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A new Neotropical temnocephalan species is described from Aegla jarai Bond-Buckup & Buckup, 1994 from Santa Catarina, Brazil and recorded on Samastacus spinifrons (Philippi, 1882) from five locations (Región de Biobío, Región de la Araucanía, and Región de Los Lagos) in Chile. Temnocephala catarinensis sp. nov. differs from 10 other species of Temnocephala Blanchard, 1849 epibionts on Aeglidae Dana, 1852 and/or Parastacidae Huxley, 1879 by having the following combination of characters: 1. a long and slightly curved cirrus; 2. an introvert with two distinct portions, a proximal one with grooves and no spines and a distal one with small spines with a strong base; 3. a single vaginal sphincter, well-developed and slightly asymmetrical; 4. a very short vagina with a weak muscular wall; 5. an almost triangular epidermal 'excretory' syncytial plates, with external margin in half circumference, sometimes reaching laterally the margin of body. The specimens of S. spinifrons have slightly larger measurements than specimens of A. jarai. The cirrus total length and introvert length, despite being larger, have almost the same number of spines in the distal portion. The shape of the EPs is similar in specimens from both hosts. The new species share some similarities with Temnocephala axenos Monticelli, 1898, Temnocephala mexicana Vayssière, 1898, Temnocephala kingsleyae Damborenea, 1994, and Temnocephala mertoni Volonterio, 2007, but the characters that differentiate them are presented and discussed. The new species has a wide geographic distribution represented by a large distance between the sampled locations (2,637 km) and separated by the Andes. This is not the only species with very distant records from each other as Temnocephala iheringi Haswell, 1893 and T. axenos or separated by the Andes as Temnocephala chilensis (Moquin-Tandon, 1846) and Temnocephala monticellii Ponce de León, Rudolph and Volonterio, 2020.

Temnocephala axenos Monticelli, 1898 was described based on specimens from an unidentified host collected in Blumenau, Santa Catarina, Brazil. Information about type locality was imprecise and the host was later identified as Aegla laevis (Latreille, 1818). However, it is known that A. laevis is not present on the eastern side of the Andes. Also, only histological preparations from one specimen studied by Monticelli are currently available in the Museum für Naturkunde Berlin, but it showed none of the taxonomic characters needed for the characterization of the species. Although the updated description of the species based on Uruguayan specimens, neither the author nor the several previous studies about the species showed a search for the type material, a resolution for the misidentification of the type host or the imprecise type locality due to the subsequent geographical division of the municipality cited in the description. The Uruguayan specimens were not even geographically close to the type locality and a neotype was not designed to validate the species' taxonomic status again. Specimens from Santa Catarina and Paraná States, Brazil, were studied, as well as restudied Argentinean specimens. The new data were compared with the update description of the species. The historical background and the discussion about geographical origins and hosts of the species, as well as a designation of a neotype, allow comparative material of the type locality and type host to exist, eliminating doubts about the identification of T. axenos.

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.