Astylosternus montanus Amiet, 1978

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 : 141

Astylosternus montanus Amiet, 1978

Material examined.

ZMB 82871 (GenBank MK318857), 2 tadpoles, Gosner stage 28 (A) and stage 25 (B), Cameroon, Mt Manengouba, 1290 m, 4°58'23.76"N, 9°52'31.8"E, 21 November 2010, leg. M. Hirschfeld; ZMB 82872, Gosner stage 25, Cameroon, Mt Manengouba, Ebonemin, 1365 m, 5°0'33"N, 9°46'30"E, 14 December 2010, leg. M. Hirschfeld; ZMB 82873, 2 tadpoles, Gosner stage 25, Cameroon, Mt Manengouba, Ebonemin, 1372 m, 5°0'46.5"N, 9°46'5.82"E, 16 December 2010, leg. M. Hirschfeld; ZMB 82874 (GenBank MK318860), 2 tadpoles, Gosner stage 35, Cameroon, Mt Manengouba, Ebonemin, 1417 m, 5°1'27.6"N, 9°45'53.2"E, 15 August 2011, leg. M. Hirschfeld; ZMB 82875 (GenBank MK318861), Gosner stage 25, Cameroon, Mt Manengouba, Ebonemin, 1356 m, 5°1'33.4"N, 9°45'46.7"E, 16 August 2011, leg. M. Hirschfeld; ZMB 82876 (GenBank MK318862), Gosner stage 25, Cameroon, Mt Manengouba, Ebonemin, 1372 m, 5°0'46.5"N, 9°46'5.8"E, 7 October 2011, leg. M. Hirschfeld.

All tadpoles were caught in small to medium-sized streams. The description is mainly based on ZMB 82875. The genotyped tadpoles have been compared with an adult from Mount Rata, Rumpi Hills, Cameroon (MHNG 2715.35; GenBank MK318863). The uncorrected pairwise p-difference between tadpoles and between tadpoles and the adult ranged from 0.20-0.71% (1-4 bp).

Description.

Robust tadpole with long muscular tail (Fig. 9); body bullet-shaped in dorsal view, more oval in lateral view; back with a longitudinal medial depression; snout broadly rounded in dorsal view, more narrowly rounded in lateral view; body length 33.3 ± 1.0% of total length; body height 43.8 ± 4.5% of body length; body width 55.8 ± 5.0% of body length; eyes positioned dorsolaterally, eye diameter 10.5 ± 0.8% of body length; nostrils positioned dorsolaterally, closer to snout tip than to eyes; inter-nostril distance 81.8 ± 11.5% of interorbital distance; tail fins narrow; ventral fin originating from tail base, dorsal fin slightly behind, ventral fin height 70.7 ± 6.8% of dorsal fin height; highest part of tail at about middle of tail length; body height 104.6 ± 12.2% of maximum tail height; tail axis width 47.9 ± 9.3% of body width; tail axis height 70.2 ± 10.2% 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, close to snout, narrower than interorbital distance; keratodont formula 1:2+2/2+2:1; anterior lip with large rostral gap, only few small papillae anterior to angles of mouth; posterior lip with two rows of around 30 triangular papillae, slightly longer than wide with rounded tips (Fig. 9c); black, massive, serrated jaw sheaths; upper jaw arched with a small medial projection (fang), lower jaw V-shaped.

The largest tadpole in Gosner stage 25 has a body length of 22.5 mm; the longest one (Gosner stage 28) had a total length of 73.2 mm.

Coloration in preservation.

Basic color brownish, dorsal surfaces darker than ventral ones, turning into yellow, tail lighter brown; tail axis with few dark speckles; tail fins very light brown, semitransparent and with a longitudinal row of small spots on the margin of dorsal fin.

Taxonomic remarks.

As in A. batesi and A. fallax , we have molecular evidence for cryptic diversity in A. montanus . Apart from the above listed material, we had access to further samples which represented an additional genetic lineage. The distances between the two clades reached an uncorrected pairwise distance of 2.5%.