Ochetosoma heterocoelium (Travassos, 1921) was collected from the mouth and oesophagus of a pit viper, Bothrops moojeni Hoge, 1966 in São Sebastião do Paraíso Farm (21°51’48.26" S, 48°26’56.78" W), municipality of Boa Esperança do Sul, São Paulo State, Brazil. In this study, we provide the first molecular characterisation of this digenean using 28S rDNA and COI sequences, and its phylogenetic position within the Plagiorchiida is assessed. Furthermore, new morphological features are added to the diagnosis of the species, and scanning electron microscopy photomicrographs are presented. Sequences of the 28S rRNA gene of O. heterocoelium were successfully obtained and aligned with 35 digenean species belonging to Plagiorchiida. Only three congeners – O. aniarum (Leidy, 1890), O elongatum (Seo et al. 2024), and O. kansense (Crow, 1913) – have been sequenced for this molecular marker. The newly sequenced individuals of O. heterocoelium are 98.7% and 99.4% similar to O. aniarum and O. kansensis, respectively, and Ochetosoma is not recovered as a monophyletic group. Dasymetra nicolli Holl and Allison, 1935 and Lechriorchis tygarti Talbot, 1933 are nested with Ochetosoma.

As part of a broad survey of the trematodes of damselfishes (Pomacentridae) in the tropical Indo-West Pacific, zoogonids were collected from multiple localities in Australia, New Caledonia, and French Polynesia. All zoogonid specimens collected were consistent with the subfamily Lecithostaphylinae, and morphological and molecular data (ITS2 and 28S rDNA, and cox1 mtDNA) were generated for most host-locality combinations to enable an integrative species delimitation. The collection comprised three species: Deretrema stratiotes n. sp. from four species of Abudefduf Forsskål from Ningaloo Reef in Western Australia, and two species consistent with the genus Lecithostaphylus Odhner, 1911 for which Innuptacola n. gen. is proposed based on phylogenetic and morphological distinction, the type-species I. gibsoni (Cribb, Bray & Barker, 1992) n. comb. (= L. gibsoni) from six species of Abudefduf in Ningaloo Reef, Queensland and New Caledonia, and I. torquata n. sp. from 12 pomacentrid species in Ningaloo Reef, the Great Barrier Reef in Queensland, and the Gambier Islands in French Polynesia. The new collection demonstrates that some zoogonid species are geographically widespread (from the Pacific Ocean to the Indian Ocean) and can infect a broad range of hosts (multiple genera within a family), whereas others are apparently geographically restricted and exhibit higher host-specificity (fishes within a single genus).

A population of Oscheius insectivorus was recovered from inside the body of a live scarab beetle collected from natural forests of Jafar Abad village, Golestan province, and was reported from Iran for the first time. The Iranian isolate of the species is characterized by 1103–1942 μm long females with their vulva at 46.9–57.4% of the body, tail 75–118 μm long, males with spicules 60.0–74.5 μm long, gubernaculum 23.7–32.2 μm long, and infective juveniles measuring 790–985 μm long. Females and males of the recovered population had shorter body when compared with the type population. Molecular identification of the recovered population was performed using the SSU and D2-D3 expansion segments of LSU rDNA, and corresponding phylogenetic trees were reconstructed and discussed. The pathogenicity of the Iranian isolate was evaluated on the larvae and adults of the poplar leaf beetle, Chrysomela populi, and the larvae of the wax moth, Galleria mellonella, under laboratory conditions. A suspension of 200 infective juveniles per ml (IJs/ml) of the nematode was most effective against third instar larvae of C. populi, causing 75% mortality 72 hours post-exposure. In adults, mortality reached 70% at the same concentration and exposure time. For G. mellonella larvae, O. insectivorus caused 50% mortality at 200 IJs/ml within 72 hours post-exposure. The lethal concentration 50 (LC50) values of the nematode were 77.71 and 94.06 IJs/ml for third instar larvae and adults of C. populi, respectively, and 217.04 IJs/ml for fifth instar larvae of G. mellonella 72 hours post-exposure at 25°C and 60% relative humidity.

This study describes a new species of Pharyngodon Diesing, 1961 (Nematoda: Pharyngodonidae) in teiid lizards Ameivula ocellifera (Spix, 1895) (Squamata: Teiidae) from a Caatinga morphoclimatic domain in the state of Pernambuco, Brazil. Pharyngodon ameivulum n. sp., like 11 other species of the genus, features males without spicules, females with truncated eggs, and no tail spines. However, the new species is distinguished by a unique set of morphological characteristics, such as males possessing three pairs of caudal papillae, with the first pair precloacal, the second adcloacal, and the third postcloacal (arrangement 1:1:1), the second pair (adcloacal) of papillae having a bifurcated distal end, and females with lateral body alae. Molecular analysis of the 18S rDNA, 28S rDNA, and 18S + 28S concatenated sequences genes reveals that P. ameivulum n. sp. clusters with representatives of Pharyngodonidae from the genera Skrjabinodon Inglis, 1968 and Spauligodon Skrjabin, Schikhobalova & Lagodovska, 1960, forming a basal clade to the clade composed of Spauligodon spp. and Skrjabinodon trimorphi Ainsworth, 1990. These are the first phylogenetic assays to include a species of Pharyngodon.

Species of the genus Corynosoma (Acanthocephala: Polymorphida) mainly parasitize marine mammals and rarely marine birds, and are of veterinary and medical importance due to causing corynosomiasis in wildlife and humans. However, the current knowledge of the mitochondrial genomes and mitogenomic phylogeny of this group remains very insufficient. In the present study, the complete mitochondrial genomes of C. bullosum (von Linstow, 1892) and C. evae Zdzitowiecki, 1984 were sequenced and annotated for the first time. Both mitogenomes comprise 12 protein-coding genes (missing atp8), 22 tRNA genes, and 2 ribosomal RNAs (rrnS and rrnL), plus 2 non-coding regions (NCR1 and NCR2). Corynosoma bullosum has the largest mitogenome (14,879 bp) of any polymorphid species reported so far, while C. evae has the smallest (13,947 bp), except for Sphaerirostris lanceoides (Petrochenko, 1949). Comparative mitogenomic analysis also revealed the presence of distinct discrepancies in A + T content and gene rearrangement across the families Polymorphidae, Centrorhynchidae, and Plagiorhynchidae. Moreover, phylogenetic analyses based on the concatenated amino acid sequences of 12 protein-coding genes strongly supported the monophyly of the order Polymorphida and a close affinity between the families Polymorphidae and Centrorhynchidae in Polymorphida. The present mitogenomic phylogeny provides additional evidence for a sister relationship between the genera Corynosoma and Bolbosoma and demonstrated that C. evae has a closer relationship with C. villosum than C. bullosum in the genus Corynosoma.

Copepods of the genus Pennella parasitize a wide range of marine animals, including cetaceans, teleosts, and cephalopods worldwide. Their taxonomy is unclear, as there is incongruence between morphological and genetic data and incomplete species coverage. This study provides new morphological and genetic (COI) data from 23 specimens of Pennella cf. filosa (syn. P. balaenoptera) from western Mediterranean whales and a swordfish. First, their position in the phylogeny of Pennella was assessed and species delimitation revisited using all available Pennella COI sequences (n = 189), obtained from Mediterranean and north Pacific specimens from 18 host species (including multiple cetaceans and teleosts). Second, it was investigated whether the geographic location, degree of host vagility, or host taxonomic identity help explain genetic differentiation. Five distinct haplotype groups with varying genetic divergence were distinguished. Although the presence of sibling species cannot be ruled out, species delimitation methods could not find interspecific genetic differences, leaving the taxonomy of the genus unresolved. The observed genetic differentiation could not be attributed to geography or host type. This suggests that members of the genus Pennella show low specificity for definitive hosts and interoceanic dispersal mediated by some vagile definitive hosts. The use of more genetic markers for addressing these questions in the future is encouraged.

Members of Sinistroporomonorchis Wee, Cutmore, Pérez-del-Olmo & Cribb, 2020 represent a small group of trematodes belonging to the Monorchiidae Odhner, 1911 with 5 species described from mugilid hosts. Specimens consistent with the generic concept of Sinistroporomonorchis were obtained from Floridichthys polyommus (Cyprinodontidae); most of them were juveniles from 4 localities within the Yucatán Peninsula. After a detailed morphological examination including scanning electron microscopy images and a principal component analysis, the specimens collected represented a new species, Sinistroporomonorchis bolini n. sp. The new species can be differentiated by the presence of an overall large pharynx including the proportion of pharynx width to oral sucker width, a uterus arranged in 2 main lateral fields, and by presenting robust caeca. In addition, sequences of the 28S of large subunit of nuclear ribosomal RNA and cox1 of the mitochondrial DNA were obtained. Phylogenetic trees inferred from each dataset, placed all the specimens in a monophyletic clade, confirming that the isolates belonged to the same species. The new species is the sixth described for the genus Sinistroporomonorchis, the fifth described from the Yucatán Peninsula and the first described from a non-mugilid host.

Although nudibranchs are common and attractive animals, our understanding of these marine gastropods in Vietnam remains limited. Prior research has suggested that combining morphological examination with molecular analysis results in more accurate identification of nudibranchs. However, previous studies in Vietnam have typically relied solely on morphological methods for nudibranch identification. In this study, the nudibranch species Halgerda batangas was recorded in Vietnam for the first time based on both morphological and molecular approaches. Halgerda batangas was characterized by a network pattern consisting of orange lines, relatively low dorsal tubercles with red-orange caps and white basal rings, and an orange line along the foot margin. Molecular analysis corroborated the morphological findings. These results suggest that integrating morphological and molecular methods is an effective approach for identifying nudibranchs.

Species of the family Echinostomatidae use diverse gastropod taxa as first intermediate hosts. However, identification of echinostomatid larvae often proves difficult because of incomplete information on their life cycles and lack of molecular data that can link larvae to the corresponding known adults. Here, echinostomatids that were isolated from freshwater limpets in South Africa were described using light and scanning electron microscopy, and ribosomal (28S, ITS, and 18S) and mitochondrial (cox1) DNA sequences. The analyses revealed three species: Petasiger radiatus, Petasiger sp., and Echinostomatidae gen. sp. Considering the close morphological resemblance between cercariae of Petasiger spp., the current species were compared with data from literature. The results showed that cercarial size is generally unsuitable for species discrimination. The numbers of flame cells and refractile granules in the excretory system, and penetration gland cell patterns, may indicate, but do not prove species identity. Although papillary patterns were distinct between species, papillae were clearly discernible only using scanning electron microscopy and are known for only a few species. Phylogenetic reconstruction indicated that 28S rDNA sequences of Petasiger on GenBank are for P. exaeretus, P. phalacrocoracis, P. radiatus, and six unnamed species. Furthermore, the results revealed that multiple ITS rDNA and cox1 sequences labelled as Stephanoprora amurensis and P. phalacrocoracis on GenBank, are from isolates whose identities are questionable. Echinostomatidae gen. sp. could not be assigned to any currently known genus. Expansion of the genetic database of the family Echinostomatidae is necessary for the delineation of putative species and elucidation of intergeneric relationships.

Two new species in the genera Diploicia and Physcia are described from the tropical dry forest of Mexico. Both species are supported by morphological, chemical and molecular evidence. Diploicia edulis, a species heavily consumed by invertebrates, is characterized by lecanorine apothecia, a dull brown epihymenium not diffused by a green pigment (K−), a subhymenium conspicuously inspersed with oil droplets, and the diploicin chemosyndrome. We provide the first molecular evidence to support the inclusion of species with lecanorine apothecia in the genus Diploicia. Physcia ornamentalis, previously reported under the name Physcia undulata s. lat. as one of the main construction materials for the bags of a moth caterpillar species (Psychidae), is characterized by a frosted-pruinose thallus, soralia originating in the lobe sinuses, and by lacking soralia in the thalline margin of the apothecia.

Meteterakis striatura Oshmarin & Demshin, 1972 is redescribed from the posterior intestine of tropical tortoise Geoemyda spengleri (Gmelin, 1789) (Testudines: Geoemydidae) from China. Some characteristic features of the male reproductive system not reported previously are now reported for the present species. These include the presence of two blind diverticula near the mid-region of the seminal vesicle and a small cuticular structure near the opening of the cloaca – which we propose to name the ‘scutum.’ The morphological function and diagnostic value of these characters as well as presence of gubernaculum or ‘gubernacular mass’ in examined representatives of the genus, including paratype specimens of M. amamiensis Hasegawa, 1990 and M. ishikawanae Hasegawa, 1987 is discussed. Illustrative material is supplemented with scanning electron microscope and light microscope images of adult males and females. The molecular characterization of the species is inferred from 18S and 28S rDNA. The taxonomic composition of the genus Meteterakis is discussed and the full list of species with taxonomic remarks is updated.

Continental drift of Baltica from the Tremadocian subpolar latitudes to subtropical latitudes in the Katian was the main factor controlling the succession of the Ordovician Baltic conodont communities. These faunas were gradually enriched during the Floian as a result of immigrations from the regions experiencing warmer climate. Reinterpretation of quantitative data in terms of population approach to fossil assemblages shows how some of these immigrants evolved anagenetically in place, changing their contribution to the secondary productivity of the ecosystem. The composition of the fauna became surprisingly uniform, at least since the numerical domination by the presumably indigenous Baltoniodus lineage was established during the Dapingian. Baltoniodus was supplemented by another indigenous lineage of Trapezognathus-Lenodus-Eoplacognathus, which continued its subordinate occurrence during the Darriwilian. The early Sandbian transgression resulted in immigration of the Amorphognathus lineage that emerged allopatrically in an unknown region but then began evolving anagenetically until the end of the Ordovician. Conodonts with coniform apparatus elements added complexity to the general picture of immigrations and disappearances, but only the lineage of Protopanderodus rectus seems to have differentiated geographically its contribution to the biological productivity. Several brief cooling and warming episodes did not result in any long-term transformations of the conodont communities. Most intriguing was the immigration of the Yaoxianognathus lineage that probably gave rise to all of the post-Ordovician ozarkodinids. By that time, Yaoxianognathus had its close relative in the tropical North American Midcontinent, but the source area was probably in the Darriwilian of the Argentinian part of Gondwana. Forms with thin P1 elements of basal cone walls, like Scabbardella or Hamarodus, are indicators of glacial Gondwanan influences. The lineage of Sagittodontina, associated with these in the Małopolska microcontinent (with Gondwanan affinities), was subordinate in Baltica until it had been influenced by the Hirnantian glaciation that ended the Baltic conodont fauna.

A new Iranian population of Lindseyus costatus is characterized, including morphometrics, microphotographs, and molecular (18S, 28S rDNA) studies. It is compared with previously known populations. The results derived from molecular analyses failed to find close evolutionary relationships with other traditional genera of Belondiridae and Swangeriinae, adding more uncertainties about the internal phylogeny of the family. The taxonomy of Lindseyus is revised, with a new diagnosis, list of species, key to their identification, and a compilation of their main morphometrics.

Amphalius spirataenius belongs to Arthropoda, Insecta, Siphonaptera, Ceratophylloidea, Ceratophyllinae, Amphalius. Only 2 species from the subfamily Ceratophyllinae have been sequenced for mitogenomes to date. The genus Amphalius mitogenome research was still blank. The A. spirataenius mitogenome was determined, annotated and analysed for the first time in this study. The 14 825 bp long genome has the typical metazoan of 37 genes with insect ancestral genome arrangement pattern. There was no significant difference in codon usage of 13 protein-coding genes: UUA, UCU, GUU, ACU and GCU were the most frequently used codons. It was found that the reason for codon preference mainly contributed to natural selection base on PR2, ENC-plot and neutrality curve analysis. Evolutionary rate, conserved sites, variable sites and nucleotide diversity analysis indicated that nad6 of A. spirataenius had the fastest evolutionary rate, while cox1 had the slowest evolutionary rate. Phylogenetic trees were reconstructed based on 13 protein-coding genes and 2 rRNA genes datasets using Bayesian inference and maximum likelihood method. The phylogenetic tree supported that both Siphonaptera and Mecoptera were monophyletic, and were sister groups to each other. This study filled gap of the genus Amphalius mitogenome sequences and was of great significance for understanding evolution of the order Siphonaptera.

Panulirus stimpsoni is restricted to southern China, Vietnam, and Japan but has been rarely reported in tropical Gulf of Thailand. In Malaysia, only six species were previously reported. This study (1) reports the seventh Malaysian species – a new record of P. stimpsoni with morphological and genetic data; (2) establishes a checklist of Malaysian Panulirus species. Surveys from 2021 to 2022 sampled lobsters across Malaysia by SCUBA or from fishermen. Seven species were identified and a modified key of Malaysian species was constructed. The COI gene was used for genetic identification and phylogenetic tree reconstruction with maximum likelihood (ML). The best model was GTR + I + G. The ML tree comprised Clades I and II with sequences clustering by species and strong support. Most Peninsular Malaysian lobsters were P. polyphagus while P. versicolor dominated Sabah. Information on P. stimpsoni's full fishery potential, distribution, ecology, and biology is limited. Further research is needed to ensure conservation and management as data are only available for six previously reported species. Further studies are required to discover sustainable use approaches for all Panulirus species, particularly P. stimpsoni, given limited ecological understanding.

The cyst nematodes, subfamily Heteroderinae, are plant pathogens of worldwide economic significance. A new cyst nematode of the genus Cactodera within the Heteroderinae, Cactodera xinanensis n. sp., was isolated from rhizospheres of crops in the Guizhou and Sichuan provinces of southwest China. The new species was characterized by having the cyst with a length/width = 1.3 ± 0.1 (1.1–1.6), a fenestral diameter of 28.1 ± 4.3 (21.3–38.7) μm, vulval denticles present; second-stage juvenile with stylet 21.5 ± 0.5 (20.3–22.6) μm long, tail 59.4 ± 2.0 (55.9–63.8) μm long and hyaline region 28.7 ± 2.7 (25.0–36.3) μm long, lateral field with four incisures; the eggshell with punctations. The new species can be differentiated from other species of Cactodera by a longer tail and hyaline region of second-stage juveniles. Phylogenetic relationships within populations and species of Cactodera are given based on the analysis of the internal transcribed spacer (ITS-rRNA), the large subunit of the nuclear ribosomal RNA (28S-rRNA) D2-D3 region and the partial cytochrome oxidase subunit I (COI) gene sequences here. The ITS-rRNA, 28S-rRNA and COI gene sequences clearly differentiated Cactodera xinanensis n. sp. from other species of Cactodera. A key and a morphological identification characteristic table for the species of Cactodera are included in the study.

A new species of bothriocephalid cestode in the genus Anantrum is described from the intestine of the shorthead lizardfish Synodus scituliceps from the north Pacific coast of Costa Rica. The new species is described based on an integrative taxonomic approach that includes the use of light and scanning electron microscopy, 28S rDNA sequencing, and phylogenetic analysis. Anantrum gallopintoi sp. nov. is the third known member of this genus and can be distinguished from A. tortum (Linton, 1905) and A. histocephalum Jensen & Heckmann, 1977 by a combination of morphological and ecological traits and, in particular, by having a vaginal sphincter, different number of testes, and different type host and type locality. The molecular analysis and the phylogenetic reconstructions supported its status as a new taxon placing it within a well-supported separate branch of Anantrum spp. subclade. According to the present finding, S. scituliceps represents a new host record and Costa Rica a new geographical record for Anantrum species, and, in general, for a bothriocephalid cestode.

Adults of the genus Posthodiplostomum, Dubois, 1936 are parasites of fish-eating birds, mainly of the family Ardeidae, and are globally distributed. The genus currently comprises 35 species, although recent molecular evidence has shown that the diversity of the genus is underestimated since several candidate species have been recognized. In the Neotropical region of Mexico, at least 6 Posthodiplostomum lineages have been detected with metacercaria stages recovered from unrelated fish hosts. Here, we obtained adult specimens of Posthodiplostomum from 6 fish-eating birds representing 2 families (Butorides virescens, Ardea herodias, Nycticorax nycticorax, Tigrisoma mexicanum – Ardeidae, and Rynchops niger and Leucophaeus atricilla – Lariidae) from 4 localities in southern Mexico. Specimens were sequenced for 2 nuclear (28S and ITS1–5.8S–ITS2) and 1 mitochondrial (cox1) molecular marker. Phylogenetic analyses allowed us to link metacercariae and adult specimens and recognized a lineage, which was described morphologically. The new species can be distinguished from its congeners by its prosoma morphology and body size; this is the first described species in the Neotropical region of Mexico. Additionally, new host and locality records for P. macrocotyle and P. pricei are presented, expanding their geographical distribution range in the Americas.