A new species of Hedruris (Nematoda: Hedruridae) from freshwater turtles, its life cycle and biogeographic distribution of the genus

Closing the knowledge gap: Helminth parasites of freshwater turtles from the Chaco-Pampa Plain, Southern South America

Six species of freshwater turtles dominate the Chaco-Pampa Plain in southern South America and their parasites have been relatively understudied, with most records concentrated in Brazil. Particularly in Argentina, there are only scattered records of parasites for most of the turtles that inhabit the region, leaving a large knowledge gap. The purpose of the present contribution is to increase the knowledge of the internal parasites of six species of freshwater turtles from Argentina, after 15 years of fieldwork, by providing new hosts and additional geographic records for many host-parasite relationships. Some molecular sequences of the studied parasites were provided as a tool for better species identification. We processed 433 stomach and fecal samples from live individuals and visceral and soft tissue samples from 54 dissected turtles collected from a wide range and different ecoregions. We found 6230 helminths belonging to 18 taxa (one cestode, 11 digeneans and six nematodes). Fourteen new parasite-host associations are reported here, and for the first time parasites are recorded for Phrynops williamsi. This work contributes significantly to the knowledge of the parasitofauna in freshwater turtles in Argentina, providing a detailed list of parasites present in each turtle species and reporting molecular characters for future studies.

A redescription of Hedruris moniezi Ibáñez & Córdova, 1976 (Nematoda: Hedruridae), an endoparasite of the Titicaca water frog Telmatobius culeus (Garman, 1876) (Anura: Telmatobiidae), with comments on all other known Hedruris species in Peru

Hedruris moniezi Ibáñez & Córdova, 1976 (Nematoda: Hedruridae) was described using light and scanning electron microscopy (SEM) based on specimens collected from the stomach of Telmatobius culeus (Anura: Telmatobiidae) in Peru. We observed some characteristics not reported previously, including sessile and pedunculated papillae and amphid on the pseudolabia, bifid deirids, morphology of the retractable chitinous hook, morphology and arrangement of the plates on ventral surface of the posterior end of the males, and arrangement of caudal papillae. Telmatobius culeus represents a new host of H. moniezi. In addition, H. basilichtensis Mateo, 1971 is considered to be a junior synonym of H. oriestae Moniez, 1889. A key to valid species of Hedruris in Peru is provided.

A new species of Hedruris Nitzsch, 1821 (Nematoda: Hedruridae) parasitic in eel Synbranchus marmoratus Bloch (Synbranchiformes: Synbranchidae) from Argentina, Neotropical Region

During a parasitological survey, specimens belonging to the genus Hedruris (Nematoda: Hedruridae) were found in the stomach of Synbranchus marmoratus Bloch from the Paraná Guazú River, Paraná River basin (Argentina). Comparative morphological studies with its congeners showed that these nematodes belonged to a new species, herein described as Hedruris anguila sp. nov. The new species can be distinguished from remaining Hedruris species by the pseudolabia size, the morphology and size of spicules, the length of female caudal hook, the shape and size of eggs and the particular morphology of the male tail. Hedruris anguila sp. nov. closely resembles Hedruris bifida Rossin & Timi, 2016 and H. suttonae Brugni & Viozzi, 2010, both also described from fish hosts, in the arrangement of caudal papillae and morphology of eggs, but differ in the size of female hook and spicules, and the number of caudal papillae in males. The main morphological features, host range and geographical distribution of all species in the genus Hedruris species are analyzed and discussed. This is the first report of a representative of the family Hedruridae parasitizing a species of Synbranchidae and the eleventh report of the genus Hedruris for a fish host. The number of valid species of Hedruris described was increased to 26, including the new species; 11 for the Neotropical Region and represent the third species found in fish host from Argentina. Based on morphological analysis, the speciation process probably occurred first in Gondwana and the non-mammillated eggs could be an ancestral morphological character. The diet of Synbranchus marmoratus and values of prevalence and mean intensity could indicate that this host species is a true definitive host for this nematode.  

Gastrointestinal helminths associated with three species of freshwater turtles in the Pampa biome, southern Brazil

Maintenance of the life cycle of a wide diversity of helminths depends on the aquatic environment. Freshwater turtles are considered one of the main groups in these ecosystems due to their high density and biomass. However, there is little information on the infection parameters of helminths associated with the Chelidae species Hydromedusa tectifera, Phrynops hilarii, and Acanthochelys spixii that occur in the Pampa biome. Therefore, this study aimed at analyzing the gastrointestinal helminth assemblage of the three species. Analyses showed that A. spixii was associated with 11 helminth taxa while P. hilarii and H. tectifera were parasitized by eight taxa each. The gastrointestinal helminth assemblage of A. spixii and H. tectifera showed high similarity by the Morisita index. Infections suggest that the helminth fauna is directly related to the diet of the hosts, since A. spixii, P. hilarii, and H. tectifera are generalist and/or opportunistic with diets composed of various invertebrates, which, in turn, are part of the life cycles as intermediate hosts of most of the identified helminths. Thus, this study highlights not only the importance of helminthological research for the understanding of the biology of host organisms, but also the need for conservation of flooded areas characteristic of the Pampa biome, which is essential to maintain the diversity of the ecosystem.

Seasonal variation of Hedruris dratini (Nematoda) parasitizing Hydromedusa tectifera (Chelidae), with focus on host’s torpor state

Background

The aim of this study was to analyze the seasonal distribution of the nematode Hedruris dratini parasitizing the South American Snake-necked turtle Hydromedusa tectifera and the amphipod Hyalella spp. in an urban stream. We focused on understand which strategies parasite population displays to get through the host’s hibernation period.

Results

The highest prevalence and abundance of H. dratini were found in summer. The parasitic load was lower in winter, however there were no significant differences when it was compared with autumn and spring. Generalized linear model identified the temperature as a determining factor for the presence of parasites in turtles.

Conclusions

Our results indicate that, beside turtles enter in a diapause state, the life cycle of H. dratini never stop throughout the year, being a continuous transmission between both the intermediate and final host throughout the year. Turtles feed and become infected with parasite larvae even in winter although with a lower ingestion rate.