Last week I attended the 2011 meeting of the European Society for Evolutionary Bioogy, held in Tuebingen, Germany. Although I was absolutely shattered by the time it came around (having spent the week prior becoming increasingly frantic as I tried to finish off a review article, analyse data, and create a poster for the conference), I enjoyed it immensely! It was a huge event with lots of really nice and interesting people, all sorts of great talks, and helped down by actual summer weather and a fair amount of hefeweizen…
Over the next few weeks, I’m going to attempt to write some short posts on my favourite talks from ESEB, from dirty bedbug penises to the evolutionary consequences of multiple inheritance systems, and deceitful flowers to sexy robotic crab claws. Hopefully I’ll be able to do them justice.
The previous post was my entry for the Guardian and Wellcome Trust science writing competition 2011 – as you can tell from my having posted it here, my effort was not shortlisted.
I suffer my usual hang-ups on reading it again.. there’s so much more I could have added, different directions I could have gone in, better insights that I could have delivered. I’d be interested to hear any feedback from others, as I’d like to improve, and to see whether my thoughts on this piece (which I’ll hold back for now) are similar to those that others might have. I do tend to cringe upon reading previous pieces, but hopefully with perseverance and posting more regularly on here then I’ll get over that! Or I could just get better at writing, and then I won’t have to.
Think of a duck. Chances are, you’re picturing a mallard – and, if you weren’t, you probably are now. Imagine the male with his striking green-blue head, and the comparatively drab, mottled brown female. If you are a regular reader of science blogs, or simply a fan of waterbird genitalia, your mind may wander to his 20cm-long explosive corkscrew penis, or her cavernous vagina, riddled with dead ends and hairpin bends.
The father of modern taxonomy himself, Carl Linnaeus – admittedly, without having gained privy to these reproductive organs – first classified the male and female mallards mistakenly as separate species. We accept these differences readily nowadays, but how and why have they occurred? Even stranger, why should any species evolve such elaborate reproductive organs?
The answer stems from ‘gametes’, or reproductive cells. Males are defined by carrying sperm, millions of pared-down parcels transporting genetic cargo at high speed. Meanwhile, females harbour relatively few eggs, sluggish monoliths packed with nutrients and protection, waiting patiently for one battling sperm to fuse the genetic information and produce a new organism.
This imbalance in the resources ploughed into gametes results in conflicting desires in the sexes. A male could incur little cost by mating with as many females as possible, increasing the probability of his genes passing to the next generation. His female counterpart, having invested so much in her eggs, gains more from exercising restraint to ensure her offspring are of the highest possible genetic quality.
By what means, then, can a female determine her perfect match? Darwin outlined such characteristics in his 1871 book ‘Selection in Relation to Sex’:
“…the greater size, strength, and pugnacity of the male, his weapons of offence or means of defence against rivals, his gaudy colouring and various ornaments, his power of song, and other such characters.”
This system can be as straightforward as the bull elephant seal using his great strength to drive rivals from a harem of females. Other traits proved far more puzzling – Darwin’s frustration in the years prior to this publication is summarised in an 1860 letter containing the epithet:
“The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!”
One theory is that such traits indicate genetic quality by acting like handicaps. Bright colours, displays and songs attract predators, while a cumbersome tail hinders a quick getaway. A male may be indicating, “Hey, if I have such a big handicap and I’m still here, doesn’t that show you how great I am? You should probably have my babies.”
What happens, then, to those that cannot compete at the highest level – should they simply give up? No, instead they engage in some downright sneaky behaviour, such as yellow dung flies waiting at the edge of a dung heap, ready to pounce on unsuspecting females travelling to meet Mr. Right atop a delicious pile of excrement. On the Hawaiian island of Kauai, Professor Marlene Zuk discovered that the mate attraction ‘song’ of the field cricket – produced by males rubbing their wings together – had enabled an invading parasitic fly to target the species ruthlessly. Rather than face extinction, however, this cricket population rapidly evolved to favour a mutation that removed rough edges from the wings. These smooth, silent crickets possess no real powers of attraction, instead surrounding the remaining chirpers in the hope of engaging a prowling female. While she would prefer a personal serenade from her potential mate, waiting too long exposes her to greater danger – or the risk of being ‘left on the shelf’. There is such a thing as being too choosy, after all.
Another tactic is to offer a ‘nuptial gift’, which can be an edible treat that the male produces himself. This has led to the synthesis of offerings that lower the female’s desire to remate before his sperm have completed fertilisation. ‘Aggressive sperm’ may outcompete or kill off rival gametes, while a dragonfly penis can scoop out existing seminal fluid. The bumblebee, meanwhile, breaks off its penis in the queen to form a ‘vaginal plug’ – an extreme case of putting all your eggs in one basket, if that’s not too confusing an analogy given the topic at hand.
It would be foolish to presume, however, that females have been standing by idly in evolutionary terms. Insects such as water striders and seaweed flies are locked in a race whereby females evolve anti-grasping functions just as the males develop claspers. Indeed, the mallard’s complex vagina has evolved as a defence mechanism. As the female is victim to frequent attempts at forced copulation, this not only helps to prevent entry, but also diverts unwanted sperm away from those precious eggs.
This arms race has raged ever since sex first evolved. As long as males and females continue searching for the tiniest advantage over one another, the battle of the sexes shows no sign of slowing down.
A new entry to my household is this rather wonderful specimen – a ghost mantis (Phyllocrania paradoxa), courtesy of Ornamental Insects. My macro attachment will come in useful – it’s around a centimetre long now, and will grow to only around 5cm. Sexual dimorphism in adulthood is not too pronounced – females are larger, though have less abdominal segments, while males have longer antennae. The crest on the head is fairly impressive… as was the way it was chomping through a fruit fly when I opened the tub this morning! This one is at an early instar, so I will be sure to photo-document each stage if possible.
I had a quick search on Google Scholar, but it seems like they haven’t been studied too much outside basic behavioural and ecological work – hopefully I’ll be able to dig up something cool about them or their nearest relatives though. Either that, or I’ll have to buy in a load more and do some studies myself. If anyone wants to pay me to do so, I can add a paypal button to my site…! In the meantime, you can content yourself with a little read of a post I wrote previously on sexual cannibalism in mantids.
I’m feeling pretty shitty about how long it’s been since I’ve posted in here, and I’ve let it get to the point where I feel I need to write something amazing as a comeback so I can pretend that I’ve been working on that the whole time… but, obviously, that’s total crap. So, here’s a few things that I’ve been doing, and hopefully I can expand on some of them at a later date:
I got a new pet.
His name is Professor Furious, and he is a gargoyle gecko (Rhacodactylus auriculatus). He’s growing at a good rate, and soon will be big enough for his proper tank (and also to check whether he is actually a he or not).
I went on holiday.
We went over to Skye for a week, and Mull for a week. I’m really excited about seeing more of Scotland now that I’m back here, and this was an incredible trip. We saw so many animals, and – thanks to a day with the International Otter Survival Fund – learned a lot about otters (my favourite mammal) and how to spot them. I’ll have to write more about this later, but here’s a brief taster:
I am writing a review paper.
It is going terribly.
I have started a new experiment.
I’m going to have more crickets than last year’s experiment. Thankfully, I have two undergraduate project students working over the summer, so things might not be so bad. Just now, I’m actually struggling to find things for them to do, but I’m sure that won’t last long! I’m getting them to write mini literature reviews, just because I can.
Yeah, I’m a dick.
I went on holiday again.
My good friend Craig is an artist based in Barcelona (check out his work here), and I purchased floor space in his apartment for the princely sum of a ticket to Primavera. It was amazing – Scotland can keep T in the Park; staying up until sunrise while having a few beers and being entertained in a warm seaside locale by acts such as Suuns, Swans, Grinderman etc is something I’m happy to travel for. Plus, nobody got stabbed.
There was some panic as my flights were cancelled due to another volcanic ash cloud, but I managed to get out there ok, and even had an extra day to hang out. I used this wisely, and got some unexpected birding in – heading past the tourists in Parc Guell, and catching a glimpse of two birds I’d been hoping to see, the crested tit and the hoopoe.
I went to the Isle of May.
Seabirds. Seabirds everywhere.
I bought a macro lens attachment for my camera.
Turns out magnifying stuff is awesome.
So, I have been keeping busy, with lots more to come, and therefore I should have no problems getting my blog back on track. Expect another one of these in a couple of months then…
Last Saturday saw myself and some other Stirling-based researchers brave the resurgent snow to travel across to St. Andrews University for 2011’s Scottish Conference of Animal Behaviour (SCAB). This was a really great meeting, being small but still covering a variety of fields – my university was represented not only by attendees from ecology and evolutionary biology, but also from the psychology department, some of whom work in conjunction with the Living Links research station at Edinburgh Zoo.
The talks were all of a very high standard, and I had to prevent myself from exploding in a fit of jealous rage at some of the research being undertaken. Thibaud Gruber kicked things off in this vein, showing some fantastic videos of chimps singularly failing to learn how to use sticks to get at honey he’d secreted in holes in logs. My personal favourite was the experiment in which he actually placed the stick into the hole, only for a chimp to remove it, lick the honey from it, and then throw the stick away in favour of scrabbling around with its fingers and rolled-up leaves. As with all research, the combination of excitement and frustration was palpable…
Bonus video – chimps using sticks to ‘fish’ for termites:
Paris Veltsos of St Andrews gave a talk that was of great interest to me, discussing courtship song and cuticular hydrocarbons (CHCs) in populations of Drosophila montana. Veltsos and his collaborators found that various factors outside simply courtship effort contribute to net selection on song; they also saw differences in CHC selection between the two populations. I had a quick chat with Paris after the end of the meeting, and am looking forward to reading the paper that comes from this work (which I shall then review here).
There were also excellent talks on fish, including one which resulted in the lecturer driving us back to Stirling devising a project that should enable him to sit and watch the Tour de France all summer as ‘research’; another from the University of Glasgow’s Amy Schwartz, on sexual selection in guppies, made tantalising references to ‘Nature’s Laboratory’ in Trinidad. I bit my knuckles as I thought of the stark walls of my two controlled temperature labs. Perhaps I should put some posters up in there.
While I remained under no illusions as to the lack of romance in the laboratory setting of my work, I was clinging to the last vestiges of my pride by thinking, well, my crickets are kinda cute…
…and then came the presentations based on work using the rufous hummingbird.
I’m not sure even the most charismatic of my cricket hordes can really compete with that.
Still, there was to be a final sting in the tail – my friend Ros Murray, also working in the sexual selection lab at Stirling, won the prize for best student presentation. This was no mean feat, considering both the standard of the talks on show and the fact that she was discussing her work on sperm competition in the microscopic nematode worm Caenorhabditis elegans. It was a great talk, and covered some really elegant work that included the use of GFP (green flourescent protein) as a marker that was passed to the next generation by the ‘winning’ sire, clearly indicating to which of the competing males the offspring belonged. The award also comes after finding that this work has been accepted for publication in BMC Evolution journal, which is really excellent news. She probably deserves the reward after the mockery she’d put up with from some of us over her tiny, tiny worm sperm going head-to-head with monkeys and hummingbirds…
Recently, probably due to the incredible macro photography of Igor Siwanowicz that I linked to recently, I’ve become rather obsessed with mantises. Before then, I’d paid very little attention to these weird creatures, and will admit to having been mildly terrified of them in the past. This stemmed from an unfortunate incident many years ago, when I tried to brush one off the door handle of a holiday apartment, only to learn that they can fly – and can propel themselves rapidly towards a human face. The neighbours came rushing out because they had heard what they assumed to be the cleaning lady screaming. Anyway, possibly due to this, I thought that there was just a ‘praying mantis’, and had no idea that the order could range from this:
…and many more incredible shapes, sizes and colours. The displays that a mantis can produce when threatened are really quite incredible, and I have been told that they are great for use in undergraduate practical classes. Mantises are apparently relatively short-sighted, and so two can be placed on opposing ends of a mounted piece of string, and it will suddenly become very clear when they notice each other. Unfortunately, the ‘loser’ will signify defeat by flying off to a remote corner of the classroom, delaying the end of the lesson as the tutor (or, more likely, a hapless TA) climbs up to gingerly retrieve it. Here are two videos of different mantis displays, the first relying on sound and wing movement, the other on the large peacock-style eyes on its wings:
So, what wonders does the mantis have in store for the intrepid sex researcher? Rather distressingly, the answer is sexual cannibalism. Males are smaller than females, which have voracious appetites and can eat up to 16 crickets per day, and so put themselves in a rather precarious position both prior to and during copulation. There is a lot of evidence, including the video below (complete with rather breathless commentary), of females devouring their mates during intercourse, but a controversy remains over the function of this.
Does the male, as in the case of the redback spider, allow himself to be eaten in order that the bearer of his children has a large meal when times are scarce, therefore helping to furnish his offspring with added nutrition? Some other insects allow females to ‘nibble’ on them during sex, thus lengthening the duration of copulation and enabling more sperm to enter the female and fertilise the eggs – could it be that this is a poorly-judged version of this adaptation? The latter seems unlikely, as females generally remove the head first, and although the body continues its final mindless act, studies have shown that ejaculation tends to happen more rapidly after decapitation, if at all.
A 2010 study by Kate Barry, of Macquarie University in Sydney, Australia, investigated the state of female nutritional status on mating dynamics in a sexually cannibalistic praying mantid. Previous studies have shown that scramble competition is important in these mating systems, and thus males are selected for their ability to detect and locate females. Given that each copulation holds the risk of death for the male (and the inherent fitness costs of this occurring), and that condition has been shown to be positively correlated with fecundity in female mantises, then theory would predict the evolution of strong male choice for females in good condition. A female in good condition is not only likely to have more eggs, making her a good choice for a male wanting to ensure that he makes the most of the copulation should it be his last, but is less likely to be starved of food. Interestingly, Barry found that long-distance male attraction to females is somehow linked to female fecundity, with ‘low condition’ females still being attractive to males as long as they had a base level of fecundity. Nutritional status seemed to have no bearing on male choice, and so it would appear that females may produce a pheromone that indicates fecundity. Indeed, in a species of cockroach there exists a relationship between ovarian development and pheromone production, meaning an honest signal is produced to demonstrate a female’s egg-bearing capacity.
It would seem, then, that the unfortunate decapitated males may be those that were unable to secure copulation with high-fecundity females, and sacrificed themselves in a final desperate attempt to pass on their genes. Or perhaps, as can happen in many species, they simply read the signals wrongly.
Note: since becoming more interested in the mantis, I’ve even come so far around as to having decided to place an order with Ornamental Insects for a ghost mantis, after listening to their interview on John F Taylor’s Reptile Living Room radio show. However, you may be able to tell from the picture below that, perhaps, I haven’t quite conquered my fear outright…
The folks over at NCBI ROFL, a blog focusing on scientific papers with a ‘funny’ subject that forms part of Discover magazine’s Discoblog section, are ringing in the new year with a themed week of insect stories! The latest entry is on the rather wonderfully weird sex life of the bed bug Cimex lectularius – I won’t ruin it for you here, but it’s definitely worth a read…
I have managed to get myself a new fancy camera (of which more later), but the bar has truly been raised by finding these incredible photographs by Igor Siwanowicz. Working in the behavioural genetics department at the Max Planck Institute of Neurobiology, Siwanowicz has also contributed to a number of books available via Amazon, and apparently plans to release one dedicated to mantids. If you look at his website, you’ll see why!