Is bigger better? A possibility for adaptation of <Emphasis Type="Italic">Daphnia</Emphasis> to filamentous cyanobacteria in the face of global warming

Body size is a key determinant of fitness in Daphnia. Bigger size means higher feeding efficiency and reproduction. However, filamentous cyanobacteria have a more detrimental effect on larger daphnids. Predicted global warming is expected to reduce size of Daphnia and facilitate frequent occurrence of cyanobacteria. Therefore, we asked two questions: (i) does elevated temperature cause reduced size of daphnids, and (ii) is temperature-dependent size reduction adaptive in an environment dominated by filamentous cyanobacteria? To address these issues, we obtained 8 clones of the Daphnia longispina complex from artificially heated lakes and 8 clones from control lakes, and exposed them to a favorable food Scenedesmus obliquus and a mixture of S. obliquus and the filamentous cyanobacterium Cylindrospermopsis raciborskii in life table experiments at 16, 20, and 24°C. Individuals from heated lakes attained larger body size than those from control lakes. Moreover, exposure to the filamentous cyanobacterium led to reduced fecundity of Daphnia from the non-heated lakes and did not affect reproduction of Daphnia from the heated lakes. We conclude that Daphnia display some evolutionary adaptations to cope with filamentous cyanobacteria, linked to long-term exposition to elevated temperature. Our results violate broadly accepted assumptions that ectotherms are smaller in warmer environments.     

Metatrancriptomic analysis from the Hepatopancreas of adult white leg shrimp (<Emphasis Type="Italic">Litopenaeus vannamei)</Emphasis>

The amoeba, Mayorella viridis contains several hundred symbiotic green algae in its cytoplasm. Transmission electron microscopy revealed strong resemblance between symbiotic algae from M. viridis the symbiotic Chlorella sp. in the perialgal vacuoles of Paramecium bursaria and other ciliates. Although it is thought that the M. viridis and symbiotic algae could be model organisms for studying endosymbiosis between protists and green algae, few cell biological observations of the endosymbiosis between M. viridis and their symbiotic algae have been published. In this study, we characterized the specificity of endosymbiotic relationships between green algae and their hosts. Initially, we established stable cultures of M. viridis in KCM medium by feeding with Chlorogonium capillatum. Microscopic analyses showed that chloroplasts of symbiotic algae in M. viridis occupy approximately half of the algal cells, whereas those in P. bursaria occupy entire algal cells. The symbiotic algae in P. bursaria contain several small spherical vacuoles. The labeling of actin filaments using Acti-stain? 488 Fluorescent Phalloidin revealed no relationship between host actin filaments and symbiotic algal localization, although the host mitochondria were localized around symbiotic algae. Symbiotic algae from M. viridis could infect algae-free P. bursaria but could not support P. bursaria growth without feeding, whereas the original symbiotic algae of P. bursaria supported its growth without feeding. These data indicated the specificity of endosymbiotic algae relationships in M. viridis and P. bursaria.     

Freshwater anostracan, <Emphasis Type="Italic">Branchinella kugenumaensis</Emphasis>, as a potential controlling consumer species on toxic cyanobacteria <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis>

To evaluate the potential of Branchinella kugenumaensis for cyanobacterial bloom control relative to Daphnia, we conducted several feeding experiments on microcystin-free and microcystin-containing unicellular strains of Microcystis aeruginosa and colonial forms of Microcystis using B. kugenumaensis and Daphnia magna in a laboratory. Branchinella kugenumaensis showed higher filtration rates than those of D. magna in all treatments. In particular, the microcystin-containing unicellular strain supported the highest filtration rates of B. kugenumaensis among treatments. Daphnia magna reduced colonies less than 75 μm in length, whereas B. kugenumaensis could graze colonies less than 100 μm. The middle-sized group of B. kugenumaensis had a higher filtration rate than the small and large sized groups in a continuous feeding experiment for 4 days. In survival experiments, survivorships were not different between the two species, whereas ages at the beginning of the experiments affected their survival time. Our results showed that B. kugenumaensis grazed on toxic and colonial cyanobacteria at relatively high rates, indicating that locally abundant grazers like Branchinella may offer a better potential for bloom control than Daphnia.     

Diverse origins of enzymes involved in the biosynthesis of chloroplast peptidoglycan

Chloroplasts are believed to be descendants of ancestral cyanobacteria that had peptidoglycan layer between the outer and the inner membranes. Historically, the glaucophyte Cyanophora paradoxa and the rhizopod Paulinella chromatophora were believed to harbor symbiotic cyanobacteria having peptidoglycan, which were conventionally named “cyanelles”. In addition, the complete set of genes involved in the synthesis of peptidoglycan has been found in the moss Physcomitrella patens and some plants and algae. The presence of peptidoglycan-like structures was demonstrated by a new metabolic labeling technique in P. patens. However, many green algae and all known red algae lack peptidoglycan-related genes. That is the reason why we questioned the origin of peptidoglycan-synthesizing enzymes in the chloroplasts of the green algae and plants. We performed phylogenetic analysis of ten enzymes involved in the synthesis of peptidoglycan exploiting the Gclust homolog clusters and additional genomic data. As expected, all the identified genes encoded in the chromatophore genome of P. chromatophora were closely related to cyanobacterial homologs. In the green algae and plants, only two genes, murA and mraY, were found to be closely related to cyanobacterial homologs. The origins of all other genes were diverse. Unfortunately, the origins of C. paradoxa genes were not clearly determined because of incompleteness of published genomic data. We discuss on the probable evolutionary scenarios to explain the mostly non-cyanobacterial origins of the biosynthetic enzymes of chloroplast peptidoglycan: A plausible one includes extensive multiple horizontal gene transfers during the early evolution of Viridiplantae.     

Adequacy of planctomycetes as supplementary food source for <Emphasis Type="Italic">Daphnia magna</Emphasis>

The nutritional quality of daphnids diet can influence their growth, reproduction and survival. In aquatic ecosystems, bacteria can contribute significantly to Daphnia diet by supporting, for instances, their high needs for phosphorus. The laboratory feeding of the model organisms Daphnia spp. is algal based, but should be improved to allow their better performance. The aim of this study was to evaluate the potential of two planctomycetes, Gemmata obscuriglobus and Rhodopirellula rubra, from exponential and stationary growth phases as alternative or supplementary food source for Daphnia magna. The actinobacterium Arthrobacter sp. was used for comparison. The feeding with only bacteria showed the inefficacy of both planctomycetes and actinobacteria as the only food source. However, when used in supplement to Raphidocelis subcapitata, a decrease in the age of first reproduction, a significant increase in reproductive output, in somatic growth and in rate of population increase was found for the highest cell densities of bacteria tested. The typical pink coloration of these bacteria present in daphnids body and eggs confirmed bacterial absorption and metabolization of their pigment. Planctomycetes yielded better results than the actinobacteria Arthrobacter but G. obscuriglobus that possesses sterols did not induce a better performance comparatively to R. rubra. No relation could be established between the feeding treatments that allowed improvement of Daphnia performance and the different kind of Daphnia’ Fatty Acid Methyl Esters. The use of sonication to separate planctomycetal cells before feeding the daphnids proved to be efficient. We confirmed that R. subcapitata supplemented by bacteria allows a better growth performance of D. magna.     

Waterbird response indicates floodplain wetland restoration

Filamentous cyanobacteria disturb food collection in Daphnia by mechanical interference with the filtering apparatus by the long trichomes. The intensity of this interference depends on the water temperature and the Daphnia body size. However, Daphnia are capable of breaking down the filaments, therefore improving the palatability of the cyanobacteria. The main objective of this study was to test whether the shortening of cyanobacterial filaments and the ensuing clearance rate of Daphnia would increase at higher temperatures to a greater degree in small-bodied Daphnia species than in large-bodied one. Laboratory feeding experiments were conducted in order to measure variation in the length of Cylindrospermopsis raciborskii trichomes and to calculate clearance rate. The filament length and the cyanobacteria clearance rate by Daphnia were calculated following their exposure to grazing by large-bodied D. pulicaria and small-bodied D. longispina in 20, 24, and 28°C. Rising temperature did not affect the intensity of breakage of C. raciborskii trichomes by D. pulicaria and caused decrease in clearance rate of this species, whereas for D. longispina, the temperature increase enhanced both filament breakage and clearance rate. We suggest that these temperature-related changes may affect relative competitive performance of Daphnia species in the presence of cyanobacteria.     

The Plankton Community of Sevan Lake (Armenia) after Invasion of <Emphasis Type="Italic">Daphnia</Emphasis> (<Emphasis Type="Italic">Ctenodaphnia</Emphasis>) <Emphasis Type="Italic">magna</Emphasis> Straus, 1820

The appearance of Daphnia (Ctenodaphnia) magna Straus, 1820 in the pelagial of Sevan Lake caused significant changes in the communities of planktonic algae, bacteria, and heterotrophic nanoflagellates. Phytoplankton and nanoflagellates were the most affected by the direct impact of D. magna, and the number and biomass of bacteria increased due to the reduction in the trophic pressure of the protists. It was also facilitated by the increased supply of phosphorus as a result of the activity of the cladocerans, as well as the decrease in the number and biomass of phytoplankton, which competes with heterotrophic bacteria for the nutrients.     

Phylogenetic signal of photobiont switches in the lichen genus <Emphasis Type="Italic">Pseudocyphellaria</Emphasis> s. l. follows a Brownian motion model

Lichen symbioses are defined as a symbiotic relationship between a mycobiont (generally an ascomycete) and one or more photobionts (green algae or/and cyanobacteria). It was proposed that cephalodia emancipation is an evolutionary driver for photobiont switch from chlorophyte to cyanobacteria. In this study we want to test the monophyly of cyanolichens and to measure the phylogenetic signal of the symbiotic relationship between cyanobacteria and a mycobiont partner in the lichen genus Pseudocyphellaria. This genus includes some species that have a chlorophyte as primary photobiont (and Nostoc in internal cephalodia), while others have only cyanobacteria. In a phylogenetic framework we measure the phylogenetic signal (or phylogenetic dispersion) as well as mapped photobiont switches performing stochastic character mapping. Results show that having cyanobacteria as main photobiont has a strong phylogenetic signal that follows a Brownian motion model. Seven clades in the phylogeny had an ancestor with cyanobacteria. Reversal to a green algae photobiont is rare. Several switches were estimated through evolutionary time suggesting that there was some flexibility in these traits along the phylogeny; however, close relatives retained cyanobacteria as main photobiont throughout the cyanolichen’s history. Photobiont switches from green algae to cyanobacteria might enhance ecotypical differentiation. These ecotypes could lead to several speciation events in the new lineage resulting in the phylogenetic signal found in this study. We give insights into the origin of lichen diversity exploring the photobiont switch in a phylogenetic context in Pseudocyphellaria s. l. as a model genus.     

The effect of bloom of filamentous green algae on the reproduction of yellowfin sculpin <Emphasis Type="Italic">Cottocomephorus grewingkii</Emphasis> (Dybowski, 1874) (Cottoidae) during ecological crisis in Lake Baikal

In shallow water areas of open Lake Baikal, filamentous green alga of the genus Spirogyra grows abundantly. Together with alga of the genus Ulothrix, it forms algal mats. According to our observations from 2010 to 2013, the spawning habitat conditions for the yellowfin sculpin Cottocomephorus grewingkii (Dybowski, 1874) (Cottidae) proved to be significantly disturbed in the littoral zone of Listvennichnyi Bay (southern Baikal), which, in turn, reduced the number of egg layings. With a 100% projective cover of the floor and a high density of green filamentous algae, the shallow-water stony substrate becomes completely inaccessible for spawning of the August population.     

To the knowledge of oribatid mites of the genus <Emphasis Type="Italic">Nothrus</Emphasis> (Acari,Oribatida, Nothridae) from Taiwan

Two species of oribatid mites of the genus Nothrus (Oribatida, Nothridae) were collected during an expedition to Taiwan in 2017. The species Nothrus anauniensis Canestrini and Fanzago, 1876 is redescribed and illustrated in detail; the main morphological traits for this species are summarized. A new species Nothrus xuejianensis Ermilov sp. n. is described; it differs from the closest species, Nothrus meakanensis Fujikawa, 1999 by the morphology and length of notogastral setae h₂ and number of subcapitular setae m.     

Effectiveness of cyanobacteria and green algae in enhancing the photosynthetic performance and growth of willow (<Emphasis Type="Italic">Salix viminalis</Emphasis> L.) plants under limited synthetic fertilizers application

The physiological response of plants to triple foliar biofertilization with cyanobacteria and green algae under the conditions of limited use of chemical fertilizers was investigated. Triple foliar biofertilization with intact cells of Microcystis aeruginosa MKR 0105, Anabaena sp. PCC 7120, and Chlorella sp. significantly enhanced physiological performance and growth of plants fertilized with a synthetic fertilizer YaraMila Complex (1.0, 0.5, and 0.0 g per plant). This biofertilization increased the stability of cytomembranes, chlorophyll content, intensity of net photosynthesis, transpiration, stomatal conductance, and decreased intercellular CO2 concentration. Applied monocultures augmented the quantity of N, P, K in plants, the activity of enzymes, such as dehydrogenases, RNase, acid or alkaline phosphatase and nitrate reductase. They also improved the growth of willow plants. This study revealed that the applied nontoxic cyanobacteria and green algae monocultures have a very useful potential to increase production of willow, and needed doses of chemical fertilizers can be reduced.     

Estimation of biotechnological potential and clarification of taxonomic status of <Emphasis Type="Italic">Parietochloris</Emphasis> genus microalgae (Trebouxiophyceae) from the CALU collection

Morphological, biochemical, and molecular genetic studies of green microalgae from the collection of cyanobacteria, algae, and algal parasites of St. Petersburg State University (CALU) (presumably belonging to the Parietochloris genus) were conducted in order to estimate biotechnological potential and clarify the phylogenetic position. It was determined that the studied strains have a close relationship to two genera from different classes (Lobosphaera (Trebouxiaceae) and Deasonia (Actinochloridaceae)) and can be of biotechnological interest as producers of valuable polyunsaturated fatty acids (especially arachidonic, linoleic, and α-linolenic).     

Molecular phylogeny of the marine <Emphasis Type="Italic">Prasiola</Emphasis> and <Emphasis Type="Italic">Rosenvingiella</Emphasis> species (Chlorophyta: Prasiolales) from southeastern Kamchatka

Molecular phylogenetic tools are often useful in distinguishing cryptic species with similar morphologies, but they can also be helpful in identifying morphotypes of a species, which displays completely different shapes. We performed molecular-phylogenetic analysis of supra-tidal green algae in the Kamchatka peninsula that belong to the order Prasiolales (Trebouxiophyceae, Chlorophyta). Based on rbcL sequences results, two new species were recorded for the first time in Kamchatka. Approximately 1.4% of the field-collected Rosenvingiella constricta had a unique uniseriate hood-like blade shape, although their rbcL sequences were 100% identical with typical multiseriate filamentous plants. Kamchatka’s population of R. constricta showed 99.4–99.6% identity in rbcL sequences with the populations from Canada and New Zealand. Another similar-looking Rosenvingiella species collected from the same locality had 93.5% identity of the rbcL gene sequence with R. constricta. Morphological and geographical analyses also suggested that this species might be a new species of the genus Rosenvingiella. Prasiola delicata was recorded for the first time in Kamchatka. The Kamchatka population of P. delicata showed 100% identity in rbcL gene sequence with the population from Vancouver, but differed from the Canadian population morphologically.     

Habitat uncertainty explains variation in offspring provisioning strategies in a temporary pond crustacean

Along with the development of nanotechnology, an increase in production and application of nanosized magnetite (Fe₃O₄) is expected. Though magnetite is considered relatively safe, information concerning potential hazards of synthetic magnetite nanoparticles with unique physico-chemical characteristics to aquatic organisms is still limited. In this study, we evaluated the toxicity of nanosized (27.2 ± 9.8 nm) and bulk (144.2 ± 67.7 nm) magnetite particles to different life stages of the aquatic crustacean Daphnia magna. In addition, phytotoxicity of the magnetite was evaluated using duckweed Lemna minor. The study did not reveal any statistically significant differences between the biological effects of nanosized and bulk magnetite particles. Both forms of magnetite induced very low toxicity (EC50 > 100 ppm) to D. magna and L. minor in the standard acute assays. However, it was demonstrated that at acutely subtoxic magnetite concentrations (10 and 100 ppm), the number of neonates hatched from D. magna ephippia was decreased. Moreover, short-term (48 h) exposure of neonate daphnids to these concentrations may significantly affect the long-term survival and reproductive potential of daphnids. These results indicate that substantial contamination of aquatic ecosystems by magnetite may disrupt the stability of cladoceran populations.     

Oribatid mites of the superfamily Trizetoidea Ewing, 1917 (Acari,Oribatida) from Peru

Two new species of the oribatid mite superfamily Trizetoidea (Acari, Oribatida) are described from Peru. Rhynchoribates (Rhynchoribatodes) rioyuyapichisensis Ermilov, sp. n. differs from the other species of the subgenus by the long flagelliform notogastral setae. Rhynchoppia puertoincaensis Ermilov, sp. n. is morphologically similar to R. capillata (Balogh, 1963), but differs by the shape and in a greater number of rostral teeth, in the number and a smaller length of notogastral setae, and in the number of genital setae. The genus Rhynchoppia (Balogh 1968) is recorded from the Neotropical Region for the first time, while Rhynchoribates (Rhynchoribatodes) brasiliensis Woas 1986 is new to the fauna of Peru.     

Effect of the vital activity products of beaver (<Emphasis Type="Italic">Castor fiber</Emphasis> L.) on the formation of zooplankton structure: Changes in the quantitative parameters of two cladocera species of different sizes in a beaver pound (in situ experiment)

The experiments were performed in microcosms situated on a control site and on a site regulated by beavers. Two cladoceran species of different sizes were placed in microcosms in different proportions. It was found that the vital activity products of Castor fiber L. promote an increase in the concentration of total phosphorus (P), a decrease in the N/P ratio in water, and an increase in the chlorophyll a concentration and the abundance and biomass of bacterioplankton. In such conditions, the abundance and biomass of the large species Daphnia (Ctenodaphnia) magna Straus was increased to the greatest extent when compared with background values when it was placed in combination with Ceriodaphnia dubia Richard or without it. Moreover, in the case of the combination of two crustacean species in microcosms, the abundance of C. dubia was lower when compared with the control site, while the abundance of D. magna was higher. The results of a bioassay showed that the productivity of C. dubia decreases in waters where D. magna is most abundant. We concluded that the formation of zooplankton in beaver ponds with specific features determined by the presence of large cladoceran species is provided by changes in the quantitative and qualitative parameters of food resources. This contributes to the massive distribution of large D. magna and its competitive relations with small C. dubia. According to the results of a bioassay, the vital activity products of D. magna can inhibit the fecundity of C. dubia.     

A new and little-known species of the oribatid mite genus <Emphasis Type="Italic">Benoibates</Emphasis> Balogh, 1958 (Acari,Oribatida, Oripodidae) from America

A new oribatid mite species of the genus Benoibates (Oribatida, Oripodidae) is described from Antigua Island. Benoibates antiguaensis sp. n. differs from B. muscicola Baranek 1981 in shorter adanal and notogastral setae and in spiniform anal setae. Benoibates crinitus (Berlese 1910) is redescribed from the USA, based on the topotypes.     

Engineering the growth pattern and cell morphology for enhanced PHB production by <Emphasis Type="Italic">Escherichia coli</Emphasis>

E. coli JM109?envC?nlpD deleted with genes envC and nlpD responsible for degrading peptidoglycan (PG) led to long filamentous cell shapes. When cell fission ring location genes minC and minD of Escherichia coli were deleted, E. coli JM109?minCD changed the cell growth pattern from binary division to multiple fissions. Bacterial morphology can be further engineered by overexpressing sulA gene resulting in inhibition on FtsZ, thus generating very long cellular filaments. By overexpressing sulA in E. coli JM109?envC?nlpD and E. coli JM109?minCD harboring poly(3-hydroxybutyrate) (PHB) synthesis operon phbCAB encoded in plasmid pBHR68, respectively, both engineered cells became long filaments and accumulated more PHB compared with the wild-type. Under same shake flask growth conditions, E. coli JM109?minCD (pBHR68) overexpressing sulA grown in multiple fission pattern accumulated approximately 70 % PHB in 9 g/L cell dry mass (CDM), which was significantly higher than E. coli JM109?envC?nlpD and the wild type, that produced 7.6 g/L and 8 g/L CDM containing 64 % and 51 % PHB, respectively. Results demonstrated that a combination of the new division pattern with elongated shape of E. coli improved PHB production. This provided a new vision on the enhanced production of inclusion bodies.     

New Species of Oribatid Mites of the Superfamily Oripodoidea Jacot, 1925 (Acari,Oribatida) from Trinidad and Tobago

Two new species of oribatid mites of the superfamily Oripodoidea (Acari, Oribatida) are described from Trinidad and Tobago. Scheloribates (Scheloribates) tobagoensis sp. n. (Scheloribatidae) differs fromS. (Scheloribates) papillaris Tseng, 1984 in the structure of the rostral and lamellar setae and leg solenidia, in the length of the prolamellae, the absence of aggenital setae, and in reduction of setae on tarsi III. Areozetes ryabinini sp. n. (Haplozetidae) differs from A. altimontanus Hammer, 1961 in the structure of the bothridial and notogastral setae and rostrum and in the number of claws on the tarsi.