Clevelandella elongata (Kidder, 1937)

(Figs 25–27; Supporting Information, Table S34)

Clevelandella elongata was detected and morphologically characterized in one population (SRU). When present, C. elongata was moderately abundant (20–30 cells per host) with the other ciliate species being more abundant.

Description based on SRU population:

Largest member of Clevelandellidae (on average 285 × 54 µm in vivo, range 245–321 × 43–71 µm; on average 220 × 61 µm in protargol preparations, range 184–259 × 43–75 µm). Elongated, almost vermiform in vivo, slightly dorsoventrally flattened, anterior end bluntly pointed, posterior end truncate and slightly flared, ventral margin convex, dorsal margin concave (Figs 25C, 27C). Cells shrink asymmetrically in protargol preparations (see Supporting Information, Table S50) and long axis straightens compared with more sinuous living specimens. Peristomial projection merges gradually with body proper hampering precise length measurement but, on average 20% of cell length (range 14–23%). Macronucleus broadly lenticular, situated slightly obliquely in anterior half of cell, large relative to cell (on average 51 × 24 µm), karyophore at anterior and posterior ends of macronucleus, usually distinct in vivo and in protargol preparations but sometimes indiscernible. Micronucleus large, globular (on average 7 µm diameter), adjacent to anterior end of macronucleus. Somatic cilia arranged in very closely spaced kineties, somatic cilia limited to approximately anterior 50% of cell, usually a short ‘tail’ of ciliated cortex extends posteriorly (Fig. 27A, B, D). Right sutural kinetofragments absent. Circumperistomial kineties very densely ciliated (Fig. 27A, B, D, E). Adoral zone extends about 45% of cell length on average, composed of an average of 94 membranelles (range 75–120). POM diplostichomonad only in anterior quarter (Fig. 26A, E).

(white arrow), and the posterior extent of ciliation on the right margin (black arrowhead). G, H, the same cell in ventral view, with detail of peristomial overture (black arrowhead). I, detail view of the long file (black arrowhead) and short file (white arrowhead) of the paroral membrane. J, ventral view (optical section) showing excretory antrum within left protuberance (black arrow). K, ventral view showing micronucleus (white arrow) and karyophore (black arrowhead). L, ventral view (optical section) showing micronucleus and adoral membranelles (black arrow). M, ventral view (optical section) showing anterior margin of the peristomial overture (black arrowhead). N, ventral view showing relatively large micronucleus (white arrow). O, detail of same cell as (N) showing micronucleus (white arrowhead) and karyophore (black arrowhead). P, ventral view showing micronucleus (white arrow). Q, ventral view showing micronucleus (white arrow). R, dorsal view of same cell as (Q) showing straight dorsal kineties (asterisk). S, detail of karyophore (white arrowhead). T, detail view of the long file (white arrowhead) and short file (black arrowhead) of the paroral membrane. Ma, macronucleus. Scale bars: 20 µm (A–H, J–N, P–R), 10 µm (I, O, S, T).

Remarks: Individuals of our population were longer and distinctly more slender in vivo than indicated by Kidder’s diagnosis for the species. Kidder (1937) did not specify whether his diagnosis for C. elongata was based on measurements from in vivo observations or fixed material, although the latter possibility seems most plausible given the technology available at that time.