Function and control of luminescence from lantern shark (Etmopterus spinax) photophores
(2010)
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- Authors
- Supervisors
- Mallefet, Jérôme
- Abstract
- (en) In the permanent darkness of the deep-sea, a vast majority of organisms including molluscs, crustaceans and fishes developed photogenic organs (= photophores) to produce their own light and assume numerous functions including predation avoidance, predation help and intraspecific communication. This amazing capability evolved in two shark families, the Etmopteridae (=lantern sharks) and the Dalatiidae, which totalised more than 50 different luminescent sharks i.e. about 10% of currently described shark species. As a matter of fact, however, this amazing phenomenon has been poorly studied in these cartilaginous fishes, in comparison with bony fishes. By using a model species (the velvet belly lantern shark, Etmopterus spinax), the present work aims to provide the first experimental data on the adaptive benefit and the physiological control of photophore luminescence in sharks. Results were obtained by different techniques including fluorescent microscopy, microphotospectrometry, pharmacology (and luminometry), and immunohistochemistry. E. spinax’s photophores are able to produce light before birth and appear as a multi-use tool that could help the shark in different behaviours including intraspecific signalling, camouflage by counterillumination, aposematism, and prey illumination. The luminescence physiological control from this shark’s photophores is complex and unique, involving hormonal [melatonin (induction), prolactin (induction) and α-MSH (inhibition)] but also nervous [GABA (inhibition), nitric oxide (modulation)] inputs. One of the main targets of these substances appears to be a melanocyte iris, which regulate the amount of light emitted to the outside by pigment dispersion/retraction. All these results suggest that the lantern sharks’ luminescence capability evolved from the Elasmobranch (sharks and rays) skin colour change mechanism, inefficient in deepwater niches.
- Affiliations
Citations
Claes, J. (2010). Function and control of luminescence from lantern shark (Etmopterus spinax) photophores. https://hdl.handle.net/2078.5/130176