Crystallized hemoglobin in Rhodnius prolixus after a blood meal on guinea-pig

Several blood-sucking arthropods, after a blood meal, are able to store the hemoglobin from their hosts in a crystalline state in their digestive system. Guinea-pig hemoglobin crystallizes in the stomach of the reduviid bug Rhodnius prolixus in two different crystal types. We show them to be crystallographically identical and to contain the same liganded state of hemoglobin, i.e. they represent different habits of the same crystal modification. The hemoglobin crystallizes in oxy-form and ages in the crystalline state, first to aquomethemoglobin and subsequently to hemichrome without crystal cracking. The rate of aging appears to be the same for both types. The hemoglobin crystal modification observed in the digestive system of Rhodnius prolixus is highly host- but not parasite- specific. The same modification is also observed in vitro and in Ornithodorus moubata, an arachnid whose digestive system differs considerably from that of the insect Rhodnius. The retainment period of the crystals represents a long term host-record of possible medical interest.