Bogut et al. also determined in their aforementioned paper which fatty acids were present in their bloodworms as shown in the following table.

The lipid analysis revealed bloodworms to contain 34.03% PUFA’s, 30.42% monounsaturated fatty acids and 26.12% saturated fatty acids.

Palmitic acid was the main saturated fatty acid they found, this is a normal finding as it is the most commonly found saturated fatty acid in animals. It is a precursor for longer chained fatty acids[8].

Oleic acid was the main monounsaturated fat found, again a very normal finding as this acid is the most common found monounsaturated acid and is the precursor for long-chain unsaturated fatty acids.

The results indicated both linoleic acid and linolenic acid to be present in significant amounts, as required for foods destined to be fed to fish. Furthermore, both the PUFA’s eicosapentaenoic acid and docosahexaenoic acid were found to be present in a significant amount.

In the field of aquaculture (the commercial farming of aquatic animals such as fish, shrimp, mollusks etc.) a lot of attention has been given to enhancing the omega-3 (ω-3) fatty acid content of the farmed animals destined to be consumed by humans. This is due to the beneficial effect the consumption of omega-3 fatty acids has on human health. Bogut et al. therefore concluded that bloodworms could form a suitable natural component of a diet fed to farmed fish aimed to be fed to humans.

One should not forget that a lot of farmed fish (in Europe) are coldwater, marine fish as these command high market prices. Coldwater, marine fish are very dependant on the presence of omega-3 fatty acids in their food in order to be able to regulate the fluidity of their cell membranes in a cold environment. Plus, coldwater marine fish only have a limited ability to use carbohydrates as an energy source and therefore rely more on the presence of lipids in their food.

Why can one find linoleic acid and linoleic acid in significant numbers in bloodworms although they can’t synthesize these fatty acids? Because the species of bloodworm we process (Chironomus plumosus) feeds on plant detritus and sediment (and the bacteria and algae present in the sediment).

Most bacteria are able to synthesize all fatty acids required for their growth and reproduction. Both linoleic acid and linolenic acid are primary PUFA’s produced by plants and algae.

And where do eicosapentaenoic acid and docosahexaenoic acid come from? Both these fatty acids are only synthesized by marine algae, but bloodworms can synthesize these fatty acids themselves through the desaturation and elongation of α-linolenic acid, which they also get through the consumption of bacteria, algae and (decaying) plant matter.

        Chironomus plumosus larvae are commonly associated with bodies of water containing a large amount of decaying organic matter and/or aquatic macro-phytes. The larvae feed by scraping stones and sediment. When picking up a handful of live bloodworms for example (pictured), one can clearly feel the larvae scraping one’s skin, it’s feels like being licked by a cat.          

         MINERAL CONTENT

Fish can absorb minerals both from their food as well as from the water they are living in. Calcium, magnesium, sodium, potassium, iron, zinc, copper and selenium can be taken up from their aquatic environment, whilst phosphates and sulfates are more effectively obtained from the food they consume. Minerals are obviously required for forming and maintaining the skeletal structure, but are also involved in osmoregulatory functions, maintaining the cell membrane potential, and they form a role in the activation and deactivation of certain hormones and enzymes.

Bloodworms do contain significant amount of minerals such as calcium, magnesium, phosphorus, potassium, sulfur, sodium, iron, copper, manganese and zinc as substantiated by various nutritional analyses we had performed on our bloodworms throughout the years.

VITAMIN CONTENT

            Not that much is known about the vitamin content of bloodworms, although Kara T. (2013) found the levels of α-tocopherol (vitamin E), retinol (vitamin A₁), K₁, K₂, D₂ & D₃ to be present in bloodworms and varying with the season [9]. Regarding vitamin C (ascorbic acid), of which it is known that most fish can not synthesize it, and therefore needs to be present in the food they ingest, it was found to be present in bloodworms but in a very low amount. So why don't we add vitamin C to our bloodworm products in contrast to the practices of some of our competitors? Well, we can think of a couple of reasons:

• As stabilized vitamin C is a water soluble compound it does not make sense to add it to its single ingredient, frozen product line. Stabilized vitamin C is a powder and adding it to our frozen, single ingredient items will only result in the vitamin being dissolved in the added water.
• Stabilized vitamin C actually is L-ascorbyl-2-polyphosphate, so should we add it to the frozen bloodworms, Mysis, brine shrimp etc., our customers will actually be introducing a source of dissolved phosphate to their tanks. Definitely not wanted!
• The adding of phosphate groups to ascorbic acid (which in itself is very unstable) does indeed stabilize the vitamin, but only during storage in a dry and cool place and for a certain amount of time. As our bloodworms are a natural product they need to be stored in a freezer at a specified, low enough temperature for a certain amount of time before they can be sold to end users in order to make sure no viable cestodes, trematodes or nematodes are still present.

FIBER CONTENT

We measure anywhere from 3% to 9% fiber (expressed on a dry weight basis) when running nutritional analyses on our bloodworms. Bloodworms contain fiber (as most insects) in the form of chitin, an insoluble fiber making up the head capsule. Another source of fiber might be ingested plant matter still present in the bloodworm gut. A small amount of fiber present in feeds administered to fish is good as fiber will help the passing of feces through the gut, but higher amounts of fiber should be avoided as most fish lack the enzymes required to digest complex carbohydrates, especially coldwater fish and carnivorous fish are lacking these digestive enzymes.

PIGMENT CONTENT

The carotenoids α-carotene, β-carotene, canthaxanthin, cryptoxanthin, lutein, astacene and a ‘kind of xanthophyll which was not possible to identify’ were found to be present in larval Chironomus annularius by B. Czeczuga (1970)[10]. The larvae are thought to obtain these pigments from the detritus they consume. Maleknejad R. et al. (2014) substituted part of a commercial diet for fish breeders with either live bloodworms, live mosquito larvae (Culex sp.) or live brine shrimp and found that the inclusion of either of these live foods substantially increased the pigmentation of the cichlids they were feeding[11].

Indeed, due to the steep price increases of certain feed ingredients during the last decade (e.g. fishmeal and natural or synthetic pigments) researchers are trying to substitute a part of the commercial diets they purchase for rearing fish with live foods (strongly preferable but most of the time not very feasible) or frozen foods such as bloodworms, adult brine shrimp, various copepod species etc. as part of the diet of farmed fish.

CONCLUSION

No animals should be reared on or fed a single food but in our opinion bloodworms form a valuable contribution to a varied diet when keeping aquarium fish, aquatic amphibians or aquatic reptiles. They are a good source of proteins containing all essential amino acids fish require, contain arachidonic, linoleic and linolenic acid and are a good source of minerals and pigments. The fact that bloodworms are preyed upon by a wide variety of animals in nature should speak for i