Pelagodileptus sp. ?

I’ve found a few specimens of this interesting dileptid. I originally took it to be a Pseudomonilicaryon, because of the beaded macronucleus and the general resemblance to both P. angustistoma and the stouter species P. japonicum, however Peter Vďačný has suggested that it is more likely to be an undescribed species of Pelagodileptus. It has ~80 ciliary rows. The very distinctive mouth, which is surrounded by darker granules and shows no sign of a pharyngeal basket, resembles that of Dimacrocaryon amphileptoides (Dileptus amphileptoides Kahl, 1931), as does the sickle-shaped proboscis. The mouth appears slighty oblique, because of twisting in the cell, which seems to be a stable feature of this species. Foissner and Vďačný speculate that the narrowly elliptical mouth found within different dileptid genera is a convergent feature. Note the sparse ventral stripe of contractile vacuoles, as well the commonplace dorsal stripe. I was unable to observe the dorsal brush.

Apologies for the image quality: this was recorded on my Chinese ‘scope (the Olympus is having electrical problems). In the footage at the end of the video, the cell is very compressed by coverslip pressure.

From a week-old sample, collected in a cattail marsh in the Mer Bleue Bog conservation area. The sample was taken from a floating mat of filamentous algae and the carnivorous plant Utricularia. Mid October, 2013.

Body length 400 µm; width 69 µm. L:W ratio, 1:5.8