Abstract
Adults, 3rd and 4th stage larvae of Camallanus acaudatus sp. n. (Nematoda, Camallanidae) are
described from the "aruanã", Osteoglossum bicirrhosum VANDELLI, from the Brazilian Amazon. The
male of C. tridentatus (DRASCHE, 1884) a parasite of "pirarucú", Arapaima gigas (CUVIER), is also
described and the female redescribed. Both of these species are hematophagous but C. acaudatus sp. n.
is thought to be more pathogenic because it penetrates the intestinal wall (rectum) and lives with as
much as a third of the anterior part of the body embedded in the host's tissue. The new species differs
from the others in the genus by having females with a sub-terminal anus, an absent tail, and a rounded
posterior extremity. The adult females have a dilated anterior extremity containing a sac-like expansion
of the distal part of the anterior uterus filled with larvae. The principal characteristics of C. tridentatus
are: 1) well developed tridents with long projections; 2) 20 - 21 (24) internal ridges in the buccal capsule;
3) one spicule in the male; 4) a prominent vulva located slightly posterior to the middle of the body;
5) a bifid tail (in the female) which varies from 120 - 150 (132) µm long. Camallanus acaudatus sp. n. is
the second species of the genus known from South American fishes. Both C. acaudalus sp. n. and C.
tridentatus are from hosts of the family Osteoglossidae.
