Key to sessile gnesiotrochan rotifers: Families, monospecific species in Flosculariidae, species of Atrochidae, Conochilidae, and Limnias

Abstract

Accurate identification of species is key to understanding their ecological roles and evolutionary history. It is also essential in cataloging biodiversity for comparisons among habitat types, responses to climate change, effective management practices, and more. The paucity of taxonomic expertise is increasing and with it the ability to competently identify species, this is particularly true for small taxa including rotifers. In an effort to improve this situation, we collated information on morphological characters from the literature on all valid species of sessile Gnesiotrocha (phylum Rotifera) currently assigned to two orders and four families. We review Order Collothecaceae, which comprises families Atrochidae (3 spp.) and Collothecidae (50 spp.) and Order Flosculariaceae, which includes families Conochilidae (7 spp.) and Flosculariidae (71 species). Based on that information, we provide dichotomous keys to the Families, monospecific species in Flosculariidae, and species of Atrochidae, Conochilidae, and Limnias. These keys will aid researchers to identify species in these families and lead to a better understanding of freshwater biodiversity and eco-evolutionary processes.

Key to sessile gnesiotrochan rotifers: Floscularia (Monogononta; Flosculariidae)

“…It is also important that these gaps be filled to develop complete phylogenies (Sørensen & Giribet 2006). Here we continue our focus on the sessile species in phylum Rotifera (sensu stricto) begun by Davies et al (2024), a group whose study is hindered by the lack of new taxonomists armed with up to date keys (Ejsmont-Karabin 2019;Fontaneto et al 2012).…”

“…Although usually less than 1000 µm in size and numbering only about 2000 described species, rotifers have piqued the curiosity of researchers for >200 years. (Davies et al 2024;Edmondson 1959;Fontaneto & De Smet 2015;Wallace et al 2006). This interest stems from the fact that these short-lived, aquatic metazoans possess diverse morphologies and varied life cycles (Wallace et al 2015), as well as reproductive modalities encompassing both obligatorily sexual, obligatorily asexual, and cyclically parthenogenetic (Serra et al 2018).…”

“…Identification of sessile rotifers is based on relatively simple characters, including shape of the corona, presence of sensory and other morphological structures in the apical field, body size, propensity to form colonies, and the fact that many species form extracorporeal coverings that surround their bodies (Yang & Hochberg 2018a, 2018bYang et al 2021). Indeed, because these coverings vary in their construction to include gelatinous matrices, flexible, hardened tubes, and pipe-like tubes composed of pellets, their composition is a convenient characteristic on which keys to the genera and even species may be based (Davies et al 2024;Edmondson 1959;Koste 1978). Unfortunately, of all potential features, morphology of their trophi has been nearly neglected.…”

“…Identify of sessile rotifers to the level of genus and then species can be difficult. The monospecific species in Flosculariidae (Beauchampia, Lacinularoides, Octotrocha, and Pentatrocha), species of Conochilidae, and Limnias have been recently considered by Davies et al (2024). A few straightforward features allow differentiation of the remaining genera of Flosculariidae: Floscularia, Lacinularia, Ptygura, and Sinantherina.…”