It is always nice to tie up loose ends left in earlier posts, so I was pleased to find a recent paper that put a name on a diatom that I had illustrated, but not been able to name, during my examination of material from a high altitude lake in Ladakh (see “Diatoms from Pangong Tso”). I had assumed that this was a species of Gomphonema; however, Pat Kociolek and colleagues have placed it in a completely new genus, Gomphosinica.
Following their paper, the diatom that was abundant in the littoral of Pangong Tso is most likely Gomphosinica lacustris and this would be the first record of the genus in India. The type location for this species is Kalakule Lake in the Kunlum Mountains of Xianjiang Province, northwest China, some 800 km north of Ladakh, and on the other side of the Tibetan Plateau. They describe their sample as “planktonic in the lake”, whereas the populations I described formed distinct growths in the littoral zone (see “Return to Pangong Tso”). They also have recorded it from Sichuan province, in southwest China. Pangong Tso actually marks the Indian-Chinese border, so it should not be a great surprise to have found it here.
Altogether, Pat Kociolek and colleagues found three new species of Gomphosinica in China, and transferred a previously-described species of Gomphonema found in Nepal to the genus. However, they also found four species in Montana, in the USA, and made one further transfer of a Gomphoneis first described from the Great Lakes. Bear in mind, too, that Gomphosinica species are distinctive, so it is unlikely that the absence of Gomphosinica in regions other than China and the USA is an oversight on the part of diatomists. There is clearly more to learn about the biogeography of this genus.
Having said that Gomphosinica is distinctive, it is hard to say exactly how it differs from Gomphonema based on what we can see with the light microscope alone. The distinctive features can only be seen with scanning electron microscope, and it would be interesting to get some molecular barcodes from members of this genus to see how these compare with those from Gomphonema and relatives. This might also shed some light on the differences between the North American and Asian species.
The same journal part also contained a paper on diatoms from the Doon Valley, near Dehra Dun in Uttarakhand, which may shed some light on the diatoms that I found nearby in the Ganges at Rishikesh (see “Diatoms from a holy river”). I named these using the identification literature that I had to hand (mostly from Europe) and included “Gomphonema pumilum” in my list. This new paper suggests that there may be local species which look very similar, including G. juettnerii and G. doonensis. My population does not fit the dimensions of either of these exactly, and my inclination would still be that at least the larger of the two specimens I illustrated is G. pumilum, but there is enough in this paper to remind me that trusting a European flora when studying the diatoms of Asia is dangerous. Whether these diatoms actually fill different niches in their respective ecosystems, or whether they are just genetically-distinct forms of what is, basically, food for relatively unfussy invertebrate larvae on both continents is a question for another day.
Note: the photograph at the top of the post is an early-evening view of a river in the Outer Himalaya Zone in the vicinity of Dehra Dun.
Karthick, B., Nautiyal, R., Kociolek, J.P. & Ramachandra, T.V. (2015). Two new species of Gomphonema (Bacillariophyceae) from Doon Valley, Uttarakhand, India. Nova Hedwigia, Beiheft 144: 166-174.
Kociolek, J.P., You, Q-M., Wang, Q-X. and Liu, Q. (2015). A consideration of some interesting freshwater gomphonemoid diatoms from North America and China, and the description of Gomphosinica gen. nov.. Nova Hedwigia, Beiheft 144: 175-198.