picture to see a larger version of the grapes
There grows in Cancún a so-called Sea Grape or Beach Grape tree. Reasons for the common name will be easy to imagine seeing the attached photo. The grapes are edible.
Coccoloba uvifera, as it is called scientifically, is a salt resistant species now used as an ornamental tree, that has very large and beautiful round leaves, with a leathery texture. These seemed to me an excellent material to continue trying the possibilities of the mesotome (the name I propose for a homemade slicer made from double edged razor blades, see footnote 2). The results of this test are illustrated in the following images; the leaves show a strange architecture, with narrow spongy parenchyma and what would have to be the palisade parenchyma distributed in bundles compressed at the base(?) where the cells appear dark and colored. Among such bundles run identifiable vascular packages easily seen with polarized light, but feebly visible with normal illumination.
hardness of the leaf made it difficult to obtain the sections, mainly
because at first
I tried using razor blades of the "thin" type. Changing to blades of
normal thickness, the sections were possible without problems.
interesting was that many of the leaves showed a surface marked by
innumerable galls that protruded from both faces of the leaf and which
thought could either be caused by fungi (but not
very probable due to their structure, which were small volcanoes in
sides of the foliar lamina) or, almost certainly, by parasitic insects.
It was a
magnificent opportunity to try the mesotome to aid an investigation
pathology. But although I do not doubt that it will have utility on
occasions, I had to give up after breaking two instruments.
I could only
cut the incipient galls in young leaves, which are where the insect
With incident light we can see in the two images below right and with a magnification of x25 the structure of the galls in a vertical section.
empty gall I found the shed skin of a pupa, and at once verified that
was a dipteran. I looked for the possible identity on the Internet. The
I found is dated 1970 and it identifies a dipteran of the Cecidomyidae
family, from a group called
"gall midges", with a North American species (from Florida,
known as Ctenodactylomyia watsoni,
whose nutgalls and maker can be seen in the following pictures taken
from Circular 97 (1970) of the Florida
Department of Agriculture & Consumer Services.
I do not doubt that the genus of the
Cancún midge is the same one, it seems to me that the shape of
the galls and
the double incubation chamber shows that it must be a different
spite of the relatively short distance between the
To break two mesotomes can also have its compensations.
1) I am neither a phytopathologist nor an entomologist. Even if I could obtain the adults which would allow identification of the parasite to species, I could not determine it. If there is amongst the readers somebody with knowledge and suitable bibliography to do it, I could provide the graphical materials and all the biological materials that can be needed. My e-mail address appears at the end of this article.
2) I described the device in Micscape as a slicer (see this article). In French it is now named “tranchette”, in Spanish it would be “rebanador” but that is really cacophonic. It seems to me that it is better to adopt a name more easily identifiable with its function. I propose “mesotome”. Of course it is not a microtome, but the sections it provides, to be studied with a microscope, could not be called macrosections. From mesotome it is easy to derive other languages derivatives.
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