Type species: Trichodina koloti sp. nov.

Type locality and type host: Sclerophrys gutteralis (Power, 1923), Nxamasere Floodplain, Okavango panhandle, Botswana (S 18° 35, 770’ E 22° 01, 551’)

Additional locality and host: Sclerophrys powerii (Hewitt, 1926), Nxamasere Floodplain, Okavango panhandle, Botswana (S 18° 34, 984’ E 22° 00, 035’)

Type-specimens: Holotype, slide 2016/12/15-01 and paratype, slides 2015/07/09-01 and 2015/07/12-09

18S nucleotide accession number: MT214940

Etymology: koloti (noun); [Tswana, a language spoken in southern Africa and the Okavango Delta region] – meaning tadpole

Morphology and morphometrics

Adult trichodinid specimens collected from tadpoles had a C-shaped macronucleus with a mean external diameter of 31.1–57.4 µm (47.0±9.5), thickness of 4.5–11.3 µm (7.2±2.5) and length of sector between terminations of macronucleus 3.8–38.5 µm (21.1±13.7) with no micronucleus were observed (Fig. 2). The adoral spiral followed a course of 370°–405°, which falls within the variation for the genus Trichodina. Based on the comparative morphological dimensions of all six populations, with only the minimum and maximum values given, the trichodinids had a convex body diameter ranging from 43.5–62.6 µm; adhesive disc diameter between 37.3–51.2 µm with a poorly to welldeveloped border membrane with a width of 2.7–5.7 µm (Table 5). The denticle ring diameter is between 21.3–35.3 µm, consisting of 20–28 denticles and 8–13 radial pins per denticle. The denticle blades are strong, semi-circular with a prominent apophysis on the anterior side with a length from 4.3–7.1 µm, tapering off towards a pointing tip. The ray of the denticle is strong, generally straight and tapers off towards the tip, it has a length ranging from 4.5–7.4 µm. The central part width is from 1.2–2.7 µm and the total denticle span is between 5.9–16.0 µm. There is little to no biometric variation between trichodinids collected from the different pools and anuran hosts, also not for seasonality (Figs 3–9).

By analysing the denticle dimensions for the Botswanan tadpole ecto trichodinids, according to the van As and Basson (1989) method (Figs 10a–f): The blade region was the most constant with minor differences between the specimens examined. Almost all had large, broad blades filling a large part of the section between the y and y+1 axes with the tangent point being slightly more proximal than the distal blade margin. The distal blade margin (surface) was generally curved, gradually sloping towards the proximal direction and parallel to the border membrane. Most of the posterior blade margins (surface) were smoothly curved in a shallow L-shape, with a few exceptions that were more deeply curved. In all the specimens the deepest point of the curve was more proximal than the apex of the blade, although some were almost on the same plain. The apexes of the blades were generally rounded, with some being slightly more pointed, and most of them extended past the y+1 axis. The anterior blade apophysis had slightly varying degrees of prominence, with the majority of specimens being somewhat prominent. No posterior projections on any specimens were observed. The central parts were slender and elongated. The distal surface was smaller, sloping more than the proximal. For the majority of the specimens the central part extended halfway past or more than halfway to the y axes. The form of the ray was mostly delicate.Almost all rays were of straight and equal width for the whole length, ending in a blunt tip. The majority of rays touched or ran parallel to the y–1 axis, in some specimens (Figs 10a, b) the rays were angled in a posterior direction, extending past the y–1. In most cases a delicate ray apophysis was present and in some specimens the ray apophyses were slightly more prominent (Figs 10b, c). The ray connections of the examined specimens were either marginally narrower than the width of the rest of the ray or of equal thickness of the ray. The ratio of the denticle above and below the x axis fell in a range between 0.5 and a maximum of 0.74, with most of the ranges clustering around 0.54.

Remarks. All tadpole trichodinid populations presented by Arthur and Lom (1984), Kruger et al. (1993a), Dias et al. (2009), Pala et al. (2018) and the populations from the current study show similarities in the biometrical data (Tables 4 and 5) and denticle shape (Figs 10 and 11). All of the above-mentioned populations represent the same species and based on the comparative similarities the denticle plan of this typical tadpole trichodinid is as follows:

Rays are always delicate and of equal thickness throughout the length of the ray.

Ray connections are thin, of the same thickness or slightly narrower than the rest of the ray.

Rays all terminate in rounded points.

The y axes’ relationship to the rays vary from touching the complete proximal side of the ray (Figs 11c, d, f) to running parallel, but not touching the ray (Figs 10 c, e, f; 11a, b, e). Variation noted in some individuals of the Botswana population includes rays angled posteriorly where some cross the y axes (Figs 10a,b) and angled anteriorly where some touch the y axes (Fig. 10e). However in all cases, the ray connection and base of the ray never cross the y axes posteriorly.

The central parts of all these trichodinid populations are narrow, elongated and of equal width throughout.

The base of the central part is of the same width as the central part for all populations. Posterior projections are observed in the population described by Pala et al. (2018) (Figs 11e, f), however, the above mentioned characteristics for the central part still apply.

The posterior termination of the central part is distinctly rounded.

In the majority of cases, bar the population of Kruger et al. (1993a) (Fig. 11c) the central part leans in a proximal direction.

In contrast, the typical denticle plan for T. hypsilepis from fish hosts is as follows:

Rays are always robust and never of equal thickness throughout the length of the ray (Figs 12a–f).

Ray connections vary from broad, narrowing after the connection (Figs 12a, c, f) and ray connection is well developed, but still narrower than the base of the ray (Figs 12b, e). Both of these characteristics can sometimes be observed in the same individual, but in different denticles (Fig. 12d).

Rays all narrow perceptibly along their length ending in a narrow/sharp point.

The y axes’ relationship to the rays vary from touching the complete proximal side of the ray (Figs 12b, c, f), running parallel, but not touching the ray (Figs 12a, d); to running though the midsection of the ray (Fig. 12e). Again, these characteristics can vary in different denticles of the same individual (Figs 12d, e, f).

The central parts of all T. hypsilepis populations are squat, varying in shape.

The base of the central part is always significantly wider than the central part proper.

The central part in the majority of cases is triangular.

In the majority of cases, bar the population of Pala et al. (2018) (Fig. 12e) the central part exhibits no slant.