A high-altitude population of Hyperboreomyzon polaris (Hirudinea: Glossiphoniidae) in Altai Mountains, South Siberia, Russia.

Hyperboreomyzon polaris Bolotov, Eliseeva, Klass & Kondakov, 2022 (Hirudinea: Glossiphoniidae) is an enigmatic freshwater leech that was recently described based on three specimens from two remote regions of the Eurasian Arctic, that is, the Kolguev Island and Putorana Plateau, Russia. Later on, misidentified historical samples of this species were discovered in the Hirudinea collection of Zoological Institute of the Russian Academy of Sciences (St. Petersburg, Russia). These samples were collected by Pavel G. Ignatov, a prominent Russian geographer and traveler, from a remote high-altitude area of the Altai Mountains (South Siberia) in 1901. To collect new samples from this population, we organized a field expedition to the same area (Lake Dzhulukul) in 2023. Molecular genetic data (COI and 18S rRNA) obtained from newly collected specimens revealed that they belong to H. polaris. Hence, this leech could be considered an Arctic-alpine species, the disjunctive range of which covers Arctic areas of Eurasia and Central Asian (South Siberian) mountains. We describe and illustrate living individuals of H. polaris for the first time, update its morphological diagnosis, present a life cycle reconstruction based on the frequency of four size classes in available samples. It is shown that this species prefers small lentic water bodies such as small lakes and lakelets. The crop content of a well-fed specimen from Altai contains DNA of the northern pintail Anas acuta Linnaeus (Aves: Anatidae), indicating that H. polaris feeds on blood of waterfowl. Our results indicate that Hyperboreomyzon may be considered a species adapted to cold high-latitude areas and mountain refugia.

A new freshwater leech species from Asian Swamp Eel stocks in China.

Discoveries of new Hemiclepsis species (Hirudinea: Glossiphoniidae) in East and Southeast Asia were expected. A peculiar freshwater leech was found on the body surface of Asian Swamp Eel Monopterus albus (Synbranchiformes: Synbranchidae) in Jingzhou, Hubei Province, China. Here, we describe this leech species as Hemiclepsis yangtzenensis sp. nov. It could be distinguished from other congeners based on a combination of morphological features such as very small size, translucent body with dense green reticulate markings throughout dorsum, very large posterior sucker with a characteristic reticulate pattern, and two pairs of well-developed drop-like eyespots. It also represents a phylogenetic lineage that is distant from other members of the genus based on the COI and 18S rRNA sequences. This leech species seems to be a specialized fish parasite that could negatively affect farming and wild stocks of Asian Swamp Eel in China.

Cryptic taxonomic diversity and high-latitude melanism in the glossiphoniid leech assemblage from the Eurasian Arctic.

The family Glossiphoniidae is a diverse and widespread clade of freshwater leeches, playing a significant role in functioning of aquatic ecosystems. The taxonomy and biogeography of leeches from temperate, subtropical, and tropical regions attracted much attention of zoologists, while their taxonomic richness and distribution in the Arctic are poorly understood. Here, we present an overview of the Eurasian Arctic Glossiphoniidae based on the most comprehensive occurrence and DNA sequence datasets sampled to date. This fauna contains 14 species, belonging to five genera and three subfamilies. One genus and five species are new to science and described here. The world's northernmost occurrences of glossiphoniids are situated on the Taymyr Peninsula at 72° N, although further records at higher latitudes are expected. Most Arctic leeches are characterized by broad ranges crossing several climatic zones (e.g., Glossiphonia balcanica and G. nebulosa), although the distribution of two new species may be confined to the high-latitude areas. The Taymyr Peninsula with the nearby Putorana Plateau represents the most species-rich area (totally 9 species), while the European Arctic, Iceland, Kolyma Highland, and Chukotka Peninsula house depleted faunas (2-4 species per subregion). Finally, we show that the high-latitude melanism is a common phenomenon in glossiphoniid leeches.