Field of Science

Ciliate orgies and barnacles with twin penises

ResearchBlogging.orgLike any other human beings on the planet, scientists too are enamoured with sex and genitalia. After all, procreation (self-replication) is the central theme in biology, and we tend to find it more fun when more than one individual is involved. Especially when these individuals differ anatomically into categories, in our case, two types, since that is what's most familiar to us. As far as I know, no lineage has evolved obligatory triple conjugations of three different mating types, although such a thing can be induced in the lab. But for now, let's have a look at a particularly unusual developmental glitch in an individual barnacle, and an even more surreal publication accompanying it:
An Individual Barnacle, Semibalanus balanoides, with Two Penises (Hoch & Yuen2009 J Crustacean Biol) [NOT SAFE FOR WORK due to images of genitalia. Unless you work in biology...]
I came across this while responding to someone's comment, and chuckled. Then I checked whether it really was a single individual case, and whether it really was published in a real journal. In 2009. Yes and yes. It was a rather entertaining read as well. Now, I would go off on a rant about some of their hypotheses and assumptions, but the type of work and the following accompanying note in the acknowledgements suggest this was actually an undergrad project, and I should be nice to my brethren:
"This work was partially supported by a Student Research Fellowship from the American Microscopical Society to [author] and a Crustacean Society Summer Research Fellowship to [author]."
"So, what did you do this summer?" "Found a barnacle with two penises, and you?"

Damn, I wish my summers were as exciting. They usually get spent in a dark room staring at blue [DAPI] dots all day. Sometimes I surgically rape a tiny flower with a pair forceps. Other times I drown my poor seedlings in nasty cytotoxins, and wonder why how they die. This guy got to measure barnacle genitalia. And infer about its sex life.

Here are the two penises in all their glory:

Lemme paraphrase all the scientific lingo: "OMG, TWO penises!" (Hoch & Yuen 2009 J Crustacean Biol)

So why barnacles, of all things? Thing is, upon reaching maturity, they glue themselves to the rock. And become stuck there. And then they get horny, but they can't go out. Kind of like that basement-dwelling 4chan crawling internet loser nerd stereotype. With one key difference: in the barnacle case, size does matter. A lot. Maybe that's not such a key difference, and we won't go there in this polite company (LOL!), but the barnacles can do it without ever going out. All they need is really loooooong penises, long enough to reach the next mother's basement-dwelling geek barnacle. And those beyond it. You can see how this particular sticky situation can lead to evolutionary peddling of male organ enlargment solutions*.

*My horrible, horrible mind is trying to imagine what molecular spam would look like... alas, my imagination does not stretch as far as barnacle penises If only they were immersed in some serious horizontal gene transfer...

They've proposed that at least one of the penises is fully functional, as the sole nearby barnacle has been fertilised. Then they wonder whether this was a genetic or developmental accident. Well, when your sample size becomes very difficult to separate the two. Especially when you terminate the sole specimen by chopping its penises off. A regularly inherited twin penis trait would be rather unlikely; it's quite improbable for a genetic change to result in the doubling of an entire organ in the metazoan version of multicellularity. So it's likely just a chance developmental glitch. I've seen a photo of a tulip with half its leaf converted to a petal, but only one tulip and a single leaf -- another example of an entertaining, but biologically unimportant, developmental glitch.

So, to summarise:

Lab slave: Holy shit guys, this one has two penises!
PI: OMG, let's see if we can publish that!
Slave: LOL nice joke, buddy!
PI: No, seriously!
Reviewer: So what's the scientific significance of this work?
Authors: It has two penises, lol XD!
Reviewer: *giggle* Ah what the hell, we need our [juvenile] entertainment too! *accept*

So what is their actual stated conclusion?
"The result is significant because it shows that the mating ability of the barnacle is resilient to developmental instability and able to overcome extreme departure from normal morphology."
For a sample size of ONE. Remember guys, this isn't a mutant line or anything, this is ONE single freak case. But they had to write something ^_~ Still amused by this getting published though...

And now for another anomaly:

Ciliate orgies
Ciliates are obligate sexual organisms. If they don't have sex within a certain number of generations (~50 for Paramecium), their somatic nucleus basically rots away. Thing is, they actually have two different nuclei - one the pass on, and one they use (ie transcriptionally active). The transcriptionally active 'macronucleus' (MAC) is essentially a giant bag of linear plasmids, sometimes having upwards of ~9000 copies of a single unigenomic, or just really short, chromosome. A problem with having so many chromosomes is evident at mitosis -- how do you attach a bundle of microtubules to every single chromosome of the thousands there are? Well, you just...don't.

Ciliate MACs undergo a special form of nuclear division termed 'amitosis', where the nucleus is more or less pinched in half (ciliates do closed mitosis where the nuclear membrane remains intact the whole time), more or less evenly. Sort of. This is roughly compensated for by some rather crazy DNA replication regulation stuff, but eventually the organism may start losing genes. (how it corrects for the ever-changing gene copy numbers is beyond me...*)

This is were sex comes in -- the ciliate exchanges its germline 'pronuclei' (haploid gametes, if you will) with that/those of its partner (in some species, it gets complicated...), and makes a new MAC. Actually, the making of a new MAC heavily depends on the preceding one, which gets destroyed just as the new one is formed, yet its information can still influence it...basically, a paradise for anyone obsessing over epigenetics! In fact, I've done an essay on that stuff for a class: Ciliate genome rearrangements pdf (not my best writing as I spent way too much time reading stuff and not enough time constructing sensible sentences...)

*Hmmm, just thought of this: overexpression lines might be a problem in a ciliate model, no? It may well be that just like what seems to be happening with the polycistronic gene situation in trypanosomes, may be also happening here: namely -- highly emphasised post-transcriptional and post-translational regulation of gene expression levels rather than direct regulation of the promoter... thus would mean that driving a gene with a highly expressed promoter might be compensated for by some pathways specific to regulating that gene (or its class), thereby screwing with your overexpression attempts. Any thoughts?

So, before I get too carried away with this, ciliates need sex. Furthermore, I'll argue that sex was a prerequisite for such a ridiculous genomic system to evolve in the first place -- frequent sex allowed their genomes to get loose like that, for it could be easily compensated for by more sex. Perhaps this is what fundies fear under 'sex addiction'? In a way, sex does a wonderful job at screwing up otherwise perfectly self-sufficient organisms. So yeah, they're right, sex is a sin. Remember the poor barnacles? Divine punishment.

On the topic of impure deviations and dirty sex, ciliates have been observed having orgies. Like the more familiar fungi, ciliates too have multiple mating types, and avoid breeding with their own. If you have a culture with, say, three mating types, you may, occasionally, see orgies of three (rarely four) organisms. Even when such orgies do occur, most often they feature a pair of ciliates conjugating, while the third kind of sits there sadly and has sex with itself. Literally (autogamy)*. (Chen 1940 PNAS)

The big solid black things are MACs, the things undergoing meiosis are the smaller germline nuclei, which are about to be exchanged. Don't you feel sorry for the poor little guy who got left out? =( (Chen 1940 PNAS)

However, sometimes they can arrange themselves into a circle and pass around the pronuclei in a circular fashion. A true triple conjugation where all the participants can get their fair share:
Wheee - a circular orgy! I suspect there may be enough material for a ciliate Kama Sutra out there... (Preparata & Nanney 1977 Chromosoma)

They also had ways to induce massive group copulation (I guess also orgies, to some extent) using a sex-inducing mystery fluid; which caused massive autogamy sprees in populations of a single mating type -- Chen (1945) proposes it was actually a 'killer', toxic substance secreted by bacterial endosymbionts which render their host immune, and kill off everything else (I don't think they knew about the endosymbionts yet at the time). Basically, their defense response to the threat of death seems to be...having sex.

I think I've just ruined ciliates for you too. You're welcome ^_^

Note: Nice picture of ciliate triple conjugation on its way when I finally scan this Russian paper I 'had' to order through the library...

*When it gets too old and still solitary and mateless, the ciliate can also cure that by having sex with itself. Ciliate microbial sex life would be an awesome topic for a popular book...

Chen, T. (1940). Conjugation of Three Animals in Paramecium bursaria Proceedings of the National Academy of Sciences, 26 (4), 231-238 DOI: 10.1073/pnas.26.4.231

Chen, T. (1945). Induction of Conjugation in Paramecium bursaria Among Animals of One Mating Type by Fluid from Another Mating Type Proceedings of the National Academy of Sciences, 31 (12), 404-410 DOI: 10.1073/pnas.31.12.404

Hoch, J., & Yuen, B. (2009). An Individual Barnacle, Semibalanus balanoides, with Two Penises Journal of Crustacean Biology, 29 (1) DOI: 10.1651/08-3037.1

Preparata RM, & Nanney DL (1977). Cytogenetics of triplet conjugation in Tetrahymena: origin of haploid and triploid clones. Chromosoma, 60 (1), 49-57 PMID: 870290

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