Microcotyle arripis is a species of monogenean, parasitic on the gills of a marine fish.

[4] Microcotyle arripis has the general morphology of all species of Microcotyle, with a symmetrical elongated body tapered posteriorly and anteriorly, comprising an anterior part which contains most organs and a posterior part called the haptor.

The haptor is symmetrical, not well delimited from body proper and bears 35 pairs of clamps, arranged as two rows, one on each side.

The digestive organs include an anterior, terminal mouth, a circular muscular pharynx situated very close to the oral suckers, an oesophagus bifurcating a little distance behind the genital atrium and a posterior intestine with two lateral branches that penetrates the haptor and are provided with numerous secondary branches.

The reproductive organs include an anterior genital atrium opening a little distance behind the pharynx, armed with numerous conical spines, a medio-dorsal vagina, a single S-shaped ovary and 23 testes posterior to the ovary, of irregular shape and fit closely against one another.