Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Smalleye pigmy sharks' bellies shine

26.04.2012
Smalleye pigmy sharks glow for camouflage

Some sharks deserve a blood curdling reputation, but not the diminutive smalleye pigmy shark (Squaliolus aliae). Reaching a maximum length of only 22cm, the tiny animals are more likely to be on someone else's menu. Silhouetted against weak light penetrating from the surface, the tiny sharks should be most at risk from predators approaching from below.

However, Julien Claes from Université catholique de Louvain, Belgium, explains that the minute sharks have evolved a handy trick. Their undersides are covered in tiny light-emitting photophores that probably fill in their telltale silhouettes. Adding that the distantly related velvet belly lantern sharks have adopted this luminous tactic for camouflage and communication, Claes and colleague Jérôme Mallefet were curious to discover whether pigmy sharks had acquired bioluminescence from the same origin, or developed the ability independently. The duo publish their discoveries that pigmy sharks glow for camouflage and that they probably share an ancestor in common with lantern sharks because they use similar mechanisms to regulate their glows in The Journal of Experimental Biology at http://jeb.biologists.com.

Teaming up with Hsuan-Ching Ho from the National Dong Hwa University, Taiwan, the scientists went trawling for smalleye pigmy sharks off the Taiwanese coast. Back in the lab, the team collected samples of the fish's skin, injected substances – ranging from neurotransmitters to hormones, which are known to regulate a wide range of biological processes – and waited to see whether the skin began glowing. Recording the time when the skin started producing light, and the maximum intensity and duration of light production, the team discovered that the hormone melatonin – which stimulates light production in the lantern sharks – made the smalleye pigmy shark's skin glow, while the neurotransmitters – which regulate light production in deep-sea bony fish – had no effect at all.

However, when the team applied prolactin to the glowing skin, they were in for a surprise: the glow faded. Instead of stimulating 30-min-long bursts of glowing light – as it does for lantern sharks – prolactin dimmed the sharks' glow, which, according to Claes, is intriguing from two perspectives.

He explains that in addition to using continual bioluminescence for camouflage, lantern sharks communicate using bursts of glowing of light from patches of skin on the pectoral and pelvic fins. They regulate this specific form of bioluminescence with the hormone prolactin. Having discovered that smalleye pigmy sharks use prolactin to inhibit light emission and that the photophores were restricted to the shark's lower surface, Claes and Mallefet concluded that instead of using bioluminescence for communication, the smalleye pigmy sharks use it purely for camouflage.

The team also explains that the lantern and pigmy sharks inherited their bioluminescence from an ancient predecessor, which used hormones to regulate skin pigmentation for camouflage. According to Claes, this ancient predecessor probably used melatonin to lighten the skin while using prolactin to darken the skin. The team says that smalleye pigmy and lantern sharks regulate their bioluminescence by adjusting the degree of pigmentation in cells covering the photophores. However, the pigmy shark has retained the pigment-mobilising effect of the ancestor's prolactin, which dims their glow by darkening the skin covering the photophores, whereas the lantern sharks have adapted prolactin to lighten the skin and emit light for communication. This suggests that the smalleye pigmy shark is more closely related to their ancient ancestor than the lantern shark.

REFERENCE: Claes, J. M., Ho, H.-C. and Mallefet, J. (2012) Control of luminescence from pigmy shark (Squaliolus aliae) photophores. J. Exp. Biol. 215, 1691-1699.

This article is posted on this site to give advance access to other authorised media who may wish to report on this story. Full attribution is required, and if reporting online a link to jeb.biologists.com is also required. The story posted here is COPYRIGHTED. Therefore advance permission is required before any and every reproduction of each article in full. PLEASE CONTACT permissions@biologists.com

Kathryn Knight | EurekAlert!
Further information:
http://www.biologists.com

More articles from Life Sciences:

nachricht Individual Receptors Caught at Work
19.10.2017 | Julius-Maximilians-Universität Würzburg

nachricht Rapid environmental change makes species more vulnerable to extinction
19.10.2017 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Electrode materials from the microwave oven

19.10.2017 | Materials Sciences

New material for digital memories of the future

19.10.2017 | Materials Sciences

Physics boosts artificial intelligence methods

19.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>