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The marine microturbellarian diversity is scarcely known from the Pacific coastline of South America. The coastal margin of Peru is highly influenced by cold-water currents (Humboldt Current System). These cold-water currents play important roles in shaping the marine species diversity in this area. However, there are no previous records of marine microturbellarians for Peru. Here, we describe a new species of Rhabdocoela and report on five other species of marine microturbellarians for this country. Carcharodorhynchus giaae n. sp. (Kalyptorhynchia, Schizorhynchidae), can be identified based on the configuration of the proboscis lips and the male and female genital systems. The male copulatory organ lacks a cirrus, but has a funnel-like, curved stylet with three pairs of spines along it, which distinguishes this species from its congeners. The female system has a vagina with a sclerotized, heavily coiled structure - a feature not mentioned in any known species of the same genus. In addition, we describe noteworthy features for another rhabdocoel, Trigonostomum galapagoense (Dalytyphloplanida, Trigonostomidae). Finally, we provide new records for three rhabdocoel species (Alcha evelinae, Itaipusa divae, Utelga heinckei), one species of Fecampiida (Urastoma cyprinae), and an unidentified species of Prolecithophora.

Catenulida are mostly inhabitants of freshwater ecosystems, like ponds, streams, though the marine species are few (Larsson and Willems, 2010). About 110 species of catenulids are known worldwide, with most of the studies conducted in South America (Marcus, 1945a, 1945b; Noreña et al., 2005), North America (Kepner and Carter 1931; Nuttycombe and Waters, 1938) and Scandinavian Peninsula (Luther, 1960, Larsson and Willems, 2010; Larsson et al., 2008). The diversity of catenulids from India has not been studied intensively; however some reports on other turbellaria exists for the country (Annandale, 1912; Whitehouse, 1913; Kapadia, 1947; Basil and Fernando, 1975; Apte and Pitale, 2011; Kalita and Goswami, 2012; Venkataraman et al., 2015). The genus Stenostomum, however, has been studied extensively around the world with identification of over 60 species (Tyler et al., 2006-2016). This is first report of the genus from India. The present study was part of the project to catalogue the diversity of free living protozoan ciliates from the Hooghly stretch of the Ganga River during which the flatworms were found. The worms were studied based on the live observations, with recognition of characters which led to its identification. This study serves to fill knowledge gap in the freshwater flatworms from India.

Species of Macrostomum are present in almost all regions of the world. These flatworms occur in different kinds of environments, from freshwater to marine ecosystems. Although Peru is considered one of the megadiverse countries in South America, little is known about freshwater microturbellarians in this country. Here we report the presence of M. rostratum Papi, 1951 for the first time in Peru, in a coastal brackish water wetland, and that of M. quiritium Beklemischev, 1951 and M. tuba Graff, 1882 in an inland portion of a river near the city of Lima. All the species were studied alive. Comments on the habitat and associated fauna are given. Detailed information on the copulatory system is provided for M. rostratum; the male system has a bilobed seminal vesicle with thick walls and full of spindle-shaped sperm cells, and a stylet in the form of a solid curved inverted cone with a subterminal opening located on the concave side of the stylet. These findings led us to suggest that M. rostratum may exhibit a hypodermic mating syndrome. The three species of Macrostomum reported here are widespread and, although the diagnostic characters of the species are present, some morphological differences in the copulatory stylet suggest they are cryptic species.

Previous studies demonstrated complex architecture of the muscular system of Macrostomum species, especially in the rostrum area and the pharynx. However, little is known about the differences in muscular pattern between species of the genus. This study examines and compares the muscular systems of specimens belonging to three freshwater Macrostomum species (M. quiritium, M. tuba and M. velastylum), labeled with phalloidin-rhodamine and studied by confocal microscopy. Our results agree with the previous descriptions, confirming that the muscular patterns for the body wall, rostrum area, pharynx and caudal region differ among species. The muscles of the body wall follow the typical architecture, but the number of fibers in the species analyzed varies between dorsal and ventral surfaces, ranging from 80 to 100 fibers, this record being higher than previous observations. The arrangement of the fibers in the rostrum is complex, especially in the brain area. Macrostomum tuba and M. quiritium have a set of two muscles crossing at brain level and forming an "X," which is not evident in M. velastylum. We identified five different sets of fibers associated to the pharynx and mouth at ventral, medium and deep levels. These different sets are present in all three species studied. The caudal plate in M. tuba has an additional layer of diagonal fibers in the body wall, which is not evident in the other two species. The muscles of the reproductive system are independent of the body wall musculature in the species analyzed, but connected to the intestinal wall by specific fibers that may serve as an anchor. J. Morphol. 278:264-282, 2017. © 2016 Wiley Periodicals,Inc., (© 2016 Wiley Periodicals, Inc.)

The genus Pasipha Ogren & Kawakatsu, 1990 currently includes 22 species, most of them recorded in the Brazilian Atlantic Forest. Recently, Pasipha hauseri was documented in north-eastern Argentina, thus extending its distribution range. This paper reports new records of the genus Pasipha in the Interior Atlantic Forest ecoregion in Argentina, with the description of three new species: Pasipha atla sp. nov., Pasipha johnsoni sp. nov., and Pasipha mbya sp. nov. These new species exhibit similarities in internal anatomy, such as pharynx cylindrical, extrabulbar prostatic vesicle with folded walls and proximally forked, male atrium highly folded, being at least two times longer than the female atrium and with small folds in their proximal portion. However, they can be distinguished from each other mainly by the secretion types discharged into the prostatic vesicle as well as into the male and female atria. In addition, they have different colour patterns on the dorsal surface.

Two new species of Dalyellidae, Dalyellia callvucurai n. sp. and Gieysztoria namuncurai n. sp., are described from temporary freshwater environments in central Buenos Aires Province, Argentina. The ultrastructure of the stylets of both species is also described. The new species of the genus Dalyellia is the second species of the genus found in the neotropics and the first whose stylet has been studied with scanning electron microscopy. Gieysztoria namuncurai n. sp. joins the seven species of the genus known in Argentina. The ultrastructural characteristics of the stylet place it in the Inaequales group, with complex stylets.

In this work, two new species of the genus Macrostomum (M. velastylum n. sp. and M. puntapiedrensis n. sp.) are described from the littoral benthos of the Río de la Plata estuary, Argentina. This is the first description of members of the Macrostomidae from Argentina, and of a species documented from both limnic and brackish-water environments. Macrostomum velastylum differs from its congeners in the fine details of its stylet, which are described using a new technique for stylet isolation and observation (scanning electron microscope). This method provides new information on stylet structure relative to traditional whole-mount techniques. Macrostomum puntapiedrensis differs from others species of the M. orthostylum group in the length and morphology of the distal tip of the stylet. Further details are provided on additional macrostomids from Argentina, including potential conspecifics of M. vejdovskyi, M. viride, and M. lineare.

The free-living Platyhelminthes of the Amazon basin are poorly known. Presently only four turbellarian species have been mentioned from the Amazon river, a fact that confirms the lack of information on this kind of faunas in this huge basin. Three new species of Gieysztoria from Amazonian floodplain in Peru are described herein: G. chiqchi n. sp., G. kasasapa n. sp. and G. sasa n. sp. The samples were taken in the Pacaya-Samiria National Reserve (Peru) during September 2002. Besides the usual description of the stylet based on whole mounted specimens, we provide a complementary description using SEM, which allowed differentiation of the new species within the currently yet imperfect picture of the Amazonian turbellarian fauna. Although further research is desired, current findings are suggestive of high diversity of free-living Turbellaria in the surveyed region.

Temnocephala brevicornis Monticelli 1889, ectosymbiont of Hydromedusa tectifera Cope 1869, is reported for the first time for Argentina. Numerous temnocephalans from Arroyo Villoldo in the locality of Magdalena, Buenos Aires, Argentina were stained in toto to be studied. This commensal species in turtles was originally cited in association with Hydromedusa maximiliani (Mikan) and Hydraspis radiolata Mikan in Brazil. Afterwards, it was found on other fresh water turtle species in Brazil and Uruguay.