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Schärer Group
Evolutionary Biology
Zoological Institute
University of Basel
Vesalgasse 1
CH-4051 Basel
Switzerland

Philipp Kaufmann

email: philipp.kaufmann-at-stud.unibas.ch
phone: +41 61 207 03 76

I am mainly interested in evolutionary processes and the genetic structures they are based on. As a MSc student in the Schärer research group I want to learn more about the sexual conflict between male and female and how they interact with each other. In this regard, the hermaphroditic Macrostomum flatworms are fascinating, since one can observe the male and female interests simultaneously in the same individual.

Current research

In my masters project I am focusing on mating strategies of the free-living flatworm Macrostomum hystrix. These simultaneously hermaphroditic worms reproduce by injecting sperm and seminal fluids hypodermically into either a mating partner (during outcrossing) or into their own tissues (during self-fertilization). It has been suggested that hypodermic insemination, which likely evolved due to sexual conflicts over the preferred mating role during outcrossing, may have enabled the evolution of self-fertilization.The simultaneous presence of outcrossing and self-fertilization makes M. hystrix an interesting organism to study the reproductive decisions of focal worms depending on their social environment, which is the main aim of my project.

To explore this, I will manipulate the social environment of focal worms by mechanically removing the stylets (sclerotized male genitalia) of potential partner worms and thus disrupting their ability to donate sperm to the focal worm (these partners will be further referred to as amputated partner). In particular, focal worms will be assigned to three treatments where they experience different social environments (Figure 1). Focals of the positive control are kept isolated. Given these conditions without access to sperm of a mating partner (allosperm), focals of this group are expected to initialize self-fertilization, using their own sperm (autosperm) on themselves. In contrast, focals of the negative control are put together with a mature partner, labeled with a dye. Here the focals are expected to mate with the partner. Outcrossing has been shown earlier to be the preferred mating strategy. In the manipulated treatment, focals are put together with a dyed amputated partner. Consequently, focals of the manipulated treatment can interact with a potential mating partner, however, they will have no access to allosperm. At the end of the experiment, sperm will be scored in the focal worms of all three treatment groups via microscopy. Based on the spatial distribution pattern of sperm in the tissue of the focal worms, one can distinguish allosperm from autosperm and thereby between self-fertilization and outcrossing.

In order to maintain the manipulated state of the amputated partners over the course of this experiment, the partners will regularly be replaced. In a preliminary experiment we examined the regenerative capabilities of M. hystrix and could show that M. hystrix can regenerate its amputated tail plate within four days.

Figure 1: Illustration of the ongoing experiment, exploring the reproductive strategies of Macrostomum hystrix under different social conditions. Hatchlings (focals) of the same age are randomly assigned to three groups, where they experience different social environments. Focal worms of the manipulated treatment and the negative control will get a new partner every three days, in order to ensure the blue colour of the partner and the absence of the stylet in the amputated partners. The positive control will be regularly monitored for hatchlings as an estimation of the reproductive activity. Upon a certain threshold of reproductive activity all focals will be scored for sperm.

Publications

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this page was last updated on Tuesday, May 30, 2017