Question

What is the function of the retrocerebral organ?

Answer 1

Answer:

These organs expel water from the body, helping to maintain osmotic balance

Explanation:

(Rotifera) A small glandular organ, attached to the epidermis above and behind the brain, comprised of the retrocerebral sacand the subcerebral glands; 

Answer 2

Answer:

Close to the brain lies a retrocerebral organ, consisting of two glands either side of a medial sac. ... The function of the retrocerebral organ is unclear. The nervous system comprises about 25% of the roughly 1,000 cells in a rotifer. Rotifers typically possess one or two pairs of short antennae and up to five eyes.

still if you want to know its function you can search in the net or find in the books but I don't think you will get any satisfactory answer as its function is really unclear