Correction: Embryonic development of a centralised brain in coleoid cephalopods

The last common ancestor of cephalopods and vertebrates lived about 580 million years ago, yet coleoid cephalopods, comprising squid, cuttlefish and octopus, have evolved an extraordinary behavioural repertoire that includes learned behaviour and tool utilization. These animals also developed innovative advanced defence mechanisms such as camouflage and ink release. They have evolved unique life cycles and possess the largest invertebrate nervous systems. Thus, studying coleoid cephalopods provides a unique opportunity to gain insights into the evolution and development of large centralised nervous systems. As non-model species, molecular and genetic tools are still limited. However, significant insights have already been gained to deconvolve embryonic brain development. Even though coleoid cephalopods possess a typical molluscan circumesophageal bauplan for their central nervous system, aspects of its development are reminiscent of processes observed in vertebrates as well, such as long-distance neuronal migration. This review provides an overview of embryonic coleoid cephalopod research focusing on the cellular and molecular aspects of neurogenesis, migration and patterning. Additionally, we summarize recent work on neural cell type diversity in embryonic and hatchling cephalopod brains. We conclude by highlighting gaps in our knowledge and routes for future research.

Early life stages of cephalopods are somewhat complex due to the life history strategy or species specificity of generalized ontogenetic patterns and processes. This work aimed to determine the time length of embryonic development at different temperatures, and if the egg size is a determinant of hatchling size in Sepiola atlantica d′Orbigny, 1839–1842. Successful hatching occurred in 98.5–100% of the eggs for each female. As seen in other coleoid cephalopods, temperature determines the amount of time for embryonic development in S. atlantica, and the obtained data were very similar to other coleoid cephalopods. Developmental times for temperatures at 13 ± 0.4°C, 18 ± 0.3°C and 16.4 ± 1.1°C were 61.8 ± 3.8, 22.6 ± 1.7 and 40.1 ± 4.8 days. The duration of embryonic development and hatchling mantle length was not strictly related. The egg volume was positively related to hatchling mantle length. Our results provide new records on the duration of embryogenesis and other information on reproductive patterns in this species. Some hatching and post-hatching behaviour are shown and discussed.

A brief description of the early embryonic development of the circulatory system in a representative of the coleoid cephalopods (Octopus vulgaris) is presented as an example of the rather uniform pattern observed at the outset of organogenesis. The role of the outer yolk sac both in morphogenesis and in the physiology of the embryo is emphasized. On the basis of recent observations reported in the literature, a preliminary comparison with the yolk sac ofNautilus is made, which in particular allows one to assess the relative importance of embryo size and bauplan constraints, respectively.

Coleoid cephalopods, a subclass of mollusks, exhibit remarkable adaptations, including the largest brains among invertebrates, camera-like eyes, and a distinctive embryonic development. They possess an advanced behavioral repertoire including dynamic camouflage. The common cuttlefish Sepia officinalis has served as a key model organism in various research fields, spanning biophysics, neurobiology, behavior, evolution, ecology and biomechanics. More recently, it has become a model to investigate the neural mechanisms underlying cephalopod camouflage, using quantitative behavioral approaches alongside molecular techniques to characterize the identity, evolution and development of neuronal cell types. Despite significant interest in this animal, a high-quality, annotated genome of its species is still lacking. To address this, we sequenced and assembled a chromosome-scale genome for S. officinalis. The final assembly spans 5.68 billion base pairs and comprises 47 repeat-rich chromosomes. Gene linkage analysis confirms the existence of 47 chromosomes, revealing clear homologies with related species such as Euprymna scolopes and Doryteuthis pealeii. Our work includes a comprehensive gene annotation and full-length transcript predictions that should be helpful for further evolutionary and single-cell expression studies. This genome provides a valuable resource for future research on the evolution, brain organization, information processing, development, and behavior in this important clade.

Coleoid cephalopods, a subclass of mollusks, exhibit remarkable adaptations, including the largest brains among invertebrates, camera-like eyes, and a distinctive embryonic development. They possess an advanced behavioral repertoire including dynamic camouflage. The common cuttlefish Sepia officinalis has served as a key model organism in various research fields, spanning biophysics, neurobiology, behavior, evolution, ecology and biomechanics. More recently, it has become a model to investigate the neural mechanisms underlying cephalopod camouflage, using quantitative behavioral approaches alongside molecular techniques to characterize the identity, evolution and development of neuronal cell types. Despite significant interest in this animal, a high-quality, annotated genome of its species is still lacking. To address this, we sequenced and assembled a chromosome-scale genome for S. officinalis. The final assembly spans 5.68 billion base pairs and comprises 47 repeat-rich chromosomes. Gene linkage analysis confirms the existence of 47 chromosomes, revealing clear homologies with related species such as Euprymna scolopes and Doryteuthis pealeii. Our work includes a comprehensive gene annotation and full-length transcript predictions that should be helpful for further evolutionary and single-cell expression studies. This genome provides a valuable resource for future research on the evolution, brain organization, information processing, development, and behavior in this important clade.

Part I: Phylogeny and Systematics 1. Phylogenetic Practices among Scholars of Fossil Cephalopods, with Special Reference to Cladistics Pascal Neige, Isabelle Rouget, and Sebastien Moyne 2. Patterns of Embryonic Development in Early to Middle Devonian Ammonoids Susan M. Klofak, Neil H. Landman, and Royal H. Mapes 3. Mode of Life of the Frasnian (Late Devonian) Ammonoid Manticoceras from Coumiac (Montagne Noire, France) Dieter Korn and Christian Klug 4. GONIAT - The Current State of the Paleontological Database System on Paleozoic Ammonoids Jurgen Kullmann 5. Ornamental polymorphism in Placenticeras kaffrarium (Ammonoidea Upper Cretaceous of India): Evolutionary implications Tapas K. Gangopadhyay and Subhendu Bardhan 6. A Late Carboniferous Coleoid Cephalopod from the Mazon Creek Lagerstatte (USA), with a Radula, Arm Hooks, Mantle Tissues, and Ink Larisa A. Doguzhaeva, Royal H. Mapes, and Harry Mutvei 7. On the Species Status of Spirula spirula (Linne, 1758) (Cephalopoda): A New Approach Based on Divergence of Amino Acid Sequences between the Canaries and New Caledonia Kerstin Warnke Part II: Morphology of Soft and Hard Tissues 8. Understanding Ammonoid Sutures: New Insight into the Dynamic Evolution of Paleozoic Suture Morphology Emily G. Allen 9. Cameral Membranes in Carboniferous and Permian Goniatites: Description and Relationship to Pseudosutures Kristin Polizzotto, Neil H. Landman, and Royal H. Mapes 10. Soft-Tissue Attachment of Middle Triassic Ceratitida from Germany Christian Klug, Michael Montenari, Hartmut Schulz, and Max Urlichs 11. The Preservation of Body Tissues, Shell, and Mandibles in the Ceratitid AmmonoidAustrotrachyceras (Late Triassic), Austria Larisa A. Doguzhaeva, Royal H. Mapes, Herbert Summesberger, and Harry Mutvei 12. Connecting Ring Ultrastructure in the Jurassic Ammonoid Quenstedtoceras with Discussion on Mode of Life of Ammonoids Harry Mutvei and Elena Dunca 13. Jaws and Radula of Baculites from the Upper Cretaceous (Campanian) of North America Neil H. Landman, Neal L. Larson, and William A. Cobban 14 Ultrastructure Analyses on the Conotheca of the Genus Belemnotheutis (Belemnitida: Coleoidea) Dirk Fuchs, Helmut Keupp, Vasilij Mitta, and Theo Engeser Part III: Biogeography, Biostratigraphy, Ecology, and Taphonomy 15. New Data on the Clymeniid Faunas of the Urals and Kazakhstan Svetlana Nikolaeva 16. Deformities in the Late Callovian (Late Middle Jurassic) Ammonite Fauna from Saratov, Russia Neal L. Larson 17. Biogeography of Kutch Ammonites During the Latest Jurassic (Tithonian) and a Global Paleobiogeographic Overview Subhendu Bardhan, Sabyasachi Shome, and Pinaki Roy 18: Ammonite Touch Marks in Upper Cretaceous (Cenomanian-Santonian) Deposits of the Western Interior Seaway Neil H. Landman and William A. Cobban 19: Some Data on the Distribution and Biology of the Boreal Clubhook Squid Moroteuthis robusta (Verrill, 1876) (Onychoteuthidae, Teuthida) in the Northwest Pacific Alexei M. Orlov 20: Habitat Ecology of Enteroctopus dofleini from Middens and Live Prey Surveys in Prince William Sound, Alaska D. Scheel, A. Lauster, and T.L.S. Vincent