Astylosternus batesi (Boulenger, 1900)

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 : 133-135

Astylosternus batesi (Boulenger, 1900)

Material examined.

ZMB 82863 (GenBank MK318840), Gosner stage 25, Cameroon, Mt Kala, 899 m, 3°50'27.66"N, 11°20'52.44"E, 9 November 2011, leg. M.F. Barej, H.C. Liedtke & N.L. Gonwouo; ZMB 82864 (GenBank MK318841), Gosner stage 25, Cameroon, Ebo Forest, Bekob, 893 m, 4°21'51.96"N, 10°25'10.26"E, 30 September 2011, leg. M. Dahmen; ZMB 82865 (GenBank MK318842), Gosner stage 25, Cameroon, Ebo Forest, Bekob, 852 m, 4°21'54.36"N, 10°25'17.22"E, 1 September 2011, leg. M. Dahmen; ZMB 82866 (GenBank MK318843), 2 tadpoles, Gosner stage 25, Cameroon, Ebo Forest, Bekob, 917 m, 4°21'27.42"N, 10°25'5.94"E, 9 January 2011, leg. M. Hirschfeld & F. Grözinger; ZMB 82784 (GenBank MK318844), Gosner stage 36, Cameroon, Ebo Forest, Bekob, 807 m, 4°21'54.3"N, 10°25'24.54"E, 10 January 2011, leg. M. Hirschfeld & F. Grözinger.

All tadpoles were caught in small to medium-sized streams. The description is mainly based on ZMB 82865 and ZMB 82784. Genotyped tadpoles have been compared with an adult frog (MC11_205; GenBank MK318905) from Mount Kala, near Kala village, Cameroon. The genotyped individuals were genetically almost identical, the maximum uncorrected p-differences in pairwise comparisons was 0.2% (1 bp).

Description.

Long slender tadpole with long, muscular tail and narrow fins (Fig. 1); body oblong oval in dorsal and lateral view; back with a medial longitudinal-depression; snout rounded in dorsal view, more narrow-rounded in lateral view; body length approximately 0.3 (31.3-36.7%, N = 3) of total length; body height 46.3 ± 5.6% of body length; body width 60.5 ± 6.0% of body length; eyes positioned dorsolaterally, eye diameter 11.3 ± 1.4% of body length; nostrils positioned dorsolaterally, closer to snout tip than to eyes; inter-nostril distance 75.2 ± 9.7% of interorbital distance; tail fins narrow, dorsal and ventral fin originating from tail base, ventral fin height narrow, reaching 70.7 ± 4.7% of dorsal fin height; highest part of tail approximately in the middle of the tail; body height 91.7 ± 11.5% of maximum tail height; tail axis width 41.3 ± 11.4% of body width; tail axis height 59.8 ± 13.9% of maximum tail height; tail tip rounded; vent tube dextral; body with large lateral air 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+2:1; anterior lip only lateral with papillae, large rostral gap; posterior lip with 2-3 rows of approximately 20 uniform papillae, papillae triangular and approximately as long as broad (Fig. 1d); black jaw sheaths massive and serrated; upper jaw with a big medial projection (fang); lower jaw U-shaped with a medial notch.

The largest tadpole, still Gosner stage 25 (ZMB 82865), measured 25 mm body length. The most developed specimen (ZMB 82784, Gosner stage 36) had similar body length of 24.7 mm. When reconstructing the tail tip of the largest specimens by the shape of tails in smaller specimens we estimate the maximum total length of A. batesi tadpoles to be 60-80 mm.

Coloration in preservation.

Brown, slightly fading from snout to tail; dorsal surfaces with irregular dark speckles; ventral surfaces without or only few darker markings; tail fins sometimes with dark blotches or speckles, partly transparent. Life color of very small specimens with much yolk, were much lighter than larger specimens (Fig. 2), showing distinct black blotches on body and tail axis, tail fins completely transparent.

Variation.

According to Channing et al. (2012) the anterior lip has three rows of keratodonts, 1:2+2/2+2:1. We cannot exclude that our specimens lost the very short third row, likewise it is possible that populations vary in this character. Channing et al. (2012) describe coloration to be partly yellowish or reddish on back and flanks, ventrally bluish to violet, dark spots on all surfaces, lessso on the venter. Angel (1930) described a tadpole as Gampsosteonyx batesi . As this tadpole originated from an area that is outside the present day range of A. batesi , the description might have be based on another Astylosternus species ( Channing et al. 2012).

Taxonomic remark.

Whereas all genotyped tadpoles were genetically almost identical amongst each other and an adult from Mount Kala, Cameroon, further genetic comparisons with specimens from across the range of the species revealed three distinct genetic lineages (results not shown). Our tadpoles originated from Cameroon. All genetic samples from Gabon and the Republic of Congo, fell into a different clade. As the type locality of A. batesi however, is " Benito River, Gaboon" ( Boulenger 1900), the tadpoles on which our descriptions is based may thus actually belong to an undescribed species within the A. batesi -complex.