Temnocephalan epibionts (Platyhelminthes, Temnocephalida) on mollusks from Pantanal wetland, Brazil

Abstract

Temnocephala iheringi Haswell, 1893 was recorded in Marisa planogyra Pilsbry, 1933 and Pomacea maculata Perry, 1810. Also, Temnocephala amatoi sp. nov. was described from Pomacea scalaris (d'Orbigny, 1835). The mollusks were collected from temporary ponds at Ypiranga Farm, Poconé, Mato Grosso, Brazil. The new species differs from six other species of Temnocephala Blanchard, 1849 epibionts on molluks by having the following combination of characters: 1. a short and curved cirrus; 2. a narrow introvert with approximately 22 longitudinal rows of spines with 13 spines each; 3. internal spines with a narrow base, longer on the base of the introvert and smaller in the distal portion; 4. a single and asymmetrical vaginal sphincter and; 5. elliptical, longer than wide epidermal 'excretory' syncytial plates (EPs) with a excretory pore displaced to the anterior portion of the plate. Temnocephala lamothei Damborenea & Brusa, 2008 has a curved cirrus, similar in size to the new species' cirrus. However, the introvert is not swollen with an oblique proximal margin, marked with a thickened oblique ring and two rows of 45-50 thin spines, differentiating the species from T. amatoi sp. nov. When comparing the specimens of T. iheringi from Poconé with the redescription of the species from Southern Brazil previously published by the authors, we found significant intraspecific variation in the size of the adhesive disk, pharynx length, shaft and introvert length, spines of the introvert length, as well as differences in the number of paranephrocytes. The size of the EPs and, when comparing with published data from Uruguayan and Argentinean specimens, the body size also showed important differences. We hypothesize that the host species may be the cause of the intraspecific variations found. Overall, the record of two new hosts for T. iheringi, the intraspecific variation found in this species and its geographical distribution being expanded 418 km further to the north, together with the description of a new species, add acknowledgment to the Rhabdocoela fauna in the Brazilian Pantanal.