Wednesday, 22 October 2014

Shall we "Planaeschna"?

A few weeks back I caught both several Planaeschna gressitti in Pia Oac and a P. tomokunii lookalike female. I started thinking about some of their identifying features. For one, the differences between P. tamdaoensis, as described by Asahina (1996) and P. gressitti (Karube, 2002) are very similar in patterning, both on the body and on the face. Differences appear when looking in detail at the appendages and penis. I was quite confident that the specimens collected in Pia Oac were P. gressitti, just as those, at similar altitude from Mau Son. The fact is though that these locations are far removed and that Tam Dao is sort of in between. P. tamdaoensis therefore occurs in the middle of the P. gressitti range and at similar altitude (around 1000m asl). Both the specimens from Mau Son and from Pia Oac had the nice balloon-shaped distal segment of the penis, quite unlike that drawn by Karube for P. tamdaoensis (although this is not depicted in the original drawings of Asahina). Apparently it was drawn later. I did not think more about this at the time, as it seemed to be straightforward. But last weekend (Saturday October 18) I went back to Pia Oac and was lucky enough to catch a male P. tomokunii lookalike, just some 25 meters from where I had caught the female two weeks earlier. It is larger, closer to P. tomokunii and fits all characteristics. It had however a balloon-shaped penis, quite different from that drawn for this species by Sasamoto et al (2013). I was confused and pondering. Might it be that the changes induced post-mortem and after preservation alter the configuration of the penis? In most cases this is not the case, but maybe it was different for Planeaschna species with their bloated and soft organs? In fact, as below pictures show, this is very much true. Photos of fresh specimens are balloon-shaped, but after their acetone bath they are greatly changes, both in color and in shape. This makes this characteristic, in my view, unreliable, given that most drawings are done in the lab a while after preservation and not on the fresh specimens. The differences in the appendages of P. tamdaoensis and P. gressitti may well be real, but these too twist sometimes upon drying and the exact shape can only be ascertained three dimensionally when differences are slight, as is the case in many Planaeschna. This is not to say that P. gressitti and P. tamdaoensis are not different species, but given the paucity of available material, I would not be surprised if they eventually would turn out to be conspecific.
If we disregard the penile organ shape for the P. tomokunii lookalike and the slight differences in the appendages, but consider the great similarity on patterning and structure, plus the fact that the male is only 2 mm smaller than the specimen described by Sasamoto et al, it would seem likely that this and the female of two week earlier, are in fact that species. The female then is just a small specimen.

First, let's have a look at fresh distal segments of the penile organ in ventral view, and compare to their post treatment shape:

The fresh distal segment of the penis of P. tomokunii in ventral view, very whitish and with globular and divided apex.
The same segment after preservation. Much reduced, the earlobes directed in the opposite direction, the color yellowing brown and the apex no longer divided, but forming one continuous shape.
The same segment in a fresh P. gressitti male, also very globular and with a split apex.
A P. gressitti male after preservation. In this case the globular effect is completely gone, the sides now straight and angular, although the split in this case is still present. Again the earlobes completely distorted. This is almost (apart from the direction of the lobes) the shape of the segment as drawn by Karube for P. tamdaoensis, indicating that this feature is unreliable.


Male Planaeschna gressitti (left) and P. tomokunii (right), both collected on October 18. P. gressitti with two yellow spots on dorsum of S10, not seen in the others I collected.
Male P. tomokunii. Note the reduced dorsal patterning on the abdomen with only central dorsal spots from S5 onwards.
Dorsal pattern on the thorax
Facial pattern, with largely pale-yellow labrum, with darker lower border, postclypeus with two orange pits and brownish center to the frons. Very similar to the female.

Dorsal view of appendages of P. tomokunii, more slender than P. gressitti
Lateral view of the same with relatively broad superiors
And the same ventrally


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