Fine structure of the luminous spines and luciferase detection in the brittle star Amphiura filiformis (original) (raw)
Related papers
A brittle star is born: Ontogeny of luminous capabilities in Amphiura filiformis
PloS one, 2024
Bioluminescence is the production of visible light by living organisms thanks to a chemical reaction, implying the oxidation of a substrate called luciferin catalyzed by an enzyme, the luciferase. The luminous brittle star Amphiura filiformis depends on coelenterazine (i.e., the most widespread luciferin in marine ecosystems) and a luciferase homologous to the cnidarian Renilla luciferase to produce blue flashes in the arm's spine. Only a few studies have focused on the ontogenic apparitions of bioluminescence in marine organisms. Like most ophiuroids, A. filiformis displays planktonic ophiopluteus larvae for which the ability to produce light was not investigated. This study aims to document the apparition of the luminous capabilities of this species during its ontogenic development, from the egg to settlement. Through biochemical assays, pharmacological stimulation, and Renilla-like luciferase immunohistological detection across different developing stages, we pointed out the emergence of the luminous capabilities after the ophiopluteus larval metamorphosis into a juvenile. In conclusion, we demonstrated that the larval pelagic stage of A.
Journal of cell science, 1987
In order to discover the intracellular location of luciferase in dinoflagellates, sections from a number of species were treated with a polyclonal anti-luciferase and the bound antibody was visualized at the electron-microscope level by indirect immunogold labelling. In two species of Pyrocystis and in Noctiluca, as in Gonyaulax, antibody became bound to dense vesicles, which correspond in size and position to light-emitting bodies detected in previous work. These vesicles resemble microsomes, are bounded by a single membrane and sometimes project into the vacuole. Unexpectedly, the trichocysts of Gonyaulax and Noctiluca and the related mucocysts of Pyrocystis also bound the antibody. This cross-reaction seems quite independent of bioluminescence, since the trichocysts of the non-luminous Cachonina also reacted positively. The possibility is discussed that a protein, different from luciferase but having some antigenic similarity, is present in trichocysts and related organelles.
A puzzling homology: a brittle star using a putative cnidarian-type luciferase for bioluminescence
Open Biology, 2017
Bioluminescence relies on the oxidation of a luciferin substrate catalysed by a luciferase enzyme. Luciferins and luciferases are generic terms used to describe a large variety of substrates and enzymes. Whereas luciferins can be shared by phylogenetically distant organisms which feed on organisms producing them, luciferases have been thought to be lineage-specific enzymes. Numerous light emission systems would then have co-emerged independently along the tree of life resulting in a plethora of non-homologous luciferases. Here, we identify for the first time a candidate luciferase of a luminous echinoderm, the ophiuroidAmphiura filiformis. Phylogenomic analyses identified the brittle star predicted luciferase as homologous to the luciferase of the sea pansyRenilla(Cnidaria), contradicting with the traditional viewpoint according to which luciferases would generally be of convergent origins. The similarity between theRenillaandAmphiuraluciferases allowed us to detect the latter using...
Zoomorphology, 1987
Three structures in the dermis of the dorsal arm plate (DAP) of the brittlestar, Ophiocoma wendti, appear to comprise a photoreceptor system. The upper surface of the DAP bears transparent, knob-like, microscopic structures which are expanded peripheral trabeculae (EPT) of the calcite stereom. The EPT are part of the photoreceptor system and can facilitate light transmission through the DAP by decreasing light refraction, reflection and absorption that occur at stereom/stroma interfaces. Bundles of nerve fibres located below the EPT area second component of the system, and may function as primary photoreceptors. The intensity of light impinging on the putative sensory tissue is regulated by the diurnal activity cycle of chromatophores, the third element of the system. During the day the chromatophores cover the EPT and thereby shade the nerve fibres. At night they retract into inter-trabecular channels, uncovering the EPT and thereby exposing the nerve fibres to transmitted light. Thus, the transparent stereom may play a role in photoreception, in addition to its generally recognized skeletal function. Although ciliated cells that may be sensory are present in the epidermis of Ophiocoma wendti, they do not appear to be photoreceptors. Functional analogues of the brittlestar photoreceptor system in other echinoderms are discussed, emphasizing the relationship between photosensitivity and the transparency of the stereom in several classes of Echinodermata.
De Novo Adult Transcriptomes of Two European Brittle Stars: Spotlight on Opsin-Based Photoreception
PLOS ONE, 2016
Next generation sequencing (NGS) technology allows to obtain a deeper and more complete view of transcriptomes. For non-model or emerging model marine organisms, NGS technologies offer a great opportunity for rapid access to genetic information. In this study, paired-end Illumina HiSeqTM technology has been employed to analyse transcriptomes from the arm tissues of two European brittle star species, Amphiura filiformis and Ophiopsila aranea. About 48 million Illumina reads were generated and 136,387 total unigenes were predicted from A. filiformis arm tissues. For O. aranea arm tissues, about 47 million reads were generated and 123,324 total unigenes were obtained. Twenty-four percent of the total unigenes from A. filiformis show significant matches with sequences present in reference online databases, whereas, for O. aranea, this percentage amounts to 23%. In both species, around 50% of the predicted annotated unigenes were significantly similar to transcripts from the purple sea urchin, the closest species to date that has undergone complete genome sequencing and annotation. GO, COG and KEGG analyses were performed on predicted brittle star unigenes. We focused our analyses on the phototransduction actors involved in light perception. Firstly, two new echinoderm opsins were identified in O. aranea: one rhabdomeric opsin (homologous to vertebrate melanopsin) and one RGR opsin. The RGR-opsin is supposed to be involved in retinal regeneration while the r-opsin is suspected to play a role in visual-like behaviour. Secondly, potential phototransduction actors were identified in both transcriptomes using the fly (rhabdomeric) and mammal (ciliary) classical phototransduction pathways as references. Finally, the sensitivity of O.aranea to monochromatic light was investigated to complement data available for A. filiformis. The presence of microlens-like structures at the surface of dorsal arm plate of O. aranea could potentially explain phototactic behaviour differences between the two species. The results confirm (i) the ability of these brittle stars to perceive light using opsin-based photoreception, (ii) suggest the co-occurrence of both rhabdomeric and ciliary photoreceptors, and (iii) emphasise the complexity of light perception in this echinoderm class.
High opsin diversity in a non-visual infaunal brittle star
BMC Genomics, 2014
Background: In metazoans, opsins are photosensitive proteins involved in both vision and non-visual photoreception. Echinoderms have no well-defined eyes but several opsin genes were found in the purple sea urchin (Strongylocentrotus purpuratus) genome. Molecular data are lacking for other echinoderm classes although many species are known to be light sensitive. Results: In this study focused on the European brittle star Amphiura filiformis, we first highlighted a blue-green light sensitivity using a behavioural approach. We then identified 13 new putative opsin genes against eight bona fide opsin genes in the genome of S. purpuratus. Six opsins were included in the rhabdomeric opsin group (r-opsins). In addition, one putative ciliary opsin (c-opsin), showing high similarity with the c-opsin of S. purpuratus (Sp-opsin 1), one Go opsin similar to Sp-opsins 3.1 and 3.2, two basal-branch opsins similar to Sp-opsins 2 and 5, and two neuropsins similar to Sp-opsin 8, were identified. Finally, two sequences from one putative RGR opsin similar to Sp-opsin 7 were also detected. Adult arm transcriptome analysis pinpointed opsin mRNAs corresponding to one r-opsin, one neuropsin and the homologue of Sp-opsin 2. Opsin phylogeny was determined by maximum likelihood and Bayesian analyses. Using antibodies designed against c-and r-opsins from S. purpuratus, we detected putative photoreceptor cells mainly in spines and tube feet of A. filiformis, respectively. The r-opsin expression pattern is similar to the one reported in S. purpuratus with cells labelled at the tip and at the base of the tube feet. In addition, r-opsin positive cells were also identified in the radial nerve of the arm. C-opsins positive cells, expressed in pedicellariae, spines, tube feet and epidermis in S. purpuratus were observed at the level of the spine stroma in the brittle star.
Visual Neuroscience, 1993
Isolated photoreceptors are desirable for whole-cell and patch-clamp studies of functional properties of visual processes that cannot be clearly analyzed when the photoreceptors are coupled. The retina of the compound lateral eye of the horseshoe crab, Limulus polyphemus, was dissociated into individual retinular cells using an enzyme pretreatment consisting of collagenase, papain, and trypsin, and a two-stage mechanical dissociation. These photoreceptors are functionally viable in an organ culture medium for up to 1 week and possess naked arhabdomeral and rhabdomeral segment membranes which are easily accessible for whole-cell recordings. A dissection technique was also developed whereby the retinal epidermis and neural plexus, as well as the second-order eccentric cells, could be separated from the ommatidia of the compound lateral eye in one simple step, providing viable isolated ommatidia attached to the cornea. The enzyme pretreatment used for dissociating the retina was then used to remove the individual ommatidia from the corneal cones. Hoffman modulation contrast microscopy was used to develop a reliable method for sorting and collecting viable isolated retinular cells for morphological and electrophysiological studies. Morphological analysis using light microscopy and scanning and transmission electron microscopy revealed that isolated retinular cells are morphologically nearly identical to retinular cells in situ. Isolated retinular cells possess a normal rhabdomere with no apparent loss of microvillar membrane as a result of the isolation process. Ommatidia can presently be isolated with up to six retinular cells possessing essentially normal structure and ultrastructure including thick rays of rhabdom. Isolated ommatidia possess naked A-segment membranes which are also well suited for whole-cell recording techniques.
Bioluminescence induction in the ophiuroid Amphiura filiformis (Echinodermata)
The Journal of Experimental Biology
Bioluminescence is a widespread phenomenon in the marine environment. Among luminous substrates, coelenterazine is the most widespread luciferin, found in more than nine phyla. The wide phylogenetic coverage of this light-emitting molecule has led to the hypothesis of its dietary acquisition that was demonstrated in one cnidarian and one lophogastrid shrimp species so far. Within Ophiuroidea, the dominant class of luminous echinoderms, Amphiura filiformis is a model species known to use coelenterazine as substrate of a luciferin / luciferase luminous system. The aim of this study was to perform a long-term monitoring of A. filiformis luminescent capabilities during captivity. Our results show (i) depletion of luminescent capabilities within five months when the ophiuroid is fed with a coelenterazine-free diet and (ii) a quick recovery of luminescent capabilities when the ophiuroid is fed with coelenterazine-supplemented food. The present work demonstrates for the first time a trophi...