Astylosternus occidentalis Parker, 1931

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 : 141-143

Astylosternus occidentalis Parker, 1931

Material examined.

ZMB 77317, 2 tadpoles, Gosner stage 25, Guinea, Déré, 419 m, 7°36'20.0"N, 8°15'36.5"W, 7 August 2010, leg. M. Hirschfeld; ZMB 77440, Gosner stage 25, Guinea, Ziama, 664 m, 8°23'99.3"N, 9°17'13.7"W, leg. M. Hirschfeld; ZMB 77438, Gosner stage 26, Guinea, Fouta Djallon, Chûte Saala, 939 m, 11°17'26.2"N, 12°29'58.0"W, July 2010, leg. C. Brede & J. Doumbia; ZMB 77439, Gosner stage 25, Guinea, Fouta Djallon, Chûte Dintin, 760 m, 10°49'13.1"N, 12°11'30.7"W, 24 July 2010, leg. C. Brede & J. Doumbia; ZMB 75368 2 tadpoles, Gosner stage 41 (A) and 37 (B), Sierra Leone, Gola North, leg. J. van der Winden; ZMB 37564, Gosner stage 26, Guinea, Mt Nimba, leg. M. Lamotte.

The description is mainly based on the two tadpoles accessioned as ZMB 77317. These and ZMB 77440 have been already described by Rödel et al. (2012), who also provide genetic sequences for specimens across the entire range of the species.

Description.

Long slender tadpole with strong, muscular tail (Fig. 10); body oval in dorsal and lateral view; snout broadly rounded in dorsal view, more narrowly rounded in lateral view; body length 31.1 ± 2.8% of total length; body height 40.2 ± 2.2% of body length; body width 56.1 ± 4.9% of body length; eyes positioned dorsolaterally, eye diameter 11.5 ± 2.3% of body length; nostrils positioned dorsally, closer to snout tip than to eyes; inter-nostril distance 62.2 ± 2.7% of interorbital distance; tail fins narrow; ventral fin originating from tail base, dorsal fin insertion a bit posterior to tail base; ventral fin height 71.6 ± 13.7% of dorsal fin height; highest part of tail approximately in the middle of the tail; body height 84.8 ± 9.4% of maximum tail height; tail axis width 53.1 ± 8.6% of body width; tail axis height 71.9 ± 14.2% of maximum tail height; tail tip broadly 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 with a few lateral papillae and large rostral gap; posterior lip with 2-3 rows of about 30 short and triangular papillae (Fig. 10c); papillae of inner row smaller than those of marginal row; black, massive, serrated jaw sheaths; upper jaw broadly arched with a small medial projection (fang), lower jaw narrowly U-shaped.

The largest tadpole in Gosner stage 25 measured 95.9 mm total length. Gosner stage 41 tadpole measured 77.5 mm. Tadpoles with more than 10 cm total length have been caught ( Guibé and Lamotte 1958b; MOR unpubl. data).

Coloration in preservation.

Body more or less uniform dark brown; ventral lighter, slightly grayish; tail fin margins are missing dark pigmentation; last third of tail darker to almost black (Fig. 10). In life, ventral surfaces grayish; lateral and dorsal parts, as well as tail, with a small but very dense yellow and brown speckling (Fig. 11). This pattern progressively becomes denser and darker towards tail tip.

Variation.

ZMB 75368 (Gosner stage 41) is very light brown in comparison to other specimens. According to Lamotte (1985), tooth row P2 is continuous and not divided, thus tooth row formula would be 1:2+2/1+1:2. According to Lamotte, the body is almost evenly pigmented, with lighter lateral sacs and lightly speckled tail. The tadpole of this species was first described by Lamotte and Zuber-Vogeli (1954) as A. diadematus. Parker (1936) mentioned A. occidentalis tadpoles from Liberia. More recent descriptions have been published by Channing et al. (2012) and Rödel et al. (2012).