The Z-Letter Archive

In best cryptozoological tradition, it’s kind of blurry and far away… The human in the picture is called Nicole Duplaix, and the photo’s from her website, so using Google would be a dead easy way of IDing the beast, but that is called CHEATING. So straight answers please, no peeking.

The Guardian has an exciting-looking article, entitled “New to Nature”, which is about a centipede, Scolopendropsis duplicata, which has been discovered in Tocantins State, central Brazil. This discovery is described in this open access article from the journal Zootaxa by Chagas Jr, Edgecome and Minelli. (Incidentally, Chagas Jr’s first name is highly appropriate: “Amazonas”; his nickname, it appears, is “Amazing”.)

Scolopendropsis duplicata. An individual with 43 trunk segments. Photo by Amazonas Chagas, Jr. (The tail is on the left.)

S. duplicata is particularly interesting because it has “too many” segments. S. duplicata is part of the scolopendromorph order of centipedes, all of which have either 21 or 23 leg-bearing (= “trunk”) segments. As its name suggests, S. duplicata has done something rather odd – it has nearly twice as many segments as expected, either 39 or 43. None of the 700 other scolopendromorph species has more than 23. Furthermore, S. duplicata is unique in that the number of segments (39 or 43) varies within a population.

There have been previous reports of intra-specific variability in trunk segment number, (e.g. Scolopendropsis bahiensis, and species in the order Geophilomorpha) but this variability was always seen between populations, not within. So in the small world of centipede biologists, this is a cracking discovery!

Classification is a difficult business, and everything above the species (the “sapiens” in Homo sapiens) level is effectively a human construct, a way we use to classify organisms, and to describe the process of evolution, rather than something that has real biological meaning. Nevertheless, classification not only helps us make sense of the world, it also provides evolutionary hypotheses that can be tested by morphological and genetic studies

Centipedes as a whole are classified along with millipedes as part of the Myriapoda sub-phylum of arthropods. There are over 3000 species, grouped into five orders. The basal group is assumed to be the Geophilomorpha , which look most like millipedes. Species in this order can have up to 177 segments, but in all other orders 23 segments has hitherto been assumed to be the maximum. Unlike the millipedes, each segment has only one pair of legs.

So normally, if you found a species with such a radically different form – nearly twice as many segments, and unprecedented population-level variability – you’d tend to think they were in different genera (the “Homo” part of H. sapiens). However, everything else about S. duplicata clearly indicates its proximity to other scolopendromorphs, so the authors comment dryly:

“We note the paradox that variability in scolopendromorph segmentation is a remarkable discovery, and yet S. duplicata and S. bahiensis are so similar in other respects and their sister group relationship so highly corroborated that generic separation is unwarranted.”

It seems probable that the genetic basis of the segment variability seen within S. duplicata and between S. duplicata and closely related species is due to variability in homeobox (“hox”) genes that control the way that segmentation takes place. However, things are not quite so simple. In the Discussion, the authors note that all the 43-segmented individuals they dissected were females, while males were only found in the 39-segment group. This suggests that – like in some Geophilomorph species – this species may show sexual dimorphism in segment number.

So whatever is controlling the polymorphism, it would appear to be some interaction between the sex determination genes in this species (and I know nothing about sex determination in myriapods, but it would appear to be on the basis of XY chromosomes, as in most insects and most chelicerates) and the hox genes.

There has been a long argument – going back over 100 years – about how the various arthropod groups should be grouped together. The current wave of molecular data shows that insects and crustaceans are more closely related to each other than they are to the other arthropods (the “pan-crustacean” hypothesis), while insects + crustaceans group together with the myriapods to form the “mandibulata” because they have mandibles, rather than chelicera, which is the mouth appendage seen in the Chelicerata.

The saddest part of the description of S. duplicata by Chagas-Junior et al comes at the end, and suggests the centipede may no longer be extant:

“Most specimens of S. duplicata were found in pitfall traps for reptiles and amphibians in the dry, xeric “cerrado”, a vegetation typical of central Brazil. All specimens were collected before flooding of the Luis Eduardo Magalhães hydroelectric power plant, in the Tocantins River, and the type locality is now under water. Vegetation around the lake is the same as that at the now submerged type locality. An expedition organized by the first author in June 2007 failed to discover any specimens of S. duplicata, even though a forest patch 500 m away from the type locality was sampled. Thus, the original habitat of this species may have been impacted by the flooding of the hydroelectric power plant, and further expeditions are needed to seek additional individuals of this remarkable Brazilian species.”

Finally, why on earth are we talking about this now? The web is full of chatter about it – just try googling Scolopendropsis duplicata and you’ll see what I mean. Because, although The Guardian doesn’t mention it, S. duplicata is not “new to nature” – the Chagas, Jr article was published back in 2008…

The answer, it appears, is the Natural History Museum website, which had S. duplicata, as its “species of the day”, and has a great interactive page, based on the Zootaxa article, of which Gregory Edgecombe of the NHM was a co-author. The Guardian and other websites obviously picked up on this, as did I… The sudden interest must be a trifle perplexing (but pleasing) to “Amazing” Amazonas and his colleagues.

Chilopod facts:

• Most species are carnivorous (they can even eat bats!)

• Like insects, they have trachaea for respiration and mandibles for eating.

• Most species are oviparous (i.e. they lay eggs), but some are viviparous (i.e. they bear live young).

• Like most chelicerates (spiders etc; harvestmen – opiliones – are an exception) they do not have penetrative sex, but the male makes a spermatophore out of silk, which the female picks up and uses to fertilize her eggs.

I spotted this via a link on the Le Monde website. The cat is called Rocky, he’s two year’s old, and he lives with a young woman called Daisy in the Gard region of France. Sadly, he doesn’t do this too much now, as she’s moved the furniture. When the video was taken (November 2009), he could only see the birds if he was standing up. Now, like most domestic cats, he can watch his desired prey sitting down. Oh, and turn the sound off. For some reason Daisy and her partner, Yann, have put some very irritating music on the soundtrack.

Could he do it if the sofa wasn’t so squishy? Why is this behaviour so unusual?

As a special Easter treat, here are two animals for you. First, what about this? No, it’s not from Alien.

And now, what about this, picked up from both The Times and The Telegraph by Greg Mayer over at WhyEvolutionIsTrue.com. The papers describe it as “an oriental yeti” (duh?) or a hairless bear (duh? it has a LONG TAIL). Greg reckons its a civet with a bad case of mange. Any other offers? Whatever it is, it is pretty unhappy. Give it some cream, quick!

It’s not often I’ll cite the rightwing UK newspaper The Daily Mail, but yesterday – as spotted by  Nelly Gidaszewski (PhD class of 07) - they picked up on an amazing set of photos by Polish amateur photographer Mirosław Świętek. Świętek, a 37 year old physiotherapist, went out into the woods at about 3am and took these stunning photos of dew-covered insects. There’s a Drosophilid in there, just for me and Jerry. Apart from their beauty, these photos show the way that physical characteristics change depending on what size you are. When you are the size of an insect, being covered in dew is primarily a problem of aerodynamics and temperature, not getting wet! You can see more of Świętek’s amazing macro photos here.

First posted (just!) at whevolutionistrue.com

What is the name of this mammal, in what part of the world does it live, and what is the name of the tree it burrows under?

A recent article in Time looks at various examples of alleged animal suicide, taking as its starting point the recent distressing film about Japanese slaughter of dolphins, The Cove. Animal-rights activist Richard O’Barry, who features in The Cove, is convinced that animals can commit suicide, having allegedly seen Kathy, a dolphin in the 1960s television show Flipper, sink to the bottom of her tank and stop breathing.

To take the discussion onto a rather more rigorous level, the article references a recent piece by a colleague of mine, Dr Duncan Wilson from the University of Manchester’s Centre for the History of Science, Technology and Medicine. Together with Edmund Ramsden from Exeter, Duncan has just published an article in the history of science magazine Endeavour (subscription required), looking at how animal “suicide” has been interpreted through the ages.

Drs Ramsden and Wilson go back to Aristotle’s story of a stallion that threw itself over a cliff when it realised it had inadvertently mated with its mother (this seems rather unlikely, in my opinion), but concentrate on 19th century views of animal suicide, and convincingly show that accounts of animal suicide  reflect the values of the society in which they are recounted. In particular, during the 19th century, “Humane groups such as the Royal Society for Protection of Animals (RSPCA) seized upon popular accounts to claim that animals shared with humans the capacities for grief, love, despair – and, moreover, that they possessed enough intelligence to plan and execute their own deaths.”

A series of cunning experiments were carried out as part of the growing debate over the nature of animal behaviour – are animals conscious, or is their behaviour “instinctive”? The paragraph on scorpions is worth citing:

“Romanes relayed several accounts where scorpions had killed themselves after being ringed with fire, but noted cautiously, ‘such a remarkable fact unquestionably demands further corroboration before we accept it unreservedly.’ E. Ray Lankester, professor of zoology at University College, London, took up the challenge and, reporting to the Linnaean Society late in 1882, claimed that he had observed a scorpion repeatedly trying to strike itself after he administered chloroform into its glass container. This he believed to ‘throw light on the old tradition’, and tended ‘to confirm its accuracy.’ In 1883, Morgan endeavoured to dispel this belief. He designed a set of experiments ‘sufficiently barbarous…to induce any scorpion who had the slightest suicidal tendency to find relief in self-destruction.’

He surrounded them with fire, condensed sunbeams on their backs, heated them in a bottle, burned them with phosphoric acid, treated them with electric shocks and subjected them to ‘general and exasperating courses of worry.’ Though he witnessed scorpions striking at their backs, this, Morgan explained, was an instinctive attempt to remove irritation. Those who ignored or rejected this fact were ‘not accustomed to accurate observation.’ In 1887, Alfred Bourne provided further evidence that questioned ‘the phenomenon so graphically delineated by Byron’. Scorpions, he claimed, were immune to their own venom.“

The point of Ramsden and Wilson’s article is to show how attitudes to animal suicide have changed over time, and have been shaped by the overall views of any given society: “Through shifting archetypes of animal suicide, we can trace the history of perspectives on self-destruction – we see the victim and hero of ancient philosophy and romanticism, the martyr or sinner of the Judeo-Christian tradition, the automaton and the neurotic, lost amongst the masses of modernity. When scientists, philosophers, writers or theologians have reflected upon the nature of suicide, they have, persistently, reflected on the natural world.”

So where does that leave one of the real, solid examples of animal “suicide” – the worker bee stinging a perceived threat, but dying in the process? The bee’s sting is famously barbed, and as the bee tries to fly away, it pulls out its innards, including the venom gland which not only continues to pulse venom down the sting, but also releases alarm pheromones which attract other bees. The downside is that the bee dies. This video shows the process, and how to get a sting out (it takes an awful lot to provoke the poor bee into stinging…):

The explanation for this behaviour is that the bee is protecting its hive, and thereby its genes. Worker bees are generally sterile (though they can produce male eggs under certain circumstances), so the only way it can make a genetic contribution to the next generation is by helping the hive, with which it shares a high proportion of its genes. From a gene’s eye view, this is not suicide at all, but merely the death of one carrier of those genes, to preserve the life of many more carriers.

So – apart from the examples of social insects, DO animals commit suicide?