Octopuses are mollusks that have evolved intricate neural systems comparable with vertebrates in terms of cell number, complexity and size. The brain cell types that control their sophisticated behavioral repertoire are still unknown. Here, we profile the cell diversity of the paralarval Octopus vulgaris brain to build a cell type atlas that comprises mostly neural cells, but also multiple glial subtypes, endothelial cells and fibroblasts. We spatially map cell types to the vertical, subesophageal and optic lobes. Investigation of cell type conservation reveals a shared gene signature between glial cells of mouse, fly and octopus. Genes related to learning and memory are enriched in vertical lobe cells, which show molecular similarities with Kenyon cells in Drosophila. We construct a cell type taxonomy revealing transcriptionally related cell types, which tend to appear in the same brain region. Together, our data sheds light on cell type diversity and evolution in the octopus brain.

The common octopus, Octopus vulgaris, is an active marine predator known for the richness and plasticity of its behavioral repertoire, and remarkable learning and memory capabilities. Octopus and other coleoid cephalopods, cuttlefish and squid, possess the largest nervous system among invertebrates, both for cell counts and body to brain size. O. vulgaris has been at the center of a long-tradition of research into diverse aspects of its biology. To leverage research in this iconic species, we generated 270 Gb of genomic sequencing data, complementing those available for the only other sequenced congeneric octopus, Octopus bimaculoides. We show that both genomes are similar in size, but display different levels of heterozygosity and repeats. Our data give a first quantitative glimpse into the rate of coding and non-coding regions and support the view that hundreds of novel genes may have arisen independently despite the close phylogenetic distance. We furthermore describe a reference-guided assembly and an open genomic resource (CephRes-gdatabase), opening new avenues in the study of genomic novelties in cephalopods and their biology.

The capacity of cephalopods (cuttlefish, squid and octopus) to produce contrasting "visual effects" by rapid colour changes of the skin represents one of the most intringuing aspects of their behaviour and evolution This book concerns and compares the multitude of appearances of the skin - or body pattern - exhibited by 21 species of coleoid cephalopods. It is the results of the anlysis of more than 180 works published between 1856 and 2005. In the following pages we provide a short overview of how body pattering in cephalopods is achieved and brought about, and which are selective pressures that drove to its evolution. The volume comprises 705 definitions of the various components/patterns compiled in the form of "anthological reviews". The names (about 1200) coined by the different authors to describe the pattering of the 21 species, toghether with their synonyms and variations, are collected and listed as an "index of terms and synonyms". Synopses, arranged by category, are also included to facilitate comparative analysis accross species."Visual guidance" is achieved with the aid of more than 500 illustrations (mostly original), assembled in 96 plates, which depict the variety and richness of the boby pattering of the 21species considered.

SUMMARY: Octopus arms are extremely dexterous structures. The special arrangements of the muscle fibers and nerve cord allow a rich variety of complex and fine movements under neural control. Historically, the arm structure has been investigated using traditional comparative morphological ex vivo analysis. Here, we employed ultrasound imaging, for the first time, to explore in vivo the arms of the cephalopod mollusc Octopus vulgaris. Sonographic examination (linear transducer, 18 MHz) was carried out in anesthetized animals along the three anatomical planes: transverse, sagittal and horizontal. Images of the arm were comparable to the corresponding histological sections. We were able, in a non-invasive way, to measure the dimensions of the arm and its internal structures such as muscle bundles and neural components. In addition, we evaluated echo intensity signals as an expression of the difference in the muscular organization of the tissues examined (i.e. transverse versus longitudinal muscles), finding different reflectivity based on different arrangements of fibers and their intimate relationship with other tissues. In contrast to classical preparative procedures, ultrasound imaging can provide rapid, destruction-free access to morphological data from numerous specimens, thus extending the range of techniques available for comparative studies of invertebrate morphology.

Octopoda utilise their arms for a diverse range of functions, including locomotion, hunting, defence, exploration, reproduction, and grooming. However the natural environment contains numerous threats to the integrity of arms, including predators and prey during capture. Impressively, octopoda are able to close open wounds in an aquatic environment and can fully regenerate arms. The regrowth phase of cephalopod arm regeneration has been grossly described; however, there is little information about the acute local response that occurs following an amputation injury comparable to that which frequently occurs in the wild. Adult Octopus vulgaris caught in the Bay of Naples were anaesthetised, the distal 10 % of an arm was surgically amputated, and wounded tissue was harvested from animals sacrificed at 2, 6, and 24 h post-amputation. The extent of wound closure was quantified, and the cell and tissue dynamics were observed histologically, by electron microscopy, as well as using ultrasound. Macroscopic, ultrasonic and ultrastructural analyses showed extensive and significant contraction of the wound margins from the earliest time-point, evidenced by tissue puckering. By 6 h post amputation, the wound was 64.0 ± 17.2 % closed compared to 0 h wound area. Wound edge epithelial cells were also seen to be migrating over the wound bed, thus contributing to tissue repair. Temporary protection of the exposed tip in the form of a cellular, non-mucus plug was observed, and cell death was apparent within two hours of injury. At earlier time-points this was apparent in the skin and deeper muscle layers, but ultimately extended to the nerve cord by 24 h. This work has revealed that O. vulgaris ecologically relevant amputation wounds are rapidly repaired via numerous mechanisms that are evolutionarily conserved. The findings provide insights into the early processes of repair preparatory to regeneration. The presence of epithelial, chromatophore, vascular, muscle and neural tissue in the arms makes this a particularly interesting system in which to study acute responses to injury and subsequent regeneration.