Unexpected attraction of Urostreptus sp. (Spirostreptidae) to seed elaiosomes: a new resource record to millipedes’ diet

Abstract

We describe, for the first time, the attraction of an unidentified millipede species (Urostreptus sp.) to an elaiosomes of a Euphorbiaceae species (Jatropha mutabilis (Pohl) Baill.). After field observations of Urostreptus specimens feeding on elaiosomes’ seeds of J. mutabilis in areas of Caatinga in Petrolina, northeast Brazil, we conducted experiments to test the hypothesis that this millipede is specifically attracted to J. mutabilis elaiosomes. In the first experiment, millipedes were offered a choice between pairs of seeds with and without elaiosomes. In each trial we recorded the animal choice and the time required to access the seed. In the second experiment, millipedes were offered a choice between pairs of pebbles similar in size to the seeds, one of which was soaked in elaiosome extract. The results showed that millipedes significantly preferred seeds with elaiosomes and were all attracted to pebbles soaked in the elaiosome extract. We also speculate some of the potential implications for seed dispersal and seedlings distribution. Keywords: Brazil; Caatinga; Diplopoda; elaiosome-bearing seed; Euphorbiaceae.