Anthony writes:

Though sex determination seems to us to be fixed at conception by chromosomes, that’s far from so in many other species.  Clown fish seen in most any aquarium store use sequential hermaphroditism . And that’s just one of many strategies

There was a mention in TWiEVO 50 of hermaphrodites and self fertilization.  This is not always (usually?) so. Earthworms are hermaphrodites but still require a partner.

Thank you.

Vr: it’s called ‘simultaneous hermaphrodites’. Self-fertilization may or may not occur, Although earthworms possess ovaries and testes, they have a protective mechanism against self-fertilization. Sexual reproduction occurs when two worms meet and exchange gametes, copulating on damp nights during warm seasons.

Anthony writes:

Dear Anthony,

Thank you for your interest in our work. In fish, the mechanisms of sex determination is very labile, and switches quite rapidly. Thus, it is impossible to determine what the ancestral state is in fish. Even in sticklebacks, we see that the sex determination mechanism and sex chromosome differs between closely related species, so we do not know what the ancestral mechanism is in sticklebacks.

I have attached a few papers that might be interesting for you on this topic. Please let me know if you have any other questions!

All the best,

Katie Peichel


Prof. Dr. Catherine (Katie) Peichel

Head of Division, Evolutionary Ecology

Institute of Ecology and Evolution

University of Bern


On 25 Dec 2019, at 15:28, Anthony wrote:

Through Professors Elde and Racaniello’s TWiEvo, I had the good fortune of hearing of your paper

Assembly of a young vertebrate Y chromosome reveals convergent signatures of sex chromosome evolution

Before the evolution of the y chromosome that you describe, is it known / assumed that the method of sex determination was sequential hermaphroditism as in clown fish?  Is there a fish that shares a last common ancestor with the threespine stickleback that uses a method of sex determination other than x – y? If yes, can it be assumed that the ancestor of the sticklebacks used that method?  Or would it be that the ancestor used x-y, sticklebacks changed from that and then the threespined switched back to it?

Thank you.

Anthony Olszewski

Ben writes:

Hi Vincent and Nels,

The anagrams I included in my last email were your names, innocent varicella (Vincent Racaniello) and Cell Needs (Nels C Elde, couldn’t  come up with any good ones without using your middle initial)!

On a completely unrelated note, I would love to hear a discussion/paper on the gain and loss/degeneration of organelles, particularly in protozoans whose diversity of organelles/endosymbionts is truly amazing!

It’s currently a very welcome 25°C in Adelaide, South Australia where consistent days above 40°C have led to terrible bushfires across the country.

All the best for the new year! I can’t wait for another year of what makes us tick!



Courtney writes:

Dear Drs.  Racaniello & Elde,   

Hello from Omaha, Nebraska. It has unfortunately started to snow and is a chilly -5 celsius. 

I am writing in to tell you how excited I am that Dr. Racaniello is including an ecology lecture in his class!  While I consider myself a “biologist”, my background is in ecology and that’s the first thing I think of when I hear the term “biology”. However, I absolutely love molecular biology/ evolution/ behavior/ etc. I have yet to find a subfield that I didn’t wholeheartedly enjoy and want to know more about (maybe computational biology?)  At my school, there is a bit of a division between the molecular biologists and ecologists. A few of the molecular folks look down at ecology and don’t think it’s a worthy field. I think part of it has to do with there are no hard and fast rules in ecology (there is always an exception.) and how hard it can be to control conditions in the field.  

Which, honestly kinda confuses me. Ecology is found at literally every level of biology. Bacteria and viruses compete for space.  Disturbances (like antibiotics) can wipe out bacterial communities in the human body and then be recolonized. The abiotic environment affects what can and cannot live in certain places.  

Anyways, I just wanted to express my joy hearing a molecular person incorporating ecology into their lectures. 

I’d like to share a science pick this week. One of my favorite bands, nightwish, has an album primarily dedicated to evolution/ biology called “Endless Forms Most Beautiful”. Richard Dawkins does some speaking on the tracks. My favorite two  songs from the album are below (with Shudder Before The Beautiful being my all time favorite song). I cried when I saw them perform some of the songs in concert. 

Endless Forms Most Beautiful  

Shudder Before The Beautiful