A wrinkly hypothesis

The aquatic ape hypothesis was first proposed 70 years ago by German pathologist Max Westenhöfer. The hypothesis has more recently championed by Elaine Morgan, most notably in her book The Aquatic Ape. But the hypothesis has not drawn a lot of attention in the literature and has been dismantled in various places (here's one that's pretty good). Essentially the hypothesis interprets certain features, such as human hairlessness, as adaptations to an aquatic environment.

In 2011 Changizi et al. published a paper arguing that water-wrinkled fingers are an adaptation to life in aquatic environments. A new paper, just published, purports to test this hypothesis. Kareklas et al. had test subjects soak their hands in 40°C water for 30 minutes. Then they got the subjects to move marbles from a source container that was either filled with water or dry. The performance of the wrinkly handed participants was compared to a control group that performed the same task without soaking their hands.

Their results showed that the wrinkly finger group completed the marble moving task 12% faster when the source container was filled with water. There was no difference between the two groups when it was dry. They argue that their study shows a clear advantage to having wrinkly fingers when manipulating submerged items. But, I find the experiment completely underwhelming as support for wrinkly fingers as adaptations.

Most obviously, participants had to soak their hands in 40°C water for 30 minutes in order to obtain the small advantage. If wrinkled fingers are important for manipulating submerged objects, it seems to take an inordinately long time for fingers to wrinkle. Moreover, prior research has shown that lower temperatures, which are more likely to be encountered by our ancestors, result in slower and less exaggerated finger wrinkling (reviewed in Wilder-Smith 2004).

Marbles are also particularly small and slippery when compared with almost all conceivable objects that a paleolithic primate would be interested in picking up. It would be far more compelling if they had shown that the performance advantage remained when other objects were manipulated underwater. Given the very small advantage for marbles, I strongly suspect that the advantage would disappear for a vast array of other items.

The proponents of the aquatic ape hypothesis will probably incorporate the new study into their lists of evidence for a close association with with water in our ancestors. But, like most of their evidence, it is little better than plausible speculation dressed up as a compelling theory that deserves attention. It's a great way to get your ideas attention in the popular press, it's a horrible way to do science. The inoculation for such adaptationist nonsense is, as always, Gould and Lewontin 1979. 

Kareklas, K., Nettle, D., & Smulders, T. (2013). Water-induced finger wrinkles improve handling of wet objects Biology Letters, 9 (2), 20120999-20120999 DOI: 10.1098/rsbl.2012.0999 

Changizi, M., Weber, R., Kotecha, R., & Palazzo, J. (2011). Are Wet-Induced Wrinkled Fingers Primate Rain Treads? Brain, Behavior and Evolution, 77 (4), 286-290 DOI: 10.1159/000328223 

Wilder-Smith, E. (2004). Water immersion wrinkling Clinical Autonomic Research, 14 (2), 125-131 DOI: 10.1007/s10286-004-0172-4

Waterfall climbing fish

Diadromous fish are those that live part of their lives at sea and part of their lives if freshwater. Some of these fish reproduce in the upper parts of rivers above barriers like waterfalls, which they must scale in order to make it to the breeding sites. A newly published paper looks at how the Nopili goby, Sicyopterus stimpsoni, manages to climb waterfalls. The researchers found that the way the goby feeds and the way it climbs are very similar.

The Nopili goby, Sicyopterus stimpsoni (photo Takashi Maie)

During feeding the Nopili goby extends its upper jaw out much further and its lower jaw much less than other gobies. In climbing the basic motion is the same except the upper jaw maintains closer contact with the rock. Climbing is also assisted by pelvic fins fused into a sucker, a feature of all gobies. Because no other goby feeds in the same way, it's unclear whether the feeding or climbing movements evolved first.

The climbing galaxias, Galaxias brevipinnis (photo Robert McCormack)

There are many other fish that have a diadromous life-history, eels and salmon being the classic examples. There are fewer fish that climb waterfalls. However, in southern Australia and New Zealand there is a fish close to my heart that has a very similar life-history to the Nopili goby, but it climbs waterfalls in a different way. The climbing galaxias, Galaxias brevipinnis, climbs using its broad pectoral and pelvic fins and wiggling upwards.

Cullen J. A., Maie T., Schoenfuss H. L., & Blob R. W. (2013). Evolutionary Novelty versus Exaptation: Oral Kinematics in Feeding versus Climbing in the Waterfall-Climbing Hawaiian Goby Sicyopterus stimpsoni PLOS One, 8 (1) DOI: 10.1371/journal.pone.0053274

Flames under the sea

A survey to help locate sites for new marine protected areas has turned up perhaps the largest colony of flame shells, Limaria hians, anywhere in the world. The bed located at the bottom of Loch Alsh in western Scotland, contains at least 100 million individuals and covers 75 hectares.

The flame shell, Limaria hians (photo Wikipedia)

The flame shell is a bivalve mollusk that feeds by extending many orange tentacles out of its shell snaring food from the water column much like corals do. They grow to a maximum of about 4cm long, but most are around 2.5cm. Preserving flame shell beds is a conservation priority because they form nest-like structures that stabilise coarse sandy substrate giving other plants and animals a place to grow.

Giant squid in full HD!!

A week ago the Discovery Channel announced that it had footage of a giant squid that it would be releasing in January 2013! It could be the first video footage ever captured of a live giant squid in its natural habitat. Previous footage of a live giant squid has been taken at the surface after the squid was caught. In 2005 and Japanese team lead by Tsunemi Kubodera and Kyoichi Mori took the first still images of a giant squid attacking a baited line. The next year a team lead bu Kubodera caught a small female squid using a similar method and filmed it as it was brought into their boat.

A giant squid attacking a baited line (photo Kubodera & Mori)

I'm guessing that Kubodera is involved again, but other researchers may have used similar methods to get this latest footage. Basically, look for where sperm whales are diving, drop a baited line down a few hundred meters with a camera on it and wait. Easy!...

Shifting baselines in coral cover

A great problem for conserving marine ecosystems is that we rarely have a good data on what things were like before human impacts started. In my last post, I wrote about a study that showed that coral cover had declined on the Great Barrier Reef by 50.7% since 1985. At the start of the study coral cover was at 28%, but pristine coral reefs can have over 70% coral cover. This suggests that impacts on the Great Barrier Reef predate the time monitoring started by many years.

A coral outcrop on the Great Barrier Reef (photo Wikipedia)

John Pandolfi at the University of Queensland has been trying to establish the past state of the Great Barrier Reef in numerous ways. One way is to take sediment cores from coral reef and compare the historical diversity and abundance of corals on the reef to the modern community composition. A new study lead by Pandolfi has reconstructed the past coral communities on reefs around Pelorus Island in the Palm Island group. They took cores containing coral remains dating back as far as the mid-third century.

They found that there was a pronounced transition in the coral species on the islands reefs between 1920 and 1955. The transition strongly correlated with a 5 to 10 fold increase in the amount of sediment found in the cores beginning in 1870, but showing several large peaks between the 1920s and 1970s. White settlement and land clearing of the area began in about 1870, the same time that high sediment loads were found in the cores. Prior to that, there was remarkable stability in the coral communities and the amount of sediment reaching the reef.

The new study highlights that reefs in 1985 that were thought to be relatively pristine probably had not been for 50 or 60 years. Therefore attempts to conserve reefs as they were in 1985 is inadequate because these reefs are likely to be already severely impacted by human activities. If we a serious about returning coral reefs to a pristine state, we should be restoring them to what they were like prior to white settlement, not what they were like now after a century of mistreatment.

Roff, G., Clark, T., Reymond, C., Zhao, J., Feng, Y., McCook, L., Done, T., & Pandolfi, J. (2012). Palaeoecological evidence of a historical collapse of corals at Pelorus Island, inshore Great Barrier Reef, following European settlement Proceedings of the Royal Society B: Biological Sciences, 280 (1750), 20122100-20122100 DOI: 10.1098/rspb.2012.2100

Conservation priorities on the Great Barrier Reef

A recently published paper on the decline of coral cover on the Great Barrier Reef serves to illustrate an important point; even without climate change we are doing a great deal of damage to some ecosystems. The study by De'ath et al. and published in the Proceedings of the National Academy of Science, finds that coral cover has declined by 50.7% since 1985. They partitioned the losses into 48% tropical cyclones, 42% predation by crown of thorns starfish and 10% to coral bleaching.

The crown of thorns starfish, Acanthaster planci (image Wikipedia)

The declines were not uniform across the reef. Most of the declines were in the southern part of the reef and near to shore, where more people live. Partly this may be due to more frequent storms in the southern part of the reef, but storm frequency has declined in the last 100 years or so. Mostly it's probably because outbreaks of crown of thorns starfish are linked to human activities, such as agriculture and fishing. And these same human activities leave coral less resilient to other impacts and make it more difficult for them to recover from disturbances.

Pollution, sedimentation and overfishing can all change the dynamics of coral reef communities by impairing the ability of corals to recover from other disturbances. Human activities can also increase the mortality of adult coral and reduce the number larvae that survive to become coral. Shifts from coral-dominated communities to seaweed-dominated communities due to these impacts are well documented.

Overfishing, particularly of herbivorous fish, has been strongly linked to shifts in community composition. In direct competition corals lose out to seaweed, which overgrows coral and in some cases uses toxins to kill the coral. Herbivorous fish though, eat the seaweed tipping the balance in favour of the corals. So important are herbivorous fish to corals that some have formed mutualistic relationships with fish, which they signal for help when seaweeds encroach on their space. 

Overfishing has also been suggested to reduce predation on larvae of the crown of thorns starfish, allowing it to reach plague proportions when fish would normally control their numbers. A second hypothesis is that nutrient inputs from farms and cities provides the crown of thorns larvae with large amounts of food, increasing their survival. Neither hypothesis is well supported, but there is growing evidence that both mechanisms are playing a role in crown of thorns outbreaks. 

For corals, like seagrasses, access to light is critical for their survival. Coral derive as much as 90% of their energy from symbiotic algae growing in their tissues. Nutrient inputs and sedimentation reduce the light available to their algal symbionts, which reduces the energy available to them. This can decrease the resilience of corals to other stressors, such as natural disturbance events. The main sources of sedimentation on the Great Barrier Reef are from human activities, such as agricultural run-off and dredging.  

De'ath et al. conclude that there is an urgent need to control crown of thorns outbreaks, especially through improvements to water quality. In the absence of disturbances, the data showed that reefs were able to increase in cover by nearly 3% per year. This is likely to be higher when the full impact of human activities are taken into account. Moreover, their data only go back to 1985, but human impacts on the reef date back to about 100 years before that. The true decline of coral cover on the Great Barrier Reef is, therefore, likely to be far greater than that measured in their study.

De'ath et al. also highlight the impending effects of climate change and ocean acidification. Many people are focused on human emissions of carbon dioxide as the sole problem we need to fix to save the reef. But, it's clear that even without the threats of climate change and ocean acidification the Great Barrier Reef is in great deal of trouble. In order to conserve the reef we need to address the source of these issues now.

De'ath, G., Fabricius, K., Sweatman, H., & Puotinen, M. (2012). The 27-year decline of coral cover on the Great Barrier Reef and its causes Proceedings of the National Academy of Sciences, 109 (44), 17995-17999 DOI: 10.1073/pnas.1208909109

Everyone loves bacon

Researchers at the VENUS Observatory put a pig carcass in 300 meters of water and watched to see what came to eat it. Mostly amphipod crustaceans, it would seem.

Results vary only slightly when the carcass is not in a cage. The wounds that appear early in the video are caused by sharks, I'm pretty sure.

All the better to carry you with

Over at Why Evolution is True, Mathew Cobb makes fun of adaptationist "just-so stories" about a beetle that evolved handles so that it could be more conveniently carried by termites. It's definitely worth a read.

More on the iron fertilisation "experiment"

A little while ago I wrote a post on the actions of Russ George, a businessman who has been trying to sell ocean iron fertilisation as a viable method for reducing carbon dioxide in the atmosphere. His arguments about the success of such schemes are way out in front of the science required to support them. He released 100 tons of iron sulfate into the north-eastern Pacific in what he calls an experiment, but what nearly all other pundits have been calling an irresponsible and reckless action.

His supporters have rallied behind him though and have had a presence in nearly every comment thread of prominent science news sites that have covered the issue. So, I thought I would take some time to put my views on the potential dangers of large-scale fertilisation of the ocean with iron.

Phytoplankton is not only reliant on iron to survive. There are several other important nutrients that limit phytoplankton numbers in areas where iron is abundant, such as phosphorous. Large blooms of phytoplankton that are produced by the addition of iron could rapidly deplete other limiting nutrients. Once the bloom has consumed the added iron and collapsed the population may not recover back to what it was prior to the bloom because it is limited by more than iron. 

When the bloom dies and decomposes, it could reduce a molecule that is highly important to a great many marine organisms, oxygen. Areas of the ocean that become so low in oxygen that they are no longer able to support life and know as dead zones. The appearance and expansion of dead zones is often caused in areas where human inputs of important nutrients, such as phosphorus and nitrogen, increases the abundance of phytoplankton. The bacteria that consume the dead phytoplankton also consume the dissolved oxygen, depleting it to levels dangerously low for many other organisms.

The rain of dead phytoplankton could also have serious effects on the seafloor community beneath. Indeed, one of my very first posts on this blog was about how the energy balance in the deep sea was critical to maintaining a high diversity of species in an energy poor, seemingly homogenous environment. A huge input of nutrients from the detritus of a plankton bloom that reaches the seafloor is likely to upset the ecology of the communities found there.

While I think that these are all legitimate concerns, it is important to note that, to my knowledge, none of these effects have been observed in iron fertilisation experiments. Oxygen depletion is a known and well documented effect of phytoplankton blooms. But, iron fertlisation on the scale of Russ George's venture may not be large enough or persist for long enough to have this effect. And natural phytoplankton blooms on the scale of the one observed in the area that George dumped his iron are not unknown.

In fact, some researchers are claiming that the observed phytoplankton bloom was already underway before George released the iron sulfate. Many reports I have read say that that the iron fertilisation occurred in July at the time the plankton bloom was getting started. But, it seems the ship which released the iron sulfate didn't leave port until the 8th of August and probably couldn't have started fertilising until a week later. Natural blooms are known to occur regularly in the area, particularly during summer when offshore currents carry iron-rich water hundreds of kilometers out to sea. Unfortunately, the design of the experiment is so poor that it's hard to tell whether the iron sparked the bloom or how much it contributed to it.

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Rare whale washes up in New Zealand

Ed Yong is a great science writer with a blog on Discover Magazine's website. He has an interesting post on a whale so rare that has never been seen alive. In 2010 two individuals washed up on a beach in the north of New Zealand. They were misidentified as the related Gray's beaked whale, Mesoplodon grayi, until genetic analysis of samples taken from the dead whales showed they were in fact the elusive spade-toothed whale, M. traversii. The subject of Ed's post is a recently published paper the reports on the genetic analysis and provides the first morphological description of a complete animal.

Update
The Science Now site has a story on these whales too. It makes the claim that the beached whales were found alive. I don't know which version is correct.