With over one million described species, the phylum Arthropoda is the most diverse group of animals to have appeared in the evolutionary history of the earth. Members of the group represent by themselves three-fourths of all living organisms and fit ecologically in every type of habitat, where they use any source of food available to them. By virtue of this adaptation and trophic plasticity, some arthropods have evolved the habit of feeding on the blood of a wide range of animals, including mammals, birds, reptile amphibians and fish.
Hematophagous (blood-feeders) arthropods have been studied intensively over the past decades, mainly because of their primary role as disease vectors of human and livestock. Seven out of ten Tropical Disease Research (TDR) of the World Health Organization is arthropod-borne, related to blood-feeding. This article, essentially based on the review of the literature, gives an overview of the blood-feeding behavior among arthropods.
Successful blood-feeding is more than merely being able to acquire the blood, handling the blood meal represents a challenged that must have been resolved by the development of processing adaptations. Most often, hematophagous arthropods take a large amount of blood. For instance mosquito and triatomines bug can take three up to ten times their body size (Friend et al, 1965). Ticks, however, being the most “professional blood-feeder” take up to several hundred its body size (Ben et al, 2003).
Hemoglobin alone accounts for 60% of blood meal protein content and represents the major source of protein for hematophagous insects (Graca- Souza et al, 2006). Therefore hemoglobin digestion is crucial in order to gain the advantage of the blood meal. This has been possible by the development of proteolytic enzymes such as trypsins and chymotrypsins that break down hemoglobin into amino acids, which are then incorporated into different physiological processes of the hematophagous arthropod.
In addition, various arthropods have developed similar mechanisms to deal the toxicity of heme resulting from the degradation of hemoglobin. In mosquitoes and triatomine bugs heme is processed by heme oxygenase which degrades the heme into carbon monoxide, iron, and biliverdin, and allows them to survive its deleterious effect. Other blood-feeders bind heme to peritrophin in the midgut thereby sequestering it. It has been also shown that triatomines bugs crystallize free heme into hemozoin in in a similar fashion as plasmodium does during its intra-erythrocytic form to circumvent the toxicity of heme.