Wednesday, February 29, 2012

Send the navy

A few weeks ago I wrote about the incursion of a Japanese whaling vessel into Australian waters. Now the Yushin Maru 3, a ship from the Japanese whaling fleet in the Southern Ocean, has again entered Australian waters. Maybe it's time the Australian Government enforced it's policy of not allowing whaling vessels to pass through the exclusive economic zone. The whalers don't seem to be listening to the warnings. It would put a smile on my face if the Australian Customs and Boarder Protection Service confiscated and scuttled the Yushin Maru 3.

Tuesday, February 28, 2012

Flowering plants in the sea part 2 - Sex

A while ago I wrote about seagrass and some of the interesting adaptations that they have to the low light levels in the sea. Another important part of their biology that had to adapt to conditions in the marine environment were their flowers. Because seagrasses moved into the sea on multiple occasions there are several strategies that they use for pollination.

The most recent entrants to the sea, in the genus Enhalus, have flowers that are pollinated in air. Male flowers break away from the plant and fertilise the female flowers, which are attached to the plant by long coiled tendrils. Unlike many other types of seagrass, the female flowers are easily recognised as flowers.

The floating female flower of Enhalus acroides. The small white polystyrene bead-like objects are the male flowers (photo The Tide Chaser). 
A close up of the male flowers of E. acroides (photo Urban Forrest).

Pollination is important in terrestrial plant populations, but was thought not to be terribly important in seagrass populations because they are mostly clonal and populations expand by vegetative growth. Indeed, expansion via the rhizomes can produce large seagrass meadows that contain genetically very similar plants.

The female flower of surfgrass, Phyllospadix torreyi  (photo Carol Blanchette).
The flower of eelgrass, Zostera marina (photo Jan Holmes)

Seagrasses also invest a lot of energy into sexual reproduction. This is curious because it takes energy away from vegetative growth, which is primarily how meadows are maintained and recover from damage. Indeed, sex seems paradoxical in species, like segrasses, that can produce offspring without sex.

One potential reason for the large investment in sexual reproduction is seagrasses is long range dispersal. Vegetative growth expands meadows, and can do so quite rapidly, but it can't jump large gaps and establish new populations or spread genes to new locations. Dispersing pollen and seeds may be able to accomplish this.

The pollen of seagrasses is large and elongate (relative to other flowering plants), and consequently, poorly suited to long distance travel. Although estimates are rare, some studies suggest that pollen may only be able to travel a few tens of meters. Pollination, therefore, is likely to occur at local scales in most seagrasses.

The fruit of eelgrass, Zostera marina. Each fruit contains a single seed (photo Jan Holmes).
The seeds of seagrasses have the potential to disperse genes much further than the pollen and establish new meadows. Seagrass seeds, or the structures that carry the seeds (e.g. fruit) have a variety of adaptations for dispersal that effect how far the seeds will travel before they start a new population. Probably the most important factor determining dispersal distance.

The seeds themselves are usually neutrally or negatively buoyant because they must eventually reach the sediment to grow into an adult plant. The structures that carry the seeds, however, are often floating and can transport the seeds considerable distances (up to several hundred kilometers). Some seagrasses are even able to transport their seeds in the insides of herbivores like dugongs and turtles.

Dugongs are mostly interesting because they transport seagrass seeds.
Another reason that sex is important for seagrasses is the resilience of populations to disturbance. We know that communities with a greater diversity of species often have an enhanced ability to resist and recover from disturbances. Interestingly, seagrass patches that have higher genetic diversity show a greater resistance to damage by herbivores and recover faster after damage. Although, the faster recovery may be due to the lower levels of damage in more diverse patches than faster rates of vegetative growth.

Further reading:

1 G. A. Kendrick et al. (2012). The Central Role of Dispersal in the Maintenance and Persistence of Seagrass Populations BioScience, vol 62(1): 56-65

2 J. D. Ackerman (2006). Sexual Reproduction of Seagrasses: Pollination in the Marine Context. In: Seagrasses: Biology, Ecology and Conservation (A. W. D. Larkum, R. J. Orth, C. Duarte Eds.). 89 - 109

3 R. J. Orth et al. (2006) Ecology of Seagrass Seeds and Dispersal Strategies. In: Seagrasses: Biology, Ecology and Conservation (A. W. D. Larkum, R. J. Orth, C. Duarte Eds.). 111 - 133

4 A. R. Hughes and J. J. Stachowicz (2004)Genetic diversity enhances the resistance of a seagrass ecosystem to disturbance. PNAS vol 101(24): 8998 - 9002.

Saturday, February 25, 2012

They came from the deep

Polychaetes are annelid worms that are mostly found in marine environments. Earth worms are annelids too, but they're oligochaetes. The oligochaetes are mostly found in freshwater and terrestrial systems.

The major differences between polychaetes and oligochaetes that can be used to distinguish them are the parapodia and chaetae. Polychaetes have them and oligochaetes don't. However, some aquatic oligochaetes have structures that look very similar to parapodia, and the parapodia and chaetae are hard to find on some polychaetes. There are exceptions to every rule!
Cross section of a polychaete showing a typical body plan.

Parapodia are fleshy outgrowths that are generally used for locomotion. In polychaetes the parapodia divide into upper and lower lobes. The upper lobe is called the notopod (pl. notopodia) and the lower lobe is called the neuropod (pl. neuropodia). Out of the lobes grow the chaetae, which are bristle-like in appearance. It's the many chaetae that give polychaetes their name.

Recently, the Telegraph newspaper published some electron micrograph images of some polychaetes that were collected from a hydrothermal vent. They make the already alien appearance of the worms even more strange. The false colour (EM images are black and white) does not help things.

Portrait of a polychaete. I'm not sure, but I think it's a Nereid polychaete (rag worm).

Another polychaete. This one is a Polynoid polychaete (scale worm). I wonder if it's predatory?
The reporting of these images has been pretty poor. Stories I have seen make it sound like these worms are only found in the deep-sea, which is not true. And that they eat the bacteria at hydrothermal vents, which is also not true. The images are of worms collected from deep hydrothermal vents, but there are many shallow water examples of both rag worms and scale worms. And both groups are generally predatory.

Rag worms and scale worms feed by rapidly everting their pharynx, which has some hardened mandibles attached. Prey that are caught in the jaws are dragged back into the mouth. In the upper image the rag worm still has its jaws hidden on the inside, while the scale worm in the lower image has partially exposed its jaws.

The everted jaws of Perinereis cultrifera, a Nereid polychaete (photo estran 22)
The other thing that was reported badly in some places involves the rag worm image. The structures that are coloured in a glowing pink are not eyes, they're sensory palps. They function as organs of smell, not sight. They eyes are on the upper surface of the animal and the image is of the underside. 

The head of a polychaete. The eyes are the four black spots at the left-hand end. The pharynx can be seen on the inside of the transparent body (photo Wim van Egmond).

Friday, February 24, 2012

Catlin Seaview Survey

The Catlin Seaview Survey will attempt to document the Great Barrier Reef in  a similar way to Google's Street View project. The images of the reef will be available through Google Earth and Google maps and cover a depth range of 0 - 100 meters.

The Catlin Seaview Survey is first and foremost an important scientific expedition. It aims to carry out the first comprehensive study to document the composition and health of coral reefs on the Great Barrier Reef and Coral Sea across an unprecedented depth range (0-100m) – addressing a series of important questions regarding the changes associated with the rapidly warming and acidifying oceans.However this is not just another scientific survey.Usually scientific surveys don’t have the ability to really capture the public’s imagination and engage people in the science. Expeditions and their findings tend only to be fascinating to other scientists. This  project is very different. The images from the expedition, when stitched together, will allow scientists and the public at large to explore the reef remotely through any device connected to the Internet. It will allow them to choose a location, dip underwater, look around and go off on a virtual dive. It has the potential of engaging people with the life and science of our oceans in a way that’s not been possible until now. It is a very exciting time.

Rare whale footage

I must again state that whales and dolphins are not that interesting. But I there is some footage of a very rarely seen whale swimming off south-west Victoria (which is not Bass Straight as the caption to the video says) that other people might find interesting. It's Shepard's beaked whale, known only from a few sightings and 42 stranded individuals. The video is believed to be the only moving footage ever captured.

Saturday, February 11, 2012

More adaptationism

Yesterday I wrote about Chris Mooney who concocted an adaptationist story about how the brain differences underlying political preferences have evolved by natural selection. A new article provides another example of adaptationist arguments as it tries to explain how the zebra got its stripes. Over at Sandwalk their is an excellent explanation of why we shouldn't get too excited that we've found the reason for zebra stripes just yet.

Friday, February 10, 2012

Mooncalf Mooney

Chris Mooney touts himself as pro-science and pro-evolution. But, in an essay in the Huffington Post to promote his new book, he does evolution a disservice. One of the claims commonly leveled at evolutionary biologists by creationists is that they tell 'just-so stories'. That is, they pick a trait and create an often plausible argument about the selection environments that would favour the evolution of the trait. But, critically they do not demonstrate that such selection environments exist, that the trait in question is inherited, or that it does increase fitness.

The title of Mooney's piece is "Want to understand Republicans? First understand evolution", which is ironic because, in writing it, he shows that he does not have a good understanding of evolution. He argues that political preferences may stem from natural selection on the brain that leads to differential responses to aversive stimuli (such as negative, threatening or disgusting images). The speed and strength of these responses is correlated with political ideology. Mooney does provide some evidence that may (emphasis on the 'may') show that the brain differences leading to political preferences are genetically linked. 

Showing that traits can be inherited is necessary, but insufficient to demonstrate that the trait has or is undergoing adaptive evolutionary change. Without evidence that the trait results in differential reproductive success there is no good reason to conclude that evolution by natural selection is responsible for producing the trait. But, Mooney foolishly does. Jerry Coyne, of 'Why Evolution is True' fame, goes into more detail about Mooney's foolishness here.

Adaptationist is the technical term for someone who accepts plausible arguments alone as evidence for adaptation. Gould and Lewontin published an excellent critique of this way of thinking, which is freely available for download from here. By coincidence, there is also a couple of posts about adaptationism on Sandwalk, here and here.

Tuesday, February 7, 2012

Carnival of Evolution

The Carnival of Evolution collects the best blog posts on evolution from the last month. It's always a good read. It's hosted by a different blogger each month. This month it's on the blog 'The Atavism'.

If you're wondering what an atavism is, it's an ancestral trait that appears in an individual of a species that normally does not display that trait. For instance, whales evolved from four legged terrestrial ancestors. Their forelegs have become highly modified to flippers, while their hindlimbs have almost completely disappeared (only present as a remnant of the hindlimb girdle). But, from time to time examples of whales and dolphins with rudimentary hindlimbs are found. Mostly is it only the main bones of the leg (the femur, tibia and fibula) that are present, but examples with a complete set of foot bones have been documented too.

Atavistic hindlimbs on a dolphin captured by Japanese 'researchers' off the coast of the infamous Taiji, the town featured in the movie 'The Cove'.

Monday, February 6, 2012

A talk

If you happen to be in Melbourne on Thursday the 9th of February, you might be interested in going to this talk on little penguins.

"Foraging Ecology of Little Penguins" presented by Nicole Kowalczyk, PhD student, Monash University.

Where: The Green Building, Meeting Rooms 1 & 2, 60 Leicester St Carlton, Melway Ref: 2B 11D

When: Thursday 9th February 2012

Time: 8.00pm – 9.30pm

The Little Penguin Eudyptula minor has been referred to as the 'Blue' or 'Fairy' Penguin. It occupies the southern parts of Australiaand New Zealand and is not considered threatened however population declines have been recorded.

The St Kilda Penguin Research Group, managed by Earthcare has been monitoring the St Kilda penguin colony since 1986. Earthcare, a local environment group works in partnership with local government, state government bodies and researchers to improve the conditions of Little Penguin habitat. Earthcare has collected a large body of data on the local colony in terms of population size, individual life history traits and breeding numbers. These data provide valuable information on population dynamics and breeding success and identifies annual changes in population parameters.

In 2010 Nicole Kowalczyk undertook  her PhD at Monash University in partnership with Earthcare. Last year she was a recipient of Birds Australia's Stuart Leslie Bird Research Award.  The primary purpose of Nicole's study is to understand the nutritional ecology of this colony and to assess how this translates into breeding performance. By correlating the acquisition of dietary resources with reproductive success  she hopes to assess how Little Penguins respond to seasonal and annual changes in their diet. This knowledge will ascertain whether the dietary needs of Little Penguins are being met and will aid in predicting how penguins will respond to further anthropogenic alterations of Port Philip Bay.

Free parking directly outside, and the venue is a 3-minute walk to public transport. Stay afterwards to socialise and enjoy light refreshments.

Organised and hosted by the BirdLife - Victoria Committee

Plankton Deep Dancer

Have you ever wondered what your parents would've named you if they were merfolk? Me neither.

But, if you are now curious, check out the Mermaid name generator.You too, could be called Plankton Deep Dancer.

A little nit-to-pick with the name generator. The first word in a binomial species name should always be capitalised!

Sunday, February 5, 2012

An ocean of plastic

There are five major oceans in the world. There's the Arctic Ocean, the Atlantic Ocean, the Pacific Ocean, the Indian Ocean and the Southern Ocean. In the Pacific, the Atlantic and Indian oceans there are huge circular currents called gyres. The Indian Ocean has a single gyre, while the Atlantic and the Pacific have two, one in the northern hemisphere and one in the southern hemisphere.

The five great oceanic gyres showing the direction of rotation
The northern hemisphere gyres rotate in a clockwise direction, while the southern hemisphere gyres rotate in an anti-clockwise direction. The direction of rotation has to do with the Coriolis effect, which is what people joke about when the say that water goes down plug-holes in different directions in Europe compared to Australia. The Coriolis effect doesn't matter too much for water going down plug-holes (other forces are far more important), but operating over long time periods and over large distances it produces gyres.

Because the gyres rotate they are good at accumulating floating items in their centres. Waste material is drawn into the gyres from the countries that surround the gyre. When the waste reaches concentrations that are significantly higher than the rest of the World's oceans that area of ocean is termed a garbage patch. So far surveys have found garbage patches in the North Pacific, North Atlantic and Indian Ocean gyres. Garbage patches also form in other places, but the oceanic gyres form the biggest patches.

Of all the garbage patches the North Pacific gyre is the largest by a considerable margin. Mainland Australia has an area of 7.69 million square kilometres and estimates of the size of the North Pacific Garbage Patch are as high as 15 million square kilometres. So, basically there's a patch of garbage that could cover an area almost twice the size of Australia floating in the North Pacific. It should be noted, however, that other estimates are considerably smaller. Estimates vary largely because different studies use different densities of debris to define what a garbage patch is.

Plastic particles hanging underwater in the North Pacific garbage patch (photo Scripps Oceanography).
The garbage patches collect a huge array of debris and chemical waste. A lot of it, about 80%, comes from land-based sources. Natural disasters, such as a tsunami or a hurricane can lead to large amounts of waste entering the sea. However, the most common route is through storm water and waste water inputs. The other 20% of waste is lost or deliberately dumped from ships at sea. Although it has been illegal to dump waste at sea for the last 20 or so years, the law is almost impossible to enforce.

By far the most common thing found in the garbage patches is plastic. Mostly it's small particles of plastic, but sometimes very large items like fishing nets that are kilometers long can be found. The fact that it is mostly plastic is pretty amazing seeing as plastic has only become common since the Second World War. But the plastic is able to accumulate because, unlike many other type of rubbish that finds its way into the sea, there are very few organisms that can break it down.

A ghost net floating in the North Pacific garbage patch (photo Scripps Oceanography).
Plastic has a number of negative effects on marine animals. Probably the effect that most people would be familiar with is that large items of plastic, like ropes, fishing line and fishing nets can entangle marine animals. This can cause them to drown, if they breath air, it can inhibit their movements making them more vulnerable to predators and it can cause them injuries as they try to struggle free.

A beached whale's tail entangled with ropes (photo Mike Baird).
Another effect is that marine animals can consume the plastic because it looks to them like a tasty piece of food. At its most minor the animal has simply wasted its time and effort catching the plastic. But, if an animal eats enough plastic it can clog their digestive tracts making it hard for them to eat and digest real food. And it is not just the larger animals like whales, turtles and sea birds that are at risk from ingesting plastic. We know that there are some very small, even microscopic animals that are eating plastics.

Plastic bag fragments found in the contents of a turtle's stomach (photo Victoria González Carman).
Plastics have also been reported to accumulate toxic chemicals on their surface in high concentrations. And if marine animals eat the plastics the chemicals can be released during digestion and become incorporated into their tissues. So even if an animal eats plastic rarely, it can acquire a toxic dose of some chemicals that enter its system via the plastic. The research on toxic plastic is controversial and not yet widely accepted.

So plastic waste is a huge problem for life in the ocean. In fact, one researcher looking at plastics in the ocean has argued in a recent book that the biggest effect on the marine environment this century won't be climate change, it'll be plastic waste.