After reading my posts on tubular fossils (here and here), a reader sent me pictures of an object he found while walking on the beach near some cliffs in Lusby, Maryland (USA). Is anyone able to tell him what it is? Is it a fossil, or an inorganic structure? If it is inorganic, any ideas on how it could have formed? More pictures below:
Dardeau, M. R., & R. W. Heard Jr. 1983. Crangonid shrimps (Crustacea: Caridea), with a description of a new species of Pontocaris. Memoirs of the Hourglass Cruises 6 (2): 1-39.
The Great Biological Survey has a long tradition in taxonomy. A collection of researchers and their associates travel to a far-off exotic location* where they spend their time greedily grabbing specimens of everything they can possibly find, before heading back home where the fruits of their labours are sorted, preserved and (hopefully) identified to give an extensive view of the biodiversity of the area surveyed.
*Well, not necessarily that far-off or that exotic. But it can be, and probably a lot more students are drawn in by the prospect of trips to central Africa or the depths of the Amazon than the small patch of remnant bush in the local council park.
Biological surveys are alive and well - I've commented on the results of recent examples here and here, and a current project to recreate the Beagle voyage of Charles Darwin plans to run one on the way (though [a] they're talking about DNA barcoding, a concept that rather raises my hackles - more on that later - and [b] hopefully the captain doesn't shoot himself this time around). Marine biology in particular has a proud history of surveying expeditions, with such examples as the Challenger to look back to.
The "Hourglass" survey began in Western Florida in 1965 and lasted for 28 months, during which samples were taken at regular intervals from stations on the continental shelf of west Florida. Results from this survey were published in a series called Memoirs of the Hourglass Cruises that came to my attention after I picked up a pile of issues of it that had been put into the "free to a good home" pile at the university library. Together, the various articles provide fairly good coverage of the marine fauna of the northern Gulf of Mexico. The Dardeau & Heard (1983) issue is typical in that it not only covers the Hourglass specimens, but takes the opportunity to review the entire Gulf of Mexico fauna (seeing as only one species of Crangonidae, Pontophilus gorei, actually turned up in the Hourglass survey, it could have been a very short paper otherwise). The one aspect that caught my eye was the description of the new species Pontocaris vicina. This species does not seem to be uncommon if the distribution records listed by Dardeau & Heard are to be believed, but had previously not been recognised as distinct from Pontocaris caribbaea. According to Dardeau & Heard, "The two species must have similar but not identical ecological requirements; although taken in successive trawl hauls, they were never taken together in the same haul".
Credits: The photo at the top comes from Wikipedia. Though a crangonid, it is not one of the Gulf of Mexico species. Rather, it is the north-east Atlantic Crangon crangon, one of the more commonly fished shrimp species in Europe.
Kevin Z has asked me to contribute my favourite choice of schlocky Z-grade horror movie, an idea that started with Rick Macpherson. I did have some objections to replying - the concept of "Halloween" is something of a bugbear of mine. Traditionally we don't celebrate it here in the Antipodes, and I've tried to dissuade its encroachment into the Great Southern Consciousness. What can I do at this point other than quote the great David Bowie:
In the end, though, I couldn't resist the opportunity to pull out a few wonderfully terrible monster films. I don't do actual horror films in the modern sense - I have a surprisingly low tolerance of gore on screen, or of things jumping out at me - but I adore a papier-mache monster.
The Wasp Woman
Janice Starlin has a problem. For many years, she's been the director and public face of America's leading cosmetic company, but time is collecting its inevitable toll. Despite her best efforts to hold back aging, anything less than perfection is unacceptable in the cut-throat business of beauty. Her search for a solution brings her into contact with Eric Zinthrop, a slightly eccentric researcher. Zinthrop, well aware of the anti-aging properties of royal jelly produced by bees, has begun research into the royal jelly of wasps. He discovers that wasp jelly can not merely slow aging, but actually reverse it!* Starlin wastes no time in installing Zinthrop in a primate laboratory, and insists on becoming his first human test subject. Unfortunately, Zinthrop is unaware that the impatient Starlin is sneaking into his laboratory and injecting herself with far more of the solution than he has judged to be safe...
*All the same, they should have known something was up when the guinea pigs he injects his solution into not only get younger, but actually change species into rats...
When I saw this movie last year, I was actually stunned by how good it was. It's not a great movie, but you can see a great movie somewhere struggling to get out - trapped by the dollar-a-day budget. The inescapable ridiculousness of the monster costume is, at least, ameliorated by its having very little actual screen time, with more mileage drawn from Starlin's attempts to conceal what is happening. In contrast to the usual run of mad scientists (see later), the mayhem is not caused by a researcher acting with disregard for humanity, but by the subject's refusal to accept the researcher's cautious approach. Like the classic King Kong, despite the monster's seemingly horrific nature, the intention is ultimately not to bring fear but pity. In King Kong, 'twas beauty killed the beast. In The Wasp Woman, it's the pursuit of beauty.
As an aside, the life of Susan Cabot, the actress who played Starlin, seems also worthy of film (and indeed, apparently a biopic is in production). Cabot met her own end when her son, a sufferer of both dwarfism and mental illness, bludgeoned her to death.
Horrors of Spider Island
Even in black and white, movie directors were well aware of the virtues of making a "horror" movie for the essential purpose of getting a whole bunch of large-breasted women to run about in very little clothing. A troupe of exotic dancers and their super-masculine manager crash-land on their way from America to Singapore and are washed up on a deserted tropical island. Nightie-ripping catfights over who gets to bed the only available MAN are dulled slightly when he is bitten by a giant radioactive spider, causing him to mutate into a supposed half-man, half-spider creature that looks more like a shaven Wookie in need of a good orthodontist.
I recommend that male readers of this blog watch this movie only when in the exclusive presence of their own sex. The levels of chauvinism demonstrated at some points are such that female viewers will probably have an uncontrolable urge to thrash the nearest male simply for being there.
And last but certainly not least...
Mesa of Lost Women
Oh. My. God. Sometimes words just fail me. I don't know where to begin...
I came across an IMDB comment that described this piece of bizarritude as "the greatest Ed Wood movie not made by Ed Wood", and I couldn't agree more. It has the complete absence of acting ability, the total disregard for lighting and perspective, even the overbearing Griswold style voiceover. Ed Wood, the... ahem... multi-talented director of Plan Nine from Outer Space and the quite unforgettable Glen or Glenda, or I Changed My Sex was actually not connected to this particular piece of drek, though he apparently did use the same flamenco guitar riff in his later Jailbait. Believe me, after sitting through Mesa of Lost Women, you'll remember the flamenco guitar. The same three bars cycle in an infinite loop throughout the entire - freaking - film! Not even the B-52's doing "Rock Lobster" can compete with that.
Back to the movie. On an isolated mesa in the middle of a New Mexican desert, a mad scientist is experimenting with injecting human growth hormone into spiders, producing an army of beautiful spider-women (as well as stunted little dwarf men, because male spiders are a poor comparison to the females). The mad scientist (named, ha ha, Dr Araña) tries to talk another scientist into joining his researches, depriving him of his reason when he refuses. Through a rather convoluted set of coincidences, the stupefied victim ends up escaping from the mental hospital he's been confined to, taking a bunch of people hostage and escaping in a light plane that happens to crashland on the very mesa housing Araña's spider people!
Seriously, I simply cannot explain this masterpiece of ineptitude. "In the continuing war for survival between man and the hexapod, only another fool would bet against the insect". Except, of course, that spiders aren't insects*.
*Funnily enough, I found this last point slightly less annoying than a similar problem in the recent movie version of Charlie and the Chocolate Factory, a film I mostly liked except for an overwhelming urge to scream at the television: "Listen to me! Chocolate. Is. Not. Candy!"
The Canellales are a small order of flowering trees and shrubs, most of which are found in the southern continents though some species reach as far north as Florida and Indonesia. Two families are included in Canellales, the Canellaceae and Winteraceae. Canellaceae is found in the Ethiopian and Neotropical biozones, while Winteraceae is Australasian, Malesian and Neotropical (the image at left is of Drimys winteri [Winteraceae], and comes from Flora Chilena).
Canellales are members of the "magnoliids" - the paraphyletic assemblage of basal flowering plants that aren't eudicotyledons, aren't monocotyledons, and are still proving difficult to place phylogenetically. Recent analyses have all agreed that the so-called "ANITA grade" includes the basalmost flowering plants yet in existence (the name ANITA derives from the taxa included in this group: Amborella-Nymphaeales-Illiciaceae-Trimeniaceae-Austrobaileya). After that, it all goes a bit custard-shaped. As well as the well-established clades of eudicots and monocots, we have Chloranthaceae, Magnoliales, Laurales, Piperales, Aristolochiales, Canellales and Ceratophyllum (some authors, such as Thorne [2000], have included some or all of these orders in an expanded Magnoliales), with almost every combination imaginable of these nine clades turning up somewhere. Nevertheless, there is a reasonable amount of molecular support for a true "magnoliid" clade including everything listed above from Magnoliales to Canellales, with Canellales probably sister to Piperales (including Aristolochiales - Zanis et al., 2002; Angiosperm Phylogeny Group, 2003). Though an association between Canellaceae and Winteraceae was first recognised on molecular grounds only, morphological characters have since been identified in support of the Canellales.
Previously, Winteraceae had been regarded as very primitive flowering plants because of their lack of vessels, specialised xylem cells for the transport of water that are characteristic of flowering plants (xylem is the central part of the plant stem that transports most of the plants water through no-longer-living cells). In vessels, the axial ends of the deceased xylem cells has become perforated or open, so instead of separate cells the plant has continuous tubes allowing for much easier water transport. The only other angiosperms to lack vessels are Amborella (possibly the basalmost of all living flowering plants) and the small eudicot order Trochodendrales.
However, the modern position for Winteraceae implies that its vessel-less condition is not primitive but derived from vesselled ancestors. What could have led the ancestors of the Winteraceae to abandon the seeming advantages of a vessel system? Field et al. (2002) compared the effectiveness of water transport in the vessel-less Winteraceae and the vessel-bearing Canellaceae. While Canellaceae had much more efficient water transport than Winteraceae, freezing and thawing had a much greater impact on water transport in Canellaceae than Winteraceae, leading Field et al. to suggest that the lack of vessels in Winteraceae might have been an adaptation to survive freezing cycles in temperate Gondwana. This seems to be the most likely explanation yet available, but as always with science, a whole host of other questions arise - if vessels are so problematic for cold-climate taxa, why have so few other angiosperms lost them? Field et al. do suggest that greater differences between vessels and standard xylem cells in more derived taxa may have put greater constraints on their loss, but I feel this is still very much an open question.
One feature that Canellaceae and Winteraceae share in common is the notable production of aromatic oils by members of both families. Canella alba (shown here in an illustration from Wikipedia) was transported from South America to Europe as "white cinnamon", and its bark is used in much the same way as cinnamon. The leaves of horopito (Pseudowintera colorata), a small tree found in New Zealand, were used as a condiment, as are those of Tasmanian pepper (Tasmannia lanceolata). I can personally vouch for the edibility of horopito - it has a strong peppery taste, similar to nasturtium but far stronger.
REFERENCES
Angiosperm Phylogeny Group. 2003. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II. Botanical Journal of the Linnean Society 141: 399-436.
Thorne, R. F. 2000. The classification and geography of the flowering plants: Dicotyledons of the class Angiospermae (subclasses Magnoliidae, Ranunculidae, Caryophyllidae, Dilleniidae, Rosidae, Asteridae and Lamiidae). Botanical Review 66: 441-647.
The latest Boneyard is up at the Hairy Museum of Natural History. There seems to be a lot of comment on the recently-discovered Futalognkosaurus, though the name's not nearly as unpronounceable as people think it is...
The newest thing meme-wise is to try and find if there are any search queries on Google for which your site comes up as the first entry. So I've just hopped onto Google Webmasters, which gives me a list of Google searches that have returned my site and the rank it got in the search. I also tried running the search through Google myself to see exactly what it was bringing up (it was a little obscure in some places). Apparently yours truly is a world leader on the web when it comes to:
- green frog sex (In fact, "frog sex" is apparently by far the most commonly used search term that returns the Catalogue. I have often wondered what on earth is so fascinating to people about frog sex, but I'm too scared of what I might discover to find out). The same page is entry No. 1 for catalogue sex lack, which is a little sad.
Okay, we'll see how long this one lasts - I'm going to attempt to add another feature to this site. Like anyone working in the field of science (and doubtless any other academic discipline), I've accumulated quite a pile of references of one form or another. In fact, my EndNote library has a little shy of 6000 entries, most of which lurk in a pair of ominous-looking filing cabinets sitting in the back of the office at home that Jack has given up trying to ask me to bring some order to. So the idea is that each week I'll select one of the entries in my EndNote more or less at random to read over and review. It may be a paper of great significance, it may be something completely trivial. It may be of interest to many, it may be of interest to almost none. All I know is that it will hopefully give me an opportunity to actually read some of the things I've probably taken a copy of at some point ande flicked through briefly before filing it away never to be seen again. So, on to this week's review, of the article that was my 1000th entry into EndNote:
Zhang, Y.-D., & A. C. Lenz. 1997. Uppermost Wenlock and Ludlow graptolites from southern Yunnan, China. Canadian Journal of Earth Sciences 34: 1220-1238.
I'm probably showing unbelievable levels of geekiness in saying so, but I have a certain degree of affection for graptolites. They were one of first examples I became aware of as a lad of a completely extinct lineage of fossil organisms of uncertain relationships to anything alive today. Graptolites were an abundant group of colonial animals in the Palaeozoic. The name Graptolithus can be translated from Latin as "rock with writing", and was originally coined by Linnaeus for what he thought were mineralisations of inorganic origin (Linnaeus' original classification covered minerals as well as plants and animals).
The most speciose lineage of graptolites, the Graptoloidea, was planktonic (the picture above comes from here, and shows a reconstruction of the basal planktonic graptolite Rhabdinopora), but other orders of graptolites were sessile and benthic. Most modern authors agree that the graptolites were closely related to the pterobranchs, a small group of modern colonial animals (both in the sense of not including many species, and in being small in size). The story of how the relationship between graptolites and pterobranchs came to be recognised is an interesting one in its own right - critical well-preserved specimens of early sessile graptolites were described by Roman Kozłowski from the Holy Cross Mountains in Poland (Kozłowski, 1949), but the results of his research almost never saw the light of day due to the minor inteference of the Second World War.
As I've already indicated, the earliest graptolites were benthic, and one of the most successful benthic orders were the Dendroidea, so-called because of their multi-branching tree-like structure. The Graptoloidea were derived from dendroid-type ancestors, and basal graptoloids such as Rhabdinopora can essentially be described as a dendroid detached from the bottom and hung upside down. Many popular books will then go on, as I am about to, to describe the subsequent history of graptoloids in a misleadingly linear way. However, the dendroids did not disappear with the rise of the graptoloids, though they never achieved the diversity of the latter. In fact, the dendroids survived long after the graptoloids had fallen by the wayside - dendroids were still alive and well in the early Carboniferous, while graptoloids never made it past the Devonian.
Nevertheless, as time went by the early multi-branched planktonic forms gave way to descendents with a far simpler organisation. Four-branched taxa gave rise to two-branched taxa, which in turn gave way to the linear monograptids (the illustration at left comes from the University of Oslo, and shows the single-rowed Spirograptus turriculatus). Another group of graptoloids, the retiolitids, took a different approach to lightening the colony structure, and reduced the colonial wall to a minimalist net-like framework (Kozłowska-Dawidziuk, 2004 - I'd recommend taking a look at this article, especially if, like me, you've had some difficulty in imaging retiolitids as live animals).
Graptoloids are a very useful group of organisms for biostratigraphy, combining the ideal features of wide distribution of individual species with relatively rapid species turnover. Biostratigraphy is the main focus of Zhang & Lenz's (1997) paper. The Ludlow epoch was in the later Silurian (see the Palaeos page) and the fauna described by Zhang & Lenz consists entirely of monograptids and retiolitids, the only graptoloid groups to survive the end of the preceeding Wenlock epoch. There's not much to say about this paper - it's a fairly standard example of a faunal survey, describing the graptolites found in the Shuiqingliangzi section in southern China. No new taxa were described, though detailed redescriptions were given of a number of taxa.
REFERENCES
Kozłowska-Dawidziuk, A. 2004. Evolution of retiolitid graptolites - a synopsis. Acta Palaeontologica Polonica 49 (4): 505-518.
Kozłowski, R. 1949. Les graptolithes et quelques nouveaux groupes d’animaux du Tremadoc de la Pologne. Palaeontologica Polonica 3: 1-235.
Bug Girl has introduced me to a fascinating piece of research that was published today in Proceedings of the National Academy of Sciences of the USA. A pair of researchers have turned their attention to the question of how aquatic organisms become trapped in amber (Schmidt & Dilcher, 2007).
Amber, as you may already be aware, is formed from resin exuded by trees hardening on contact with the air. While the resin is still fluid and sticky, small organisms such as insects may become trapped and covered. As the resin turns into amber, the engulfed organism is sealed off from the ravages of the outside world and preserved (image above is of an alate termite, and is from here). Good examples of such amber inclusions are arguably the best preserved fossils in the world, and provide a depth of information that is simply not possible with other preservation methods. Details can be preserved right down to the cellular level and smaller, while soft-bodied organisms such as nematodes and protozoa that are otherwise absent from the fossil record may be found.
As already indicated, exposure to air and drying is a vital component of the process of resin turning into amber, and so it has generally been assumed that amber must form terrestrially. Unfortunately for this assumption, aquatic organisms are not uncommon in amber. A number of suggestions have been made to explain how they could have gotten there - they could have been living in water sitting in hollows between branches (technically referred to as "phytotelmata"), or they could have been travelling between bodies of water, or they could have already died in the water before being blown by the wind into resin. As pointed out by Schmidt & Dilcher, none of these options is really a good enough answer. Terrestrial dispersal is just not an option for some obligate aquatic organisms found in amber, and wind dispersal of dead organisms wouldn't explain the numbers of aquatic taxa found (as well as seeming unlikely for soft-bodied organisms such as protozoa). Phytotelmata are also not common enough to explain the numbers found, especially as most amber deposits are believed to have been formed by conifers.
Schmidt & Dilcher decided to solve the problem by emulating amber formation in a patch of swamp forest owned by Dilcher. After "inducing artificial resin outflows from pine trees" (translation: hacking off pieces of bark with a handsaw), Schmidt & Dilcher observed what happened to the resin after it came into contact with water sitting in small pools on the ground.
Fig. 1. Resin in Dilcher's swamp forest east of Gainesville (Florida). (A) Pinus elliottii and other trees standing in the water. (B) Resinous exudate spreading at the water surface. (C) Small elongate resin pieces of up to 4 cm in length hanging at the water surface attached to the tree trunk. (D) Solidified resin piece at the water surface with trapped insects and anthers (arrows). (E) Subaquatic resin with enclosed detritus flowing downward on the tree trunk. (F) Subaquatic pillow-like resin piece of 5 cm flowing on the swamp floor. (G) Extensive subaquatic resin flow of 20-cm length on the swamp floor. (H) Pillow-like resin piece of 2.5 cm width in lateral view with trapped water beetle (arrow). (Scale bars: 1 cm.) (from Schmidt & Dilcher, 2007)
Some resin spread over the surface of the water in a thin film - while organisms could be trapped in this, it was not thick enough to be likely to preserve anything long-term. Blobs of resin could remain attached to the tree at the water surface, and organisms could become trapped on the underside of these. Finally, if there was enough resin to break the water surface, it formed pillow-like masses at the bottom of the water. Small organisms such as rotifers and mites could be trapped in the surface of the resin, burying themselves deeper in the mass as they struggled to escape. After a day or two, a thin hardened skin formed over the mass, generally excluding micro-organisms, but larger mobile animals such as water beetles could still break through the skin and become trapped (the authors did not comment on whether such animals were likely to be actively attracted, tarpit-wise, to food organisms already trapped). Resin masses could move and flow in the water, and small droplets of water that might also contain micro-organisms could become enclosed in the resin. As long as the resin remained liquid, bacteria and fungi could even grow in the mass, making them more likely to be preserved later.
As long as the resin remained covered by water, it didn't harden, but when the pool dried the mass hardened and solidified. As Schmidt & Dilcher explained in their paper, their observations have a number of taphonomic implications for using amber inclusions to reconstruct the environment they formed in. Inclusions would be biased towards fungi and bacteria growing in the resin and larger animals that could break through the skin. Because the window of opportunity for micro-organisms to become trapped before the skin formed was relatively small, such organisms were less likely to become inclusions.
Schmidt, A. R., & D. L. Dilcher. 2007. Aquatic organisms as amber inclusions and examples from a modern swamp forest. Proceedings of the National Academy of Sciences of the USA 104 (42): 16581-16585.
The Saxifragaceae are a small family of about 30 genera of herbaceous plants found in the temperate zones of the world (more in the Northern Hemisphere than the Southern - image of Saxifraga oppositifolia from Wikipedia). Many species are found in alpine or arctic habitats. The flowers have a corolla of five separate petals and five conjoined sepals and are often borne in a raceme, while the fruit is generally a dry capsule.
Classification of the Saxifragaceae is a point fraught with difficulty. The brief description I've given applies to what was the subfamily Saxifragoideae, to which phylogenetic studies indicate the family should probably be restricted (Soltis & Soltis, 1997). Saxifragaceae sensu stricto is then placed in a small order Saxifragales with families such as Crassulaceae, Paeonia and Grossulariaceae. Crassulaceae and Saxifragaceae have both been regarded in the past as members of the subclass Rosidae, and it seems likely that Saxifragales are basal rosids, but other published phylogenies show a little uncertainty about their exact position relative to the rosid-asterid split (for instance, Kårehed [2001] shows Saxifragales as sister to Caryophyllales + Asteridae rather than to Rosidae, but taxon sampling was very low).
Other taxa previously included in Saxifragaceae have been scattered to the winds, settling in a whole range of places within the angiosperm family tree. Most notably, a collection of past saxifragaceans has staked out a position low in the asterid tree as the family Hydrangeaceae. Hydrangeaceae will probably be most familiar as the family including the hydrangeas widely grown as ornamentals (and going by what I've heard people saying, seemingly a real love-them-or-hate-them kind of plant). I was always impressed by the story that flower colour in hydrangeas is determined by soil pH - plants in acidic soil produce blue flowers, while alkaline soils give rise to pink flowers.
I had intended to write this post on the genus Broussaisia in Saxifragaceae, but in looking up information for the post I soon discovered that Broussaisia is no longer a saxifragacean as it was listed in Yampolsky & Yampolsky (1922), but a member of Hydrangeaceae. In fact, phylogenetic analysis indicates that Broussaisia (including a single species of Hawaiian shrub, B. arguta, commonly known as the kanawao) is nested within the genus Hydrangea (Hufford et al., 2001). The kanawao (shown above in an image from Wikipedia) is found on all the main islands of Hawaii, and is quite unusual for Hydrangeaceae in producing a fleshy (albeit small) fruit. Go to lemmingreport for an interesting page collecting old reports on the use of kanawao in traditional medicine - apparently the fruit could be used to "bring about conception with a barren woman". The efficacy of this remedy was such that apparently one could vary the dose to determine whether the child was a boy or a girl... However, the supreme money quote has to be: "It was the way of increasing the population in Hawaii during the old days. ... Look at how the numbers of Japanese, Chinese and Filipinos have increased in immigrating in Hawaii. They are not good at settling, but they do take care and know how to increase their numbers".
REFERENCES
Hufford, L., M. L. Moody & D. E. Soltis. 2001. A phylogenetic analysis of Hydrangeaceae based on sequences of the plastid gene matK and their combination with rbcL and morphological data. International Journal of Plant Sciences 162 (4): 835-846.
Kårehed, J. 2001. Multiple origin of the tropical forest tree family Icacinaceae. American Journal of Botany 88 (12): 2259-2274.
Soltis, D. E., & P. S. Soltis. 1997. Phylogenetic relationships in Saxifragaceae sensu lato: a comparison of topologies based on 18S rDNA and rbcL sequences. American Journal of Botany 84 (4): 504-522.
Yampolsky, C., & H. Yampolsky. 1922. Distribution of sex forms in the phanerogamic flora. Bibliotheca Genetica 3: 1-62.
Reconstruction of Gondwana in the Permian, showing the modern thicknesses of continental lithosphere. From Kumar et al., 2007.
A very cool paper in today's Nature (link below) deals with the question of India's movement after it broke away from Gondwana about 140 million years ago. Plate tectonics has a bit of a tendency to leave me gasping for breath, because the forces involved are just so incredible. Great chunks of the planet's surface get ripped up by colliding masses of rock bigger than all imagining, at scales at which living organisms just become negligible.
Most of you are probably aware that the Earth's crust is divided into large chunks called plates. The plates are moving in all different directions - magma wells up from the more fluid mantle under the crust on one side of the plate, cools down to form crustal rock which is carried with the movement of the plate to the other side, where things can suddenly get interesting.
Crustal rock falls into two categories. Oceanic crust is heavier, while continental crust is more buoyant (obviously, 'buoyant' is a relative term when you're dealing with rock). When a travelling piece of oceanic crust runs out of plate, it sinks down beneath the opposing plate, and is remelted back into the mantle. Continental crust, however, doesn't do this - it's too light to sink and so it simply bobs in place, like a cork in water. When two pieces of continental crust on opposing plates run into each other, neither is able to go beneath the other, and an almighty crash occurs. The force of these rockmasses pushing into each other pushes the rock at their junction upwards, and many of the world's mountain ranges represent present or past collisions of continental crust. The Himalayas and their backing ranges are where India is currently ploughing into Asia, while the Alps were formed as Italy (with the weight of Africa behind it) pushed up against the rest of Europe.
Eventually, the continental collision runs out of steam, and the plate boundary becomes fused to form a supercontinent. This isn't necessarily the end of the story, however. Supercontinents have formed many times over the Earth's history, only to fracture at a later date and scatter pieces of continental crust back in different directions again. The mechanisms for this are unclear, but the leading idea is that heat building up underneath the continental mass rises up as a mantle plume, ripping apart the overlying continent. The Great Rift valley in eastern Africa represents a current plate fracture in action. The supercontinent of Gondwana contained the present-day landmasses of Africa, South America, Antarctica, India and Australia. before its division over the course of the Mesozoic.
For the most part, this was a fairly sedentary process. Africa and Australia drifted off at about 2 to 4 cm per year. Antarctica seems to have been fairly happy where it was, and hardly moved at all. India, however, was a different matter - it couldn't wait to escape the family home, and tore off at incredible speeds of up to 20 cm a year. Its eventually collision with Asia about 50 million years ago slowed it down somewhat, but it still travels at 5 cm per year, faster than all the other Gondwanan fragments.
Topographical view of India and the Tibetan Plateau (from 100gogo), showing the line of India caning into Asia.
How was India able to achieve this massive speed? Today's paper by Kumar et al. explains that. Using seismic readings, they measured the thickness of the continental crust in the Gondwanan fragments. The deepest part of Africa has a continental thickness of more than 250 km. Antarctica and Australia have thicknesses of about 150 km. India, in contrast, has a thickness in places of less than 100 km. It seems that it is the absence of that deep keel that has allowed India its free movement.
The presence of deposits such as diamond-bearing kimberlites that form at very deep temperatures in India indicate that its crust wasn't always so thin. Kumar et al. suggest that the mantle plume that caused the breakup of Gondwana may have melted away the deeper parts of India before flinging it northwards like a dart into Asia's underbelly.
Taxon of the Week has been delayed a day, as I wasn't actually at uni yesterday. But never fear - I know how much you've all been hanging out to see what the supreme organism will be this week, and this week's chosen organism is the turrid gastropod genus Comitas (image from here).
Turridae is a family of predatory gastropods, mostly fairly small though Comitas is one of the larger members, reaching up to 95 mm in length. The turrids belong to a clade called Toxoglossa that also includes the better-known Conidae (cone shells). The name Toxoglossa means "poison tongue", and a well-developed poison gland is associated with the radula of toxoglossans for the capture of prey. This has been taken to the greatest extent in cone shells, at least some of which are toxic enough to be dangerous to humans. Compared to other gastropods, toxoglossans show reduction in the numbers of radular teeth while individual teeth become larger and more elaborate (figure below from Kantor & Taylor, 2000). In cone shells, the individual teeth are long and spiral in cross-section to form a hypodermic toxin injector.
Though there are far more species of Turridae in the world than Conidae, the latter receives a lot more attention than the former, probably because turrids are generally smaller, more retiring and more likely to be found in deeper waters. Comitas is found in deeper and cooler waters of the Indo-Pacific (Powell, 1966).
REFERENCES
Kantor, Y. I., & J. D. Taylor. 2000. Formation of marginal radular teeth in Conoidea (Neogastropoda) and the evolution of the hypodermic envenomation mechanism. Journal of Zoology 252: 251-262.
Powell, A. W. B. 1966. The molluscan families Speightiidae and Turridae: An evaluation of the vaid taxa, both recent and fossil, with lists of characteristic species. Bulletin of the Auckland Institute and Museum 5: 1-184.
Today is Blog Action Day. Thousands of blogs around the world are going to be commenting on a single issue, and this year's issue is the environment. Hardly surprising - the environment is rather a hot topic at the moment. Indeed, for perhaps the first time in history, the environment is practically overshadowing the economy as a deciding issue in the upcoming national elections here in Australia.
The concept of environmental awareness (at least in the modern sense) is actually a relatively recent one. There was a time when the world's resources seemed almost inexhaustible. Expectations were that production would rise ever higher as more and more of the world was turned over the cultivation, while "unproductive" ecotypes such as prairie and wetland would be drained, fertilised, and pressed into human service. Those who suggested forbearance were little heeded, with their warnings of future impacts usually dismissed as so much scare-mongering. It is only in more recent years that we have realised just how much effect the loss of these "wastelands" can have on our own livelihoods.
To fall back on Dicken's over-quoted opening to the Tale of Two Cities, we are currently in what are, environmentally speaking, the best and the worst of times. The cumulative effect of centuries of human impact means that we are perhaps the first generation in whose time the result of that impact has become obvious. Talk to someone of your grandparents' generation with experience in the fishing industry, and they will tell you of vast catches of fish pulled up in minutes in areas were searching for days will bring up a tiny fraction of the catch. Seafood catches such as crayfish and squid that are now widely sought were once tossed overboard as bycatch, thought only suitable for use as burley or bait. As one character says early in Frank Herbert's Dune, "We were living in a paradise for our species and didn't know it".
A number of years ago, my family went fishing for the day at the Poor Knights Islands in New Zealand. At the time, half the islands were a marine reserve, while the other half were open to recreational fishing (the reserve has since been enlarged to cover the entire area). In the area where we were sitting, just outside the reserve, the abundance of fish was something I had never seen before. Any line put down got a bite in a matter of seconds. Bits of bait tossed over the side barely even hit the water before being swallowed. Just think - once, almost the entire ocean was like this. There is a British TV programme hosted by the guy that used to be Baldrick called The Worst Jobs in History - in one episode, an explanation was given of how the Vikings used to transport ships across land barriers, rolling them across logs greased with the fat from fish. Think on how much fish that would have required, and how much must have been available to be considered for use in that manner.
We hear accounts of flocks of birds so large that they blotted out the sun. "If you simply closed your eyes and threw your spear, why, there would be something good to eat on the end of it", as someone says in Neil Gaiman's The Doll's House. Alexander Wilson observed a flight of passenger pigeons in Kentucky in 1806 for which he wrote: "If we suppose this column to have been one mile in breadth (and I believe it to have been much more) and that it moved at the rate of one mile a minute; four hours, the time it continued passing, would make its whole length two hundred and forty miles. Again supposing that each square yard of this moving body comprehended three pigeons, the square yards in the whole space, multiplied by three, would give two thousand two hundred and thirty millions, two hundred and seventy-two thousand pigeons!" (Fisher & Peterson, 1964 - italics mine). Let me repeat that - roughly two and a quarter billion birds in a single flock!
And yet, it is precisely the loss of this abundance that has allowed the environmental movement to gain the force it has today. Those concerned with preserving the environment are no longer the lone voice of Elijah crying in the wilderness, they are - or should be - all of us who wish to live our lives able to see the beauty of the world that surrounds us. Genesis claims that God gave dominion over the world to Man - therefore, the preservation of the world is man's responsibility.
If I may end on a slightly lighter note, I recently overheard a conversation that seemed to sum up all the difficulties of achieving a balance between our modern lifestyles and preserving the world around us:
PERSON 1: "You know, if it weren't for the Agricultural and Industrial Revolutions, we wouldn't have all these problems - no pollution, no global warming..."
PERSON 2: "Yeah, but we'd be living surrounded by pig shit".
REFERENCES
Fisher, J., & T. T. Peterson. 1964. The World of Birds: A comprehensie guide to general ornithology. Macdonald: London.
The Boneyard is up at microecos, this time illustrated by a good array of imaginative illustrations. Check out the Conference with Triceratops, and the Sauropods Entwined.
The Ig Nobels came out last week. For those who haven't heard of them, the Ig Nobels are intended as a spoof on the Nobel Prizes for academic achievement, and according to the official website are awarded for research that "first makes people laugh, then makes them think". I have to admit that I could probably name more Ig Nobel winners than Nobel winners - not to mention that unlike the proper Nobel prizes, the Ig Nobels do directly recognise achievements in fields like biology and mathematics*.
*There is a widespread urban myth that there is no Nobel Prize for Mathematics because Nobel's mistress left him for a mathematician. Sadly, there seems to be little direct evidence for this story.
Among this year's winners, one prize really stands out. The Peace prize was awarded to "The Air Force Wright Laboratory, Dayton, Ohio, USA, for instigating research & development on a chemical weapon -- the so-called "gay bomb" -- that will make enemy soldiers become sexually irresistible to each other". Personally, I would like to wish the researchers of the Wright Laboratory every success in their endeavour, and please could they tell me where I might purchase one (or two or three) on completion? This could be a perfect example of a military development with wide-ranging civilian uses.
I was about to suggest that, as well as expanding my own personal options, the judicious release of a few well-placed gay bombs around fundamentalist hang-outs would solve a lot of problems currently besetting society. But then I realised that probably it wouldn't.
Needless to say, not anything to do with any organism known to mankind, but a very cheesy video with a surprisingly catchy tune. I guess all I can do is ding-a-ding-dang my dang-a-long-ling-long.
While trying to answer a query from Neil on the previous post, I discovered that there was an even bigger fossil cephalopod out there than the Parapuzosia I showed you yesterday (offhand, I gave the size of Parapuzosia as 2.5 m, which is apparently not entirely correct. The actual fossil itself is around 2 m in diameter, but is missing most of the living chamber [cephalopod shells are divided into a number of successive chambers, with the actual animal only occupying the youngest chamber] - 2.5 m is an estimated size if the living chamber were intact). Cameroceras was an straight-shelled endoceratid 'nautiloid' in the early Ordovician that reached about 10 m in length, though there seems to be some uncertainty - reading between the lines, I'm guessing that we don't have an entirely intact shell for Cameroceras either, and the total size is again an estimate. But note that that length doesn't include tentacles!
The picture at the top of the post comes from here, but note that the site linked is obviously a collection of pictures taken from elsewhere (a number of them even have the unmistakeable style of Palaeos.org's own Stanton Fink) and I don't know the original source* (Update: See in the comments for the apparent original site). The larger specimen on the left is apparently Cameroceras and looks to be about the right size. The smaller specimen on the right is meant to be the closely related Endoceras - Palaeos gives a length of about four metres for this critter, so the one in the picture appears a little large. The buxom wench with the rapier is, well, a buxom wench with a rapier.
*Should the original illustrator be out there, I'll be happy to correct the link. I'll also take this as a good time to remind you all that it is Catalogue of Organism's policy that any inadvertent breaches of copyright will be immediately rectified upon notification by removing the offending item.
Apparently yesterday was International Cephalopod Awareness Day. This is one of the problems of living on the other side of the world from the blogging majority - by the time I discovered that October 8 was Cephalopod Day, October 8 was, for me, pretty much over. Mind you, except for Ben D at Principles of Parsimony, Cephalopod Awareness seemed to mostly be Neocoleoid Awareness. Unfortunately, modern cephalopods are something of a fragment of their former selves. Of the three traditional subclasses, only one - the coleoids - survives in any great numbers. 'Nautiloids'* are represented by only a single living genus, the eponymous Nautilus. The third class, the ammonoids (of which ammonites are the best-known members), never made it past the end of the Cretaceous.
*The inverted commas are because Nautiloidea in the traditional sense is a paraphyletic group that contains the ancestors of the other subclasses.
But once these creatures ruled the sea. The image above (from here) is of the largest known ammonite, Parapuzosia seppenradensis, with a diameter of about 2.5 metres. That's a lot of calamari.
Oh yes, and while looking stuff up for this, I came across one of the more disturbing article titles I've seen - "Implosion of living Nautilus under increased pressure". Ick. Can you imagine the grant proposal?
After last week's fairly nominal effort at Taxon of the Week, I'm happy to report that the ecology labs are over and done with*, and I can present you with something a little more this week. Many of you will probably be aware of the existence of parasitoid** wasps - Hymenoptera that lay their eggs inside insects and other animals so that when the larvae hatch out they can devour the unfortunate host from the inside out (in some situations, you can't help but say "devour"). The most well-known examples of parasitoid wasps are the large ichneumons***, but I'll be dealing today with a different group - the micro-wasps of the Proctotrupomorpha.
*So I can stop explaining to students that their chances of having actually found a dragonfly in a pitfall trap are fairly minimal.
**Not a typo. Technically speaking, "parasitism" implies that the parasite feeds off the host without (ideally) actually killing it. "Parasitoid" Hymenoptera are referred to as such because the growth of the larva almost invariably results in the death of the host. As such, they are better described as internal predators rather than parasites. All the same, I apologise in advance for when I'm going to inevitably slip back into referring to them as parasites later on.
***Not to be confused with the mongooses also known as ichneumons. The two are easily distinguished - mongooses are much harder to fit into a collection vial.
Proctotrupomorphs are a spectacularly diverse group. The image at the top of the post from Natural History Museum shows an array of examples from only one of the component superfamilies, the Chalcidoidea. Proctotrupomorphs also include the Proctotrupoidea, Platygastroidea and Cynipoidea. Most are exceedingly small - according to the website just linked, the smallest chalcidoid (also the world's smallest insect) reaches a maximum adult size of 0.11mm. There are proctotrupomorphs with wings, there are ones without. There are species with relatively enormous 'horns' arising from the front of the abdomen that allow space for ovipositors considerably longer than the remainder of the insect (as shown above in an image from here). Most emerge from eggs or juveniles of other arthropods, but some have taken to living in galls or pollinating figs. Some are even parasitoids of other parasitic wasps. And a few are even aquatic.
A number of proctotrupomorphs exhibit what is called polyembryony. A single egg is laid within a host which then divides into a number of larvae - up to two thousand in Copidosoma floridanum. The latter species also has a remarkable characteristic in that some of the polyembryonically produced individuals, the precocious larvae, develop enlarged mandibles and seek out and destroy other larvae of the same species but from different eggs (Zhurov et al., 2004). These precocious larvae never mature and die along with the host, leaving their identical siblings (the reproductives) to emerge as adults. In another species, Encarsia formosa (shown above in a picture from Cornell University), the gift from one larva to another is even more significant, though perhaps less willing. Most E. formosa larvae are female, and develop within greenhouse white-flies. Males are much rarer, and actually have a different host - they develop as hyperparasites of the female larvae! (Askew, 1971) As with the marine fly Pontomyia, this demonstrates the dangers potentially inherent in reading morals of human society into the biology of other organisms.
In many cases, however (particularly with egg parasites), there is often no room at the inn for more than one larva - if two larvae attempt to grow within the one host, food supplies would be exhausted before either could complete development. Therefore, most parasitic wasps have measures to prevent competition within the host. As already mentioned for Copidosoma, larvae may kill each other off within the host. There are a number of cases where development of supernumerary larvae halts terminally once one has hatched out or pupated (Askew, 1971), though the mechanisms of this termination may be unclear. Some species act to prevent supernumerary oviposition from happening at all. Trissolcus basalis (image above from SARE) is a parasite of shield bug eggs. After the female has laid within an egg, she scratches the ovipositor over the cap of the egg in a figure-eight movement to leave a mark indicating that the egg has already been parasitised. As a contrast to all this, though, Tetrastichus giffardianus is an obligate superparasite of the fruit fly Dacus cucurbitae. Larvae of T. giffardianus can only avoid encapsulation* by the host if said host has already been parasitised by another wasp, the braconid Opius fletcheri.
*Encapsulation is the formation of a hard capsule around the parasite larva by the host's natural defenses, which isolates and kills the parasite.
Finally, a number of proctotrupomorphs have abandoned parasitism to become herbivores. Fig wasps are a number of families of chalcidoids that lay their eggs within fig flowers. Fig flowers are produced entirely enclosed within an immature fig, and can only be accessed by a single small hole in the fig. The female wasp crawls within the fig and lays her eggs in the flowers. The hatching larvae feed on the inside of the fig (though ovules are deep enough to escape the depredations of the larvae) before maturing. Once mature, they mate within the fig, and the males chew an exit path for the females before expiring without dispersing. The females become covered in pollen as they escape the fig (some species apparently actively collect pollen into special pockets), which they carry to the fig they will lay in. Figweb is a website with all the information on the fig-wasp interaction you could possibly want, as well as some pretty good images.
REFERENCES
Askew, R. R. 1971. Parasitic Insects. Heinemann Educational Books: London.
The newest edition of the Boneyard is up at Fish Feet, so check it out. And am I allowed a little smarminess that Kevin Z's and my conjoint posts are at the top of the list? Yes, I know that it doesn't have any real significance, but I'm scratching for primacy wherever I get it.
I'm afraid that today's "Taxon of the Week" must needs be a short one. I'm tutoring a lab course on invertebrate surveying this week, so I don't have the time to write an extensive post. I can only give you a whirlwind introduction to the lynx spiders of the family Oxyopidae (image above from Wikimedia).
Oxyopidae are one of the families of hunting spiders - that is, rather than building a web to catche prey in, they actively hunt for small insects. The name "lynx spider" is apparently supposed to refer to their sharp eyesight, though there seems to be some doubt as to just how sharp their eyesight is compared to, for instance, the jumping spiders of the Salticidae. Still, like other families of hunting spiders, Oxyopidae have all of their eyes directed more or less forward, and a sharp downwards bend to the front of the prosoma means that the four central eyes are looking straight ahead, as shown spectacularly well in the picture above from Ed Nieuwenhuys. In both the pictures above, if you look closely you may also make out the long spiny hairs sticking out at right angles from the legs that also seem to be characteristic of this family.
While they may not build webs for catching prey, female lynx spiders do use silk to protect their eggs, which they stand guard over until the eggs are well-developed.
The Canellales are a small order of flowering trees and shrubs, most of which are found in the southern continents though some species reach as far north as Florida and Indonesia. Two families are included in Canellales, the Canellaceae and Winteraceae. Canellaceae is found in the Ethiopian and Neotropical biozones, while Winteraceae is Australasian, Malesian and Neotropical (the image at left is of Drimys winteri [Winteraceae], and comes from Flora Chilena).
One feature that Canellaceae and Winteraceae share in common is the notable production of aromatic oils by members of both families. Canella alba (shown here in an illustration from Wikipedia) was transported from South America to Europe as "white cinnamon", and its bark is used in much the same way as cinnamon. The leaves of horopito (Pseudowintera colorata), a small tree found in New Zealand, were used as a condiment, as are those of Tasmanian pepper (Tasmannia lanceolata). I can personally vouch for the edibility of horopito - it has a strong peppery taste, similar to nasturtium but far stronger.
And the dragonfly? While you may be familiar with dragonflies as master aerialists, they begin their lives as aquatic hunters. As such, they are far more likely to be found in amber as nymphs rather than adults (image from CalPhotos, © 2004 William Leonard).
