The viruses associated with bats have generated significant concern; however, there is limited knowledge regarding the endoparasites that affect these mammals. This study involved the collection of seven nematode specimens (three males and four females) from the intestines of Hipposideros armiger in Shaoguan City, Guangdong, China. Next-generation sequencing was employed to obtain the mitochondrial DNA (mtDNA) genome, which was determined to be 14,130 base pairs in length. The mitochondrial genome comprised 12 protein-coding genes, 21 tRNA genes, 2 rRNA genes, and an AT-rich non-coding region. Phylogenetic analyses based on mtDNA sequences indicated that the nematode forms a sister clade to Nematodirus, exhibiting only 74% nucleotide identity. In contrast, the nuclear ITS1 gene demonstrated a high degree of nucleotide identity (98.6%–98.8%) with Durettenema guangdongense. Consequently, the parasitic nematode identified from H. armiger is likely to belong to the genus Durettenema and has been designated as Durettenema sp. 888. Furthermore, an epidemiological investigation revealed the presence of the parasitic nematode infections in H. armiger collected from Guangdong, Guangxi, and Guizhou Provinces. Given the widespread distribution of H. armiger and their tendency to inhabit areas in close proximity to human dwellings, the influence of parasite prevalence on bat population numbers and potential for human and domestic animal transmission of this pathogen warrants further investigation.

Stephanofilaria is a genus of nematodes that cause ulcerative dermal lesions in large mammals. However, there is a dearth of knowledge on the molecular genetics of Stephanofilaria species infecting critically endangered rhinoceros. This study employed genetic barcoding genes to identify Stephanofilaria species and to determine its genetic diversity and evolution. Phylogenetic analyses on partial genes of the second internal transcribed spacer Ribosomal DNA (ITS-2) and cytochrome c oxidase subunit 1 (Cox-1), revealed a 77% and 93% bootstrap support at the Cox-1 and ITS-2 loci respectively to a clade containing previously identified Stephanofilaria species. Morphological examination also confirmed features diagnostic of Stephanofilaria dinniki previously known to infect rhinoceros. Gene diversity of Cox-1 was 0.931 ± 0.030 and 0.579 ± 0.104 for the ITS-2, whereas nucleotide diversity was 0.008 ± 0.002 and 0.00197 ± 0.0016 for the Cox-1 and ITS-2 genes respectively. Neutrality tests (Fu and Li’s D* and Fu and Li’s F*) were significantly negative (p<0.05) at all loci, whereas Tajima D and Fu’s FS were each statistically significant (p<0.05) at the Cox-1 and ITS-2 loci respectively. The high gene diversity, low nucleotide diversity and negative neutrality tests are consistent with positive selection at the Cox-1 gene. Stephanofilaria infection among rhinoceros is currently restricted to highland sanctuaries compared to a widespread distribution in both lowlands and highlands in the 1960s suggesting an adaptation to vectors thriving in cooler highland temperatures. This is the first genetic identification of S. dinniki, in rhinoceros and will aid in diagnosis, treatment, studies, and rhinoceros conservation.

In this study, we investigated the diversity and survival of aestivating snails in dry-season rice paddies, focusing on their role as intermediate hosts for trematodes. A total of 1,159 snails from various families were collected and analysed, revealing nine species, primarily from the Bithyniidae family, with Bithynia siamensis siamensis being the most abundant. Of the nine species collected, the most common species, B. s. siamensis, exhibited a relatively high survival rate of 81.5% throughout the three-month dry period post-harvest, whereas the remaining eight species had survival rates below 24.0% (0–23.1%). Four snail species, B. s. siamensis, Filopaludina martensi martensi, F. sumatrensis polygramma, and F. doliaris, were found infected with larval trematodes, with an overall prevalence of 8.46% (57/674). The larval trematodes identified were categorized into four types: echinostome metacercaria, Thapariella anastomusa metacercaria, unidentified metacercaria, and unidentified rediae. These findings demonstrate that trematode infections can persist in aestivating snails despite the challenging conditions during the dry season, emphasizing the potential of aestivating snails to act as vectors for trematode transmission in agricultural settings. This underscores the need for effective management strategies to mitigate the risks associated with trematode transmission.

The techniques employed to collect and store trematodes vary between research groups, and although these differences are sometimes necessitated by distinctions in the hosts examined, they are more commonly an artefact of instruction. As a general rule, we tend to follow what we were taught rather than explore new techniques. A major reason for this is that there are few technique papers in the published literature. Inspired by a collaborative workshop at the Trematodes 2024 symposium, we outline our techniques and processes for collecting adult trematodes from fishes and discuss the improvements we have made over 40 years of dissections of 20,000+ individual marine fishes. We present these techniques for two reasons: first, to encourage unified methods across the globe, with an aim to produce optimally comparable specimens across temporal periods, across geographic localities, and between research groups; and second, as a resource for inexperienced researchers. We stress the importance of understanding differences in host biology and the expected trematode fauna, which ultimately enables organised and productive dissections. We outline our dissection method for each key organ separately, discuss handling, fixation, and storage methods to generate the most uniform and comparable samples, and explore ethical considerations, issues of accurate host identification, and the importance and potential of clear record keeping.

Steringotrema microacetabularis Suriano & Martorelli, 1983 (Fellodistomidae) was described from the flounder Paralichthys orbignyanus. Later, it was redescribed, based on new material from the same host and type locality, and reconsidered as Bacciger microacetabularis (Baccigeridae). The main difference noted in the redescription was the presence of spines on the body. However, the lack of DNA data made confirming the true affiliation of this digenean challenging. New specimens sampled from P. orbignyanus allowed us to sequence the 28S, ITS, and COI genes. Fresh specimens were stained to compare their morphology with the holotype and voucher specimens. The digeneans found correspond with those reported from Mar Chiquita, described as B. microacetabularis (=S. microacetabularis). Genetic analyses clustered the newly sequenced individuals within the Cryptogonimidae, showing relationships with Oligogonotylus manteri, Tabascotrema verai, and Caecincola parvulus (28S); T. verai, Lobosorchis spp., Euryakaina manilensis, and Metadena marina (ITS); and Siphoderina spp. (COI). After comparing the species with cryptogonimids lacking spines in the oral sucker, a new genus, Surianotrema n. gen., is described. This genus increases the number of cryptogonimid genera known in South America to seven – three in freshwater and four in marine environments – with Surianotrema n. gen. being the first to be sequenced. New sequences from other South American cryptogonimids are necessary to better understand the phylogenetic relationships between genera within this family, particularly in South America.

Gyrodactylidae Cobbold, 1864 is a monophyletic family of hyperviviparous species, with 36 genera and approximately 700 species. Here, we focused on one of these genera – namely Scleroductus Jara & Cone, 1989 – characterizing its morphological variation systematically and testing its phylogenetic position in relation to other genera in the family. We collected and describe two new species of monogenean parasites of Scleroductus infecting Neotropical freshwater catfishes in Mexico. Scleroductus veracruzano n. sp. infects Guatemalan chulín, Rhamdia guatemalensis in Veracruz, while Scleroductus oaxaqueno n. sp. infects filespine chulín, Rhamdia laticauda in Oaxaca, Mexico. Sequences of the internal transcribed spacer (ITS rDNA) and 18S rDNA were generated for both species. Phylogenetic hypotheses based on maximum likelihood and Bayesian inference analyses of 18S rDNA indicate that the two new Mexican taxa are closely related to each other, and both appear as sister species to an undescribed but molecularly characterized Scleroductus sp. infecting South American catfish, Rhamdia quelen in Brazil. Our analyses confirm the placement of Scleroductus spp. within the monophyletic family Gyrodactylidae, whose sister clade is the Oogyrodactylidae. Within Gyrodactylidae, Scleroductus spp. form a clade sister to a well-supported clade composed by members of the genera Ieredactylus, Gyrodactyloides and Laminiscus.

This report provides an overview of available data on the ultrathin structure and the mechanisms of formation of cysts around acanthocephalans of the classes Palaeacanthocephala and Archiacanthocephala in intermediate hosts. In most of the described cases, the cyst is bi-layered, consisting of an outer layer that is relatively thick and vesicular, and an underlying layer that is thin and amorphous. In acanthellae of some species, a lamellar layer is observed on the cyst surface, which degrades presumably at the cystacanth stage. Three probable mechanisms of cyst formation in acanthellae of different species have been identified. The first and second mechanisms involve the border of microvilli that develops on the tegument surface. In acanthellae of the first group, the cyst’s vesicular layer is formed by detachment of fragments or small vesicles from microvilli, a process resembling the micro-apocrine secretion, while the amorphous layer is composed of electron-dense material released from invaginates of the tegument’s outer membrane and the remaining microvilli. In acanthellae of the second group, the cyst is single-layered and formed presumably of whole microvilli separated from the tegument. Since acanthellae of the third group lack microvilli on the tegument surface, the vesicular layer of the cyst is formed of a few small vesicles and amorphous material synthesized deep in the tegument and in large vesicles transported to the parasite’s surface. The amorphous, electron-dense layer of the cyst is formed in the same manner as in the first group, but without microvilli.