Scleropages formosus (Muller & Schlegel, 1840)

Van Oijen, Martien J. P. & Van Der Meij, Sancia E. T., 2013, The types of Osteoglossum formosum Müller & Schlegel, 1840 (Teleostei, Osteoglossidae), Zootaxa 3722 (3), pp. 361-371 : 368-370

Remarks on S. formosus by early authors

Valenciennes (in Cuvier & Valenciennes 1846: 304), not having access to a specimen of S. formosus , gives a summary of the characters described by Müller & Schlegel (1840 -1845). The description of the colouration is not copied from the original description, but based on his own observations of the colours of their figure (see Fig. 1 ).

Bleeker (1851: 436) described a specimen (222 mm TL) from the river Sambas, NW Borneo. After the description he wrote [translated]:

“In the specimens of Osteoglossum formosum Müller & Schlegel (1844) from the lakes along the Doeson river in South East Borneo the body depth fits 4 times in its length, its width fits 2½ times in its length, its barbels are about as long as the snout, the dorsal fin has 18 rays of which only the first 3 are undivided, and the caudal fin together with the caudal peduncle fits 5 times in the total length, whereas this in my specimen fits only 4 ½ times in the TL. These differences, which partly might be explained by the difference in age, do not give me the right to consider my specimen from the Sambas as a separate species.”

Bleeker did not comment on the differences in colouration. He describes the body colour of his specimen from the Sambas as green, the belly as silvery and all fins and fin rays as golden or dark brownish. Possibly Bleeker in Batavia did not possess a coloured edition of Müller & Schlegel (1840). Bleeker mentioned O. formosum in at least eight other publications ( Weber & de Beaufort 1911: 283), but in all of them the name appears only in species lists.

In his “ Atlas Ichthyologique ” Bleeker (1870-1875, Vol. VI: 145, Pl. CCLXXVI) states that Müller & Schlegel (1844) published a very detailed description and a beautiful figure. However, he was of the opinion that the figure did not properly reflect the habitus of the species. Bleeker’s own description was based on 11 specimens from Sumatra, Banka and Borneo. Bleeker did not examine specimens from the type locality. The specimen figured in the Atlas (see Fig. 11A ) is quite different from that in Müller & Schlegel (1840), especially in colouration. In the Atlas Bleeker describes the colouration as follows [translated]:

“Body colour, dorsal part dark olive green, ventral part silvery or golden. Inner part of iris golden, outer part beautiful green. Barbels golden or brown. Fin rays yellow or golden, fin membranes pearl coloured or bluish hyaline.”

Apparently Bleeker considered O. formosum a very variable species.

Günther (1868: 378), in his account of O. formosum , gives no details of the colouration. Von Martens (1876:

304) characterized this species as follows [translated]:

“ Osteoglossum is the most beautiful fresh water fish of Borneo, with a length of 0.62 m, with large scales, a lustre of gold along the free margin; the short dorsal fin is set backwards as in our pike, the pectoral fins long and acute, a strong barbel on the lower jaw; the vertical fins and the pectorals blackish with a broad orange red seam, the belly with a sharp keel, which is not formed by one scale as in the herring but by two scales. Near the lake Danau Sriang this fish was named Silo.”

From a colour plate of a specimen from lake Sentarum published with this description (see Fig. 11B ) it is clear that the colouration of von Marten’s specimens differs greatly from the specimens of Müller & Schlegel ( Fig. 1 ) and Bleeker ( Fig. 11A ).

According to Weber & De Beaufort (1913: 13), the colouration of S. formosus is dorsally dark green, the sides and ventral sides silvery or golden green, sometimes with longitudinal rows of oblique dark patches, shining through the lateral scales (shown in their black & white drawing of the species). Fin membrane bluish, the rays golden brown. According to Dr Isbruecker (Zoological Museum Amsterdam, now Naturalis Biodiversity Center), the ZMA collection holds only two specimens that were present before 1913; one from Borneo (from Bleeker’s collection) and one collected in Palembang, Sumatra, in 1908. These are the localities marked with an explanation mark in Weber & De Beaufort (1913: 13). The authors thus did not see live specimens and their colour description must have been compiled from descriptions of previous authors.

It is remarkable that none of the early authors commented on the differences in colouration and/or body shape in specimens from different areas. In “The Asian Arowana”, a book for dragon fish hobbyists, Goh & Chua (1999) present photographs of a number of colour varieties, again diverging from the earlier published colour figures. Pouyaud et al. (2003: 288) analysed “ 36 specimens representing all known colour varieties (except the Cross Back Golden) that died since 1998 after being caught by fishermen or kept and bred in tanks either by Indonesian governmental research institutions or by private fish farmers.” The examined material was a mixture of wild and cultivated specimens. Unfortunately, type series of their new species are also composed of wild specimens, descendants of a wild brood stock, and offspring of private strains. It is also regrettable that the authors chose juvenile specimens to represent two of the three new species as well as for the neotype. Pouyaud et al. (2003) did not compare the colours of their new species with those of the figures by early authors mentioned above, with one exception. They proposed to restrict S. formosus to the “Green variety” on the basis of the colour description of Weber & De Beaufort (1913), which is cited in full. When the last mentioned description is compared with the colour figure from Müller & Schlegel (1840) it is clear that they are quite different. If Pouyaud et al. (2003) had checked the original figure, they would have noticed that it does not compare to the colouration of specimens of the “Green variety”. In certain characters Pouyaud et al. “Silvers” seems a better match.

Figures

FIGURE 11. Habitus figures of Scleropages formosus (Müller & Schlegel 1840) from the literature. A. From Bleeker (1870, Tab. 276), specimen from Borneo, 335 mm TL; B. From Martens (1876, Pl.13), specimen from Lake Sriang, Borneo, ca 620 mm TL; C. From Weber & de Beaufort (1910, Fig. 7), 430 mm TL. Mirror image. Probably ZMA.PISC.100740, from Djambi, Sumatra.

FIGURES 1–8. Osteoglossum formosum Müller & Schlegel, 1840. From Müller & Schlegel 1840-1845, reproduced at ca. ½ of original size, with original captions.1. Osteoglossum formosum; a little more than half of the natural size; 2. Dorsal view of the skull; natural size; 3. Lateral view of the skull; natural size (gill cover removed); 4. Central bony element of the tongue; natural size; 5. Lateral view of scale from the centre of the flank, showing the mucus canal of the lateral line; natural size (the light part shows the hidden area, the dark part the exposed area); 6. A small piece of the exposed part of the scale; enlarged; 7. A small piece of the hidden part of the scale; enlarged; 8. Outline of the body in a transverse section.