TJ got it all wrong

If only we held these truths to be self-evident.

Scallops...it's what's for dinner

Having a brother who works for the National Marine Fisheries Observer Program definitely has its perks. Last night I cooked up scallops that were caught from the Nantucket Lighthouseship Area (NLSA) of George's Bank.

This area is a heavily managed and is only open to scallopers on occasion. It was opened this summer for a brief period of time and my brother was given some of the catch. Actually, I believe his roommate, one of the observers, was given the scallops, but, in any case, some of the scallops made their way to my brother and then he passed some on to me.



So, I cooked em up last night. Nothing fancy - just a simple pan sear in olive oil and served over some lemon orzo and with a glass of Gewürztraminer (note: the photo above is not my dinner, but an image I plundered from the web) . Now, I am by no means a scallop aficionado, but those were some tasty molluscs. Not sure how many pounds of scallops they pulled out of the area, but I'm glad to have gotten a few. Hope they didn't do too much damage while they were there...

I realize now that this post is on the opposite side of the "George's Bank shellfish" fence than one I posted a while back. Seems hypocritical. Probably is. All I can say is that I'm just going to have to trust that the National Marine Fisheries Service knows what they're doing (my brother works with them, right?) and if they say it is OK to open up NLSA to scallopers, then it's OK for me to eat those scallops. Did I mention they were real tasty?

Scientology = Science Fiction

Vinny Barbarino and Maverick won't be happy with this one, but it looks like their beloved Church of Scientology may stand trial for fraud and extortion after a 10-year Belgian investigation concluded that they should be labeled as a criminal organization.

If only this were a sign of things to come. Which group should we go after next?

All things Spined and Spineless

I'm still working on getting my sea photos up. In the meantime, here are two carnivals for you:

the Circus of the Spineless is ready over at Naturalist Notebook

Tangled Bank #87 is up over at Balancing Life

Happy Reading!

Green flash at last

Back on land after a quick, but extremely good time on board the SSV Corwith Cramer. I have tons of pictures and will post some of them with a recap of the experience early next week.

For now though, I wanted to share that I finally saw the elusive green flash at sunrise Wed. morning while on dawn watch (more on that later too). For those who don't know about the green flash, it's a rare optical phenomenon (a small, brief, green flash of light on the horizon, "on top of" the setting/rising sun) that occurs the instant before sunrise or after sunset. It is best viewed where there is a clear, straight horizon, so it mostly associated with sunrises and sunsets over the ocean.

The green flash occurs because the sun's rays are refracted by the earth's atmosphere, separating the light into its spectral colors. When the sun is below the horizon, the shorter, blue wavelengths tend to bend more and get scattered before they reach an observer's eyes, thus there is no blue flash. The longer red and orange wavelengths bend less and do not scatter, but by the time they reach an observer's eyes the sun is just above the horizon and so get washed out by the sun's own brilliance, thus there is no "red flash". Green light waves sit in the middle of the spectrum and are refracted at a good angle and just the right time so that they reach an observer's eyes without being overwhelmed by the sun itself. Thus, under appropriate conditions, the observer sees a green flash.

I have well over a 1000 hours at sea and until this week had never seen a green flash. Some people deny its very existence because they've never seen it no matter how long they've spend on the ocean. Seeing this brief, but brilliant emerald green flash was certainly one of the highlights on my trip. I was in the right place, at the right time, under the right conditions. Definitely worth the lack of sleep.

Stay tuned for more details about the whole trip...I think I'm going to go sleep for a few days now.

---

UPDATE 8/31/07 - A reader, Priscilla B. from South Africa, emailed me about how the San people of South Africa call the Green Flash the Green Python and believe it to bring good fortune to those who see it. Apparently, I was supposed to make a wish when I saw it, but alas, I was too excited about actually seeing it to wish for anything, like world peace, universal health care, or a bitchin' 72" plasma, HD TV. Maybe next time.

Down to the sea

Avast ye landlubbers. If ye be needin' me, ye be out o' luck for I be ridin' on the se'en seas. In the meantime, keep your scurvy hands off me treasure. I be countin' it when I return.

Sea Fever

I must go down to the seas again, to the lonely sea and the sky,
And all I ask is a tall ship and a star to steer her by;
And the wheel's kick and the wind's song and the white sail's shaking,
And a gray mist on the sea's face, and a gray dawn breaking.

the SSV Westward

So wrote John Masefield around the turn of the 19th 20th century. And to me (and countless others I am sure) it still rings true to this day.

It's hard to put into words, but the ocean has a power over me. I've always enjoyed the ocean in all its mystery and power and wondrous life. I grew up spending summers exploring the beaches and jetties of Cape Cod, collecting "mermaid's purses", whelk egg cases, scallop shells, and sea glass, searching for hermit and sand crabs, picking helpless periwinkles and dog whelks off the rocks, and shining flashlights into the night waters looking for blue crab and comb jellies and pipefish. I tried fishing for blues and stripers, but was never very good at that (apparently my brother, Carl, got all the fish-catching genes). Though I did catch my fair share of spider crabs.

For all that though, most of my connection to the sea was shore-based. Sure, I went out on my uncle's Boston Whaler on occasion (the best was going out to Monomoy), but really never spent that much time on the water and never more than a few miles from shore. All that changed however in my junior year at Bowdoin when I had the opportunity to take part in Sea Education Association's SEA Semester. It was during that experience that I contracted Masefield's sea fever.

Instead of going into all the salty details here, I'll send you over to the website I designed to celebrate my and my shipmates' experience. (don't laugh when you click over there - it was the first website I ever put together - 10 or so years ago - no digital cameras, no CSS, no Photoshop - and though I keep saying I am going to redo or delete it, I can't bring myself to do it).

On top of the science of the ocean and of sailing, SEA Semester teaches you more about teamwork, leadership, and your strengths and weaknesses than any other experience I've encountered - you deal with real problems in real weather in real seas. Torn mains'l in the middle of a squall in the middle of the night? Work together and deal with it. Seasick in twenty-foot seas? Help each other out and deal with it. One of your watch members not pulling their weight? Figure out how to motivate them, teach them, encourage them or deal with the fact that you're just going to have to move forward without their help.

Ever since my SEA experience, I've jumped at any feasible opportunity to get back on a sailing ship - afternoon sails at SEA alumni events, my wife's and my honeymoon on the Grace Bailey, our Galapagos adventure on the Sea Cloud. Why am I posting about all this now? Because in a couple of weeks, I'll be rejoining SEA for a 4-day cruise on the SSV Corwith Cramer and that sea fever is flaring up again.

I imagine it won't be nearly the experience my original trip was - it's only a four day "Colleagues Cruise" - but I'm counting the days till I climb aboard (even if it's not on the Westward, which was retired a few years back). I plan on bringing my camera (digital now!) and will share my photos when I get back.

Yes, I am a pirate. Born 200 years too late.

She takes after her dad

Today is "Pirate Day" at my daughter's daycare.

I think this is the Book of the Day.

(BTW she does a great "Arrrrrrrr". It brings tears to this old salt's eyes.)

That'll teach you to mess with my heirloom tomato!

One of the joys of my summer is growing our own tomatoes (actually, growing our own tomatoes, cucumbers, zucchini, lettuce,...). This year, my dad bought us an heirloom 'Brandywine' tomato. We planted it along with the rest of our vegetables and have watched it flower and start to produce a number of robust fruit. It looked like many more flowers were on the way and so I was anticipating a bumper crop. But now, it looks like I'll be lucky to salvage the four fruits currently on the vine.

We have a tomato worm in our midst. Or at least, we did.

I hadn't been outside to check on the garden in the past few days, so I didn't know we had a Manduca quinquemaculata larvae munching away on our prized tomato plant. When I went out this evening to water, here's what I saw:


The entire top half of our 'Brandywine' was completely defoliated. I'd seen tomato worms before, so I knew what to look for - a large, green, and, admittedly, cool-looking caterpillar - so large and cool in fact that people's first reaction to them is usually, "Wow". Well, sure enough, there it was hanging onto a leaf just at the base of the damaged area - the bugger was working its way down the plant, towards the ripening fruit.

But, actually, this one wasn't really moving. In fact, it wasn't really doing anything. Just hanging there underneath a leaf. Not only that, but it looked different than the ones I've seen before. What are all those white things?


On closer examination, I had a pretty good idea what it was, at least in general. I'd run across this kind of thing in grad school, studying yucca moths (a tale for another day). Looks like our tomato worm had a bad case of the parasitoids. If I had to guess, I'd say some female wasp came by and laid her eggs inside the caterpillar. Once the eggs hatched, the wasp larvae ate their way out of the caterpillar to pupate, forming these white cocoons. Gross? Sure, but cool too.


A quick search on Google confirms it. Specifically, some species of braconid wasp appears to have parasitized (parasitoidized? parasitoided?) the moth larvae (or perhaps, even cooler, the moth eggs). The tomato worm is decidedly dead now - nothing more than a tomato plant ornament. An ornament housing hundreds of developing wasps that is.


So what do I do now? Well, I could remove the offending caterpillar carcass. But the caterpillar is no longer threatening my heirloom crop. So, I think I'll leave it be and wait for the wasps to emerge. If I'm lucky, I'll be able to get some photos. At the very least, I've got my very own biological pest control system in place. Tomato worms beware!

addendum: August 6th - After a weekend away, I went outside today to check if the wasps were emerging and found that the entire tomato worm carcass had disappeared. It, and the wasp cocoons, were just gone. I checked the ground around the tomato plant, thinking the caterpillar and passengers had succumbed to the force of gravity, but, alas, it was no where to be found. Not sure what could have happened to it - could some other critter have eaten it? In any case, there will be no photos of emerging Hymenoptera. :(

Long-term rainforest study in danger

Of all the ironic things...

It looks like one of the world's watershed ecological experiments is in danger of succumbing to the pressures it was designed to study. The Biological Dynamics of Forest Fragmentation Project (formerly the Minimum Critical Size of Ecosystems Project) is a large-scale field experiment on the effects of habitat fragmentation that has been in existence since the late 1970s. This study, initiated by Dr. Thomas Lovejoy, essentially took a swath of Amazon rainforest and created a patchwork of forest fragments of different sizes. The initial intent was to empirically solve the SLOSS question (Single Large or Several Small) - the question for conservation biologists of whether it is better (biodiversity-wise) to create one large reserve or many, smaller ones who's total area equaled the larger (the SLOSS argument, in turn, was influenced by another seminal work - MacArthur's and Wilson's Theory of Island Biogeography). As with any good scientific endeavor, this experiment has revealed a lot more than it originally set out to - e.g. the importance of edge effects, microhabitat changes, habitat diversity, and on and on...The work that has come out of this study has influenced countless conservation efforts and has been a cornerstone topic for teaching about environmental science, experimental design, conservation biology, and general ecology.

Unfortunately, it now seems that the experiment is in serious of danger of being destroyed by encroaching development. The population in the surrounding area has grown to the point where people are starting to spread out into the experimental area - burning some of the forest plots and raiding research camps. I suppose this sort of thing was inevitable with the rate of population growth, especially in developing countries, but it will be a sad day for science if/when such an important and innovative experiment is forced to shut down.

Astrophysics Rocks!

Sorry marine biologists, but it looks like you're not the only rock stars in the science community.

The field of astrophysics is about to usher in their very own MEGA rock star - Brian May, formerly of Queen. Apparently the 60-year old rocker has just about wrapped up his doctoral dissertation on "Radial Velocities in the Zodiacal Dust Cloud".

How many PhDs do you know of that are also world-wide musical icons? Really, who would of thought that "Fat Bottomed Girls" would be written by a physicist?

(Thanks for the link, Linda)

Tangled Bank #83

The latest edition of the Tangled Bank is now up over at Aardvarchaeology.

African elephants live in Africa for a reason

In this month's Scientific American is an article about a topic that gets my blood going whenever I read about it - the concept of Pleistocene Rewilding. For those of you who haven't heard of it, Pleistocene Rewilding is the idea that we should introduce non-native megafauna to North American ecosystems. The basic idea is that up to 10,000 years or so ago, relatives of these animals roamed North America as key cogs in the natural landscape. Then humans arrived and most of the large animals went extinct. The correlation between the extinctions and the arrival of Homo sapiens has lead to the hypothesis that humans hunted the large herbivores to the point where their populations were too low to be sustained. With a lack of large herbivores, large carnivores were also unable to survive. The Pleistocene rewilding is an attempt to reverse this Pleistocene overkill.

Lions, mammoths, camels, horses, cheetahs, and others were all found in various ecosystems throughout North America and helped shape the evolution and ecology of plants and animals still found today. For example, it is hypothesized that the pronghorn's speed evolved to help it evade American cheetahs (why else should it run over 60 mph?), and that the large seeds of the honey locust tree were eaten and dispersed by mammoths (now, the honey locust has no natural seed dispersal). Proponents of Pleistocene rewilding see North American ecosystems as "broken", missing major players. Since the missing fauna are now extinct, the idea is to use extant species as proxies. Re-wilders want to import African elephants, cheetahs, lions, and camels to restore North America to what it was (might have been?) before humans killed off the large mammals.

I first read about Pleistocene rewilding some years ago in the now-defunct journal Wild Earth. More recently, researchers at Cornell have reinvigorated the rewilding push. I think it is a monumentally bad idea. First, it's gimmicky - the article in SciAm talks about the increased tourist revenues it would bring in and even shows an illustration with a monorail in the background. If this is what you want, go to Disney's Animal Kingdom, Six Flags' Wild Safari, or the San Diego Zoo's Wild Animal Park. Second, and most important, these animals don't belong here. I'm all for the conservation and restoration of ecosystems. The reintroduction of wolves to Yellowstone was a phenomenal, watershed event. But Canis lupus used to live there - in historic times nonetheless - and still were living relatively nearby. Before zoos, African elephants NEVER lived in North America. African cheetahs NEVER lived in North America. The Dromedary Camel NEVER lived in North America. And even though the American and African lions are considered subspecies of Panthera leo I wonder how similar they truly were (isolated for at least tens of thousnads of years, living in different environments). Haven't we seen the results time and time again of introducing non-native species to ecosystems?

I might think differently about Pleistocene rewilding if we were able to actually reintroduce the Pleisotcene fauna. How great would it be to see herds of mammoths roaming around? Or the chance to see a cheetah chase down a pronghorn? Alas, unless there's some Jurassic Park technologies out there, this ain't happening.

Craig Venter up to it again

Craig Venter et al. have apparently taken a big step towards creating synthetic life - they've managed to insert the whole genome of one species of bacteria into another species of bacteria. Some people are making a big deal about it and apparently there's a good editorial in the current Nature (though I wouldn't know since Roger Williams University apparently doesn't think it important to have a subscription)

There is however a NY Times piece on it. Without knowing the details of how this whole genome insertion is carried out, I must say that this technique doesn't seem particularly mind-blowing - we've been putting genes of one species into the cells of other species for decades (and microbes and viruses have probably been doing it billions of years). I would have thought that this sort of thing was inevitable and the next logical step in genetic engineering. In fact, now that I think about it, this isn't really different than cloning...

...I've just sat here for a few minutes thinking about how this new breakthrough is different from the cloning techniques currently being used. They seem fundamentally the same to me. If anyone out there knows otherwise, please tell me what I am missing (like I said, I haven't read up on Venter's method and the obstacles that had to be maneuvered along the way).

In any case, all we need to do now is to create a synthetic genome. How hard could that be?

Friday Science: How the kapok tree crossed the Atlantic

One of the long-standing hypotheses in biogeography is that sub-Sarahan and Neotropical rainforests have similar plant communities because Africa and South America were joined together previous to their separation some 120 million years ago. For most of their geographic history there was no oceanic barrier between these continents so organisms were free to disperse from one to the other as easily as you could walk from Rhode Island to Massachusetts (or from Rhode Island to California if you had the time and the legs). Therefore, the flora and fauna of these two land masses were remarkably similar to one another when plate tectonics began pulling the two apart. Over the past 100 million years or so species in both places continued to evolve independent of one another, but similarities remain because both continents started with a subset of the same organisms.

Within the angiosperms, Africa and South America share over 100 genera and nearly 100 species. The most common explanation for this pattern is vicariance - the geographic splitting of a population (in this case, the emergence of the Atlantic Ocean as Africa and South America "floated away" from each other) . However, a new study has tested this hypothesis and, for the Kapok tree at least, finds the vicariance model insufficient. Instead, it appears that this species is able to cross the Atlantic ocean.

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First some antural history. The Kapok, Ceiba pentandra, is a canopy-emergent, tropical tree that can grow up to 70m (230ft) with a trunk 3m (10ft) wide. The flowers atttract bat and moth pollinators with copious nectar production. The fruits contain large amounts of cotton-like fibers that are used to disperse the small seeds through the air (similar to milkweed or dandelion dispersal). So even though the distance between Africa and South America is great, C. pentandra at least has a plausible mechanism for cross-Atlantic dispersal. The question then is, is C. pentandra found both in the Amazon and in western Africa because it was already widely spread across both continents before they separated (the vicariance hypothesis) or because it was originally found in only one location and then dispersed across the Atlantic to the other?

Ceiba pentandra clockwise from left (1) emergent Amazon tree with a person beside the characteristic buttress trunk (photo credit R. Gribel); (2) dehiscing fruit with kapok (photo credit A. Gentry); (3) seed enveloped in kapok (photo credit C. Dick). (from Dick et al. 2007)

To answer that question, the authors used the molecular clock method. Briefly, the molecular clock method assumes that genetic mutations occur at a relatively constant rate. When two populations become separated, their genomes are free to mutate independently from one another. The longer two populations are separated, the more different we expect their genomes to be (each has acquired their own, different mutations). If the populations are not entirely separated, gene flow, the dispersal of genetic information, will homogenize the gene pool and the two sets of genomes will be relatively similar. If mutation rate is constant (and we know what it is) and we know how different two sets of DNA are, we can make a simple calculation of when the two groups became separated from one another. For example, if we know that one mutation arises every 1,000 years in a particular DNA sequence and two sets of this DNA sequence are different at 50 nucleotide locations, we know that these two groups separated from one another 25,000 years ago (we assume that each group has accrued 1/2 of the total differences - in this case each group has had enough time for 25 mutations to arise). Of course, it is much more complicated than this - sometimes the same mutation can occur independently in both lineages or a particular nucleotide may mutate and then "back-mutate" to its original (in both cases we wouldn't recognize any mutations when in fact there have been two), but the basic concept remains the same.

For this study, leaf tissue was collected from C. pentandra individuals from Western Africa, Central America, South America, and Puerto Rico. From these samples, stretches of nuclear and chloroplast non-coding DNA were sequenced. The nuclear sequences that were sequenced were for a subset of the internal transcribed spacers (ITS) found between the genes that encode ribosomal subunits. The sequenced chloroplast DNA was from intergenic spacers found between some photosynthesis genes. Basically, these areas are used for two main reasons:

1. They are highly variable
They do not encode any functional protein so the sequences are essentially freed from the pressures of natural selection. Since there are no selective pressures on them, mutations that arise in the sequence are not weeded out and over time the number of mutations build up. Thus, two groups of organisms that have been separated will build up different sets of mutations in these regions relatively quickly, making these regions useful, using the molecular clock method described above, when looking at phylogenetic relationships of closely related groups (usually at the species level or, as in this case, at the population level within a species).

2. They are easily located
The spacers are found flanking very important genes - those that are responsible for making ribosomes and for carrying out photosynthesis. These important genes are generally less variable as mutations in their sequences tend to be functionally disruptive and are thus naturally selected out. The sequences for these genes are therefore generally stable and are "easy" to locate in genomes. Biologists use these highly-conserved, known sequences as starting and ending points for locating the more variable, unknown sequences of the spacers between them.

Once the authors sequenced the spacers, they could examine how the sequences differed across the geographic range of the species. By using an amalgam of previously published values of mutation rates, and erring on the conservative side, the authors hypothesis was that if African and Neotropical populations of C. pentandra have been isolated since the breakup of Gondwana the ITS nucleotide sequences should be at least 7% different and the chloroplast spacers should be at least 19% different.

Those are the expected values under the vicariance hypothesis. When the authors tested this hypothesis, they observed that the ITS sequence divergence was less than 0.4% and that there was essentially no divergence in the chloroplast sequences (the only variation was found in one cluster in western Ecuador). The observed values were significantly lower than the expected values. This means that the African and Neotropical populations have not been isolated for 100 million years - kapok trees did not cross the Atlantic not as passengers on the drifting continents. The low level of genetic divergence between the geographic areas suggests that more recent (and thus long-range) dispersal is responsible for the kapok tree's geographic pattern. The authors suggest that cottony seed fibers could allow the seeds to be transported long distances via wind currents. Alternatively (or contemporaneously) floating kapok seeds may be dispersed via ocean currents.

But where did the great kapok tree originate? Africa or South America? Most cross-Atlantic dispersals are assumed to have been westerly - from Africa to the New World. However, the authors suggest that C. pentandra did it the other way - though, based solely on the suggestions in this paper, I am not convinced (whatever that is worth!). Regardless of which direction the kapok tree went, it is clear that it crossed the Atlantic relatively recently via seed dispersal, not through an ancient vicariance event.

Citation: CHRISTOPHER W. DICK, ELDREDGE BERMINGHAM, MARISTERRA R. LEMES, ROGERIO GRIBEL (2007) Extreme long-distance dispersal of the lowland tropical rainforest tree Ceiba pentandra L. (Malvaceae) in Africa and the Neotropics. Molecular Ecology (OnlineEarly Articles). doi:10.1111/j.1365-294X.2007.03341.x

Worst Jobs in Science?

Popular Science has just released their annual bottom-10 "Worst Jobs in Science" report. While I agree that some of these jobs can't be good - like the Elephant Vasectomist - some are actually pretty cool if you ask me - like the Forensic Entomologist (certainly grisly, but a damn brilliant use of science). Still others I wouldn't give "job" status to - Gravity Test Subject? C'mon.

What I want to know most of all though is who the moron was who decided that Oceanographer should be on this list. As far as I can tell, most people, including non-scientists, would say that being an Oceanographer is on the list of coolest jobs in science. But maybe it's my own marine bias. Have the guys over at Deep Sea News seen this yet? Not sure how they're gonna like being lumped in with the "Garbologists"

(thanks Jeff for the link!)

Don't go a shellfishin' on George's Bank

My brother, who works for the federal fisheries observer program, sent me some info regarding a pretty impressive "red tide" event currently occurring on George's Bank. Both "Red tides" and George's Bank are rather interesting topics, so I thought I'd take the time to write something about them both. You probably won't find shellfish from George's Bank at your local fishmonger, but if you do, I wouldn't eat them at this point.

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George's Bank
George's Bank is a shallow shoal in the North Atlantic located approximately 100 km off the coast of Massachusetts. GB is a very productive area (or at least, used to be) and was one of the most important areas for New England and Canadian fishermen. Essentially, this area is so productive because it sits where the cold, nutrient-rich Labrador current meets the warmer Gulf stream. Combine this with its shallow waters and you end up with an ideal environment for phytoplankton, which in turns makes George's Bank an ideal breeding and feeding environment for cod, haddock, herring, flounder, lobster, scallops, and clams. Combine lots of fish and shellfish with proximity to land and you have an ideal environment for fishermen (not to mention a veritable cornucopia of seabirds and marine mammals). GB is so shallow and so close to the mainland that it was part of the mainland during the last glaciation event, then became "George's Island" as seas began to rise, before finally succumbing to the sea 6,000 yrs ago. Fishermen sometimes dreg up interesting fossils from GB.

(click image to enlarge)
In addition to the shallow waters and mixing of currents, GB has a rather complex and heterogeneous sea floor, including a number of small "canyons", which increases GB's appeal to an even greater range of biodiversity.

Verrazano discovered GB in the early 1500s (though Basque fishermen may have been fishing there since 1000 AD - there was a Basque fishing fleet stationed in Newfoundland) and the entire western North Atlantic become a hotbed of fishing, particularly for cod. You've probably heard the off-quoted aphorism that cod were so plentiful you could walk to shore on their backs.

GB and the western North Atlantic were so important (and profitable) that the U.S. and Canada had to appeal to the International Court in The Hague in 1984 to step in and set international boundaries where their EEZ's overlapped. Fishermen and officials from both countries still squabble over this "Hague Line", which cuts through GB (most of GB falls within the U.S. EEZ; only the eastern edge is in Canadian waters).

Over the years, increased fishing effort and increasingly efficient and technologically advanced fishing gear decimated the fisheries on GB, effectively causing their collapse in the late 80s and early 90s. in 1993 Canada placed a moratorium on cod fishing and placed strict regulations on other GB fisheries. In 1994 the U.S. closed most of GB to commercial fishing. In 1995, this ban was extended indefinitely.

Red Tides
First off, "red tides" are not tides, they're algal blooms. Second, not all "red tides" are harmful and not all harmful algae cause "red tides". So, the more appropriate and scientifically-acceptable term is not "red tide", but "harmful algal bloom", or HAB. HABs are defined as an event when toxic-producing algae populations increase to the point that they become hazardous. For some species of algae, this requires an enormous population explosion, but for other, more toxic species, even a few cells per liter would be considered an HAB.

In the western North Atlantic, most HABs are the result of the dinoflagellate Alexandrium fundyense - incidently, these HABs are also "red tides". These critters produce neurotoxins, such as saxitoxin. Saxitoxin selectively blocks cellular sodium channels, which are necessary for creating nerve impulses. Blocking sodium channels thus prevents nerve impulses. Since nerve impulses control our muscles, saxitoxin can, in severe cases, cause paralysis. Naturally then, HABs of Alexandrium fundyense are responsible for Paralytic Shellfish Poisoning (PSP).

PSP occurs because shellfish are natural filters. They take in seawater, pass it through their gills, trapping microscopic organisms that they then digest. During blooms of Alexandrium fundyense shellfish in the area eat the dinoflagellates, but end up storing the saxitoxins in their tissue. Luckily for shellfish, saxitoxins have no effect on them. Unluckily for us (and any other vertebrate that decides to dine on the "infected" shellfish), the toxins enter our bodies when we eat the shellfish, block our sodium channels, and cause PSP. Symptoms of PSP? How about "nausea, vomiting, diarrhea, abdominal pain, and tingling or burning lips, gums, tongue, face, neck, arms, legs, and toes. Shortness of breath, dry mouth, a choking feeling, confused or slurred speech, and lack of coordination are also possible."¹ In the most severe cases paralysis sets in and respiratory failure and death may follow.

HABs on GB:
As if the fisheries on George's Bank haven't been hit hard enough by depleted stocks, it turn out that there is a rather severe Alexandrium bloom sitting right on top of the shoal. The R/V Endeavor has recently completed a survey of the Gulf of Maine and Georges Bank and has found an HAB only on GB.

(click image to enlarge)
Superimposing the survey data onto the North Atlantic chart, you can see how the HAB is right on top of GB (note thre lack of data from the eastern, Canadian end of GB):
(click image to enlarge)
The worst section of the HAB has over 13,000 Alexandrium cells per liter of seawater, more than enough to cause PSP.

So, ignore those "George's Bank Quahogs" on sale at your local neighborhood food mart. Unless of course you think your diet is lacking in saxitoxins. (Actually, if you do see "George's Bank Quahogs" for sale, you best notify your nearest employee of the National Marine Fisheries Service - shellfishing on GB has been closed for more than a decade).

Tangled Bank #81

Check out the newest installment of the Tangled Bank - some great posts as always.

Friday Science: from Parasite to Mutualist

This is the first in a, hopefully, weekly bi-weekly occasional series of posts in which I will summarize/discuss some new peer-reviewed research that I find interesting. My post on synthetic estrogen and extinction started me thinking that this would be a good addition here. In attempting this, I am in no way suggesting that I am an expert in any of the topics I will be posting, only that I find them interesting and that I hope to be able to present the material in a "chewable" form. I'll also try to restrict my summaries to articles available via open access. Wish me luck.

This week's article that caught my attention is from PLoS Biology and deals with the evolution of parasites into benign or even beneficial organisms. In particular, the researchers show that over approximately 20 years, a particular strain of Wolbachia has evolved in a manner such that it now causes infected female flies (Drosophila simulans) to lay more eggs. Here we have a parasite that used to cause reproductive harm evolving into a "parasite" that helps fly reproduction. Even better, this phenomenon is exactly what evolutionary theory predicts should have happened.

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Wolbachia is a bacterium that infects all sorts of invertebrates, particularly insects. Individuals that are infected with Wolbachia show decreased reproductive success - partly through a process called cytoplasmic incompatibility (CI). CI basically means that the gametes of an infected individual are incapable of (or less successful in) fusing with the gametes of uninfected individuals. Thus, infected females can only breed with infected males.

Another interesting thing about Wolbachia is that unlike most transmissible parasites, it is passed only from mother to offspring via infected eggs. Such "vertical transmission", combined with CI, can cause a rather rapid spread of the parasite within a population. And this is exactly what has been seen in the population of flies in this study. In the mid-1980s Wolbachia-induced CI was discovered in a population of D. simulans in southern California. Since that time, the Wolbachia infestation has spread north through California and is "now pervasive throughout most North American populations of D. simulans."

Notice though that there are two conflicting aspects of Wolbachia infection: 1) Wolbachia is only passed from mother to egg, yet 2) Wolbachia infections cause females to lay fewer eggs. Evolutionaryly speaking, this set-up is not in the bacteria's (nor the fly's) best interest. Under this type of vertically-transmitted infection scenario, evolutionary theory predicts that the parasite will become less virulent harmful over time. At worst, the parasite should evolve so as to have no affect on female fecundity (just hitching a ride on the eggs). At best, theory predicts that the parasite should come around 180° and become a mutualistic partner by actually increasing female reproduction.

Sure enough, 20 years after the initial "outbreak", Wolbachia infection in D. simulans now has a positive effect on female fecundity. Originally, infected females laid 20% fewer eggs compared to uninfected females. Now infected females lay 10% more eggs than uninfected females. The authors also point out that CI levels and transmission rates have stayed constant, so the fecundity effect is not a result of depressed CI or bacterial transmission.

So, is this change in fecundity an effect of an evolving bacterium or an evolving host (or both)? To test this, the authors essentially infected flies with the old strain of the Wolbachia (that had been kept in culture for the past 20 years?) and found that the fecundity advantage disappeared. Thus, the current fecundity effect appears to be mostly a result of the evolution of the bacteria.

Ah, but what if the current Wolbachia strain that is causing the fecundity advantage is actually a more recently introduced strain and not the direct evolutionary lineage of the old strain? To examine this possibility, the authors tested the CI levels between the current strain and the old strain. If they were two different strains, flies infected with one would be reproductively incompatible with flies infected with the other. This was not the case, supporting the idea that the new Wolbachia strain is an "evolved version" of the old strain.

I found this study fascinating for a number of reasons. First, the design and the thoroughness of the experiments seem flawless to me (given, of course, that I am neither a fly biologist nor a bacteriologist) - the authors seem to have covered all the appropriate ground, showing that indeed the effects they witnessed are the result of bacterial evolution. Secondly, the evolution of this strain of Wolbachia is a great example of how quickly natural selection can work given conducive conditions. Thirdly, this paper shows just how testable (and accurate) predictions from evolutionary theory are.

Based on what is known about evolution by natural selection, coupled with a firm understanding of the biology behind a given natural system, we are able to make hypotheses, design experiments (and/or make the necessary observations to test these hypothesis, and come to scientifically tenable conclusions.

What more could you ask for?

Citation: Weeks AR, Turelli M, Harcombe WR, Reynolds KT, Hoffmann AA (2007) From Parasite to Mutualist: Rapid Evolution of Wolbachia in Natural Populations of Drosophila. PLoS Biol 5(5): e114 doi:10.1371/journal.pbio.0050114

The perfect gift

How great is this? James Watson, co-discoverer of DNA the structure of DNA, was presented with the genetic sequence of his very own genome.

It only cost $1 million. Wonder if I should ask for mine for Father's Day...

(thanks for the link, Linda)