Disco clam light, new research


This video from California in the USA is called Disco Clams Light Up the Ocean Floor.

From Wildlife Extra:

The secret of the disco clam’s light show is revealed

The Ctenoides ales file clam, also known as the disco clam, is one of the few creatures to use silica micro-structures to reflect light, according to new research published in the Journal of the Royal Society Interface.

The clam does it so well that for years divers and scientists alike believed that it was generating its unique electric display with light-producing chemical reactions known as bioluminescence.

Lindsey Dougherty, a PhD student at the University of California, Berkeley, first shattered that idea last year with a series of presentations showing that the lips were lined with reflective silica spheres.

For the new study, Dougherty and her colleagues used an electron microscope to look at the spectral signature of the structure of the clam’s lip tissue.

On one side were those microscopic balls of silica — the primary element in glass and quartz. The other side was dark, and only reflected light on the red-end of the visible light spectrum.

Because red light doesn’t transmit well underwater, the dark side of the clams’ lips are effectively non-reflective.

Conversely, the silica-side reflects 85 to 90 per cent of all white light when underwater.

“They’re almost ideal reflectors in blue-green water environments,” said Dougherty.

The team confirmed this by using computer models to see how the spheres’ structures reflected light at four different wavelengths.

Using a high-speed camera, they were able to see exactly how the clams make the flash: by rapidly rolling and unrolling their lips, exposing the dark and reflective sides at a rate of about two times per second.

Disco clams can be found all the way from Australia to Indonesia in water from 10 to 160ft deep.

Even in shallow waters, the clams tend to squirrel themselves away into relatively dark nooks, which explains why it seemed so natural to think that their display was bioluminescent.

From an evolutionary perspective, lightning lips are a pretty costly adaptation. They need special muscles to control the furling motion, and silica is a rare element in the ocean.

Dougherty said there are three possibilities: The lips are to lure in mates, attract prey, or ward off predators.

In the future, she’s going to be researching the clams’ eyes (they have up to 40). Knowing how the clams see could unlock the secret behind their most prominent light-show feature.

See also here.

New sponge species discovery in the Pacific


This video from California in the USA says about itself:

Four new species of carnivorous sponges: Adapting to life in the deep sea

14 April 2014

This video describes four new species of carnivorous sponges from the Northeast Pacific Ocean that were discovered by MBARI scientists. Carnivorous feeding in sponges is an adaption to the food poor deep-sea environment, where filter feeding — the typical way sponges feed — is energetically expensive. Instead, these sponges trap small crustaceans with microscopic hooks. Once trapped, sponge cells mobilize, engulf the prey, and rapidly digest it. In addition to consuming small crustacean prey, one of these species appears to be consuming methane-oxidizing chemosynthetic bacteria.

For more information visit here.

From Wildlife Extra:

Four new species of killer sponges discovered

April 2014: Four new species of carnivorous (killer) sponges living on the deep seafloor, from the Pacific Northwest to Baja California have been discovered by scientists from the Monterey Bay Aquarium Research Institute.

It was only discovered that some sponges are carnivorous about 20 years ago. Unlike other sponges most carnivorous sponges do not have specialised cells called choancytes, whose whip-like tails move continuously to create a flow of water which brings food to the sponge. Therefore these sponges, explains lead marine biologist Lonny Lundsten “trap larger, more nutrient-dense organisms, like crustaceans, using beautiful and intricate microscopic hook.”

These animals look more like bare twigs or small shrubs covered with tiny hairs. But the hairs consist of tightly packed bundles of microscopic hooks that trap small animals such as shrimp-like amphipods. Once an animal becomes trapped, it takes only a few hours for sponge cells to begin engulfing and digesting it. After several days, all that is left is an empty shell.The four new sponges are named as Asbestopluma monticola, (which was collected from the top of the extinct underwater volcano Davidson Seamount off the coast of central California), Asbestopluma rickets (named after the marine biologist Ed Ricketts), Cladorhiza caillieti, (found on recent lava flows along the Juan de Fuca Ridge, a volcanic ridge offshore of Vancouver Island), and Cladorhiza evae, which was found far to the south, in a newly discovered hydrothermal vent field along the Alarcon Rise, off the tip of Baja California.

Harmless dye reveals how incredibly efficient sea sponges are at pumping and straining water: here.

Prehistoric Pacific marine mammals discoveries


This video is called Whales evolution.

Not only news about big land mammals during the Ice Age … also about big marine mammals before the Ice Age.

From the University of Otago in New Zealand:

Strange marine mammals of ancient North Pacific revealed

February 5, 2014

Summary:

The pre-Ice Age marine mammal community of the North Pacific formed a strangely eclectic scene, new research reveals. Studying hundreds of fossil bones and teeth excavated from the San Francisco Bay Area‘s Purisima Formation, scientists have put together a record of 21 marine mammal species including dwarf baleen whales, odd double-tusked walruses, porpoises with severe underbites and a dolphin closely related to the now-extinct Chinese river dolphin.

The pre-Ice Age marine mammal community of the North Pacific formed a strangely eclectic scene, research by a Geology PhD student at New Zealand’s University of Otago reveals.

Studying hundreds of fossil bones and teeth he excavated from the San Francisco Bay Area’s Purisima Formation, Robert Boessenecker has put together a record of 21 marine mammal species including dwarf baleen whales, odd double-tusked walruses, porpoises with severe underbites and a dolphin closely related to the now-extinct Chinese river dolphin.

Among his finds, which were fossilized 5 to 2.5 million years ago, is a new species of fossil whale, dubbed Balaenoptera bertae, a close relative of minke, fin, and blue whales.

Mr Boessenecker named the whale in honour of San Diego State University‘s Professor Annalisa Berta, who has made numerous contributions to the study of fossil marine mammals and mentored many students.

Although an extinct species, it belongs within the same genus as minke and fin whales, indicating that the Balaenoptera lineage has lasted for 3-4 million years. Balaenoptera bertae would have been approximately 5-6 meters in length, slightly smaller than modern minke whales, Mr Boessenecker says.

His findings appear in the most recent edition of the international journal Geodiversitas.

The publication represents eight years of research by Mr Boessenecker, who was 18 in 2004 when he was tipped off by a local surfer about bones near Half Moon Bay. When he discovered the fossil site, he was astonished by the numerous bone-beds and hundreds of bones sticking out of the cliffs.

He excavated the incomplete skull of Balaenoptera bertae during early field research there in 2005 and it was encased in a hard concretion that took five years to remove.

“The mix of marine mammals I ended up uncovering was almost completely different to that found in the North Pacific today, and to anywhere else at that time,” he says.

Primitive porpoises and baleen whales were living side-by-side with comparatively modern marine mammals such as the Northern fur seal and right whales. And species far geographically and climatically removed from their modern relatives also featured, such as beluga-like whales and tusked walruses, which today live in the Arctic, he says.

“At the same time as this eclectic mix of ancient and modern-type marine mammals was living together, the marine mammal fauna in the North Atlantic and Southern Ocean were already in the forms we find today.”

Mr Boessenecker says this strange fauna existed up until as recently as one or two million years ago. Its weirdness was likely maintained by warm equatorial waters and barriers to migration by other marine mammals posed by the newly formed Isthmus of Panama, and the still-closed Bering Strait.

“Once the Bering Strait opened and the equatorial Pacific cooled during the Ice Age, modernised marine mammals were able to migrate from other ocean basins into the North Pacific, leading to the mix we see today,” he says.

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Pacific humpback whales, new discoveries


This video is called Humpback Whales – BBC documentary excerpt.

From LiveScience:

Distinct Humpback Whale Populations Found in North Pacific

By Laura Poppick, Staff Writer

December 04, 2013 03:02pm ET

Five distinct humpback whale populations have been identified across the North Pacific Ocean in the most comprehensive genetic study of the mammals in this region yet, a new study reports.

The ranges of the newly identified populations include: Hawaii; Mexico; Central America; Okinawa and the Philippines; and an additional West Pacific population whose range has yet to be determined more specifically.

Humpback whales are found in all oceans of the world, but the North Pacific humpbacks are genetically isolated enough to be considered a subspecies of other humpbacks, of which the new populations are further subclassifications, study co-author Scott Baker, a professor of fisheries and wildlife at Oregon State University, said in a statement.

“Even within these five populations, there are nuances,” Baker said. “The Mexico population, for example, has ‘discrete’ sub-populations off the mainland and near the Revillagigedo Islands, but because their genetic differentiation is not that strong, these are not considered ‘distinct’ populations.”

To distinguish the separate populations, the team studied DNA within 2,200 tissue samples of whales from 10 feeding regions and eight winter breeding regions during a three-year study called SPLASH, which stands for Structure of Populations, Levels of Abundance and Status of Humpbacks.

The team studied distinct breeding and feeding grounds because these are the types of “barriers” that isolate marine animal populations and make them become genetically distinct, whereas terrestrial animals more commonly become isolated and genetically distinct by geographic barriers, Baker said. Researchers think that migration routes, feeding and breeding grounds of individuals are passed from mother to calf and through subsequent generations, with the separations between populations ultimately becoming evident in their DNA as a distinct marker of the population.

Using photo identification records to estimate humpback whale populations, the researchers suggest roughly 22,000 humpbacks currently swim throughout the North Pacific, which is close to the population size of humpbacks before whaling decimated their populations during the 19th and 20th centuries. Commercial whaling has been banned by the International Whaling Commission since 1966, when hunting had dwindled the species down to roughly 5,000 individuals worldwide.

Though the U.S. Endangered Species Act still lists humpbacks as endangered, the International Union for the Conservation of Nature currently only recognizes two populations as endangered — one in the Sea of Arabia and one in Oceania. The team believes that one or more of the newly identified populations may qualify as endangered as well.

“Each of the five distinct populations has its own history of exploitation and recovery that would need to be part of an assessment of its status,” Baker said.

The study findings are detailed this week in the journal Marine Ecology – Progress Series.

Killer whales, new research


This video is called BBC Natural World: The Woman Who Swims With Killer Whales.

From Wildlife Extra:

Killer whales found to eavesdrop on prey

December 2013: UK Scientists have found evidence that marine-mammal-eating killer whales rely on acoustic clues to locate their prey.

While biologists had evidence that the whales do not echolocate while hunting, due to the excellent hearing of the seals, porpoises and other animals the whales hunt, they were still unsure exactly how the animals do find their prey in the murky northern waters off the west coast of North America.

However, a two-year study by Volker Deecke, a researcher at the Centre for Wildlife Conservation at the University of Cumbria, UK has revealed that killer whales can successfully locate prey even in near-complete darkness. Deecke notes that this new evidence of night-time hunting rules out visual cues as the only means of prey detection.

“We now suspect that mammal-eating killer whales are primarily eavesdropping on sounds generated by their prey to find food,” he said.

Deecke and his colleagues traveled to Alaska to conduct the study, analysing huge quantities of data gathered from acoustic recording tags placed on 13 killer whales. The tags, which are about the size of a cell phone, were attached to the whales with four suction cups and could stay on for up to 16 hours.

The tags’ accelerometers, compass, depth sensor, and hydrophone recorded data on the animals’ movements and any sounds it heard or made. Deecke and his colleagues were able to identify predation events by the characteristic sound of a whale dispatching its prey with a hit from its tail fluke.

Deecke said of one unfortunate seal’s demise: “As soon as we put one of the tags on, it started to record seal roars, which are part of the display that male harbor seals use to attract females. Over the next half hour the roars got louder and louder, then there are a sequence of three quite loud roars that suggest the seal is within a few hundred meters of the killer whale. Twenty-seven seconds later there are the sounds of a predation event, and then no more roars.”

Deecke notes that such a story is compelling but does not provide direct evidence that killer whales are tuning in to the sounds of their prey. Going forward, he hopes to use playback experiments to test killer whales’ responses to recorded seal roars and porpoise echolocation clicks.