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 firstname.lastname@example.org
Kathryn Knight | EurekAlert!
Researchers identify potentially druggable mutant p53 proteins that promote cancer growth
09.12.2016 | Cold Spring Harbor Laboratory
Plant-based substance boosts eyelash growth
09.12.2016 | Fraunhofer-Institut für Angewandte Polymerforschung IAP
Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.
Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
09.12.2016 | Life Sciences
09.12.2016 | Ecology, The Environment and Conservation
09.12.2016 | Health and Medicine