I am a biologist primarily working on the deep sea and molluscs (incl. snails, clams, octopuses, chitons, etc.). A focus of my research is to document and understand biodiversity and its evolution across multiple levels: from species to ecosystem, and from phenome to genome. Over geological timescales, life has evolved countless ‘novelties’ in order to gain new functions and conquer new environments. Like how wings allowed access to the sky, living in ‘extreme’ habitats such as deep-sea hot vents require novel adaptations. I am interested in 1) the diversity of organisms and their novelties, 2) how they help the organism adapt to the environment, and 3) by what trajectories do these novelties arise (and if there are common laws governing them).
I am currently a Senior Scientist with Tenureat the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), the Japanese national research institute for marine sciences. I am also a visiting scientist of Senckenberg Research Institute and Natural History Museum, Frankfurt, and a member of the IUCN Species Survival Commission, Mollusc Specialist Group. I have dived up to >6,000 m deep in the manned submersibles DSV SHINKAI 6500 and TRITON 3300/3 Mk. II in person to explore hot vents and other deep-sea environments, although I also often work with remotely operated submersibles. I am an avid collector of molluscs (‘shell collector’) and photographer.
![We collaborated with Sony to develop a new method to evaluate organismal behaviour and particle dynamics using the Event‐based Vision Sensor (EVS)! By focusing on brightness shifts, EVS is a new type of camera sensor that can reach 10,000 fps even under low-light. Read this OPEN ACCESS paper for free: https://doi.org/10.1002/ece3.70150<br />
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Abstract:<br />
The Event-based Vision Sensor (EVS) is a bio-inspired sensor that captures detailed motions of objects, aiming to become the ‘eyes’ of machines like self-driving cars. Compared to conventional frame-based image sensors, the EVS has an extremely fast motion capture equivalent to 10,000-fps even with standard optical settings, plus high dynamic ranges for brightness and also lower consumption of memory and energy. Here, we developed 22 characteristic features for analysing the motions of aquatic particles from the EVS raw data and tested the applicability of the EVS in analysing plankton behaviour. Laboratory cultures of six species of zooplankton and phytoplankton were observed, confirming species-specific motion periodicities up to 41 Hz. We applied machine learning to automatically classify particles into four categories of zooplankton and passive particles, achieving an accuracy up to 86%. At the in situ deployment of the EVS at the bottom of Lake Biwa, several particles exhibiting distinct cumulative trajectory with periodicities in their motion (up to 16 Hz) were identified, suggesting that they were living organisms with rhythmic behaviour. We also used the EVS in the deep sea, observing particles with active motion and periodicities over 40 Hz. Our application of the EVS, especially focusing on its millisecond-scale temporal resolution and wide dynamic range, provides a new avenue to investigate organismal behaviour characterised by rapid and periodical motions. The EVS will likely be applicable in the near future for the automated monitoring of plankton behaviour by edge computing on autonomous floats, as well as quantifying rapid cellular-level activities under microscopy.<br />
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Takatsuka S# / Miyamoto N#, Sato H, Morino Y, Kurita Y, Yabuki A, Chen C, Kawagucci S* (2024). Milli-second-scale behaviours of plankton quantified in vitro and in situ using the Event-based Vision Sensor. Ecology and Evolution, 14: e70150. DOI: 10.1002/ece3.70150 [Preprint available on bioRxiv, DOI: 10.1101/2023.01.11.523686]](https://scontent-den2-1.xx.fbcdn.net/v/t39.30808-6/457323359_10228766404479331_5592781285350155259_n.jpg?_nc_cat=108&ccb=1-7&_nc_sid=46905d&_nc_ohc=YxYg-IQQWTAQ7kNvgE0jUB1&_nc_zt=23&_nc_ht=scontent-den2-1.xx&edm=AC7C4-wEAAAA&_nc_gid=AI7PEdD8tgvwGPBJyIEGbrN&oh=00_AYAkW1lXdRT3TQQUZSuA1Bly4vdXDhjjrqipsEt8n2fZTw&oe=676BE99D)
![Conus nocturnus [Lightfoot], 1786 <br />
CONIDAE<br />
-20 m, Dived, Off Manado, North Sulawesi, Indonesia, 2023/vii, 60.5 mm <br />
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Characterised by a pattern with two very broad and dark bands separating zones of irregular white tent-like patterns, the "Nocturne Cone" is a conid endemic to Indonesia. Only known from the eastern part of the country approximately between Sulawesi Island and western New Guinea, it lives in shallow waters between about 1 to 30 m deep on coral sand and rubble. The type locality was originally stated as "China", which is now considered erroneous. This has caused the species to become 'lost' for about two centuries before it was finally rediscovered in Indonesia. Partly due to this convoluted history it was considered a classic rarity for decades, but recently there has been a surge in shell collecting activities in Indonesia leading to an increased availability, rendering it uncommon at most. A carnivorous gastropod, it is an active predator feeding on other molluscs. <br />
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The overall shell form and pattern varies only slightly, most notably in the size and extent of the white 'tents'. Vast majority of specimens exhibit very dark brown and close to solid black bands, but rarely shells with lighter brown bands are also found. Like many conid species, the shell surface can be either smooth or strongly granulose; the latter form has been named f. deburghiae Sowerby II, 1857. Some specimens have been found to transition from smooth to granulate or vice versa through growth. Typical shell length around 60 mm, very large specimens can exceed 85 mm. <br />
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It is most similar to Conus bandanus Hwass, 1792, which can be distinguished by a more conical body whorl with straight sides, more of the shell surface being covered by white tent-like pattern, and growing to a larger size (reaching 150 mm). Though C. bandanus is very variable and some forms such as C. bandanus f. equestris Röding, 1798 are smaller with less tenting, the conical shell form with straight sides can always differentiate it from C. nocturnus.](https://scontent-den2-1.xx.fbcdn.net/v/t39.30808-6/450192462_10228282097731965_4768990594989564157_n.jpg?_nc_cat=110&ccb=1-7&_nc_sid=46905d&_nc_ohc=JrZKZdEnbGsQ7kNvgHeEeiu&_nc_zt=23&_nc_ht=scontent-den2-1.xx&edm=AC7C4-wEAAAA&_nc_gid=AJ2spRjJggaLSPy-WXmXgYA&oh=00_AYAgK9DXfhXSevGyn0IrHPKtgYqrBJH8dNTtop4gsfp5Eg&oe=676C122F)
![Cymbiola imperialis ([Lightfoot], 1786)<br />
VOLUTIDAE<br />
-65 m, By net, Bongao, Tawi-Tawi, Mindanao, Philippines, 2020, 238.0 mm <br />
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The aptly named "Imperial Volute" is a large volutid native to Sulu Sea between the Philippines and Malaysia, characterised by a crown of long spines around the shoulder. A carnivorous and predatory gastropod inhabiting sandy bottoms and feeding on other invertebrate animals, it is found from very shallow waters just below lowtide zone to about 80 m depth. A common species, its showy shell is often sold as souvenir or room decoration, almost all originating from the Philippines. <br />
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Typical specimens exhibit a shell pattern combining lightning-like axial streaks and 3-4 broad spiral bands of irregular dark brown blotches, but some specimens lack the spiral bands entirely -- a form known as f. robinsona (Burch, 1954). The shoulder spines vary in strength and number among individuals, shells without spines have also been found but such specimens are extremely rare. The aperture colouration can also vary from pale yellow to very dark orange. The shell is covered by a layer of thin, brownish periostracum when alive; the periostracum is often glazed over on the ventral side by another layer of transparent calcium carbonate (callus). Typical shell length around 200 mm, very large specimens can exceed even 270 mm. <br />
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Though the overall morphology of C. imperialis resemebles C. chrysostoma (Swainson, 1824), that species is much smaller and typically does not exceed 80 mm in shell length. Cymbiola nobilis ([Lightfoot], 1786) is another broadly similar species, but is easily distinguished by the shell being broader and lacking shoulder spines entirely.](https://scontent-den2-1.xx.fbcdn.net/v/t39.30808-6/420166125_10227401308832793_5954611142799536285_n.jpg?_nc_cat=107&ccb=1-7&_nc_sid=46905d&_nc_ohc=cFlLOEKJ2a0Q7kNvgEFbuxz&_nc_zt=23&_nc_ht=scontent-den2-1.xx&edm=AC7C4-wEAAAA&_nc_gid=AJ2spRjJggaLSPy-WXmXgYA&oh=00_AYBMhNvgmI5E9uOTBUXIFAoeEemeQov7fhgIIJv5xMI8LQ&oe=676C0B32)
Chrysomallon squamiferum Chen et al., 2015
