Reduced egg laying caused by a male accessory gland product opens the possibility for sexual conflict in a simultaneous hermaphrodite

Abstract

Promiscuity, sperm storage and internal fertilization enhance sperm competition, which leads to sexual confl ict whenever an advantageous trait for sperm donors is harmful to recipients. In separate-sex species, such confl icts can severely impact the evolution of reproductive characteristics, physiology and behaviours. For simultaneous hermaphrodites, the generality of this impact remains unclear and underlying mechanisms remain largely unexplored. In the hermaphrodite Lymnaea stagnalis several previous studies showed that investment in eggs diff ers depending on semen receipt, but these were inconsistent about the direction of change. We investigated whether the change in egg laying is caused by a seminal fl uid component. By intravaginally injecting animals, we here reveal that a component of the seminal fl uid inhibits egg laying, thus providing the fi rst direct evidence for involvement of such components in competition for fertilization in hermaphrodites. We discuss the broad implications that this fi nding has on a number of previous studies performed in the same species. © Koninklijke Brill NV, Leiden, 2009.

Effect of Male Accessory Gland Products on Egg Laying in Gastropod Molluscs

“…The finding that Ovipostatin reduces egg mass production in the recipient corroborates earlier work indicating that substances in the semen may influence egg laying [13][14][15] . By transferring biologically relevant amounts (see 3.…”

“…Although this procedure here is shown using the prostate gland extract, the effect of a single purified seminal fluid protein can also be tested following the same procedure. Obviously, in such tests it is always crucial to include proper controls (sham treatments) to ensure that the procedure and/or the carrier medium do not affect the parameters in questions 14,16 . Using this method, it has already been shown that there is a single seminal fluid protein, namely Ovipostatin, that mediates a reduction in egg laying 14,16 .…”

“…Obviously, in such tests it is always crucial to include proper controls (sham treatments) to ensure that the procedure and/or the carrier medium do not affect the parameters in questions 14,16 . Using this method, it has already been shown that there is a single seminal fluid protein, namely Ovipostatin, that mediates a reduction in egg laying 14,16 . This protein, produced in the prostate gland and transferred during mating along with the spermatozoa, represents the first fully characterized seminal fluid component in a simultaneous hermaphrodite and does, so far, not show any resemblance to known proteins.…”

“…Hence, parameters that need to be quantified in this context -next to laying frequency and egg numbers -include egg size, hatching time, hatchling development and hatchling size. In addition, it is possible to look at effects on other female processes than egg laying, such as sperm storage and usage, as well as the allocation of reproductive resources towards the female and male function 14,17 . Clearly, the presented method is instrumental in addressing these followup issues, both in Lymnaea stagnalis and in other fresh water snails.…”

“…But there are many simultaneous hermaphrodites that transfer male accessory gland products along with their sperm, such as the model species used here, the great pond snail Lymnaea stagnalis. Previous research has already demonstrated that the receipt of seminal fluid influences the female reproductive output of this species [13][14][15] , and several of the involved seminal fluid proteins have been identified 16,17 .…”