Writing in the open-access journal BMC Biology, Allyson Whittaker and Paul Sternberg from the California Institute of Technology investigated the role of the excitatory neurotransmitter acetylcholine in regulating tail muscles to achieve an exploratory embrace.

The video shows an intimate moment between two nematodes of the species Caenorhabditis elegans. Because the hermaphrodite does not actively co-operate in mating, it is up to the male to make and maintain the necessary contact. He presses the front side of his tail against the hermaphrodite while he backs along and searches for the vulva. If not found along this first side, the tail makes a sharp turn, curling round the end of the hermaphrodite to continue searching on the other side. On finding the vulva, the male inserts his spicules and mating commences.

Whittaker, A.J. and Sternberg, P.W. (2009) Coordination of opposing sex-specific and core muscle groups regulates male tail posture during Caenorhabditis elegans male mating behavior. BMC Biology, 7