I offer projects using nematode worms which make for great student projects as they grow fast, cross easily and are easy to keep. They benefit from the availability of various resources (wormbase.org, wormbook.org, strain collections, genomes and transcriptomes).
Depending on the project, you will gain experience in experimental design, worm maintenance, aseptic technique, PCR, microscopy, statistical analysis in R, as well as writing / presentation skills and maintaining a lab book.
I am interested in the interplay between sexual selection, environmental adaptation and sex chromosome evolution. Below are some possible projects but feel free to contact me to discuss your ideas.
Depending on the project, you will gain experience in experimental design, worm maintenance, aseptic technique, PCR, microscopy, statistical analysis in R, as well as writing / presentation skills and maintaining a lab book.
I am interested in the interplay between sexual selection, environmental adaptation and sex chromosome evolution. Below are some possible projects but feel free to contact me to discuss your ideas.
Identifying traits that differ between sexes
Worms have a plastic response to salt which depends on their experience. Adult worms seek the salt concentration they grew happily in and avoid the salt concentration in which they were starved or stressed while they were growing up. We have replicated this literature result for NaCl chemotaxis of C. elegans, and extended the results to males and other species.
Example result showing worms grown at high salt will seek high salt as adults (positive y axis values), while worms grown at low salt will seek low salt as adults (negative y axis values). The result is similar in females/hermaphrodites of 3 species (C. brenneri, C. remanei, C. elegans).
Contrasting females (top) and males (bottom) shows that there is a subtle (but statistically significant) difference. The males show a more extreme response during the same observation time.
Possible future directions:
- Further explore within-species strain and sex differences.
- Test for similar responses to other stimuli such as other salts, alcohol, glycerol, temperature.
- Investigate the effect of additional prior stress (such as temperature) to the worm response speed and intensity.
- Investigate the variability of the response.
- Investigate the timing of the response.
Experimental selection for salt preference and salt adaptation
We are interested in whether there is a genetic predisposition for a particular salt preference, on top of the well-known plasticity in developing a salt concentration preference (see above).
To do this we grew worms long-term on different salt concentrations (experimental evolution). We then grew them for one generation in normal salt and checked whether they had a preference for the salt concentration of their evolved condition or the condition they grew up in.
They preferred their ancestral salt condition, suggesting there is also a genetic predisposition for preference.
To do this we grew worms long-term on different salt concentrations (experimental evolution). We then grew them for one generation in normal salt and checked whether they had a preference for the salt concentration of their evolved condition or the condition they grew up in.
They preferred their ancestral salt condition, suggesting there is also a genetic predisposition for preference.
Example result showing the offspring of worms evolving in high salt will seek it as adults (positive y axis values) even if themselves were grown at normal salt. The result is also as expected for worms grown in low salt. While the results are in the expected direction, the only statistically significant difference is for the offspring of the worms that evolved under low salt.
Possible future directions:
- Investigate whether the result is due to cross-generation (epigenetic) inheritance, or genetic adaptation.
- Attempt to break covariation for preference in males and females, by selecting each sex for a different environment.
- Directly select for salt preference instead of salt adaptation, and contrast result with salt adaptation.
Characterisation of reproductive isolation within and between species
We crossed populations after evolving for 6 generations on high or low salt. Fewer offspring were produced in the crosses between salt conditions (hh, ll) than within salt conditions (hl, lh; but significant at 10% level only). This points to the possibility of environmental adaptation leading to reproductive isolation.
This result can be followed up:
- More generations of selection, and comparison with selection for preference instead of for salt adaptation
- Other assays of reproductive isolation (female choice, male attraction to females, offspring longevity, parent longevity in environment not evolved…)
We may have produced viable offspring in a C. remanei x C. brenneri cross, which is opposite to expectation from the literature.
In this gel F1 offspring from the cross in lanes 1,3,4,5 show two PCR bands. The parental species have one band each.
- This result needs to be confirmed with independent replication and by using more strains.
The most successful inter-specific hybrids are from a cross between C. nigoni (dioecious) and C. briggsae (androdioecious). This cross can be used to study the genetics of reproductive isolation (speciation), but also the transition between sexual systems (from hermaphrodites to separate sexes).
It is already known that Haldane's rule holds (the male hybrids suffer more than the female hybrids), and that the large X effect holds (the X has a disproportionate effect on reproductive isolation).
Possible future directions:
It is already known that Haldane's rule holds (the male hybrids suffer more than the female hybrids), and that the large X effect holds (the X has a disproportionate effect on reproductive isolation).
Possible future directions:
- We can characterise the extent of reproductive isolation in this cross using multiple strains of the two species, to identify strains that are more compatible than others.
- We can develop molecular markers that allow to follow introgression of different chromosomes from the two species.
Please check out the posters and theses of previous students to get a better idea of what a project looks like.
Click on the icons below the project title to see the poster or thesis of previous students.
