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Newly Discovered Planthopper Appendage Doesn’t Fit the Bauplan

Although the world of insects is incredibly diverse, there are some morphological characteristics that all adult winged insects have shared in common for hundreds of millions of years. For example, all of them have five-segmented heads, three-segmented thoraxes with three pairs of legs, and 11-segmented abdomens.

Any appendages that appear on their abdomens have been found to have something to do with copulation … until very recently.

For the first time ever, scientists from Germany and Israel have found an appendage on planthoppers in the Bennini tribe that has nothing to do with copulation or reproduction — instead, it appears to be some kind of sensory organ. Known as LASSOs (lateral abdominal sensory and secretory organs), the appendages are the same on both male and female planthoppers across more than 125 different species. They are described in an article in the journal Current Biology.

“The appendages, termed LASSO (lateral abdominal sensory and secretory organs), are consistent in topology and structure in all species studied and are not sexually dimorphic,” the authors wrote. “The existence of these non-sexual abdominal appendages reveals the potential of the 300 million year old conserved bauplan of insects.”

“The Bennini sensory organ is astounding because it represents a real evolutionary novelty,” said Dr. Hannelore Hoch, senior author. “It is neither homologous to any structure in a related taxon, nor is it a serial homologue to a structure in the same organisms. It’s also amazing that the appendages are uniform across all 125 species known and are not sexually dimorphic. This sort of excludes the notion that sexual selection is responsible for their evolution. In other words, a selection pressure other than sexual is involved.”

The following video shows an animated 3D-reconstruction of the the LASSO of a male planthopper from Vietnam:

“This is astounding because since the Lower Devonian, there have been no abdominal appendages on insects other than those used for a sexual function,” said Dr. Phyllis Weintraub, another one of the co-authors. “The planthoppers in the Bennini tribe have appendages on their second abdominal segments that are clearly not used for copulation.”

The researchers are still not exactly sure what the LASSOs do. Planthoppers in the Bennini tribe have never been studied in their natural environment — most of what is known about them comes from dried museum specimens. However, according to the authors, it “is conceivable that the LASSO might be an enemy-detection device.”

“My wild hypothesis is that LASSOs perceive signals from small predators or parasitoids, perhaps via the electrostatics these small insects produce during flight,” said Dr. Hoch. “However, this is entirely unknown. I am planning to study their behavior and potential interactions with other organisms in the field, and have chosen Borneo to be a suitable place.”

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Non-sexual abdominal appendages in adult insects challenge a 300 million year old bauplan

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