Kora Montagne-Wajer

Male accessory gland protein reduces egg laying in a simultaneous hermaphrodite.

Seminal fluid is an important part of the ejaculate of internally fertilizing animals. This fluid contains substances that nourish and activate sperm for successful fertilization. Additionally, it contains components that influence female physiology to further enhance fertilization success of the sperm donor, possibly beyond the recipients optimum. Although evidence for such substances abounds, few studies have unraveled their identities, and focus has been exclusively on separate-sex species. We present the first detailed study into the seminal fluid composition of a hermaphrodite (Lymnaea stagnalis). Eight novel peptides and proteins were identified from the seminal-fluid-producing prostate gland and tested for effects on oviposition, hatching and consumption. The gene for the protein found to suppress egg mass production, Ovipostatin, was sequenced, thereby providing the first fully-characterized seminal fluid substance in a simultaneous hermaphrodite. Thus, seminal fluid peptides and proteins have evolved and can play a crucial role in sexual selection even when the sexes are combined.

Effects of frequent mating on sex allocation in the simultaneously hermaphroditic great pond snail (Lymnaea stagnalis)

Simultaneous hermaphrodites have the opportunity to control the allocation of resources to the male and female function depending on the circumstances. Such flexibility also provides the possibility to influence sex allocation in the mating partner. To investigate this idea, we measured egg production (female investment) and sperm production as well as prostate gland size (both are part of male investment) under different mating regimes in the great pond snail Lymnaea stagnalis. We find no evidence for the prediction from sex allocation theory that sperm production increases with mating frequency. However, we do find that animals with more mating opporunities develop smaller prostate glands, in which seminal fluid is produced. Moreover, repeated mating increases egg production, thus shifting allocation towards the female function, and probably decreases growth. So, our data hint at a three-way trade-off between part of the male function (prostate gland), female function, and growth. Interestingly, sex allocation seems to be shifted in the opposite direction from the one predicted by theory. We discuss how this feminization is suggestive of a direct manipulation by the sperm donor, probably to stimulate immediate sperm use.

Aspects of body size and mate choice in the simultaneously hermaphroditic pond snail Lymnaea stagnalis.

Body size can be a good indicator of the quality of a potential mate in terms of fecundity. In many hermaphrodites, egg production is positively correlated with body size. Especially when donating sperm is costly, a preference for larger partners might be expected. Here we test this prediction for the great pond snail Lymnaea stagnalis. As expected, we find a clear effect of body size on egg production, and show that shell height can be used as a reliable predictor of body size. Additionally, behavioural observations reveal that these snails are not physically limited in mating with a much larger or smaller partner. Nonetheless, both in a choice experiment as well as in spontaneous copulations, we find no evidence of mate choice based on body size. These results contribute to a growing field of research which attempts to understand the evolution of the wide variation in the ways that hermaphroditic species respond to the size of potential mating partners.

Effects of age, size, and mating history on sex role decision of a simultaneous hermaphrodite

Lay summary Quite a few animals are male and female at the same time, so they can choose to mate either as male or female on copulation. The decision to perform either sex role was known to be highly flexible depending on various, but often confounding, factors. For the pond snail, we report that young and small snails tend to mate as males first, though old and large snails do not seem to be better females.

A syringe-like love dart injects male accessory gland products in a tropical hermaphrodite.

Sexual conflict shapes the evolution of many behaviours and processes involved in reproduction. Nearly all evidence supporting this comes from species where the sexes are separated. However, a substantial proportion of animals and most plants are hermaphroditic, and theoretical work predicts that sexual conflict plays an important role even when the sexes are joined within one individual. This seems to have resulted in bizarre mating systems, sophisticated sperm packaging and complex reproductive morphologies. By far the best-known example of such a strategy in hermaphrodites is the shooting of so-called love-darts in land snails. All known love darts carry a gland product on their outside and enter this into the partner’s hemolymph by stabbing. Here, we show that species of the snail genus Everettia possess a syringe-like dart that serves as a real injection needle. Their dart is round in cross-section, contains numerous channels, and has perforations along its side. Histology and electron microscopy show that these holes connect to the channels inside the dart and run all the way up to the elaborate mucus glands that are attached to the dart sac. This is the first report on a love dart that is used as a syringe to directly inject the gland product into the partner’s hemolymph. Although the exact use and function of this dart remains to be demonstrated, this clearly adds to the complexity of the evolution of reproductive strategies in hermaphrodites in general. Moreover, the perforations on the outside of the love dart resemble features of other injection devices, thus uncovering common design and repeated evolution of such features in animals.

Cutaneous application of an accessory-gland secretion after sperm exchange in a terrestrial slug (Mollusca : Pulmonata)

Competition for fertilisation in hermaphroditic animals seems to have led to many odd behaviours and complex morphologies involved in the transfer of accessory-gland products to the partner. Terrestrial slugs of the genus Deroceras show remarkably elaborate and interspecifically diverse penis morphologies and mating behaviours. Most species have an appending penial gland, which in Deroceras panormitanum consists of a few long fingers that are everted after sperm exchange and laid onto the partners back. To investigate whether this gland transfers a secretion onto the partners skin, we killed slugs at different mating stages and studied their penial glands and skin histologically. Two types of secretion granules appeared at a very early stage of courtship, and the penial gland was already filled 15min into the courtship. At copulation, the gland everted this secretion onto the partners body, where it remained for at least 50min. No lysis of skin tissue or other effects on the skin were observed. The slugs tried to lick the received secretion off their own body, and some droplets were observed to be shed with the body mucus. Our results indicate the external application of a glandular substance that could function as either a pheromone or allohormone. The behaviours of the recipients suggest sexual conflict, although mutual interest cannot be ruled out.

Mechanisms of phenanthrene toxicity in the soil invertebrate, Enchytraeus crypticus

Polycyclic aromatic hydrocarbons (PAHs) continue to cause environmental challenges as a result of their release into the environment by a great variety of anthropogenic activities and their accumulation in soils. Studies were conducted on the toxicological effect of the model PAH phenanthrene using the soil invertebrate model Enchytraeus crypticus at the individual, tissue, and molecular levels. Animals were exposed for 2 d and 21 d to phenanthrene concentrations corresponding to the (previously estimated) 3-wk effective concentration, 10% (EC10) and EC50 for effects on reproduction. Gene expression profiling did not reveal a typical phenanthrene-induced biotransformation signature, as it usually does in arthropods and vertebrates. Instead, after 2 d of exposure, only general metabolic processes were affected, such as translation and adenosine triphosphate synthesis-coupled electron transport. Histological sections of tissues of 2-d exposed animals showed no deviations from control. In contrast, after prolonged exposure of up to 21 d, histopathological effects were found: chloragogenous cells were highly vacuolated and hypertrophic. This was corroborated by differential expression of genes related to immune response and oxidative stress at the transcriptomic level. The data exemplify the complexity and species-specific features of PAH toxicity among soil invertebrate communities, which restricts read-across and extrapolation in the context of soil ecological risk assessment. Environ Toxicol Chem 2016;35:2713-2720.