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Jérôme Mallefet - One of the best experts on this subject based on the ideXlab platform.
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In the intimacy of the darkness: Genetic polyandry in deep-sea luminescent lanternsharks Etmopterus spinax and Etmopterus molleri (Squaliformes, Etmopteridae).
Journal of fish biology, 2020Co-Authors: Laurent Duchatelet, Jérôme Mallefet, Nicolas Oury, Hélène MagalonAbstract:Multiple paternity seems common within elasmobranchs. Focusing on two deep-sea shark species, the velvet belly lanternshark (Etmopterus spinax) and the slendertail lanternshark (Etmopterus molleri) we inferred the paternity in 31 E. spinax litters from Norway (three to 18 embryos per litter) and six E. molleri litters from Japan (three to six embryos), using 21 and 10 specific microsatellites, respectively. At least two E. spinax litters were sired from multiple fathers each, with highly variable paternal skew (1:1 to 9:1). Conversely, no clear signal of genetic polyandry was found in E. molleri.
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Deep-sea sharks: Relation between the liver's buoyancy and red aerobic muscle volumes, a new approach
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2019Co-Authors: Nicolas Pinte, Mathilde Godefroid, Ouissam Abbas, Vincent Baeten, Jérôme MallefetAbstract:Abstract Shark's buoyancy depends on two types of force: (i) the hydrostatic force which is mainly provided by their liver filled with low density lipids and (ii) the hydrodynamic force which is provided by the morphology of their body and fins. Shallow-water shark species are usually negatively buoyant, whereas deep-sea shark species have been suggested to display neutral buoyancy. It has been suggested that species that are close to the neutrality would have less red aerobic muscle fibers. Here, we investigated several liver features (the hepatosomatic index, the oil content and the lipid composition) playing a major role regarding the buoyancy of three deep-sea shark species (Etmopterus molleri, Etmopterus spinax and Isistius brasiliensis) and one shallow-water counterpart (Galeus melastomus). We used FT-Raman and FT-MIR spectroscopy to qualify/quantify the lipid composition of their liver. Our results showed that most deep-sea shark species studied have liver features providing more buoyancy than their shallow-water counterparts, appart from E. molleri which shows liver's features that resemble more shallow-water shark species (e.g. G. melastomus). Finally, data regarding liver features of several deep-sea shark species from the literature were added and the red aerobic muscle distribution/proportion of nine species was measured, to reveal how these parameters might be related. Our results showed that sharks characterized by a liver providing more hydrostatic force possess proportionally less red aerobic muscles than sharks having a liver that contributes less to their buoyancy. Therefore, our results i.e. deep-sea shark displaying less red aerobic muscle with a liver providing more buoyancy, support low metabolic rates hence slow swimming speed.
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Etmopterus spinax the velvet belly lanternshark does not use bacterial luminescence
Acta Histochemica, 2019Co-Authors: Laurent Duchatelet, Jérôme Delroisse, Patrick Flammang, Jacques Mahillon, Jérôme MallefetAbstract:Abstract Marine organisms are able to produce light using either their own luminous system, called intrinsic bioluminescence, or symbiotic luminous bacteria, called extrinsic bioluminescence. Among bioluminescent vertebrates, Osteichthyes are known to harbor both types of bioluminescence, while no study has so far addressed the potential use of intrinsic/extrinsic luminescence in elasmobranchs. In sharks, two families are known to emit light: Etmopteridae and Dalatiidae. The deep-sea bioluminescent Etmopteridae, Etmopterus spinax, has received a particular interest over the past fifteen years and its bioluminescence control was investigated in depth. However, the nature of the shark luminous system still remains enigmatic. The present work was undertaken to assess whether the light of this shark species originates from a bioluminescent bacterial symbiosis. Using fluorescent in situ hybridization (FISH) and transmission electron microscopy (TEM) image analyses, this study supports the conclusion that the bioluminescence in the deep-sea lanternshark, Etmopterus spinax, is not of bacterial origin.
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isolation and characterization of 29 and 19 microsatellite loci from two deep sea luminous lanternsharks Etmopterus spinax and Etmopterus molleri squaliformes etmopteridae
Molecular Biology Reports, 2019Co-Authors: Nicolas Oury, Jérôme Mallefet, Laurent Duchatelet, Hélène MagalonAbstract:Etmopterus spinax (Linnaeus, 1758) and Etmopterus molleri (Whitley, 1939) are two bioluminescent deep-sea sharks, usually caught in large numbers as bycatch by deep-water fisheries. Yet, no study has ever involved population status of these two species using genetic tools. In order to investigate population genetic structure, diversity and connectivity of these two lanternsharks, 29 and 19 microsatellite loci were isolated from E. spinax DNA library for E. spinax and E. molleri, respectively. These loci were tested on 32 E. spinax individuals from the North Sea and seven E. molleri from the East China Sea. The number of alleles per locus ranged from 2 to 13. The observed heterozygosity ranged from 0.031 to 0.839 for E. spinax and from 0.000 to 1.000 for E. molleri, while the expected heterozygosity ranged from 0.031 to 0.903 and from 0.143 to 0.821, respectively. Almost all loci (24 and 16, respectively) were at Hardy–Weinberg equilibrium for both species and no linkage disequilibrium among loci was detected. These loci represent useful tools to better understand the population structure of these two species. Besides, they could also be suitable for other lanternsharks in general, as these latter remain largely understudied, specially in terms of understanding the basic science that will serve into their conservation.
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Additional file 1: of Etmopteridae bioluminescence: dorsal pattern specificity and aposematic use
2019Co-Authors: Laurent Duchatelet, Nicolas Pinte, Taketeru Tomita, Keiichi Sato, Jérôme MallefetAbstract:Animated GIF of MRI transversal section of Etmopterus spinax at the level of spine base, going from the tip to the base of the spine. (GIF 557 kb
Julien Claes - One of the best experts on this subject based on the ideXlab platform.
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comparative control of luminescence in sharks new insights from the slendertail lanternshark Etmopterus molleri
Journal of Experimental Marine Biology and Ecology, 2015Co-Authors: Julien Claes, Jérôme MallefetAbstract:Here, we investigated the organisation and physiological control of photophores from the slendertail lanternshark (Etmopterus molleri), an etmopterid species phylogenetically distant from E. spinax, one of the two current model species for shark photophore control study. Our results support the idea that lanternsharks evolved a common photophore control mechanism, more complex compared to that of dalatiid sharks, in order to use their luminescence as a versatile deep-sea tool.
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extraocular opsin detection in lanternshark Etmopterus spinax photogenic tissue
21th Benelux Congress of Zoology, 2014Co-Authors: Julien Claes, Jérôme Mallefet, Jérôme Delroisse, Laurent DuchateletAbstract:The velvet belly lanternshark (Etmopterus spinax) is a small deep-sea shark commonly found in the Eastern Atlantic and the Mediterranean Sea. As other members of the Etmopteridae family, it displays thousands of tiny epidermal light organs called photophores, which are composed of a cluster of photogenic cells (photocytes) enclosed in a pigmented sheath and topped by a shutter-like structure and a lens. These organs produce a blue-green light that is believed to be involved in numerous functions including camouflage by counterillumination, intraspecific communication and aposematism. According to recent pharmacological studies, this functional versatility is partly achieved thanks to a complex photophore control mechanism, which involves hormones and neural agents. Current experimental data suggest (i) photocytes and the shutter to be the main targets of these pharmacological substances, and (ii) the presence of a link between the targets since the shutter appears to open while photocytes are glowing and inversely. Here, we hypothesize extraocular opsins to endowe photophores with their own light perception (as it was recently shown in a bioluminescent squid) and hence to provide the link between shutter opening and photocyte activity. The present work uses various techniques including transcriptome analysis western blotting, immunohistochemistry to detect the presence of opsins in the shark’s photogenic tissue. Results confirm the presence of extraocular opsins associated with the photophores, which likely supports their involvement in the bioluminescence control mechanism.
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morphology and control of photogenic structures in a rare dwarf pelagic lantern shark Etmopterus splendidus
Journal of Experimental Marine Biology and Ecology, 2011Co-Authors: Julien Claes, Keiichi Sato, Jérôme MallefetAbstract:The shark genus Etmopterus encompasses numerous deep-sea species that are widely distributed throughout the world's oceans and share the capability to emit light thanks to numerous tiny epidermal photogenic organs called photophores. Despite the potential wide ecological interest of this light emission, it is still a poorly studied aspect of shark biology, mostly due to the challenges inherent to the study of uncommon deep-sea animals. During a collection trip in waters around Okinawa Island, we had the opportunity to collect, maintain and study specimens of Etmopterus splendidus, a small pelagic lantern shark that was not previously known from this area. Analyses show that (i) the photophore density of this species varies according to the different parts of the body, which led to a heterogeneous photogenic pattern; (ii) photophore harbour the classical structure found in other etmopterid sharks, i.e. a cluster of photocytes enclosed in a pigmented sheath and surmounted by pigmented and lens cells; (iii) the physiological control of these photophores appears similar to what was found in the distantly related Etmopterus spinax, i.e. including hormonal and neural inputs as well as the action of pigmented cells overlying the photocytes. These results indicate that E. splendidus luminescence is probably used for more than one purpose, and support the idea that the physiological control of lantern shark photophores was selected early in the evolution of these sharks.
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control of luminescence from lantern shark Etmopterus spinax photophores
Communicative & Integrative Biology, 2011Co-Authors: Julien Claes, Jérôme MallefetAbstract:The velvet belly lantern shark (Etmopterus spinax) is a common deep-sea shark that has been used, in the recent years, as a model for experimental studies on physiological control of shark luminescence. These studies demonstrated that, unlike any other luminous organism, the luminescence of this shark was under a dual control of hormones and neurotransmitters (or neuromodulators). This paper, by making a short review of histological and pharmacological results from these studies, aims to propose a first model of luminescence control in E. spinax.
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gaba inhibition of luminescence from lantern shark Etmopterus spinax photophores
Comparative Biochemistry and Physiology C-toxicology & Pharmacology, 2011Co-Authors: Julien Claes, Jenny Kronstrom, Susanne Holmgren, Jérôme MallefetAbstract:Photogenic organs (photophores) of the velvet belly lantern shark (Etmopterus spinax) are under hormonal control, since melatonin (MT) and prolactin (PRL) trigger luminescence while α-melanocyte-stimulating hormone (α-MSH) prevents this light to be emitted. A recent study supported, however, the presence of numerous nerve fibres in the photogenic tissue of this shark. Immunohistochemical and pharmacological results collected in this work support these nerve fibres to be inhibitory GABAergic nerves since (i) GABA immunoreactivity was detected inside the photogenic tissue, where previous labelling detected the nerve fibre structures and (ii) GABA was able to inhibit MT and PRL-induced luminescence, which was on the other hand increased by the GABA(A) antagonist bicuculline (BICU). In addition, we also demonstrated that BICU can induce light per se by provoking pigment retraction in the pigmented cells composing the iris-like structure of the photophore, attaining, however, only about 10% of hormonally induced luminescence intensity at 10(-3)molL(-1). This strongly supports that a GABA inhibitory tonus controls photophore "aperture" in the photogenic tissue of E. spinax but also that MT and PRL have more than one target cell type in the photophores.
Mallefet Jérôme - One of the best experts on this subject based on the ideXlab platform.
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Bioluminescence of the Largest Luminous Vertebrate, the Kitefin Shark, Dalatias licha: First Insights and Comparative Aspects
'Frontiers Media SA', 2021Co-Authors: Mallefet Jérôme, Stevens, Darren W., Duchatelet LaurentAbstract:Bioluminescence has often been seen as a spectacular yet uncommon event at sea but considering the vastness of the deep sea and the occurrence of luminous organisms in this zone, it is now more and more obvious that producing light at depth must play an important role structuring the biggest ecosystem on our planet. Three species of deepwater sharks (Dalatias licha, Etmopterus lucifer, and Etmopterus granulosus) were collected from the Chatham Rise, off New Zealand, and for the first time, we documented their luminescence. Comparison of glowing shark pictures, combined with histological description of light organs and hormonal control analysis, highlight the evolutive conservation of the bioluminescence process within Dalatiidae and Etmopteridae. A special emphasis is placed on the luminescence of D. licha, the largest known luminous vertebrate. This first experimental study of three luminous shark species from New Zealand provides an insight into the diversity of shark bioluminescence and highlights the need for more research to help understand these unusual deep-sea inhabitants: the glowing sharks
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In the intimacy of the darkness: Genetic polyandry in deep‐sea luminescent lanternsharks Etmopterus spinax and Etmopterus molleri (Squaliformes, Etmopteridae) and Etmopterus molleri
Wiley-Blackwell Publishing Ltd., 2020Co-Authors: Duchatelet Laurent, Oury Nicolas, Mallefet Jérôme, Magalon HélèneAbstract:Multiple paternity seems common within elasmobranchs. Focusing on two deep‐sea shark species, the velvet belly lanternshark (Etmopterus spinax) and the slendertail lanternshark (Etmopterus molleri) we inferred the paternity in 31 E. spinax litters from Norway (three to 18 embryos per litter) and six E. molleri litters from Japan (three to six embryos), using 21 and 10 specific microsatellites, respectively. At least two E. spinax litters were sired from multiple fathers each, with highly variable paternal skew (1:1 to 9:1). Conversely, no clear signal of genetic polyandry was found in E. molleri
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Bioluminescence in lanternsharks: Insight from hormone receptor localization
Academic Press, 2020Co-Authors: Duchatelet Laurent, Delroisse Jérôme, Mallefet JérômeAbstract:As part of the study of their bioluminescence, the deep-sea lanternshark Etmopterus spinax and Etmopterus molleri (Chondrichthyes, Etmopteridae) received growing interest over the past ten years. These mesopelagic sharks produce light thanks to a finely tuned hormonal control involving melatonin, adrenocorticotropic hormone and α-melanocyte-stimulating hormone. Receptors of these hormones, respectively the melatonin receptors and the melanocortin receptors, are all members of the G-protein coupled receptor family i.e. coupled with specific G proteins involved in the preliminary steps of their transduction pathways. The present study highlights the specific localization of the hormonal receptors, as well as of their associated G-proteins within the light organs, the so-called photophores, in E. spinax and E. molleri through immunohistofluorescence technic. Our results allow gaining insight into the molecular actors and mechanisms involved in the control of the light emission in Etmopterid sharks
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In the intimacy of the darkness: Genetic polyandry in deep‐sea luminescent lanternsharks Etmopterus spinax and Etmopterus molleri (Squaliformes, Etmopteridae)
'Wiley', 2020Co-Authors: Duchatelet Laurent, Oury Nicolas, Mallefet Jérôme, Magalon HélèneAbstract:International audienceMultiple paternity seems common within elasmobranchs. Focusing on two deep-sea shark species, the velvet belly lanternshark (Etmopterus spinax) and the slendertail lanternshark (Etmopterus molleri) we inferred the paternity in 31 E. spinax litters from Norway (three to 18 embryos per litter) and six E. molleri litters from Japan (three to six embryos), using 21 and 10 specific microsatellites, respectively. At least two E. spinax litters were sired from multiple fathers each, with highly variable paternal skew (1:1 to 9:1). Conversely, no clear signal of genetic polyandry was found in E. molleri
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Ecological features and swimming capabilities of deep-sea sharks from New Zealand
Elsevier BV, 2020Co-Authors: Pinte Nicolas, Parisot Pascaline, Martin Ulrich, Zintzen Vincent, De Vleeschouwer Christophe, Roberts, Clive D., Mallefet JérômeAbstract:Currently the ecology of deep-water sharks is poorly documented, especially in situ information for these elusive species are lacking. In this study, stereo-Baited Remote Underwater Videos (stereo-BRUVs) were deployed to collect ecological data from New Zealand deep-sea sharks. The results showed differences in abundance between species, with Etmopterus granulosus (Etmopteridae) found in greatest numbers. Moreover, the known depth range increased for Scymnodon macracanthus (Centrophiridae). Deep-sea shark species were generally found to swim at slower cruise speeds than their shallow-water counterparts. However, the swimming speed of deep-sea sharks was clearly not uniform, with some species displaying higher cruise swimming speeds than others. The fastest sharks (Centrophorus harrissoni, Etmopterus granulosus and Etmopterus molleri) had swimming abilities comparable to benthic shallow water sharks. The higher cruise swimming speed in the family Etmopteridae could be an advantage for these luminous sharks if they follow isolumes to match their ventral light intensity with the down-welling light of their environment. This study revealed that alternative non-destructive methods can be effective for ecological studies of deep-sea marine fauna
Nicolas Straube - One of the best experts on this subject based on the ideXlab platform.
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Intraspecific dental variations in the deep-sea shark Etmopterus spinax and their significance in the fossil record
Zoomorphology, 2020Co-Authors: Nicolas Straube, Jürgen PollerspöckAbstract:An important character on several taxonomic levels for shark identification is the tooth morphology. Sharks show a variety of highly specialized dentitions reflecting adaptations to their feeding habits. Intraspecific variation of tooth morphology such as sexual or ontogenetic dimorphism is poorly known in many species, even though tooth morphology plays a decisive role in the characterization of the fossil record of sharks, which comprises mostly fossil teeth. Here we analyzed the dentition of 40 jaws of the Velvet Belly Lantern Shark Etmopterus spinax and identified ontogenetic and sexual dimorphic characters such as total number of teeth, number of upper teeth, cusplet numbers in upper jaw teeth and width of lower jaw teeth. Dimorphic characters may reduce intraspecific competition for food, as E. spinax segregates by sex and size and may allow for identifying the male sex. The lower jaw tooth height, a sexually non-dimorphic character, was used to re-calculate the total length of specimens, which represents the first such approach for a squaliform shark. Results derived from the extant E. spinax are subsequently applied to fossil Etmopterus sp. teeth (Miocene) to gain individual information such as sex or size, but also characterize the extinct population from the excavation site by a size distribution profile in comparison to data from extant populations. This approach indicates the presence of multiple ontogenetic stages in the extinct population.
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Etmopterus alphus n. sp.: a new lanternshark (Squaliformes: Etmopteridae) from the south-western Indian Ocean
African Journal of Marine Science, 2016Co-Authors: Nicolas Straube, Rob Leslie, Simon WeigmannAbstract:A new species of lanternshark, Etmopterus alphus (Squaliformes: Etmopteridae), is described from the south-western Indian Ocean. The new species resembles other members of the ‘Etmopterus lucifer’ clade in having linear rows of dermal denticles and most closely resembles E. molleri from the south-western Pacific. The new species is fairly common along the upper continental slopes off central Mozambique, at depths between 472 and 558 m, and is also found on the southern Madagascar Ridge in 650–792 m depth. It can be distinguished from other members of the E. lucifer clade by a combination of characteristics, including arrangement of flank and caudal markings, dimension of flank markings and shape, size and arrangement of dermal denticles along the body. Molecular analysis further supports the distinction of E. alphus from other members of the E. lucifer clade.
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on the occurrence of the southern lanternshark Etmopterus granulosus off south africa with comments on the validity of e compagnoi
Deep-sea Research Part Ii-topical Studies in Oceanography, 2015Co-Authors: Nicolas Straube, David A. Ebert, Shannon Corrigan, Robin W Leslie, Paul J Clerkin, Elisabeth Rochel, Gavin J P NaylorAbstract:The Southern Lanternshark, Etmopterus granulosus, is a large species of Lanternshark that has been a source of long-standing taxonomic confusion. Recent work suggests E. granulosus to be conspecific with the New Zealand Giant Lanternshark, Etmopterus baxteri, suggesting that the species may be widespread throughout the Southern Hemisphere. The taxonomic affinity of populations off South Africa, however, has remained uncertain. Herein we show that South African samples are also conspecific with E. granulosus based on both molecular and morphometric data. These results extend the known distribution range of this species to South Africa and the southern Indian Ocean, strengthening the hypothesis that E. granulosus has a circum-Antarctic distribution. In addition we show that there is a cryptic, granulosus-like species in South African waters that can likely be assigned to Etmopterus compagnoi.
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Cryptic diversity and species assignment of large lantern sharks of the Etmopterus spinax clade from the Southern Hemisphere (Squaliformes, Etmopteridae)
Zoologica Scripta, 2010Co-Authors: Nicolas Straube, Jürgen Kriwet, Ulrich K. SchliewenAbstract:Straube, N., Kriwet, J. & Schliewen, U. K. (2010). Cryptic diversity and species assignment of large lantern sharks of the Etmopterus spinax clade from the Southern Hemisphere (Squaliformes, Etmopteridae). —Zoologica Scripta, 40, 61–75. Many species of the speciose deep-sea shark family Etmopteridae (lantern sharks) are a regular by-catch component of deepwater trawl and longline commercial fisheries. As for many elasmobranchs, the low fecundity, late sexual maturation and extreme longevity of the lantern sharks increase their susceptibility to overfishing. However, the taxonomic uncertainty within etmopterids and the poorly known patterns of dispersal of these shark species hampers the establishment of reasonable monitoring efforts. Here, we present the first molecular approach to clarify the taxonomy and distribution of a morphologically uniform group of lantern sharks comprising Etmopterus granulosus and closely related congeners by using nucleotide sequence data from the mitochondrial DNA cytochrome oxidase I gene and amplified fragment length polymorphisms. Samples were collected from several locations in the Southern Hemisphere, where the species occur. Our analyses reveal a high level of cryptic diversity. E. granulosus is not endemic to Chile, but instead has a widespread distribution in the Southern Hemisphere being synonymous to New Zealand Etmopterus baxteri. Conversely, specimens previously assigned to E. baxteri from off South Africa apparently represent a distinct species. Our results provide the basis for the re-description of E. granulosus and E. baxteri which will help in the establishment of useful monitoring and management strategies.
Laurent Duchatelet - One of the best experts on this subject based on the ideXlab platform.
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In the intimacy of the darkness: Genetic polyandry in deep-sea luminescent lanternsharks Etmopterus spinax and Etmopterus molleri (Squaliformes, Etmopteridae).
Journal of fish biology, 2020Co-Authors: Laurent Duchatelet, Jérôme Mallefet, Nicolas Oury, Hélène MagalonAbstract:Multiple paternity seems common within elasmobranchs. Focusing on two deep-sea shark species, the velvet belly lanternshark (Etmopterus spinax) and the slendertail lanternshark (Etmopterus molleri) we inferred the paternity in 31 E. spinax litters from Norway (three to 18 embryos per litter) and six E. molleri litters from Japan (three to six embryos), using 21 and 10 specific microsatellites, respectively. At least two E. spinax litters were sired from multiple fathers each, with highly variable paternal skew (1:1 to 9:1). Conversely, no clear signal of genetic polyandry was found in E. molleri.
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Etmopterus spinax the velvet belly lanternshark does not use bacterial luminescence
Acta Histochemica, 2019Co-Authors: Laurent Duchatelet, Jérôme Delroisse, Patrick Flammang, Jacques Mahillon, Jérôme MallefetAbstract:Abstract Marine organisms are able to produce light using either their own luminous system, called intrinsic bioluminescence, or symbiotic luminous bacteria, called extrinsic bioluminescence. Among bioluminescent vertebrates, Osteichthyes are known to harbor both types of bioluminescence, while no study has so far addressed the potential use of intrinsic/extrinsic luminescence in elasmobranchs. In sharks, two families are known to emit light: Etmopteridae and Dalatiidae. The deep-sea bioluminescent Etmopteridae, Etmopterus spinax, has received a particular interest over the past fifteen years and its bioluminescence control was investigated in depth. However, the nature of the shark luminous system still remains enigmatic. The present work was undertaken to assess whether the light of this shark species originates from a bioluminescent bacterial symbiosis. Using fluorescent in situ hybridization (FISH) and transmission electron microscopy (TEM) image analyses, this study supports the conclusion that the bioluminescence in the deep-sea lanternshark, Etmopterus spinax, is not of bacterial origin.
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Etmopteridae bioluminescence: dorsal pattern specificity and aposematic use
Zoological Letters, 2019Co-Authors: Laurent Duchatelet, Nicolas Pinte, Taketeru Tomita, Keiichi SatoAbstract:Background In the darkness of the ocean, an impressive number of taxa have evolved the capability to emit light. Many mesopelagic organisms emit a dim ventral glow that matches with the residual environmental light in order to camouflage themselves (counterillumination function). Sharks use their luminescence mainly for this purpose. Specific lateral marks have been observed in Etmopteridae sharks (one of the two known luminous shark families) suggesting an inter/intraspecific recognition. Conversely, dorsal luminescence patterns are rare within these deep-sea organisms. Results Here we report evidence that Etmopterus spinax, Etmopterus molleri and Etmopterus splendidus have dorsal luminescence patterns. These dorsal patterns consist of specific lines of luminous organs, called photophores, on the rostrum, dorsal area and at periphery of the spine. This dorsal light seems to be in contrast with the counterilluminating role of ventral photophores. However, skin photophores surrounding the defensive dorsal spines show a precise pattern supporting an aposematism function for this bioluminescence. Using in situ imaging, morphological and histological analysis, we reconstructed the dorsal light emission pattern on these species, with an emphasis on the photogenic skin associated with the spine. Analyses of video footage validated, for the first time, the defensive function of the dorsal spines. Finally, we did not find evidence that Etmopteridae possess venomous spine-associated glands, present in Squalidae and Heterondontidae, via MRI and CT scans. Conclusion This work highlights for the first time a species-specific luminous dorsal pattern in three deep-sea lanternsharks. We suggest an aposematic use of luminescence to reveal the presence of the dorsal spines. Despite the absence of venom apparatus, the defensive use of spines is documented for the first time in situ by video recordings.
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isolation and characterization of 29 and 19 microsatellite loci from two deep sea luminous lanternsharks Etmopterus spinax and Etmopterus molleri squaliformes etmopteridae
Molecular Biology Reports, 2019Co-Authors: Nicolas Oury, Jérôme Mallefet, Laurent Duchatelet, Hélène MagalonAbstract:Etmopterus spinax (Linnaeus, 1758) and Etmopterus molleri (Whitley, 1939) are two bioluminescent deep-sea sharks, usually caught in large numbers as bycatch by deep-water fisheries. Yet, no study has ever involved population status of these two species using genetic tools. In order to investigate population genetic structure, diversity and connectivity of these two lanternsharks, 29 and 19 microsatellite loci were isolated from E. spinax DNA library for E. spinax and E. molleri, respectively. These loci were tested on 32 E. spinax individuals from the North Sea and seven E. molleri from the East China Sea. The number of alleles per locus ranged from 2 to 13. The observed heterozygosity ranged from 0.031 to 0.839 for E. spinax and from 0.000 to 1.000 for E. molleri, while the expected heterozygosity ranged from 0.031 to 0.903 and from 0.143 to 0.821, respectively. Almost all loci (24 and 16, respectively) were at Hardy–Weinberg equilibrium for both species and no linkage disequilibrium among loci was detected. These loci represent useful tools to better understand the population structure of these two species. Besides, they could also be suitable for other lanternsharks in general, as these latter remain largely understudied, specially in terms of understanding the basic science that will serve into their conservation.
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Additional file 1: of Etmopteridae bioluminescence: dorsal pattern specificity and aposematic use
2019Co-Authors: Laurent Duchatelet, Nicolas Pinte, Taketeru Tomita, Keiichi Sato, Jérôme MallefetAbstract:Animated GIF of MRI transversal section of Etmopterus spinax at the level of spine base, going from the tip to the base of the spine. (GIF 557 kb