Abstract

Tenebrionid beetles can survive in arid environments, and a key feature underlying their ability to conserve water is the cryptonephridial complex (CNC). It recovers water from the rectal contents and recycles it back to the body. The complex arises from a radical reorganisation of the insect body plan. It comprises two organs found in most insects, the hindgut and renal/Malpighian tubules, which come to lie in counter current arrangement. The renal tubules generate a high ionic concentration to draw water out of the hindgut and return it to the body. It is surrounded by an insulating layer of tissue, the perinephric membrane, which appears to be unique to insect CNCs.

In the Denholm lab we are studying how this organ system develops, including how differentiation of the specialised cells within it is controlled. Here I will talk about the mechanisms by which the distinct tissues generating the CNC are assembled during development. Using Tribolium, we find that sequential crosstalk between the hindgut, renal tubules and perinephric membrane precursor cells, involving multiple Fibroblast Growth Factor (FGF) ligands and receptor isoforms, establishes the counter current configuration and close apposition of the rectum with renal tubules, as well as the recruitment of the perinephric membrane. We also identify that the perinephric membrane develops from a distinct population of mesodermal cells not previously described. This provides an elegant example of FGF signalling orchestrating elaborate morphogenic interactions between three tissues, to generate one of the most powerful water conservation systems in nature.