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The colubrid snakes of the genera Gongylosoma Fitzinger, 1843 and Liopeltis Fitzinger, 1843 are distributed across south and southeast Asia with five and eight nominate species, respectively. Despite their wide distribution, members of these genera are among some of the least-known colubrids. The two genera were considered synonymous in the past only to be separated later, and are defined on rather nebulose characters with a lack of support from molecular data. To test the monophyly of the two genera, we generated molecular data for the type species of Gongylosoma and species representing the two genera, including samples of Liopeltis rappii (Günther, 1860) from the western Himalayas. Results recovered paraphyly of Liopeltis , especially with regard to the genus Gongylosoma. Morphological data supports recognizing the western and eastern populations of L. rappii as two distinct species. The findings from our integrative taxonomic approach advocate establishing a new genus to embody Liopeltis rappii and a new allied species from the central and western Himalayas. A rediagnosis and revised classification of the genera Gongylosoma and Liopeltis is presented. The results further hint at cryptic diversity across members of the two genera, warranting scrutiny of the most widespread members of the group.

The genus Tanqua Blanchard, 1904, infests reptiles, particularly those inhabiting aquatic environments. This study examined a population of rainbow water snakes, Enhydris enhydris (Schneider, 1799), collected from southern Thailand. Adult nematodes consistent with Tanqua were found in the stomach. Various morphometric, meristic and qualitative morphological variables, including size, ratios, distances, cephalic appearance, the number of caudal papillae and other features, serve to distinguish the specimens from other species within the genus. In particular, Tanqua anomala and Tanqua diadema, which closely resemble our Tanqua specimens, can be differentiated by key diagnostic characteristics such as a retractable head, the distance from the anterior end to the cervical sac, the relative positions of caudal papillae and excretory pore, and the length of the uterus. Molecular analysis (COI and 18s rRNA genes) confirmed its status as a species of Tanqua, genetically distinct from Tanqua tiara, and matching the genetic sequence found in larvae of Tanqua sp. from a snakehead fish species from Bangladesh. Tanqua siamensis sp. nov. is described, supported by morphological traits, microscopic illustrations and genetic information. This study reports the first evidence of a caudal papillary pair in females. This species causes significant lesions on the stomach wall of the snake host, raising possible issues for snakes held in captivity regarding food hygiene and parasite protection.

The parasite fauna of Neotropical reptiles is poorly known, and the number of parasites described in these hosts does not seem to correspond to the actual species diversity in this zoogeographical region. This also applies to tapeworms such as proteocephalids, which are rarely found in reptiles and are strictly specific to their reptilian hosts. In the present paper, three new species of Ophiotaenia La Rue, 1911 are described from three dipsadine snake species (Squamata: Colubridae) in Ecuador, namely O. jeanmarctouzeti sp. n. from the Neotropical blunt-headed treesnake Imantodes cenchoa (Linnaeus), O. barraganae sp. n. from the beautiful calico snake Oxyrhopus formosus (Wied-Neuwied) and O. velascoae sp. n. from the forest flame snake Oxyrhopus petolarius (Linnaeus). The new species are characterised by type 1 uterine development, the number and distribution of testes, the size of the scolex and other metric features. As no molecular data are available on the specimens collected more than 35 years ago, the phylogenetic relationships of the individual taxa are not known.

A breeding colony of wild-origin eastern indigo snakes (EISs, Drymarchon couperi) that is part of a reintroduction program has been impacted by gastric cryptosporidiosis. Gastric cryptosporidiosis is an insidious disease of squamates caused by an apicomplexan protozoan, Cryptosporidium serpentis. Viral coinfections have been implicated as possible immunosuppressant agents that allow for disease progression and both adenovirus and reovirus have been implicated in allowing for the progression of gastric cryptosporidiosis during coinfection in other snake species. Molecular (PCR) screening for adenoviruses and reoviruses was performed for both C. serpentis-positive and C. serpentis-negative EIS within the breeding colony. No reoviruses were detected in the collection. Adenoviruses were present in 11/68 (16.2%) EISs evaluated, and there was no significant difference between C. serpentis-positive and C. serpentis-negative EISs (p = 0.196). There was no significant difference in adenovirus status between C. serpentis-positive EISs’ lifespan (p = 0.191) or survival rates (p = 0.823). These findings suggest that the presence of the adenoviruses found in this study does not contribute to the formation or progression of gastric cryptosporidiosis in EISs.

Invasive species pose a threat not only to biodiversity because they displace or compete with native fauna, but also because of the pathogens they can host. The Canary Islands are an Atlantic biodiversity hotspot threatened by increasing numbers of invasive species, including the California kingsnake Lampropeltis californiae, which was recently introduced to Gran Canaria. Seventy-seven snakes were examined for gastrointestinal parasites in 2019–2020. Sporocysts of Sarcocystis sp. were detected in 10 of them; detection of gamogonia stages in histological sections of 3 snakes confirmed the snake as a definitive host. Partial ssrDNA was amplified using SarcoFext/SarcoRext primers; an additional sequence of Sarcocystis was obtained from the tail muscle of the endemic Gran Canaria giant lizard Gallotia stehlini for a comparison. Identical ssrDNA sequences of unknown Sarcocystis sp. were obtained from 5 different snakes. Phylogenetic analysis showed that Sarcocystis sp. isolated from invasive California kingsnakes is unrelated to Sarcocystis provisionally considered S. stehlini from the endemic lizard. The dixenous coccidia are rarely reported to invade new predator–prey systems. However, the present data suggest that previously unknown Sarcocystis sp. is circulating among invasive snakes and as yet unknown vertebrate intermediate hosts, with undetermined consequences for the Gran Canaria ecosystem.

The combined use of molecular and microscopic techniques has become an increasingly common and efficient practice for the taxonomic and evolutionary understanding of single-celled parasites such as haemogregarines. Based on this integrative approach, we characterized Hepatozoon found in Helicops angulatus snakes from the Eastern Amazonia, Brazil. The gamonts observed caused cell hypertrophy and were extremely elongated and, in some cases, piriform (mean dimensions: 25.3 ± 1.9 × 8.6 ± 1.3 μm). These morphological features correspond to Hepatozoon carinicauda, described 50 years ago in the snake Helicops carinicaudus in the southeast region of Brazil. Phylogenetic and genetic divergence analyses, performed with the sequence obtained from the amplification of a 590 bp fragment of the 18S rRNA gene, revealed that Hepatozoon in He. angulatus differed from the other lineages retrieved from GenBank, and was clustered singly in both the phylogenetic tree and the haplotype network. The integration of these data allowed the identification of H. carinicauda in a new aquatic host, and increased the knowledge of its geographical distribution. Therefore, the present study included the first redescription of a Hepatozoon species in a snake from the Brazilian Amazon.

Here, we report a new species, Sarcocystis pantherophisi n. sp., with the Eastern rat snake (Pantherophis alleghaniensis) as natural definitive host and the interferon gamma gene knockout (KO) mouse as the experimental intermediate host. Sporocysts (n = 15) from intestinal contents of the snake were 10.8 × 8.9 μm. Sporocysts were orally infective to KO mice but not to laboratory-raised albino outbred house mice (Mus musculus). The interferon gamma KO mice developed schizont-associated neurological signs, and schizonts were cultivated in vitro from the brain. Mature sarcocysts were found in skeletal muscles of KO mice examined 41 days postinoculation (PI). Sarcocysts were slender, up to 70 μm wide and up to 3.5 mm long. By light microscopy, sarcocysts appeared thin-walled (<1 μm) without projections. By transmission electron microscopy, the sarcocyst wall was a variant of “type 1” (type 1i, new designation). The parasitophorous vacuolar membrane (pvm) had approximately 100-nm-wide × 100-nm-long bleb-like evaginations interspersed with 100-nm-wide × 650-nm-long elongated protrusions at irregular distances, and invaginations into the ground substance layer (gs) for a very short distance (6 nm). The gs was smooth, up to 500 nm thick, without tubules, and contained a few vesicles. Longitudinally cut bradyzoites at 54 days PI were banana-shaped, 7.8 × 2.2 μm (n = 5). Molecular characterization using 18S rRNA, 28S rRNA, ITS-1, and cox1 genes indicated a close relationship with other Sarcocystis parasites that have snake–rodent life cycles. The parasite in the present study was molecularly and biologically similar to a previously reported isolate (designated earlier as Sarcocystis sp. ex Pantherophis alleghaniensis) from P. alleghaniensis, and it was structurally different from other Sarcocystis species so far described.

Based on both unique morphological characteristics of the gamont, distinct changes caused to the host erythrocyte and analysis of partial 18S rRNA gene sequences, a new parasite of the genus Hepatozoon Miller, 1908 is described from the snake Philodryas nattereri Steindachner (Squamata: Dipsadidae) in northeastern Brazil. The new species, Hepatozoon musa n. sp., is characterized by large and curved mature gamonts (18.9 ± 0.9 μm in length and 3.8 ± 0.3 μm in width) that considerably engorge infected host erythrocytes and displace the nucleus laterally, which become longer and thinner. Phylogenetic estimates indicate the new species is more closely related to the recently described Hepatozoon cuestensis O’Dwyer, Moço, Paduan, Spenassatto, Silva & Ribolla, 2013, from Brazilian rattlesnakes. These recent findings highlight the need for further studies of Hepatozoon to better determine the biodiversity of this common but poorly-studied parasite group.

Serpentirhabdias mussuranae n. sp. is described from the lungs of the mussurana, Clelia clelia (Daudin, 1803), from vicinities of Lábrea, Amazonas State, Brazil. The species is characterized by the triangular oral opening, the presence of teeth (onchia) in the oesophastome, the excretory glands longer than the oesophagus and the tail abruptly narrowing in its anterior half and gradually tapering in posterior half. Among the Neotropical representatives of the genus, three species are known to possess the onchia in the oesophastome: S. atroxi , S. moi and S. viperidicus . Serpentirhabdias mussuranae n. sp. differs from S. atroxi and S. viperidicus by its triangular shape of the oral opening and the oesophastome in apical view, vs. round in the latter two congeners. Additionally, S. viperidicus has a larger oesophastome, 13–22 micrometers wide and 13–23 micrometers deep. The new species has relatively longer excretory glands than S. moi . The new species is morphologically and genetically close to S. atroxi , S. moi and S. viperidicus , all parasitic in Brazilian snakes, based on the presence of onchia and the comparison of nucleotide sequences of nuclear ribosomal DNA and mitochondrial cox1 gene (differences varied between 3.8% and 7.1%). Data on the life cycle of S. mussuranae n. sp. is provided, and the life cycle is typical of the genus Serpentirhabdias , with the combination of direct development and heterogony. Free-living larval stages and the adults of amphimictic free-living generation are described. The results of molecular phylogenetic analysis based on nuclear ribosomal internal transcribed spacer (ITS) + partial 28S region and partial mitochondrial cox1 gene are provided.

Hepatozoon parasites were examined for the first time in reptiles from the Seychelles Islands. Although both prevalence and intensity were low, Hepatozoon species were detected in individuals from 2 endemic species, the lizard Mabuya wrightii and the snake Lycognathophis seychellensis. This was confirmed using visual identification and through sequencing part of the 18s rRNA gene. Phylogenetic analysis indicates that the Hepatozoon on the Seychelles form a monophyletic lineage, although more data are clearly needed to stabilize estimates of relationships based on this marker.