The type of pheromones in glands called osmforos,

The tiny orange-hued flowers of the
orchids of the genus Specklinia can be powerfully attractive, but also
deceptive. These plants -which grow in Costa Rica and Latin America- employ a
strategy of sophisticated and even “truculent” seduction to get the
tiny fruit flies (Drosophila) to approach them, stay for hours around them and
then They take their pollen to guarantee the reproduction of the species.

This technique
consists of secreting chemicals very similar to the hormones that insects emit
to alert others that there is food somewhere. Scientists collected specimens of
the flies – males and females – and subjected them to genetic analysis. This is
how they managed to identify 13 species grouped under a single genus
Drosophila, better known as “fruit flies”. “Generally, each
species of orchid has a specific pollinator, but this is a rare case of a
specific group of pollinators,” said the biologist. The researchers also
monitored the behavior of these insects. “The flies move from one sepal to
another for many hours, sucking tiny drops.

The floral
segments are known as sepals, one of the six parts in which the flower of an
orchid is divided. The scientists took some flowers and placed them in a
substance called hexane, which “traps” all the chemical compounds in
the flower. After carrying out an analysis called gas chromatography or
segregated aromas, the experts found in flowers three compounds known as
“tiglatos”, which act as aggregation pheromones.

Aggregation
pheromones are chemicals that insects secrete to attract other individuals of
the same species to the food. For example, an ant that finds sugar produces
these pheromones as to communicate to the other ants that there is food. Thus,
UCR specialists concluded that the Specklinia produce this type of pheromones
in glands called osmforos, located on the outside of the flower. “That is
the ‘trick’ that these flowers use to seduce these insects in particular.

The Drosophila
flies arrive there because they believe that another fly is telling them that
there is food there. It is a novel finding, because there was no known case of
pheromone production of aggregation in orchids. Once they bite the hook, the
flies need an additional incentive to stay for a long time in the orchids. What
is in this case?

The team collected several of the
tiny drops present in the inner part of the flower that the flies suck. After
undergoing a chemical analysis, they determined that they have a high sugar
content; that is, it is a nectar. In addition to sucking that liquid in the
orchid, the flies also participate in courtship and copulation activities.

You could say that
there is a mechanism of deception, because it is the orchid itself that
attracts the fly by means of pheromones. However, there is also a reward,
because the insect finds nectar and therefore remains in the flower for 12
hours or more

Once there, the
plant “makes sure” that the fly takes its pollen. “Inside, these
orchids have a structure in the center called lip or lip, which is a modified
petal. That lip is mobile, then, when the fly rests on it, it is thrown into a
structure called the column that is the reproductive part, where the pollen is continued.
The pollen adheres to a structure in the chest of the fly, called scutellum and
that is how the insect transports them to another flower.

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