Asian Citrus Psyllid Anatomical Discoveries

Ernie NeffPsyllids

Asian citrus psyllid
Male Asian citrus psyllid

Scientists from the University of Granada (UGR) have made the first anatomical atlas of the Asian citrus psyllid (ACP), which spreads HLB.

The research group, led by Professor Susan J. Brown from Kansas State University, conducted a multidisciplinary project to study the psyllid, the bacteria it transmits, its effects and means of control. The U.S. research team approached Javier Alba-Tercedor of UGR’s Department of Zoology to lead the study of the functional anatomy of the insect using microtomographic techniques.

This study forms part of the doctoral thesis of Ignacio Alba-Alejandre (supervised by Alba-Tercedor). A recent article published in the journal Scientific Reports (by Nature) provides a highly detailed vision of both the external and the internal structures of the ACP.

The research team was able to elucidate the operation of different anatomical structures of the ACP. Among the most noteworthy examples are the male sperm pump — an impellent suction pump that serves to expel sperm — and the spermatheca (sac) in which females store sperm.

The complexity of the articulated reproductive organ of males is particularly striking, as is the fact that females have a more voluminous nervous system than males. The latter phenomenon undoubtedly occurs because they have to perform more complex vital functions, such as selecting the ideal location for subsequent egg-laying.

Curiously, the hindgut of the female is posteriorly differentiated into a rectum that forms a small rectal ampulla, into which it deposits small amounts of excrement. By contracting the walls of the ampulla, the feces are violently propelled away from the body, thereby avoiding contact that could contaminate the eggs.

Another interesting discovery to emerge from the analysis carried out at the UGR was that the psyllids have glands at the base of the legs (coxal glands) and others at the base of the antennae (antennal glands) that produce sex pheromones. When the insect settles on the leaves, it impregnates them with the secretions of the coxal glands, which also attract the opposite sex. Once males and females are close to one another, they begin a kind of “dance” in which they touch antennae and, thanks to the secretions of the antennal glands, recognize each other’s sexes.

The research team has been able to reconstruct in 3D — for the first time — an adult feeding on a citrus leaf, showing how its stylets pierce the walls of the leaf to reach the vessels of the phloem and feed by sucking the sap.

Source: University of Granada

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