Epibiosis is very common between crustaceans and ciliates where the calcified surface of the crustacean body provides a suitable substrate for ciliate colonization. The aim of this contribution is to provide data about a new record between the epistylid ciliate Epistylis hentscheli Kahl, 1935, and the crayfish Procambarus (Austrocambarus) sp. The distribution of the epistylid on the basibiont body and its cellular/colonial characteristics were analyzed. Procambarus (Austrocambarus) sp. harbored colonies of E. hentscheli only on the pereiopods. This is the first record of this peritrich ciliate as an epibiont on Crustacea, having been previously found on algae and fish.

Peritrichs usually settle on the external surface and gills of crustaceans. However, their physiological effect on the host has not been studied. Respiratory rate is a susceptible index for some factors that affect an organism. To test if ciliates attached to the crustacean gills have a physiological effect, we measured crustacean oxygen consumption in a closed system. Crayfish Cambarellus (Cambarellus) montezumae were collected in Lago Xochimilco in Mexico City and were isolated in chambers. Two peritrich species, Cothurnia variabilis (32.5%) and Epistylis gammari (67.5%), were observed on the gills. The metabolic rate was evaluated by oxygen consumption with a polarimetric oximeter. Statistical analyses demonstrated that a density of ciliates attached to the gills of the crayfish above ~50 individuals increased oxygen consumption with a positive correlation to epibiont density. We conclude that C. variabilis and E. gammari ciliate epibionts attached to the gill of the crayfish Cambarellus (Cambarellus) montezumae cause an increase in metabolic rate.

The epibiotic relationship between crustaceans and ciliates is frequent, for example, with species of suctorians. This work aims to present an updated list of species of the family Podophryidae worldwide distributed as epibionts of crustaceans and its geographic distribution. The available literature was checked, and all the species were verified. We found four species and four species indeterminata attached to 16 species of crustaceans. For the American continent, we obtained four species, and for Africa and Oceania, we did not find any species.

Epibiosis is common among ciliates and crustaceans because the calcified surface of the crustacean body offers a suitable site for colonization by the epibiont. Suctoria are among the most common epibiont ciliate groups of freshwater decapod crustaceans. The aim of this study is to increase knowledge of suctorians as epibionts of freshwater decapod crustaceans of the families Cambaridae and Pseudothelphusidae. Crustaceans were collected from three rivers and one pond in Chiapas, Mexico. Six species of suctorian epibionts were recorded: Acineta tuberosa, Podophrya maupasi, P. sandi, Tokophrya cyclopum, T. quadripartita and Trichophrya epistylidis. This is the first record of ciliate epibionts on members of family Pseudothelphusidae (represented by Phrygiopilus montebelloensis and Raddaus bocourti), and the first record of suctorians epibionts on Procambarus (Austrocambarus) sp. (Cambaridae).