This larva had clearly defined cells except at the very anterior and posterior ends that ranged from what is considered brick-like cells at the anterior end to elongated triangular cells at the posterior end. The esophagus was approximately the same length, the width the same, the length of tail the same as what is more typical of poteriostomum spp. or even Triodontophorus spp. I have included a picture, but was unable to take one with scale bars before the larva swam away (heat treating the larva to "sedate" it unfortunately degraded it's cells such that it could not be found again).
I work with horse strongyles since 1987 and I have never seen L3 with 24-26 cells. I believe this can be a modification, or some specific morphotype, perhaps from Triodontophorus sp. The shape and organization of cells are pretty much the ones from this genus.
In Cyathostomum s.l. I found L3 with 6,7,8 and 9 cells. so I would not be surprised that could happen with other genera. I hope it can help your research.
Luis Carvalho
Dear Jennifer,
I would just like to share my experience in identifying ovine infective larvae regarding their imaging. It is very difficult to take an image of live larva which is very motile. Killing the larvae with Lugol's iodine would help to take more images, including the ones with scale bar. Lugol's iodine does not alter the shape of intestinal cells. Larvae have to be as fresh as possible.
Best regards!
Stanislav
Stanislav,
We frequently use Lugol's in my lab, but I commonly work with feces from our parasitology horse herd that hasn't been treated since 1970. Needless to say, there are so many larvae that even diluting the larvae 10 times doesn't always help. Lugol's solution doesn't give me enough time to examine all the larvae before their cells become degraded. Other labs freeze the larvae in the nematode chambers for a few minutes, and it still isn't enough time to examine them all before they thaw. Typically, I heat the nematode chamber on a hot plate at 55 degrees Celsius for 2 or 3 minutes, and this renders them immobile for the longest period of time without degrading. Unfortunately, repeated heating is quite destructive, as you can imagine. The answer may be to heat them, and only add Lugol's if I find something of interest. Hopefully it wouldn't be too destructive.
Thank you though!
Dear Jennifer,
I work mainly with nematodes of small ruminants and I know that the identification process of infective larvae is laborious. I also usually use morphological features for species identification. If you do not need live larvae, try to heat L3 in a 2% formalin suspension to 55 oC for about a minute. Larvae will die but their morphology remain unaltered. Nevertheless I increasingly use PCR based techniques because some larvae of nematode species are morphologically indistinguishable. Moreover morphology of nematodes can be altered by many factors (e.g. host immune system, breed, diet, concurrent parasitic infection, fixative medium). I think that development of your larvae was affected and an untypical intestinal cell number occured as a result of this process. In this case molecular techniques are necessary for reliable identification.
Jarda
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