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I'm currently supervising a graduate student who's writing a review of the literature on tool use in wild chimpanzees. This has become a most enjoyable interaction: it's a topic I've been interested in for quite a while now, so the supervision role is an excuse to extend my own knowledge, and it's great helping the student to enhance their own skills in relation to academic research and writing. 

Anyway, a couple of days ago I came across a new paper (Boesch et al., 2016) on an intriguing aspect of chimpanzee behaviour, and my student and I had a stimulating discussion about it at our regular weekly meeting this morning. (There's a general summary of the findings and the project which generated them here.) I'd previously heard of (& shared with her) what appeared to be an isolated incident of 'fishing' by an orangoutan, but this new paper documents wild common chimpanzees, Pan troglodytes, using a new technique to obtain freshwater algae. (Of interest in the orangoutan example were the claims that the image of the animal in action were faked, claims discussed here and dismissed as false.)

It seems that it's unusual for primates to eat aquatic plants, although they may eat fish and invertebrates when available. Both bonobos (Pan paniscus) and gorillas eat plants growing in swampy areas. Common chimpanzees do the same, but have also been reported eating algae - something that's really unusual in animals apart from marine species. And it's highly unusual in chimps too: 

despite decades of chimpanzee research, there are only a few observations of algae harvesting, suggesting that this behavior is indeed rare

and in most of these observations the chimps used their hands, rather than tools, to scoop algae from the water. It's possible, of course, that the local ecology of other well-studied chimpanzee groups just don't favour consumption of aquatic algae. But this behaviour could also be due to cultural evolution in a few small social groups.

So, Boesch and his team set up a research station at Bakoun, in Guinea (not far south of the equator), as part of a continent-wide attempt to 

contribute to a fuller understanding of the extent of chimpanzee behavioral variation and flexibility

in order to help get a handle on the actual level of behavioural diversity in wild chimps, and to answer questions around the relative effects of ecological diversity and cultural evolution on differences in behaviour shown by different groups of animals.

The chimps in the study area at Bakoun hadn't been studied before, and to minimise the potential impacts of interaction with humans, all observations were made using 'remote video camera traps', triggered to begin recording on detecting movement. These cameras were set up at sites where there was other evidence of chimp activity, such as remains of tools. Obviously they captured much more than chimpanzee activity, but of the 1,473 video clips that showed chimps, 486 (from 11 different sites), showed the animals 'fishing' for algae (Spirogyra sp.). Most of these events happened during the dry season, when water levels were lower, peaking in the 'hot dry' season when chimps returned repeatedly to the same sites over several days. 


The chimpanzees were observed to fish for algae at sites where the algae occurred in large accumulations at the bottom of the river bed.We rarely observed free floating, surface algae being targeted... [and we] observed all age and sex classes perform and succeed in fishing for algae from deep ponds or river shores.

Interestingly, the researchers found that every single animal used a tool to collect algae, even those only 2 or 3 years old - and they tended to use the same hand each time they fished. They fished by holding one end of a long stick, reaching it down to the bottom of the water, and then twirling the stick so that strings of algae were wound onto it. They then withdrew the stick and pulled the algae off with their lips. And, when algae fishing, the chimps usually avoided getting wet as much as possible. 

To see how successful this was as a food-gathering strategy, two of the research team used a discarded chimp tool - they managed to collect 400g of Spirogyra in just 10 minutes. Since individual chimps were seen fishing for an hour at a time, algae fishing could make quite a contribution to their seasonal diet:

chimpanzees may be fulfilling substantial dietary requirements [for protein, carbohydrates, and lipids, plus antioxidants and minerals] by ingesting large amounts of Spirogyra algae during the dry season

And just what were these tools? Mostly woody branches, modified by stripping off smaller branches and fraying one of both ends; some of these branches were up to 4m long, allowing access to algae that was otherwise unreachable in deeper parts of the river. In around 20% of events chimps arrived at their fishing sites already prepared ie bringing tools with them.

As I commented to my student, research like that described by Boesch and his colleagues goes well beyond simply documenting the activities of our close cousins. This is because, while it's likely our own hominin ancestors used a variety of plant-based tools, these aren't the sort of thing that's likely to be found by palaeontologists, and so 

research on primates can illuminate the potential repertoire of tool use behaviors that may reasonably be assumed to have been present in our last common ancestor (Boesch et al. 2016).

For example:

we suggest that in Bakoun, tool use permits a more efficient access to a rarely available but highly preferred resource, such as algae, that permits chimpanzees to flourish in an environment otherwise more limited in food and water. It is therefore probable that our last common ancestor would have similarly made and used tools to also engage in rudimentary fishing, to collect and consume rich aquatic fauna, and perhaps flora too (ibid.).

And

This [research] demonstrates the flexibility in [chimpanzee] technical skills and how this helps them to obtain access to valuable resources in a drier habitat and new context. Such technological skills have been suggested to be present in our human ancestors when they invaded drier, savanna habitat during the course of human evolution (ibid.).

C.Boesch, A.K.Kalan, A.Agbor, M.Arandjelovic, P.Dieguez, V.Lapeyre, and H.S.Kuhl (2016) Chimpanzees routinely fish for algae with tools during the dry season in Bakoun, Guinea. American Journal of Primatology 78(12), published on-line 3 November 2016. DOI: 10.1002/ajp.22613

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I've just come across a most excellent article by the Genetic Literacy Project. In it, Nicholas Staropoli notes that a proportion of the human genome actually has viral origins.

This might sound a bit strange - after all, we tend to think of viruses as our enemies (smallpox, measles, and the human papilloma virus come to mind). But, as Staropoli notes, there are a lot of what are called 'endogenous retroviruses' (ERVs) - or their remains - tucked away in our genome. (An ERV has the ability to write its own genes into the host's DNA.) And he links to a study that draws this conclusion: 

We conservatively estimate that viruses have driven close to 30% of all adaptive amino acid changes in the part of the human proteome conserved within mammals. Our results suggest that viruses are one of the most dominant drivers of evolutionary change across mammalian and human proteomes.

Carl Zimmer writes about one such example in his blog The Loom: it seems that a gene that's crucial in the development of the placenta (that intimate connection between a foetus and its mother) is viral in origin. In fact, one gene encoding the protein syncytin is found in primates - but carnivores have a quite different form of the gene, while rabbits have a different form again, and mice yet another!

This is a very complex evolutionary story indeed. And so you could do much worse than read the two articles, by Staropolis and Zimmer, in their entirety. 

 

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So, I own a pocket wolf.

...

...

Oh, OK, I own a little black mini-poodle. But, like all dogs, he has the same number of chromosomes as a wolf!

There've been several articles posted recently about the evolution of domestic dogs. While we've tended to think that domestication didn't begin until humans began to settle down & develop agriculture, DNA analysis suggests that wolves and humans may have begun a relationship up to 100,000 years ago. And a paper published in Science back in June presents evidence that there were two domestication events, one in Asia and once in either the Near East or Europe. There's a nice visualisation and explanation of the doggy family tree here.

A few weeks ago, I was discussing domestication with RadioLive's Graeme Hill, and one of the questions he asked was, why do we have so many different body forms in domestic dogs, and so little variation in form in cats? Was it because the dog genome is more 'plastic' & susceptible to change? My answer was that I suspected it had more to do with the length of the species' association with humans. Cats are sometimes described as 'semi-domesticated', and our shared history may go back just 10,000 years (with the possibility, again, of at least two separate domestication events). Whereas 100,000 years gives a lot of time for selective breeding by humans to produce all those different dog breeds.

Which takes us to bulldogs - the subject of a Scholarship Biology question in 2014. Bulldogs were originally bred to drive cattle, and had the strength and the ferocity (and presumably also a high pain threshold!) to subdue an animal by grabbing its muzzle and hanging on. They were subsequently used in bull-baiting, a cruel 'sport' that the UK banned in 1835.

Instead, the dogs were then bred for show. While their physical characteristics remained pretty much the same (short & squat, very muscular, the familiar very short face/muzzle with deeply folded skin) - by 1860 they had already begun to develop, as a result of selective breeding, their now-familiar gentle, non-aggressive temperament.

Unfortunately, selection for that very distinctive body form has brought with it a whole host of inherited disorders. You've probably met a bulldog with that snorfling, stertorous breathing - this respiratory problem is called brachycephalic syndrome, due to the very short face & nasal passage. Other heritable disorders include:

  • hip dysplasia (seen too in other breeds, such as labradors), where the hip joint can partially dislocate - this one is due to polygenic inheritance ie there are a number of different genes involved. 
  • a hole between the two ventricles of the heart. This is called ventricular septal defect (VSD), and an animal must inherit 2 copies of a recessive allele to express this disorder. It's autosomal, which means that male and female bulldogs are equaliy likely to express it.
  • cryptorchidism - one or both testes remains up in the body cavity instead of descending to the scrotum. This one is an autosomal dominant trait - only one copy of the allele is required. 
  • and - with all those wrinkles - dermatitis, also considered to be an autosomal dominant trait. The dermatitis often leads to bacterial infections. 

Poor bulldogs :( 

The actual exam question gave this background information & asked students to discuss two things: how humans may have manipulated the evolution of bulldogs from wolves; and how further selective breeding could be used to try to eliminate EACH of the named disorders AND evaluate how effective this might be. For students intending to sit these exams: remember that when you're answering these questions you need to provide both 'evidential' statements and justifications for them. And to do that, you'll need to integrate the resource materials provided in the exam paper with your own biological knowledge. 

The first part's pretty straightforward: you might consider, for example, why humans would want to select for non-aggressive wolves (eg for help in protecting a human or group of humans from other predators). Or what about the founder effect, which would come into play because of that small population of proto-dogs? The small sample of the wolf gene pool found in those first 'dogs' could mean that particular alleles were simply lost in the dog population, while others could become much more common.

You'd then want to address the sort of things a breeder would focus on to get from generalised doggy form to the highly specialised bulldog: insensitivity to pain; the short, powerful, upwards-facing jaw; the squat, heavily-muscled body. Don't forget the explanation: that the physical features would allow the dog to drive or subdue much larger animals, and that selection for those traits, if they had a genetic component, would see those particular alleles to increase in frequency in the bulldog gene pool.

And of course, once bull-baiting was banned, selection for gentleness/docility came into play. Because that called for further inbreeding in the existing bulldog population, it would likely result in a higher frequency of any existing harmful alleles as well.

The second part of the question tests understanding of students' knowledge of concepts around inheritance. In some cases it's probably possible to remove the deleterious alleles from the bulldog gene pool - but as a result the dogs would diverge from what's currently viewed as the breed standard. For example, selective breeding for a longer, less-wrinkled face could reduce the frequency of brachycephalic syndrome and dermatitis - but the resulting animals would be much less bulldog-like!

The same approach is less likely to be effective for hip dysplasia, however, due to the polygenic nature of this disorder, because it involves multiple genes rather than a single gene locus.

But selective breeding could help with VSD & cryptorchidism. For example, a dog that doesn't express VSD is either homozgyous dominant (with 2 copies of the normal allele) or heterozygous. So at the population level, breeding heterozygous individuals will on average produce 25% of pups with VSD, with the rest not expressing the disorder. Using a test-cross would allow you to breed only from parents homozygous for the normal allele, but it would take more time.  

And with cryptorchidism, you'd avoid breeding from males who had the disorder (which would have very poor fertility anyway, I'm guessing), and from females whose sons had undescended testes (because these females would be 'carriers' for the allele - while cryptorchidism is a dominant trait, you're only going to see it in males). 

Of course, you could also try out-breeding with other dog breeds - but then, the resultant pups may well not conform to the bulldog 'standard'. 

I must say, it does bother me that adhering to a breed standard - a human construct - can perpetuate known health problems in a breed such as this.

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Tunicates are more commonly known as 'sea squirts' - little blobby marine creatures that squirt water when you touch them (hence the name). We don't hear about them often, except perhaps when they make the news for all the wrong reasons. But from an evolutionary perspective they are fascinating little creatures - and it's largely due to their larvae.

As an aside: why do we call them tunicates? Because the body of the adult organism is enclosed in an outer sheath, aka a tunic. The majority of tunicate species belong to a group known as ascidians, which as adults live in shallow waters, attached to rocks or maritime structures (including boats). The remainder are planktonic & found out in the open ocean.

The larvae of many ascidians are free-swimming and, because of their body form, are often described as 'tadpole larvae'. (Some of the non-ascidian tunicates have adults with the same morphology.) These little animals have a number of features (shared with creatures such as the cephalochordate formerly known as Amphioxus) that link them with the chordates: a hollow dorsal nerve cord, a post-anal tail, a pharynx with slits in it (which feeds into the gut), and a living cartilaginous rod known as the notochord, against which the animal's muscles work. (The larvae, and the adults of some non-ascidian tunicates, are basically little swimming filtration units.)

In fact, because of their rather simple structure, tunicates have long been viewed as representing the likely common ancestor of both chordates (a group that includes us) and the slightly-more-complex cephalochordates like Amphioxus. However, a newly-published & fascinating article by Linda Holland (2016) looks at 

the highly derived body plans and life styles of the tunicate classes, their importance in the marine food web and their genomics [with an] emphasis ... on the impact of their especially rapid evolutionary rates on understanding how vertebrates evolved from their invertebrate ancestors.

It turns out that a genomic comparison, using nuclear genes from chordates, cephalochordates and tunicates, indicates that it's actually Amphioxus that sits at the base of this particular group. This in turn means that tunicates

have lost a lot of what the long extinct ancestral tunicate once possessed. 

This genomic work is fascinating on a number of levels. For example, the 'textbook wisdom' is only bacteria (ie Prokaryotes) have their genome organised into operons, where a single mRNA transcript contains several genes. But it turns out that tunicates, which have a rather small genome.

[have] a high percentage of genes in operons

something that Holland states they share with roundworms (nematodes) and some flatworms, which apparently also have "reduced genomes". In tunicates, it seems that among the genes that have been lost are some of the 'Hox' genes - genes that control the development and patterning of body form. 

I learned heaps of new things from this paper: tunicates are able to regenerate most of their bodies, for example (makes sense, I guess, as the sessile adult sea squirt can't exactly avoid being snacked on by predators). Apparently this is achieved by pluripotent stem cells in the animals' blood, though how it's done is still something of a mystery. And I had no idea at all that the animal's 'tunic'

contains cellulose, synthesized by a cellulose synthase that was evidently acquired in an ancestral tunicate by horizontal gene transfer from a bacterium. 

An animal that produces cellulose! Nature never ceases to surprise :)

L.Z.Holland (2016) Tunicates. Current Biology 26: 4 pR146–R152 DOI: http://dx.doi.org/10.1016/j.cub.2015.12.024

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Once upon a time, I wrote about traumatic insemination in bedbugs. (Those of my friends who are still traumatised by learning about the reproductive habits of various slug species may not wish to follow that link.) Now, two papers just published in Nature Communications describe the results of sequencing & examining the genome of the common bedbug, Cimex lectularius

Bedbugs have probably been with us since humans first lived in caves, where the bugs jumped (possibly literally) from bats to Homo. They're now a widespread human ectoparasite (found on every continent apart from Antarctica) and have developed resistance to the pesticides once used to control their populations. In introducing their paper on their analysis of the C.lectularius genome, Rosenfeld & his colleagues (2016) comment that

There is a limited molecular understanding of the biology of the bed bug before, during and after feeding on human blood, which is essential to their life cycle since bed bugs are temporary ectoparasites, whereby they access their hosts for blood feeding and then seek the refuge of the indoor environment for digestion, waste production and mating.

To increase our understanding of the bugs' life cycle, Rosenfeld's team looked not only at the genome sequence but at changes in gene expression, finding the most pronounced changes occurred after the insect had sucked its fill of human blood. They also found that these changes in expression 

included genes from the Wolbachia endosymbiont, which shows a simultaneous and coordinated host/commensal response to haematophagous activity. 

In other words, gene expression in both host and parasite changes in a synchronous way after the bug has fed. (Just as an aside, Wolbachia is a bacterium that has a significant impact on the reproductive lives of its host.) In the bugs the change could be described as huge: "20% of all stage-regulated genes" showed differential changes in expression after a blood meal.

As you'd expect, the bugs have a number of genes with anticoagulant activity - after all, having blood coagulate in their needle-like mouthparts while feeding would really gum things up - plus other genes associated with blood-feeding. The research team also identified a number of mutations that confer resistance to pesticides such as pyrethroids & cyclodienes, plus others that may underlie metabolic changes that speed up detoxification. Genes that have an impact on the thickness of the bugs' cuticle also have an impact on resistance (also noted by Benoit et al. 2016). 

In the second paper, Benoit and his colleagues (2016) also analysed the common bedbug genome to produce

a comprehensive representation of genes that are linked to traumatic insemination, a reduced chemosensory repertoire of genes related to obligate hematophagy, host–symbiont interactions, and several mechanisms of insecticide resistance.

Traumatic insemination involves male bugs stabbing their sexual partners pretty much anywhere on their bodies with a sharp, pointy, penis. It's a habit that can lead to the females picking up a range of pathogens, and unsurprisingly natural selection has driven the evolution of a range of adaptations minimising the physical harm and risk of infection. 

Because the bugs are obligate blood-feeders (haematophagous), their chemosensory system has evolved to allow them to find their particular hosts (ie us). The team observed that the genes involved in this system differed between C.lectularius & the related species that feeds on bat blood, as the 2 species have specialised on different hosts. They identified a total of 102 genes involved in chemosensory pathways, well down on the number found in related bugs (hemipterans) that feed on a range of plant species. (On the other hand, they have a much-expanded repertoire of salivary enzymes, compared to the plant-sucking bugs.)

The bedbugs' specialisation on human blood as their sole food source did have some potential pitfalls, as apparently vertebrate blood lacks some of the micronutrients that arthropods require. And that's where Wolbachia comes back into the story: 

such specialization also drives obligate associations with symbionts, including Wolbachia, that generate critical micronutrients that are deficient in vertebrate blood (Benoit et al., 2016).

Wolbachia does this by providing its host with 

a cocktail of specific B vitamins that are critical for reproduction and development

The research team also found genes encoding proteins (aquaporins) that allow the bugs to rapidly shed the excess water imbibed in a blood meal, and concluded that differential expression of aquaporin genes (and others) allow the bugs to survive periods of starvation and dehydration in between hosts.

In their conclusion, Benoit et al. comment that the wealth of information uncovered by these genomic studies may allow us to move towards an answer to a pressing question: 

What triggered the current bed bug resurgence?

To which harassed travellers would probably add, and how can we bring them back under control?

J.B.Benoit, Z.N.Adelman, K.Reinhardt, A.Dolan, M.Poelchau, E.C.Jennings, E.M.Szuter, R.W.Hagan, H,Gujar, J.N.Shukla, F,Zhu, M.Mohan, D.R.Nelson, A.J.Rosendale, C.Derst, V.Resnik, S.Wernig, P.Menegazzi, C.Wegener, N.Peschel et al. (2016) Unique features of a global human ectoparasite identified through sequencing of the bed bug genome. Nature Communications 7 Article number 10165 doi:10.1038/ncomms10165

J.A.Rosenfeld,D.Reeves, M.R.Brugler, A.Narechania, S.Simon, R.Durrett ,J.Foox, K.Shianna, M.C.Schatz, J.Gandara, E.Afshinnekoo, E.T.Lam, A.R.Hastie, S.Chan, H.Cao, M. Saghbini, A.Kentsis, P.J.Planet, V.Kholodovych, M.Tessler et al. (2016) Genome assembly and geospatial phylogenomics of the bed bug Cimex lectularius.  Nature Communications 7 Article number: 10164 doi:10.1038/ncomms10164

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By now many of you have probably seen images of green-glowing zebrafish, or pigs whose snout & trotters glow in the dark. In both cases the animals are genetically modified and are expressing a fluorescent protein originally sourced from a jellyfish. (The body form of a jellyfish is a medusa, while that of sea anemones & their freshwater relative, Hydra, is called a polyp.) There are a range of these proteins, which collectively belong to a group called the Green Fluorescent Proteins (what else?), and while a wide range of jellyfish produce them1 there are only occasional reports of glowing polyps.

However, in a paper just published in the open-access journal PLoS ONE, Andrey Prudkovsky & his colleagues describe finding tiny (~1.5 mm) fluorescent polyps living in the Red Sea. More specifically, growing in colonies on the shells of small gastropods, a relationship described as epibiotic. The snails are active at night on the sandy seabed, and the researchers noted that the little gastropods buried themselves in the sand when a torch shone on them. They also noticed that the snails, as they moved about in the moonlight, were covered with tiny pinpoints of green light.

Where fluorescence has been described in other polyps, it's mostly been in the 'stalks' of the little animals, but in all the polyps Prudkovsky's team studied, the intense green glow came from a region known as the hypostome - the region around the animal's mouth & encircled by its tentacles. Because both the intensity and the site at which the proteins are expressed is so unusual, the researchers suggest that this could be a useful taxonomic characteristic, given that it's hard to tell one colonial polyp species from another.

They also speculate on the adaptive significance of a polyp having a green glow around its mouth, suggesting that 

[f]luorescence in the hypostome of Cytaeis sp. has probable ecological significance as prey are likely to be attracted to the tentacles and mouth of the polyps

although I do feel that until there's actual observational evidence of this happening, it's a little like an evolutionary just-so story. But isn't the combination of little snails and glowing polyps rather beautiful?

Fig 3.  Hydroid polyps of Cytaeis sp. from the Saudi Arabian Red Sea, scale bar 2 mm; (A) fluorescence of living polyps on the shell of the gastropod Nassarius margaritifer; (B) polyps on the shell of a N. margaritifer specimen, scale bar 2 mm; (C) close-up of polyps, scale bar 0.5 mm.

Fig 3 From Prudkovsky et al., 2016: Hydroid polyps of Cytaeis sp. from the Saudi Arabian Red Sea, scale bar 2mm; (A) fluorescence of living polyps on the shell of the gastropod Nassarius margaritifer; (B) polyps on the shell of a N.margaritifer specimen, scale bar 2mm; (C) close-up of polyps, scale bar 0.5mm. doi:10.1371/journal.pone.0146861.g003

1 And also in comb jellies, marine arthropods, and cephalopods cephalochordates (thanks to herr doktor bimler for picking up the evidence of my brainfade).

Prudkovsky AA, Ivanenko VN, Nikitin MA, Lukyanov KA, Belousova A, Reimer JD, et al. (2016) Green Fluorescence of Cytaeis Hydroids Living in Association with Nassarius Gastropods in the Red Sea. PLoS ONE 11(2): e0146861. doi:10.1371/journal.pone.0146861

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When I was a kid I used to collect shells on the beach - got my Girl Guides 'collectors' badge & everything :) So I really enjoyed reading this post over on Sciblogs NZ. And that in turn reminded me of an article I saw recently on microsnails.

According to that article, 

"Microsnail" is the term for the creatures with shells measuring 5 millimetres or less, sometimes much less (Milius, 2016).

So these are some seriously tiny creatures. According to National Geographic1, microsnails are relatively common (albeit with any given species having a fairly restricted range), but they're just so small that people don't notice them. (NatGeo has an error in the first sentence of that story: I think they meant to say that the snails are a fraction of an inch tall.) However, they are a very diverse group: a 2014 paper on microsnail taxonomy (Jochum et al.) states that snails less than 5mm in length

represent the majority of worldwide tropical land snail diversity. 

The NatGeo story is based on the recent description of 7 new species of microsnail from China, the smallest of which, Angustopila dominikae, could fit in the eye of an ordinary sewing needle: its shell is just 0.86mm long2. Apparently A.dominikae held the mantle of 'smallest land snail in the world' for 5 days, before being knocked off its perch by an even smaller snail from Borneo. 

That there are so many of these tiny species of gastropod shouldn't really come as a surprise: there are more microhabitats available for smaller creatures. (Think, for example, of the tiny eyelash mites that frolic on our faces at night.) But those microhabitats may be limited in extent and that can be a problem (for creatures and those classifying them alike). In the case of the microsnail genus Plectostoma,

many species only occur on a single hill and nowhere else on earth.

And as described in this post on physorg.news

Limestone hills are 'sitting ducks' for mining companies, and many are being quarried away for cement, taking their unique snails  with them to their grave. One species, Plectostoma sciaphilum, is already extinct: its home was turned into concrete around 2003. Similar fates await at least six more species. One of these, P. tenggekensis (named and described in the new paper) occurs only on Bukit Tenggek, which the authors [Liew et al., 2014] forecast to be completely gone by the end of 2014.

Sad to think that these jewel-like creatures may be disappearing from the world even faster than scientists can catalogue them.

Photographs of 17 living Plectostoma species from Liew et al., 2014. Image credit T.-S. Liew.

1 NatGeo has an error in the first sentence of that story: I think they meant to say that the snails are a fraction of an inch tall.

2 Now, if that's their adult size, imagine how tiny the juveniles must be! 

A.Jochum, R.Slapnik, M.Kampschulte, G.Martels, M.Heneka & B.Pall-Gergely (2014) A review of the microgastropod genus Systenostoma Bavay & Dautzenberg, 1908 and a new subterranean species from China (Gastropoda, Pulmonata, Hypselostomatidae). Zookeys 410: 23-40. doi: 10.3897/zookeys.410.7488

T-S Liew, J.J.Vermeulen, M.F.bin Marzuki & M.Schilthuizen (2014) A cybertaxonomic revision of the micro-landsnail genus Plectostoma Adam (Mollusca, Caenogastropoda, Diplommatinidae), from Peninsular Malaysia, Sumatra and Indochina. Zookeys 393: 1-107  doi: 10.3897/zookeys.393.6717

S.Milius (2016) The fine art of hunting microsnails: beauty and sorrow in five millimetres or less. Science 189(2): 4

 

 

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In 2012 the world was introduced to some of the smallest-known vertebrates: tiny chameleons. My good friend Grant wrote about them at the time, & I set an essay assignment for my first-years on these tiny beasties. How tiny is tiny? The following images are from the original paper, published in PLoS one by Glaw, Kohler, Townsend & Vences, 2012.

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Brookesia micra sp. n. from Nosy Hara, northern Madagascar. (A) adult male on black background, showing orange tail colouration; (B) juvenile on finger tip; (C) juvenile on had of a match; (D) habitat along a small creek on western flank of Nosy Hara, where part of the type series was collected. doi: 10.1371/journal.pone.0031314.g008

Anyway,Science News has an article on the speed with which chameleons shoot out their tongues to capture prey. It's based on this paper by Christopher Anderson, published in Scientific Reports.

When a chameleon shoots out its tongue, the movement's driven not only by muscle contraction but by utilising the potential energy stored in stretched elastic tissues. This allows the animal

to release energy more rapidly than by muscle contraction directly, thus amplifying power output. Chameleons employ such a mechanism to ballistically project their tongue up to two body lengths, achieving power outputs nearly three times greater than those possible via muscle contraction.

Noting that small animals are often capable of greater performance in the same feat than larger ones (think about the relative heights that fleas can jump, for example, or the loads that ants are capable of carrying), Anderson hypothesised that smaller chameleons would be able to outperform larger ones when it came to thrusting out their tongues.

To test this, he watched feeding by chameleons from 20 different species, and found that smaller species could indeed reach further: 2.5 times  body length in an individual just 47mm long. And they also achieved much greater accelerations: while larger species send forth their tongues at accelerations as high as 486 m s-2, the smaller ones Anderson studied managed far greater acceleration and power:

peak accelerations of 2,590 m s-2, or 264 g, and peak power output values of 14,040 W kg-1

The interesting question here is, why? Why can smaller chameleons shoot their tongues our further & faster? The answer may lie in the animals' metabolic rates: smaller chameleons will have higher mass-specific metabolic rates, and better feeding effectiveness could mitigate the impact of this. Anderson's data support this: because they also have proportionately longer jaws, larger tongues & associated structures, and higher relative tongue projection distances, 

small chameleons have effectively increased the relative size of their entire feeding apparatus. In doing so, small chameleons have increased the functional range of their prey capture mechanism, and are likely able to capture and process larger prey items than they would otherwise be able to if their muscle cross sections and jaws were not disproportionately large for their body size. This inference is supported by the selection of proportionately larger prey items by the smaller of two morphological forms in Bradypodion. These patterns are thus consistent with those that would be predicted for mitigating metabolic scaling constraints, which may be involved in driving the observed morphological scaling patterns.

Dr Anderson has produced a number of videos showing just what happens when a chameleon strikes, and has kindly given permission for me to use one of them here: 

C.V.Anderson (2016) Off like a shot: scaling of ballistic tongue projection reveals extremely high performance in small chameleons. Scientific Reports 6, article number 18625. doi: 10.1038/srep18625

 

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Well, probably not1, in the sense that most would place on the term 'tummy bug' (where a close proximity to the toilet is a Good Thing), but it turns out that he did have some rather interesting intestinal bacteria.

Ötzi is perhaps better known as the 'Iceman', who died around 5,300 years ago in the Otztai Alps of the Italian Tyrol. (He's the subject of a fascinating web page & I have to say, I'd love to visit the museum, maybe when we next visit family in Europe.) His body, clothing, and equipment are exceptionally well-preserved & are yielding a great deal of information on life in Neolithic Europe - including, as described in the latest issue of Science, the nature of his microbiome. (You'll find the full paper here, but there's also an open-access summary here. I do have a gripe about the use of the term 'tummy bug' in the latter, though!)

In their just-published paper, Maixner's research team reports on their finding of a strain of Helicobacter pylori in Ötzi's stomach contents (he'd apparently eaten a full meal not long before he died). I've written about H.pylori before: while it's been found to be associated with development of gastritis, stomach ulcers, & sometimes cancer in a small proportion of those carrying it2, there's also evidence that it has a protective effect against other disorders, including acid reflux and oesophageal cancer. And it's been with us for a long time:

Predominant intrafamilial transmission of H. pylori and the long-term association with humans has resulted in a phylogeographic distribution pattern of H. pylori that is shared with its host. This observation suggests that the pathogen not only accompanied modern humans out of Africa, but that it has also been associated with its host for at least 100,000 years. Thus, the bacterium has been used as a marker for tracing complex demographic events in human prehistory.

Most modern Europeans carry one particular strain of this bacterium, which is believed to have originated via recombination of two earlier strains. However, the origins of these strains have been uncertain, & the researchers hoped that Ötzi's gut microbes might throw some light on this. The Iceman himself was born and lived in Southern Europe, and DNA comparisons link him to early European farmers. However, the strain of H.pylori found in his gut is most closely related to a haplotype now found in central and southern Asia, and not to those of Europe and Africa.

The detection of an hpAsia2 strain in the Iceman’s stomach is rather surprising because despite intensive sampling, only three hpAsia2 strains have ever been detected in modern Europeans. Stomachs of modern Europeans are predominantly colonized by recombinant hpEurope strains.

Maixner suggests that the Iceman's ancestors must have brought this Asian strain of H.pylori with them when they migrated to Europe. Well after Ötzi died, later immigrants from Africa brought their own strain of the bacterium, and subsequent recombination produced the modern European strain of this microbe. This is evidence for rapid evolution of H.pylori in Europe as waves of human migrants moved into and across the continent.

The researchers also noted that Ötzi's version of the bacterium represents a strain that's associated with stomach inflammation in modern humans - and that protein biomarkers expressed in his gut indicate that he had an inflammatory response to the infection. This may or may not have manifested in actual disease - his stomach lining was not sufficiently well-preserved to let them draw any conclusions on this.

 

1  Which is a real pity, as I was so going to steal my friend Grant's suggested phrase, "the Tyrolean trots", for my title :( 

 It's "found in approximately half the world’s human population, but fewer than 10% of carriers develop disease that manifests as stomach ulcers or gastric carcinoma" (Maixner, Krause-Kyora, Turaev, Hoopmann et al., 2016)

F.Maixner, B.Krause-Kyora, D.Turaev, A.Herbig, M.R.Hoopmann, J.L.Hallows, U.Kusebauch, E.Vigi, P.Malfertheiner, F.Megraud, N.O'Sullivan, G.Cipollini, V.Coia, M.Samadelli, L.Engstrand, B.Linz, R.L.Moritz, R.Grimm, J.Krause, A.Nebel, Y.Moodley, T.Rattei, & A.Zink (2016) The 5300-year-old Helicobacter pylori genome of the Iceman. Science 351 (6269):162-165 . DOI: 10.1126/science.aad2545

 
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I've never heard of gribbles before, & did wonder if they were in some way related to tribbles (or a certain US politician's hair...). But no, it turns out that gribbles are small, wood-boring crustaceans. And they look rather cute: 

A magnified image of the gribble

Image by Prof Simon McQueen-Mason & Dr Simon Cragg 

However, their cuteness should not obscure the fact that gribbles (and their partners-in-crime, the molluscan shipworms & crustacean pillbugs) do a significant amount of damage to the wood of piers, jetties, & vessels. For this reason (Powell, 2012: 326)

Even in today's more ecologically oriented society, a motion to conserve the 'gribble' would receive little support along the world's waterfronts 

And how did I find out about gribbles? Well, a good friend & colleague is a co-author on a just-published paper on the environmental history of marine woodborers (Rayes, Beattie & Duggan, 2015). The authors begin by saying that

While depictions of mariners fighting fearsome sea monsters or battling terrifying storms entertain us to this day, it is perhaps ironic that one of the main threats to commerce over the last millennium or more has come from a series of very small organisms whose history has been submerged in historical accounts.
And they then go on to look at how these marine invertebrates have spread through the world's oceans, disrupting both travel & trade. In New Zealand they found a rich source of information on how European settlers tried to deal with the damage done by the woodborers (aka the "Termites of the Sea"), trying a range of (unsuccessful) techniques in an uncoordinated way.
The depredations of marine woodborers on these structures created headaches for governments, shipping companies and export industries alike, as authorities and companies grappled with the need to repair crumbling infrastructure and ships (ibid).
This was a continuous problem from at least the 2nd millenium BCE - when the Egyptians responded to borer attack by using much thicker ('sacrificial') wood on ocean-going ships & coating it with tar - until the advent of concrete-based infrastructure and ships of iron or steel. I found the history of human responses to the serious damage wrought by these little animals absolutely fascinating. At one point it reminded me of reading - in the 'Hornblower' books by C.S.Forester - of ships being careened in order to replace damaged hull timbers. It's worth noting, too, that some of the treatments applied to timber, while they may have reduced the depredations of gribbles & their ilk, were themselves quite harmful to the environment: think arsenic & mercury, for example.
 
I was surprised to discover that even in recent times, woodborers continue to do damage. For example
between 1995 and 1997, New York experienced severe woodborer damage, resulting in a 21-metre wharf section dropping into the East River and a six-metre section plunging from the Brooklyn pier (ibid).
New Zealand hasn't escaped scot-free. Shipworm fossils date back around 200 million years, and our native mangroves would have been part of their habitat. However, new niches would have opened up to them upon human arrival, dependent as we were on ships and related infrastructure. And in turn, Maori and then European movement to & around our coasts not only carried the native shipworms to new habitats but also introduced gribbles & pillbugs, now well-established here. However, for a long time after European settlement, responses to the problems posed by marine woodborers were handled in quite a parochial, disconnected manner - the authors have done a very thorough job of reviewing historical documents to pull together this aspect of New Zealand's maritime history. And they've found some fascinating little snippets: in 1889, in Timaru,
the effects of gribbles [on the Timaru wharf] were compared to 'the suckling of a sugar stick by a sweet-toothed infant' (ibid).
Incidentally, non-native woodborers can also do considerable harm to mangroves, which is of concern given the significant ecosystem roles that mangroves can play. However, Rayes & her co-authors also make the valuable point that the various woodborers - while they may be a right royal pain in the planking for mariners - also serve a valuable function in their own, original, tropical ecosystems:
Woodborers provide important ecological services within mangrove ecosystems and along coastlines by removing the build-up of dead woody debris, through increasing their rate of decomposition (ibid).
Indeed, it seems that an enzyme from this little wood-muncher may provide a useful biotechnological fix for recycling cellulose-based materials. (This is a valuable reminder that whether something is 'good' or 'bad' is often highly context-dependent; think also of the case of Helicobacter pylori.)
 
So why have we paid so little heed to the gribbles, shipworms, and pillbugs (oh my!)? Rayes et al. have this to say (but I really disagree on the claimed lack of cuteness of gribbles!)
There is nothing remotely heroic about fighting a minute-sized shipworm when one could be grappling with a terrifying octopus ... [Marine woodborers] can offer neither the mystery nor appeal of a whale, still less the terror of a Great White Shark, or the cuteness of a dolphin. They have all the appeal of a snail or a slug, and probably induce the same inclinations ...
 
Yet the fact that gribbles don't sell books or invite the same warm feeling or terror as larger creatures of the sea should not stop us from attempting to rescue them from the enormous condescension of posterity [that ignores their significant role in maritime history].
 
 

Powell, C.E. Jnr (2012) Isopods other than Cyathura. pp325 - 343 in Hart, C.W.Jnr (Ed) Pollution Ecology of Estuarine Invertebrates. pub Elsevier.

Rayes, C.A, Beattie, J., & Duggan, I.C. (2015) Boring through history: an environmental history of the extent, impact and management of marine woodborers in a global and local context, 500 BCE to 1930s CE. Environment and History 21(4): 477 - 512. doi: 10.3197/096734015X14414683716163

 

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