Edible Frog Research Articles

Frogs, sentinels of DNA damage induced by pollution in Naples and the neighbouring Provinces

Many DNA mutation-based diseases recognised in Campania have recently been related to toxic substances in illegal dumping areas. We performed a comet assay on edible frog erythrocytes to evaluate DNA damage. Differences in genotoxic parameters were observed among populations. We show that severe DNA damage occurred in the north Campania where the emergence of environmental waste exploded recently. Although a similar magnitude of genotoxic damage was observed in some southern populations, it is attributable to a massive pesticide pollution related to intensive farming. The frog species analysed seems to be a good bioindicator for detecting genotoxic effects of chemical environmental hazards.

Effects of geographic distance, sea barriers and habitat on the genetic structure and diversity of all-hybrid water frog populations

The history of population size and migration patterns leaves its mark in the genetics of populations. We investigate the genetic structure of the edible frog, Pelophylax esculentus in the Danish archipelago and adjacent countries. This frog is of particular interest because it is a hybrid that, in this area, forms all-hybrid populations of diploid (LR) and triploid (LLR and LRR) genomotypes with no (or very few) adults of the parental species (LL and RR). This study is the first to cover the entire geographic range of Danish, Swedish and German all-hybrid populations, documenting their extent and providing a broad picture of their diversity of neutral genetic markers and genomotype proportions. With 18 microsatellite markers, we found that genetic diversity declines northwards in agreement with the glacial refuge and central-marginal hypotheses; however, populations on small and medium-sized islands are no less diverse than those on large islands and continental peninsulas. Isolation by distance exists across the archipelago with limited influence of fragmentation by brackish seawater. The extremely low genetic diversity in all-hybrid populations, compared with adjacent populations, may be responsible for the maintenance of their special breeding system. We also show large variation among ponds in proportions of LLR, LR and LRR genomotypes, but little geographic pattern in their distribution. Instead, we found relationships between the genomotype proportions and some of 15 habitat parameters monitored. Body size differences among LLR, LR and LRR further suggest ecological differences.

Amphibians of Poland's urban areas

For many reasons urban environment cannot affect positively on amphibian fauna, thus the most of amphibian species decrease in their abundance, become endangered or simply extinct in such areas. Scattered, inconsistent, sometimes simply not available data on amphibian fauna in towns do not facilitate action to protect the species. Therefore the collecting and compiling of the studies on amphibian fauna of different towns of Poland is important for the further research to reveal general rules in changes connected with urbanization. In sum, in 9 Polish towns 13 amphibian species plus one natural hybrid – the edible frog Rana kl. esculenta Linnaeus, 1758 were recorded. Eight to thirteen taxa were found in a town and it may be assumed that lack of other species occurring in Poland is connected only with their limited ranges. The current knowledge presented in the collected articles can become the starting point for the further studies onamphibian occurrence in urban environment and for appropriate protective measures in towns.

Amphibian communities in small water bodies in the city of Olsztyn

The aims of the study were determine the effects of anthropogenic pressure on the species composition and population size of amphibians of small water bodies in Olsztyn city (NE Poland). The presence of 11 amphibian species was noted in 83.5% of water bodies. The dominants were: the common frog Rana temporaria, the edible frog Rana esculenta, the pool frog Rana lessonae, the common toad Bufo bufo and the moor frog Rana arvalis. The fire-bellied toad Bombina bombina was an influent, while the common newt Triturns vulgaris, the common spadefoot Pelobates fnsciis, the tree frog Hyla arborea, the green toad Bufo viridis and the crested newt Tritimis cristatus were the recedents. The most frequent were “green frogs”, which occur in 71.9% of water bodies inhabited by amphibians (60.0% of all water bodies). The species characterized by the lowest occurrence frequency were the tree frog (6.0% and 5.0%, respectively), the green toad (5.4% and 4.5%) and the crested newt (3.6% and 3.0%). In the paper the urban pressure on amphibian communities is widely discussed.

Ranavirus in wild edible frogs Pelophylax kl. esculentus in Denmark

A survey for the amphibian pathogens ranavirus and Batrachochytrium dendrobatidis (Bd) was conducted in Denmark during August and September 2008. The public was encouraged via the media to register unusual mortalities in a web-based survey. All members of the public that registered cases were interviewed by phone and 10 cases were examined on suspicion of disease-induced mortality. All samples were negative for Bd. Ranavirus was isolated from 2 samples of recently dead frogs collected during a mass mortality event in an artificial pond near Slagelse, Denmark. The identity of the virus was confirmed by immunofluorescent antibody test. Sequencing of the major capsid protein gene showed the isolate had more than 97.3% nucleotide homology to 6 other ranaviruses.

The Harvest of Endemic Amphibians for Food in Eastern Madagascar

Deliveries of edible, endemic amphibians to a restaurant in eastern Madagascar were monitored over a five-month period in the 2008 austral summer. Each frog collector was interviewed on arrival and information was obtained on collection locality, methods, frequency, as well as recording the number of frogs delivered. A total of 3,233 frogs were delivered to the restaurant during the study, averaging 249 per week. All of the 21 interviews concerned frogs collected in forest habitats at night by teams of between one and three people. Collection occurred in four localities, one of which (Fierenana) necessitated public transport to deliver the frogs. Effort at Fierenana was typically higher than at other sites with collectors frequently spending at least one night in the forest and traveling around 8.3 hours between their homes and forest collection locations. Income generated went directly to the collectors, who always delivered the frogs in person, and supply was determined by their available time, frog abundance, and weather conditions. Although the restaurant had no stated minimum quantity for purchase, small frogs were refused and collectors aimed for a minimum of 60 large frogs per delivery. The income generated by local amphibian collectors at Fierenena was similar for non-threatened edible species destined for domestic consumption (0.29 US$) and the Critically Endangered Mantella milotympanum collected for overseas export (0.32 US$). The harvest of edible frogs provides important income for individual hunters but additional study is needed to investigate its impact on frog populations and to develop methods to link sustainable collection practices with forest management.

Gamete types, sex determination and stable equilibria of all-hybrid populations of diploid and triploid edible frogs (Pelophylax esculentus)

BackgroundTriploid individuals often play a key role in speciation by hybridization. An understanding of the gamete types (ploidy and genomic content) and stability of hybrid populations with triploid individuals is therefore of importance for exploring the role of hybridization in evolution. The all-hybrid populations of the edible frog, Pelophylax esculentus, are unique in their composition and genetic dynamics: Diploid (genotype LR) and triploid (LLR and LRR) hybrids depend on each other's different gamete contributions for successful reproduction and maintenance of the populations, as the parental genotypes P. lessonae (LL) and P. ridibundus (RR) are absent among adults. This study provides data and interpretations on gamete types and sex determination that are essential for understanding the function, evolutionary potential and threats of this intriguing system.ResultsDissection of metamorphs from a crossing experiment confirmed that sex determination is an XX-XY system with the Y confined to the L genome. From microsatellite analysis of parents and offspring from the crossings, gamete frequencies could be deduced: Triploids of both sexes mostly made haploid gametes with the genome they had in double dose, however LLR females also made approximately 10% LL gametes by automixis. LR frogs showed much variation in their gamete production. In LRR-rich populations, their LR sperm production was sufficiently high (22%) to explain the observed proportion of LRR males, the formation of which has not previously been understood. A model was constructed to calculate equilibrium genotype proportions for different population types on the basis of the gamete proportions found. These equilibria agreed well with empirical literature data.ConclusionIf population differentiation with respect to genotype proportions is really driven by gamete patterns, as strongly suggested by the present study, all-hybrid populations constitute not one, but several intrinsically different breeding systems. Tetraploidization could occur if the survival or fertility of both males and females increased. Whether introduction of hybrid or parental species individuals would threaten the all-hybrid populations cannot be predicted without further knowledge on the mechanisms behind non-hybrid inviability, but at least R genomes with Y factor are predicted to be invasive, if introduced, and could bring the populations to collapse.

De novo sequencing of peptides secreted by the skin glands of the Caucasian Green Frog Rana ridibunda

Amphibian skin glands are known to secrete various types of bioactive peptides. The array of these peptides is specific for every frog species. The present research deals with the identification of peptides isolated from the skin secretion of the Marsh frog R. ridibunda inhabiting the Kolkhida Canyon of the Caucasian region. The research is based on comprehensive high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) analysis of intact and chemically modified peptides. In particular, an oxidation procedure was applied directly to the crude skin secretion to open S--S loops whereas N-terminal acetylation was additionally carried out for one individual peptide. Sequences were determined by manual interpretation of electron capture dissociation (ECD) and collisionally induced dissociation (CID) tandem mass spectra. A total of 29 peptides were identified in the skin secretion of the Caucasian Marsh frog. The peptide profile is represented with disulfide-containing peptides belonging to the brevinin, esculentin and ranatuerin families, neuropeptides of the bradykinin and bombesin families. Two identified peptides belonging to the ranatuerins are the first peptides of this family discovered in the skin secretions of European frogs. Ten of the identified peptides coincide with those reported earlier for the European Edible frog. Another ten are identical to those found in R. ridubunda from the Moscow region. This fact verifies the described method as being an efficient analytical tool to compare intra- and interspecific variabilities.

What’s in a frog stomach? Solving a 150-year-old mystery (Diptera: Calliphoridae)

The nominal taxon Acanthosoma chrysalis Mayer, 1844 is revised, and a lectotype is designated. The species, which was described from Germany from a number of alleged parasites encysted in the peritoneal wall of the stomach of edible frogs, is shown to be based on first instar larvae of blow flies (Calliphor- idae). Argued from the shape and configuration of mouthhooks and abdominal cuticular spines, Acanthosoma Mayer, 1844 is shown to be a junior synonym of Onesia Robineau-Desvoidy, 1830, syn.n. ,a ndA. chrysalis is shown to be a junior synonym of O. floralis Robineau-Desvoidy, 1830, syn.n. This species is an obligate parasitoid of earthworms, and it is hypothesized that first instar larvae enter the frogs through infected earthworms.

Relationship of Endangered Amphibians to Landscape Disturbance

Abstract: We examined the density of 2 endangered amphibians, natterjack toads (Bufo calamita) and yellow‐bellied toads (Bombina variegata), in 150 breeding pools at each of 2 military training areas in the German state of Bavaria. We selected pools to ensure a wide range of observable ground disturbance resulting from military vehicular traffic during cross‐country maneuvers. Both species exhibited significant affinity for pools with high levels of ground disturbance. Natterjack toads preferred pools with 80–100% ground disturbance; yellow‐bellied toads preferentially occupied pools with 40–100% ground disturbance. Pools occupied by the target species were characterized by higher levels of bare ground and minimal vegetation. Among other observed amphibians, European edible frogs (Rana esculenta) preferred pools with ≤60% ground disturbance, less bare ground, more vegetative cover, and disturbance >2 years old. Common tree frogs (Hyla arborea), smooth newts (Triturus vulgaris), and alpine newts (T. alpestris) showed no preference for level of disturbance; densities were correlated to parameters apparently unrelated to disturbance. The habitat mosaic created by the heterogeneous nature of military training disturbance may help explain the high biodiversity that often characterizes military training areas. Preservation of native biodiversity is dependent on maintaining an appropriate disturbance regime that, in turn, maintains a habitat mosaic conducive to the presence of native species adapted to a broad disturbance—succession continuum. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):738–744; 2008)

Comparison of fatty acid, mineral and proximate composition of body and legs of edible frog (Rana esculenta)

The fatty acid profile and mineral composition (calcium, magnesium, sodium, phosphorus, potassium, iron, zinc, manganese, silicon, boron, cadmium, chromium, nickel, aluminium, copper, and lead) by Inductively Coupled Plasma-Atomic Emission Spectometry (ICP-AES) and the proximate composition of the body and legs of edible frog (Rana esculenta) were investigated. The fatty acids occurring in the highest proportions in both the body and leg of frogs were mystiric acid (C14:0, 1.13–2.30%), palmitic acid (C16:0, 19.76–23.23%), stearic acid (C18:0, 3.61–6.29%), palmitoleic acid (C16:1, 7.06–13.08%), oleic acid (C18:1n-9 cis, 10.83–16.71%), linoleic acid (C18:2n-6, 6.44–6.71%), γ-linolenic (C18:3n-6, 0.13–0.27%), linolenic (C18:3n-3, 2.32–3.37%), cis-11,14,17-eicosatrienoic acid (C20:3n-3, 4.71–7.72%), cis-5,8,11,14,17-eicosapentaenoic acid (C20:5n-3, 3.96–6.05%) and cis-4,7,10,13,16,19-docosahexaenoic acid (C22:6n-, 2.77–6.67%). Among the minerals determined, potassium was found to be highest, followed by phosphorus. Calcium, aluminium, cadmium, copper, lead, chromium, nickel, boron, silicon and zinc are found to be lower than the potential toxicity levels.

Possible antimicrobial defense by free sugars on the epidermal surface of aquatic vertebrates

Biochemical, lectin histochemical, and densitometrical methods demonstrated contents and spectra of free sugars in the skin of aquatic vertebrates (fishes: cod, marine trout, freshwater trout, perch; amphibians: Koa-Tao-Island caecilian, smooth newt, edible frog, South-African clawed toad; mammals: northern fur seal, common seal, otter, Capybara). Total free sugar contents, particu- larly sialic acids, were relatively higher in freshwater species (perch, Capybara) than in marine species. In amphibians, the caecilian and the newt showed higher amounts of free sugars than the anurans; strong reactions indicated a specific involvement of α-L-fucose in mucus functions. Lectin histochemistry demonstrated positive reactions in the stratum superficiale, the outer stratum spinosum, and specific cells of the fish epidermis. The integumental free sugar spectrum of the amphibians was narrow, with generally lower reaction intensities, except for mucus glands. In the mammals, the epidermal cells exhibited rather weak lectin histochemical staining, except for the northern fur seal and the Capybara, where the upper vital epidermis and corneal cells reacted strongly. The mammalian apocrine skin glands, particularly, exhibited positive reaction staining in their secretory endpiece. The free sugar spectrum was similar in all species: α-D-mannose, β-D-N-acetylglucosamine, α-D-N-acetylgalactosamine, α-D-galactose, β-D-galactose, α-L-fucose, sialic acids (mainly in fish epidermis and skin glands). High concentrations of free sugars on the skin surface possibly impede attacks of commensal skin micro-inhabitants (bacteria, fungi) against the integrity of the epidermis. This features a basic or general biological mechanism that operates before the specific immune system is activated.

MODIFICATION OF HOSTS' BEHAVIOR BY A PARASITE: FIELD EVIDENCE FOR ADAPTIVE MANIPULATION

Parasites relying on trophic transmission to complete their life cycles often induce modifications of their host's behavior in ways that may increase their susceptibility to predation by final hosts. These modifications have often been interpreted as parasite adaptations, but very few studies have demonstrated that host manipulation has fitness benefits for the parasite. The aim of the present study was to address the adaptive significance of parasite manipulation by coupling observations of behavioral manipulation to estimates of trophic transmission to the definitive host in the natural environment. We show that the acanthocephalan parasite Pomphorhynchus laevis manipulates the drifting behavior of one of its intermediate hosts, the amphipod Gammarus pulex, but not of a sympatric host, the introduced amphipod Gammarus roeseli. We found a 26.3-28.3 times higher proportion of infected G. pulex in the stomach content of one of the definitive hosts of P. laevis, the bullhead Cottus gobio, than in the benthos. No such trend was observed for G. roeseli. The bell-shaped curve of mean parasite abundance (MPA) relative to host size observed in G. pulex also supported an increased predation mortality of P. laevis-infected individuals compared to uninfected amphipods. Again, no such pattern was observed in G. roeseli. Furthermore, our results indicate that the modifications induced by P. laevis are specific to the definitive host and do not increase the risk of predation by inappropriate hosts, here the adult edible frog Rana esculenta. Overall, our study is original in that it establishes, under field conditions, a direct link between parasitic manipulation and increased transmission to the definitive host, and more importantly, identifies the specificity of the manipulation both in the intermediate host species and toward the definitive host.

Purification and characterization of antimicrobial peptides from the skin secretion of Rana dybowskii

Six antimicrobial peptides designated dybowskins were isolated from the skin secretion of Rana dybowskii, an edible frog in Korea. Dybowskin-1 (FLIGMTHGLICLISRKC) and dybowskin-2 (FLIGMTQGLICLITRKC) were isoforms differing in only two amino acid residues at the 7th and 14th positions from the N-terminus, and they showed amino acid sequence similarities with ranalexin peptides. Dybowskin-3 (GLFDVVKGVLKGVGKNVAGSLLEQLKCKLSGGC), dybowskin-4 (VWPLGLVICKALKIC), dybowskin-5 (GLFSVVTGVLKAVGKNVAKNVGGSLLEQLKCKISGGC), and dybowskin-6 (FLPLLLAGLPLKLCFLFKKC) differed in both size and sequence, and they were, in terms of amino acid sequence similarities, related to brevinin-2, japonicin-2, esculentin-2, and brevinin-1 peptides, respectively. All the peptides presented in this paper contained Rana-box, the cyclic heptapeptide domain, which is conserved in other antimicrobial peptides derived from the genus Rana. All the dybowskin peptides showed a broad spectrum of antimicrobial activity against the Gram-positive and Gram-negative bacteria (minimum inhibition concentrations (MIC), 12.5 to >100 μg/ml) and against Candida albicans (MIC, 25 to >100 μg/ml). Especially, dybowskin-4 with valine at its N-terminus was the most abundant and showed the strongest antimicrobial activity among all the dybowskin peptides. This result indicates that the dybowskin peptides from R. dybowskii, whose main habitats are mountains or forests, have evolved differently from antimicrobial peptides isolated from other Korean frogs, whose habitats are plain fields.

Choosing the Safest Route: Frog Orientation in an Agricultural Landscape

Orientation is a key component to successful movements between habitats. We hypothesized that barren agricultural landscapes hinder the ability of frogs to orient and move between habitats. Specifically, we predicted that when presented with a choice between a short route through a hostile environment and a longer but safer route, individuals would select the one that entails the least risk. During a field experiment, we translocated 104 Edible Frogs (Rana klepton esculenta) into a recently harrowed field according to two treatments: the distance to their pond of origin (5-70 m) and the distance to a wooded hedgerow (10-60 m). The frogs' ability to orient toward the pond decreased with pond distance and increased with distance to the hedgerow, but we did not detect interactive effects. In addition, frogs were more successful in orienting toward the pond under high wind conditions. We have shown that both the configuration of the landscape and weather variables influence the movement behavior of amphibians in agricultural settings, and these may have important implications for population persistence.

Distribution of amphibians and reptiles in central Poland: 1980-2000

Based on 3047 records from 97 recorders distribution maps were drawn for the amphibians and reptiles of central Poland (lirom 51°00’N to 52°15’N and from 18°20’E to 20°20’E). The study area was divided into 180 atlas fields based on the geographic grid. All data were gathered in 1980-2000, most of them (67%) however, in 1995-2000. 13 taxa of amphibians were found in 143 atlas fields and 6 species of reptiles were found in 121 atlas fields. The amphibians were (given with the number of atlas fields with the species found): 119 - Common frog Rana temporaria Linnaeus, 1758; 114 - Common toad Bufo bufo (Linnaeus, 1758); 97 - Moor frog Rana arvalis Nilsson, 1842; 94 - Fire-bellied toad Bomhina bombina (Linnaeus, 1761); 93 - Pool frog Rana lessonae Camerano, 1882; 87 - Tree frog Hyla arhorea (Linnaeus, 1758); 85 - Green toad Bufo viriiüs Laurenti, 1768; 72 - Smooth newt Triturus vulgaris (Linnaeus, 1758); 70 - Spadefoot Pelobales fuscus (Laurenti, 1768); 69 - Edible frog Rana kl. esculenia Linnaeus, 1758; 39 - Great crested newt Triturus cristatus (Laurenti, 1768); 30 - Marsh frog Rana ridibunda Pallas, 1771 and 28 - the Natterjack Bufo calamita Laurenti, 1768. The reptile species (given with the number o f atlas fields) were: 94 - Sand lizard Lacerta agilis Linnaeus, 1758; 72 - Slow-worm Anguis fragilis Linnaeus, 1758; 67 - Common lizard Lacerta vivipara Jacquin, 1787; 60 - Grass snake Natrix natrix (Linnaeus, 1758), 57 - Adder Vipera berus (Linnaeus, 1758) and 4 - the Smooth snake Coronella austriaca Laurenti, 1768. Six adult specimens of the European pond terrapin Emys orbicularis (Linnaeus) were also found, but breeding of this species in the area studied was not confirmed.

Effects of macrophage depletion on peritoneal inflammation in swiss mice, edible frogs and goldfish

SWISS mice, edible frogs and goldfish i.p. injected with zymosan (Z groups) develop peritoneal inflammation connected with a massive intraperitoneal accumulation of leukocytes, which is significantly diminished in mice and fish (but not frogs) by supplementation of zymosan with morphine (ZM groups). In order to check the putative role of resident peritoneal macrophages in morphine-modulated zymosan-induced peritonitis, some animals were depleted of resident macrophages by repeated i.p. injections of clodronate-liposomes (CL) followed by Z or ZM injection. In SWISS mice such CL-induced removal ofMac-3-positive cells (macrophages) resulted in an enhanced influx and prolonged accumulation of polymorphonuclear leukocytes (PMNs) in CL-Z and CL-ZM groups in comparison with their counterparts with intact macrophages. Nevertheless, supplementation of zymosan with morphine inhibited the early stages of peritonitis in CL-treated animals as it did in untreated mice. This indicates that intact peritoneal macrophages of SWISS mice are important for limiting PMN accumulation, perhaps mainly through the release of IL-10, but are not critical for the induction of anti-inflammatory effects of morphine during the early stages of peritonitis. Unexpectedly, macrophage depletion in CL-treated frogs and fish resulted in a lack of a typical peritonitis in both Z and ZM groups of these ectothermic animals.

Determination of polychlorinated dibenzo-p-dioxins and dibenzofurans and comparison of extraction methods for edible freshwater fish and frogs in South Korea by using a high-resolution GC/MS

Three different extraction methods were evaluated: Soxhlet extraction, accelerated solvent extractor extraction and alkali digestion with high-resolution gas chromatography/high-resolution mass spectrometry, for the analysis of edible freshwater fish and frogs. The recovery efficiencies for the different extraction methods were also compared. Using these extraction methods, the concentrations and spatial distributions of these compounds in freshwater fish and frogs (n = 99), collected from 31 locations on four major river systems (Han, Nakdong, Kum and Youngsan) and two wetlands in South Korea, were examined. The concentrations of total polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in all the freshwater fish and frog samples were analysed. The toxic equivalency (TEQ) concentration of PCDD/Fs in fish ranged from 0 (n.d.) to 1.309 pg I-TEQ g−1 wet weight. Detailed concentrations for different types of fish were as follows (pg I-TEQ g−1 wet weight): 0 (n.d.)–1.309 for crucian (mean 0.331, n = 28), 0.004–0.743 for carp (0.244, n = 10), 0.004–0.592 for dace (0.198, n = 8), 0.187–0.400 for cornet fish (0.287, n = 3), 0.164–0.410 for Korean piscivorous chub (0.303, n = 6), 0.105–0.516 for bass (0.310, n = 2), 0.451–0.812 for mullet (0.631, n = 2), 0.082 for long-nosed barbell, 0.100 for common Korean bitterling and 0.995 for dark chub. The total TEQ concentration ranged from 0 (n.d.) to 1.258 pg I-TEQ g−1 wet weight for the two kinds of frogs (n = 36) investigated: 0 (n.d.)–1.258 pg I-TEQ g−1 (mean 0.346, n = 29) for the bullfrog and from 0 (n.d.)–0.474 pg I-TEQ g−1 (0.185, n = 7) for the mountain frog.

Phylogenetic position of a renal coccidium of the European green frogs, 'Isospora' lieberkuehni Labbé, 1894 (Apicomplexa: Sarcocystidae) and its taxonomic implications.

'Isospora' lieberkuehni, an unusual isosporoid renal coccidium that parasitizes the European water frog was isolated from the edible frog, Rana kl. esculenta, in the Czech Republic. Sequencing of the small-subunit (SSU) rRNA gene showed that it belongs to the family Sarcocystidae, being closely related to a clade comprising members of the subfamily Toxoplasmatinae. The position within Sarcocystidae correlates with the mode of excystation via collapsible plates as postulated by previous authors. Phylogenetic, morphological and biological differences between 'Isospora' lieberkuehni and the other Stiedabody-lacking members of the genus Isospora justify separation of this coccidium on a generic level. Hyaloklossia Labbé, 1896 is the oldest available synonym and is herein re-erected. The original definition of the genus Hyaloklossia is emended based on recent observations.

Diet and trophic niche overlap of two ranid species in northern Italy

Diet of two syntopic populations of Rana dalmatina and R. synklepton esculenta were studied in order to collect data about competition and niche overlap in relation to habitats frequented. Field observations confirm previous ecological researches and show that the former species has a short aquatic phase during the mating period; it lives in woods after breeding relatively far from water. The edible frog, on the contrary, remains near damp areas during the whole activity period. Trophic niche breadth proved greater in R. dalmatina than in R. synklepton esculenta. Niche overlap between species was low, because of the different kind of habitats frequented, while that between sexes was low in R. dalmatina, because males and females show different activity patterns during the year. On the contrary, overlap was complete in R. synklepton esculenta. No correlation was found between the size of frogs and preys. In conclusion, frogs are opportunistic predators and our results suggest that maintaining a highly diversified habitat is useful for avoiding competition between species.