Zooplankton

The amino acid content in freshwater copepods (Eudiaptomus zachariasi), cladocerans Daphnia pulex and Ceriodaphnia sp. as well as copepodites (Cyclops strenuus) is studied by Dabrowski & Rusiecki (1983). Yet, the amino acid content in saltwater brine shrimp, Artemia salina, nauplii on hatching and during fasting is determined.

The major free amino acids in C. strenuus dry matter are 1,43 % arginine, 0,22 % histidine, 0,20 % alanine, 0,15 % glutamic acid and 0,11% lysine. Free arginine content decreases in the daphnids as they increase in the size. The content of all free amino acids in fasting Artemia nauplii is lower than in the freshwater zooplankters. The major free amino acids in nauplii are 0.55 % proline, 0.41 % alanine, 0.34 % glycine and 0.37 % serine, respectively.

Chemical composition of Daphnia longispina and other daphnids is studied by Holm & Walther (1988). Non-polar amino acid alanine ((from 13,4 mol % to 20,3 mol %), basic amino acids arginine (11,6 mol %) and lysine (10,2 mol %) as well as polar, uncharged amino acid glycine (10,0 mol %) are most abundant in the plankton extract.

The same authors have demonstrated rapid leakage of amino acids from frozen daphnids upon thawing.

The moisture content, crude protein level and amino acid profile of three freshwater zooplankton (Moina micrura, Diaphanosoma excisum, Brachionus calyciflorus) commonly used for rearing fish larvae are analyzed by Ovie & Ovie (2006). The moisture contents and crude protein levels are similar, as follows: M. micrura 89,0 % and 52,4 %; D. excisum 89,3 % and 57,3 %; B. calyciflorus 91,6 % and 50,3 %, respectively. The samples are represented by 17 amino acids: nine essential and eight non-essential amino acids. The dominant essential amino acids (per 16 g N) in M. micrura are lysine (10.73 g), arginine (8,17 g) and leucine (8,0 g); in D. excisum lysine (9,95 g), leucine (8,0 g) and valine (6,23 g); in B. calyciflorus leucine (8,95 g), lysine (8,64 g) and arginine (6,37 g). According to Ovie & Ovie (2006), in all three species tested (M. micrura, D. excisum, B. calyciflorus), glutamine and aspartic acid dominate the non-essential amino acid profile.

Seasonal Variations

Seasonal variations in the concentrations of 19 free amino acids in the whole body homogenates of freshwater amphipod Gammarus pseudolimnaeus are measured by Graney & Giesy (1986). The greatest total concentrations of free amino acids, 226,9 and 286,4 nmol per mg dry weight, are observed in April and May, with declining through summer months. The pattern of relative concentrations of individual free amino acids in G. pseudolimnaeus is found to be similar to that of other freshwater invertebrates. Alanine represents the most abundant amino acid (16,2-22,4 %) throughout an entire year. Arginine and leucine exhibit the next greatest abundances and comprised an average of 10,2 and 10,4 % of the total free amino acid concentration, respectively.

Holm & Walther (1988) give seasonal variations in the concentrations of free amino acids in D. longispina and other daphnids.

Amino acid profile of amphipod Gammarus lacustris in the beginning of autumn has the high level of alanine (22,6 mmol per ml of homogenate) and ornithine (17,6 mmol) (Karanova & Andreev, 2010). The amount of alanine and ornithine accounts for 39,8 % of the total pool of free amino acids, taken together alanine, ornithine, lysine and leucine form 55% of this pool.

Decapoda

The abdominal muscle, antennal gland, haemolymph, hepatopancreas and ovary of freshwater Astacus leptodactylus are analysed for free and protein-bound amino acids by van Marrewijk & Ravestein (1974). Free amino acid content is highest in the abdominal muscle and lowest in the haemolymph. The most abundant free amino acids are glycine, arginine and alanine. Together they account for up to 38 mol % in the hepatopancreas and up to 73 mol % in the abdominal muscle of the total amount. The content of free amino acids in the hemolymph of three crayfish species, Astacus astacus, A. leptodactylus and Ortonectes limosus, is researched by Rogala et al. (1978), setting the differences in lysine and histidine content.

In freshwater Chinese mitten crab, Eriocheir sinensis, and A. astacus concentration of amino acids is less than in marine decapods (Camien et al., 1951) (mitten crab is an invasive species that lives in freshwater but migrates seawards to breed).

Freshwater and Saltwater Crustaceans

Among the various biochemical compounds in freshwater and marine copepods, cladocerans, euphausiids and mysiids, protein, phospholipids, carbohydrates as well as chitin show no significant differences either between taxonomic groups or habitat types (Ventura, 2006). In contrast, differences occur in freshwater versus marine species and among taxonomic groups for lipids, free amino acids, nucleotides and nucleic acids.

According to Camien et al. (1951), concentration of amino acids in freshwater decapods (E. sinensis and A. astacus) is less than in marine decapods (Homarus vulgaris and Maja squinado) that is connected with the regulation of greater osmotic pressure in the marine environment.

Carr et al. (1996) give comparative data on concentrations of free amino acids and other substances in marine euphausiids and decapods.

Glycine is abundant in marine decapods similar to freshwater species, plus more amounts of taurine (Weber & van Marrewijk, 1972) and betaine (Carr et al., 1996) that are absent in freshwater species. For example, in euryhaline brown shrimp, Crangon crangon, the amount of taurine grows with the growth of salinity (from 224,16 μmol for 17,1 ‰  to 419,83 μmol per g fresh weight for 40.8 ‰) (Weber & van Marrewijk, 1972).

Basic References

Camien M.N., Sarlet H., Duchâteau G., Florkin M. 1951. Non-protein amino acids in mussle and blood of marine and fresh water crustacea. Journal of Biological Chemistry 193, 881-885

Carr W.E.S., Netherton III J.C., Gleeson R.A., Derby C.D. 1996. Stimulants of feeding behavior in fish: analyses of tissues of diverse marine organisms. The Biological Bulletin 190, 149-160

Dabrowski K., Rusiecki M. 1983. Content of total and free amino acids in zooplanktonic food of fish larvae. Aquaculture 30, 31-42

Graney R.L., Giesy J.P. Jr. 1986. Seasonal changes in the free amino acid pool of the freshwater amphipod Gammarus pseudolimnaeus Bousfield (Crustacea: Amphipoda). Comparative Biochemistry and Physiology Part A: Physiology 85, 535-543

Holm J.C., Walther B.T. 1988. Free amino acids in live freshwater zooplankton and dry feed: Possible importance for first feeding in Atlantic salmon fry (Salmo salar). Aquaculture 71, 223-234

Karanova M.V., Andreev A.A. 2010. Free amino acids and reducing sugars in the freshwater shrimp Gammarus lacustris (Crustacea, Amphipoda) at the initial stage of preparation to winter season. Journal of Evolutionary Biochemistry and Physiology 46, 279-283

Ovie S. I., Ovie S.O. 2006. Moisture, protein, and amino acid contents of three freshwater zooplankton used as feed for aquacultured larvae and postlarvae. The Israeli Journal of Aquaculture 58, 29-33.

Rogala A., Michalak W., Gondko R. 1978. Free amino acids in the hemolymph of three species of freshwater crayfish. Comparative Biochemistry and Physiology Part A: Physiology 60, 445-446

van Marrewijk W.J.A., Ravestein H.J.L. 1974. Amino acid metabolism of Astacus leptodactylus Esch. I. Composition of the free and protein-bound amino acids in different organs of the crayfish. Comparative Biochemistry and Physiology Part B: Comparative Biochemistry 47, 531-542

Ventura M., 2006. Linking biochemical and elemental composition in freshwater and marine crustacean zooplankton. Marine Ecology Progress Series 327, 233-246

Weber R.E., van Marrewijk W.J.A. 1972. Free amino acids in the shrimp Crangon crangon and their osmoregulatory significance. Netherlands Journal of Sea Research 5, 391-415