Stack of cellular lamellae forms a silvered cortex to conceal the opaque organ in a transparent gastropod in epipelagic habitat
Background Gelatinous zooplankton in epipelagic environments often have highly transparent bodies to avoid detection by their visual predators and prey; however, the digestive systems are often exceptionally opaque even in these organisms. In a holoplanktonic gastropod, Pterotrachea coronata, the vi...
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| Format: | Article |
| Language: | English |
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PeerJ Inc.
2022-10-01
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| Online Access: | https://peerj.com/articles/14284.pdf |
| _version_ | 1797418426802634752 |
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| author | Daisuke Sakai Jun Nishikawa Hiroshi Kakiuchida Euichi Hirose |
| author_facet | Daisuke Sakai Jun Nishikawa Hiroshi Kakiuchida Euichi Hirose |
| author_sort | Daisuke Sakai |
| collection | DOAJ |
| description | Background Gelatinous zooplankton in epipelagic environments often have highly transparent bodies to avoid detection by their visual predators and prey; however, the digestive systems are often exceptionally opaque even in these organisms. In a holoplanktonic gastropod, Pterotrachea coronata, the visceral nucleus is an opaque organ located at the posterior end of its alimentary system, but this organ has a mirrored surface to conceal its internal opaque tissue. Results Our ultrastructural observation proved that the cortex of the visceral nucleus comprised a stack of thin cellular lamellae forming a Bragg reflector, and the thickness of lamellae (0.16 µm in average) and the spaces between the lamellae (0.1 µm in average) tended to become thinner toward inner lamellae. Based on the measured values, we built virtual models of the multilamellar layer comprising 50 lamellae and spaces, and the light reflection on the models was calculated using rigorous coupled wave analysis to evaluate their properties as reflectors. Our simulation supported the idea that the layer is a reflective tissue, and the thickness of the lamella/space must be chirped to reflect sunlight as white/silver light, mostly independent of the angle of incidence. Conclusions In P. coronata, the cortex of the visceral nucleus comprised multicellular lamellae that form a chirped Bragg reflector. It is distinct in structure from the intracellular Bragg structures of common iridophores. This novel Bragg reflector demonstrates the diversity and convergent evolution of reflective tissue using reflectin-like proteins in Mollusca. |
| first_indexed | 2024-03-09T06:32:31Z |
| format | Article |
| id | doaj.art-e910beb9c0d04810bc9799d768394c15 |
| institution | Directory Open Access Journal |
| issn | 2167-8359 |
| language | English |
| last_indexed | 2024-03-09T06:32:31Z |
| publishDate | 2022-10-01 |
| publisher | PeerJ Inc. |
| record_format | Article |
| series | PeerJ |
| spelling | doaj.art-e910beb9c0d04810bc9799d768394c152023-12-03T11:03:25ZengPeerJ Inc.PeerJ2167-83592022-10-0110e1428410.7717/peerj.14284Stack of cellular lamellae forms a silvered cortex to conceal the opaque organ in a transparent gastropod in epipelagic habitatDaisuke Sakai0Jun Nishikawa1Hiroshi Kakiuchida2Euichi Hirose3School of Regional Innovation and Social Design Engineering, Kitami Institute of Technology, Kitami, Hokkaido, JapanDepartment of Marine Biology, School of Marine Science and Technology, Tokai University, Shimizu, Shizuoka, JapanInnovative Functional Materials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya, Aichi, JapanFaculty of Science, University of the Ryukyus, Nishihara, Okinawa, JapanBackground Gelatinous zooplankton in epipelagic environments often have highly transparent bodies to avoid detection by their visual predators and prey; however, the digestive systems are often exceptionally opaque even in these organisms. In a holoplanktonic gastropod, Pterotrachea coronata, the visceral nucleus is an opaque organ located at the posterior end of its alimentary system, but this organ has a mirrored surface to conceal its internal opaque tissue. Results Our ultrastructural observation proved that the cortex of the visceral nucleus comprised a stack of thin cellular lamellae forming a Bragg reflector, and the thickness of lamellae (0.16 µm in average) and the spaces between the lamellae (0.1 µm in average) tended to become thinner toward inner lamellae. Based on the measured values, we built virtual models of the multilamellar layer comprising 50 lamellae and spaces, and the light reflection on the models was calculated using rigorous coupled wave analysis to evaluate their properties as reflectors. Our simulation supported the idea that the layer is a reflective tissue, and the thickness of the lamella/space must be chirped to reflect sunlight as white/silver light, mostly independent of the angle of incidence. Conclusions In P. coronata, the cortex of the visceral nucleus comprised multicellular lamellae that form a chirped Bragg reflector. It is distinct in structure from the intracellular Bragg structures of common iridophores. This novel Bragg reflector demonstrates the diversity and convergent evolution of reflective tissue using reflectin-like proteins in Mollusca.https://peerj.com/articles/14284.pdfBragg reflectorGelatinous zooplanktonPterotracheid gastropodRigorous coupled wave analysis (RCWA)Ultrastructure |
| spellingShingle | Daisuke Sakai Jun Nishikawa Hiroshi Kakiuchida Euichi Hirose Stack of cellular lamellae forms a silvered cortex to conceal the opaque organ in a transparent gastropod in epipelagic habitat PeerJ Bragg reflector Gelatinous zooplankton Pterotracheid gastropod Rigorous coupled wave analysis (RCWA) Ultrastructure |
| title | Stack of cellular lamellae forms a silvered cortex to conceal the opaque organ in a transparent gastropod in epipelagic habitat |
| title_full | Stack of cellular lamellae forms a silvered cortex to conceal the opaque organ in a transparent gastropod in epipelagic habitat |
| title_fullStr | Stack of cellular lamellae forms a silvered cortex to conceal the opaque organ in a transparent gastropod in epipelagic habitat |
| title_full_unstemmed | Stack of cellular lamellae forms a silvered cortex to conceal the opaque organ in a transparent gastropod in epipelagic habitat |
| title_short | Stack of cellular lamellae forms a silvered cortex to conceal the opaque organ in a transparent gastropod in epipelagic habitat |
| title_sort | stack of cellular lamellae forms a silvered cortex to conceal the opaque organ in a transparent gastropod in epipelagic habitat |
| topic | Bragg reflector Gelatinous zooplankton Pterotracheid gastropod Rigorous coupled wave analysis (RCWA) Ultrastructure |
| url | https://peerj.com/articles/14284.pdf |
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