Phreatobius sanguijuela

This small fish reaches a maximum standard length of 4.2 cm (1.7 in).^[2] P. sanguijuela differs from P. cisternarum in a number of ways, but the main differences are the absence of eyes (which are present in P. cisternarum).^[2]

This species was first discovered in a hand-dug well located within the Paragúa River drainage, a tributary of the Guaporé (Iténez) River in Bolivia.^[2] Later it was discovered just across the border in several wells near São Francisco do Guaporé in the Brazilian state of Rondônia.^[3] This species is threatened by environmental degradation due to pollution, water extraction for drinking and irrigation, mineral extraction, and associated erosion.^[2] It is often killed when accidentally caught from wells because of a superficial resemblance to leeches.^[2]