Astylosternus diadematus Werner, 1898

Griesbaum, Frederic, Hirschfeld, Mareike, F. Barej, Michael, Schmitz, Andreas, Rohrmoser, Mariam, Dahmen, Matthias, Muehlberger, Fabian, Christoph Liedtke, H., L. Gonwouo, Nono, Doumbia, Joseph & Roedel, Mark-Oliver, 2019, Tadpoles of three western African frog genera: Astylosternus Werner, 1898, Nyctibates Boulenger, 1904, and Scotobleps Boulenger, 1900 (Amphibia, Anura, Arthroleptidae), Zoosystematics and Evolution 95 (1), pp. 133-160 : 136-137

Astylosternus diadematus Werner, 1898

Material examined.

ZMB 82799 (GenBank MK318845), 1 tadpole, Gosner stage 25, Cameroon, Mt Manengouba, Nkikok, 1328 m, 5°5'34.5"N, 9°49'3.8"E, 8 September 2011, leg. M. Hirschfeld; ZMB 82870 (GenBank MK318846), 1 tadpole, Gosner stage 25, Cameroon, Mt Manengouba, M’Bourouko, 1459 m, 5°4'3.48"N, 9°51'56.22"E, 1 December 2010, leg. M. Hirschfeld; ZMB 88345, 1 tadpole, Gosner stage 25, Cameroon, near Korup National Park, Mokango, 621 m, 5°8'11.29"N, 9°4'37.43"E, 9 May 2014, leg. F. Mühlberger; ZMB 88346, 1 tadpole, Gosner stage 36, Cameroon, near Korup National Park, Mokango, 502 m, 5°7'36.51"N, 9°4'9.49"E, 10 May 2014, leg. F. Mühlberger.

The two specimens from Mount Manengouba were caught in medium-sized streams in gallery forest; the Korup specimens were from small creeks in rainforest. The description is mainly based on ZMB 82799 and ZMB 88346. Genotyped tadpoles have been compared with two adults from Mount Nlonako, Cameroon (ZFMK 81585 and ZFMK 81702; GenBank MK318847, MK318848). The uncorrected pairwise p-difference between the tadpoles and between the tadpoles and the adults ranged from 0.2-0.7% (1-3 bp).

Description.

Long robust tadpole with muscular tail (Fig. 3); body oval in dorsal and lateral view; snout rounded in dorsal view, slightly more pointed in lateral view; body length approximately 0.3 (32.8-32.9%, N = 2) of total length; body height 46.7 ± 4.5% of body length; body width 60.7 ± 7.8% of body length; eyes positioned dorsolaterally, eye diameter 11.5 ± 1.0% of body length; nostrils positioned dorsolaterally, closer to snout tip than to eyes; inter-nostril distance 70.9 ± 3.5% of interorbital distance; tail fins narrow, dorsal and ventral fin originating from tail base, ventral fin height 67.7 ± 3.2% smaller than dorsal fin height; highest part of tail axis approximately in the middle of the tail; body height 82.2-85.7% (N = 2) of maximum tail height; tail axis width 47.4 ± 4.8% of body width; tail axis height 69.8 ± 5.4% of maximum tail height; tail tip pointed; vent tube dextral; body with large lateral sacs, extending from spiracle to end of body; short spiracle, sinistral; mouth ventral, very close to snout, narrower than interorbital distance; keratodont formula 1:2+2/2+2:1; anterior lip only with lateral papillae and large rostral gap; posterior lip with two rows of around 20 papillae, central papillae long and narrow, papillae becoming smaller towards angles of the mouth (Fig. 3c); black jaw sheaths massive and serrated; upper jaw with a medial fang, lower jaw U-shaped with medial notch.

The largest tadpole (ZMB 88346, Gosner stage 36) had 72 mm total length (body length: 23 mm).

Coloration in preservation.

Brown to dark brown, dorsal surfaces darker, venter lighter and more grayish; flanks densely beset with diffuse and small brown spots; intensity of patterning deceases from back to vent; tail fins slightly transparent, dorsal fin with dark patterning, ventral fin with fewer dark spots.

Variation.

ZMB 88346 had a particularly high body (95.4% of maximum tail height) and a keratodont formula of 1:2+2/1+1:2. Channing et al. (2012) report the keratodont formulae 3+3/2+2:1 and 3+3/1+1:2, as well as lighter coloration and less dark spots. The latter differences possibly are due to preservation differences.