Aquatic Leaf Research Articles

Boosting Interfacial Electron Transfer and CO2 Enrichment on ZIF-8/ZnTe for Selective Photoelectrochemical Reduction of CO2 to CO.

Artificial photosynthesis is an effective way of converting CO2 into fuel and high value-added chemicals. However, the sluggish interfacial electron transfer and adsorption of CO2 at the catalyst surface strongly hamper the activity and selectivity of CO2 reduction. Here, we report a photocathode attaching zeolitic imidazolate framework-8 (ZIF-8) onto a ZnTe surface to mimic an aquatic leaf featuring stoma and chlorophyll for efficient photoelectrochemical conversion of CO2 into CO. ZIF-8 possessing high CO2 adsorption capacity and diffusivity has been selected to enrich CO2 into nanocages and provide a large number of catalytic active sites. ZnTe with high light-absorption capacity serves as a light-absorbing layer. CO2 molecules are collected in large nanocages of ZIF-8 and delivered to the ZnTe surface. As evidenced by scanning electrochemical microscopy, the interface can effectively boost interfacial electron transfer kinetics. The ZIF-8/ZnTe photocathode with unsaturated Zn-Nx sites exhibits a high Faradaic efficiency for CO production of 92.9% and a large photocurrent of 6.67 mA·cm-2 at -2.48 V (vs Fc/Fc+) in a nonaqueous electrolyte at AM 1.5G solar irradiation (100 mW·cm-2).

Can titanium dioxide nanoparticles modulate the effects of zinc oxide nanoparticles on aquatic leaf litter decomposition?

The potential impacts of metallic nanoparticles (NPs) at environmental levels on freshwater ecosystems cannot be ignored due to their frequent release. The most widely used metallic oxide, ZnO NPs and TiO2 NPs (100 ng L−1) were applied to explore their single and combined effects on leaf litter decomposition. Although ZnO NPs and TiO2 NPs alone or in combination increased 22.68%–41.17% of the leaf decomposition rate, they performed different toxic mechanisms in ecological processes. The microbial mass and enzyme activities significantly increased after acute exposure, but significantly decreased after chronic exposure to ZnO NPs. The activity of BG was the most sensitive factor that was decreased by 66.22%, 56.97%, and 39.39% after 21-day exposure to ZnO NPs, TiO2 NPs, and in combination, respectively. In addition, the analysis of Fourier transform infrared spectroscopy suggested a novel perspective on understanding the promoting mechanism. The promotion effect of ZnO NPs relied on the enhanced decomposition of refractory organics and easily degradable substances due to the contribution of Anguillospora, Pyrenochaetopsis, and Bipolaris. The single exposure to TiO2 NPs and combined exposure with ZnO NPs promoted microbial mass and hydrolase activities, with the stimulating effect attributed to the enhanced decomposition of soluble substances. Therefore, the results highlight the importance of chemical analysis of decomposed leaves to evaluate the potential threat of metallic NPs to the function of freshwater ecosystems.

Emerald ash borer invasion of riparian forests alters organic matter and bacterial subsidies to south Michigan headwater streams.

Emerald ash borer (EAB) has killed millions of ash trees in the United States and Canada, yet impacts on terrestrial-aquatic linkages are largely unknown. Ash tree death along streams creates canopy gaps, increasing light to riparian plants and potentially affecting organic matter subsidies. Six EAB-related canopy gaps along streams across a gradient of timing of EAB invasion in Michigan were characterized for coarse woody material (CWM), terrestrial and aquatic leaf litter and their associated bacterial communities, and macroinvertebrates upstream, downstream, and at the center of the gap. Stream sites downstream of EAB-related canopy gaps had significantly lower dissolved oxygen and macroinvertebrate diversity than sites upstream and at the gaps. Yet there was no difference in CWM or aquatic leaf litter, likely due to downstream movement of organic matter from upstream riparian sources. Low abundance bacterial amplicon sequence variants unique to gap or forest were detected in leaves and leaf litter, suggesting that EAB-related canopy gaps altered leaf-associated bacterial communities. Overall, EAB invasion indirectly impacted some variables, while organic matter dynamics were resistant to change.

Co-exposures of acid rain and ZnO nanoparticles accelerate decomposition of aquatic leaf litter

The pattern of acid rain is dependent on the ratio of SO42− and NO3−, which change may affect the dissolution activity of dull heavy metals in the aquatic environment and further complicate the ongoing challenge of ecosystem stability and increase risks. In this study, we assessed the combined effects of acid rain (SO42-: NO3- was 2:1, 1:1, and 1:2) and ZnO nanoparticles (30 ng L-1) on plant litter decomposition through a microcosm experiment. The highest dissolution of ZnO nanoparticles was achieved when the SO42-: NO3- ratio was 1:2, and there were no significant differences among other treatments. The fungal biomass showed significant decreases under acute exposures but tended to be adaptive during chronic exposures. The co-exposure significantly stimulated the activities of leucine-aminopeptidase, glycine-aminopeptidase, polyphenol oxidase, and cellobiohydrolase. Besides, the fungal diversity and the relative abundance of some functional genera (e.g. Anguillospora) were enhanced when the SO42-: NO3- ratio was 1:2 and 2:1. In conclusion, the decomposition rate of plant litter was increased by 123–204% by co-exposures. Collectively, the findings underline the importance of considering environmental context to assess nanoparticle toxicity.

Using a Paired Chironomid δ18O and Aquatic Leaf Wax δ2H Approach to Reconstruct Seasonality on Western Greenland During the Holocene

AbstractThe Arctic hydrological cycle is predicted to intensify as the Arctic warms, due to increased poleward moisture transport during summer and increased evaporation from seas once ice‐covered during winter. Records of past Arctic precipitation seasonality are important because they provide a context for these ongoing changes. In some Arctic lakes, stable isotopes of oxygen and hydrogen (δ18O and δ2H, respectively) vary seasonally, due to seasonal changes in precipitation δ18O and δ2H. We reconstruct precipitation seasonality from Lake N3, a well‐dated lake sediment archive in Disko Bugt, western Greenland, by generating Holocene records of two proxies that are produced at different times of the year, and therefore record different lake water seasonal isotopic compositions. Aquatic plants synthesize waxes throughout the summer, and their δ2H reflects winter‐biased precipitation δ2H at Lake N3, whereas chironomids synthesize their head capsules between late summer and winter, and their δ18O reflects summer‐biased precipitation δ18O at Lake N3. During the middle Holocene at Lake N3, aquatic plant leaf wax was strongly 2H‐depleted, while chironomid chitin was 18O‐enriched. We guide interpretations of these records using sensitivity tests of a lake water and energy balance model, where we change precipitation amount and isotope seasonality inputs. The sensitivity tests suggest that the contrasting trends between proxies were likely caused by an increase in precipitation amount during all seasons and an increase in precipitation isotope seasonality, in addition to proxy‐specific mechanisms, highlighting the importance of understanding lake‐ and proxy‐specific systematics when interpreting records from sediment archives.

Molecular Characterization of Donacia provosti (Coleoptera: Chrysomelidae) Larval Transcriptome by De Novo Assembly to Discover Genes Associated with Underwater Environmental Adaptations.

Simple SummaryDonacia provosti is one of the major pests of aquatic crops. It has been widely distributed in the world causing extensive damage to lotus and rice plants. The larvae generally live-in water; however, little is known about the evolution and molecular mechanisms underlying the adaptation. Here, we generated the first larval transcriptome of D. provosti in order to identify potential genetic mechanisms of aquatic adaptation. About 5036 orthologous clusters were identified among four species and 494 unique clusters were identified from D. provosti larvae including the visual perception. Moreover, 93 orthologous gene pairs were found evolving under positive selection. Our results also showed that 4 gene pairs out of the 93 gene pairs were associated with the “mTOR signaling pathway”, which are predicted to be involved in the molecular mechanism of D. provosti adaptation to the underwater environment. In the light of the increasing availability of transcriptomic information for beetle underwater habitat and evolutionary analyses, it is expected that this paper will provide us with some novel insights into aquatic adaptation in beetles and serves as a foundation for future studies aiming to identify candidate genes underlying the genetic basis of aquatic adaptation in beetles.Donacia provosti (Fairmaire, 1885) is a major pest of aquatic crops. It has been widely distributed in the world causing extensive damage to lotus and rice plants. Changes in gene regulation may play an important role in adaptive evolution, particularly during adaptation to feeding and living habits. However, little is known about the evolution and molecular mechanisms underlying the adaptation of D. provosti to its lifestyle and living habits. To address this question, we generated the first larval transcriptome of D. provosti. A total of 20,692 unigenes were annotated from the seven public databases and around 18,536 protein-coding genes have been predicted from the analysis of D. provosti transcriptome. About 5036 orthologous cutlers were identified among four species and 494 unique clusters were identified from D. provosti larvae including the visual perception. Furthermore, to reveal the molecular difference between D. provosti and the Colorado potato beetle Leptinotarsa decemlineata, a comparison between CDS of the two beetles was conducted and 6627 orthologous gene pairs were identified. Based on the ratio of nonsynonymous and synonymous substitutions, 93 orthologous gene pairs were found evolving under positive selection. Interestingly, our results also show that there are 4 orthologous gene pairs of the 93 gene pairs were associated with the “mTOR signaling pathway”, which are predicted to be involved in the molecular mechanism of D. provosti adaptation to the underwater environment. This study will provide us with an important scientific basis for building effective prevention and control system of the aquatic leaf beetle Donacia provosti.

Comparison of Histological Changes in Mice Infected with the Cryptosporidium Parvum after Treatment with an Aquatic Leaf Extract of Salvia Officinalis, Pimpinella Anisum and, Spiramycin Drug

Background: Cryptosporidium parvum was cause Cryptosporidiasis .In this study the therapeutic effectof two aquatic extracts of plants in infected white mice with the C. parvum were examined and the resultswere compare with the therapeutic effect of Spiramycin through the study of the histological changes inmouse intestine. Methods: Thirty male mice were divided into six groups: group 1(non infected, negativecontrol ), group 2 (feeding with C. parvum oocysts, positive control ), group 3 (infected and treatment withleaf extract of Pimpinella anisum), group 4 (infected and treated with Salvia officinalis extract ,the group5 and 6 (infected and treatment with 5mg and 10mg Spiramycin Respectively ) The existence of oocystsin the feces of animals was counted daily during the therapeutic period .After two weeks; the changes ofcecum histological sections were examined. Conclusions: The oocysts counted in feces samples, showedsignificant differences between the treatments (P <0.05). The cecum histological changes in the group 3and 4 indicated that leaf extract of plants have moderate efficacy in treatment of C.parvum infection. Thececum appears close to normal at the concentration of 5mg Spiramycin there is no abnormal tissue in theconcentration of 10 mg.

Effects of riparian deforestation on benthic invertebrate community and leaf processing in Atlantic forest streams

Riparian deforestation may strongly affect stream functioning, with consequences for biodiversity and ecosystem services. These effects can be assessed using bioindicators relating to biotic community structure and ecosystem functioning. We evaluated the effects of riparian deforestation on 1. measures of community structure using aquatic benthic invertebrates, and 2. an aspect of ecosystem functioning, aquatic leaf processing. We selected sites along gradients of riparian land use in four Atlantic rainforest streams and measured physical and chemical properties for their association with riparian deforestation. We sampled benthic invertebrates and calculated metrics of community structure at each site. We measured rates of leaf processing using leaves of a common riparian tree, Guarea guidonia. Riparian deforestation was accompanied by increasing concentration of ammonia, water current and temperature and decreasing nightly oxygen saturation. Invertebrate diversity decreased and community metrics changed with deforestation as expected of negative impacts. Leaf processing decreased with deforestation. Although there were significant differences in physical and chemical measurements among streams, the gradients in community and ecosystem responses were similar, thus suggesting that both types of bioindicators were useful for monitoring changes and relating them to loss of biodiversity and ecosystem function.

Reconstructing Arctic Precipitation Seasonality Using Aquatic Leaf Wax δ2H in Lakes With Contrasting Residence Times

AbstractArctic precipitation is predicted to increase this century. Records of past precipitation seasonality provide baselines for a mechanistic understanding of the dynamics controlling Arctic precipitation. We present an approach to reconstruct Arctic precipitation seasonality using stable hydrogen isotopes (δ2H) of aquatic plant waxes in neighboring lakes with contrasting water residence times and present a case study of this approach in two lakes on western Greenland. Residence time calculations suggest that growing season lake water δ2H in one lake reflects summer precipitation δ2H, while the other reflects amount‐weighted annual precipitation δ2H and evaporative enrichment. Aquatic plant wax δ2H in the “summer lake” is relatively constant throughout the Holocene, perhaps reflecting competing effects of local summer warmth and increased distal moisture transport due to a strengthened latitudinal temperature gradient. In contrast, aquatic plant wax δ2H in the “mean annual lake” is 100‰ 2H depleted from 6 to 4 ka relative to the beginning and end of the record. Because there are relatively minor changes in summer precipitation δ2H, we interpret the 100‰ 2H depletion in mean annual precipitation to reflect an increase in winter precipitation amount, likely accompanied by changes in winter precipitation δ2H and decreased evaporative enrichment. Thus, unlike the “summer lake,” the “mean annual lake” records changes in winter precipitation. This dual‐lake approach may be applied to reconstruct past changes in precipitation seasonality at sites with strong precipitation isotope seasonality and minimal lake water evaporative enrichment.

Changes in decomposition rate and litterfall in riparian zones with different basal area of exotic Eucalyptus in south-eastern Brazil

Exotic species in riparian environments can influence the quantity and quality of litterfall in the ecological system. The objective of this study was to evaluate the influence of Eucalyptus leaves on litterfall and terrestrial and aquatic leaf decomposition in a riparian forest in São Paulo state, Brazil. Three riparian zones were evaluated, and they were designated as areas of low (L), medium (M) and high (H) Eucalyptus basal area, respectively. Each riparian area was evaluated by surveying its structure and floristic composition. The amount of litterfall was evaluated over one year, and leaves were collected in terrestrial and vertical collectors. We evaluated the rates of aquatic and terrestrial decomposition of Eucalyptus and native leaves within litterbags. In general, area H had lower species richness, a higher edge effect and high Eucalyptus litterfall. Area L had higher species diversity (H′, Shannon– Wiener index), higher Pielou’s equitability index (J′), and smaller amounts of Eucalyptus litterfall. Eucalyptus leaves had higher extractive and lignin content compared with that of native trees. Eucalyptus leaves had a lower decomposition rate, except for the aquatic environment in area M. Our results show that the presence of Eucalyptus in riparian zones can increase litterfall and reduce the rate of leaf decomposition, but more studies are needed to evaluate any changes in ecosystem function from Eucalyptus presence.

Stage-specific effects of fire: Effects of prescribed burning on adult abundance, oviposition habitat selection, and larval performance of Cope’s Gray Treefrog (Hyla chrysoscelis)

To effectively manage landscapes that support species with complex life cycles, managers should consider how current practices affect habitats these organisms rely on in each life stage. Prescribed fire is a landscape level disturbance that may alter both aquatic and terrestrial habitat characteristics. However, our knowledge of the effects of fire on amphibians is primarily limited to adult responses in terrestrial habitats. Here we present an integrated approach to test the response of Cope’s Gray Treefrogs (Hyla chrysoscelis) to fire across terrestrial and aquatic habitats by examining responses in tadpole performance and survivorship, adult abundance, and oviposition choice. In a common garden experiment, tadpoles reared with unburned leaf litter grew much faster those in pools with burned litter. To determine how fire in terrestrial and aquatic habitats acts to shape oviposition choice, we embedded aquatic mesocosms containing a substrate of either burned or unburned leaf litter within burned and unburned terrestrial plots. Observed oviposition was an order of magnitude higher in unburned terrestrial plots, regardless of the aquatic leaf litter treatment. This trend was not driven by differences in adult abundance in burned and unburned plots. Our findings are consistent with a scenario where adult treefrogs use terrestrial cues to preferentially breed in aquatic sites in unburned landscapes where tadpoles also experience greater growth. These insights highlight the value of adopting a multi-scale integrative approach that links stage and habitat specific effects on abundance, behavior, and performance to understanding the effects of anthropogenic and natural stressors on animal with complex life cycles.

A molecular basis behind heterophylly in an amphibious plant, Ranunculus trichophyllus

Ranunculus trichophyllus is an amphibious plant that produces thin and cylindrical leaves if grown under water but thick and broad leaves if grown on land. We found that such heterophylly is widely controlled by two plant hormones, abscisic acid (ABA) and ethylene, which control terrestrial and aquatic leaf development respectively. Aquatic leaves produced higher levels of ethylene but lower levels of ABA than terrestrial leaves. In aquatic leaves, their distinct traits with narrow shape, lack of stomata, and reduced vessel development were caused by EIN3-mediated overactivation of abaxial genes, RtKANADIs, and accompanying with reductions of STOMAGEN and VASCULAR-RELATED NAC-DOMAIN7 (VDN7). In contrast, in terrestrial leaves, ABI3-mediated activation of the adaxial genes, RtHD-ZIPIIIs, and STOMAGEN and VDN7 established leaf polarity, and stomata and vessel developments. Heterophylly of R.trichophyllus could be also induced by external cues such as cold and hypoxia, which is accompanied with the changes in the expression of leaf polarity genes similar to aquatic response. A closely-related land plant R. sceleratus did not show such heterophyllic responses, suggesting that the changes in the ABA/ethylene signaling and leaf polarity are one of key evolutionary steps for aquatic adaptation.

Sympatric occurrence of three leaf beetle species of Macroplea Samouelle, 1819 (Coleoptera, Chrysomelidae, Donaciinae) in Finland with a key to species in Northern Europe

ABSTRACTMacroplea Samouelle, 1819 is the only known fully aquatic leaf beetle genus with three European species that have earlier been classified by their assumed water salinity preferences. We studied the inter- and intraspecific variation of the specimens living in Northern Europe using both molecular (cytochrome c oxidase subunit I, COI) and morphological evidence. The variation in the COI sequences between M. mutica (Fabricius, 1792) and M. pubipennis (Reuter, 1875) was 8.4%–9%, M. mutica and M. appendiculata (Panzer, 1794) – 3.9%–4.9%, and M. appendiculata and M. pubipennis – 8.8%–9.2%. All three species were sampled together in the Bothnian Sea on the same water plants, showing that neither salinity nor plant species bear a decisive importance in their occurrence in the region. Phylogenetic results suggest the existence of two currently unknown Macroplea species that are evolutionarily close to M. appendiculata. A key to the Nordic species is provided.

Oxidative Enzyme Response of Watercress (Nasturtium officinale) to Sublethal Fuel Exposure

Biomarkers such as oxidase enzyme activity from flora exposed to chemicals in the water column and sediments have been widely used by ecotoxicologists to assess the quality of an environment. Biomarkers such as oxidase enzymes are especially useful indicators because they represent a direct biological response to environmental toxicity. A luminometer was used to quantify oxidase enzyme production in watercress (Nasturtium officinale) due to toxic chemical exposure of E85 (85% ethanol and 15% gasoline blend), gasoline, and 99% pure ethanol over a 72-h period in aquatic root exposure and volatile leaf exposure experiments. Aquatic exposure to E85 caused an increase in oxidative enzyme production while gasoline and ethanol caused no significant changes in oxidase concentrations. Aquatic root exposure results were compared to volatile leaf exposures where effects of E85, gasoline, and ethanol caused increases in oxidase production. Morphometric measurements were also conducted as plant stress comparisons to oxidative enzyme analyses. Measurements of root length showed increases in root growth at some concentrations of fuels with only the highest concentration of E85 resulting in a decrease in root growth when compared to the control.

Intraspecific leaf chemistry drives locally accelerated ecosystem function in aquatic and terrestrial communities.

Resource patchiness influences consumer foraging, movement, and physiology. Fluxes across ecosystem boundaries can extend these effects to otherwise distinct food webs. Intraspecific diversity of these cross-ecosystem subsidies can have large consequences for recipient systems. Here, we show intraspecific variation in leaf defensive chemistry of riparian trees drives local adaptation among terrestrial and riverine decomposers that consume shed leaf litter. We found extensive geographic structuring of ellagitannins, diarylheptanoids, and flavonoids in red alder trees. Ellagitannins, particularly those with strong oxidative activity, drive aquatic leaf decomposition. Further, spatial variation in these leaf components drives local ecological matching: in experiments using artificial food sources distinguished only by the chemical content of individual trees, we found decomposers both on land and in rivers more quickly consumed locally derived food sources. These results illustrate that terrestrial processes can change the chemistry of cross-ecosystem subsidies in ways that ultimately alter ecosystem function in donor and recipient systems.

Detection of an Enigmatic Plethodontid Salamander Using Environmental DNA

The isolation and identification of environmental DNA (eDNA) offers a non-invasive and efficient method for the detection of rare and secretive aquatic wildlife, and it is being widely integrated into inventory and monitoring efforts. The Patch-Nosed Salamander (Urspelerpes brucei) is a tiny, recently discovered species of plethodontid salamander known only from headwater streams in a small region of Georgia and South Carolina. Here, we present results of a quantitative PCR-based eDNA assay capable of detecting Urspelerpes in more than 75% of 33 samples from five confirmed streams. We deployed the method at 31 additional streams and located three previously undocumented populations of Urspelerpes. We compare the results of our eDNA assay with our attempt to use aquatic leaf litterbags for the rapid detection of Urspelerpes and demonstrate the relative efficacy of the eDNA assay. We suggest that eDNA offers great potential for use in detecting other aquatic and semi-aquatic plethodontid salamanders.

Combined effects of drought and the fungicide tebuconazole on aquatic leaf litter decomposition

Loss of biodiversity and altered ecosystem functioning are driven by the cumulative effects of multiple natural and anthropogenic stressors affecting both quantity and quality of water resources. Here we performed a 40-day laboratory microcosm experiment to assess the individual and combined effects of drought and the model fungicide tebuconazole (TBZ) on leaf litter decomposition (LLD), a fundamental biogeochemical process in freshwater ecosystems. Starting out from a worst-case scenario perspective, leaf-associated microbial communities were exposed to severe drought conditions (four 5-day drought periods alternated with 4-day immersion periods) and/or a chronic exposure to TBZ (nominal concentration of 20μgL−1). We assessed the direct effects of drought and fungicide on the structure (biomass, diversity) and activity (extracellular enzymatic potential) of fungal and bacterial assemblages colonizing leaves. We also investigated indirect effects on the feeding rates of the amphipod Gammarus fossarum on leaves previously exposed to drought and/or TBZ contamination. Results indicate a stronger effect of drought stress than fungicide contamination under the experimental conditions applied. Indeed, the drought stress strongly impacted microbial community structure and activities, inhibiting the LLD process and leading to cascading effects on macroinvertebrate feeding. However, despite the lack of significant effect of TBZ applied alone, the effects of drought on microbial functions (i.e., decrease in LLD and in enzymatic activities) and on Gammarus feeding rates were more pronounced when drought and TBZ stresses were applied together. In a perspective of ecological risk assessment and ecosystem management for sustainability, these findings stress the need for deeper insight into how multiple stressors can affect the functioning of aquatic ecosystems and associated services.

<b>Habitat structure determining the spatial distribution of ichthyofauna in a Brazilian stream

This work aimed to evaluate the relationship between parameters of fish communities and the habitat structure of a stream. Twenty three stretches six meters long were evaluated in the Samambaia stream located inside the Sumidouro Park, Rio das Velhas basin, state of Minas Gerais, Brazil. Fish samplings and habitat characterization were made for each stretch. Seven variables of habitat (vegetal cover, width, depth, substrate, flow, presence of aquatic plants and leaf litter) and two variables characterizing the longitudinal gradient (altitude and distance from the Sumidouro lagoon) were assessed. The fish community responded to habitat changes, presenting variation in richness and composition of species. Richness was positively influenced by the presence of leaf litter and aquatic plants. Furthermore, through similarity data (NMDS) and habitat structure (PCA), it was possible to observe the separation of the 23 stretches into two groups with a dissimilarity of approximately 90%. We concluded that the variation in richness and composition of species throughout the stream was strongly related to the variables of habitat structure. This variation is clearer when considering the longitudinal gradient which highlights a great difference between stretches nearer and farther from the mouth of Samambaia stream.

Flabellariopteris, a new aquatic fern leaf from the Late Triassic of western Liaoning, China

An aquatic fern leaf, Flabellariopteris mii Sun gen. et sp. nov. from the Late Triassic of Western Liaoning, China, is described and proposed as the type species of the new morphortaxon of the Marsileaceae. The fossil leaves are preserved as impression. No fertile and rhizomatic materials are found. The leaves attached at a common point on the top of the petiole are composed of two leaflets joined basally in an opposite arrangement. The petiole is slender. The leaflet is fan-shaped or semi-circular, and commonly divided into four wedge-shaped lobes. Terminal margin of lobes is usually incised, incisions shallow or deep, with bluntly rounded or notched apex. The veins are conspicuously dichotomous, but anastomoses and marginal vein are absent. The unique morphological features, including two-parted thin leaflets, size, shape, veins and slender petiole, indicate that the present specimen represents an aquatic fern, which is the oldest fossil record and the first megafossil evidence assignable to Marsileaceae from the Triassic floras.

Potential for passive internal dispersal: eggs of an aquatic leaf beetle survive passage through the digestive system of mallards

Long-distance dispersal of aquatic invertebrates is in many cases facilitated by resistant life stages surviving the passage through the gut of water birds. While this is well known for taxa like crustaceans and bryozoans, it has only very rarely been documented for aquatic insects. The fully aquatic leaf beetle Macroplea mutica shows a remarkably wide distribution throughout the whole Palearctic region, despite showing very little potential for active dispersal. The aim of this study was to test the potential for endozoochorous dispersal in Macroplea mutica by feeding beetle eggs to mallards (Anas platyrhynchos). It was hypothesised that eggs of these water beetles might survive internal transport within birds. Approximately 1% of ingested M. mutica eggs could be retrieved from faeces of mallards 2–8 h after ingestion. Larvae hatched from 20% of the retrieved eggs after gut passage. These results represent one of the first documented cases of insects surviving the gut passage through a water bird, and the first experimental evidence of the potential for bird-mediated endozoochorous dispersal of aquatic beetles. The possibility of internal transport could help to explain the remarkably wide distribution of an otherwise strikingly immobile beetle species.