Repost from Wired.com: Sea Creatures Hint at Recent Trans-Antarctic Seaway

The discovery of nearly identical sea creatures on either side of a now solid Antarctic ice sheet — 1,500 miles wide and over a mile thick — points to an open ocean passage there as recently as 125,000 years ago.

A schematic of a seaway created by the partial collapse of the West Antarctic Ice Sheet (on left).

The new evidence adds to geologic clues indicating the West Antarctic Ice Sheet has collapsed at least once in the last million years, and could do so again in a warmer climate. The complete collapse of the West Antarctic Ice Sheet would raise global sea level by 11 to 16 feet.

“The West Antarctic Ice Sheet can be considered the Achilles heel of Antarctica,” biologist David Barnes of the West Antarctic Survey, lead author of the study, said in a press release. “Our research provides compelling evidence that a seaway stretching across West Antarctica could have opened up only if the ice sheet has collapsed in the past.”

As part of the Census of Antarctic Marine Life, scientists were looking at the distribution of different species of bryozoans, small filter-feeders that are attached to the sea floor as adults (top image). They found that the populations of bryozoans were remarkably similar in two different seas separated by the ice sheet, the Weddell and the Ross.

“Because the larvae of these animals sink and this stage of their life is short — and the adult form anchors itself to the sea bed — it’s very unlikely that they would have dispersed the long distances carried by ocean currents,” Barnes said. “Our conclusion is that the colonization of both these regions is a signal that both seas were connected by a trans-Antarctic sea way in the recent past.”

“This biological evidence is one of the novel ways that we can look for clues that help us reconstruct Antarctica’s ice sheet history,” Barnes said. The study appears in Global Biological Change.

The West Antarctic Ice Sheet is already considered to be highly vulnerable to climate change, but estimates of when it might collapse vary from a few hundred to a few thousand years.

Read More http://www.wired.com/wiredscience/2010/08/antarctic-passage/#ixzz0yH1cDspW

Shrimp Go Into the Light

A recent study in aquatic toxicology studied the effects of several well prescribed anti-depressants on the behavior of shrimp. One in particular, fluoxetine, better known as Prozac significantly altered the shrimp’s behavior, causing them to move towards rather than away from light right into the awaiting maws of predatory shrimp-eaters. In scientist speak, this movement towards or away from light stimulus is called “phototaxis” (on a complete aside, another more bizarre photo-response is the photic sneeze effect where bright light causes someone to automatically sneeze. I like the mental picture of a mass of little sneezing shrimp…).

These kinds of studies are gaining more import because of the types of chemicals ending up in aquatic systems. Much of what we put into our bodies is never completely absorbed and ends up in the sewer system which consequently often ends up in other water-based ecological systems (sewage is treated for things like excess nutrients but we couldn’t possibly screen for all the possible chemicals sewage may contain). So materials like caffeine, medications we take, etc. are now outside of our superficial human realm and in the larger natural environment, with detrimental if not even bizarre effects on wildlife including sex changes in fish.

To find out more, read the sciencedaily feature here.

From Science Daily: How the Sea Snake Got Its Stripes

I was delighted just by the title of this Science Daily story alone – due to its folk tale inspired headline – but was further intrigued about the suggestion that coloration of some sea snakes may cause them to be susceptible to the colonization of algae on their skin which may slow them down their swimming speed among other possible consequences. The excerpt and photo below are from the original Science Daily article which can be accessed here:

ScienceDaily (Apr. 14, 2010) — We all know that looks matter, and for snakes, a colour which works well on land has dramatically different results under water, according to a recent study by biologists from the University of Sydney.

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Professor Rick Shine and Dr Adele Pile from the School of Biological Sciences have discovered a sea snake’s colouration can influence its susceptibility to algal fouling which can reduce swimming speed by up to 20 percent.

Their study, reported this month in Proceedings of the Royal Society B, sheds new light on how the transition from terrestrial to aquatic life has shaped the evolution of sea snakes.

Professor Shine said sea snakes evolved from venomous land snakes — such as the highly toxic tiger snake — who reinvaded the oceans around five million years ago.

“The fact that sea snakes have made the transition from terrestrial to aquatic life, makes them the perfect model to study evolution because we can compare traits between land snakes and sea snakes and hence identify selective forces unique to those habitats,” he said.

“The shift from land to water brought with it a new set of challenges, and sea snakes evolved unique physical traits which enabled them to survive in the aquatic environment — a paddle-shaped tail for swimming, valves to close their nostrils and large lungs to provide oxygen while under water.

“Another consistent attribute of sea snakes involves coloration: most are banded rather than unicoloured, blotched or striped. Fouling by algae has also been reported in several groups of sea snakes, and we wondered if maybe a snake’s colour could influence its susceptibility to this.”

To test this hypothesis, the scientists turned to a population of sea snakes in the tropical Pacific, in which members of the same species ranged from jet black to brightly black-and-white banded, and many patterns in between. Over a four-year period, the researchers examined free ranging individuals and found that black snakes supported significantly more algal cover than black-and-white snakes.

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“There is clearly a balance of costs and benefits of algal accumulation, which is why we see a variety of colours in the population. For example, a covering of seaweed may slow down the snake and reduce its ability to obtain oxygen from the water directly through its skin, because the algae form a barrier. But on the flip side, the algae might increase the snake’s oxygen availability, because of algal photosynthesis, and hence benefit the snake.”

Octopi- Unlikely Geniuses

I’ve long been interested in octopi (the plural of octopus, as octopuses doesn’t quite work). I’ve recalled prior stories on their mimicing ability and tales originating from aquariums about their resident octopi crawling out of their tanks, into others nearby, and snacking on the exhibit fish. Or perhaps this story about an octopus who escaped a tank in an Australia aquarium and bided his time in a drain waiting for an opportunity to escape. They’re incredibly smart animals which has suprised researchers as they expect these traits in longer-lived organisms. Most species of octopus will lives less than five years. Nevertheless, according to a fascinating article in Discover Magazine:

“Anatomy confirms what behavior reveals: Octopuses and cuttlefish have larger brains, relative to body weight, than most fish and reptiles, larger on average than any animals save birds and mammals. Although an octopus brain differs from a typical vertebrate’s brain—it wraps around the esophagus instead of resting in a cranium—it also shares key features such as folded lobes, a hallmark of complexity, and distinct visual and tactile memory centers. It even generates similar electrical patterns.”

 The latest in a series of reports about octopi doing a little marine yoga and arranging their bodies in shapes reminiscent of other ocean life is a video of an octopus in the Caribbean mimicing a flounder (in some senses, he almost looks like a skate to me):

This is the first Atlantic species discovered to do this, but scientists have known about the Indonesian mimic octopus for quite some time:

Not only, are these creatures masters of mimicry, but it appears they also join the list or organisms observed using tools. Another indonesian species, the veined octopus has been spotted carrying around coconut shells that they can use to form a shelter when predators threaten. Read more here.