Rotifer Species Research Articles

Lethal effects and ultrastructure of cellular uptake of ingested gold nanoparticles in the freshwater rotifer Brachionus calyciflorus (Monogononta: Brachionidae)

Much of the recent literature concerning the threat posed by anthropogenic microscopic pollution has focussed on marine organisms although freshwater environments face the same degree of pollution and therefore risk. Although several studies have documented the ingestion of nanoparticles (NPs) in species of the pelagic freshwater rotifer genus Brachionus, unambiguous evidence for its cellular uptake in this group remains lacking. We therefore used transmission electron microscopy (TEM) of ultrathin sections through the digestive tract of individuals of Brachionus calyciflorus exposed in vitro to citrate stabilized gold nanoparticles (AuCit NPs) in their culture medium to provide the first concrete evidence for the cellular uptake of NPs in rotifers, a group of organisms that comprise an important part of the zooplankton community. Using this method, AuCit NPs with average diameters of 8.5 ± 1.4 nm and 12.5 ± 1.5 nm could be localized clearly within large vacuoles within the stomach cells. Moreover, the occasional presence of pits containing AuCit NPs in the outer membranes of these cells hints that the particles are taken up by some form of endocytosis. In all cases, the ingestion of AuCit NPs showed lethal effects after only one day with virtually no individuals surviving more than two days of exposure. Combined with the TEM evidence above, we hypothesize that death might derive from some form of lysosomal overload. In total, our results document the potential threat that microscopic pollution also poses for freshwater organisms. Through this, we hope that additional emphasis in this context will be directed toward freshwater environments and the potential for such pollution both to enter as well as to move up the food chain via trophic transfer events.

Distribution of zooplankton in Lake Aslikul (South Urals, Russian Federation)

Fauna of aquatic invertebrates from various biotopes of the mineralized Lake Aslikul of the Asly-Kul natural park was studied. Lake Aslikul is the largest body of water in the Republic of Bashkortostan, one of the largest lakes in the Middle Volga region. Crustaceans dominated (67%) in the zooplankton in terms of the number of species. Typical eurythermal species such as Keratella quadrata (Müller, 1786), Eudiaptomus gracilis (Sars, 1863), and E. graciloides (Lilljeborg, 1888) were recorded in the zooplankton, that thrived throughout the summer and autumn. Typical brackish-water species were encountered, for example, Hemidiaptomus ignatovi Sars, 1903. A specific community of zooplankters was formed in different biotopes of the lake: Daphnia galeata and Bosmina (E.) cf longispina (Leydig, 1860) were found in the pelagial; Pleuroxus aduncus (Jurne, 1820) and Eucyclops macruroides (Lilljborg, 1901) in macrophyte beds. The species inhabiting the deep-water part of the water body may be considered as indicators of oligo- and mesotrophic waters (Diaphanasoma brachyurum (Lievin, 1848), Bosmina (Eubosmina) cf. longispina Ley dig, 1860, and Bilpalpus hudsoni (Imhof, 1891)). Two rotifer species Rotaria rotatoria (Pallas, 1766) and Lecane (s. Str.) luna (Müller, 1776) were found only in macrophyte beds indicating mesotrophic conditions. In June and September 2010, the abundance of zooplankton throughout the entire lake varied from 1200 to 196 (on average, 484.3 ± 166.4) thousand individuals/m³, and the biomass from 13.6 to 0.9 (on average, 8.5 ± 2.5) g/m³. Crustaceans (78%) have also made the main contribution to the formation of quantitative indicators of zooplankton in various biotopes of the lake.

Rotifer Species Diversity in Mexico: An Updated Checklist

A review of the Mexican rotifer species diversity is presented here. To date, 402 species of rotifers have been recorded from Mexico, besides a few infraspecific taxa such as subspecies and varieties. The rotifers from Mexico represent 27 families and 75 genera. Molecular analysis showed about 20 cryptic taxa from species complexes. The genera Lecane, Trichocerca, Brachionus, Lepadella, Cephalodella, Keratella, Ptygura, and Notommata accounted for more than 50% of all species recorded from the Mexican territory. The diversity of rotifers from the different states of Mexico was highly heterogeneous. Only five federal entities (the State of Mexico, Michoacán, Veracruz, Mexico City, Aguascalientes, and Quintana Roo) had more than 100 species. Extrapolation of rotifer species recorded from Mexico indicated the possible occurrence of more than 600 species in Mexican water bodies, hence more sampling effort is needed. In the current review, we also comment on the importance of seasonal sampling in enhancing the species richness and detecting exotic rotifer taxa in Mexico.

Assessment of zooplankton community in an anthropogenic-disturbance coastal creek, southwest Nigeria

In order to assess the zooplankton community in an anthropogenic-disturbance Badagry creek, Zooplankton and water samples were collected and analyzed bi-monthly from November 2011 to September 2013 in nine stations representing its three different zones using standard methods. Zooplankton was identified to species-level using relevant texts and counted under a Microstar IV Carl Zeiss binocular microscope calibrated at different magnifications. Diversity was determined using Shannon-Weiner (H), Simpson (1-D) and Evenness (e^H/S) indices. Water samples were analysed for temperature, pH, salinity, conductivity, turbidity, dissolved oxygen, water depth and nitrate. Data were analysed using descriptive statistics, ANOVA, cluster and Canonical correspondence analysis (CCA) at α = 0.05. A total of 56 species comprising 26 species of rotifers, 15 species of arthropoda, 4 species of ciliophora, 3 species of cnidaria, and 2 species of ctenophora, foraminifera, mollusca, protozoa each, with an array of meroplankton / juvenile stages of the order copepod of subphylum crustacea were recorded. Diversity indices were highest (H = 2.20; 1-D = 0.80; e^H/S = 0.27) at station 6 and lowest in station 8 (H = 1.20; 1-D = 0.56) and station 1(e^H/S = 0.14). Salinity/conductivity, nitrate and water depth were significantly different (p < 0.05) among the study stations. CCA revealed salinity/conductivity and nitrate were the most important abiotic factors co-related with the zooplankton abundance in Badagry creek. The moderately low zooplankton communities’ diversity and abundance in Badagry creek point at different natural and anthropogenic factor impacts.

Vaduvur and Sitheri lakes, Tamil Nadu, India: conservation and management perspective

Wetlands are declining globally. Hence, it is reasonable to assume that most existing wetlands are impacted to some degree by human land-use that in turn caused population declines in many wetland-dependent taxa. The National Wetland Atlas has classified Tamil Nadu as a wetland-rich state as they occupy 6.92% of geographic area. However, studies on wetlands are limited in Tamil Nadu. Hence, an attempt was made to identify the threats to the Vaduvur and Sitheri lakes and their associated fauna. In total, 118 species of birds belonging to 87 genera, 48 families and 18 orders in Vaduvur Lake and 87 species of birds belonging to 71 genera, 48 families and 16 orders in Sitheri Lake were recorded. A total of 28 zooplankton species were recorded in both the lakes comprising 14 species of rotifers, six species of cladocerans, five species of copepods, two species of ostracods, and one species of protozoa. A total of 15 species of fishes were identified from the sellers who catch fishes from the Sitheri Lake. The physico-chemical parameters of water varied according to the seasonal fluctuations in rainfall pattern. In general, wetland management for waterbirds of these two lakes should focus on providing suitable nesting habitats and available food resources for dependant avifauna. Management of invertebrates, amphibians, and fishes in these two lakes is one technique that can be used to provide foraging opportunities for waterbirds. An integrated approach and increased co-operation would result in the rational use of this freshwater resource leading to improved standards of living around this lake.

Intrinsic postzygotic barriers constrain cross‐fertilisation between two hybridising sibling rotifer species of the Brachionus calyciflorus species complex

Abstract Brachionus calyciflorus is a recently described monogonont rotifer species complex that comprises four species. The observation of hybridisation between two of these species challenges this species delimitation. The mechanisms of reproductive isolation essential to the maintenance of species integrity remain unclear. Here, we conducted upscaled hybridisation experiments to obtain large numbers of hybrid and non‐hybrid dormant propagules. Through hatching assays, we compared the zygote viability of hybrid with non‐hybrid dormant propagules. Furthermore, we investigated populations of F1 hybrid clones and assessed their clonal growth rate and the ability to reproduce sexually. Our results demonstrated higher rates of morphological abnormality and associated mortality in dormant propagules of hybrids compared to non‐hybrids yet hatching rates of healthy‐looking propagules proved similar. F1 hybrids exhibited high clonal population growth rates, nevertheless, we also observed strong differences between clones and a strong influence of parental genotype identity. Two‐thirds of the F1 hybrid clones showed a low incidence of sexual reproduction and almost never produced dormant propagules. Clones with high population growth rates seemed to invest less in sexual reproduction. Our results clearly demonstrate the existence of intrinsic postzygotic barriers caused by relatively high mortality of dormant propagules. Furthermore, the low ability of most hybrid clones to engage in sexual reproduction may reduce the long‐term fitness of hybrid clones. These postzygotic barriers probably impede genetic exchange between parental species and contribute to the maintenance of their integrity.

Zooplankton Community Structure in Shallow Saline Steppe Inland Waters

Several shallow saline waters can be found in Central Asia in arid steppe climate, but our knowledge of their zooplankton community has been so far rather limited. The aim of our research was to provide data on the steppe zooplankton community in a large-scale regional study. Therefore, a baseline survey was carried out in 23 shallow inland waters of different salinity in Northern Kazakhstan. We measured the quantity and identified the taxonomic composition of zooplankton in the spring period and examined changes in community structure in correlation with salinity. Lesser salt concentration of the hyposaline–mesosaline waters was indicated by the presence of halophilic rotifer species: Brachionus asplanchnoides, Br. dimidiatus, Br. plicatilis. Mesosaline and hypersaline waters were indicated by the presence of halobiont crustaceans: Moina salina, Arctodiaptomus salinus, Cletocamptus retrogressus. Very high concentration of salt was indicated by presence of Artemia alone which is the only group, that can tolerate and adapt to this extreme environment. In the hypersaline waterbodies at over 79 gL−1 high TDS conditions a very simple tropical structure was found. Artemia playing monopolistic ecological function in the zooplankton community. We identified three characteristic groups of shallow inland saline waters based on their zooplankton composition.

The Species Diversity of Tropical Freshwater Rotifers (Rotifera: Monogononta) in Relation to Environmental Factors

This study aims to evaluate the diversity of rotifers in various freshwater habitats in Da Nang City, Vietnam, and to investigate the relationship between community structure and environmental conditions. A total of 75 rotifer species belonging to 25 genera and 17 families were recorded, out of which seven species are new to Vietnam. Species from the families Brachionidae and Lecanidae are abundant (containing about 50% and 69.44%, respectively) in the total rotifer species in both lacustrine and riverine habitats. The number of rotifers recorded in the lakes (64 taxa) was much higher than those in rivers (36 taxa), and this is possibly due to the conditions in lakes being more favorable for the development of small zooplanktons. The significant influences of environmental factors (temperature, pH, turbidity, and trophic state) on the rotifer community were well-reflected in the distribution of commonly found species in lakes (p-value < 0.05). Our study results enrich the data on the diversity and the ecology of rotifers in Vietnam.

Divergent responses in morphology and life history to an Asplanchna kairomone between attached and free-swimming Brachionus dorcas (Rotifera)

In the presence of the predatory rotifer Asplanchna, some Brachionus and Keratella species develop inducible morphological, behavioral, and life history defenses that enable prey to survive predation pressure. However, whether clones belonging to the same rotifer species but with different behaviors (attached and free-swimming) exhibit divergent responses in morphology and life history remains largely unknown. In this study, neonates of an attached and a free-swimming clone of B. dorcas were exposed to media conditioned by A. brightwellii neonates at densities of 0 (control), 40, 80, and 160 ind l−1 for 24 h, and their morphological and life-table demographic parameters were measured and calculated. We showed that the Asplanchna kairomone significantly increased the propensity to attach in the attached clone only, with attached individuals effectively protected from Asplanchna predation. In response to increasing Asplanchna kairomone concentration, the attached clone did not show any morphological changes, but it did exhibit a decreased net reproductive rate and intrinsic rate of population increase. The free-swimming clone developed elongated posterolateral spines and a decreased intrinsic rate of population increase, as well as a decrease in the proportion of sexual offspring. Thus, both clones exhibited reproductive costs.

Diversity and Abundance of Zooplankton in River Aswa in Uganda

Zooplankton community constitutes one of the keystone organisms that are crucial in understanding aquatic ecosystem responses to environmental distresses. The objective of this study was to contribute to the understanding of zooplankton ecological conservation status and assessment of potential impacts of the proposed Hydropower plant on the zooplankton community in River Aswa, Nwoya District, in Uganda. Baseline information on aquatic micro-invertebrate diversity, abundance and distribution along the affected river section was generated. Two copepods and four species of rotifers were recorded. The Intake site had the highest diversity (six species) while Powerhouse hadfour species. Of the species encountered, Keratella tropica registered the highest abundance—1,025 and 732 individuals m-2 at the Powerhouse and Intake sites, respectively. Total zooplankton densities were comparable with Intake (2,773 individuals m-2) and Powerhouse (2,311 individuals m-2). The zooplankton taxa do not appear in the IUCN Red List in the Catalogue of Life. Therefore, the proposed construction of a hydropower plant may not pose zooplankton conservation problems.
 Keywords: Biodiversity, Zooplankton, invertebrates, hydropower, River Aswa.

Ultrastructure of extracorporeal secretions of four sessile species of Rotifera (Gnesiotrocha), with observations on the chemistry of the gelatinous tube

AbstractSecretion of an extracorporeal hydrogel is a common defensive strategy employed by many aquatic invertebrates including several species of sessile rotifers. Here, we provide a comparative study of the ultrastructure of the gelatinous secretions of four species of Superorder Gnesiotrocha (Monogononta): Conochilus unicornis, Collotheca ferox, Stephanoceros fimbriatus, and Stephanoceros millsii. Additionally, we use differential staining and enzyme degradation assays to explore the chemistry of the gelatinous tube of S. fimbriatus. At least three types of secretions are produced by these four species: an external gelatinous tube, a thick glycocalyx, and an adhesive peduncle. These three different secretions all have a fibrous appearance, but each has different electron densities, fiber thicknesses, and glandular origins. The gel tube, which is likely secreted by pedal glands, has a highly hydrated framework of mesh‐like fibers with thick internal and external laminae that differ slightly among species. Chemical staining suggests that the gel tube is composed of glycoproteins with a high content of sulfonic groups and limited or no obvious lipids or cationic proteins. This tube is resistant to chemical and enzymatic digestion. The proteinaceous glycocalyx is secreted by the syncytial integument and has various densities and thicknesses among species. The peduncle is an adhesive attachment that connects a rotifer's foot to a substratum, or, in some species, to conspecifics as part of a colony. The secretion is highly electron dense and contains membrane‐bound vesicles; it appears to be derived from a different set of pedal glands than the hydrogel tube. The different chemistries and anatomical origins of the three gelatinous secretions suggest an independent evolutionary history for each.

Evolutionary dynamics of transposable elements in bdelloid rotifers.

Transposable elements (TEs) are selfish genomic parasites whose ability to spread autonomously is facilitated by sexual reproduction in their hosts. If hosts become obligately asexual, TE frequencies and dynamics are predicted to change dramatically, but the long-term outcome is unclear. Here, we test current theory using whole-genome sequence data from eight species of bdelloid rotifers, a class of invertebrates in which males are thus far unknown. Contrary to expectations, we find a variety of active TEs in bdelloid genomes, at an overall frequency within the range seen in sexual species. We find no evidence that TEs are spread by cryptic recombination or restrained by unusual DNA repair mechanisms. Instead, we find that that TE content evolves relatively slowly in bdelloids and that gene families involved in RNAi-mediated TE suppression have undergone significant expansion, which might mitigate the deleterious effects of active TEs and compensate for the consequences of long-term asexuality.

First record for the Palearctic region of a rare rotifer from the Ptygura elsteri group (Rotifera: Monogononta: Flosculariaceae: Flosculariidae) with description and biogeography of a new species: Ptygura innominata n. sp.

Here, I describe a new rotifer species within the Ptygura elsteri group collected from Mallorca, Spain (Palearctic). Previously reported from the Nearctic, this form possesses anatomical and ecological characteristics that indicate it to be a separate species. While other morphotypes assigned to the P. elsteri group have cervical hooks, the hooks on this morphotype are clearly different. In this report, I discuss previously published observations of this form, describe its anatomical and ecological details, and discuss its taxonomic position within the genus Ptygura. The name for this new species is Ptygura innominata n. sp.

Species Composition Features of Zoopankton in Mineralized Water Bodies from Specially Protected Natural Territories in Ulug-Khem Basin (Republic of Tuva)

The species composition of zooplankton in mineralized water bodies located in the Ulug-Khem basin (Republic of Tuva) was studied. These lakes have the status of natural monuments of regional significance. In total we recorded 53 species of microscopic Custaceans and Rotifers from 32 genera, 13 families, and 8 orders. Cladocera comprises 53% of the species. The dependence of the species diversity on the level of mineralization was revealed; 89% of the species were found in brackish water bodies. The zooplankton composition of the hyperhaline lakes Dus-Khol (Svatikovo) and Cheder has remained constant for many dozen years. The zooplankton includes some species known only from Republic of Tuva in Russia, namely, Microcyclops afganicus and Macrotrix tabrizensis. M. asiaticus and Alona irinae, rare for the fauna of Russia, live in the lake Haak-Hol. A decrease in the total numbers of zooplankton is observed in the lakes, namely: in the lake Dus-Khol, it has decreased by 4 times, in the lake Khadyn it has decreased by 10–19 times as compared to the middle of the last century. Despite the lack of intermediate information, we regard this as a consequence of anthropogenic impact. The emergence of an indicator of pollution (Brachionus nilsoni) in the lake Khadin confirms this version. At the same time, the stable finding of species rare for the fauna of Russia indicates the presence of favorable conditions for their development and life, which increases the value of the reservoirs themselves, which are already unique natural objects.

Littoral zooplankton diversity in Himayat Sagar Reservoir, Telangana, India

AbstractThe present study investigated zooplankton composition and diversity, along with physicochemical parameters from the littoral regions of Himayat Sagar Reservoir, Telangana, India. A total of 84 zooplankton species were found, including 60 rotifer species, 16 cladoceran species and eight copepod species. Keratella tropica, Lecane bulla, Coronatella rectangula and Mesocyclops sp. were observed frequently throught the study period. The Shannon Diversity Index ranged between H′ = 1.8 and 2.1, with a high diversity observed during the summer season. Dominance was greater during the monsoon and winter seasons, being represented by Brachionus calyciflorus, B. angularis, B. falcatus, Keratella tropica, Ceriodaphnia cornuta, Diaphanosoma sarsi and Mesocyclops sp. Correlation coefficients and principal component analysis indicated temperature, pH and nutrients had a major influence on zooplankton community changes in this reservoir. The environmental variables and diversity indices indicated seasonally fluctuating trophic conditions. Himayat Sagar Reservoir requires long‐term monitoring for assessment and better management of its faunal diversity and water quality.

Rotifera in lake subhabitats

Lake ecosystems contain numerous habitats, such as the relatively homogeneous pelagial, as well as many different subhabitats in the littoral zone. Among rotifer communities inhabiting the littoral zone are those living in organic sediments (epipelon), on submerged stones (epilithon), among sand grains (hydropsammon), on animals (epizoon), on submerged branches and twigs (epixylon) and on macrophytes (epiphyton). The aim of this work was to explain differences in species richness among rotifer communities inhabiting these subhabitats. Qualitative and quantitative analyses of the structure and diversity of rotifer species were based on studies carried out in the summers of 2009–2020 in lakes in northeastern Poland. The analysis of the structure and density of rotifer species inhabiting different lake subhabitats suggests that although the communities are subject to similar ecological characteristics, there are marked differences in the species richness and diversity of the communities. A characteristic feature is the presence of species sharing subhabitats and species assigned to only one habitat type.

Checklist of rotifer species from Albania (phylum Rotifera)

The checklist of Rotifera species recorded for Albanian inland waters and its neighboring regions is provided. A total of 140 species of bdelloids and monogononts, with representatives of 38 genera are listed. The history of rotifer surveys as a component of zooplankton in Albania started at the end of 19th century. Mostly they were taxonomic and descriptive ones, while later on after the mid 20th century appeared the systematic approaches emphasizing the particularities and richness of zooplankton in specific karstic Mediterranean ecosystems. In this article 140 taxa of bdelloids and monogononts representing 39 genera are reported.

The composition and heterogeneity of the rich and diverse rotifers (Rotifera: Eurotatoria) of the floodplain lakes (beels) of the Majuli River Island, Assam State (Northeast India)

The tropical and subtropical floodplain lakes are hypothesized as one of the globally interesting rotifer rich ecosystems. Our study indicating the biodiverse Rotifera of ten ‘slightly acidic to circum-neutral, moderately hard-water and de-mineralized’ tropical floodplain lakes (beels) of the Majuli River Island of the Brahmaputra river basin of northeast India mendorses this hypothesis. Total richness, the richness of important families and community similarities affirm heterogeneity mof the rotifer species composition amongst the beels. The species richness registers significant spatio-temporal variations with seasonal differences amongst the beels and individually in each beel, and lacks significant influence of the recorded abiotic factors. The constellations of 76-81 species in three beels during winter and 76 species in one beel during pre-monsoon are noteworthy instances of ‘Rotifera paradox’. The rotifer fauna of the Majuli beels registers affinity with Southeast Asian and Oriental faunas, records several species of the regional distribution interest and exhibits the littoral-periphytic nature, while application of Q B/T and Q L/B quotients depicts limitations. This study merits ecological diversity interest for Rotifera vis-avis the floodplain lakes of India and elsewhere from the tropics and subtropics, and assumes biodiversity conservation importance due to threat of extinction of the Majuli – an alluvial floodplain of the Brahmaputra basin.

COMPOSICIÓN DE LA DIETA DE Asplanchna girodi (PLOIMA, ASPLANCHNIDAE) EN UN EMBALSE ALTOANDINO ECUATORIAL EN COLOMBIA BASADO EN OBSERVACIONES DE CAMPO

Asplanchna girodi (de Guerne, 1888) is a predatory rotifer of wide distribution in temperate and tropical freshwater ecosystems. Of this species, little is known about its diet and its food preferences under natural conditions, since most of the work related to this aspect has been carried out under laboratory conditions. During a short monitoring program at La García Reservoir, a high Andean equatorial reservoir located in the central region of the department of Antioquia (Colombia), in which this species reached a total density of 2.296,2 ind.L-1, studied the composition of the A. girodi diet based only on the direct observation, under the microscope, of the organisms contained in the stomachs of all the individuals present in the simples. Between June and September 2014, integrated samples composed of five depths were taken monthly at three monitoring stations in the entire water column, with a sampling bottle of 10 L capacity. The collected material was filtered through a 30µm plankton net of mesh eye. It was found that A. girodi, presented a wide trophic preference that included the foraging of a dinoflagellate (Ceratium, Schrank), five species of rotifers and a cladoceran. These results lead to the conclusion that A. girodi is possibly an opportunistic species, since consumption is directed at the species with the highest availability (in this case Ceratium) and with the greatest energy savings, since no investment is made in the search for specific prey and in turn would become an important factor in controlling phytoplankton populations.

STUDY ON ZOOPLANKTON DIVERSITY DURING SPRING SEASON IN CHASHMA LAKE, PAKISTAN

The present study was conducted to know the zooplankton species diversity in Chashma Lake during spring (March 2016 to May 2016). Various physico-chemical parameters like Temperature, PH, Salinity, conductivity, Total dissolved solids (TDS), Turbidity, Dissolved Oxygen, Alkalinity, Chloride and Carbon dioxide which effect the distribution of zooplankton were also analyzed during this study. Zooplankton community was dominated by different species of rotifers. Those rotifers were Asplanchna herricki, Asplanchna brightwelli, Polyarthra remata, Brachionus angularis, Keratella cochlearis, Keratella tecta and Keratella valga tropica. Among these Keratella valga tropica was most common. Some species of copepods were recorded such as, Diacyclops thomasi, Acanthocyclops robustus, Mesocyclops edax, Tropocyclops prasinus mexicanus and Orthocyclops modestus. Among these Diacyclops thomasi was most abundant. Among copepods some nauplii and copepodid stages were also observed. Different species of cladocerans such as, Bosmina longirostris, Daphnia pulex, Chydorus sphaericus, Alona bicolor, Alonella exigua and Simocephalus serrulatus were also recorded.