Navigation Links
First fruitful, then futile: Ammonites or the boon and bane of many offspring
Date:4/23/2012

For 300 million years, they were the ultimate survivors. They successfully negotiated three mass extinctions, only to die out eventually at the end of the Cretaceous along with the dinosaurs: Ammonoids, or ammonites as they are also known, were marine cephalopods believed to be related to today's squid and nautiloids. Ammonoids changed their reproductive strategy early on in the course of evolution. However, what was once a successful initial strategy may well have proved to be a fatal boomerang at the end of the Cretaceous, as an international team of researchers headed by paleontologists from the University of Zurich demonstrate in a study recently published in the science journal Evolution.

Embryos already had coiled shells

At the beginning of their evolution, ammonoids had straighter shells, which, like other mollusks, they began to coil during the Devonian Period. The precise reason behind this change is unknown. The selection pressure in favor of more tightly coiled shells is believed to have sprung from the ammonoids' natural predators. As the scientists have now discovered, the shell change also affected the ammonoid embryos. "In the oldest ammonoids, the embryonic shells were considerably bigger and coiled less tightly than in later forms," explains Kenneth De Baets, a paleontologist at the University of Zurich, summing up the latest findings.

Smaller hatchlings, more offspring

There were two more evolutionary trends that coincided with the increasingly more tightly coiled shells: The size of the embryonic shells shrank increasingly over time the hatchlings became smaller and smaller. In parallel, the shell size of fully grown animals increased and, on the whole, the animals became increasingly bigger. Based on this, the researchers deduced that the number of offspring in ammonoids rocketed during the Devonian Period. This is confirmed by discoveries of substantial clusters of fossilized embryonic shells at the end of the Devonian Period and more recent deposits.

"The large number of offspring could have been the key to the rapid proliferation of the ammonoids in the aftermath of each mass extinction," De Baets suspects. His hypothesis is supported by the fact that precisely the groups with smaller, loosely coiled embryonic shells and proportionately fewer offspring died out in certain Devonian extinction events. Nevertheless, the once successful reproductive strategy of many offspring appears to have turned against them at the end of the Cretaceous Period: The ammonoids died out. Only nautiloids have survived until today: They are characterized by large young and a small number of offspring. Exactly how this circumstance had a positive impact upon the survival of the nautiloids is unknown. All that is clear, according to De Baets, is that nautiloids are extremely vulnerable with their reproductive strategy nowadays in view of overfishing.


'/>"/>
Contact: Kenneth Da Baets
kenneth.debaeats@pim.uzh.ch
41-446-342-347
University of Zurich
Source:Eurekalert  

Related biology news :

1. Putting plants online: 4 leading botanical gardens to create first online catalog of all plants
2. ORNL microscopy yields first proof of ferroelectricity in simplest amino acid
3. First description of a triple DNA helix in a vacuum
4. Scientists complete first-ever emperor penguin count from space
5. First mass extinction linked to marine anoxia
6. New technology tracks sparrow migration for first time from California to Alaska
7. FirstMark Exhibiting at the Inaugural Atlanta Clinical Cardiology Update
8. FirstMark Announces New Hire Jay Houtman as Southeast Regional Sales Manager
9. First complete full genetic map of promising energy crop
10. Ottawa researchers to lead world-first clinical trial of stem cell therapy for septic shock
11. American College of Rheumatology releases first classification criteria for polymyalagia rheumatica
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
First fruitful, then futile: Ammonites or the boon and bane of many offspring
(Date:3/7/2017)... England , March 7, 2017 Brandwatch , ... chosen by The Prince,s Trust to uncover insights to ... across The Trust. The UK,s leading youth charity will ... social campaign results and get a better understanding of the topics ... ...
(Date:3/2/2017)... 2017 Summary This report provides ... KGaA and its partnering interests and activities since 2010. ... Description The Partnering Deals and Alliance since 2010 report ... one of the world,s leading life sciences companies. ... to ensure inclusion of the most up to date ...
(Date:2/28/2017)... --  Acuant , a leading provider of data capture ... new and core technologies building upon the acquisition of ... desktop Acuant FRM TM facial recognition and match ... manual review of identity documents by accredited professionals. ... most accurate capture software to streamline workflows by securely ...
Breaking Biology News(10 mins):
(Date:3/24/2017)... , March 24, 2017 On ... trading session at 5,817.69, down 0.07%; the Dow Jones ... and the S&P 500 closed at 2,345.96, marginally dropping ... sectors closed in green, 4 sectors finished in red, ... Friday, Stock-Callers.com has initiated reports coverage on the following ...
(Date:3/23/2017)... , ... March 23, 2017 , ... ... material that exhibits both viscous and elastic characteristics when deformed, which is identical ... exhibits properties to gently absorb compressive forces and return to its natural state ...
(Date:3/23/2017)... 23, 2017  Northwest Biotherapeutics (OTCQB: NWBO) (NW ... therapies for solid tumor cancers, today announced that ... it announced last Friday, March 17, 2017. ... investors securities totaling 28,843,692 shares, comprised of 18,843,692 ... shares of Class C Warrants pre-funded at the ...
(Date:3/23/2017)...  BioPharmX Corporation (NYSE MKT: BPMX), a specialty ... today reported financial results for the quarter and ... an update on the company,s clinical development efforts ... are pleased to report that last year was ... Anja Krammer. "We achieved key clinical milestones and ...
Breaking Biology Technology: