Sunday, 27 April 2014

Differences between Nihonogomphus at Huu Lien and N. schorri at Xuan Son, a case for Nihonogomphus lieftincki

Yesterday, April 26, I visited Huu Lien. The day ended a little weird, when I was questioned by 5 guards demanding so see the insides of my car, the contents of a plastic bag (with Kameliya's rubber boots) and so on. It is of course good they keep an eye on things, so I tried to be cooperative to some extent. But the guy walking by with illegal electric fishing equipment was not even glanced at and the sound of chainsaws from various directions where people were cutting down any larger and accessible trees also did not seem to bother anyone, which made it look like a racial profiling exercise to me. But then again, ecotourism is quite an alien concept here and that anyone would want to take pictures of Odonata, well, weird…

Surprisingly, yesterday was rather sunny and I had another shot at various gomphids. I was able to catch two Nihonogomphus specimens and was struck by the differences with the Nihonogomphus schorri specimen from Xuan Son the other day. I doubt whether the differences are large enough to warrant a discussion of the species level, but it is an interesting case of geographical variation or inter population variability.

First, here is a Xuan Son specimen photographed perched and one from Huu Lien.

Xuan Son, Nihonogomphus schorri, male, April 13

Huu Lien, Nihonogomphus species, male, April 26
Apart from some differences in the coloration, the difference in shape is striking. I only saw one perched in Xuan Son, so it is difficult to generalize. But the difference is born out also by structural differences between the specimens caught. HW shorter and body longer in Huu Lien (BL 47mm against 44mm, HW 34mm against 35mm). (Measurements given by Do & Karube for N. schorri BL 45mm, HW 32.5mm)

The Huu Lien specimen in hand, different from the one perched in the photo

Xuan Son specimen in hand, also different from one perched in photo
An interesting difference, apart from the body shape also evident here, is the black line over the metapleural suture. The Huu Lien specimens all have a thin branch, sharply defined, which is much more diffuse in Xuan Son, giving the impression of a continuous broad black stripe rather than a branch. In the drawings by Do & Karube this branch is completely lacking and the stripe narrows dorsally.

What can already be seen here is the difference in shape of the first segment of the penile organ. Let's pull that close:

Huu Lien Specimen 1, look at the hook directed posteriorly

Huu Lien Specimen 2, identical hook

Xuan Son Specimen, no hook, just pointed straight down
What is interesting is that the shape of the first segment of the penile organ of the Xuan Son specimen is closest to the drawing in Do & Karube, which was of course based on Huu Lien specimens of N. schorri.

Huu Lien Specimen 1, appendages in ventral view. Note the inferior appendage is not spread and although bent upwards, reaches the shoulder of the superiors.

The Xuan Son specimen, spread in a V and falling short clearly off the shoulder  of the superiors

Second Huu Lien specimen, identical to the first specimen
Interestingly again is that the Xuan Son specimen fits well the drawings in Do & Karube, in which the inferior appendage is spread in a V and falls clearly short of the shoulder.
Dorsal view Huu Lien specimen 1

Dorsal view Huu Lien specimen 2

Dorsal view Xuan Son specimen
Note that the shapes and color are consistently different (in the small sample), also given the two in situ photos of life specimens. Both Xuan Son specimens (including the perched specimen) have half of S10 yellow, which is obscured in the Huu Lien specimens, but again clearly illustrated in Do & Karube.

The lamina of the anterior lamina is also drastically different. It is, in short, a completely different structure. And the anterior hamule, with a shoulder in the Xuan Son specimen, as to be expected for N. schorri, only broadens somewhat, without a clear shoulder, in the Huu Lien specimens.

This is a Huu Lien specimen, note the rectangular, but almost square,  lamina at the bottom of the structure

This is the Xuan Son N. schorri. Note the narrow and clearly excavated lamina, which also almost disappears under the adjacent structure. It is very different.
It is clear that the specimens from Huu Lien, the type locality of Nihonogomphus schorri, are a different species. As a matter of fact, shape of appendages and penile organ first segment, shape of anterior and posterior hamuli, measurements, black labrum, all fit very well Nihonogomphus lieftinck, a species from Fujian, Hunan, Hubei and also Guangdong in China. See the drawings in Chao (1954), and in Wilson & Xu (2009), including. The differences in coloration could be geographical variation. With a more thorough study of the type material of N. lieftincki structural differences might become apparent, but for the time being I call this Nihonogomphus cf. lieftincki.

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