NEWSLETTER 12/2010 24. Dezember 2010
I wish you and your family marry Christmas and a happy new year!
¡Feliz Navidad y próspero año nuevo! Buon Natale e felice anno nuovo!
Feliz Natal e próspero ano novo
Frohe Weihnachen und ein glücklichen neues Jahr!
Joyeux Noël et bonne année! Glædelig jul og godt nytår!
NEW PARTNERS:
Adrian Gleiss, Department of Pure and Applied Ecology, Institute of Environmental Sustainability, Swansea University, Singleton Park, Swansea, UK
Partner in Google-Maps
NEXT UPDATE:
Several times a week (new database software)
STATISTIC:
|
September
|
October
|
November
|
Dezember
|
|
papers:
|
9.985
|
10.165
|
11.415
|
11.729
|
|
recent:
|
7.213
|
7.439
|
8.631
|
9.004
|
|
fossil:
|
2.772
|
2.724
|
2.724
|
2.725
|
|
evaluated:
|
5.024
|
5.291
|
5.821
|
6.124
|
|
free downloading:
|
1.403
|
1.448
|
1.820
|
1.948
|
|
saved abstracts:
|
1.621
|
1.721
|
2.085
|
2.124
|
|
saved DOI
|
1.403
|
1.497
|
1.703
|
1.754
|
|
database entries „described species“
|
26.737
|
28.109
|
31.181
|
33.207
|
|
different species names
|
9.906
|
10.002
|
10.194
|
10.456
|
|
valid recent species
|
1.173
|
1.174
|
1.176
|
1.180
|
MEETINGS:
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35th Annual Larval Fish Conference
May 22-26, 2011
Wilmington
North Carolina
Meeting Web Site
27th Annual Meeting of the American Elasmobranch Society
July 6-11, 2011
Minneapolis
Minnesota
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SVP 71st Annual Meeting
November 2-5, 2011
Paris Las Vegas
Las Vegas, NV USA
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NEW FUNCTION OF THE WEBSITE:
List (pdf) of the papers of the year 2009 for download:
The downloadlink of the pdf is: http://www.shark-references.com/images/meine_bilder/downloads/Papers_2009.pdf
New: first description (digital version) of the following species:
X. CARCHARODON SEMISERRATUS Agass.
XI. CARCHARODON LANCEOLATUS Agass.
XII. CARCHARODON TOLIAPICUS Agass.
XIII. CARCHARODON HETERODON Agass.
XIV. CARCHARODON MEGALOTIS Agass.
XV. CARCHARODON LEPTODON Agass.
XVI. CARCHARODON DISAURIS Agass.
XVII. CARCHARODON SUBSERRATUS Agass.
XVIII. CARCHARODON ESCHERI Agass.
l. OTODUS OBLIQUUS Agass.
II. OTODUS LANCEOLATUS Agass.
III. OTODUS APPENDICULATUS Agass.
IV. OTODUS LATUS Agass.
V. OTODUS CRASSUS Agass.
VI. OTODUS SEMIPLICATUS Münst.
VII. OTODUS SERRATUS Agass.
VIII. OTODUS MACROTUS Agass.
IX. OTODUS TRICUSPIS Agass.
X. OTODUS SUBPLICATUS Münst.
XI. OTODUS TRIGONATUS Agass.
XII. OTODUS APICULATUS Agass.
XIII. OTODUS RECTICONUS Agass.
NEW PAPERS:
FOSSIL:
BOURDON, J. & EVERHART, M.J. (2010): Occurrence of the extinct Carpet shark, Orectoloboides, in the Dakota Formation (Late Cretaceous; Middle Cenomanian) of Kansas. Transactions of the Kansas Academy of Science, 113 (3-4): 237-242
SHIMADA, K. & NAGRODSKI, M. (2010): Occurrence of the Fossil Lamniform Shark, Cretoxyrhina mantelli, from the Upper Cretaceous Hartland Shale, Central Kansas. Transactions of the Kansas Academy of Science, 113 (3-4): 235-236
CLAESON, K.M. & O’LEARY, M.A. & ROBERTS, E.M. & SISSOKO, F. & BOUARÉ, M. & TAPANILA, L. & GOODWIN, D. & GOTTFRIED, M.D. (2010): New specimens, including the first record of lower dental plates, of the extinct myliobatid Myliobatis wurnoensis were recovered from the Maastrichtian (Late Cretaceous) of the Iullemmeden Basin, Mali, and are the oldest record of the taxon. We evaluated the phylogenetic position of this taxon with reference to other myliobatids (extinct and extant) using osteology and dentition. Our results indicate that Myliobatinae and Myliobatis are each paraphyletic, and that Aetobatus and Rhinoptera are monophyletic. We also found that taxa known only from the Cretaceous, Brachyrhizodus and Igdabatis, are highly nested within Myliobatidae. The phylogenetic position of these taxa unambiguously extends the origin of Myliobatidae and most of its representative taxa into the Mesozoic. Acta Palaeontologica Polonica, 55 (4): 655-674
HANKE, G.F. & WILSON, M.V.H. (2010): The putative stem-group chondrichthyans Kathemacanthus and Seretolepis from the Lower Devonian MOTH locality, Mackenzie Mountains, Canada. In: ELLIOTT, D.K. & MAISEY, J.G. & YU, X. & Desui MIAO (editors): Morphology, Phylogeny and Paleobiogeography of Fossil Fishes, Verlag Dr. Friedrich Pfeil: 159-182, 14 figs.
GINTER, M. (2010): Teeth of Late Famennian ctenacanth sharks from the Cleveland Shale. In: ELLIOTT, D.K. & MAISEY, J.G. & YU, X. & Desui MIAO (editors): Morphology, Phylogeny and Paleobiogeography of Fossil Fishes, Verlag Dr. Friedrich Pfeil: 145-158, 6 figs.
DE CARVALHO, M.R. (2010): Morphology and phylogenetic relationships of the giant electric ray from the Eocene of Monte Bolca, Italy (Chondrichthyes: Torpediniformes). In: ELLIOTT, D.K. & MAISEY, J.G. & YU, X. & Desui MIAO (editors): Morphology, Phylogeny and Paleobiogeography of Fossil Fishes, Verlag Dr. Friedrich Pfeil: 183-198, 9 figs.
BÖTTCHER, R. (2010): Description of the shark egg capsule Palaeoxyris friessi n. sp. from the Ladinian (Middle Triassic) of SW Germany and discussion of all known egg capsules from the Triassic of the Germanic Basin. Palaeodiversity, 3: 123–139
RECENT:
BORRELL, A. & CARDONA, L. & KUMARRAN, R.P. & AGUILAR, A. (2010): Trophic ecology of elasmobranchs caught off Gujarat, India, as inferred from stable isotopes. ICES Journal of Marine Science, in press Abstract: http://dx.doi.org/10.1093/icesjms/fsq170
BURGESS, G.H. & BUCH, R.H. & CARVALHO, F. & GARNER, B.A. & WALKER, C.J. (2010): Factors Contributing to Shark Attacks on Humans: A Volusia County, Florida, Case Study. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 541-566
DUDLEY, S.F.J. & CLIFF, G. (2010): Shark Control: Methods, Efficacy, and Ecological Impact. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 567-592
DULVY, N.K. & FORREST, R.E. (2010): Life Histories, Population Dynamics, and Extinction Risks in Chondrichthyans. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 639-680
EBERT, D.A. &WINTON, M.V. (2010): Chondrichthyans of High Latitude Seas. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 115-158
FRISK, M.G. (2010): Life History Strategies of Batoids. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 283-318
GELSLEICHTER, J. & WALKER, C.J. (2010): Pollutant Exposure and Effects in Sharks and Their Relatives. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 491-540
GLEISS, A.C. & NORMAN, B. WILSON, R.P. (2010): Moved by that sinking feeling: variable diving geometry underlies movement strategies in whale sharks. Functional Ecology, 2010: in press Abstract: http://dx.doi.org/10.1111/j.1365-2435.2010.01801.x
GRUBBS, R.D. (2010): Ontogenetic Shifts in Movements and Habitat Use. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 319-350
GUBILI, C. & BILGIN, R. & KALKAN, E. & KARHAN, S.Ü. & JONES, C.S. & SIMS, D.W. & KABASAKAL, H. & MARTIN, A.P. & NOBLE, L.R. (2010): Antipodean white sharks on a Mediterranean walkabout? Historical dispersal leads to genetic discontinuity and an endangered anomalous population. Proceedings of the Royal Society of London, Series B: in press Abstract: http://dx.doi.org/10.1098/rspb.2010.1856
HEITHAUS, M.R. & FRID, A. & VAUDO, J.J. & WORM, B. & WIRSING, A.J. (2010): Unraveling the Ecological Importance of Elasmobranchs. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 611-638
KAJIURA, S.M. & CORNETT, A.D. & YOPAK, K.E. (2010): Sensory Adaptations to the Environment: Electroreceptors as a Case Study. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 393-434
LITVINOV, F.F. (2010): "Management measures in elasmobranches fishery: crucial points in
life history of pelagic and demersal species." ICES CM 2010/E: 04: 1-20
MOURATO, B.L. & COELHO, R. & AMORIM, A.F. & CARVALHO, F.H.V. & HAZIN, F. & BURGESS, G. (2010): Size at maturity and length-weight relationships of the blurred lantern shark Etmopterus bigelowi (Squaliformes: Etmopteridae) caught off southeastern Brazil. Ciencias Marinas, 36 (4): 323-331
PAPASTAMATIOU, Y.P. & ITANO, D.G. & DALE, J.J. & MEYER, C.G. & HOLLAND, K.N (2010): Site fidelity and movements of sharks associated with ocean-farming cages in Hawaii. Marine and Freshwater Research, 61 (12): 1366-1375 Abstract: http://dx.doi.org/10.1071/MF10056
PORTNOY, D.S. (2010): Molecular Insights into Elasmobranch Reproductive Behavior for Conservation and Management. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 435-458
ROSA, R.S. & CHARVET-ALMEIDA,P. & DIBAN QUIJADA, C.C. (2010): Biology of the South American Potamotrygonid Stingrays. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 241-282
SCHLUESSEL, V. & BENNETT, M.B. & COLLIN, S.P. (2010): Diet and reproduction in the white-spotted eagle ray Aetobatus narinari from Queensland, Australia and the Penghu Islands, Taiwan . Marine and Freshwater Research, 61 (11): 1278-1289 Abstract: http://dx.doi.org/10.1071/MF09261
SHIVJI, M.S. (2010): DNA Forensic Applications in Shark Management and Conservation. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 593-610
SIMS, D.W. (2010): Tracking and Analysis Techniques for Understanding Free-Ranging Shark Movements and Behavior. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 351-392
SKOMAL, G. & BERNAL, D. (2010): Physiological Responses to Stress in Sharks. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 459-490
STEVENS, J.D (2010): Epipelagic Oceanic Elasmobranchs. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 3-36
WHITE, W.T. & SOMMERVILLE, E. (2010): Elasmobranchs of Tropical Marine Ecosystems. In: J.C. Carrier, J.A. Musick and M.R. Heithaus (Eds) Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. CRC Press, Boca Raton: 159-240
WHITTAMORE, J.M. & BLOOMER, C. & HANNA, G.M. & MCCARTHY, I.D. (2010): Evaluating ultrasonography as a non-lethal method for the assessment of maturity in oviparous elasmobranchs. Marine Biology, 157 (12): 2613-2624 Abstract: http://dx.doi.org/10.1007/s00227-010-1523-4
WIRSING, A.J. & RIPPLE, W.J. (2010): A comparison of shark and wolf research reveals similar behavioral responses by prey. Frontiers in Ecology and the Environment, 2010: in press Abstract: http://dx.doi.org/10.1890/090226
MISCELLANEOUS
Mediterranean sharks are Australian immigrants
Antipodean great whites took a wrong turn on the way to South Africa.
Joseph Milton
Mediterranean great white sharks are descended from Australian ancestors.David Fleetham/Corbis
The elusive great white sharks of the Mediterranean Sea may be descended from a single small Australian population that lost its bearings while visiting South Africa 450,000 years ago.
The great whites (Carcharodon carcharias) were probably returning to the Antipodes but became trapped after passing through the Straits of Gibraltar, according to a team led by marine biologist Leslie Noble of the University of Aberdeen, UK. The sharks have since made the Mediterranean their home because they reproduced there and, like salmon, the young always return to their birthplace.
Little is known about Mediterranean great whites — sightings are rare and tissue samples even rarer — but Noble and his colleagues teamed up with Turkish researchers to get access to samples from four sharks caught in fishing nets: two from Turkey, one from Tunisia and another from Sicily.
Their research, published today in Proceedings of the Royal Society B1, suggests that a combination of climate change, high sea levels and strong ocean currents around the South African coast could have driven the migrating Australian sharks off-course, up the west coast of Africa and east into the Mediterranean. But because the initial population was small, genetic variability in modern Mediterranean sharks seems to be limited — indicating that a lack of diversity could threaten their future survival. Female sharks from the nearby Atlantic do not seem to be migrating to the region, where they could help to replenish the stagnant gene pool.
Lost at sea
The researchers sequenced an area of the four sharks' mitochondrial DNA — DNA that is passed onto offspring from the mother and encodes proteins from cells' energy factories. The team was then able to compare the genetic code with a bank of sequences derived from great whites in waters of different parts of the world, including South Africa, Australia and the Atlantic.
Noble says the team was surprised to find that the section of DNA sequenced was identical in three of the four Mediterranean sharks, and showed that they were most closely related to Australian great whites. The team had expected to see more affinity with the nearer Atlantic or western Indian Ocean populations.
Great white sharks were once thought of as a coastal species, but research has shown that they migrate long distances in the open ocean — although scientists do not know exactly why. Tagged sharks have been seen travelling between the coasts of South Africa and southern Australia, and the authors suggest that it was probably during one of these excursions that a group took a wrong turn.
“I wouldn't like to speculate on the consequences for the Mediterranean if this population became extinct.”
The researchers used a molecular dating technique based on the number of differences between the DNA of the Mediterranean and Australian sharks to estimate that the sharks got lost during the Pleistocene epoch, around 450,000 years ago. Noble says that this was an period between ice ages: a time of high sea levels, climate change and, perhaps most importantly, an unusually fast-flowing ocean eddy off the east coast of South Africa called an Agulhas ring — which may explain why the sharks went so far astray.
The warm Agulhas Current flows down the east coast of Africa, but periodically an Agulhas ring carries its waters around the southern tip of the continent and into the Benguela Current off the west coast. "When sharks follow the Agulhas Current, the cooler waters of the Benguela probably alert them to turn east," says Nelson, "but an Agulhas ring is like a warm-water bubble." A group of sharks swimming in one of these bubbles could miss the turning and find the western coast of Africa between it and its desired destination.
The researchers speculate that the sharks then swam north until the Mediterranean basin gave them a chance to head east again. Once in the basin, they may have become trapped by the peninsulas and narrow channels of the Mediterranean.
A population in peril
Paulo Prodöhl, an evolutionary geneticist at Queen's University Belfast, UK, says that although the finding "comprises a precious and unique data set, the sample sizes are really too small to draw conclusive inferences". But he admits that because shark samples are so hard to get hold of, "you have to work with what you can get".
"We recognize the sample-size problem," says Noble. "We're trying to get another 50 Mediterranean samples, which could dramatically change our inferences — we're very keen to access museum material."
But, he says, "I don't think it removes the central tenet — that as far as we're aware, a significant proportion of the Mediterranean sharks are Australian in origin."
Noble also hopes that the work will highlight the plight of a potentially fragile shark population surviving in a polluted and over-fished sea. He says that great whites occupy a "pivotal role" in the Mediterranean, and the removal of top predators from other marine ecosystems has been disastrous.
"On the east coast of America, shark eradication has caused an 'ecological cascade'," says Noble. Populations of species on which sharks prey, such as seals and dolphins, have exploded, unbalancing the whole system. "It's been instrumental in helping kill off some of the shellfish," says Noble. "I wouldn't like to speculate on the consequences for the Mediterranean if this population became extinct."
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References
- Gubili, C., et al. Proc. R. Soc. B doi:10.1098/rspb.2010.1856 (2010).
Sharks and Wolves: Predator, Prey Interactions Similar on Land and in Oceans
ScienceDaily (Nov. 10, 2010) — There may be many similarities between the importance of large predators in marine and terrestrial environments, researchers concluded in a recent study, which examined the interactions between wolves and elk in the United States, as well as sharks and dugongs in Australia.
In each case, the major predators help control the populations of their prey, scientists said. But through what's been called the "ecology of fear" they also affect the behavior of the prey, with ripple impacts on other aspects of the ecosystem and an ecological significance that goes far beyond these species.
The study was done by scientists from Oregon State University and the University of Washington, and was published in Frontiers in Ecology and the Environment.
"For too long we've looked at ecosystem functions on land and in the oceans as if they were completely separate," said William Ripple, a professor in the Department of Forest Ecosystems at Society at OSU, and an international expert in the study of large predators such as wolves and cougars.
"We're now finding that there are many more similarities between marine and terrestrial ecosystems than we've realized," Ripple said. "We need to better understand these commonalities, and from them learn how interactions on land may be a predictor of what we will see in the oceans, and vice versa."
In this study, Ripple and collaborator Aaron Wirsing, a researcher with the School of Forest Resources at the University of Washington, compared what has been learned about wolf and elk interaction in Yellowstone National Park in the U.S. to the interplay of tiger sharks and dugongs in Shark Bay, Australia. Dugongs are large marine mammals, similar to manatees, that feed primarily on seagrasses and are a common prey of sharks.
In studies with elk, scientists have found that the presence of wolves alters their behavior almost constantly, as they try to avoid encounters, leave room for escape and are constantly vigilant. The elk graze less in sensitive habitats, which in Yellowstone is helping streamside shrubs and aspen trees to recover, along with other positive impacts on beaver dams and wildlife.
Conceptually similar activities are taking place between sharks and dugongs, the researchers found. When sharks are abundant, dugongs graze less in shallow water where they are most vulnerable to sharks, and sacrifice food they might otherwise consume. This allows the seagrass meadows to thrive, along with the range of other plant and marine animal species that depend on them.
Related marine interactions have been observed in the North Atlantic Ocean, Ripple said. As shark populations were diminished by overfishing, the number of rays increased, which in turn reduced the level of sea scallops, an important fishery.
The marine/terrestrial similarities are also reflected in the body condition and health of species, the researchers noted. In Shark Bay, green sea turtles are more willing to face risks from sharks and seek the best grazing areas when their body condition is strong. In like fashion, the common wildebeest on the African Serengeti are less vulnerable to attack by lions or hyenas when their physical condition is good.
A more frequent information exchange between terrestrial and marine ecologists could provide additional insights into ecosystem function, the researchers said in their report.
Journal Reference:
- Aaron J Wirsing, William J Ripple. A comparison of shark and wolf research reveals similar behavioral responses by prey. Frontiers in Ecology and the Environment, 2010; : 100722074133007 DOI: 10.1890/090226
Secrets of Sharks' Success: Flexible Scales Enable Fast Turning
ScienceDaily (Nov. 24, 2010) — New research from the University of South Florida suggests that one of the evolutionary secrets of the shark's success hides in one of its tiniest traits -- flexible scales on the bodies of these peerless predators that make them better hunters by allowing them to change directions while moving at full speed.
The key to this ability lies in the fact that the scales control water flow separation across the creatures' bodies, says Amy Lang of the University of Alabama who will present work she performed with her colleagues at the University of South Florida Nov. 23 at the American Physical Society's Division of Fluid Dynamics (DFD) annual meeting in Long Beach, CA.
Flow separation is an issue in systems like aircraft design, explains Lang, because it tends to cause vortices that impede speed and stability.
"In nature, if you look at surfaces of animals, you'll see that they are not smooth," she says. "They have patterns. Why? One common application of patterning a surface is to control flow -- think of the dimples of a golf ball that help the ball fly farther. We believe scales on fast-swimming sharks serve a similar purpose of flow separation control."
Based on experimental measurements and models of shark scales, Dr. Lang's team discovered that the bases of shortfin mako scales (literally small teeth covering their body) where they attach to the skin are not as wide as the tops of the scales. This tapered shape enables the scales to be easily manipulated to angles of 60 degrees or more, endowing them with movement called "denticle bristling."
Also, these flexible scales are only found on parts of the body where flow separation is most likely to occur, such as behind the gills on the side of the body. Denticle bristling is the probable mechanism leading to flow separation control for the shortfin mako shark.
"As we investigate further, we imagine applications of controlling flow separation in design of aircraft, helicopters, wind turbines -- anywhere flow separation is an issue," Lang adds.
This work is funded by the National Science Foundation.
Whale Sharks Use Geometry to Avoid Sinking
ScienceDaily (Nov. 27, 2010) — They are the largest fish species in the ocean, but the majestic gliding motion of the whale shark is, scientists argue, an astonishing feat of mathematics and energy conservation. In new research published November 25 in the British Ecological Society's journal Functional Ecology marine scientists reveal how these massive sharks use geometry to enhance their natural negative buoyancy and stay afloat.
For most animals movement is crucial for survival, both for finding food and for evading predators. However, movement costs substantial amounts of energy and while this is true of land based animals it is even more complex for birds and marine animals which travel in three dimensions. Unsurprisingly this has a profound impact on their movement patterns.
"The key factor for animal movement is travel speed, which governs how much energy an animal uses, the distance it will travel and how often resources are encountered," said lead author Adrian Gleiss from Swansea University. "However, oceanic animals not only have to consider their travel speed, but also how vertical movement will affect their energy expenditure, which changes the whole perspective."
For the past four years, Adrian Gleiss and Rory Wilson, from Swansea University, worked with Brad Norman from ECOcean Inc. to lead an international team to investigate the movements of whale sharks, Rhincodon typus, at Ningaloo Reef in Western Australia. They attached animal-borne motion sensors, accelerometers, to the free-swimming whale sharks to measure their swimming activity and vertical movement, which allowed them to quantify the energetic cost of vertical movement.
The team's data revealed that whale sharks are able to glide without investing energy into movement when descending, but they had to beat their tails when they ascended. This occurs because sharks, unlike many fish, have negative buoyancy.
Also, the steeper the sharks ascended, the harder they had to beat their tail and the more energy they had to invest. The Whale Sharks displayed two broad movement modes, one consisting of shallow ascent angles, which minimize the energetic cost of moving in the horizontal while a second characteristic of steeper ascent angles, optimized the energetic cost of vertical movement.
"These results demonstrate how geometry plays a crucial role in movement strategies for animals moving in 3-dimensions," concluded Gleiss. "This use of negative buoyancy may play a large part in oceanic sharks being able to locate and travel between scarce and unpredictable food sources efficiently."
Journal Reference:
- Adrian C. Gleiss, Brad Norman, Rory P. Wilson. Moved by that sinking feeling: variable diving geometry underlies movement strategies in whale sharks. Functional Ecology, 2010; DOI: 10.1111/j.1365-2435.2010.01801.x
