Danio year 2009: Rakhine Yoma

 Fish, Travel  Kommentarer inaktiverade för Danio year 2009: Rakhine Yoma
Jan 012010
 
thermometerat minus 10 degrees

Stockholm area, Sweden, late December 2009

In the last few hours of the first decade of the 2000s, realising that my friends in the western Pacific time zones are already into the new decade, and writing this is not likely to come to an end this year. Snow and cold (-10 to -15C) outside demonstrate why tropical fish won’t do in the garden. It was night outside already at 1600h, but inside electricity glows in every corner and it is a comfortable +23C, so the fish inside are just fine.

In 1998, Ralf Britz and I travelled westward from Yangon in a battered but still comfortable Toyota minibus, with driver and guide. We did not have permission to fly to Kalaymyo to look for Badis ferrarisi (this was a Badis trip, and a considerable contribution to the Badis revision of 2002). Our substitute goal was the western slope of the Rakhine Yoma (aka Arakan Mountain Range), separated from the Ayeyarwaddy drainage and ichthyologically quite unknown. Of course Day had been there, up to Akyab (Sittwe), and Hora had reported fish from Sandoway (Thandwe), but nothing substantial was known. It took a whole day to travel the dirt roads and hitting Gwa on the Andaman Sea coast, arriving late in the evening. Of course we made a few stops on the way, but very brief.

Sampling sites in Rakhine Yoma in 1998.

The soft hills of Rakhine Yoma in a top view.

We then travelled north along the coast to Taunggok and returned to the Ayeyarwaddy at Pyay, making excursions up and down logging roads to find small streams with freshwater. The coastal stretch along the main road was either brackish water or no suitable water at all. Unfortunately, in the remaining four days, no badid came into the seine, so badids are probably absent from the area we sampled, betwen Gwa and Taunggok. That may be significant, or just due to poor sampling. We did get quite some interesting Garra, already described by me and Fang (2004), and quite some danios and other cyprinids endemic to the region. The Rakhine Yoma forests are actually a biodiversity hotspot with numerous endemic species of animals and plants, so no surprise endemic species of fish are also abundant. Endemic fish species that come to mind are Danio feegradei, Garra vittatula, G. rakhinica, G. flavatra, G. propulvinus, G. nigricollis, Puntius binduchitra, Batasio elongatus, Hara spinulus, Akysis vespertinus, and Channa pulchra.

Danio feegradei has already been described from Thandwe (then Sandoway) by Hora, who also reported Danio choprae from the same locality. The latter was first described from near Myitkyina in the upper Ayeyarwaddy drainage. The danionins we encountered, of course included D. feegradei, but also Hora’s choprae. The latter turned out to have very little in common with D. choprae and in fact to represent a new species. Along with it we were impressed by a huge danio that had two dark blotches on the side and inhabited small streams in the deep forest. This one nobody seems to have seen before, and the colour pattern was certainly not reported before.

Eventually these two new danios got their names. In 2009, 11 years and a bit more after we collected them. Why it takes so long time from discovery to description?

Danio aesculapii, preserved holotype.

The choprae-like fish was named Danio aesculapii, and with its 29 mm max SL in the wild is one tiny fish. The name was inspired by the popular name of snakeskin danio. In the living fish, not much of snake pattern shows, the most impressive in this highly agile being is a golden shine along the middle of the dorsum. In the preserved fish, however, there is a series of dark vertical bars anteriorly on the side and two rows of dark spots from above the anal-fin origin to the caudal-fin base. Unlike most Danio, D. aesculapii does not possess stripes on the caudal fin. The caudal peduncle is relatively deep, and has more scales, 12 around the middle, than most other Danio, which have 10 only. Asklepios or Aesculapius was the Ancient Greek god of medicine, typically equipped with a staff with a snake or two wrapped around it.

Devario xyrops. A male, just collected.

The large double-blotched species got named Devario xyrops with reference to the sharp ridges rising along the anterior part of the orbit (xyrops means razor-eye), and is also diagnosed by the colour pattern with a diffuse blotch formed by irregular vertical bars anteriorly on the side, and separated from a well-defined dark stripe on the posterior part of the body. It was getting dark, and we were exhausted after chasing fish up and down the stream all afternoon, but realising that this was an exceptional species, we made an effort to take a live colour photo as per above. The pink sheen ventrally probably derives from the red lid of the container on which the photo tank was placed, however. Devario xyrops is large for a danio, with the largest specimen 77 mm SL. Comparing with other Devario we found that the colour pattern is not fully unique. Also Devario browni has a separation of the lateral marking into an anterior blotch and a posterior band, but not as conspicuous as in D. xyrops. A similar species, D. anomalus, was described by Conway et al. (2009) from Bangladesh, and differs in being much more slender.

Small pool close to Thandwe, habitat of Danio aesculapii.
Habitat of Devario xyrops and Danio aesculapii north of Thandwe.
And with that pass the last day of 2009 and the first of 2010. It is still cold out there, and very dark. Not a very inspiring setting, but not all days are like this so I do dare wish you a productive 2010 full of excitement and happiness!

References
To learn more you can download the original descriptions of both Danio aesculapii and Devario xyrops which are available online as Open Access from the publisher’s website:

And here are other papers mentioned (none of them Open Access):
Conway, K.W., R.L. Mayden & K.L. Tang. 2009. Devario anomalus, a new species of freshwater fish from Bangladesh (Ostariophysi: Cyprinidae). Zootaxa, 2136: 49-58.
Hora, S.L. 1937. Notes on fishes in the Indian Museum. XXXI. On a small collection of fish from Sandoway, Lower  Burma.  Records of the Indian Museum, 39: 323-331.
Kullander, S.O. & R. Britz. 2002. Revision of the family Badidae (Teleostei: Perciformes), with description of a new genus and ten new species. Ichthyological Exploration of Freshwaters, 13: 295-372.
Kullander, S.O. & F. Fang. 2004. Seven new species of Garra (Cyprinidae: Cyprininae) from the Rakhine Yoma, southern Myanmar. Ichthyological Exploration of Freshwaters, 15: 257-278.
Image credits:

Map from the NRM Ichthyology Collection online database, using Google Maps

All other images: Sven O Kullander, CC-BY-NC
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