Demystifying the Narwhal’s Tusk

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Photo Credit: National Geographic

Yet again drones have proved an invaluable instrument for new discoveries, especially when it comes to observing marine mammal behavior (see my past post: Whale Tales – Current Cetacean Communiqués).  The subject in question this time is the strange and elusive Narwhal.

Humans have valued Narwhal tusks for centuries, perceiving them as a cure for a number of medical ailments including epilepsy and poisoning, a practice which is still alive and well in Japan. Inuits still carry on the tradition of culling narwhal for subsistence and often used the tusks for carving. However, we have had little knowledge about the value of the tusk to the animal itself until recent years. More current research and observation suggests the tusks of narwhals function in multiple capacities.

The edited footage above conveniently highlights moments where individual narwhals stun passing cod with a solid tap of their tusk. It’s an interesting hunting method, but one that is rivaled by other examples in the marine world. Many species immobilize their prey; some, like sailfish, use similar techniques, while others may use contrasting tools. Electric Rays and eels shock their quarry, while pistol shrimp use high-speed cavitation bubbles to daze their targets. Archer fish knock their dinner out of overlying branches by spitting a stream of water at them.

The purpose of the narwhal’s tusk likely doesn’t stop at clubbing unwitting prey. The absence of an enamel coating on their tusk supports the idea that these animals might be using them in a sensory capacity, allowing the specialized tooth to come into contact with surrounding water masses to detect environmental changes such as salinity and temperature, as well as chemical cues in the water associated with food and mates. Pairing this awareness of their surroundings with highly directional echolocation also allows them to find sometime slim openings in Arctic ice coverage where they can surface and breath as needed.

However, these animals may still suffer catastrophic events living in the extremes they do. Pods of narwhals occasionally suffer entrapments when rapidly shifting weather conditions cause unexpected freezing over potential air holes leading to open water. Kristin Laidre, a researcher at University of Washington’s Polar Science Center, noticed the frequency and timing of those events may be changing with recent shifts in Arctic climate. This, paired with a variety of additional stressors to the whales’ habitat, is the focus of one her current research projects examining the behavioral ecology of narwhals in a changing Arctic. She and other researchers have tagged the animals on multiple occasions in Canada’s Baffin Bay to track their movement, the depth of their dives, and associated water temperatures. As it turns out the temperature data has proved useful to other scientists interested in climatology data. Laidre is soon hoping to once again utilize the oceanographic power of narwhals, this time in Greenland.

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Speck of Science 2/19/17 – Denuding Geckos

 

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Photo Credit: A. Anker

A week and half ago multiple science news outlets reported on the publication of a study that described a new species of Geckolepis geckos, a bizarre genus that goes by the more common moniker of “fish-scale” geckos. They appear to be relatively unique to the Comoros Islands and Madagascar, locations that harbor other fascinating endemic species (restricted to a certain region), a fact which can largely be attributed to island isolation.

These lizards are sheathed in a layer of vibrant scales that they jettison quickly in response to perceived predatory threats. Mark Scherz, the PhD candidate who lead-authors the study, experienced significant challenges trying to collect fully-covered specimens of what would later be identified as Geckolepis megalepis. The gecko loses skin with scales, and much resembles a naked baby mouse after the process. As the study notes, “The new species has the largest known body scales of any gecko (both relatively and absolutely), which come off with exceptional ease.”

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Photo credit: F Glaw

This quality of Genus Geckolepis to lose then regenerate scales is suggested to have applications in human medicine with regards to tissue recovery. In addition, geckos have been studied for other enviable qualities including their ability to adhere to vertical surfaces with ease.

 

 

Faltering Ice – The Crack in Larsen C

There is currently a great deal of collective breath-holding surrounding the fate of a portion of the Larsen C ice shelf. Reports since December have been narrating the changes in a widening crack along its face, as the rift has increased in length by 20 miles. Only a 12 mile stretch of intact ice keeps the shelf tenuously anchored. As USA Today notes, you can literally bet on when it will give way.

The Larsen ice shelf is a region of chaos along the Antarctic Peninsula which curves towards the toe of Chile. The region is named after whaling captain and explorer Carl Anton Larsen, who experienced an Antarctic winter stranding with his men, not unlike that of Ernest Shackleton. Much of the shelf has already been lost previously due to catastrophic collapse events. 1995 saw the crumbling of Larsen A. Seven years later, Larsen B disintegrated over the course of 2-3 months. Its epic demise was cataloged by watching satellites.

The sheering off of these massive stretches of ice are not without effect. Ice shelves are comparable to sea ice, and their liberation does not directly contribute to changes in sea level. However, they often fortify nearby glaciers, and once absent, glacial movement can speed up significantly. Glacial ice, in contrast, can contribute to changing sea levels. It is thought that global warming trends have contributed to many ice sheet de-stabilization events around Greenland and Antarctica. Because ice is a cooling influence on climate due to its reflective nature (called albedo), ice loss is part of a positive feedback loop. Warming trends reduce both ice cover and albedo which leads to further warming.

This NASA photo released December 1, 2016 shows what scientists on NASA's IceBridge mission photographed in a view of a massive
View of the Larsen C ice shelf fissure in Nov 2015 as documented by the NASA Icebridge Mission.

On perhaps a lighter note however, the calving of ice also has also led to unexpected discoveries. After the break up of Larsen B, scientists discovered an intricate chemotrophic ecosystem a half mile below the ocean’s surface.  Chemotrophic organisms create their own energy through chemical pathways rather than relying on photosynthesis. The system below Larsen B was populated by cold seep clams and mats of microbes, examples of tenacious organisms that have adapted to get by with little access to sunlight or the growth of the phytoplankton food source it supports. This along with findings like vast microbial communities found within subglacial lakes in Antarctica adds to our collective evidence that life finds ways to subsist in the most extreme of environments.

Speck of Science 2/7/17 – Shark Find in Belize

FIU researcher Demian Chapman and a possible new species of Bonnethead. Source: FIU 

A new species of Bonnethead has been described in Belize by FIU researcher Demian Chapman, thus the scenario of a single widespread species in that region now becomes the story of one or more species with overlapping ranges. The discovery was made after analyzing a snippet of the shark’s genome.

DNA analysis has allowed a much more nuanced perspective on species-level differences beyond the physical characteristics that were once the focus of classically-trained taxonomists. Now scientists are able to classify variance on a genetic level and have refined the technique. Now researchers use a method called DNA barcoding, which needs to examine just a small portion of an animal’s genomic sequence, and is often compared to scanning groceries at your supermarket’s checkout line. Large-scale efforts to catalog and archive these genetic identifiers, such as Barcode of Life, make this data widely accessible.


In addition, this finding was part of a larger initiative, called Finprint, focused on filling in data gaps concerning sharks, fins, and rays – all of which constitute a group of cartilaginous fish known as elasmobranchs. Finprint uses baited remote underwater video (BRUV) as one of their primary tools for studying these creatures. Much of their work appears to be focused on their spatial distribution, identifying regions that could lead to conflict with other uses such as fishing or areas that can be marked as candidates for protection.

 

Discovery from the Otter Side

While this is an amazing story, the urge to not post all the otter jokes is a fight I may lose.

Sherlotter Holmes and John Beaverson

All joking (briefly) aside, the Journal of Systematic Palaeontology just published findings about the otter species Siamogale melilutra as described by Wang et al. Skeletal pieces from three individuals were recovered in western China and used to characterize the ancient otter who outguns the giant river otter of today in size (approximately 50 kg to the giant otter’s 34).

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Giant River Otter. Photo Credit: Ernane Junior, Your Shot, National Geographic

While the specimens had elements reminiscent of both otters and badgers, a few distinctive features allowed researchers to place the animals firmly in subfamily Lutrinae, home to 13 current day otter species. However the paper notes the mixture of characteristics, described in some other genera as well, lead to some interesting questions about the ways in which the two may be related.

On the tail of this amazing find, I share an interesting otter fact which upon learning some years ago, quickly escalated their status in my heart: sea otters have loose folds of skin under their arms they use as pockets for storing food and rocks to use as tools.

I will close with the following video as it would be an otter shame not to:

Speck of Science 1/24/16 – Bees of the Seas

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Many of nature’s means of doing business on land has aquatic parallels. Seagrasses produce seeds and pollen the same way as terrestrial grasses do. However, there are certainly some differences. The pollen grains of seagrasses dwarf their land-based counterparts at almost 50 times larger, and the physics of the water in which pollination occurs certainly follows rules vastly different than those air currents.

Scientists have been postulating for some time about how marine plants get the job done in such a different environment, evident in this 1976 abstract for a submission in Letters to Nature.  Many aquatic plants may reproduce by variations of self-cloning where a sexual partner is not needed to give rise to new individuals. Sea grasses often dabble in a little of both worlds, as both have their evolutionary advantages. Cloning, often referred to more specifically as vegetative propagation in plants, allows underwater flora to quickly take up real estate without expending as many resources.  However, sexual reproduction confers the benefits of genetic variation and adaptability into their populations.

Initially, it was suggested water bore the primary burden of transporting pollen grains from male to female seagrass plants. However, in 2009, a team of researchers from National Autonomous University of Mexico led by  Brigitta van Tussenbroek observed small invertebrate crustaceans visiting turtlegrass (Thalassia testudinum) flowers in a manner that reminded them of terrestrial bees.

To explore whether or not these small creatures had the capacity to truly serve as pollinators, they moved their exploration in the controlled setting of a laboratory. They put turtlegrass and pollinators in tanks sans current, and monitored the movement of pollen grains as well as successful instances of pollination. Both successfully occurred in tanks where crustaceans had been added, but not in tanks where the animals were absent. The research team coined a new term, zoobenthophilous pollination, to describe the marine process they observed.

Seagrasses are vital to human wellbeing in ways similar to oyster reefs, coral reefs, and mangroves, and provide a wealth of services to the environments they thrive in. They are an important food source for manatees, dugongs, turtles, and other creatures. Their root systems stabilizes sea floors. They may serve as nursery grounds for minuscule juvenile fish needing protection from predators. But seagrasses have seen vast decline worldwide, in what could be called a global crisis. Now that we are learning seagrass survival may also have dependence on pollinators, we can only hope we do a better job of conserving these little sea bees than we have their terrestrial counterparts.

Speck of Science 12/1/16 – How Elephants Are Losing Their Tusks

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Small-tusked elephant, source: African Wildlife Foundation

Nature has a fickle way of removing the wheat from the chaff. When organisms are less suited to survival, their chances of lasting long enough to reproduce may be in serious jeopardy. If the deleterious traits are genetic in nature, then there is limited chance they will be handed off to future generations. We call this process natural selection.

One example proving that humans can act as a shaping force similar to mother nature by chiseling the genetic outlook  of a creature is presented in this recent Independent article.The piece describes how African elephants in some regions are being born with smaller tusks or entirely without them, presumably in response to the selective pressure of poaching. While there always have been an elephant here or there born without tusks, the preferential culling of ivory has increased the prevalence of tuskless elephants.

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Photo credit: National Geographic

However, as Snopes suggests (not a source I was expecting to comment on the issue), this particular phenomenon has been noted and written about for years prior. A 1995 paper published in the African Journal of Ecology noted in Queen Elizabeth National Park had jumped from 3-4% up to 9-25%. Collectively in South Luangwa National Park and nearby Lupande Game Management Area, the change was from 10% up to 38% in a 20 year period.

While elephants may be the charismatic mascot for poaching issues, undoubtedly it is an issue that for a multitude of animal species reverberates well beyond just their population size and deeply into the very tapestry of their DNA.