An extraordinary new fluvial bdelloid rotifer, Coronistomus impossibilis gen. nov., sp. nov., with adaptations for turbulent flow (Rotifera: Bdelloidea: Coronistomidae fam. nov.)

A new bdelloid rotifer, Coronistomus impossibilis gen. nov., sp. nov. is described from the Hawlings River in Maryland, USA. The new species is a non-swimming sediment dweller that exceeds 550 µm in body length. Its corona is a weakly bilobed ciliated field on the ventral side of the head with lateral borders continuing into mouth. The species has ramate trophi that have on each half three widely spaced major teeth with two interproximal teeth. The foot lacks spurs and ends with a pair of long, thick ventral toes and a medially positioned caudal appendage. The new species lives in microhabitats exposed to turbulent flow and its morphological idiosyncrasies are interpreted as adaptations to reduce the likelihood of getting dislodged by the water. Although the corona morphology and the caudal appendage of the new species are similar to the corresponding traits of some of the species in the family Philodinavidae, the structure of its nonprotrusible trophi and its possession of only two toes (as opposed to four) separate it from all other members of the Philodinavidae. Therefore, a new family, Coronistomidae fam. nov., is erected for the new genus Coronistomus.

The trouble with Adineta vaga (Davis, 1873): a common rotifer that cannot be identified (Rotifera: Bdelloidea: Adinetidae)

My purpose here is to highlight three long-standing problems in the taxonomy of Adineta vaga (Davis, 1873) and its subspecies: 1. The lack of unique morphological criteria to identify the morphological variant (morphovariant) Davis described; 2. The lack of an evolutionarily meaningful subspecies definition applicable to parthenogenetic bdelloid rotifers; 3. The lack of compliance with the applicable articles of the International Code of Zoological Nomenclature (ICZN; https://tinyurl.com/y8f242an) when subspecies are assigned to A. vaga.

Bdelloid rotifers (Rotifera, Bdelloidea) of China: diversity and new records

Bdelloid rotifers are a group of microscopic invertebrates known for their obligate parthenogenesis and exceptional resistance to extreme environments. Their diversity and distributions are poorly studied in Asia, especially in China. In order to better understand the species distribution and diversity of bdelloid rotifers in China, a scientific surveys of habitats was conducted with 61 samples (both terrestrial and aquatic habitats) from 11 provinces and regions of China, ranging from tropics to subtropics with a specific focus on poorly sampled areas (Oriental) during September 2017 to October 2018. A total of 59 morphospecies (including subspecies) were found, of which, thirty-nine morphospecies (including one genus) are new records for China, almost doubling the number of previous records. Four rare morphospecies (Adineta cf. acuticornis Haigh, A. beysunae Örstan, Habrotrocha ligula loxoglotta De Koning and H. serpens Donner) are depicted and redescribed, and an updated checklist of Chinese bdelloids with their location and ecological information is presented. This study provides new data from a large region of China, enriching the knowledge of bdelloid biodiversity, and their global biogeography.

Descriptions of two new species of Philodina (Rotifera, Bdelloidea), with notes on seven rare bdelloids from Korea

A taxonomic study on bdelloid rotifers collected from various terrestrial habitats at five different locations in Korea resulted in eight new Korean records and two new species-level taxa, Philodina clypeata n. sp. and P. verrucosa n. sp. Among the eight new Korean records, two species- and three subspecies-level taxa are new to Asia as well. These new Korean records also include seven rare species/subspecies-level taxa with poorly known distributions. Habrotrocha gracilis quadridens Schulte and Macrotrachela zickendrahti seda Donner were rediscovered in Korea 64 and 53 years, respectively, after the original descriptions. Habrotrocha ligula aligula Burger, Macrotrachela insulana Donner, M. petulans Milne, M. pinnigera (Murray), and Philodina parvicalcar De Koning have been reported from two to three countries only including their type localities before the present study. In addition, a partial sequence of mitochondrial cytochrome c oxidase subunit I gene (mtCOX1) for P. verrucosa n. sp. as well as a taxonomic key for the Philodina species recorded from Korea to date are also provided here.

Taxonomic morphology of the genus Adineta (Rotifera: Bdelloidea: Adinetidae) with a new species from a suburban garden

The morphological descriptions of the species of bdelloid rotifers and the associated taxonomic difficulties, primarily resulting from the inadequate original descriptions of many species, are discussed. The genus Adineta, whose members are relatively easy to study and frequently encountered, is proposed as a starting point for taxonomic revisions of the Bdelloidea. The taxonomically significant morphological traits in the genus Adineta are discussed. Some of these have rarely been used: the number of denticles on the rake organ and body proportions. These traits are used to describe Adineta beysunae sp. nov., which was found in a sample from a house garden. The new species is diagnosed by the morphology of its rump, foot and rake organ. The latter has up to 11 denticles, the highest number recorded in an Adineta species.