Evolution of cephalopod nervous systems

Probably not a substantial claim: may not pass S3 (load-bearing).

Coleoids divide into eight-armed octopodiforms and ten-armed decapodiforms.

“The major division of coleoid cephalopods is into the eight-armed octopodiforms (octopuses and vampire squids) and the ten-armed decapodiforms (squid and cuttlefish).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Interbrachial connectives carry coordinating axons between arms.

“Interbrachial connectives carry axons of these coordinating neurons between the arms.”

May combine two claims.

Transcriptome sequencing in squid and octopus shows many protocadherins are expressed in the nervous system, suggesting a molecular parallel with vertebrate brains.

“Transcriptome sequencing in both squid and octopus indicates that many of these genes are expressed in the nervous system, suggesting a molecular parallel between the brains of coleoid cephalopods and vertebrates.”

Probably not a substantial claim: may not pass S4 (based).

Understanding how cephalopod brain regions relate to those of vertebrates, insects, annelids, and other animals provides a direct test of hypotheses about brain evolution.

“Beyond the insights gained into cephalopod neurobiology, understanding the evolutionary relationship between cephalopod brain regions to those of vertebrates, insects, annelids, and other animals provides a direct test of important hypotheses on brain evolution.”

May combine two claims.

Cephalopod genomes resemble other invertebrate genomes in having most pan-bilaterian genes in single copy, suggesting no whole-genome duplication like vertebrates.

“At first glance, cephalopod genomes largely resemble those found in other sequenced invertebrates: they possess most pan-bilaterian genes in single copy, suggesting that cephalopod evolution did not undergo a parallel phase of whole genome duplication, as happened in vertebrates.”

May combine two claims.

Ecdysozoans such as Drosophila and C. elegans lack protocadherins, but cephalopod genomes have more than any vertebrate sequenced, estimated at 100 to over 300.

“In contrast to ecdysozoan genomes (including Drosophila melanogaster and Caenorhabditis elegans), which lack any protocadherins, cephalopod genomes encode even more protocadherins than any vertebrate genome sequenced to date; estimates range from 100 to over 300.”

May combine two claims.

Nautiloids lack many coleoid innovations and have an external shell, a pinhole eye, and many digital tentacles without suckers.

“Many coleoid innovations are absent in the nautiloids, which have a true external shell, as well as a pinhole eye, and dozens of digital tentacles that lack suckers.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Most invertebrate genomes have 200-400 C2H2 zinc finger genes, and the human genome has over 700, partly from KRAB-motif gene expansion.

“This family is typically the most abundant transcription factor in many animal genomes: most invertebrate genomes encode 200–400 genes with C2H2 zinc finger motifs. The human genome has more than 700 of these genes, thanks in part to an expansion of the KRAB-motif-containing genes.”

May combine two claims.

The close relationship between cephalopods and monoplacophorans may indicate that some cephalopod traits are elaborations of ancestral features, including a cord-like nervous system similar to that of chitons.

“This close placement with the monoplacophorans may support some cephalopod novelties that appear to be elaborations of the ancestral condition, including an early, cord-like appearance of the nervous system that shows similarities to the cord-based chiton nervous system, which is absent in gastropods and bivalves (Figure 2).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Protocadherins are cell adhesion molecules important for neuronal wiring in vertebrate brains.

“The protocadherins are a family of cell adhesion molecules that play a key role in the development of neuronal wiring in vertebrate brains.”

May combine two claims. The quote only partly states this claim.

Cephalopod embryos are large and yolky, with early bilateral superficial cleavages resembling teleosts rather than spiral cleavage, and they develop directly without larval stages.

“Cephalopod embryos are large and yolky, and early cleavages are bilaterally symmetric and superficial, resembling the early development of teleost fish, rather than the spiral cleavage shared by other molluscs with members of Spiralia, named for this cleavage pattern.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

The cephalopod supraesophageal, buccal, posterior, and anterior subesophageal masses may correspond to cerebral, buccal, palliovisceral, and pedal ganglia in non-cephalopod conchiferans.

“The cephalopod supraesophageal, buccal, posterior and anterior subesophageal masses may correspond to the cerebral, buccal, palliovisceral, and pedal ganglia, respectively, in non-cephalopod conchiferans like gastropods, bivalves, and scaphopods.”

May combine two claims.

Molecular data place nautiloids in Orthoceratoidea, while fossils suggest Multiceratoidea, which would imply an early split of coleoids and nautiloids near 490 million years ago.

“Although molecular data place nautiloids in the Orthoceratoidea clade, fossil evidence suggests that they might belong in Multiceratoidea, which would suggest coleoids and nautiloids diverged early in the evolution of cephalopods, close to 490 million years ago, just 50 million years after the Cambrian explosion.”

May combine two claims.

This widespread neurogenic territory differs from other molluscs, where it is restricted, and from vertebrates, where CNS neurogenesis is confined to the neural tube.

“This widespread neurogenic territory contrasts both with neurodevelopment in other molluscan embryos, which is restricted to discrete territories, and with vertebrate neurodevelopment, which restricts central nervous system neurogenesis to the neural tube — a structure that inverts from the neurectoderm.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Nautiloids have supra- and sub-esophageal masses divided into 13 lobes.

“Nautiloids also have supra- and sub-esophageal masses divided into 13 lobes.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Axial nerve cords carry ascending and descending axons between the periphery and central brain.

“The axial nerve cords also contain ascending and descending axonal projections conveying information between the periphery and the central brain.”

May combine two claims.

Cephalopod genomes contain thousands of C2H2-domain genes, often in clusters.

“In contrast, thousands of C2H2-domain-containing genes have been identified in cephalopod genomes, often in clustered arrays”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The brain and arms add neurons as the octopus grows, increasing thousands-fold from hatching to eight months.

“It is important to note that the brain and the arms continue to add neurons as the octopus grows, increasing thousands fold as an octopus grows from less than a milligram at hatching with just a few suckers on each arm to almost two kilograms with hundreds of suckers by eight months of age.”

May combine two claims.

The brain lies between the eyes, with optic lobes on each side and central brain divided into supra- and sub-esophageal masses.

“The brain sits between the eyes, with two optic lobes flanking the central brain, which is divided into supra- and sub-esophageal masses (Figure 2A,B).”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The oldest known cephalopods are Cambrian and had an external chambered shell like nautiloids.

“The earliest known cephalopods date from the Cambrian, and like nautiloids have an external, chambered shell.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Vertebrate genomes usually have dozens of protocadherins: 50-70 in mammals and over 100 in teleosts.

“Vertebrate genomes typically encode dozens of protocadherins (50–70 in mammals, 100+ in teleosts).”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The Octopus vulgaris brain is estimated to have about 500 million neurons, six times the mouse brain.

“The brain of Octopus vulgaris is estimated to comprise approximately 500 million neurons — six times the number in the mouse brain.”

May combine two claims.

Cephalopods first appeared more than 490 million years ago and split into Orthoceratoidea, Multiceratoidea, and Endoceratodidea.

“The earliest cephalopods arose over 490 million years ago and diversified into three major clades: Orthoceratoidea, Multiceratoidea, and Endoceratodidea.”

May combine two claims.

Neural progenitors and neurons appear early and are widespread in the embryonic territory; much of the early octopus embryo appears neurectodermal.

“In each case, it has been found that neural progenitors and neurons appear early, as the body plan is set up, and are widespread throughout the embryonic territory — indeed, much of the early octopus embryo appears to be neurectodermal (Figure 4).”

May combine two claims.

The subesophageal mass contains lower motor centers for arms, eyes, mantle, and funnel, and optic lobes process visual information.

“The subesophageal mass contains lower motor centers controlling the arms, eyes, mantle, and funnel, while the optic lobes play a role in visual processing.”

May combine two claims.

Coleoid cephalopod nervous systems are comparable in size to vertebrates but organized differently.

“Coleoid cephalopod nervous systems rival those of vertebrates in size but have an entirely different organization.”

May combine two claims.

About 200 million of these neurons are in the optic lobes and central supraesophageal and subesophageal masses, while 300 million are in the arm axial nerve cords.

“Of these, approximately 200 million are located in the optic lobes and the central supraesophageal and subesophageal masses. The remaining 300 million neurons are distributed throughout the axial nerve cords in the arms, which lie at the center of each arm.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Two extant cephalopod clades exist: Nautilidae and Coleoidea.

“There are only two clades of extant cephalopods: the Nautilidae and the Coleoidea (Figure 1B).”

May combine two claims.

Coleoid supraesophageal and subesophageal masses contain 30-40 lobes, suggesting many neural elaborations are coleoid-specific innovations.

“Coleoid supraesophageal and subesophageal masses have 30–40 individual lobes, which suggests that many of these neural elaborations are coleoid, or lineage-specific, innovations (Figure 3).”

May combine two claims.

These studies find both similar and novel molecular signatures compared with other animals.

“Studies find both similar and novel molecular signatures in the development of these structures to what has been described in other animals.”

May combine two claims.

The vertical and frontal lobe systems mediate visual and tactile learning and memory, respectively, while basal lobes control higher motor functions.

“Within the supraesophageal brain, the vertical lobe system and the frontal lobe system play roles in visual and tactile learning and memory, respectively, whereas the basal lobes play roles in higher motor control.”

May combine two claims.

Cephalopods sit near the base of conchiferans, either as sister to monoplacophorans or to gastropods, bivalves, and scaphopods.

“modern phylogenomic analyses suggest that they branch near the base of the conchiferans, either as a sister group to the enigmatic, deep sea monoplacophorans or as a sister group to the clade containing gastropods, bivalves, and scaphopods.”

May combine two claims.

Shared brain features of nautilus and coleoids predate the first tetrapods by 100 million years and the first dinosaurs by 230 million years.

“Regardless of the precise date, it is clear that the shared features of the brains of nautilus and coleoids existed 100 million years before the first tetrapods and 230 million years before the first dinosaurs.”