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I blog about research articles in sex and reproduction. Topics range from molecular interactions during sex to sexual behaviors of different animals (or plants!).
As they age, hermaphrodite worms run out of sperm. Males can somehow sense this and find these older, sperm-depleted hermaphrodites to be very sexy indeed.... Read more »
Morsci, N., Haas, L., & Barr, M. (2011) Sperm Status Regulates Sexual Attraction in Caenorhabditis elegans. Genetics. DOI: 10.1534/genetics.111.133603
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The largest group of cichlid species is the haplochromine cichlids (roughly 1500 species). A feature of many haplochromines are the colorful “egg spots” on the anal fin of males. Tons of studies have been done trying to pin down exactly what these spots are used for. Some studies have suggested that females prefer males with more egg spots, for various potential reasons, but this is still an unsettled issue.
Now, a paper by Anya Theis, Walter Salzburger, and Bernd Egger from the Unviersity of Basel (published this month in PLoS One) argues that egg spots can be used for male-male competition. The jist: the fewer egg spots a male has, the more likely it is he’s going to be attacked by other males.... Read more »
Theis, A., Salzburger, W., & Egger, B. (2012) The Function of Anal Fin Egg-Spots in the Cichlid Fish Astatotilapia burtoni. PLoS ONE, 7(1). DOI: 10.1371/journal.pone.0029878
Did you know that diatoms have sex? I didn’t. ... Read more »
Sato, S., Beakes, G., Idei, M., Nagumo, T., & Mann, D. (2011) Novel Sex Cells and Evidence for Sex Pheromones in Diatoms. PLoS ONE, 6(10). DOI: 10.1371/journal.pone.0026923
Female frogs (Xenopus laevis) release their eggs out into the water, where they wait for some lucky sperm to come along and fertilize them. But they don't wait very long. Frog eggs are ticking time bombs that self-destruct after only a few hours if not fertilized. Previously, how this happened was a mystery. Now, new research from Kobe University and (in a separate paper) CNRS in France has found that the eggs die by a well-known mechanism: programmed cell death.... Read more »
Tokmakov, A., Iguchi, S., Iwasaki, T., & Fukami, Y. (2011) Unfertilized frog eggs die by apoptosis following meiotic exit. BMC Cell Biology, 12(1), 56. DOI: 10.1186/1471-2121-12-56
Du Pasquier, D., Dupré, A., & Jessus, C. (2011) Unfertilized Xenopus Eggs Die by Bad-Dependent Apoptosis under the Control of Cdk1 and JNK. PLoS ONE, 6(8). DOI: 10.1371/journal.pone.0023672
Okay, I’ll admit it: I’m using this paper as an excuse to post pymy hippopotamus pictures. They’re so cute! But, besides the cuteness of miniature hippos, the science in this paper is also really cool. Joseph Saragusty and colleagues at the Leibniz Institute for Zoo and Wildlife Research, along with Tim Bouts of the Zoological Society of London discovered that male pygmy hippos can control the ratio of female-to-male offspring they father. The paper was published in the February 28 issue of Nature Communications.... Read more »
Saragusty, J., Hermes, R., Hofer, H., Bouts, T., Göritz, F., & Hildebrandt, T. (2012) Male pygmy hippopotamus influence offspring sex ratio. Nature Communications, 697. DOI: 10.1038/ncomms1700
Male fiddler crabs wave their giant claws to get the attention of females. Females prefer males that wave a lot, in line with a common theme in female choice: making the male work for it. Waving that big thing around is more than just an advertisement. The thing is heavy to lift, so the male has to be in good shape to keep up all that waving. It’s also dangerous. The more he waves that big sign saying, “Hey, look at me!” the more predators will take notice.
How do males determine how often to wave if too much waving will get them dead, and too little will keep them from getting mates?... Read more »
Milner, R., Jennions, M., & Backwell, P. (2011) Keeping up appearances: male fiddler crabs wave faster in a crowd. Biology Letters. DOI: 10.1098/rsbl.2011.0926
Each of us has over 3 billion base pairs of DNA in every one of our cells. And every time a cell divides, there is a risk of making a critical mistake in a few bases that can eventually lead to cancer. That’s why our cells have lots of fail-safes to make sure that we don’t turn into one big tumor by the time we hit puberty. Damaged DNA triggers a response by the gene p53, known as the “guardian of the cell” by some. If p53 decides the damage is too great, it orders the death of the cell, and cancer is averted. But when p53 itself is damaged, this often leads to (or encourages growth of) cancer.
What does this have to do with sex? Research from Haifin Lin’s lab at Yale University has shown that another gene, Pumilio 1, keeps p53 in check in the testes. When Pumilio is deleted in the mouse, p53 goes crazy and starts sending helpless little sperm cells to their deaths, causing fertility defects and shrunken testes. The research was published this week in the journal Current Biology.... Read more »
Chen, D., Zheng, W., Lin, A., Uyhazi, K., Zhao, H., & Lin, H. (2012) Pumilio 1 Suppresses Multiple Activators of p53 to Safeguard Spermatogenesis. Current Biology. DOI: 10.1016/j.cub.2012.01.039
Males of many species “guard” females after they’ve mated, presumably to prevent them from mating with other males. But in the cricket Gryllus campestris, males have a more noble intent when they guard their mate: to save her from being eaten.... Read more »
Rodríguez-Muñoz, R., Bretman, A., & Tregenza, T. (2011) Guarding Males Protect Females from Predation in a Wild Insect. Current Biology. DOI: 10.1016/j.cub.2011.08.053
I recently read this paper about fig wasps. The paper by Hui Yu and Stephen G. Compton was published in PLoS One. But it’s more than just a scientific paper. It’s a love story: fig and wasp, destined to be together and mutually dependent on each other for continued survival. It’s also about the love of a mother for her sons. And every love story has its tragedy. In this case, it’s the free-loading enemy wasps that kill the love-children of the wasp/fig romance and force the wasp mother to choose which children to protect.... Read more »
Yu, H., & Compton, S. (2012) Moving Your Sons to Safety: Galls Containing Male Fig Wasps Expand into the Centre of Figs, Away From Enemies. PLoS ONE, 7(1). DOI: 10.1371/journal.pone.0030833
I recently wrote about a paper describing a protease in worm seminal fluid that helps activate male sperm in a species with males and hermaphrodites. Now, another group has published a (sort of) follow-up. They found a protease inhibitor that blocks the protease found in the first paper (Try-5), but in a different species of worm. They also show that it has two roles: one in turning sperm on, the other in turning them off. The research was published ahead of print in PNAS January 31, 2012.... Read more »
Zhao, Y., Sun, W., Zhang, P., Chi, H., Zhang, M., Song, C., Ma, X., Shang, Y., Wang, B., Hu, Y.... (2012) Nematode sperm maturation triggered by protease involves sperm-secreted serine protease inhibitor (Serpin). Proceedings of the National Academy of Sciences, 109(5), 1542-1547. DOI: 10.1073/pnas.1109912109
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Wolbachia are a type of bacteria that live inside the cells of many animals, but mostly insects. They are passed on from mother to child through the mother’s eggs.
They can often be bad for the insect host: they might kill all male offspring, destroy the host’s gonads, or make it harder for the host female to make eggs with sub-par blood. This is why Wolbachia has been pursued as a potential tool for reducing mosquito populations that carry dangerous human pathogens like Dengue virus and malaria.
On the other hand, Wolbachia can be a good thing for the host. In some species, Wolbachia infection can protect the host from viral infections. And, as a new paper in the journal Science demonstrates, they can ramp up the host female’s egg production by increasing the activity of the germline stem cells.... Read more »
Fast, E., Toomey, M., Panaram, K., Desjardins, D., Kolaczyk, E., & Frydman, H. (2011) Wolbachia Enhance Drosophila Stem Cell Proliferation and Target the Germline Stem Cell Niche. Science, 334(6058), 990-992. DOI: 10.1126/science.1209609
More often than you might expect, new genes become male-specific and play important roles in male fertility. These genes get fast-tracked, becoming quickly “fixed” in the population because of the advantage they give to the boys in that age-old competition: who can make the most babies. New research into a group of newly evolved sperm genes in Drosophila melanogaster shows just how quickly new genes can become indispensable. The research was published last week in Proceedings of the National Academy of Sciences.... Read more »
Yeh, S., Do, T., Chan, C., Cordova, A., Carranza, F., Yamamoto, E., Abbassi, M., Gandasetiawan, K., Librado, P., Damia, E.... (2012) Functional evidence that a recently evolved Drosophila sperm-specific gene boosts sperm competition. Proceedings of the National Academy of Sciences, 109(6), 2043-2048. DOI: 10.1073/pnas.1121327109
If you’ve perused the other posts on this site, you may have noticed that I have a thing for seminal fluid. That’s because semen is awesome: it’s full of proteins, lipids, sugars, and who knows what else, all of which plays some role in fertility.
Exactly what all that stuff is doing is still a total mystery (except for a very few rare cases).
Unfortunately, just picking out one protein and asking, “what happens if I break this?” doesn’t seem to work in most cases. One reason for this could be that there are tons of fail-safes built in. After all, if destroying the function of any one protein could cause infertility, making babies would be a lot more difficult.
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Smith, J., & Stanfield, G. (2011) TRY-5 Is a Sperm-Activating Protease in Caenorhabditis elegans Seminal Fluid. PLoS Genetics, 7(11). DOI: 10.1371/journal.pgen.1002375
Well, hello again imaginary reader of this blog. I'm ready to dust this site off and finally start adding some new posts, after a long hiatus. Since the last post, I've written my doctoral dissertation, and will be defending it in just 2 days!
I've also gotten engaged, which is why I was so interested in this article: "The Puzzle of Monogamous Marriage", written by researchers at the University of British Columbia. The authors provide evidence from many studies of human societies arguing that monogamy is good for society. One of the basic tenets of this argument is that when polygyny (having many wives) is the norm in a society, rich and powerful men end up with proportionally more wives...... Read more »
In some plants, multiple gametophytes can develop in a single ovule and compete for the chance to be fertilized. This may have been an ancient strategy in plants to ensure the most fit eggs were used to make seeds, but it was lost in most plant species that survive today. ... Read more »
Bachelier, J., & Friedman, W. (2011) Female gamete competition in an ancient angiosperm lineage. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.1104697108
Are you grossed out by blue cheese? (I’m not, but I know many who are). Does that blue-green marbling of delicious fungus kind of make you gag? Well, this little factoid probably won’t help: there may be sex going on in that cheese.
Until pretty recently, a big chunk of fungal species were thought to reproduce without sex–until people really started to look. It turns out, there’s a lot more sex going on in the fungal world (on the down-low) than people thought. And that includes fungi that are used to make delicious blue cheese. Jeanne Ropars and colleagues in France, the home of Roquefort cheese, looked at the genomes of the mold species used in this particular cheese to see what kind of funny business was going on in their snack of choice. They found much more diversity than could be explained by asexual reproduction. And even more telling, the genes used by fungi to find mating partners have been kept intact and functional by evolution, meaning there’s probably some sex going on. The results were published November 21 in the online journal PLoS One.... Read more »
Ropars J, Dupont J, Fontanillas E, Rodríguez de la Vega RC, Malagnac F, Coton M, Giraud T, & López-Villavicencio M. (2012) Sex in Cheese: Evidence for Sexuality in the Fungus Penicillium roqueforti. PloS one, 7(11). PMID: 23185400
The maternal-only transmission of mitochondria has long been a mystery. It’s a now you see it, now you don’t situation: the sperm’s mitochondria go into the fertilized egg, but they disappear within minutes. Now, a paper published in the journal Science has found the answer. Machinery within the egg literally eats up the sperm’s mitochondria through a process called autophagy.... Read more »
Al Rawi S, Louvet-Vallée S, Djeddi A, Sachse M, Culetto E, Hajjar C, Boyd L, Legouis R, & Galy V. (2011) Postfertilization Autophagy of Sperm Organelles Prevents Paternal Mitochondrial DNA Transmission. Science (New York, N.Y.). PMID: 22033522
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