Reproductive strategies of a simultaneous hermaphrodite

Straalen, N.M. van [Promotor]Koene, J.M. [Copromotor

Possible origins of macroscopic left-right asymmetry in organisms

I consider the microscopic mechanisms by which a particular left-right (L/R) asymmetry is generated at the organism level from the microscopic handedness of cytoskeletal molecules. In light of a fundamental symmetry principle, the typical pattern-formation mechanisms of diffusion plus regulation cannot implement the "right-hand rule"; at the microscopic level, the cell's cytoskeleton of chiral filaments seems always to be involved, usually in collective states driven by polymerization forces or molecular motors. It seems particularly easy for handedness to emerge in a shear or rotation in the background of an effectively two-dimensional system, such as the cell membrane or a layer of cells, as this requires no pre-existing axis apart from the layer normal. I detail a scenario involving actin/myosin layers in snails and in C. elegans, and also one about the microtubule layer in plant cells. I also survey the other examples that I am aware of, such as the emergence of handedness such as the emergence of handedness in neurons, in eukaryote cell motility, and in non-flagellated bacteria.Comment: 42 pages, 6 figures, resubmitted to J. Stat. Phys. special issue. Major rewrite, rearranged sections/subsections, new Fig 3 + 6, new physics in Sec 2.4 and 3.4.1, added Sec 5 and subsections of Sec

Aging and disease-relevant gene products in the neuronal transcriptome of the great pond snail (Lymnaea stagnalis): a potential model of aging, age-related memory loss, and neurodegenerative diseases

Modelling of human aging, age-related memory loss, and neurodegenerative diseases has developed into a progressive area in invertebrate neuroscience. Gold standard molluscan neuroscience models such as the sea hare (Aplysia californica) and the great pond snail (Lymnaea stagnalis) have proven to be attractive alternatives for studying these processes. Until now, A. californica has been the workhorse due to the enormous set of publicly available transcriptome and genome data. However, with growing sequence data, L. stagnalis has started to catch up with A. californica in this respect. To contribute to this and inspire researchers to use molluscan species for modelling normal biological aging and/or neurodegenerative diseases, we sequenced the whole transcriptome of the central nervous system of L. stagnalis and screened for the evolutionary conserved homolog sequences involved in aging and neurodegenerative/other diseases. Several relevant molecules were identified, including for example gelsolin, presenilin, huntingtin, Parkinson disease protein 7/Protein deglycase DJ-1, and amyloid precursor protein, thus providing a stable genetic background for L. stagnalis in this field. Our study supports the notion that molluscan species are highly suitable for studying molecular, cellular, and circuit mechanisms of the mentioned neurophysiological and neuropathological processes

Receipt of seminal fluid proteins causes reduction of male investment in a simultaneous hermaphrodite

Mating partners often have conflicting interests when copulating [1-3]. One of the major agents affecting female mating partners is seminal fluid, transferred along with sperm. The role of seminal fluid proteins (SFPs) in reproductive success is well studied in separate-sexed animals [4, 5] but is much less so in simultaneous hermaphrodites [6]. The latter potentially have a unique target to exploit for the sperm donor's own benefit: the male function of their mating partners [7, 8]. Here we show that, in the great pond snail Lymnaea stagnalis, receipt of specific SFPs reduces both sperm transfer and paternity success in a subsequent insemination event. Lowering investment in the mating partner's male function constitutes a novel role for SFPs. This demonstrates for the first time that hermaphrodites alter their mates' male as well as female reproductive output [6]. Although it remains to be tested whether this represents mate manipulation or an adaptive response of recipients [9], our findings identify male investment as a new target for postcopulatory sexual selection [10]. © 2014 Elsevier Ltd

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

Contrasting with separate-sexed animals, simultaneous hermaphrodites display unique reproductive strategies as they are male and female at the same time. Simultaneous hermaphrodites that copulate unilaterally, for instance, make a decision to mate as a male or female. Previous studies have demonstrated that sex role preference in hermaphrodites is flexible and is controlled by several, often confounding, factors. We examined the relationship between sex role decisions and 3 life-history traits (age, size, and mating history) in the great pond snail, Lymnaea stagnalis. Based on our field observations, which indicate that adult individuals show overlapping generations and large variation in body size during the breeding season, we performed a sex role choice experiment in the laboratory. We found that young and small snails mate as males first. Both age and size significantly affected sex role decision, with age having a stronger effect. Furthermore, we tested whether L. stagnalis becomes reluctant to inseminate a mate after being inseminated because it is known that after insemination, male investment substantially reduces. Contrary to expectations, our results indicate that the receipt of seminal fluid does not seem to reduce male motivation. In sum, sex role decisions in L. stagnalis are largely determined by age and size but not by having received seminal fluid. This mating pattern, however, does not fully support the size-advantage model because large or old individuals did not perform better as females in our experiment. These results imply a conflicting mating interest, rather than harmonious agreement, between age- and size-different hermaphrodites

Divergence of seminal fluid gene expression and function among natural snail populations.

Nakadera Y, Smith AT, Daupagne L, Coutellec M-A, Koene JM, Ramm SA. Divergence of seminal fluid gene expression and function among natural snail populations. Journal of evolutionary biology. 2020;33(10):1440-1451.Seminal fluid proteins (SFPs) can trigger drastic changes in mating partners, mediating post-mating sexual selection and associated sexual conflict. Also, cross-species comparisons have demonstrated that SFPs evolve rapidly and hint that post-mating sexual selection drives their rapid evolution. In principle, this pattern should be detectable within species as rapid among-population divergence in SFP expression and function. However, given the multiple other factors that could vary among populations, isolating divergence in SFP-mediated effects is not straightforward. Here we attempted to address this gap by combining the power of a common garden design with functional assays involving artificial injection of SFPs in the simultaneously hermaphroditic freshwater snail, Lymnaea stagnalis. We detected among-population divergence in SFP gene expression, suggesting that seminal fluid composition differs among four populations collected in western Europe. Furthermore, by artificially injecting seminal fluid extracted from these field-derived snails into standardized mating partners, we also detected among-population divergence in the strength of post-mating effects induced by seminal fluid. Both egg production and subsequent sperm transfer of partners differed depending on the population origin of seminal fluid, with the response in egg production seemingly closely corresponding to among-population divergence in SFP gene expression. Our results thus lend strong intraspecific support to the notion that SFP expression and function evolve rapidly, and confirm L. stagnalis as an amenable system for studying processes driving SFP evolution. This article is protected by copyright. All rights reserved