Successive matings produce opposite patterns on ejaculate volume and spermatozoa number in an ancient arthropod model with indirect sperm transfer

OLIVERO, PAOLA ANDREA; VRECH, DAVID EDUARDO; PERETTI, ALFREDO VICENTE; OVIEDO-DIEGO, MARIELA ANAHÍ

CANADIAN JOURNAL OF ZOOLOGY

NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS

Lugar: Otawa; Año: 2019 vol. 97 p. 579 - 587

0008-4301

The production of spermatophore and ejaculate is energetically expensive for males. High mating rates may accelerate sperm depletion and progressive decrease the size of the ejaculates. Sperm competition can shape spermatozoa numbers according to different signals and clues such as number of potential rivals or female mating status. Factors influencing patterns of sperm allocation have been neglected in terrestrial arthropods that transfer sperm indirectly using a complex sclerotized spermatophore deposited on the soil. We used the Neotropical scorpion, Bothriurus bonariensis (C.L. Koch, 1842), to examine ejaculate volume, spermatozoa numbers and spermatophore`s trunk length along three successive matings and their relationship with male?s body size. Males mated and deposited a preinsemination spermatophore every ten days. Ejaculate volume and trunk length decreased, and spermatozoa number increased over matings. Male body size positively influenced ejaculate volume, and trunk length interacted with mating event. High mating rates may decrease ejaculate volume. Sperm competition may produce increased spermatozoa number. Ejaculates are more energetically expensive than spermatozoa and bigger males may face better the energetic requirements. Bigger spermatophore´s trunks contain greater ejaculate volume in the first two matings, but this relationship disappears at the third mating event. Our discussion focuses on the factors responsible for the patterns observed.