Freshwater molluscs, snails (Gastropoda) and mussels (Bivalvia), are an excellent food for many species of freshwater fish and crustaceans. In rivers, lakes and reservoirs, molluscs form powerful bottom placers and foulings that are actively exploited by many cyprinid and other fish.

For example, it is shown that bream, Abramis brama, white bream, Blicca bjoerkna, common roach, Rutilus rutilus, and carp, Cyprinus carpio, can eat zebra mussel, Dreissena polymorpha, of size ranged from 1-2 to 45 mm depending on fish age (Prejs et al., 1990; Nagelkerke & Sibbing, 1996; Tucker et al., 1996). The real switch to zebra mussels would be expected in fish of 23–24 cm length (Prejs et al., 1990). Other abundant freshwater molluscs are Viviparus viviparus, V. ater, V. contectus and other viviparous snails. For example, newborn V. ater are eaten by barbel, Barbus barbus, roach, R. rutilus, rudd, Scardinius erythrophtalmus and tench, Tinca tinca (Keller & Ribi, 1993), while adult viviparids (with the relatively hard shell and shell size up to 45 mm) are eaten by all large cyprinid fish with the well developed pharyngeal teeth.

Composition

The proximate compositions and fatty acid profiles of the freshwater mussels Unio terminalis and Potamida littoralis are compared by Ersoy & Şereflişan (2010).  The crude protein (11,87-11,97 %), lipid (2,55-1,05 %), ash (1,68–1,61%) and moisture (80,36-81,69 %) contents of U. terminalis and P. littoralis are observed. Lipid content in U. terminalis is found to be significantly higher than in P. littoralis. The percentages of total saturated fatty acids and total monounsaturated fatty acids are higher in U. terminalis than in P. littoralis. At the same time, the corresponding content of total polyunsaturated fatty acids is lower. The n3-n6 ratio are 1,54-1,40 in U. terminalis and P. littoralis, respectively. Using these data, Ersoy & Şereflişan (2010) conclude that freshwater mussels U. terminalis and P. littoralis are suitable as the healthy food.

Freshwater and Saltwater Molluscs

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Free amino acid content in three species of earthworms, cosmopolitan tiger worms, Eisenia foetida, African earthworms, Eudrilus eugeniae, and Indian blue worms, Perionyx excavatus, are studied by Reinecke et al. (1991). Leucine and arginine are most abundant among essential amino acids in all three species. Crude protein content are 66,13 % in E. foetida, 58,38 % in E. eugeniae, 61,63 % in P. excavatus and 61,00 % in fishmeal, for comparison. The amino acid profile in four species of earthworms namely E. eugeniae, Hyperiodrilus africanus, Alma millsoni and Libyodrilus violaceus, in comparison with E. foetida, is studied by Dedeke et al. (2010). Arginine is most abundant in four African species and one of the abundant essential amino acids (after leucine and lysine) in E. foetida. Glutamic and aspartic acids, among non-essential amino acids, are most abundant than arginine and leucine in all five species, achieving 16,4 g per100g crude protein in E. foetida.

Lysine and methionine, that are limited amino acids in most feedstuffs, are present in all species of earthworms (Dedeke et al., 2010).

Earthworm Meal

Earthworm meal (Lumbricus rubellus) has become one of the natural materials that can be used as feed additive. The study of Istiqomah et al. (2009) is carried out (1) to evaluate the amino acid profile of earthworm and earthworm meal, (2) to calculate the value of essential amino acid index of both materials. It is shown that essential amino acid of earthworm is dominated by histidine (0,63 % of dry matter basis), meanwhile the earthworm meal is dominated by isoleucine (1,98 %). The non-essential amino acid of earthworm and earthworm meal is dominated by glutamic acid (1,52 % and 3,60 % of dry matter basis, respectively). The value of essential amino acid index obtained from earthworm meal is higher (58,67,%) than those from earthworm (21,23 %). It is concluded that powdering method of earthworm by using formic acid addition has higher amino acid balance than earthworm.

According to data by Istiqomah et al. (2009) and other authors, earthworm meal of L. rubellus contains 65,63 % crude protein, earthworm meal of L. terestris contains 32,60 % crude protein, earthworm meal of P. excavatus contains 57,20 % crude protein and have complete amino acids. Dynes (2003) gives the similar results on crude protein in earthworm meal of Eisenia andrei and E. foetida.

Silage

Earthworms (E. foetida and L. rubellus) have been ensiled with sorghum and molasses in the following proportions: 1) 60% earthworms, 40% sorghum; 2) 60% earthworms, 40% sorghum, adjusting pH to 4,0 with HCl; 3) 60% earthworms, 20% sorghum, 20% molasses; 4) 60% earthworms, 20% sorghum, 20% molasses, adjusting pH to 4,0 with HCl (Ortega Cerrilla et al., 1996). These four mixtures have been allowed to ferment for 15 days at 18^o C. No essential differences are in the percentage of moisture, ether extract, crude fiber and crude protein for treatments 1, 2, 3 and 4, respectively, hence Ortega Cerrilla et al. (1996) conclude that it is possible to preserve earthworms E. foetida and L. rubellus by ensiling, adding carbohydrates like sorghum or molasses, and that an addition of acids to have an adequate fermentation is optional.

Vermicomposts

Basically, vermicomposts contains cow, horse and other manure, agricultural waste, tree leaves and other vegetable byproducts, processed by earthworms, together with the ... Read more »