Aline Aguiar

The inclusion of parasites in inventories has provided relevant information on the knowledge of biodiversity. Integrating accurate taxonomy and species identity of both hosts and parasites can result in valuable insights into the association’s evolutionary relationships, geographic distribution, and dynamics. Besides the risk of diseases related with some parasites, herein we also highlighted the great diversity revealed in parasite communities associated with amphibians and reptiles, varying from unicellular to metazoan organisms occupying numerous tissues throughout the host’s body. To be aware of this diversity, the first step is to implement taxonomic studies performing appropriate methods for collecting and preserving specimens. Here, we aim to provide a useful hands-on guide to parasitological data collection from amphibians and reptiles. We write especially for those aiming to include parasitological data in their sampling, and for herpetologists and naturalists who already collaborate with parasitologists. We also provide some fundamental knowledge on the morphology and life cycle of the main parasites associated with herps, as well as protocols and tips for better collecting and preserving each type of parasite.

Biological inventories are essential tools for understanding parasite diversity. In this study, we describe the helminth parasite communities associated with anuran amphibians from five localities within the Caatinga domain of Northeastern Brazil. A total of 1,198 individuals, belonging to 22 species and six anuran families (Bufonidae, Hylidae, Leptodactylidae, Microhylidae, Odontoprhynidae, and Phyllomedusidae), were examined. Of these, 629 specimens (52.5%) were parasitized, and 27,004 helminths were recovered. The helminths represented 34 taxa, including 24 Nematoda, 7 Digenea, 1 Cestoda, and 2 Acanthocephala. We present parasitological descriptors such as prevalence, abundance range, infection site, and life stage. Additionally, we report 18 new host-parasite records and provide updated data on geographical occurrence. Our findings emphasize the importance of regional surveys in expanding knowledge on host-parasite interactions and in highlighting hidden components of biodiversity within the Caatinga biome.

We described Creptotrema cambeve n. sp. from the intestine of the Brazilian catfish Cambeva davisi (Haseman, 1911) (= Trichomycterus davisi) based on integrative analyses using morphological and molecular approaches. Creptotrema cambeve n. sp. closely resembles morphologically Creptotrema paraense Vicente, Santos & Souza, 1978, which was described from a siluriform fish in Northern Brazil; however, the two species differ mainly in the oral and ventral sucker sizes and the distribution of the vitellaria. The phylogenetic analyses of the 28S rDNA placed the sequences of the new species in a monophyletic clade together with all other Creptotrema spp. and as sister taxon of Creptotrema cruste Alcantara, Ebert, Ferreira-Silva, Forti, Morais, Pérez-Ponce de León & Silva, 2024, a parasite from a Brazilian anuran. Genetic divergences between the new species and other Creptotrema spp. varied from 0.2% to 4.3%, further corroborating the distinction of the new taxon. Creptotrema cambeve n. sp. is the 18th nominal Creptotrema species known from South America and the 22nd erected in the genus. This is the first study reporting a trematode in Cambeva spp. hosts and the second parasitological survey carried out for Ca. davisi, a poorly known small endemic fish.

Diversity of Creptotrema was investigated using morphological and molecular tools, including data for Creptotrema creptotrema (type-species). Three new species, parasites of Brazilian fishes, are described: Creptotrema conconae n. sp. (type-host, Imparfinis mirini Haseman), Creptotrema schubarti n. sp. (type-host, Characidium schubarti Travassos) and Creptotrema megacetabularis n. sp. (type-host, Auchenipterus osteomystax (Miranda Ribeiro)). The diagnosis of the genus was amended to include new features. The new species differ from each other mainly in terms of body shape, relative sucker size, and testes position. DNA sequences were obtained from Creptotrema spp. from Brazil, including 28S, ITS and COI. Genetic divergences among the new species and C. creptotrema varied from 2.1 to 5.2% (21–49 bp) for 28S, and 6.6 to 16.4% (21–45 bp) for COI. Phylogenetic analysis (28S) placed the newly generated DNA sequences of Creptotrema in a clade (Creptotrema clade sensu stricto) composed of C. creptotrema, the new species described herein, and all species previously described as Auriculostoma, revealing that Auriculostoma is best interpreted as a synonym of Creptotrema based on the principle of priority of zoological nomenclature. Creptotrema funduli, the single sequence of the genus previously available, was not grouped within the Creptotrema clade sensu stricto, suggesting the need for reevaluation of the taxonomic status of this species. Our results showed that Creptotrema represents a monophyletic genus of trematodes widely distributed across the Americas, which currently comprises 19 valid species of parasites of teleosts and anurans.

Biodiversity of anuran endoparasites from a transitional area between the Atlantic Forest and Cerrado biomes in Brazil: new records and remarks

Rhabdias pocoton. sp. is herein described from the lungs of the swamp frogPseudopaludicola pocotoMagalhães, Loebmann, Nogueira, Kokubum, Baptista, Haddad & Garda, 2014, from the Caatinga biome in the state of Ceará, in north-eastern Brazil. The new species is characterized by a body that dilates posteriorly, six small lips (protuberances) and two rounded lateral expansions of cuticular inflation on the anterior end, each containing an amorphous gland-like structure inside and a short and conical tail. Additionally, molecular analysis and comparison of the partial mitochondrial cytochromecoxidase I sequence ofR.pocoton. sp. revealed genetic divergence between the new species and the sequences ofRhabdiasspp. previously deposited in GenBank. Phylogenetic analysis grouped the new taxon into theR. pseudosphaerocephalaspecies complex +R. glaurungiclade. The new discovery represents the 19th species ofRhabdiasspp. described in the Neotropical region, the ninth in Brazil and the first species ofRhabdiasfound parasitizing South American frogs of the genusPseudopaludicola, as well as the first Caatinga biome species ofRhabdias.

Habitats characterized by geographic isolation such as islands have been studied using different organisms as models for understanding the dynamic and insular patterns of biodiversity. Determinants of parasite richness in insular host populations have been conducted mainly with mammals and birds, showing that parasite richness decreases in insular areas. In the present study, we predicted that the type of environment (insular or continental) can influence the richness, diversity and abundance of parasites associated with the endemic frog Haddadus binotatus (Spix, 1824). We sampled frogs in two insular and two mainland fragments to survey their helminth parasites. The total richness was composed of 15 taxa of Nematoda and two of Acanthocephala, and the community composition of the two islands had more similarities between them than the two mainland localities. The insular effect was positive for richness and abundance of helminths, and no significant effect was observed on helminth diversity – even the mean diversity presented high numbers for the islands. We presumed that insular hosts could have lost some parasites in the colonization process when these continental islands were separated from the mainland, approximately 11,000 years ago. However, the high richness and abundance on islands can be explained by an epidemiological argument, which considers high population density due to insularity and other features of the host as factors that increase parasite transmission success among individuals.

Lungworms from the genusRhabdiasare common parasites of amphibians and reptiles distributed worldwide. To assess the diversity ofRhabdiasspp., we performed molecular analyses of 35 specimens sampled in different regions of Brazil. Molecular analyses were based on the internal transcribed spacer (ITS), large subunit (28S) ribosomal and the cytochrome oxidase I (COI) mitochondrial genes. DNA sequence divergence was compared among ribosomal and mitochondrial genes, analyses using the general mixed Yule‐coalescent (GMYC) method based on the COI gene were used to identify possible cryptic diversity, and phylogenetic analyses using concatenated ITS and 28S ribosomal genes were used to test the monophyly of Rhabdiasidae. We revealed five morphospecies:R.cf.stenocephala,R. breviensis,R. pseudosphaerocephalaand two new species,Rhabdiassp.4 andRhabdiassp.5. DNA sequence levels of divergence among genes ITS, 28S and COI were compared, and the efficiency of the molecular markers to identify species (ITS and COI) and lineages (COI) was tested. GMYC was assigned to 17 well‐supported clades (i.e., 17 species), and cryptic diversity was detected in the Neotropical region as evidenced by the multiple lineages inR. breviensisandR. pseudosphaerocephala. In addition, our results suggest evidence for host–parasite cophylogeny in theR. pseudosphaerocephalacomplex and dispersal events among their populations. Phylogenetic analyses supported the monophyly of Rhabdiasidae and improved the resolution of main clades.Rhabdias breviensisis closely related toRhabdiascf.africanus,Rhabdiascf. stenocephala,R. pseudosphaerocephala,Rhabdiassp.4 andRhabdiassp.5 grouping together in a main clade with Neotropical‐related species. The large geographical distribution appeared to be a phylogenetic pattern among the species ofRhabdiasfrom the neotropics.

Species of Stratiodrilus are ectocommensals of freshwater decapod crustaceans, and the genus is also the most speciose within the family Histriobdellidae. However, a global review of the species of Stratiodrilus and their hosts has not been performed in nearly two decades. Based new field collections in Brazil and a literature search, we present a list of Stratiodrilus species and their hosts. We searched for host and occurrence records in papers of species descriptions, review papers and specialized databases. Forty-one host records were summarized worldwide. All host taxa were freshwater decapod crustaceans belonging to Aegla, Astacoides, Astacopsis, Cherax, Parastacus, Samastacus, and Trichodactylus. In addition, we report four new host records for Stratiodrilus circensis, and found Aegla lata as the northernmost host record for this polychaete species. Stratiodrilus circensis also had the largest number of different host species. The greatest species richness of Stratiodrilus is found in the Neotropical region, although members of this genus are also found in Australia and Madagascar associated with crayfishes. Aegla was the most reported host genus associated with species of Stratiodrilus. We provide an updated list to the known species of Stratiodrilus and also discuss the distribution of these histriobdellids.