Species diversity of rotifers (rotifera: monogononta) in freshwater psammon with three new records to Vietnam

This study aims to evaluate the diversity of rotifers in psammon in the Central Coast of Vietnam. A total of 64 rotifer species belonging to 17 genera and 14 families were recorded in 10 samples collected at hygropsammon zones of freshwater lakes and ponds in Thua Thien Hue province. Lepadella cristata (Rousselet, 1893), Cephalodella tenuior (Gosse, 1886), and Lindia torulosa Dujardin, 1841 were new record to Vietnam rotifers fauna. Species from the families Lecanidae, Lepadellidae, and Trichocercidae are abundant (containing about 44%, 14%, and 12%, respectively) in the total rotifer species recorded. Psammonxenic species accounted for the largest percentage of the psammic rotifer community with 83%, followed by psammonphiles (11%) and psammonbionts (6%). Our study results enrich the data on the diversity and the ecology of rotifers in Vietnam.

Variable Fitness Response of Two Rotifer Species Exposed to Microplastics Particles: The Role of Food Quantity and Quality

Plastic pollution is an increasing environmental problem, but a comprehensive understanding of its effect in the environment is still missing. The wide variety of size, shape, and polymer composition of plastics impedes an adequate risk assessment. We investigated the effect of differently sized polystyrene beads (1-, 3-, 6-µm; PS) and polyamide fragments (5–25 µm, PA) and non-plastics items such as silica beads (3-µm, SiO2) on the population growth, reproduction (egg ratio), and survival of two common aquatic micro invertebrates: the rotifer species Brachionus calyciflorus and Brachionus fernandoi. The MPs were combined with food quantity, limiting and saturating food concentration, and with food of different quality. We found variable fitness responses with a significant effect of 3-µm PS on the population growth rate in both rotifer species with respect to food quantity. An interaction between the food quality and the MPs treatments was found in the reproduction of B. calyciflorus. PA and SiO2 beads had no effect on fitness response. This study provides further evidence of the indirect effect of MPs in planktonic rotifers and the importance of testing different environmental conditions that could influence the effect of MPs.

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.

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.

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.

Functional groups of rotifers and an exotic species in a tropical shallow lake

In freshwater environments the rotifer group may be divided into microphagous and raptorial species regarding their feeding patterns, and such guilds differently interact with other community components. Here, we analyzed the influence of cladocerans, cyclopoid nauplii, temperature, food resources and an exotic species on rotifer guilds, based on weekly samplings for 1 year. We have identified rotifer species and their trophi types in order to separate them into the raptorial and microphagous functional groups. The ratio raptorial:microphagous rotifers (Guild ratio, GR) was used in interaction analyses with cladocerans, nauplii, temperature, food resources and the exotic species Kellicottia bostoniensis. Correlations between total rotifers and food (phytoplankton carbon) and temperature were negative and significant, therefore, these factors did not lead to the increase of rotifer community. On the other hand, microphagous rotifers had opposing relation to cladoceran densities, as GR values showed that they became predominant when cladoceran populations declined. The use of density-based GR was adequate, with similar results compared to biomass-based studies regarding interactions with other organisms. Furthermore, we have found no invasive characteristics for the exotic microphagous rotifer, Kellicottia bostoniensis, and it seems to be outcompeted by the native microphagous species.

Pretreatment Method for DNA Barcoding to Analyze Gut Contents of Rotifers

We designed an experiment to analyze the gut content of Rotifera based on DNA barcoding and tested it on Asplanchna sp. in order to ensure that the DNA extracted from the rotifer species is from the food sources within the gut. We selected ethanol fixation (60%) to minimize the inflow effects of treated chemicals, and commercial bleach (the final concentration of 2.5%, for 210 s) to eliminate the extracellular DNA without damage to the lorica. Rotifers have different lorica structures and thicknesses. Therefore, we chose a pretreatment method based on Asplanchna sp., which is known to have weak durability. When we used the determined method on a reservoir water sample, we confirmed that the DNA fragments of Chlorophyceae, Diatomea, Cyanobacteria, and Ciliophora were removed. Given this result, Diatomea and cyanobacteria, detected from Asplanchna, can be considered as gut contents. However, bacteria were not removed by bleach, thus there was still insufficient information. Since the results of applying commercial bleach to rotifer species confirmed that pretreatment worked effectively for some species of rotifers food sources, in further studies, it is believed to be applicable to the gut contents analysis of more diverse rotifers species and better DNA analysis techniques by supplementing more rigorous limitations.

A new rotifer species: Lecane langsenensis n. sp. (Rotifera: Monogononta) from Vietnam

Lecane langsenensis n. sp. is described from two locations in Vietnam: Lang Sen Reserve, Long An Province, and the Huong River, Thua Thien Hue Province. It is distinguished from L. arcula, L. aculeata and L. superaculeata by its longer lorica, antero-lateral spine, and claws. Moreover, the size and shape of L. langsenensis, L. arcula, L. aculeata, and L. superaculeata were measured and compared. The results showed that these species are completely different.