The epidermal ‘excretory’ syncytial plates in species of Temnocephala (Platyhelminthes, Temnocephalida) - Proposal of a new methodology

Abstract

The epidermis of temnocephalids is formed by a mosaic of syncytial plates as revealed by electron microscopy and/or 5% silver nitrate impregnation. The variable form and size have been observed but the value of the epidermal ‘excretory’ syncytial plates (EPs) in the identification of Temnocephala species never were proper discuss. Ten species of Temnocephala were studied using images taken with a scanning electron microscope (SEM), describing a morphometry method to allow the comparison, thus, evaluating the EPs as a specific character in the identification of species of Temnocephala. The measurements (length of the anterior and posterior portions of the plate relative to the excretory pore, width of the internal and external limits, length of the portion exceeding the tentacles, total width, and total length) were obtained using AxioVision® Zeiss LWE 4.7.2 (AVZ) software. The EPs of the species tested were different revealing unique characteristics thus allowing their use as specific characters within Temnocephala. There was a pattern for each host group (Mollusca, Crustacea, Insecta, and Chelonia); the exceptions were the crustacean species and one insect species. The intra-specific variation study in Temnocephala trapeziformis demonstrated that this character varied minimally within the species. The SEM images and the AVZ software measurements were positive for the characterization of species of Temnocephala. The cirrus remained the most important specific character within Temnocephala. The traditional morphometric method was sufficient to demonstrate several specific EP characteristics, but new EPs should always be clearly described and illustrated following the now proposed methodology for Temnocephala species identification.