Three New Freshwater Cochliopodium Species (Himatismenida, Amoebozoa) from the Southeastern United States

Abstract

Cochliopodium is a lens‐shaped genus of Amoebozoa characterized by a flexible layer of microscopic dorsal scales. Recent taxonomic and molecular studies reported cryptic diversity in this group and suggested that the often‐used scale morphology is not a reliable character for species delineation in the genus. Here, we described three freshwater Cochliopodium spp. from the southeastern United States based on morphological, immunocytochemistry (ICC), and molecular data. A maximum‐likelihood phylogenetic analysis and pairwise comparison of COI sequences of Cochliopodium species showed that each of these monoclonal cultures were genetically distinct from each other and any described species with molecular data. Two of the new isolates, “crystal UK‐YT2” (Cochliopodium crystalli n. sp.) and “crystal‐like UK‐YT3” (C. jaguari n. sp.), formed a clade with C. larifeili, which all share a prominent microtubule organizing center (MTOC) and have cubical‐shaped crystals. The “Marrs Spring UK‐YT4” isolate, C. marrii n. sp., was 100% identical to “Cochliopodium sp. SG‐2014 .” These sequences formed a clade with C. actinophorum and C. arabianum. While the new isolates can be separated morphologically, most of the taxonomic features used in the group show plasticity; therefore, Cochliopodium species can only be reliably identified with the help of molecular data.

Grazing preferences of three species of amoebae on cyanobacteria and green algae

“…One of the two larger amoebae was morphologically identified as Cochliopodium sp., which is in the order Himatismenida, phylum Discosea. Cochliopodium was observed to have intracellular crystalline cytoplasmic inclusions and extracellular scales (Figure 1A,B) (Geisen et al., 2014; Melton et al., 2020), and to produce cysts (Figure 1B) (Anderson & Tekle, 2013).…”

Differential gene expression analysis and cytological evidence reveal a sexual stage of an amoeba with multiparental cellular and nuclear fusion

“…These problems make it difficult in identifying unfused or fused cells based on size and number of nuclei. Given these challenges, we made an effort to select cells based on our observation in previous publications [ 21 – 23 ] as a general guide to discriminate between unfused (~20–30 μm) and fused (> 50 μm) amoeba cells.…”

“…Cochliopodium species grow as single cells with a single nucleus through most of their life cycle. However, in sufficiently dense cultures, they fuse forming larger plasmodial stages, their nuclei migrate within the plasmodium, come into contact and fuse, forming polyploid nuclei [ 16 , 22 , 23 ]. Subsequently, the merged nuclei undergo division within the plasmodium presumably resulting in a new mix of chromosomes.…”

“…We recently described the life cycle of a lens-shaped amoeba (Cochliopodium minus) that undergoes extensive multiple cellular and nuclear fusion during active growth (i.e. the vegetative stage) [16,21], hereafter referred to as Cochliopodium for brevity and since most of the members of the genus display similar behavior [22][23][24]. Cochliopodium possesses genes exclusively involved in meiosis [11,13].…”