NEWSLETTER 03/2013 23. March 2013

 

Acrolamna crassicornis
Alopias hermani
Araloselachus agespensis
Galeocerdo cheganicus
Glueckmanotodus kamyshinensis
Glueckmanotodus karatauensis
Heptranchias karagalensis
Hexanchus tusbairicus
Karaisurus demidkini
Palaeohypotodus volgensis
Paraorthacodus turgaicus
Parotodus mangyshlakensis
Ptychocorax aulaticus
Striatolamia sibirica
Tobolamna levinae
Usakias wardi
Araloselachus aralensis
Carcharias praecrassidens
Borealotodus borealis
Squalicorax praeyangaensis
Trigonotodus tusbairicus
Araloselachus aralensis
Lamiostoma stolarovi
Notorynchus lerichei
Macrorhizodus nolfi
Acrolamna acuminata dilatata
Ptychocorax hybodontoides
Squalicorax volgensis
Cretalamna appendiculata
 

 

Posted February 26, 2013
Using CAT scans and making 3-D virtual reconstructions of the jaws of the ancient fish Helicoprion, Idaho State University researchers have solved some of the mysteries surrounding large spiral fossils of this fish's teeth.

The ISU Museum of Natural History has the largest public collection of Helicoprion spiral-teeth fossils in the world. The fossils of this 270-million-year-old fish have long mystified scientists because, for the most part, the only remains of the fish are its teeth because its skeletal system was made of cartilage, which doesn't preserve well. No one could determine how these teeth – that look similar to a spiral saw blade – fit into a prehistoric fish with a poor fossil record, long assumed to be a species of a shark.
"New CT scans of a unique specimen from Idaho show the spiral of teeth within the jaws of the animal, giving new information on what the animal looked like, how it ate," said Leif Tapanila, principal investigator of the study, who is an ISU Associate Professor of Geosciences and Idaho Museum of Natural History division head and research curator.
The results of the study, "Jaws for a spiral tooth-whorl: CT images reveal novel adaptation and phylogeny in fossil Helicoprion," are being published in the Royal Society's journal, Biology Letters. The Royal Society, based in London, England, is a self-governing fellowship of approximately 1,450 of the world's most distinguished scientists, including more than 80 Nobel Laureates.

In the IMNH's Idaho Virtualization Laboratory Tapanila and his colleagues have virtual reconstructions of the Helicoprion's jaws, based on firm evidence, that clear up the biggest mystery surrounding these teeth.
"We were able to answer where the set of teeth fit in the animal," Tapanila said. "They fit in the back of the mouth, right next to the back joint of the jaw. We were able to refute that it might have been located at the front of the jaw."
Located in the back of the jaw, the teeth were "saw-like," with the jaw creating a rolling-back and slicing mechanism. The Helicoprion also likely ate soft-tissued prey such as squid, rather that hunting creatures with hard shells.
Another major find was that this famous fish, presumed to be a shark, is more closely related to ratfish, than sharks. Both of these species are fish with cartilage for a skeletal structure, rather than bone, but they are classified differently.

"It was always assumed that the Helicoprion was a shark, but it is more closely related to ratfish, a Holocephalan," Tapanila said. "The main thing it has in common with sharks is the structure of its teeth, everything else is Holocephalan."
Based on the 3-D virtual reconstruction of the Helicoprian's jaw, the ISU researcher can infer other characteristics about the fish. Using this information, the Idaho Museum of Natural History is creating a full-bodied reconstruction of a modest-sized, 13-foot long Helicoprion, which probably grew as long as 25 feet. This model will be part of the IMNH's new Helicoprion exhibit that will open this summer, which includes artwork by Ray Troll, a well-regarded scientific illustrator as well as a fine arts artist.
The ISU team of researchers on this project included Tapanila, Jesse Pruitt, Alan Pradel, Cheryl D. Wilga, Jason B. Ramsay, Robert Schlader and Dominique Didier. Support for the project, which will include three more scientific studies on different aspects of the Helicoprion, was provided by the National Science Foundation, Idaho Museum of Natural History, American Museum of Natural History, University of Rhode Island and Millersville University.
For more information about the Idaho Virtualization Laboratory, visit vl.imnh.isu.edu.
For more information on the Royal Society, visit royalsociety.org/.
Contact information for Leif Tapanila is 208-282-3871 or
tapaleif@isu.edu.

Mar. 12, 2013 — A tagging study has revealed that porbeagle sharks in the Gulf of St. Lawrence could severely impact the number of migrating American eels in the region.

Canadian researchers tagged eight adult eels in the St. Lawrence River as part of the Ocean Tracking Network's investigation to uncover the eels' pathway through the Gulf to spawning grounds in the Sargasso Sea -- a journey that has mystified scientists for over a century.

Adult eels have never been seen in the Sargasso Sea. The researchers hoped to track their eels right into the Sea to precisely document spawning areas. Eight eels from the St. Lawrence River in Quebec were tagged with satellite "pop-up tags." All eight tags detached from the eels and surfaced prematurely, suggesting the eels' untimely death.

Seven tags transmitted data which included swimming depths, times, dates, and sea temperatures. Six tags recorded a sharp and sustained spike in temperature. Water temperatures in the Gulf of St. Lawrence in October range between 0 -- 10°C. Tags recorded temperatures of 22 -- 28°C -- stomach temperatures of warm-bodied pelagic fishes.

The ingested tags continued to record data on the dive patterns and depths of the animal. By comparing the known diving and depth patterns of porbeagle sharks and bluefin tuna to those recorded by the tags, investigators identified porbeagle sharks as the predators. On March 11, the Convention on International Trade in Endangered Species voted for greater protection of five shark species including porbeagle sharks.

Julian Dodson, professor at Laval University and OTN principal investigator, coauthored the study. "Both species are in trouble, and measures to conserve one may well be at odds with efforts to protect the other. What we really need now are studies to quantify just how important eels are in the diets of sharks and just what impact shark predation has on eel abundance."

In addition to pop-up tags, investigators also fitted an additional 113 eels with acoustic tags. These simpler tags broadcast only their identity and are detected by receivers moored in the ocean. Only four of the 113 eels leaving the Gulf of St. Lawrence for the Atlantic Ocean were detected on the OTN acoustic array in the Cabot Strait. The information suggests that the porbeagle sharks are taking a heavy toll on the migrating eels.

"We could hope that there will be increased pressure to protect eels in fresh water, particularly during downstream migration through power dams," says Mélanie Beguer-Pon, OTN researcher at Laval University. "We can't do anything about shark predation, but we can limit mortality in turbines."

The study was conducted by Mélanie Beguer-Pon, José Benchetrit and Julian Dodson (OTN, Laval University), with Martin Castonguay (OTN, DFO-IML), Kim Aarestrup (OTN, NIAR-Denmark), Steven Campana (DFO-BIO) and Michael Stokesbury (OTN, Acadia University).

source: http://www.sciencedaily.com/releases/2013/03/130314110258.htm

ITES Makes Historic Decision to Protect Sharks and Rays