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The circadian clock controls behavior and metabolism in various organisms. However, the exact timing and strength of rhythmic phenotypes can vary significantly between individuals of the same species. This is highly relevant for rhythmically complex marine environments where organismal rhythmic diversity likely permits the occupation of different microenvironments. When investigating circadian locomotor behavior of Platynereis dumerilii, a model system for marine molecular chronobiology, we found strain-specific, high variability between individual worms. The individual patterns were maintained for several weeks. A diel head transcriptome comparison of behaviorally rhythmic versus arrhythmic wild-type worms showed that 24-h cycling of core circadian clock transcripts is identical between both behavioral phenotypes. While behaviorally arrhythmic worms showed a similar total number of cycling transcripts compared to their behaviorally rhythmic counterparts, the annotation categories of their transcripts, however, differed substantially. Consistent with their locomotor phenotype, behaviorally rhythmic worms exhibit an enrichment of cycling transcripts related to neuronal/behavioral processes. In contrast, behaviorally arrhythmic worms showed significantly increased diel cycling for metabolism- and physiology-related transcripts. The prominent role of the neuropeptide pigment-dispersing factor (PDF) in Drosophila circadian behavior prompted us to test for a possible functional involvement of Platynereis pdf. Differing from its role in Drosophila, loss of pdf impacts overall activity levels but shows only indirect effects on rhythmicity. Our results show that individuals arrhythmic in a given process can show increased rhythmicity in others. Across the Platynereis population, rhythmic phenotypes exist as a continuum, with no distinct “boundaries” between rhythmicity and arrhythmicity. We suggest that such diel rhythm breadth is an important biodiversity resource enabling

The regular movements of waves and tides are obvious representations of the oceans’ rhythmicity. But the rhythms of marine life span across ecological niches and timescales, including short (in the range of hours) and long (in the range of days and months) periods. These rhythms regulate the physiology and behavior of individuals, as well as their interactions with each other and with the environment. This review highlights examples of rhythmicity in marine animals and algae that represent important groups of marine life across different habitats. The examples cover ecologically highly relevant species and a growing number of laboratory model systems that are used to disentangle key mechanistic principles. The review introduces fundamental concepts of chronobiology, such as the distinction between rhythmic and endogenous oscillator–driven processes. It also addresses the relevance of studying diverse rhythms and oscillators, as well as their interconnection, for making better predictions of how species will respond to environmental perturbations, including climate change. As the review aims to address scientists from the diverse fields of marine biology, ecology, and molecular chronobiology, all of which have their own scientific terms, we provide definitions of key terms throughout the article.

The moon’s monthly cycle synchronizes reproduction in countless marine organisms. The mass-spawning bristle worm Platynereis dumerilii uses an endogenous monthly oscillator set by full moon to phase reproduction to specific days. But how do organisms recognize specific moon phases? We uncover that the light receptor L-Cryptochrome (L-Cry) discriminates between different moonlight durations, as well as between sun- and moonlight. A biochemical characterization of purified L-Cry protein, exposed to naturalistic sun- or moonlight, reveals the formation of distinct sun- and moonlight states characterized by different photoreduction- and recovery kinetics of L-Cry’s cofactor Flavin Adenine Dinucleotide. In Platynereis, L-Cry’s sun- versus moonlight states correlate with distinct subcellular localizations, indicating different signaling. In contrast, r-Opsin1, the most abundant ocular opsin, is not required for monthly oscillator entrainment. Our work reveals a photo-ecological concept for natural light interpretation involving a “valence interpreter” that provides entraining photoreceptor(s) with light source and moon phase information.

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Özpolat, B. D., Randel, N., Williams, E. A., Bezares-Calderón, L. A., Andreatta, G., Balavoine, G., Bertucci, P. Y., Ferrier, D. E. K., Gambi, M. C., Gazave, E., Handberg-Thorsager, M., Hardege, J., Hird, C., Hsieh, Y.-W., Hui, J., Mutemi, K. N., Schneider, S. Q., Simakov, O., Vergara, H. M., Jékely, G., Tessmar-Raible, K., Raible, F., Arendt, D. The Nereid on the rise: Platynereis as a model system. EvoDevo, 12(1), (2021): 10, https://doi.org/10.1186/s13227-021-00180-3., The Nereid Platynereis dumerilii (Audouin and Milne Edwards (Annales des Sciences Naturelles 1:195–269, 1833) is a marine annelid that belongs to the Nereididae, a family of errant polychaete worms. The Nereid shows a pelago-benthic life cycle: as a general characteristic for the superphylum of Lophotrochozoa/Spiralia, it has spirally cleaving embryos developing into swimming trochophore larvae. The larvae then metamorphose into benthic worms living in self-spun tubes on macroalgae. Platynereis is used as a model for genetics, regeneration, reproduction biology, development, evolution, chronobiology, neurobiology, ecology, ecotoxicology, and most recently also for connectomics and single-cell genomics. Research on the Nereid started with studies on eye development and spiralian embryogenesis in the nineteenth and early twentieth centuries. Transitioning into the molecular era, Platynereis research focused on posterior growth and regeneration, neuroendocrinology, circadian and lunar cycles, fertilization, and oocyte maturation. Other work covered segmentation, photoreceptors and other sensory cells, nephridia, and population dynamics. Most recently, the unique advantages of the Nereid young worm for whole-body volume electron microscopy and single-cell sequencing became apparent, enabling the tracing of all neurons in its rope-ladder-like central nervous system, and the construction of multimodal cellular atlases. Here, we provide an overview of current topics and methodologies for P. dumerilii, with the aim of stimulating further interest into our unique model and expanding the active and vibrant Platynereis community., Funding resources are shown after author initials. EAW: BBSRC David Phillips Fellowship BB/T00990X/1. BDÖ: NIH NIGMS MIRA 1R35GM138008-01; NSF-EDGE Award no 1923429; Hibbitt Startup Funds. GJ, LABC, CH: Wellcome Trust Investigator Award 214337/Z/18/Z. KNM: Marie Sklodowska-Curie fellow supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 766053, project EvoCELL. NR: European Union Horizon 2020, Marie Skłodowska-Curie Grant No 838225. MCG: Stazione Zoologica A. Dohrn (Napoli) and the Ischia Marine Center technical staff; Open University PhD programme; ASSEMBLE; PON-MODO project (Campania Region, Italy), RITMARE - Flag project, Italy; MARES Consortium. Thanks to the ECCSEL - NatLab Italy facilities, managed by the OGS (Trieste), to support collection at Panarea and Vulcano islands. JDH: NERC award NE/T001577/1. MHT: Deutsche Forschungsgemeinschaft (DFG), Grant Number TO563/7-1. EG and MV: Labex ‘Who Am I?’ (No. ANR-11-LABX-0071) funded by the French Government through its ‘Investments for the Future’ program operated by the ANR under Grant No. ANR-11-IDEX-0005-01, Centre National de la Recherche Scientifique (DBM Grant), Université de Paris (IDEX Emergence grant 2020), Agence Nationale de la Recherche (Grant TELOBLAST no. ANR-16-CE91-0007; Grant STEM No. ANR-19-CE27-0027-02), the «Association pour la Recherche sur le Cancer» (Grant PJA 20191209482), and the «Ligue Nationale Contre le Cancer» (Grant RS20/75-20). SQS: NSF (US) Award IOS-1455185, MOST (TW) 108-2311-B-001-002-MY3, Academia Sinica Career Development Award AS-CDA-110-L02, and the Institute of Cellular and Organismic Biology (ICOB) of Academia Sinica (TW). YWH: Deutsche Forschungsgemeinschaft (DFG), grant number TO563/7-1 (to Pavel Tomancak). OS: Austrian Science Fund Grant P32190. GB: The Balavoine Lab was funded by the CNRS, the Université de Paris and grants from the ANR (TELOBLAST no. ANR-16-CE91-0007) and from the ARC (PJA 20181208248). FR and KTR: T

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Özpolat, B. D., Randel, N., Williams, E. A., Bezares-Calderón, L. A., Andreatta, G., Balavoine, G., Bertucci, P. Y., Ferrier, D. E. K., Gambi, M. C., Gazave, E., Handberg-Thorsager, M., Hardege, J., Hird, C., Hsieh, Y.-W., Hui, J., Mutemi, K. N., Schneider, S. Q., Simakov, O., Vergara, H. M., Vervoort, H., Jekley, G., Tessmar-Raible, K., Raible, F., Arendt, D. The Nereid on the rise: Platynereis as a model system. EvoDevo, 12(1), (2021): 10, https://doi.org/10.1186/s13227-021-00180-3., The Nereid Platynereis dumerilii (Audouin and Milne Edwards (Annales des Sciences Naturelles 1:195–269, 1833) is a marine annelid that belongs to the Nereididae, a family of errant polychaete worms. The Nereid shows a pelago-benthic life cycle: as a general characteristic for the superphylum of Lophotrochozoa/Spiralia, it has spirally cleaving embryos developing into swimming trochophore larvae. The larvae then metamorphose into benthic worms living in self-spun tubes on macroalgae. Platynereis is used as a model for genetics, regeneration, reproduction biology, development, evolution, chronobiology, neurobiology, ecology, ecotoxicology, and most recently also for connectomics and single-cell genomics. Research on the Nereid started with studies on eye development and spiralian embryogenesis in the nineteenth and early twentieth centuries. Transitioning into the molecular era, Platynereis research focused on posterior growth and regeneration, neuroendocrinology, circadian and lunar cycles, fertilization, and oocyte maturation. Other work covered segmentation, photoreceptors and other sensory cells, nephridia, and population dynamics. Most recently, the unique advantages of the Nereid young worm for whole-body volume electron microscopy and single-cell sequencing became apparent, enabling the tracing of all neurons in its rope-ladder-like central nervous system, and the construction of multimodal cellular atlases. Here, we provide an overview of current topics and methodologies for P. dumerilii, with the aim of stimulating further interest into our unique model and expanding the active and vibrant Platynereis community., Funding resources are shown after author initials. EAW: BBSRC David Phillips Fellowship BB/T00990X/1. BDÖ: NIH NIGMS MIRA 1R35GM138008-01; NSF-EDGE Award no 1923429; Hibbitt Startup Funds. GJ, LABC, CH: Wellcome Trust Investigator Award 214337/Z/18/Z. KNM: Marie Sklodowska-Curie fellow supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 766053, project EvoCELL. NR: European Union Horizon 2020, Marie Skłodowska-Curie Grant No 838225. MCG: Stazione Zoologica A. Dohrn (Napoli) and the Ischia Marine Center technical staff; Open University PhD programme; ASSEMBLE; PON-MODO project (Campania Region, Italy), RITMARE - Flag project, Italy; MARES Consortium. Thanks to the ECCSEL - NatLab Italy facilities, managed by the OGS (Trieste), to support collection at Panarea and Vulcano islands. JDH: NERC award NE/T001577/1. MHT: Deutsche Forschungsgemeinschaft (DFG), Grant Number TO563/7-1. EG and MV: Labex ‘Who Am I?’ (No. ANR-11-LABX-0071) funded by the French Government through its ‘Investments for the Future’ program operated by the ANR under Grant No. ANR-11-IDEX-0005-01, Centre National de la Recherche Scientifique (DBM Grant), Université de Paris (IDEX Emergence grant 2020), Agence Nationale de la Recherche (Grant TELOBLAST no. ANR-16-CE91-0007; Grant STEM No. ANR-19-CE27-0027-02), the «Association pour la Recherche sur le Cancer» (Grant PJA 20191209482), and the «Ligue Nationale Contre le Cancer» (Grant RS20/75-20). SQS: NSF (US) Award IOS-1455185, MOST (TW) 108-2311-B-001-002-MY3, Academia Sinica Career Development Award AS-CDA-110-L02, and the Institute of Cellular and Organismic Biology (ICOB) of Academia Sinica (TW). YWH: Deutsche Forschungsgemeinschaft (DFG), grant number TO563/7-1 (to Pavel Tomancak). OS: Austrian Science Fund Grant P32190. GB: The Balavoine Lab was funded by the CNRS, the Université de Paris and grants from the ANR (TELOBLAST no. ANR-16-CE91-0007) and from the ARC (PJA 20181208248). FR and KTR: T

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Özpolat, B. D., Randel, N., Williams, E. A., Bezares-Calderón, L. A., Andreatta, G., Balavoine, G., Bertucci, P. Y., Ferrier, D. E. K., Gambi, M. C., Gazave, E., Handberg-Thorsager, M., Hardege, J., Hird, C., Hsieh, Y.-W., Hui, J., Mutemi, K. N., Schneider, S. Q., Simakov, O., Vergara, H. M., Jékely, G., Tessmar-Raible, K., Raible, F., Arendt, D. The Nereid on the rise: Platynereis as a model system. EvoDevo, 12(1), (2021): 10, https://doi.org/10.1186/s13227-021-00180-3., The Nereid Platynereis dumerilii (Audouin and Milne Edwards (Annales des Sciences Naturelles 1:195–269, 1833) is a marine annelid that belongs to the Nereididae, a family of errant polychaete worms. The Nereid shows a pelago-benthic life cycle: as a general characteristic for the superphylum of Lophotrochozoa/Spiralia, it has spirally cleaving embryos developing into swimming trochophore larvae. The larvae then metamorphose into benthic worms living in self-spun tubes on macroalgae. Platynereis is used as a model for genetics, regeneration, reproduction biology, development, evolution, chronobiology, neurobiology, ecology, ecotoxicology, and most recently also for connectomics and single-cell genomics. Research on the Nereid started with studies on eye development and spiralian embryogenesis in the nineteenth and early twentieth centuries. Transitioning into the molecular era, Platynereis research focused on posterior growth and regeneration, neuroendocrinology, circadian and lunar cycles, fertilization, and oocyte maturation. Other work covered segmentation, photoreceptors and other sensory cells, nephridia, and population dynamics. Most recently, the unique advantages of the Nereid young worm for whole-body volume electron microscopy and single-cell sequencing became apparent, enabling the tracing of all neurons in its rope-ladder-like central nervous system, and the construction of multimodal cellular atlases. Here, we provide an overview of current topics and methodologies for P. dumerilii, with the aim of stimulating further interest into our unique model and expanding the active and vibrant Platynereis community., Funding resources are shown after author initials. EAW: BBSRC David Phillips Fellowship BB/T00990X/1. BDÖ: NIH NIGMS MIRA 1R35GM138008-01; NSF-EDGE Award no 1923429; Hibbitt Startup Funds. GJ, LABC, CH: Wellcome Trust Investigator Award 214337/Z/18/Z. KNM: Marie Sklodowska-Curie fellow supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 766053, project EvoCELL. NR: European Union Horizon 2020, Marie Skłodowska-Curie Grant No 838225. MCG: Stazione Zoologica A. Dohrn (Napoli) and the Ischia Marine Center technical staff; Open University PhD programme; ASSEMBLE; PON-MODO project (Campania Region, Italy), RITMARE - Flag project, Italy; MARES Consortium. Thanks to the ECCSEL - NatLab Italy facilities, managed by the OGS (Trieste), to support collection at Panarea and Vulcano islands. JDH: NERC award NE/T001577/1. MHT: Deutsche Forschungsgemeinschaft (DFG), Grant Number TO563/7-1. EG and MV: Labex ‘Who Am I?’ (No. ANR-11-LABX-0071) funded by the French Government through its ‘Investments for the Future’ program operated by the ANR under Grant No. ANR-11-IDEX-0005-01, Centre National de la Recherche Scientifique (DBM Grant), Université de Paris (IDEX Emergence grant 2020), Agence Nationale de la Recherche (Grant TELOBLAST no. ANR-16-CE91-0007; Grant STEM No. ANR-19-CE27-0027-02), the «Association pour la Recherche sur le Cancer» (Grant PJA 20191209482), and the «Ligue Nationale Contre le Cancer» (Grant RS20/75-20). SQS: NSF (US) Award IOS-1455185, MOST (TW) 108-2311-B-001-002-MY3, Academia Sinica Career Development Award AS-CDA-110-L02, and the Institute of Cellular and Organismic Biology (ICOB) of Academia Sinica (TW). YWH: Deutsche Forschungsgemeinschaft (DFG), grant number TO563/7-1 (to Pavel Tomancak). OS: Austrian Science Fund Grant P32190. GB: The Balavoine Lab was funded by the CNRS, the Université de Paris and grants from the ANR (TELOBLAST no. ANR-16-CE91-0007) and from the ARC (PJA 20181208248). FR and KTR: T

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Özpolat, B. D., Randel, N., Williams, E. A., Bezares-Calderón, L. A., Andreatta, G., Balavoine, G., Bertucci, P. Y., Ferrier, D. E. K., Gambi, M. C., Gazave, E., Handberg-Thorsager, M., Hardege, J., Hird, C., Hsieh, Y.-W., Hui, J., Mutemi, K. N., Schneider, S. Q., Simakov, O., Vergara, H. M., Vervoort, H., Jekley, G., Tessmar-Raible, K., Raible, F., Arendt, D. The Nereid on the rise: Platynereis as a model system. EvoDevo, 12(1), (2021): 10, https://doi.org/10.1186/s13227-021-00180-3., The Nereid Platynereis dumerilii (Audouin and Milne Edwards (Annales des Sciences Naturelles 1:195–269, 1833) is a marine annelid that belongs to the Nereididae, a family of errant polychaete worms. The Nereid shows a pelago-benthic life cycle: as a general characteristic for the superphylum of Lophotrochozoa/Spiralia, it has spirally cleaving embryos developing into swimming trochophore larvae. The larvae then metamorphose into benthic worms living in self-spun tubes on macroalgae. Platynereis is used as a model for genetics, regeneration, reproduction biology, development, evolution, chronobiology, neurobiology, ecology, ecotoxicology, and most recently also for connectomics and single-cell genomics. Research on the Nereid started with studies on eye development and spiralian embryogenesis in the nineteenth and early twentieth centuries. Transitioning into the molecular era, Platynereis research focused on posterior growth and regeneration, neuroendocrinology, circadian and lunar cycles, fertilization, and oocyte maturation. Other work covered segmentation, photoreceptors and other sensory cells, nephridia, and population dynamics. Most recently, the unique advantages of the Nereid young worm for whole-body volume electron microscopy and single-cell sequencing became apparent, enabling the tracing of all neurons in its rope-ladder-like central nervous system, and the construction of multimodal cellular atlases. Here, we provide an overview of current topics and methodologies for P. dumerilii, with the aim of stimulating further interest into our unique model and expanding the active and vibrant Platynereis community., Funding resources are shown after author initials. EAW: BBSRC David Phillips Fellowship BB/T00990X/1. BDÖ: NIH NIGMS MIRA 1R35GM138008-01; NSF-EDGE Award no 1923429; Hibbitt Startup Funds. GJ, LABC, CH: Wellcome Trust Investigator Award 214337/Z/18/Z. KNM: Marie Sklodowska-Curie fellow supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 766053, project EvoCELL. NR: European Union Horizon 2020, Marie Skłodowska-Curie Grant No 838225. MCG: Stazione Zoologica A. Dohrn (Napoli) and the Ischia Marine Center technical staff; Open University PhD programme; ASSEMBLE; PON-MODO project (Campania Region, Italy), RITMARE - Flag project, Italy; MARES Consortium. Thanks to the ECCSEL - NatLab Italy facilities, managed by the OGS (Trieste), to support collection at Panarea and Vulcano islands. JDH: NERC award NE/T001577/1. MHT: Deutsche Forschungsgemeinschaft (DFG), Grant Number TO563/7-1. EG and MV: Labex ‘Who Am I?’ (No. ANR-11-LABX-0071) funded by the French Government through its ‘Investments for the Future’ program operated by the ANR under Grant No. ANR-11-IDEX-0005-01, Centre National de la Recherche Scientifique (DBM Grant), Université de Paris (IDEX Emergence grant 2020), Agence Nationale de la Recherche (Grant TELOBLAST no. ANR-16-CE91-0007; Grant STEM No. ANR-19-CE27-0027-02), the «Association pour la Recherche sur le Cancer» (Grant PJA 20191209482), and the «Ligue Nationale Contre le Cancer» (Grant RS20/75-20). SQS: NSF (US) Award IOS-1455185, MOST (TW) 108-2311-B-001-002-MY3, Academia Sinica Career Development Award AS-CDA-110-L02, and the Institute of Cellular and Organismic Biology (ICOB) of Academia Sinica (TW). YWH: Deutsche Forschungsgemeinschaft (DFG), grant number TO563/7-1 (to Pavel Tomancak). OS: Austrian Science Fund Grant P32190. GB: The Balavoine Lab was funded by the CNRS, the Université de Paris and grants from the ANR (TELOBLAST no. ANR-16-CE91-0007) and from the ARC (PJA 20181208248). FR and KTR: T

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Özpolat, B. D., Randel, N., Williams, E. A., Bezares-Calderón, L. A., Andreatta, G., Balavoine, G., Bertucci, P. Y., Ferrier, D. E. K., Gambi, M. C., Gazave, E., Handberg-Thorsager, M., Hardege, J., Hird, C., Hsieh, Y.-W., Hui, J., Mutemi, K. N., Schneider, S. Q., Simakov, O., Vergara, H. M., Vervoort, H., Jekley, G., Tessmar-Raible, K., Raible, F., Arendt, D. The Nereid on the rise: Platynereis as a model system. EvoDevo, 12(1), (2021): 10, https://doi.org/10.1186/s13227-021-00180-3., The Nereid Platynereis dumerilii (Audouin and Milne Edwards (Annales des Sciences Naturelles 1:195–269, 1833) is a marine annelid that belongs to the Nereididae, a family of errant polychaete worms. The Nereid shows a pelago-benthic life cycle: as a general characteristic for the superphylum of Lophotrochozoa/Spiralia, it has spirally cleaving embryos developing into swimming trochophore larvae. The larvae then metamorphose into benthic worms living in self-spun tubes on macroalgae. Platynereis is used as a model for genetics, regeneration, reproduction biology, development, evolution, chronobiology, neurobiology, ecology, ecotoxicology, and most recently also for connectomics and single-cell genomics. Research on the Nereid started with studies on eye development and spiralian embryogenesis in the nineteenth and early twentieth centuries. Transitioning into the molecular era, Platynereis research focused on posterior growth and regeneration, neuroendocrinology, circadian and lunar cycles, fertilization, and oocyte maturation. Other work covered segmentation, photoreceptors and other sensory cells, nephridia, and population dynamics. Most recently, the unique advantages of the Nereid young worm for whole-body volume electron microscopy and single-cell sequencing became apparent, enabling the tracing of all neurons in its rope-ladder-like central nervous system, and the construction of multimodal cellular atlases. Here, we provide an overview of current topics and methodologies for P. dumerilii, with the aim of stimulating further interest into our unique model and expanding the active and vibrant Platynereis community., Funding resources are shown after author initials. EAW: BBSRC David Phillips Fellowship BB/T00990X/1. BDÖ: NIH NIGMS MIRA 1R35GM138008-01; NSF-EDGE Award no 1923429; Hibbitt Startup Funds. GJ, LABC, CH: Wellcome Trust Investigator Award 214337/Z/18/Z. KNM: Marie Sklodowska-Curie fellow supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 766053, project EvoCELL. NR: European Union Horizon 2020, Marie Skłodowska-Curie Grant No 838225. MCG: Stazione Zoologica A. Dohrn (Napoli) and the Ischia Marine Center technical staff; Open University PhD programme; ASSEMBLE; PON-MODO project (Campania Region, Italy), RITMARE - Flag project, Italy; MARES Consortium. Thanks to the ECCSEL - NatLab Italy facilities, managed by the OGS (Trieste), to support collection at Panarea and Vulcano islands. JDH: NERC award NE/T001577/1. MHT: Deutsche Forschungsgemeinschaft (DFG), Grant Number TO563/7-1. EG and MV: Labex ‘Who Am I?’ (No. ANR-11-LABX-0071) funded by the French Government through its ‘Investments for the Future’ program operated by the ANR under Grant No. ANR-11-IDEX-0005-01, Centre National de la Recherche Scientifique (DBM Grant), Université de Paris (IDEX Emergence grant 2020), Agence Nationale de la Recherche (Grant TELOBLAST no. ANR-16-CE91-0007; Grant STEM No. ANR-19-CE27-0027-02), the «Association pour la Recherche sur le Cancer» (Grant PJA 20191209482), and the «Ligue Nationale Contre le Cancer» (Grant RS20/75-20). SQS: NSF (US) Award IOS-1455185, MOST (TW) 108-2311-B-001-002-MY3, Academia Sinica Career Development Award AS-CDA-110-L02, and the Institute of Cellular and Organismic Biology (ICOB) of Academia Sinica (TW). YWH: Deutsche Forschungsgemeinschaft (DFG), grant number TO563/7-1 (to Pavel Tomancak). OS: Austrian Science Fund Grant P32190. GB: The Balavoine Lab was funded by the CNRS, the Université de Paris and grants from the ANR (TELOBLAST no. ANR-16-CE91-0007) and from the ARC (PJA 20181208248). FR and KTR: T

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Özpolat, B. D., Randel, N., Williams, E. A., Bezares-Calderón, L. A., Andreatta, G., Balavoine, G., Bertucci, P. Y., Ferrier, D. E. K., Gambi, M. C., Gazave, E., Handberg-Thorsager, M., Hardege, J., Hird, C., Hsieh, Y.-W., Hui, J., Mutemi, K. N., Schneider, S. Q., Simakov, O., Vergara, H. M., Jékely, G., Tessmar-Raible, K., Raible, F., Arendt, D. The Nereid on the rise: Platynereis as a model system. EvoDevo, 12(1), (2021): 10, https://doi.org/10.1186/s13227-021-00180-3., The Nereid Platynereis dumerilii (Audouin and Milne Edwards (Annales des Sciences Naturelles 1:195–269, 1833) is a marine annelid that belongs to the Nereididae, a family of errant polychaete worms. The Nereid shows a pelago-benthic life cycle: as a general characteristic for the superphylum of Lophotrochozoa/Spiralia, it has spirally cleaving embryos developing into swimming trochophore larvae. The larvae then metamorphose into benthic worms living in self-spun tubes on macroalgae. Platynereis is used as a model for genetics, regeneration, reproduction biology, development, evolution, chronobiology, neurobiology, ecology, ecotoxicology, and most recently also for connectomics and single-cell genomics. Research on the Nereid started with studies on eye development and spiralian embryogenesis in the nineteenth and early twentieth centuries. Transitioning into the molecular era, Platynereis research focused on posterior growth and regeneration, neuroendocrinology, circadian and lunar cycles, fertilization, and oocyte maturation. Other work covered segmentation, photoreceptors and other sensory cells, nephridia, and population dynamics. Most recently, the unique advantages of the Nereid young worm for whole-body volume electron microscopy and single-cell sequencing became apparent, enabling the tracing of all neurons in its rope-ladder-like central nervous system, and the construction of multimodal cellular atlases. Here, we provide an overview of current topics and methodologies for P. dumerilii, with the aim of stimulating further interest into our unique model and expanding the active and vibrant Platynereis community., Funding resources are shown after author initials. EAW: BBSRC David Phillips Fellowship BB/T00990X/1. BDÖ: NIH NIGMS MIRA 1R35GM138008-01; NSF-EDGE Award no 1923429; Hibbitt Startup Funds. GJ, LABC, CH: Wellcome Trust Investigator Award 214337/Z/18/Z. KNM: Marie Sklodowska-Curie fellow supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 766053, project EvoCELL. NR: European Union Horizon 2020, Marie Skłodowska-Curie Grant No 838225. MCG: Stazione Zoologica A. Dohrn (Napoli) and the Ischia Marine Center technical staff; Open University PhD programme; ASSEMBLE; PON-MODO project (Campania Region, Italy), RITMARE - Flag project, Italy; MARES Consortium. Thanks to the ECCSEL - NatLab Italy facilities, managed by the OGS (Trieste), to support collection at Panarea and Vulcano islands. JDH: NERC award NE/T001577/1. MHT: Deutsche Forschungsgemeinschaft (DFG), Grant Number TO563/7-1. EG and MV: Labex ‘Who Am I?’ (No. ANR-11-LABX-0071) funded by the French Government through its ‘Investments for the Future’ program operated by the ANR under Grant No. ANR-11-IDEX-0005-01, Centre National de la Recherche Scientifique (DBM Grant), Université de Paris (IDEX Emergence grant 2020), Agence Nationale de la Recherche (Grant TELOBLAST no. ANR-16-CE91-0007; Grant STEM No. ANR-19-CE27-0027-02), the «Association pour la Recherche sur le Cancer» (Grant PJA 20191209482), and the «Ligue Nationale Contre le Cancer» (Grant RS20/75-20). SQS: NSF (US) Award IOS-1455185, MOST (TW) 108-2311-B-001-002-MY3, Academia Sinica Career Development Award AS-CDA-110-L02, and the Institute of Cellular and Organismic Biology (ICOB) of Academia Sinica (TW). YWH: Deutsche Forschungsgemeinschaft (DFG), grant number TO563/7-1 (to Pavel Tomancak). OS: Austrian Science Fund Grant P32190. GB: The Balavoine Lab was funded by the CNRS, the Université de Paris and grants from the ANR (TELOBLAST no. ANR-16-CE91-0007) and from the ARC (PJA 20181208248). FR and KTR: T

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kuehn, E., Stockinger, A. W., Girard, J., Raible, F., & Özpolat, B. D. A scalable culturing system for the marine annelid Platynereis dumerilii. Plos One, 14(12), (2019): e0226156, doi: 10.1371/journal.pone.0226156., Platynereis dumerilii is a marine segmented worm (annelid) with externally fertilized embryos and it can be cultured for the full life cycle in the laboratory. The accessibility of embryos and larvae combined with the breadth of the established molecular and functional techniques has made P. dumerilii an attractive model for studying development, cell lineages, cell type evolution, reproduction, regeneration, the nervous system, and behavior. Traditionally, these worms have been kept in rooms dedicated for their culture. This allows for the regulation of temperature and light cycles, which is critical to synchronizing sexual maturation. However, regulating the conditions of a whole room has limitations, especially if experiments require being able to change culturing conditions. Here we present scalable and flexible culture methods that provide ability to control the environmental conditions, and have a multi-purpose culture space. We provide a closed setup shelving design with proper light conditions necessary for P. dumerilii to mature. We also implemented a standardized method of feeding P. dumerilii cultures with powdered spirulina which relieves the ambiguity associated with using frozen spinach, and helps standardize nutrition conditions across experiments and across different labs. By using these methods, we were able to raise mature P. dumerilii, capable of spawning and producing viable embryos for experimentation and replenishing culture populations. These methods will allow for the further accessibility of P. dumerilii as a model system, and they can be adapted for other aquatic organisms., BDO received funding from Hibbitt Startup Funds. FR received funding from projects P30035, and I2972, by Austrian Science Fund (FWF). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kuehn, E., Stockinger, A. W., Girard, J., Raible, F., & Özpolat, B. D. A scalable culturing system for the marine annelid Platynereis dumerilii. Plos One, 14(12), (2019): e0226156, doi: 10.1371/journal.pone.0226156., Platynereis dumerilii is a marine segmented worm (annelid) with externally fertilized embryos and it can be cultured for the full life cycle in the laboratory. The accessibility of embryos and larvae combined with the breadth of the established molecular and functional techniques has made P. dumerilii an attractive model for studying development, cell lineages, cell type evolution, reproduction, regeneration, the nervous system, and behavior. Traditionally, these worms have been kept in rooms dedicated for their culture. This allows for the regulation of temperature and light cycles, which is critical to synchronizing sexual maturation. However, regulating the conditions of a whole room has limitations, especially if experiments require being able to change culturing conditions. Here we present scalable and flexible culture methods that provide ability to control the environmental conditions, and have a multi-purpose culture space. We provide a closed setup shelving design with proper light conditions necessary for P. dumerilii to mature. We also implemented a standardized method of feeding P. dumerilii cultures with powdered spirulina which relieves the ambiguity associated with using frozen spinach, and helps standardize nutrition conditions across experiments and across different labs. By using these methods, we were able to raise mature P. dumerilii, capable of spawning and producing viable embryos for experimentation and replenishing culture populations. These methods will allow for the further accessibility of P. dumerilii as a model system, and they can be adapted for other aquatic organisms., BDO received funding from Hibbitt Startup Funds. FR received funding from projects P30035, and I2972, by Austrian Science Fund (FWF). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kuehn, E., Stockinger, A. W., Girard, J., Raible, F., & Özpolat, B. D. A scalable culturing system for the marine annelid Platynereis dumerilii. Plos One, 14(12), (2019): e0226156, doi: 10.1371/journal.pone.0226156., Platynereis dumerilii is a marine segmented worm (annelid) with externally fertilized embryos and it can be cultured for the full life cycle in the laboratory. The accessibility of embryos and larvae combined with the breadth of the established molecular and functional techniques has made P. dumerilii an attractive model for studying development, cell lineages, cell type evolution, reproduction, regeneration, the nervous system, and behavior. Traditionally, these worms have been kept in rooms dedicated for their culture. This allows for the regulation of temperature and light cycles, which is critical to synchronizing sexual maturation. However, regulating the conditions of a whole room has limitations, especially if experiments require being able to change culturing conditions. Here we present scalable and flexible culture methods that provide ability to control the environmental conditions, and have a multi-purpose culture space. We provide a closed setup shelving design with proper light conditions necessary for P. dumerilii to mature. We also implemented a standardized method of feeding P. dumerilii cultures with powdered spirulina which relieves the ambiguity associated with using frozen spinach, and helps standardize nutrition conditions across experiments and across different labs. By using these methods, we were able to raise mature P. dumerilii, capable of spawning and producing viable embryos for experimentation and replenishing culture populations. These methods will allow for the further accessibility of P. dumerilii as a model system, and they can be adapted for other aquatic organisms., BDO received funding from Hibbitt Startup Funds. FR received funding from projects P30035, and I2972, by Austrian Science Fund (FWF). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Even though chitin is one of themost abundant biopolymers in nature, current knowledge on chitin formation is largely based only on data from fungi and insects. This study reveals unanticipated broad taxonomic distribution and extensive diversification of chitin synthases (CSs) in Metazoa, shedding newlight on the relevance of chitin in animals and suggesting unforeseen complexity of chitin synthesis in many groups. We uncovered robust orthologs to insect type CSs in several representatives of deuterostomes, which generally are not thought to possess chitin. This suggests a broader distribution and function of chitin in this branch of the animal kingdom. We characterize a new CS type present not only in basal metazoans such as sponges and cnidarians but also in several bilaterian representatives. Themost extensive diversification of CSs took place during emergence of lophotrochozoans, the third large group of protostomes next to arthropods and nematodes, resulting in coexistence of up to ten CS paralogs inmolluscs. Independent fusion to different kinds of myosinmotor domains in fungi and lophotrochozoans points toward high relevance of CS interaction with the cytoskeleton for fine-tuned chitin secretion. Given the fundamental role that chitin plays in themorphology of many animals, the here presented CS diversification revealsmany evolutionary complexities. Our findings strongly suggest a very broad andmultifarious occurrence of chitin and question an ancestral role as cuticular component. The molecular mechanisms underlying regulation of animal chitin synthesis are most likely far more complex and diverse than existing data from insects suggest.

Tribolium castaneum is a representative of earth’s most numerous eukaryotic order, a powerful model organism for the study of generalized insect development, and also an important pest of stored agricultural products. We describe its genome sequence here. This omnivorous beetle has evolved an ability to interact with a diverse chemical environment as evidenced by large expansions in odorant and gustatory receptors, as well as p450 and other detoxification enzymes. Developmental patterns in Tribolium are more representative of other arthropods than those found in Drosophila, a fact represented in gene content and function. For one, Tribolium has retained more ancestral genes involved in cell-cell communication than Drosophila, and some are expressed in the growth zone crucial for axial elongation in short germ development. Systemic RNAi in T. castaneum appears to use mechanisms distinct from those found in C. elegans, but nevertheless offers similar power for the elucidation of gene function and identification of targets for selective insect control.

We report the sequence and analysis of the 814-megabase genome of the sea urchin Strongylocentrotus purpuratus, a model for developmental and systems biology. The sequencing strategy combined whole-genome shotgun and bacterial artificial chromosome (BAC) sequences. This use of BAC clones, aided by a pooling strategy, overcame difficulties associated with high heterozygosity of the genome. The genome encodes about 23,300 genes, including many previously thought to be vertebrate innovations or known only outside the deuterostomes. This echinoderm genome provides an evolutionary outgroup for the chordates and yields insights into the evolution of deuterostomes.

The term "pattern formation" refers to the process by which order unfolds in development. The present thesis deals with a particular aspect of molecular pattern formation during vertebrate embryogenesis. The model system in the focus of this study is the zebrafish, Danio rerio. In the early developmental phases of the zebrafish, Fibroblast growth factors (Fgfs) are involved in the molecular patterning of various tissues, including two regions of the brain, the forebrain and the midbrain-hindbrain region, affecting cellular processes as diverse as cell proliferation, differentiation, and axonal targeting. The goal of this study was to better understand the mechanisms by which Fgf signaling regulates pattern formation and embryogenesis. I addressed this question on several levels, investigating the extent of intracellular signaling (MAPK activation) relative to sources of Fgf expression, and the transcriptional responses of cells to Fgf signaling during embryogenesis. By a macroarray analysis, I identified putative transcriptional targets of Fgf signaling in late gastrulation, providing a set of molecules that are likely to act as functional players in relaying the patterning information encoded by Fgf signals. Among those are the secreted signaling molecules Chordin and Wnt8, as well as Isthmin, a novel secreted molecule that I found capable to interfere with anterior embryonic patterning. In addition, I identified two ETS domain transcription factors, Erm and Pea3, which constitute bona fide integrators of FgfR signaling. By gain- and loss-of-function studies, I demonstrate that transcript levels of erm and pea3 are tightly regulated by Fgf signaling. Detailed analysis of the expression patterns of erm and pea3 along with other Fgf target genes also provides evidence for a differential read-out of Fgf concentration in the embryo, consistent with a role of Fgf as a vertebrate morphogen. The discovery of novel molecular components downstream of Fgf r

The term "pattern formation" refers to the process by which order unfolds in development. The present thesis deals with a particular aspect of molecular pattern formation during vertebrate embryogenesis. The model system in the focus of this study is the zebrafish, Danio rerio. In the early developmental phases of the zebrafish, Fibroblast growth factors (Fgfs) are involved in the molecular patterning of various tissues, including two regions of the brain, the forebrain and the midbrain-hindbrain region, affecting cellular processes as diverse as cell proliferation, differentiation, and axonal targeting. The goal of this study was to better understand the mechanisms by which Fgf signaling regulates pattern formation and embryogenesis. I addressed this question on several levels, investigating the extent of intracellular signaling (MAPK activation) relative to sources of Fgf expression, and the transcriptional responses of cells to Fgf signaling during embryogenesis. By a macroarray analysis, I identified putative transcriptional targets of Fgf signaling in late gastrulation, providing a set of molecules that are likely to act as functional players in relaying the patterning information encoded by Fgf signals. Among those are the secreted signaling molecules Chordin and Wnt8, as well as Isthmin, a novel secreted molecule that I found capable to interfere with anterior embryonic patterning. In addition, I identified two ETS domain transcription factors, Erm and Pea3, which constitute bona fide integrators of FgfR signaling. By gain- and loss-of-function studies, I demonstrate that transcript levels of erm and pea3 are tightly regulated by Fgf signaling. Detailed analysis of the expression patterns of erm and pea3 along with other Fgf target genes also provides evidence for a differential read-out of Fgf concentration in the embryo, consistent with a role of Fgf as a vertebrate morphogen. The discovery of novel molecular components downstream of Fgf r

The term "pattern formation" refers to the process by which order unfolds in development. The present thesis deals with a particular aspect of molecular pattern formation during vertebrate embryogenesis. The model system in the focus of this study is the zebrafish, Danio rerio. In the early developmental phases of the zebrafish, Fibroblast growth factors (Fgfs) are involved in the molecular patterning of various tissues, including two regions of the brain, the forebrain and the midbrain-hindbrain region, affecting cellular processes as diverse as cell proliferation, differentiation, and axonal targeting. The goal of this study was to better understand the mechanisms by which Fgf signaling regulates pattern formation and embryogenesis. I addressed this question on several levels, investigating the extent of intracellular signaling (MAPK activation) relative to sources of Fgf expression, and the transcriptional responses of cells to Fgf signaling during embryogenesis. By a macroarray analysis, I identified putative transcriptional targets of Fgf signaling in late gastrulation, providing a set of molecules that are likely to act as functional players in relaying the patterning information encoded by Fgf signals. Among those are the secreted signaling molecules Chordin and Wnt8, as well as Isthmin, a novel secreted molecule that I found capable to interfere with anterior embryonic patterning. In addition, I identified two ETS domain transcription factors, Erm and Pea3, which constitute bona fide integrators of FgfR signaling. By gain- and loss-of-function studies, I demonstrate that transcript levels of erm and pea3 are tightly regulated by Fgf signaling. Detailed analysis of the expression patterns of erm and pea3 along with other Fgf target genes also provides evidence for a differential read-out of Fgf concentration in the embryo, consistent with a role of Fgf as a vertebrate morphogen. The discovery of novel molecular components downstream of Fgf r

The term "pattern formation" refers to the process by which order unfolds in development. The present thesis deals with a particular aspect of molecular pattern formation during vertebrate embryogenesis. The model system in the focus of this study is the zebrafish, Danio rerio. In the early developmental phases of the zebrafish, Fibroblast growth factors (Fgfs) are involved in the molecular patterning of various tissues, including two regions of the brain, the forebrain and the midbrain-hindbrain region, affecting cellular processes as diverse as cell proliferation, differentiation, and axonal targeting. The goal of this study was to better understand the mechanisms by which Fgf signaling regulates pattern formation and embryogenesis. I addressed this question on several levels, investigating the extent of intracellular signaling (MAPK activation) relative to sources of Fgf expression, and the transcriptional responses of cells to Fgf signaling during embryogenesis. By a macroarray analysis, I identified putative transcriptional targets of Fgf signaling in late gastrulation, providing a set of molecules that are likely to act as functional players in relaying the patterning information encoded by Fgf signals. Among those are the secreted signaling molecules Chordin and Wnt8, as well as Isthmin, a novel secreted molecule that I found capable to interfere with anterior embryonic patterning. In addition, I identified two ETS domain transcription factors, Erm and Pea3, which constitute bona fide integrators of FgfR signaling. By gain- and loss-of-function studies, I demonstrate that transcript levels of erm and pea3 are tightly regulated by Fgf signaling. Detailed analysis of the expression patterns of erm and pea3 along with other Fgf target genes also provides evidence for a differential read-out of Fgf concentration in the embryo, consistent with a role of Fgf as a vertebrate morphogen. The discovery of novel molecular components downstream of Fgf r