Comparative chemical composition of two freshwater sludgeworms, Tubifex tubifex and Limnodrilus hoffmeisteri, has been studied by Whitten & Goodnight (1982). These authors have found, in particular, that L. hoffmeisteri contain the significantly greater amount of lipid soluble material than T. tubifex. Graney et al. (1986) have measured the concentrations of free amino acids in five species of freshwater sludgeworms (L. hoffmeisteri, T. tubifex, Potamothrix moldaviensis, P. vejdovskyi and Stylodrilus heringianus). Alanine, represented between 23,1 % and 41,8 % of the total free amino acid pool, has been found to be most abundant in all species.

Chemical composition of T. tubifex is determined by Saglio et al., (1990) in the context to study the  attractiveness of amino acids to fish.. Basic amino acids such as lysine (12,0 mg l⁻¹), histidine (9,1 mg l⁻¹) and arginine (8,1 mg l⁻¹) as well as non-polar amino acid such as alanine (11,7 mg l⁻¹) are most abundant in the crude tubifex extract (500 mg l⁻¹).

According to Yanar et al. (2003), the most abundant amino acids (g per 100 g protein) in T. tubifex are lysine (6,54), leucine (6,52) and argenine (5,39). On the crude protein content (% of dry matter), T. tubifex (58,68 %) is near to enchytraeid worms, Enchytraeus sp., and brine shrimp, Artemia salina, but lags behind cladocerans, such as Daphnia sp. and Moina sp., as well as copepods, such as Tigriopius japonicus and Acartia clausi (from 70,09 % to 72,13 %). Total fatty acid content is 7.28 mg per 100 mg dry weight, ω-3 and ω-6 fatty acids compose 18 % and 22 % of the total, respectively (Yanar et al., 2003).

T. tubifex can be considered as the caratenoid source with the total carotenoids measured at the level of 15,02 mg kg^-1 (Yanar et al., 2003). This amount is close to the value (about 40 mg kg^-1) needed in diet of fish to ensure their pigmentation (e.g., Christansen & Wallace, 1988; Choubert & Storebakken 1989).

Attractiveness

Accordung to Saglio et al., (1990), the crude tubifex extract is significantly attractive for common carp, Cyprinus carpio, in the range of concentrations tested (5 mg l⁻¹, 50 mg l⁻¹, 500 mg l⁻¹, 5 g l⁻¹). Maximum attraction is obtained in response to the extract with concentration of 500 mg l⁻¹.

Experimental tests of the four chemical groups of amino acids show that acidic amino acids (aspartic and glutamic) do not produce significant activity in carp. Basic amino acids (lysine, histidine and arginine) as well as polar, uncharged amino acids (glycine, serine, threonine, tyrosine, asparagine and glutamine) are ineffective as attractants but significantly increase exploratory behaviour in carp. Non-polar amino acids (alanine, valine, leucine, isoleucine, phenylalanine and methionine) show significant effects on both attraction and exploration.

Saglio et al., (1990) have found that combination of alanine, valine and glycine acts similar to the crude tubifex extract. To match the dose of 500 mg l⁻¹ of the crude tubifex extract, concentrations of alanine, valine and glycine are 1,3 x 10^-7 mol l⁻¹, 5,7 x 10^-8 mol l⁻¹ and 5,0 x 10^-8 mol l⁻¹, respectively.

For camparison, an extract of pupa silkworm, Bombyx mori, contains more acidic amino acids (27,1%) (Tsushima & Ina, 1978) than an extract of sludgeworms (10,9%). According to experimental findings by Kasumyan & Morsi (1996), asparttic and glutamic acids are attractive (after cysteine and proline) for C. carpio as gustatory stimulants.

Basic References