SUMMARYStudy of the control mechanisms of light emission in invertebrates shows the involvement o... more SUMMARYStudy of the control mechanisms of light emission in invertebrates shows the involvement of several neurotransmitters. In ophiuroids, only one species (Amphipholis squamata) has so far been characterized for luminescence control, which seems to be cholinergic, with an influence of several excitatory and inhibitory neuromodulators (amino acids, catecholamines, neuropeptides S1 and S2, purines). The aim of this work is to investigate the nature of control mechanisms of light emission in three luminous ophiuroid species, A. filiformis, O. aranea and O. californica, in order to see whether or not they share common mechanisms. Luminescence induced by general depolarisation of tissues using KCl (200 mmol l–1) shows different patterns, according to species. Only A. filiformis emits light in response to acetylcholine. In this species, the involvement of both muscarinic and nicotinic receptors is proposed, since atropine and tubocurarine (at 10–3 mol l–1) inhibited 99 % and 71 %, resp...
Bioluminescence is known to be of great ecological importance to a luminous organism but extremel... more Bioluminescence is known to be of great ecological importance to a luminous organism but extremely few studies investigate the ontogeny of luminous capabilities. The photogenic pattern of the velvet belly lantern shark Etmopterus spinax was investigated over ontogeny (14.0-52.5 cm total length) to determine the scaling of the surface area and the photophore density of different luminous zones as well as the ecological consequences of ontogenetic variations in bioluminescence efficiency. According to the luminous zone considered, different scaling patterns were found for the surface areas while the photophore densities of all zones scale with negative allometry, even though photophore insertion occurs. No sexual differences in these relationships were found. Luminous zones can be placed in two morphologically different groups: the "coverage" and the "isolated" zones. While counter-illumination is certainly the function of the former, the latter are probably involved in intraspecific behaviours. Due to the discrepancy between luminous capabilities of these two luminous zone categories, there is an ontogenetic increase in the luminescence heterogeneity of the luminous pattern as it was shown by luminescence modelling and confirmed by direct observations of spontaneous luminescence in living sharks. This heterogeneity certainly represents a trade-off between an efficient ventral camouflage and a strong identification tool for intraspecific behaviours such as coordinate hunting, which would be particularly useful when E. spinax become fish eaters (>19 cm total length), and for sexual recognition in mature individuals.
SUMMARY Photophores (photogenic organs) of the lantern shark Etmopterus spinax are under hormonal... more SUMMARY Photophores (photogenic organs) of the lantern shark Etmopterus spinax are under hormonal control, with prolactin (PRL) and melatonin (MT) triggering the light emission. Differential sensitivity to these hormones in adult individuals suggests, however, that the luminescence of this shark is controlled by an additional mechanism. In this study, different techniques were used to investigate a potential modulator of E. spinax luminescence – nitric oxide (NO). NO synthase (NOS)-like immunoreactivity (IR) was found in the photocytes (photogenic cells) of the photophores. In addition, acetylated tubulin IR also supported the presence of nerves running through the photogenic tissue and innervating different structural elements of the photophores: photocytes, pigmented cells from the iris-like structure and lens cells. Pharmacological experiments confirmed a modulatory action of NO on the hormonally induced luminescence: NO donors sodium nitroprusside (SNP) and hydroxylamine decreas...
Summary Tomopteris helgolandica Greeff 1879 (Tomopteridae) is a transparent holoplanktonic polych... more Summary Tomopteris helgolandica Greeff 1879 (Tomopteridae) is a transparent holoplanktonic polychaete that can emit a bright light. In this work, we investigated the emission pattern and control of this deep-sea worm's luminescence. Potassium chloride depolarisation applied on anesthetised specimens triggered a maximal yellow light emission from specific parapodial sites, suggesting that a nervous control pathway was involved. A pharmacological screening revealed a sensitivity to carbachol, which was confirmed by a dose-light response associated with a change in the light emission pattern, where physiological carbachol concentrations induced flashes and higher concentrations induced glows. The light response induced by its hydrolysable agonist, acetylcholine, was significantly weaker but was facilitated by eserine pretreatment. In addition, a specific inhibitory effect of tubocurarine was observed on carbachol-induced emission. Lastly, KCl- and carbachol-induced light responses ...
SUMMARYWe investigated the effects of cyclic nucleotides (cGMP and cAMP) and inositol triphosphat... more SUMMARYWe investigated the effects of cyclic nucleotides (cGMP and cAMP) and inositol triphosphate/diacylglycerol pathways on the KCl-induced luminescence control of the ophiuroid species Amphiura filiformis, Ophiopsila aranea and Ophiopsila californica. Results show that dibutyrylcGMP, the cGMP analogue, and sodium nitroprusside, the guanylyl cyclase activator, had no effect on the luminescence of O. aranea and O. californica. On the other hand, cGMP could be involved in an inhibitory control in A. filiformis. Dibutyryl-cAMP, the cAMP analogue, and forskolin, the adenylyl cyclase activator, had no effect on maximal light emission, but the adenylyl cyclase inhibitors MDL-12,330A and SQ22,536 affected the kinetics of light production in both Ophiopsilaspecies and strongly reduced KCl-induced luminescence in A. filiformis and O. aranea, suggesting cAMP pathway involvement in photogenesis. The phospholipase C inhibitor U-73122 also strongly reduced KCl-induced luminescence in all three...
SUMMARYStudy of the control mechanisms of light emission in invertebrates shows the involvement o... more SUMMARYStudy of the control mechanisms of light emission in invertebrates shows the involvement of several neurotransmitters. In ophiuroids, only one species (Amphipholis squamata) has so far been characterized for luminescence control, which seems to be cholinergic, with an influence of several excitatory and inhibitory neuromodulators (amino acids, catecholamines, neuropeptides S1 and S2, purines). The aim of this work is to investigate the nature of control mechanisms of light emission in three luminous ophiuroid species, A. filiformis, O. aranea and O. californica, in order to see whether or not they share common mechanisms. Luminescence induced by general depolarisation of tissues using KCl (200 mmol l–1) shows different patterns, according to species. Only A. filiformis emits light in response to acetylcholine. In this species, the involvement of both muscarinic and nicotinic receptors is proposed, since atropine and tubocurarine (at 10–3 mol l–1) inhibited 99 % and 71 %, resp...
Bioluminescence is known to be of great ecological importance to a luminous organism but extremel... more Bioluminescence is known to be of great ecological importance to a luminous organism but extremely few studies investigate the ontogeny of luminous capabilities. The photogenic pattern of the velvet belly lantern shark Etmopterus spinax was investigated over ontogeny (14.0-52.5 cm total length) to determine the scaling of the surface area and the photophore density of different luminous zones as well as the ecological consequences of ontogenetic variations in bioluminescence efficiency. According to the luminous zone considered, different scaling patterns were found for the surface areas while the photophore densities of all zones scale with negative allometry, even though photophore insertion occurs. No sexual differences in these relationships were found. Luminous zones can be placed in two morphologically different groups: the "coverage" and the "isolated" zones. While counter-illumination is certainly the function of the former, the latter are probably involved in intraspecific behaviours. Due to the discrepancy between luminous capabilities of these two luminous zone categories, there is an ontogenetic increase in the luminescence heterogeneity of the luminous pattern as it was shown by luminescence modelling and confirmed by direct observations of spontaneous luminescence in living sharks. This heterogeneity certainly represents a trade-off between an efficient ventral camouflage and a strong identification tool for intraspecific behaviours such as coordinate hunting, which would be particularly useful when E. spinax become fish eaters (>19 cm total length), and for sexual recognition in mature individuals.
SUMMARY Photophores (photogenic organs) of the lantern shark Etmopterus spinax are under hormonal... more SUMMARY Photophores (photogenic organs) of the lantern shark Etmopterus spinax are under hormonal control, with prolactin (PRL) and melatonin (MT) triggering the light emission. Differential sensitivity to these hormones in adult individuals suggests, however, that the luminescence of this shark is controlled by an additional mechanism. In this study, different techniques were used to investigate a potential modulator of E. spinax luminescence – nitric oxide (NO). NO synthase (NOS)-like immunoreactivity (IR) was found in the photocytes (photogenic cells) of the photophores. In addition, acetylated tubulin IR also supported the presence of nerves running through the photogenic tissue and innervating different structural elements of the photophores: photocytes, pigmented cells from the iris-like structure and lens cells. Pharmacological experiments confirmed a modulatory action of NO on the hormonally induced luminescence: NO donors sodium nitroprusside (SNP) and hydroxylamine decreas...
Summary Tomopteris helgolandica Greeff 1879 (Tomopteridae) is a transparent holoplanktonic polych... more Summary Tomopteris helgolandica Greeff 1879 (Tomopteridae) is a transparent holoplanktonic polychaete that can emit a bright light. In this work, we investigated the emission pattern and control of this deep-sea worm's luminescence. Potassium chloride depolarisation applied on anesthetised specimens triggered a maximal yellow light emission from specific parapodial sites, suggesting that a nervous control pathway was involved. A pharmacological screening revealed a sensitivity to carbachol, which was confirmed by a dose-light response associated with a change in the light emission pattern, where physiological carbachol concentrations induced flashes and higher concentrations induced glows. The light response induced by its hydrolysable agonist, acetylcholine, was significantly weaker but was facilitated by eserine pretreatment. In addition, a specific inhibitory effect of tubocurarine was observed on carbachol-induced emission. Lastly, KCl- and carbachol-induced light responses ...
SUMMARYWe investigated the effects of cyclic nucleotides (cGMP and cAMP) and inositol triphosphat... more SUMMARYWe investigated the effects of cyclic nucleotides (cGMP and cAMP) and inositol triphosphate/diacylglycerol pathways on the KCl-induced luminescence control of the ophiuroid species Amphiura filiformis, Ophiopsila aranea and Ophiopsila californica. Results show that dibutyrylcGMP, the cGMP analogue, and sodium nitroprusside, the guanylyl cyclase activator, had no effect on the luminescence of O. aranea and O. californica. On the other hand, cGMP could be involved in an inhibitory control in A. filiformis. Dibutyryl-cAMP, the cAMP analogue, and forskolin, the adenylyl cyclase activator, had no effect on maximal light emission, but the adenylyl cyclase inhibitors MDL-12,330A and SQ22,536 affected the kinetics of light production in both Ophiopsilaspecies and strongly reduced KCl-induced luminescence in A. filiformis and O. aranea, suggesting cAMP pathway involvement in photogenesis. The phospholipase C inhibitor U-73122 also strongly reduced KCl-induced luminescence in all three...
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