Effects of Copper and the Insecticide Cypermethrin on a Soil Ciliate (Protozoa: Ciliophora) Community.

Ciliated protozoa play important ecological roles in soils, yet few studies have investigated the effect of soil pollution on them. We determined the effect of copper (Cu) and cypermethrin on a soil ciliate community under microcosm conditions. Soils were treated with Cu or cypermethrin and the abundance and species richness of ciliates determined 15 days later. Cu treatment increased soil ciliates abundance at the highest concentration (960 mg kg-1), as did cypermethrin at a treatment of 160 mg kg-1. No negative effect on ciliate abundance was found for either substance due to increased numbers of tolerant species, particularly Homalogastra setosa and Chilodonella uncinata in the case of Cu and Colpoda stenii and Colpoda inflata for cypermethrin treatments. However, several species were absent at high treatment levels. Notably, Halteria grandinella was not found in Cu treatments above 240 mg kg-1, whilst Oxytricha setigera was not found in cypermethrin treatments above 160 mg kg-1. For Homalogastra setosa, there was an initial positive response to cypermethrin, but abundance then decreased at a treatment of 320 mg kg-1, and treatment at 640 mg kg-1 eradicated the species from the microcosms. Accordingly, both substances affected the structure of the soil ciliate community at high concentrations.

Morphology and Phylogeny of the Ciliate Psilotricha silvicola n. sp. (Alveolata, Ciliophora) from Woodland Soils in the United Kingdom.

The genus Psilotricha was established by Stein in 1859, with P. acuminata as the type species within the family Oxytrichidae. This species lacked a full description until it was re-discovered in 2001, showing that its morphological and morphogenetic characters confirmed the inclusion in the family Oxytrichidae. Since then, the genus Psilotricha has had a convoluted taxonomy despite the morphological evidence available. In this paper, we describe a new Psilotricha species, Psilotricha silvicola n. sp., from woodland soils in Southern England (United Kingdom). The morphology was investigated in live and protargol-impregnated specimens. Our findings show that P. silvicola n. sp. shares morphological characteristics with P. acuminata, including the distinctive cell shape and the long and sparse cirri. Phylogenetic analysis of the 18S rRNA gene places this new species within the family Oxytrichidae, nested apart from the family Psilotrichidae (which includes the genera Urospinula, Psilotrichides and Hemiholosticha), in a clade containing species of the family Oxytrichidae. Furthermore, the morphology of another Psilotricha species, P. viridis, found in a freshwater pond in the same woodland area, is also here described, bringing additional insight into the taxonomy of the genus. Our findings provide further evidence for inclusion of the genus Psilotricha within the oxytrichids.