The new synanthropic crevice weaver spider species, from the family Filistatidae, Pikelinia floydmuraria sp. nov . (male and females) is described from the department of Tolima, Colombia. The female internal genitalia of P. fasciata from the Galapagos islands, Ecuador, is described here for the first time. Additional unidentified species of Pikelinia populations were recorded in the departments of Cauca, Quindío, and Risaralda. Dietary analysis of P. floydmuraria sp. nov . (Tolima) and Pikelinia sp. (Armenia) revealed a predominance of Hymenoptera (~35% of prey), followed by Diptera and Coleoptera. This study expands known diversity and trophic ecology of Pikelinia genus.

Jan Cornelis Christiaan Loman (1856–1929) was a major contributor to our knowledge of sea spiders (Arthropoda, Pycnogonida) and to the collections of the Naturalis Biodiversity Center (NBC), Leiden. Loman worked on Pycnogonida material from various geographic origins, including southern Africa, the Antarctic Peninsula, Arctic seas, Southeast Asia, the Atlantic, Australia, the China Sea, Japan, and the Mediterranean Sea; he notably participated in the taxonomic study of samples from the Siboga Expedition, the Prince Albert I of Monaco expeditions, and the Swedish Antarctic Expeditions. In total, Loman described 54 sea spider species and six sea spider genera; 48 and three, respectively, are still regarded as valid today. In the present work, we aim to summarise Loman’s outstanding contribution to sea spider taxonomy by listing all species he reported or described. We recovered a total of 162 records in NBC, 133 of which correspond to type material, including 19 holotypes and 37 syntypes. We further sought out all Loman’s Pycnogonida material curated at NBC and located additional type material housed in institutions worldwide.

The species diversity of freshwater mussels in the upper Yangtze River has been seriously underestimated, and human-induced disturbances have severely threatened the survival of local bivalve species. In this study, we describe a new freshwater mussel species, Cristaria wangyucheni Z.-G. Chen & Y.-T. Dai, sp. nov. , from the Jialing River Basin in the upper Yangtze River, Sichuan, China, based on comparative morphology and molecular phylogeny. Phylogenetic analyses of COI and 28S rRNA gene fragments revealed that C. wangyucheni sp. nov. is a sister to the other species of Cristaria . The pairwise uncorrected COI p -distance analysis demonstrated genetic distances ranging from 10.10% (between this species and C. truncata ) to 13.17% (between this species and C. “ beirensis ”). Morphologically, C. wangyucheni sp. nov. can be distinguished from its congeners by its medium-sized shell, which ranges from an elongated triangle to an irregular rectangle. This discovery broadens our understanding of interspecific shell morphological variation within the genus Cristaria .

Myxobolus branchiostegi sp. nov. was detected in the gallbladder of six out of 28 specimens (21.4%) of Branchiostegus argentatus Cuvier, 1830 from the East China Sea. This is the first record of a Myxobolus species infecting this host. Mature myxospores of the new species were oval in valvular view, measuring 9.21 ± 0.52 µm (8.3–9.8 µm) in length and 7.40 ± 0.60 µm (6.2–8.0 µm) in width. Two equal, pyriform polar capsules measured 4.40 ± 0.34 µm (3.7–4.8 µm) in length and 2.58 ± 0.17 µm (2.3–2.9 µm) in width, each possessing polar tubules with 4–6 turns. Phylogenetic analysis, based on small subunit ribosomal RNA gene (SSU rDNA) sequences placed the new species within the family Myxobolidae, as a sister to Myxobolus iwagiensis Kawano et al., 2025. Further analysis suggested a possible trend that the clustering of Myxobolidae species may be influenced by the taxonomic affinity of their fish hosts, with closely-related parasites tending to infect hosts within the same order. Host aquatic habitat (marine, brackish-water or freshwater) and species geographic distribution may also contribute to the observed clustering patterns.

Species discovery within Odorrana has gradually increased over the years, establishing a remarkable diversity for the genus. During recent herpetological surveys, we collected specimens from Yingjiang County, Yunnan Province, China with additional samples from Thailand and Vietnam. Based on combined morphological and phylogenetic analyses, we describe a new species Odorrana sudianensis sp. nov. from Sudian Town, Yingjiang County, China and report new records of O. heatwolei for Thailand and Vietnam. Phylogenetic analyses, based on the 16S rRNA mitochondrial gene fragment, confirm the new species as a distinct evolutionary lineage with a genetic divergence ( p -distance) of 4.6% from its closest sister species O. dulongensis . Odorrana sudianensis sp. nov. is morphologically distinguishable from all its known congeners by having a robust medium adult body size, a head length longer than wide, a mottled grass-green dorsum with dark brown blotches on the posterior region, absence of dorsolateral folds and circum-marginal grooves for all finger discs expanded with lateroventral grooves. Additionally, the new species record sequences from Thailand and Vietnam nested within the O. heatwolei subclade with a low p -distance (0.0–0.5%) from topotypic sequences of O. heatwolei . Examined specimen shows morphological congruence with topotypic O. heatwolei in key diagnostic traits. Our new species and new species records increase the number of recognised species of Odorrana to 46 in China, seven in Thailand and 23 in Vietnam. We also address existing taxonomic disputes within Odorrana and provide comments and recommendations on the taxonomy of several species within the genus.

Species identification and delimitation are critical for biodiversity conservation. Recent mitochondrial-based phylogenetic studies of the genus Paramesotriton, a group of small salamanders inhabiting mountain streams in southern China and northern Vietnam, suggest that its diversity may be underestimated. In this study, we confirm and characterize a new species, Paramesotriton wumengshanensis sp. nov., using morphological, mitochondrial NADH dehydrogenase subunit 2 (ND2), mitogenome, and genomic evidence. This new species can be distinguished from other Paramesotriton species by characteristics such as rough and large body warts, large eyes, the absence of vestigial gills and gill filaments in adults, and distinctive vomerine teeth. Statistical analysis of the morphological data further showed that the new species is significantly different from its close relatives. Phylogenetic reconstruction based on concatenated and coalescent approaches, using both mitochondrial DNA and nuclear single nucleotide polymorphisms (SNPs) generated by restriction site-associated DNA sequencing, revealed that the new species forms a distinct lineage within the genus Paramesotriton, exhibiting a minimum genetic distance of 0.63% in mitochondrial ND2 compared to congeners. The observed cytonuclear discordance and minor mitochondrial differences among species may stem from historical gene flow and/or incomplete lineage sorting, and future studies using genomic evidence are needed to investigate their respective contributions. Based on this discovery, we recommend that independent evidence, especially genomic evidence, be integrated into the classification of closely related species to avoid falling into the trap of mitochondrial introgression.

A new species of marine flatworm of the genus Plagiostomum is described from the intertidal zone along the coast of South China, based on comprehensive morphology, histology, reproductive biology, and molecular phylogenetic analyses. Plagiostomum aestuarium has a blunt anterior end with a small tentacle-like structure and a dark-brown patch covering the brain region. A pair of testes and a pair of ovaries are separated. The testes are located ventrally, while the ovaries are distributed from the vitellaria towards the testes. The vitellaria are separated at the anterior end, merge at the dorsal part of the intestine, and separate again at the posterior end on both sides of the intestine. The penis is encased in a well-developed penis sheath. The proximal part of the penis is coiled within the distal sac, and the distal part of the penis is relatively short. In light of the distinctive characteristics that distinguish this new species, we have classified it within the genus Plagiostomum (Platyhelminthes: Prolecithophora: Plagiostomidae). The phylogenetic tree constructed based on the concatenated datasets of 18S rDNA and 28S rDNA revealed that P. aestuarium is closely related to other Plagiostomum species. Furthermore, this study provides a comprehensive account of the distinctive reproductive biology of P. aestuarium and, for the first time, elucidates the function of the penis sheath structure during hypodermic insemination. This new finding could potentially serve as a new classification criterion for species within the family Plagiostomidae.

We present the morphological and genetic characterization of a new shallow-water tanaid, Synapseudes marinaesp. nov., collected from Milatos Beach on the northern coast of Crete, marking the first record of the genus Synapseudes from the Sea of Crete. This species exhibits strong morphological similarities to Synapseudes mediterraneus, briefly described by Băcescu in 1977 from the Mediterranean waters of Israel, which is also redescribed herein. In addition to the taxonomic descriptions, we include mitochondrial cytochrome c oxidase subunit I (COI) data to support the classification of the newly described species within the Synapseudes genus, noting a p-distance value of 28% between species of Synapseudes. A detailed diagnosis of the Synapseudes species occurring in the Mediterranean Sea is provided. Scanning electron microscopy images of S. marinaesp. nov. have been incorporated to enhance the optical microscope drawings and provide a more comprehensive depiction of this new species.

A new species, Phoxinus ayukensissp. nov., from the Kuban basin (Northwestern Caucasus) is described. This species has an extremely narrow range of approximately 5–7 km in a seasonally almost drying stream within the karstic region. The new species has a moderate genetic distance in cytochrome b mtDNA (p-distance = 0.026 ± 0.005) from geographically and genetically close species in the Kuban basin—P. adagumicus—and differs from all known Phoxinus species by a highly increased number of scales in the lateral series: 87–105 (mean 97.7), differs from other species from Eastern Europe and the Caucasus (P. adagumicus, P. chrysoprasius, P. colchicus, and P. isetensis) by an increased frequency of occurrence of seven rays in the pelvic fin (ca. 35%) and an increased number of scales between bases of dorsal and anal fins (32–41, mean 36.7). Morphologically, the new species is the most different from the other Caucasian species, but it is closer to the Northern minnow P. isetensis; that might be explained by phenotypic convergence caused by adaptation to cold waters. The range of the new species is limited by waterfalls in the upper reach of the Ayuk Stream, where subterranean water outlets probably contributed to its survival. The role of Pleistocene glaciations in shaping the modern distribution and environmental differences in evolutionary divergence of Caucasian Phoxinus is highlighted. Low genetic diversity coupled with extremely limited range within the seasonally half-drying stream suggests a high rank of protection for new species.

While taxonomy of the odorous frog genus Odorrana has made considerable progress recently, far less attention was given to those newly-described karst-associated species. In this study, the taxonomic status of Odorrana lipuensis group, species living in karst environments, was revisited. Combining the scrutiny of previous literature, molecular analyses using two mitochondrial DNA fragments (i.e. 16S rRNA and CO1) and morphological analyses including a series of additional specimens, we defined the O. lipuensis group and revised the taxonomic accounts of recognised species. Based on these data, we described a new species, O. calciphilasp. nov. from the karst regions in northern Guangdong, China. Apart from this new species, the O. lipuensis group currently contains three other species distributed in southern China and northern Vietnam, namely O. concelata, O. liboensis and O. lipuensis. Morphological comparisons between this group and other congeners, together with a dichotomous identification key for each species within this group, were also presented. Finally, the known distribution, implications of morphological distinctiveness, ecological and evolutionary significances and existing taxonomic issues of these species were also discussed.