Acineta

Abstract: The suctoria have received less attention than some of the other ciliate groups. Most papers in the past 50 years have been particularly concerned with the description of the different budding methods found in the group and the inclusion of these data in devising new classifications for the subclass. Keys to their identification have been few and this has led to taxonomic confusion particularly at the generic level. It is apparent that we are still unclear as to what consitutes a genus as far as the suctoria are concerned and this was the first major problem to be overcome. Many difficulties were encountered with the suctoria when preparing a generic key to all freshwater ciliates (Curds, 1982), but it was decided at the time that it was not within the province of that book to include major generic revisions and acceptable published classifications were adhered to as far as possible. The present publication is the first of a series of papers that should enable the ecologist and taxonomist to identify all species of suctoria described to date. The initial approach was to create a database of published information concerning suctorian genera on a computer. An on-line identification programme made it possible to be able to quickly compare the descriptions of species with published generic descriptions, and in this way the accuracy of the original and subsequent generic identifications could be assessed. In a surprising number of cases it was found that species had been assigned to incorrect genera. So far it has been necessary to erect one new genus and several recently described genera have been synonymised. It was

Abstract: Because heavy branchial infestations are thought to interfere with respiration, we examined the attachment of three stalked ciliates commonly found in the branchial chambers of Louisiana crawfish. Attachments by Cothurnia sp., Epistylis sp. and Acineta sp. differ in their fine structure. Stalks of the peritrichous ciliates. Cothurnia and Epistylis, contain striated tubules that differ in their arrangement, diameter, and in the periodicity of their striations. In both species the striated tubules branch within the basal disk and attach to a pad of adhesive material secreted by the organism during initial attachment to the gill surface. The stalk of the suctorian Acineta is composed of a striated honeycomb-like matrix. Within the basal disc the matrix is disorganized; however, striated elements anchor the stalk to a pad of adhesive material. Attachment sites also differ in the amount of secretory material deposited. Cothurnia forms a multi-layered, granular pad; Epistylis forms an indistinct, microfibrillar layer, and Acineta deposits a thick mucoid pad. None of the ciliates appear to damage the gill epicuticle nor is there an obvious host response. Harmful effects are probably limited to a decrease in respiratory surface area and disruption of normal water flow patterns. This may impair respiration sufficiently to increase the susceptibility of crawfish to low dissolved oxygen concentrations encountered periodically in commercial crawfish ponds.

Abstract: Acineta nitocrae, a suctorian ciliate previously known from Ukraine, was discovered in western Lake Erie in October 1997 and in the Detroit River in May 1999. Individuals were found inhabiting the body surface of Nitocra hibernica and N. incerta, nonindigenous harpacticoid copepods. Acineta nitocrae infested 64 % of N. hibernica in Lake Erie, whereas in Ukraine it infested between 24 and 80 % of N. hibernica populations. In Lake Erie, N. hibernica copepods suffered lower suctorian burdens than conspecific individuals in native habitats in Ukraine. In Ukraine, this suctorian was also found on two other harpacticoid species - Nitocra lacustris and Canthocamptus staphylinus. The highest preference of A. nitocrae was established for N. hibernica. Acineta nitocrae individuals from Lake Erie and Ukrainian populations of N. hibernica were similar with respect to dimensions of the lorica and stalk, but differed significantly in terms of the length and width of actinophores, with highest values observed for Lake Erie. Occurrence of A. nitocrae in the Great Lakes may be related to the introduction of its hosts, N. hibernica and N. incerta.