Modern experiments have shown that the candiru feeds by approaching a host fish and swimming alongside it until close to the gill cover. It then attempts to penetrate the gill chamber by forcing itself underneath. The candiru has also been seen entering the host through its mouth, though this behavior seems to be rare. While latched onto the host fish's gill chamber with sharp teeth, the candiru goes limp and quickly swells up with blood. The gut of this species is a straight tube with loosely-spaced fibers lining the walls of the connective tissue, most likely facilitating the swelling of the belly that is associated with the candiru. The lack of any protrusible jaw supports the theory that this species does not suck blood, but rather bites into a blood vessel and ingests the fluid that flows freely into the mouth. Because the candiru relies on the blood pressure of the host to ingest blood from the ventral or dorsal arteries, host fish must be selected by size.
Modern experiments have shown that the candiru feeds by approaching a host fish and swimming alongside it until close to the gill cover. It then attempts to penetrate the gill chamber by forcing itself underneath. The candiru has also been seen entering the host through its mouth, though this behavior seems to be rare. While latched onto the host fish's gill chamber with sharp teeth, the candiru goes limp and quickly swells up with blood. The gut of this species is a straight tube with loosely-spaced fibers lining the walls of the connective tissue, most likely facilitating the swelling of the belly that is associated with the candiru. The lack of any protrusible jaw supports the theory that this species does not suck blood, but rather bites into a blood vessel and ingests the fluid that flows freely into the mouth. Because the candiru relies on th:e blood pressure of the host to ingest blood from the ventral or dorsal arteries, host fish must be selected by size.