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Abstract:
Artystone minima n. sp. (Isopoda, Cymothoidae) from the body cavities of pencil fish
(Nannostomus beckfordi GUENTHER) is described. The infected fish were caught in backwaters of
the upper Rio Negro, Amazonas State, Brazil. The new species is morphologically similar to Artystone
trysibia SCHIöDTE, 1866, from which it differs in several important respects. A. minima n. sp. is
smaller (3.3 - 6.9 mm rather than 22 - 25 mm). The small body size of these parasites permits them to
infect smaller fish hosts (3 - 4 cm instead of 15 - 30 cm). The small body size also limits to 13 - 15 the
number of eggs in the marsupia of mature females (compared to 400 for A. trysibia). The new species
also has a head that is free and a frons that is squared-off anteriorly whereas the head of A. trysibia is
immersed up to the eyes and the frons is convex. The lesions produced by this parasite in the fish show
no evidence of inflammatory reaction or of secondary invasions by bacteria.
