A Comprehensive Update on Helminth Parasite Biodiversity and Richness in Peruvian Amphibians

: This study aimed to comprehensively update and expand the knowledge on the diversity and richness of helminth parasites found in Peruvian amphibians. A systematic search was conducted across primary databases, encompassing both indexed and non-indexed articles, to compile the most recent data. As of the present study, a total of 83 distinct helminth taxa have been documented in association with 78 anuran species of the order Anura, marking a 176.7% increase from previously recorded ﬁgures. Nematodes exhibited the highest species richness, totalling 52 taxa (62.65%), followed by trematodes (21 taxa, 25.3%), acanthocephalans and cestodes (4 taxa each, 4.8%), and monogeneans (2 taxa, 2.4%). The overwhelming majority (85.5%) of the collected parasites (71 taxa) were identiﬁed as mature helminths, with the remaining 14.5% (12 taxa) in their larval stages. Notably, Cosmocerca brasiliense Travassos, 1925 (Cosmocercidae), and Physaloptera sp. (Physalopteridae) were the most prevalent nematodes, having infected the broadest range of host species. Rhinella marina Linnaeus, 1758 (Bufonidae), emerged as the anuran host with the highest diversity, harboring 17 distinct helminth species. These ﬁndings underscore the crucial role of helminth parasites in shaping amphibian ecosystems and their signiﬁcance as bioindicators of environmental health. Protecting both amphibian hosts and their associated helminth parasites is paramount, as it is intrinsically linked to the preservation of ecological equilibrium within these ecosystems.

Campião et al. [2] published a list of helminth parasites found in South American amphibians, reporting a total of 30 helminth species in Peru, which positioned Peru fourth in terms of helminth biodiversity.However, this review did not consider data published in national journals, many of which are difficult to access and have since discontinued publication or exist only in printed form in Peruvian libraries.
In recent years, there has been an increase in studies focusing on helminth parasites affecting amphibians in Peru [2][3][4][5][6][7][8][9].Despite this increasing attention, the available information remains limited.It is necessary to continue these studies to document the diversity of helminths, which may face extinction if their hosts become threatened.Such research also contributes to the understanding of parasitic infection dynamics, aids in the use of these parasites as bioindicators of contamination in a specific area, and informs the development of conservation strategies [10][11][12][13].
Given the dispersed nature of information related to Peruvian amphibian parasites, this study aims to consolidate these data to facilitate future research.The objective of this research is to compile a comprehensive checklist of helminth parasites infecting amphibians in Peru and analyze their diversity and richness.

Materials and Methods
The database was compiled through an extensive bibliographical review of helminth parasites reported from amphibians in Peru.Searches were conducted using several keywords on various platforms, including Zoological Records (Web of Knowledge), Biological Abstracts, Helminthological Abstracts, Google Scholar, Aquatic Sciences and Fisheries Abstracts, Pubmed, ScienceDirect, and Scopus.In each database, search words included "anuran parasites Peru", "amphibian parasites Peru", and amphibian helminths Peru".Additionally, articles published in Spanish that were not indexed in electronic databases were included.Dissertation, theses, and abstracts of scientific meetings do not constitute formal publications, and thus were not considered.The helminth parasite richness was quantified as the total number of parasite species observed in each host species.
This paper consists of two sections: The first section provides a list of helminth parasites, including information about their hosts, locality, site of infection, stage, and the corresponding references.The list of parasite-host associations is presented in phylogenetic order, beginning with the phylum Platyhelminthes (Monogenea, Trematoda, and Cestoda), followed by the phyla Nematoda and Rotifera.Helminth taxonomy follows specific reference for each group: Amin [14] for Acanthocephala, Anderson et al. [15] for Nematoda, Gibson et al. [16], Jones et al. [17], Bray et al. [18] for Trematoda, and Campião et al. [2], Cohen et al. [19] for monogenean, and Khalin et al. [20] for Cestoda.The second section presents a list of amphibian hosts, categorizing them based on their conservation status according to the IUCN (International Union for Conservation of Nature) and their associated parasites, organized by families and amphibian species in alphabetical order.Taxonomic information regarding amphibians is updated based on the AW database [1].
New records for Peru were also included in cases where helminth species were found in amphibian hosts at the Helminthological and Minor Invertebrates Collection at the Museum of Natural History, San Marcos University (MUSM), Peru, even if they had not been previously published in a scientific journal.The collection's acronym is provided alongside the record.Parasite and amphibian names were updated in accordance with recent publications.

Results
The results obtained in this research reveal that in Peru, there is available information on parasites associated with 78 anuran hosts distributed across 10 families: Bufonidae (10 spp.), Dendrobatidae (4 spp.), Hemiphractidae (6 sp.), Hylidae (27 spp.), Leptodactylidae (11 spp.), Microhylidae (3 spp.), Pipidae (1 sp.), Ranidae (1 sp.), Strabomantidae (8 spp.), and Telmatobiidae (7 spp.).The Bufonidae and Telmatobidae families exhibited the highest number of helminth parasites, with 49 and 29 taxa, respectively (Figure 1).Meanwhile, only one species of helminth parasite has been reported to infect Peruvian pipids and ranids so far.To date, a total of 83 taxa of helminth parasites from 28 families infecting amphibians have been recorded in Peru.Among the different types of parasites, nematodes exhibited the highest species richness (n = 52, 62,65%), followed by trematodes (n = 21; 25.3%), acanthocephalans (n = 4; 4.8%), cestodes (n = 4; 4.8%), and monogeneans (n = 2, 2.4%).These helminth parasites were associated with 60 nominal species and 23 undetermined species (Table 1) within the context of 78 species of anuran host.The overwhelming majority (85.5%) of the registered parasites (71 taxa) were identified as mature helminths, with the remaining 14.5% (12 taxa) in their larval stages.Sixty-eight percent (n= 53) of the amphibian hosts were found to harbor two or more parasites per host (Figure 2).To date, a total of 83 taxa of helminth parasites from 28 families infecting amphibians have been recorded in Peru.Among the different types of parasites, nematodes exhibited the highest species richness (n = 52, 62,65%), followed by trematodes (n = 21; 25.3%), acanthocephalans (n = 4; 4.8%), cestodes (n = 4; 4.8%), and monogeneans (n = 2, 2.4%).These helminth parasites were associated with 60 nominal species and 23 undetermined species (Table 1) within the context of 78 species of anuran host.The overwhelming majority (85.5%) of the registered parasites (71 taxa) were identified as mature helminths, with the remaining 14.5% (12 taxa) in their larval stages.Sixty-eight percent (n= 53) of the amphibian hosts were found to harbor two or more parasites per host (Figure 2).Table 2 displays information on the Anura hosts in Peru, including the mean richness of helminths, the maximum richness, the number and percentage of Anura families with larval parasites, and the percentage of amphibians listed in the IUCN conservation database.Of all the collected parasites, 85.5% (n = 71) were identified as mature forms of helminths, while 14.5% (n = 12) were in larval stages.Nematodes such as Cosmocerca brasiliense Travassos, 1925; Physaloptera sp.Rud, 1819; and Aplectana hylambatis (Baylis, 1927) exhibited a broad range of host species.Anurans such as Rhinella marina Linnaeus, 1758 (17 spp.);Rhinella margaritifera (Laurenti, 1768) (16 spp.); and Telmatobius jelskii (Peters, 1863) (16 spp.) were found to host the highest diversity of helminth parasites.Table 2 displays information on the Anura hosts in Peru, including the mean richness of helminths, the maximum richness, the number and percentage of Anura families with larval parasites, and the percentage of amphibians listed in the IUCN conservation database.Of all the collected parasites, 85.5% (n = 71) were identified as mature forms of helminths, while 14.5% (n = 12) were in larval stages.Nematodes such as Cosmocerca brasiliense Travassos, 1925; Physaloptera sp.Rud, 1819; and Aplectana hylambatis (Baylis, 1927) exhibited a broad range of host species.Anurans such as Rhinella marina Linnaeus, 1758 (17 spp.);Rhinella margaritifera (Laurenti, 1768) (16 spp.); and Telmatobius jelskii (Peters, 1863) (16 spp.) were found to host the highest diversity of helminth parasites.We compiled a total of 47 articles published over a 60-year period (1963 to 2023) on helminth parasites in amphibian hosts from Peru.The highest number of articles published on amphibian hosts falls within the period from 2000 to 2023, with 22 articles, representing 46.81% of the total.The second-highest period for article publication spans from 1980 to 1999, with 15 articles, accounting for 31.9% of the total.The earliest period, from 1963 to 1979, saw the publication of 10 papers, representing 21.27% of the total number of articles.Figure 3 displays the curve representing the total accumulated records of helminth taxa between 1963 and 2023 in Peruvian amphibians, while Figure 4 illustrates the curve depicting the accumulated number of new helminth taxa during the same period in Peruvian amphibians.
articles.Figure 3 displays the curve representing the total accumulated records of helminth taxa between 1963 and 2023 in Peruvian amphibians, while Figure 4 illustrates the curve depicting the accumulated number of new helminth taxa during the same period in Peruvian amphibians.articles.Figure 3 displays the curve representing the total accumulated records of helminth taxa between 1963 and 2023 in Peruvian amphibians, while Figure 4 illustrates the curve depicting the accumulated number of new helminth taxa during the same period in Peruvian amphibians.The regions in Peru where amphibian parasites were most frequently recorded included Cuzco (39.75%),Lima (32.53%),Junín (16.87%),Arequipa (15.66%), and Pasco (13.25%) (Figures 5 and 6).The most commonly infected organs were the intestine, small intestine, and urinary bladder, accounting for 28%, 19%, and 16% of recorded infections, respectively, across 11 different sites within the host amphibians.Regarding the conservation status of the host amphibians, as per the IUCN, 63 anuran species are classified as 'Least Concern' (LC), two as 'Near Threatened' (NT), three are 'Vulnerable' (VU), six are 'Endangered' (EN), three are 'Critically Endangered' (CR), and the status of two species remains undetermined.

Discussion
To date, a total of 83 helminth parasite taxa have been documented in 78 amphibian species in Peru, marking a significant increase of 176.7% in comparison to the earlier findings reported by Campião et al. [2], who registered only 30 taxa in Peru.Nematodes exhibit the highest species richness with 52 taxa, followed by digeneans with 21 taxa.Gonzalez and Hamann [60] reported 47 nematode taxa in 34 species of Argentinean amphibians.In contrast, Fernandez and Kohn [7] cited only 11 species of trematode parasites in Peruvian amphibians.This diversity pattern is consistent with that observed in helminth parasites of other anurans across South American countries [2].The majority of collected parasites in Peruvian amphibians were identified as mature helminths.Campião et al. [2] noted that adult nematodes are typically found in the gastrointestinal tract and are the most prevalent helminths in South American amphibians.Nematode species have been reported as adults and have dominated the helminth fauna of Argentinean amphibians [60].
In Peru, R. marina, followed by Rhinella margaritifera, hosted the most diverse range of helminth parasites (17 spp.and 16 spp., respectively).In South America, Leptodactylus latrans and Rhinella marina were the hosts with the highest number of reported helminth taxa, with 81 and 47 helminth species, respectively [2].In Argentina, the bufonid Rhinella schneideri (Werner, 1894) and the leptodactylid Leptodactylus bufonius Boulenger, 1894 displayed the highest species richness of parasitic nematodes (nine spp.) among Argentinean amphibians [60].In Mexico, anuran host species with the largest number of parasite species are R. marina with 49 species, L. vaillanti with 34, and Lithobates montezumae Baird, 1854, with 30 [13].Campião et al. [2] indicated that the genus Rhinella (Fitzinger, 1826) had among the highest numbers of helminths in South America [63].Rhinella marina and R. margaritifera are species complexes of semiaquatic toads found in tropical and subtropical South America and Central America.This species group is poorly delineated, with numerous undescribed cryptic species, which could explain the high diversity of helminth parasites infecting this group [63][64][65][66].Rhinella marina is known for having a highly diverse diet, primarily consisting of ants and Coleoptera larvae, which may contribute to the high diversity of helminth parasites in this anuran species [67].In South America, the most prominent families of anurans are Hylidae and Leptodactylidae, comprising nearly 60% of the species studied for helminth parasites [2].In Peru, Hylidae and Leptodactylidae also have the most hosts evaluated, but Bufonidae and Telmatobiidae are the families with the highest richness of helminth parasites.In Argentina, Bufonidae and Leptodactylidae exhibit the highest species richness of nematodes [60].
Regarding the conservation status of amphibian hosts, it was observed that three families, namely Telmatobiidae, Bufonidae, and Hemiphractidae, contained the highest percentages of host species considered of conservation importance.Understanding the diversity of parasites in amphibians, particularly those species listed as endangered, is crucial.Helminth parasites are integral components of biodiversity, and their extinction can occur in tandem with that of their hosts.
Among the 78 amphibians surveyed for helminths in Peru, there were no caecilian or caudata species.Remarkably, nearly 88% of Peruvian amphibians have not been subjected to studies on helminth parasites.The helminth parasite fauna is a crucial component of the natural history of amphibian hosts and can serve as a valuable and predictive tool for understanding parasite-host interactions and supporting biodiversity conservation research [13,[68][69][70][71][72][73][74][75].However, further research in this area is warranted.

Conclusions
This comprehensive update on helminth parasite biodiversity and richness in Peruvian amphibians provides valuable insights into the diversity and distribution of helminth parasites in this region.This research has important implications for conservation, as understanding the diversity and distribution of helminth parasites can aid in the development of conservation strategies and the use of parasites as bioindicators of contamination in specific areas.Additionally, the study highlights the potential threat of extinction faced by helminth parasites if their hosts become threatened.Overall, this study represents a significant contribution to the knowledge of helminth parasite biodiversity in Peruvian amphibians and underscores the need for further research in this field to protect both the amphibian hosts and their associated parasites.

Figure 1 .
Figure 1.Helminth parasite species distribution among amphibian families in Peru.

Figure 1 .
Figure 1.Helminth parasite species distribution among amphibian families in Peru.

Figure 2 .
Figure 2. Current known richness of helminth parasites in amphibian hosts from Peru.

Figure 2 .
Figure 2. Current known richness of helminth parasites in amphibian hosts from Peru.

Figure 3 .
Figure 3. Curve of the number of accumulated total records of helminth parasite taxa between 1963 and 2023 in amphibians of Peru.

Figure 3 .
Figure 3. Curve of the number of accumulated total records of helminth parasite taxa between 1963 and 2023 in amphibians of Peru.

Figure 3 .
Figure 3. Curve of the number of accumulated total records of helminth parasite taxa between 1963 and 2023 in amphibians of Peru.

Figure 4 .
Figure 4. Curve of the number of accumulated new helminth parasite taxa between 1963 and 2023 in amphibians of Peru.

Figure 5 .
Figure 5. Areas with records of monogeneans, acanthocephalans, and cestodes in amphibian hosts from Peru.

Figure 6 .
Figure 6.Areas with records of digeneans and nematodes in amphibian hosts from Peru.

Figure 6 .
Figure 6.Areas with records of digeneans and nematodes in amphibian hosts from Peru.

Table 1 .
Total of nominal and undetermined parasite species of amphibia from Peru according to the taxonomic group.

Table 1 .
Total of nominal and undetermined parasite species of amphibia from Peru according to the taxonomic group.