Another plea for ‘best practice’ in molecular approaches to trematode systematics: Diplostomum sp. clade Q identified as Diplostomum baeri Dubois, 1937 in Europe

DNA sequence data became an integral part of species characterization and identification. Still, specimens associated with a particular DNA sequence must be identified by the use of traditional morphology-based analysis and correct linking of sequence and identification must be ensured. Only a small part of DNA sequences of the genus Diplostomum (Diplostomidae) is based on adult isolates which are essential for accurate identification. In this study, we provide species identification with an aid of morphological and molecular (cox1, ITS-5.8S-ITS2 and 28S) characterization of adults of Diplostomum baeri Dubois, 1937 from naturally infected Larus canus Linnaeus in Karelia, Russia. Furthermore, we reveal that the DNA sequences of our isolates of D. baeri are identical with those of the lineage Diplostomum sp. clade Q , while other sequences labelled as the ‘D. baeri’ complex do not represent lineages of D. baeri. Our new material of cercariae from Radix balthica (Linnaeus) in Ireland is also linked to Diplostomum sp. clade Q. We reveal that D. baeri is widely distributed in Europe; as first intermediate hosts lymnaeid snails (Radix auricularia (Linnaeus), R. balthica) are used; metacercariae occur in eye lens of cyprinid fishes. In light of the convoluted taxonomy of D. baeri and other Diplostomum spp., we extend the recommendations of Blasco-Costa et al. (2016, Systematic Parasitology 93, 295–306) for the ‘best practice’ in molecular approaches to trematode systematics. The current study is another step in elucidating the species spectrum of Diplostomum based on integrative taxonomy with well-described morphology of adults linked to sequences.

Relationships between characteristics of macrobenthic assemblages and environmental variables in the Heihe River Basin, China

To clarify the characteristics of macrobenthic assemblages and their response to the aquatic environment in the upper and middle reaches of the Heihe River, water quality, sediments and macrobenthos measurements were conducted in the summers of 2018 and 2019. The results showed that 50 species of macrobenthos were identified, belonging to 3 phyla, 7 classes, 15 orders and 32 families, mainly arthropods (37 species) and mollusks (11 species). Argyroneta aquatica, Chlaznius sp., dragonfly nymphs, Palaemon modestus, Radix auricularia, Cyraulus albus and Suecinea sp. were the dominant species in the whole study region; most of these are pollution-tolerant and moderately tolerant species. The macrobenthos density and biomass ranged from 10 to 577 ind./m2 and from 0.0907 to 50.0562 g/m2, respectively, showing high spatial heterogeneity. Predators were the main functional feeding group. One-way analysis of variance clarified that Margalef's index and the Shannon–Wiener index differed significantly among the spatial areas (P < 0.05). Canonical correspondence analysis showed that the spatial heterogeneity of the macrobenthos was affected by the water temperature and the total nitrogen and total phosphorus in sediments (P < 0.05).

The Orava dam reservoir – an important site of aquatic molluscs in north-western Slovakia

Mollusc assemblages of the Orava reservoir, the biggest dam reservoir in Slovakia, were studied in 2020. The reservoir, built in 1941–1953, is situated in north-western Slovakia. Sixteen aquatic mollusc species (13 gastropods, 3 bivalves) were recorded. Valvata piscinalis (O. F. Müller), Radix auricularia (Linnaeus) and Gyraulus parvus (Say) were the most frequent; they were recorded in more than ten sites each. Rich mollusc assemblages, composed mainly of gastropods, were found in sites with rich littoral vegetation of macrophytes. The bivalve diversity and abundance were very small, especially compared to the other studied dam reservoirs. The current results were compared with the previous surveys. The occurrence of Radix lagotis (Schrank) is its first reliable record in Slovakia. Viviparus acerosus (Bourguignat), Aplexa hypnorum (Linnaeus), Anodonta cygnea (Linnaeus), non-native Potamopyrgus antipodarum (Gray) and Physa acuta (Draparnaud) were recorded in this area for the first time and their sites are outside their known range in Slovakia.

MORPHOLOGICAL AND BIOINFORMATICS STUDY FOR RADIX AURICULARIA SNAILS IN FRESHWATER IN BASRAH PROVINCE, IRAQ

Radix auricularia (Lymnaea auricularia) snails are the main intermediate host of Fasciola gigantica in the middle and South of Iraq. Recently, some studies suggest these snails are not present in Iraq, in particular Basrah province. Thus, the current study was aimed to use the bioinformatics analysis in the determination of Radix sp. in Basrah and also aimed to identify morphological characteristics of this species in the AL-Sewaib river, Basrah. Four hundred R. auricularia snails were collected from the AL-Sewaib river during May 2018 to March 2019. The results of the bioinformatics analysis showed according to the mitochondrial cytochrome c oxidase subunit I, the presence of R. auricularia snails in Basrah province and these snails are more closely related to Iranian R. auricularia snails than those for European counties and Russia. This study also displayed the existence of the polymorphism phenomenon in R. auricularia snails collected from the AL-Sewaib river which there were six different forms (A, B, C, D, E and F). These forms had variations in the colour and form of shells along with a variation in the number of eggs (30-56) per an egg mass. In addition to this, these R. auricularia forms had variations in their distributions. Form E had the highest spread percentage (33%) followed by 17, 15, 14, 11 and 10% for forms B, D, C, A and F, respectively. These forms had also variations in their morphological characteristics. The largest form was the form D whereas the smallest form was the form B but other forms A, C, E and F were similar and had moderate sizes.Thus, the current study concludes the existence of R. auricularaia snails in Basrah as a representative city for the southern part of Iraq and also confirmed the presence of the polymorphism phenomenon in the members of R. auricularaia obtained from the AL-Sewaib river.

ECOLOGICAL VALENCE OF A MOLLUSK OF THE GENUS RADIX IN THE MIDDLE RIVER OF THE LOWER VOLGA

Background. The Lower Volga basin has undergone significant changes caused by the development of human economic activity. However, its high significance in terms of assessing and preserving the biodiversity of natural complexes on the territory is very relevant. Small and medium-sized tributaries support the vast biodiversity of the flora and fauna of the Lower Volga and their transformations in the landscape of catchment areas and the hydrological regime create prerequisites for changing the entire natural complex of the region. The assessment of the state of rivers based on macrozoobenthos indicators has various advantages over other approaches, primarily in the species diversity and structure of bottom communities that reflect the state of the ecosystem over a long period. One of the important components of the benthic groups are mollusks as representatives of one of the most numerous animal species. Representatives of malacofauna form part of the food chain in the transmission of energy, are part of the diet of various species of fish and waterfowl. Therefore, the aim of the work is to study the distribution and features of quantitative indicators of Radix (Radix) auricularia (Linnaeus, 1758) under the influence of abiotic and biotic environmental factors in the Samara River. Materials and methods. The study was conducted in the summer of 2017 in the Samara River from the source to the mouth. Cameral processing was carried out, where their species identity was established, quantitative indicators were calculated, including morphometric measurements of shells. The environmental assessment was carried out using modern statistical methods. Results. Mollusk individuals were found in various biotopes of the river, characterized by a variety of abiotic and biotic conditions. The occurrence of the species in the river was 65%, with the highest registration at the stations of the lower course. The quantitative indicators varied significantly at different stations. The highest values of abundance and biomass were recorded in the small reservoir of the upper current. Analysis of changes in the morphometric characteristics of the shells of the species in different parts of the river allowed us to identify the largest individuals in the lower reaches, where the greatest anthropogenic impact on the water quality in the river. Thus, the changes caused by humans had less impact on the mollusk than the absence of natural favorable environmental factors. The assessment of the influence of various environmental factors on the mollusk R. (R.) auricularia allowed us to establish significant environmental variables of the environment. Conclusions. The presented results significantly supplement the available data on the biology and ecology of the mollusk R. (R.) auricularia in the region. All the extensive material made it possible to better understand the biotic preferences of the species in rivers under various environmental conditions. The results will make it possible to more effectively assess the state of inland water bodies with similar abiotic and biotic conditions.

First confirmed record of Trichobilharzia franki Müller & Kimmig, 1994, from Radix auricularia (Linnaeus, 1758) for Austria

Avian schistosomes are of medical and veterinary importance as they are responsible for the annually occurring cercarial dermatitis outbreaks. For Austria, so far, only Trichobilharzia szidati Neuhaus 1952 was confirmed on species level as causative agent of cercarial dermatitis. Here we present the first record of Trichobilharzia franki Müller & Kimmig 1994 in Austria. The species was detected during a survey of digenean trematodes in Upper Austrian water bodies. Furthermore, we provide DNA barcodes of T. franki as well as measurements of several parasite individuals to indicate the intraspecific diversity. We also recommend the usage of an alternative primer pair, since the “standard COI primer pair” previously used for Schistosomatidae amplified an aberrant fragment in the sequence of T. franki. Overall, our study shows how limited our knowledge about occurrence and distribution of avian schistosomes in Austria is and how important it is to acquire such a knowledge to estimate ecological and epidemiological risks in the future.

Mid-Holocene palaeohydrochemistry and palaeohydrology of Yamdrok Yumtso, southern Tibetan Plateau, reconstructed from δ18O and δ13C of fossil shells of the gastropod Radix auricularia

Palaeohydrochemical and palaeohydrological changes of lakes have seldom been reconstructed from the fossil shells of the gasropod Radix auricularia, which is a new, and potentially high-resolution environnmental archive. We conducted a geochemical and stable isotope study of the shells of Radix from the exposed fluvio-lacustrine sediments near Lake Yamdrok Yumtso in the southern Tibetan Plateau. Our aims were to determine the sedimentary environment, palaeo-lake hydrochemistry and hydrological status. AMS 14C and OSL dating indicates that a lake-level stage of Yamdrok Yumtso higher than that of today occurred during ~4.7–1.2 cal. kyr BP. Results of Sr/Ca, δ13C and δ18O analysis of the fossil shells of Radix auricularia indicate that the lake-level fluctuations were mainly controlled by changes of the Indian Summer Monsoon; decreasing evaporation during the mid- to late-Holocene was also responsible. In addition, based on the geochemical relationship between Radix sp. shells and the ambient water in lakes, the values of δ18OPalaeo-water and Sr/CaPalaeo-water reconstructed using the fossil shells of Radix auricularia are −8.2‰ to −5.1‰ and 0.0012 to 0.0057, respectively. Further, based on the values of δ18Oshell, together with geomorphological evidence, we infer that Yamdrok Yumtso was a closed lake system, and we estimate its possible extent during the interval of high lake-level. In addition, we speculate that the water level of Yamdrok Yumtso at this time exceeded 4448.9 m a.s.l., but was less than 4451 m a.s.l., and that the major separation of various components of the Yamdrok Yumtso system occurred after 1.2 kyr BP.

TREMATODE FAUNA OF MOLLUSKS OF THE KATTAKURGAN RESERVOIR OF THE SAMARKAND REGION

The paper presents research data on the fauna and qualitative composition of trematode cercaria of the families that maturate in mollusks, namely, Lymnaeidae, Planorbidae, and Physidae of the Kattakurgan Reservoir of the Samarkand Region. The work was carried out in the spring-summer and autumn time of 2017–2019 in the Kattakurgan Reservoir. There were 7510 mollusks (Lymnaeidae – 4116 specimens, Planorbidae – 2280 specimens and Physidae – 620 specimens) collected and investigated according to the known malacology methods. As our collections showed, 5 species were found here in 2017–2019 – L. auricularia, L. subdisjuncta, Costatelia acuta, Planorbis planorbis, and Anisus covexiusculus. Among them – Lymnaea auricularia and L. sudisjuncta live on the lower layers of plants, and are sometimes found on the slopes of the dam. Seven species of mollusks infected with trematode larvae were found in the examined reservoir. We found that the fauna of trematode cercaria from the studied reservoir is represented by 16 species belonging to 15 genera. The richest species diversity of cercariae in mollusks Planorbis planorbis is 6 species. Cercariae are represented by 5 species in mollusks Radix auricularia in the studied region.