Search Results (9)

This work provides a contribution to the understanding of the structure of the photophores in the mesopelagic fish Chauliodus sloani (family Stomiidae), which occasionally are stranded along the coasts of the Strait of Messina (Central Mediterranean Sea). The analysis was carried out through the study of the structure and ultrastructure of the ventral photophores, and it also includes an immunohistochemical investigation that offers valuable insights into the function of these organs. Studies on photophores help clarify many aspects of the ecology of this species, which represents an important functional link in the marine food web. Full article

The constellation fish, Valenciennellus tripunctulatus, is a small mesopelagic teleost typically found in equatorial and temperate waters worldwide, although the species has been also rarely recorded in the Mediterranean Sea (less than 20 specimens from the available literature since 1918). The Mediterranean records have been documented for the Strait of Messina, the southern Tyrrhenian Sea, the Ligurian Sea and the Adriatic Sea. The present paper offers an updated review on the occurrence of V. tripunctulatus in the Mediterranean basin and provides data on three new specimens, collected in the Strait of Messina between April 2010 and March 2024. Furthermore, we also report information from two individuals found in March 1992 and February 2017, respectively. Overall, the standard length of these specimens ranged from 24.1 to 28.2 mm, whereas weight varied from 0.18 g to 0.20 g. Morphometric and meristic data were reported, and this analysis revealed few differences between examined individuals in the number of PV (ventral series anterior to pelvic fin base) and AC (from anal fin origin to caudal fin base) photophore series. The relationship between total length and standard length (SL = 0.75 × TL + 2.98), total length and head length (HL = 0.17 × TL + 1.47) and standard length and head length (HL = 0.23 × SL + 0.88) showed high correlation values. Considering the lack of data on this species in the Mediterranean, updating morphometric, meristic, biological, ecological and distribution information is very important for taxonomic purposes and useful in understanding the characteristics of the regional population and eventual differences between Mediterranean stock(s) and those from other oceanic areas. Full article

Bioluminescence is the production of visible light by an organism. This phenomenon is particularly widespread in marine animals, especially in the deep sea. While the luminescent status of numerous marine animals has been recently clarified thanks to advancements in deep-sea exploration technologies and phylogenetics, that of others has become more obscure due to dramatic changes in systematics (themselves triggered by molecular phylogenies). Here, we combined a comprehensive literature review with unpublished data to establish a catalogue of marine luminescent animals. Inventoried animals were identified to species level in over 97% of the cases and were associated with a score reflecting the robustness of their luminescence record. While luminescence capability has been established in 695 genera of marine animals, luminescence reports from 99 additional genera need further confirmation. Altogether, these luminescent and potentially luminescent genera encompass 9405 species, of which 2781 are luminescent, 136 are potentially luminescent (e.g., suggested luminescence in those species needs further confirmation), 99 are non-luminescent, and 6389 have an unknown luminescent status. Comparative analyses reveal new insights into the occurrence of luminescence among marine animal groups and highlight promising research areas. This work will provide a solid foundation for future studies related to the field of marine bioluminescence. Full article

Bioluminescence is a common ecological trait among many marine organisms, including three shark families: Etmopteridae, Dalatiidae, and Somniosidae. The kitefin shark, Dalatias licha (Bonnaterre, 1788), from the Dalatiidae family is the largest known luminous vertebrate. This study compares the light organ ultrastructure of D. licha with that of Etmopterus spinax, the type species of Etmopteridae, to gain a deeper understanding of the light emission process and its evolutionary conservation within shark families. The ultrastructure of D. licha’s photophores and the morphological changes that occur after hormonal stimulation (via melatonin and α-MSH, which stimulate or inhibit the bioluminescence, respectively) were examined. The photophores consist of a spherical pigmented sheath surrounding a unique, regionalized light-emitting cell (photocyte). The photocyte’s basal area contains a specific area filled with granular inclusions that resemble the glowon-type microsources of E. spinax, suggesting that this area is the intracellular site of light emission. An acidophilic secretion, not present in Etmopteridae, is also observed within the granular area and may be involved in photogenesis. The ultrastructure analysis reveals no lens cells or reticular layer, unlike in Etmopteridae photophores, indicating a simpler organization in Dalatiidae photophores. Melatonin stimulation causes the removal of pigments from the photophore-associated melanophores and an increase in the granular inclusion diameter and coverage in the granular area, further showing that this last area is the potential site of light emission, while α-MSH stimulation causes the extension of the melanophore pigments and a decrease in the granular inclusion diameter and coverage. These results support the evolutive conservation of photophore functional organization across luminous etmopterid and dalatiid sharks. Full article

Bioluminescence is a common phenomenon in marine organisms, especially in deep water where faint blue light remains. Among elasmobranchs, three families display the ability to emit light, the Etmopteridae, the Dalatiidae, and the Somniosidae. Luminous sharks have thousands of minute light organs, called photophores, that are mainly present ventrally and produce light. The main function of shark luminescence is counterillumination to camouflage the shark silhouette by mimicking the residual ambient light and avoiding being spotted by predators underneath. To perform counterillumination efficiently, luminescence needs to be finely adjusted. A new type of control was recently demonstrated via extraocular photoreception at the level of the light organ. An encephalopsin (i.e., opsin 3) was shown to be expressed in the vicinity of the photophore of an Etmopteridae species, Etmopterus spinax. This opsin was also demonstrated to be expressed concomitantly with the photophore development (i.e., when photophores become able to produce light) during E. spinax embryogenesis. To understand the photophore morphogenesis of different shark families, we analyzed the smalleye pygmy shark, Squaliolus aliae, with a photophore formation which represents the first report on the Dalatiidae family. Since Dalatiidae and Etmopteridae are phylogenetically closely related, the photophore morphogenesis was compared with an Etmopteridae representative, Etmopterus spinax. The results also reveal that Squaliolus aliae shares similar encephalopsin expression pattern as in Etmopterus spinax, which further supports evolutionary conservation of photophore morphogenesis as well as its own encephalopsin-based light perception across the two luminous shark families. Full article

This review presents a synthesis of shark bioluminescence knowledge. Up to date, bioluminescent sharks are found only in Squaliformes, and specifically in Etmopteridae, Dalatiidae and Somniosidae families. The state-of-the-art knowledge about the evolution, ecological functions, histological structure, the associated squamation and physiological control of the photogenic organs of these elusive deep-sea sharks is presented. Special focus is given to their unique and singular hormonal luminescence control mechanism. In this context, the implication of the photophore-associated extraocular photoreception—which complements the visual adaptations of bioluminescent sharks to perceive residual downwelling light and luminescence in dim light environment—in the hormonally based luminescence control is depicted in detail. Similarities and differences between shark families are highlighted and support the hypothesis of an evolutionary unique ancestral appearance of luminescence in elasmobranchs. Finally, potential areas for future research on shark luminescence are presented. Full article

Lactisole, which has a 2-phenoxy propionic acid skeleton, is well-known as an inhibitor of sweet taste receptors. We recently revealed some of the structure–activity relationships of the aromatic ring and chiral center of lactisole. Photoaffinity labeling is one of the common chemical biology methods to elucidate the interaction between bioactive compounds and biomolecules. In this paper, the novel asymmetric synthesis of lactisole derivatives with common photophores (benzophenone, azide and trifluoromethyldiazirine) for photoaffinity labeling is described. The synthetic compounds are subjected to cell-based sweet taste receptors, and the substitution with trifluoromethyldiazirinyl photophore shows the highest affinity to the receptor of the synthesized compounds. Full article

Aliphatic diazirines have been widely used as prominent photophores for photoaffinity labeling owing to their relatively small size which can reduce the steric effect on the natural interaction between ligands and proteins. Based on our continuous efforts to develop efficient methods for the synthesis of aliphatic diazirines, we present here a comprehensive study about base-mediated one-pot synthesis of aliphatic diazirines. It was found that potassium hydroxide (KOH) can also promote the construction of aliphatic diazirine with good efficiency. Importantly, KOH is cheaper, highly available, and easily handled and stored compared with the previously used base, potassium tert-butoxide (t-BuOK). Gram-scale study showed that it owned great advantages in being used for the large-scale production of aliphatic diazirines. This protocol is highly neat and the desired products can be easily isolated and purified. As the first comprehensive study of the base-mediated one-pot synthesis of aliphatic diazirines, this work provided good insight into the preparation and utilization of diazirine-based photoaffinity labeling probes. Full article

Photoaffinity labeling is a reliable analytical method for biological functional analysis. Three major photophores—aryl azide, benzophenone and trifluoromethyldiazirine—are utilized in analysis. Photophore-bearing l-phenylalanine derivatives, which are used for biological functional analysis, were inoculated into a Klebsiella sp. isolated from the rhizosphere of a wild dipterocarp sapling in Central Kalimantan, Indonesia, under nitrogen-limiting conditions. The proportions of metabolites were quite distinct for each photophore. These results indicated that photophores affected substrate recognition in rhizobacterial metabolic pathways, and differential photoaffinity labeling could be achieved using different photophore-containing l-phenylalanine derivatives. Full article