shrimp, this study evaluates changes in the FA composition of shrimp muscle and remains by comparing frozen and boiled samples. Major FAs in C. crangon were the saturated palmitic acid (PA, 16:0), accounting for 16.6%–19.1% of total fatty acids (TFAs), and the long-chain polyunsaturated FAs (LC-PUFAs) eicosapentaenoic acid (EPA, 20:5(n-3), 16.1–21.6%TFA ) and docosahexaenoic acid (DHA, 22:6(n-3), 11.5–13.6%TFA ). Frozen muscle and frozen remains showed similar FA profiles. Boiling changed the FA profile. PA, EPA, and DHA decreased by up to 25%, whereas palmitoleic acid 16:1(n-7) and oleic acid 18:1(n-9) increased by 2% to 3% each. Boiled muscle and boiled remains showed similar FA profiles. Despite the loss of FAs, the boiled shrimp remains are suggested to be a suitable PUFA supplement for aquaculture feeds, deserving further investigation.

Description: Processing remains of brown shrimp, Crangon crangon, account for up to 60 % of the catch while only the small muscle fraction is used for human consumption. Incorporation into aquafeeds for high-valued species would reduce waste, create by-product value and promote sustainable aquaculture development. A detailed chemical characterisation of the remains from mechanically peeled brown shrimp was made and apparent nutrient digestibility coefficients in Litopenaeus vannamei were investigated. Brown shrimp processing remains (BSPR) contain substantial amounts of key nutrients (521 g⋅kg-1 crude protein, 74 g⋅kg-1 total lipid, 15 MJ⋅kg-1 gross energy) and valuable functional ingredients were detected (cholesterol, astaxanthin). Apparent energy (82 %) and protein (86 %) digestibility coefficients reveal good bioavailability of these nutrients. Dry matter digestibility was lower (64 %) presumably due to the high ash content (244 g⋅kg-1). The amino acid profile meets dietary requirements of penaeid shrimp with high apparent lysine and methionine digestibility coefficients. Analysis of macro- and micro minerals showed reasonable levels of required dietary minerals (phosphorus, magnesium, copper, manganese, selenium, zinc) and apparent copper digestibility was high (93 %). Contamination levels present in BSPR were below European standards acceptable for human consumption. Processing remains of brown shrimp have a high potential as alternative feed ingredient in sustainable diets for L. vannamei in recirculating aquaculture systems.