Large pro rotifer (Proales amplus), new monogonont with large epipharynx from Korea (Rotifera, Proalidae)

NEWS - Large pro rotifer (Proales amplus) is the 42nd species in the genus Proales that exhibits unique morphological characteristics on the trophy, especially the unmatched epipharynx that prevents misidentification with other species. The epithet amplus is derived from the Latin word meaning large or wide, referring to the size and shape of the epipharynx.

Proalidae Harring & Myers 1924 includes 4 genera and 53 species that are distributed throughout the biogeography and inhabit a variety of environments, including freshwater, saltwater and terrestrial environments. The genus Proales includes 41 species that are characterized by various morphological features.

In Korea, the presence of Proalidae has been documented with 5 species: Bryceella perpusilla (Wilts, Martínez Arbizu & Ahlrichs, 2010), B. stylata (Milne, 1886), B. tenella (Bryce, 1897), Proales fallaciosa (Wulfert, 1937) and Proalinopsis caudatus (Collins, 1872).

The habitus of P. amplus has some similarities with P. phaeopis (Myers 1933), such as an elongated and fusiform body, two eyespots, one pseudosegment of the leg, two short toes and no dorsal papillae between the toes. However, the epipharynx of both species is very different.

Body slender, fusiform. Head is distinguished from the trunk by transverse folds. Two small red eyespots in the brain are positioned very close together shifted to the right. Trunk with six transverse folds, several longitudinal folds in the middle of the back.

Legs short, with one pseudosegment. Toes short, slender, ending in blunt tips. Pedal glands large, exceeding the length of the legs. Gastric glands very large, elongated, pyriform. Malleate trophies. Rami without alulae, with a pair of blunt projections located proximally.

Fulcrum short, thin, rod-shaped in dorso-ventral view. Keys with five teeth, consisting of three large and two small teeth. Preuncinal teeth on the largest key teeth. Manubria club-shaped, slightly curved, posterior ends curved dorsally.

Epipharynx large, wide, flat, with a comb-like shape at the apical edge; posterior base with a width of 1/3 of the anterior edge, extending to the middle of the ventral side of the rami; proximal anterior side of the right epipharynx extending to the left.

Molecular analysis shows significant genetic distance from other species and sufficient to be considered a distinct species. Furthermore, in the phylogenetic tree, this species forms a clade with other species in the Proalidae supporting its genetic allocation in the genus Proales.

However, Proales does not form a monophyletic group and shows a tendency for long branches. Researchers believe this is due to the lack of genetic information in Proalidae. This family has 53 species, but molecular data are only available for 1 Bryceella species, 5 Proales species and 1 Wulfertia species.

The limited molecular data, especially considering the taxonomic complexity of the genus Proales, highlights the critical need for more comprehensive taxonomic studies. This genus is known to be a complex group, so molecular data are essential in solving complex taxonomic challenges.

Original research

Yang H-M, Min G-S (2024). Proales amplus sp. nov., a new monogonont rotifer with a large epipharynx from Korea (Rotifera, Proalidae). Biodiversity Data Journal 12: e129622, DOI:10.3897/BDJ.12.e129622

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