Family Sphaeriidae Research Articles

Peculiarities of the Species Composition, Abundance and Biotope Distribution of Mollusks Fam. Sphaeriidae in Rivers with a Many Lakes in the Catchment Area (by the Example of Water Courses of the Onega Lake Basin)

Using the example of the rivers of the Onega Lake basin, the species composition of mollusks of the Sphaeriidae family, their abundance, biomass, and contribution to benthic communities in rivers with many lakes in the catchment areas were analyzed. Patterns of spatial distribution of species across biotopes and gradients of environmental variables were traced. 26 species of mollusks of this family were identified, among them European-Siberian species predominate. Most of the species of mollusks of the family Sphaeriidae found by us have wide ecological ranges and are found in water bodies of various types. It was found that the contribution of Sphaeriidae to the species richness and functioning of aquatic communities in rivers in the conditions of branched lake-river systems (Lake Onega basin) exceeds the values usual for rivers with a small number of lakes in the catchment area. Using the ANOSIM and PERMANOVA methods, it was proved that the species composition of rocky rapids and riffles, sandy rifts and soft bottom soils is different. Using the IndVal test, seven species were shown to have a statistically significant association with one of these biotopes, and four of them, with rocky bottoms of river rapids and riffles. Using the NMDS method, it was shown that the greatest changes in the species composition of representatives of Sphaeriidae are observed when environmental conditions change from small streams with slow current and brown water to large rivers with fast current and clear water.

Off the conservation radar: the hidden story of Europe's tiny pea clams (Bivalvia: Sphaeriidae)

AbstractThis study highlights the conservation problems faced by the tiny freshwater bivalves of the family Sphaeriidae, also known as pea, pill, or fingernail clams (or mussels) in Europe. Despite their global distribution, assumed ecological importance, and potential uses, basic knowledge about their taxonomy, biology, and ecology is very limited and much lower than for the larger freshwater bivalve taxa. Immediate scientific priorities are required to fill knowledge gaps regarding their taxonomy, genetic diversity, distribution, reproductive cycle, ecosystem functions, and population trends. Such fundamental knowledge is necessary to identify specific threats and develop appropriate conservation actions. Deploying environmental DNA analysis at a large scale could be a valuable way to fill gaps in distribution and strengthen monitoring in areas where local taxonomic knowledge is lacking. Until taxon-specific management plans can be developed, we recommend that efforts concentrate on the general protection and restoration of wetland habitats, implementing pollution control measures, and managing invasive species. These actions should be complemented by community engagement through citizen science initiatives. Additionally, prioritising data collection to fill existing knowledge gaps and updating conservation statuses (Red Lists) based on comprehensive assessments will be crucial. Implementing these actions will provide a starting point for the broader protection of freshwater ecosystems, thus benefiting pea clams and other interconnected species within these habitats.

The fingernail clams (Bivalvia: Veneroida: Sphaeriidae) of Morocco: Diversity, distribution and conservation status.

BackgroundIn Morocco, many uncertainties surround the current diversity and distribution of the bivalve family Sphaeriidae. Such information, including taxonomy and conservation status, are vital for further studies to improve the knowledge of this family in Morocco and represents the first step towards the development of a national conservation plan for all freshwater bivalves.Between 2016 and 2019, several investigations were carried out to assess the diversity and distribution of Sphaeriidae in the different basins of Morocco, covering different types of habitat (lakes, springs, rivers and small ponds). The identification of specimens and their morpho-ecological features was based on morphological and morphometric analyses. The data on the general distribution of the collected species allowed the evaluation of their conservation status as well.The shell morphology and morphometric analyses revealed the existence of five species belonging to the genus Pisidium [P.casertanum (Poli, 1791), P. (cf.) personatum Malm, 1855, P.subtruncatum Malm, 1855, P.amnicum (O. F. Müller, 1774) and Pisidium sp.] and one species to the genus of Musculium [M.lacustre (O. F. Müller, 1774)]. Sphaeriidae were found in all Moroccan basins, except Bouregreg and Sakia El Hamra-Oued Eddahab Basins. The results showed that Sebou Basin was the species richest with the occurrence of the five species, while Loukkos and Sous-Massa Basins had the lowest-species richness with one species only. The conservation status of sphaeriids in Morocco was evaluated for the first time and resulted in P. (cf.) personatum and P.subtruncatum being proposed as Least Concern and Vulnerable, respectively, while the status of Regionally Extinct is suggested for both species P.amnicum and M.lacustre.New informationFirst evaluation of the diversity and species richness of the family Sphaeriidae in Morocco with an assignment of an updated conservation status of the recorded species.

Phyllodistomum kupermani n. sp. from the European perch, Perca fluviatilis L. (Perciformes: Percidae), and redescription of Phyllodistomum macrocotyle (L\xfche, 1909) with notes on the species diversity and host specificity in the European Phyllodistomum spp. (Trematoda: Gorgoderidae)

BackgroundEuropean species of the large genus Phyllodistomum Braun, 1899 had historically been erected based solely on morphological characters. Unfortunately, many of them are still poorly known and inadequately described. Molecular approaches are critical to delineate species which were impossible to differentiate based on morphology alone.MethodsNew samples of adult Phyllodistomum spp. were collected from the urinary bladder and/or ureters of European freshwater fishes and fixed to conduct a light and scanning electron microscopy study, and to obtain sequences of nuclear (ITS2 spacer and 28S rRNA gene), to be analysed in the context of a molecular phylogeny.ResultsBased on new findings, a new species of Phyllodistomum from the urinary bladder of the European perch, Perca fluviatilis, in Volga River basin, Russia, is described. Additionally, new data on the morphology and tegumental surface topography of P. macrocotyle (Lühe, 1909) Odhner, 1911 from ureters of the common rudd, Scardinius erythrophthalmus, is presented. The host range of P. folium, confirmed by DNA analysis, is extended to other cyprinid fish species.ConclusionsThe present study has again shown that species of the genus Phyllodistomum are in dire need of revision based on both molecular analysis and detailed morphological redescriptions of the forms attributed to the genus. Morphologically, P. kupermani n. sp. most closely resembles P. pseudofolium, a highly host-specific parasite of Gymnocephalus cernuus (L.), but molecular phylogenetic analyses based on ITS2 and 28S rDNA sequences showed that these species are distantly related. Phyllodistomum kupermani n. sp. was found to be phylogenetically most closely related to the type-species of Phyllodistomum, P. folium. Phylogenetic analyses revealed that Phyllodistomum kupermani n. sp. and P. folium formed a clade with other freshwater species for which cystocercous cercariae develop in bivalves of the family Sphaeriidae. The micromorphology and tegumental surface topography of P. macrocotyle revealed in the present study provide a valuable taxonomic criterion for congeneric species differentiation.

A contribution to the fauna of freshwater Bivalvia of waterbodies and watercourses of the Eastern slope of the Polar and Pre-Polar Urals

The article is devoted to the fauna of Bivalvia (family Sphaeriidae) of waterbodies and water-courses of the eastern slope of the Polar and Pre-Polar Urals. The fauna of freshwater clams of this region remains practically unexplored. This study aimed at identification of the species content of Bivalvia and publication of images of their shells. We analyzed both qualitative and quantitative samples of molluscs as well as fish stomach contents. The identification of the material was based on conchological features, including the hinge structure. In total, 31 sphaeriid species is reported, and the annotated check-list, brief zoogeographic characteristics of the fauna, and shell images are provided. Most species demonstrate a limited spatial distribution within the studied area. The causes of discrepancies between published lists of sphaeriid species are discussed.

First record of Pisidium subtruncatum Malm, 1855 (Bivalvia, Sphaeriidae) in an African cave

Studies on the bivalve family Sphaeriidae in North Africa are very limited at the surface water level, but even more for caves. During an expedition in 2019 to the Ait M’hamed cave (Oum Er Rabia Basin), six specimens of the genus Pisidium were collected. Morphometric and genetic analyses showed that these individuals belong to the species Pisidium subtruncatum Malm, 1855. This work is the first step towards future exploration of cave Sphaeriidae in North Africa.

Freshwater biogeography in Wallacea: The case of sphaeriid bivalves in the Malili lake system (Sulawesi, Indonesia)

Ancient lakes are renowned as freshwater hotspots of biodiversity and endemism. However, some of these water bodies are poorly studied with the minute pill clams in the genus Pisidium (family Sphaeriidae) being particularly overlooked. The Malili lake system is located on Sulawesi, which is the largest and possibly biologically most diverse Indonesian island within the biodiversity hotspot region of Wallacea. This lake system consists of 5 interconnected lakes that harbour a unique freshwater fauna including 42 mostly endemic mollusc species described to date. The only bivalves recognized in this lake system have been in the widespread genus Corbicula. We present new insights into the sphaeriid biodiversity of the ancient Malili lakes and provide the first fossil-calibrated phylogeny for this family to discuss the biogeographical history of the Wallacean Pisidium fauna including the dating of speciation events. Both morphological and molecular data suggest that the Malili lake system is inhabited by at least three Pisidium species, two of which are potentially endemic to these lakes. This diversity is probably derived from a single colonization event from the Oriental region. The fossil-calibrated phylogeny further indicates that intra-island diversification occurred well after the island was fully formed. Our study improves understanding of the overall sphaeriid biodiversity in Indonesia as well as the endemic fauna of the ancient lakes.

Bivalve molluscs of the subfamily Sphaeriinae in the Kama region waterbodies (the Middle Urals, Russia)

An annotated and illustrated check-list of species of the subfamily Sphaeriinae (family Sphaeriidae) of the Kama region (the Middle Urals, Russia), with enumeration of species’ localities, is presented. After examination of own collections and critical assessment of published data, 8 species from two genera ( Musculium and Sphaerium ) have been included into the final list. One of these species, Sphaerium asiaticum , is recorded for the first time from the studied area. The ecological characteristics of all species as well as remarks on their distribution within the region are provided. From the zoogeographical point of view most sphaeriine species of the studied area belong to the European-Siberian faunistic group.

Molluscan fauna of the lower reaches of the Syoyakha River (Yamal Peninsula)

The molluscan fauna of the Syoyakha (Zelenaya) River remain poorly explored even though the Syoyakha is one of the biggest rivers on the Yamal Peninsula. The Syoyakha River is remarkable for its high fish stocking capacity and it plays an important role in the seasonal distribution and migration of commercial fish species. Freshwater mollusks are known to be a major component of freshwater ecosystems and they make up a part of the diet of many commercially important fish species. The species composition of the mollusks inhabiting the lower reaches of the Syoyakha River has been studied. Five bivalve species of the family Sphaeriidae were found, namelySphaeriumcorneum(Linnaeus, 1758),Pisidiumcasertanum(Poli, 1791),P.globulare(Clessin in Westerlund, 1873),P.lilljeborgi(Clessin in Esmark et Hoyer, 1886) andP.dilatatum(Westerlund, 1897). In general, the molluscan fauna of the lower reaches of the Syoyakha River are taxonomically poor, which can be considered typical of freshwater invertebrate communities living at high latitudes. Another reason for the decline in species diversity may lie in the absence of any large transit watercourse in the basin in question allowing northward dispersion of the mollusks. The average density of mollusks in the watercourse stretch under study varied from 98.9 ind./m2to 620.5 ind./m2.P.globularesettlements had the highest recorded density of 1,442.9 ind./m2. The mollusks are confined to clayey, silty and sandy substrates with remnants of vegetation. The fauna is basically formed by widespread Palearctic and Holarctic mollusk species that have adapted to the extreme conditions of the Arctic. The findings may be used for hydrobiological and fishery characterization of the watercourse given that the recorded species ofS.corneum,P.globulare,P.lilljeborgi, andP.dilatatumare a major food item for important fish species, such as cisco, vendace, char, muksun, etc.

MALACOFAUNA OF THE KIVACH STRICT NATURE RESERVE

The malacofauna of the Kivach Strict Nature Reserve was studied. In total, 25 species of mollusks were found. This number included terrestrial gastropods 9 species, aquatic pulmonate gastropods 9 species, prosobranch gastropods 2 species, bivalves 5 species. For eight species the nature reserve's territory is close to the northern limit of their distribution in European Russia, and for two species it is close to the southern limit. Among the terrestrial gastropods one species (Arion subfuscus) prefers forest habitats; one species (Succinea putris) prefers living on wet land, but is also found in water on the trunks and branches of submerged trees; one species (Deroceras reticulatum) is synanthropic, found only in a residential area; and the rest prefer open sites. All the aquatic gastropods found in the nature reserve live in stagnant or slow-flowing water bodies. All the observed species of bivalves belong to the superfamily Unionacea. Three species live in lakes and river pools with slow stream. Two bivalve species (Unio crassus and Margaritifera margaritifera) inhabit rapids in the Suna River. The latter two species are red-listed. In fact, the freshwater pearl mussel Margaritifera margaritifera used to inhabit the Suna River in the past but went extinct as a result of human activities. The present-day population of M. margaritifera includes 400 individuals. These mussels were translocated from the Nemina River within the program for restoration of this species. A list of species of mollusks described from Karelia but not found in Kivach nature reserve is presented. It is quite likely, however, that some of these species do inhabit the territory of the reserve. This is especially so for small bivalves of the family Sphaeriidae. The resultant species list can serve as a starting point for further investigations of the reserve's malacofauna.

Nuclear DNA content in two Sphaeriidae species from Southern Chile (Bivalvia: Veneroida)

ABSTRACTThe family Sphaeriidae is a group of cosmopolitan freshwater clams that inhabit temporary and permanent fluvial and lacustrine environments around the world. In Chile, Sphaeriidae is represented by 11 species belonging to the genera Musculium, Pisidium and Sphaerium. In this study, the nuclear DNA content (or 2C-value) of Musculium argentinum (d’Orbigny, 1835) and Pisidium llanquihuense Ituarte, 1999 was estimated for the first time. Musculium argentinum showed a 2C-value of 3.7 ± 0.38 pg, whereas P. llanquihuense showed a 2C-value of 3.57 ± 0.36 pg. These 2C-values are within the range previously reported for Sphaeriidae (2.35–5.7 pg), which includes diploids and polyploids, amounting to 13 of the species examined around the world. Of the cytological data available for the family, the nuclear DNA content can have a unifying role in understanding the magnitude of the chromosome polymorphisms within this polyploid complex.

Freshwater molluscan fauna from the Florissant Formation, Colorado: paleohydrologic reconstruction of a latest Eocene lake

The freshwater molluscan assemblage from the uppermost Eocene Florissant Formation (34.07 ± 0.10 Ma), Colorado, USA, provides a reliable proxy in reconstructing past ecology and environmental characteristics of ancient Lake Florissant. In particular, stable-isotope analyses of aragonitic shell material contribute to our understanding of the paleohydrologic history of this ancient lake. Re-examination of molluscan taxonomy in the middle shale and caprock conglomerate (informal) units produces three sphaeriid bivalves (family Sphaeriidae, genus Sphaerium) and two pulmonate gastropod genera (family Planorbidae, genus Gyraulus; and family Lymnaeidae, genus Lymnaea). The middle-shale assemblage, representing quiet-lake deposition, is dominated by pulmonate gastropods; the shell material in all specimens in this unit has been replaced by silica. The caprock conglomerate assemblage, representing redeposition by a debris flow, is dominated by bivalves; specimens within the caprock conglomerate unit are aragonite, interpreted to be biogenic (original). Carbon and oxygen isotope analyses of the aragonite show a strong covariance (all molluscan data: r = 0.83; sphaeriids: r = 0.76) with consistent grouping (δ13C: 0‰ to −5.5‰, δ18O: +2‰ to −5‰) from all families. This result indicates that ancient Lake Florissant was “closed” and that evaporation had a stronger effect on isotopic values than precipitation, for the duration of the sampled interval. This finding is in agreement with our current understanding of how the sediments of the Florissant Formation were deposited within a lake that formed because of a paleoriver being dammed by debris flows.

Exploring high-mountain limnic faunas: discovery of a novel endemic bivalve species (Sphaeriidae : Pisidium) in the Nepal Himalayas

High-mountain regions are known to harbour considerable biodiversity, although it is not all well known. The terrestrial fauna of the world’s largest mountain range, the Himalayas, has been moderately well studied, but this is not the case with the limnic fauna, and especially molluscs. During intensive malacozoological field surveys conducted over the past 20 years, the bivalve family Sphaeriidae has been studied in Nepal along an elevational gradient from 100 to 4010 m above sea level (a.s.l.). Here we describe a new species of Sphaeriidae, Pisidium alexeii, sp. nov., based on comprehensive molecular phylogenetics, anatomy and shell morphology. The species can be clearly distinguished from all other sphaeriid species occurring in Nepal. A molecular phylogeny based on mitochondrial and nuclear data inferred the oriental biogeographical affinity of the new species. The species is ecologically restricted and only occurs at a few sites between 1010 and 1700 m a.s.l. A review and updated checklist of the sphaeriid fauna of Nepal is provided and biodiversity and biogeographical patterns are discussed.

Are the contours of the frontal section of shell valves in Bivalvia specific?

The diagnostic importance of the character of curvature of the frontal section of shell valves in Bivalvia on the basis of determining the constant angle of the logarithmic spiral is discussed. The contours of the frontal section of shell valves in several species of mollusks of the families Margaritiferidae and Sphaeriidae have been analyzed. It is shown that in different species of the family Sphaeriidae, the values of constant angles coincide. While performing graphic constructions, it was established that the contours of the frontal section of all studied species of pearl mussels and some spheriids do not correspond to the segment of the logarithmic spiral. It was noted that the hypothesis of the species specificity of this character was not confirmed; therefore, the curvature of the frontal section of shell valves cannot be used as the main character for the systematics and species identification of bivalves.

Food utilisation in fingernail and pill clams

The contents of digestive systems in six freshwater bivalve species of the family Sphaeriidae were investigated. Microorganisms in the stomachs and intestines of the bivalves were the same as found suspended in the water, which implies none or very limited preingestive selection, at least of the organic particles. Most of the organisms (coccal algae, diatoms, flagellates, euglenophytes, Zygnematophycaea, monadoid algae, bacteria) probably pass through the digestive system unharmed, as they were found alive even in the alimentary bolus in the hindgut. Probably only a small proportion of them is digested, in particular the bacteria and monadoid algae, the abundance of which decreased especially following starvation. In starved animals, food particles were also present in the digestive diverticula, apparently in order to increase food utilisation.

Does polyploidy occur in central European species of the family Sphaeriidae (Mollusca: Bivalvia)?

Abstract Some representatives of the bivalve family Sphaeriidae are assumed to be polyploid. In this study, 11 sphaeriid species (nine of the genus Pisidium, one of Musculium, and one of Sphaerium) inhabiting central Europe were studied karyologically, 10 of them for the first time. Analysis revealed high chromosome numbers (from 140 to 240). To elucidate the origin of high chromosome numbers, DNA contents were measured by flow cytometry in 5 of the studied species and, for comparison, in S. corneum and S. nucleus, which are known to be diploid (2n=30). Species with high chromosome counts yielded very similar DNA contents that are not higher than in the related species with low diploid numbers. This finding contradicts a possible origin of these species by recent polyploidization or hybridization of related species. Chromosome complements of the investigated species with high chromosome numbers differ from those with low 2n in their small chromosome size and the high proportion of subtelo- or acrocentric chromosomes. This indicates their possible origin either by an ancient polyplodization event followed by chromosomal rearrangements or by multiple chromosome fissions.

Nuclear DNA Content in Two Chilean Species ofPisidium(Veneroida: Sphaeriidae)

ABSTRACT The pill clams Pisidium chilense (d'Orbigny, 1846) and Pisidium huillichum (Ituarte, 1999) showed a 2C DNA content of 4.04 ± 0.4 pg and 2.35 ± 0.24 pg, respectively. The somatic DNA content of these 2 Chilean Pisidium Pfeiffer 1821 species is within the range described previously for diploid Heterodonta, despite the fact that both showed a high chromosome number (> 100–120 chromosomes) equivalent to the polyploid level described for other species of the genus. The nuclear DNA content is shown here for the first time for species of the family Sphaeriidae. The Pisidium, like other species, are not economically important as edible species, but they play a significant role in the dynamics of nutrient and energy cycles in freshwater bodies similar to that described for other Sphaeriidae species.

The significance of molluscs as paleoecological indicators of freshwater systems in central-western Argentina

The objectives of this study were to (a) analyze the distribution pattern of molluscs in freshwater systems from central-western Argentina, (b) investigate the key environmental factors affecting the species distribution, and (c) compare Quaternary and modern mollusc assemblages in order to evaluate the extent and limitations of freshwater molluscs as paleobioindicators. A total of 45 freshwater habitats were sampled for living molluscs. At each selected site, physical and chemical parameters were quantified, and living molluscs collected. Principal Component Analysis (PCA) was used for the ordination of sampling sites based on environmental variables. To explore the relationships between environmental variables and mollusc assemblages, a Canonical Correspondence Analysis (CCA) was performed. Data on fossil mollusc assemblages from three Quaternary alluvial successions outcropping in the area were combined with the modern data set by means of a Detrended Correspondence Analysis (DCA). Eight taxa were identified: Lymnaea viator, Heleobia hatcheri, Heleobia parchappii, Heleobia aff. parchappii, Chilina mendozana, Biomphalaria peregrina, Physa acuta, and a bivalve attributed to the family Sphaeriidae. Except for H. hatcheri and P. acuta, the species were also recorded as fossils in the area. Overall, the occurrence of molluscs in central-western Argentina appeared to be related to calm vegetated shallow water bodies. With the exception of H. parchappii that only occurred in saline waters (8–16 mS cm − 1 ), the mollusc assemblages were restricted to low salinities (below 1.9 mS cm − 1 ). Two main groups, indicative of different energetic environmental conditions related to the stability of the flow regime, were recognized: (1) L. viator, P. acuta, and B. peregrina occurred at lentic habitats (shallow lakes) or calm backwaters (pools) within lotic systems such as streams and rivers, (2) H. hatcheri, H. aff. parchappii, C. mendozana, and Sphaeriidae dominated in lotic habitats where a directional water flow exists. These same groups were recognized in the fossil record allowing the reconstruction of habitats that differed in the magnitude of the water flow.

Distribution and habitats of Pisidium viridarium Kuiper, 1956 (Bivalvia: Sphaeriidae) as reflected by the records of the National Freshwater Snail Collection of South Africa

The genus Pisidium includes some of the smallest bivalves in the family Sphaeriidae. The distribution of this group is cosmopolitan and they can utilize virtually any freshwater habitat,including peat bogs. Without doubt their centre of evolution lies in the Holarctic Region and theorigin of Pisidium is considered to be Mesozoic. This article focuses on the geographical distribution and habitats of P. viridarium, the most well represented species of this genus in the database of the National Freshwater Snail Collection (NFSC) of South Africa. Details pertaining to the habitats of the 639 samples of P. viridarium as recorded at the time of collection were extracted from the database of the NFSC. The number of loci (1/16 th square degrees) in which the 639 collection sites were located, was distributed in pre-selected intervalsof mean annual air temperature and rainfall, as well as intervals of mean altitude, to illustratethe frequency of occurrence within specific intervals. A temperature index was calculated for allmollusc species in the database from their frequencies of occurrence within the selected intervals and the results used to rank them in order of their association with low to high climatic temperatures. To evaluate the significance of the difference between frequencies of occurrence in, on, or at the various options for each parameter investigated, chi-square values were calculated. Furthermore, an effect size value was calculated to determine the contribution of each parameter towards establishing the geographical distribution of this species as reflected by the data in the database. Additionally, a multivariate analysis in the form of a decision tree was constructed from the data which enabled the selection and ranking of those variables that maximally discriminated between the frequency of occurrence of P. viridarium in, on, or at the various options for each parameter as compared to all other mollusc species in the database. The 132 different loci from which the samples were collected, display a relatively continuous distribution in the south-eastern part of the North West Province, the northern part of Gauteng, the central part of Mpumalanga and Lesotho. P. viridarium is sporadically distributed in the Eastern Cape and Free State, poorly represented in the Northern and Western Cape and completely absent from Limpopo. Its absence in certain areas of South Africa should be attributed to unfavourable environmental conditions rather than to a lack of opportunities to disperse: there are many agents and frequent opportunities for passive dispersal reported in literature for Sphaeriidae and the presence of P. viridarium in this country had already been recorded in 1950.This species was reported from 13 of the 14 habitat types represented in the database. However, the majority of samples were collected in marshes and in habitats of which the water conditions were described as clear, fresh and standing. The decision tree analysis indicated that temperature, altitude, type of water-body and substratum were the most important factors, of those investigated, that influenced the geographical distribution of this species in South Africa. It is known from reports in literature that bivalves can accumulate heavy metals from superficial sediments and the fact that P. viridarium is a filter feeder, a bottom dweller and can utilize a relatively large variety of habitats under a wide range of climatic conditions, could make it a useful candidate for monitoring heavy metal levels in freshwater habitats. It is recommended that the feasibility of such a possibility be investigated. In view of the reports from elsewhere in the world that Pisidium species can serve as intermediate hosts for helminth parasites that can affect the well-being of humans and animals, it is suggested that the potential of P. viridarium toact as intermediate host for harmful helminth parasites be evaluated. Efforts should also be made to update the geographical distribution of molluscs especially those that could play an important role in the life cycle of economically important helminth parasites.

Biology and immature stages of the clam-killing fly, Renocera pallida (Diptera: Sciomyzidae)

The larva of the Palaearctic Renocera pallida (FallĂŠn, 1820) is confirmed as a predator of small species of bivalve molluscs of the family Sphaeriidae. To date only the larvae of three Nearctic Renocera species (and larvae of two other species of Sciomyzidae in two genera) are known to have the same food preference. The life cycle, biology, larval feeding and behaviour are described for the first time and compared with that of the Nearctic Renocera. The systematic position and biology of Renocera in general are discussed. Descriptions of the egg, second and third larval instars and the puparium of R. pallida are presented, the main features of the egg and larvae are illustrated by scanning electron micrographs.