Spermiophagic activity in the female genital system of some species of terrestrial isopods (Crustacea, Halophilosciidae)

• Halophilosciidae present a peculiar pattern of female genital system.
• Females of Halophilosciidae receive during mating a great quantity of sperm.
• During their storage in the ovary, the sperm tails undergo a process of digestion.
• The mechanisms underlying the spermiophagic activity are unclear.

The females of some species of the family Halophilosciidae receive in the course of mating a quantity of sperm considerably redundant with respect to the number of eggs that can be fertilized; this is possible thanks to the peculiar morpho-functional organization that characterizes their genital system and that allows them to store the sperm not only in the great seminal receptacle but also within the ovary. While most of the sperm stay free in the lumen of the seminal receptacle, a part of those present in the ovary undergoes a process of capture by the follicular cells with consequent internalization within endocellular cavities. This process concerns exclusively the immotile tail, that characterizes the peculiar spermatozoon of the isopods and which is essentially of proteic nature. After their capture the sperm tails undergo a gradual process of digestion, which seems to be apparently realized without the intervention of lysosomes. The possible role of this spermiophagic activity might be to represent a significant trophic paternal investment aimed at improving the fitness of the female and of the offsprings.