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:3/22/2017)... 2017   Neurotechnology , a provider of ... announced the release of the SentiVeillance 6.0 ... facial recognition using up to 10 surveillance, security ... The new version uses deep neural-network-based facial detection ... utilizes a Graphing Processing Unit (GPU) for enhanced ...
(Date:3/20/2017)... At this year,s CeBIT Chancellor Dr. Angela Merkel visited ... to the DERMALOG stand together with the Japanese Prime Minster Shinzo Abe. ... the largest German biometrics company the two government leaders could see the ... well as DERMALOG´s multi-biometrics system.   Continue Reading ... ...
(Date:3/13/2017)... , March 13, 2017 Future of security: Biometric Face ... ... DERMALOGs Face Matching enables to match face pictures against ... basis to identify individuals. (PRNewsFoto/Dermalog Identification Systems) ... DERMALOG,s "Face Matching" is the fastest software for biometric Face Matching ...
Breaking Biology News(10 mins):
(Date:3/23/2017)... ... ... to announce it has become the premiere team-building cooking event company in San Diego. ... as Illumina, HP and Qualcomm, and is ranked #1 in its category on Trip Advisor. ... new team building format, a way for teams to not only interact with one another ...
(Date:3/23/2017)... MILFORD, Mass. , March 23, 2017 ... leading partner to global in vitro diagnostics ... launch of the industry,s first multiplexed ... inherited disease testing by next-generation sequencing ... materials were developed with input from industry ...
(Date:3/23/2017)... ... March 23, 2017 , ... Ellen Matloff, president and ... Council (CTC) as a 2017 Women of Innovation® finalist. Matloff will be among ... Dinner. , The dinner recognizes women accomplished in science, technology, engineering and math ...
(Date:3/23/2017)... York , March 23, 2017 According ... plasma products and derivatives market is fragmented due to the presence of ... such as Proliant, Thermo Fisher , and Sigma-Aldrich, compete with ... these three companies, collectively, held more than 76% of this market ... As ...
Breaking Biology Technology: