TIL about unisexual mole salamanders which are an all-woman intricate of salamanders that ‘steal’ sperm from up to 5 diverse species of salamanders in the genus Ambystoma and recombine it to deliver feminine hybrid offspring. This approach of replica is termed kleptogenesis.

TIL about unisexual mole salamanders which are an all-female intricate of salamanders that ‘steal’ sperm from up to five unique species of salamanders in the genus Ambystoma and recombine it to deliver feminine hybrid offspring. This strategy of replica is identified as kleptogenesis.

See Reddit by Mourning_GeckoPerspective Supply

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The mourning geckos of my user name use parthenogenesis to reproduce. I thought that was crazy enough but kleptogenesis is blowing my mind.

They can also just use the stolen sperm to stimulate the production of fertile (but unfertilized) eggs, producing genetically cloned offspring.

[Here]( is a slightly easier to read but less thorough write up of what these salamanders do.

“Out here stealing sperm from different species of men with the girlies. Just Friday night things”

I’m quite surprised that this method of reproduction can support the continued existence of a species at all!

I don’t really understand. If they’re crossing with another species, how do they still exist? Cloning? Also, if they can all produce fertile offspring, how are they all considered distinct species?

There’s an episode of Star Trek Voyager that has a race of females who steal males from other species to mate

Sex and gender get *really* complicated when you look at them closer across the tree of life.

As mentioned in the article, many animals can exist as all-female populations that reproduce by essentially cloning themselves through a process called parthenogenesis. A great way to grow your population quickly, but it leaves them vulnerable to outside threats because of the resulting low genetic diversity.

Honeybees reproduce where all fertilized eggs are female, and males come from unfertilized eggs.

Many reptiles don’t determine sex by genes at all, but rely on environmental factors like temperature.

Some mammals have ZW sex chromosomes, where the males are ZZ and the females are ZW, the opposite of humans where males are XY and females are XX.

Many invertebrates are hermaphrodites and can reproduce in either a male or female fashion (or sometimes both at once)

Some animals including certain fish go through sequential hermaphroditism, all being born one sex, and transitioning to the other in response to certain conditions (age, availability of food or mates, being the dominant member of the group, etc.)

I could go on. Nature is a lot weirder than most people give it credit for.

I am a PhD student currently studying this genetic system on Pelee Island. The Unisexual Ambystoma complex takes everything you thought you understood about genetics and tells you “No, that is not the way”.

A brief: This system consists of an almost exclusively female monophyletic lineage of nuclear genetic hybrid salamanders that are obligative sexual parasites of five known sexual species, and reproduce via ‘kleptogenesis’ living in multiploidy assemblages.


1. ALMOST all female: The deeper you get in the literature you will occasionally find (~1%) unisexuals that are male based on the presence of testes rather than ovaries. It is unclear how this happens, though I suspect it has to do with the reproductive outcomes (see below). For instance, if you come across the [2003 COSEWIC report]( on the laterale-texanum system on Pelee Island where some individuals are marked as male unisexuals. From direct contact with Jim Bogart on this, the males appear to be sterile.
2. Monophyletic lineage: This is based on their mtDNA (CYT-b) which is passed down via the female. Best estimate is that the unisexual lineage originated ~5 MYA ([Bi and Bogart, 2010]( making it the oldest known unisexual group of animals alive today.
3. Nuclear genetic hybrids: Every animal in this system has nuclear DNA from at least two different species, one of which is always *A. laterale* (reason unknown, it just is). To differentiate between animals we give them designations called “genomotypes”, different from a genotype. A genomotype is based on the origin of, and dosage amount, of chromosome sets. For instance an LTT has one set of chromosomes from *A. laterale* (L) and two sets from *A. texanum* (T).
4. Obligative sexual parasites: As they are practically all females, they require sperm for egg development, thus they REQUIRE a viable sexual host species to use sperm from.
5. Five known host species (genomotype code provided in brackets):
1. *A. laterale* (LL) – Blue-spotted salamander
2. *A. texanum* (TT) *-* Small-mouth salamander
3. *A. tigrinum* (TiTi) – Tiger salamander
4. *A. jeffersonianum* (JJ) – Jefferson salamander
5. *A. barbouri* (BB) – Streamside salamander
6. *A. maculatum* (MM) – Spotted salamander <- not actually considered a viable host, but I recall finding a paper or two where it seems to have been successfully used in lab crosses.
6. ‘Kleptogenesis’: A completely unique reproductive mode with 3 known offspring outcomes and one hypothesized outcome.
1. Clonality – sperm comes to the egg, activating egg development but chromosomes are not incorporated resulting in a genetic clone (This is akin to gynogensis)
2. Ploidy elevation – sperm hits egg AND sperm genome gets incorporated producing a ploidy elevated offspring (e.g. LT female takes sperm from TT , *A. texanum*, and produces an LTT offspring)
3. Genome replacement – in some cases, one set of chromosomes is completely replaced by the incoming set from the sperm. For instance an LLJ female uses J sperm producing an LJJ offspring ([Bogart 2019]( This and ploidy elevation have increased rates in higher temperatures ([Licht and Bogart, 1989]( (This is most similar to hybridogenesis)
4. HYPOTHESIZED ROUTE: In cases where an individual is a symmetrical tetraploid (e.g. LLTT, two L sets and two T sets) meiosis can go to full completion producing diploid (LT) offspring. I repeat, this is hypothetical – though given my current data it is the best explanation for the diversity seen on Pelee IMO.
7. Multiploidy assemblages: You may have already guessed it from above, but unisexual females can be of multiple ploidy levels: diploid (2N), triploid (3N), tetraploid (4N), and rare cases of pentaploids (5N). In addition, they can be multi-hybrids, such as trihybrids (LTJ) or tetrahybrid (LTJTi) ([Bogart 2019b](

A few other fun bits:

Different genomotypes appear to have different niches ([Greenwald et al., 2016]( which may be based on genome dosage effects (i.e. an LTT will have a more *texanum*-like niche while an LLT will have a more *laterale*-like niche). This follows given that gene expression generally follows genome dosage ([McElroy et al., 2017](

In a weird turn of events, intergenomic crossover and even translocation can happen. This means that say, an L-1 (chromosome 1 from *laterale*) can crossover with T-1 (chr 1 from *texanum*) producing a chimeric chromosome 1 that is part L and part T ([Bi et al., 2007]( These crossovers can even be tracked across sites!

Because Ambystoma have among the largest known genomes (10x the size of a human’s) unisexual Ambystoma cells vary in size in relation to ploidy level (number of full chromosome sets). This used to be the way that ploidy was determined! And because salamander blood cells are nucleated, this also impacted their blood cell size. Despite their cell sizes increasing, unisexuals don’t increase in size proportionally. So a diploid unisexual will have more cells compared to a tetraploid unisexual of the same size.

Higher ploidy animals suffer from slower cell communication which can make them slower to arrive at the breeding pond ([Lowcock, 1993]( Among other ecological impacts from polyploidy. Despite this, unisexual assemblages tend to be triploid dominated rather than diploid dominant.

Where present, unisexuals typically are the MAJORITY of Ambystoma in the community, and might become so prevalent as to lead to the local extinction of their sperm donor hosts ([Bogart et al., 2016](, this is sometimes referred to as the “Clanton effect”. In the system I study, unisexuals make up between 85%-99.5% of local Ambystoma assemblages.

Shameless plug – here’s a [video]( I made for a conference last year going into some of my work.

And this is just what I could get down in about 45 minutes of writing…

Edits: Slightly more detail for kleptogenesis. Gene expression study added. Ploidy dominance. “Clanton effect”. Minor grammatical/spelling edits.

tl;dr – Unisexual salamanders are the true Amazonians – steal sperm, incorporate genetics, maaaaybe kill off their sex partners.

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