Vodní měkkýši přírodní rezervace Krabonošská niva [Aquatic molluscs of the Krabonošská niva Nature Reserve]

A floodplain of the Lužnice river at the Czech-Austrian border is protected by the Krabonošská niva Nature Reserve (Southern Bohemia, Czech Republic). This floodplain has a relatively natural character and, in addition to the Lužnice river, there is a high diversity of habitats at various stages of succession such as oxbows, pools and temporary wetlands. Altogether 20 species were found at 15 sites studied in 2021. Common and widespread gastropods Lymnaea stagnalis, Segmentina nitida and Planorbarius corneus belonged among the most often recorded species. Endangered Pisidium globulare was found at two sites, and only one non-native species Physa acuta was recorded. Molluscan assemblages are very similar to the assemblages of the neighboring Horní Lužnice Nature Reserve.

Food preferences of the great ramshorn Planorbarius corneus (Linnaeus, 1758) allospecies (Mollusca: Gastropoda: Planorbidae) from the Ukrainian river system

The “western” and “eastern” allospecies of the superspecies complex Planorbarius corneus (Linnaeus, 1758) sensu lato includes the most widespread and abundant gastropods in the Ukrainian aquatic fauna. The range of the “western” allospecies includes the north and central parts of Right Bank Ukraine, while the range of the “eastern” allospecies comprises the north-eastern and eastern parts of Left Bank Ukraine, and the extreme south (as far as the Danube River) of the Ukrainian steppe zone. The food preferences of these snails were established for the first time. Such data may provide the basis for studying the role of both allospecies in the food webs of the river systems of Ukraine.

Growth and Reproduction of Planorbarius corneus (Linnaeus, 1758) in Laboratory Conditions

This study presents the results of observation on growth and reproduction of Planorbarius corneus (Linnaeus, 1758) (Gastropoda, Pulmonata) over the course of several years of continuous rearing in the laboratory in order to use them as test organisms for toxicity testing of chemicals. Some growth and reproduction features (shell diameter increase, fecundity, hatching time and rate, age at first reproduction, juvenile survival), which could provide more information for culturing P. corneus in the laboratory, are presented. The quantitative results of growth and reproduction in laboratory conditions were obtained: heterogenous growth varied between 0.1 mm and 5.3 mm in individual snails, production of 0.6 egg masses per snail/day and 11 eggs per snail/day. A statistically significant negative correlation between initial snail size and growth was noticed. In the second part of the experiment, the reproductive output of 4 isolated snails was compared to that of permanently grouped snails. As a result, 2-fold decreased growth and 4-fold decreased reproductive output in the progeny of isolated animals was noticed.

Influence of heavy metal ions on ecotoxicological indicators of planorbarius corneus (Mollusca, Gastropoda, Pulmonata, Bulinidae)

The influence of different concentrations of ions of copper, zinc, nickel, manganese of the aquatic environment on the ecotoxicological indicators of the wide range and the most numerous species of malacofauna of Ukraine – Planorbarius corneus (Linnaeus, 1758) was studied. According to the level of toxic effect on the coils, the pollutants studied by us belong to the categories of low-toxic (Mn2+), moderately toxic (Ni2+), highly toxic (Zn2+) and highly toxic (Cu2+) substances. The values of subthreshold, sublethal, chronically lethal, and acute lethal concentrations for each of the used toxicants (mg/dm3) were determined according to the peculiarities of behavior and physiological condition of the experimental animals. As the concentrations of metal ions in the medium increase, the values of the latent period in P. corneus increase. The first signs of poisoning in animals are a weakening of motor activity and increased mucus secretion. At lethal concentrations (LC100) of these toxicants in experimental mollusks develops a rapid pathological process. By the end of the experiment, all individuals in this group die. With increasing concentrations of heavy metal ions, lethal time and lethal mean time decrease. The highest lethal time values were observed for manganese (II) ions, and the lowest for copper ions. The reversibility of mollusk poisoning by different concentrations of these metals was studied. Restoration of functions in the studied animals is carried out in reverse order. Under the action of the same concentrations of heavy metal ions, the duration of the lethal mean time is different. The value of the coefficient of endurance under the influence of heavy metals on the horn extract decreases from high to low concentrations. At subthreshold concentrations, this coefficient cannot be established due to the absence of 100 % death of individuals until the end of the acute experiment. The values of the adaptation coefficient are the highest for highly toxic metal (Cu2+) and the lowest for weakly toxic (Mn2+). Under the action of copper ions, the adaptation of animals to the effects of the toxicant is temporary, followed by depression.

Vodní měkkýši přírodní rezervace Horní Lužnice – revizní průzkum po více než 10 letech [Aquatic molluscs of the Horní Lužnice Nature Reserve – revision survey after more than 10 years]

The Lužnice River and its floodplain are protected in the Horní Lužnice Nature Reserve (Southern Bohemia, Czech Republic). The floodplain has a relatively natural character. Altogether 21 aquatic mollusc species were found at 40 sites. Lymnaea stagnalis, Physa fontinalis, Segmentina nitida and Planorbarius corneus belonged among the most often recorded species. Endangered Pisidium globulare was found. Non-native molluscs were not recorded. Only minimal changes were documented after the first research of this reserve, which was done more than 10 years ago.

A Mollusk Planorbarius corneus is an Intermediate Host of the Infectious Agent of Rostand’s «Anomaly P» in Green Frogs

Here we present the first new data about the mysterious «anomaly P» of green frogs (genus Pelophylax) in about 50 years. We established that the gastropod Planorbarius corneus could be an intermediate host (or vector) of the infectious agent of the anomaly P. Symmetrical cases of polydactyly, the anomaly «cross» and heavy cases of the anomaly P, which were previously found in natural populations in the European part of Russia and recently obtained in laboratory, can be caused by this infectious agent. As the most probable cause, we assume a species of trematodes, for which the first intermediate host is P. corneus, from which they infest tadpoles of green frogs.