a-Genome of Octopus bimaculoides anatomy, highlighting the tissues sampled for transcriptome analysis: viscera (heart, kidney and hepatopancreas), yellow; gonads (ova or testes), peach; retina, orange; optic lobe (OL), maroon; supraesophageal brain (Supra), bright pink; subesophageal brain (Sub), light pink; posterior salivary gland (PSG), purple; axial nerve cord (ANC), red; suckers, grey; skin, mottled brown; stage 15 (St15) embryo, aquamarine. Skin sampled for transcriptome analysis included the eyespot, shown in light blue
The million-dollar question is why are octopuses are so intelligent?
DNA obtained from Octopus bimaculoides was sequenced and it was discovered that octopus possessed unusually high number of protocadherins, genes that regulate neural development. (Specifically ,168 protocadherin genes, 10 X that found in an invertebrate, and 2X that found in mammals.)
The octopus have a large number of transposons, genes that can change their position in the genome. The genes present in O. bimaculoides were not arranged in the doubly conserved synteny nut rather in clusters along the genome. O. bimaculoides had only a single Hox complement unlike multiple copies. This was similar in Hox transcripts in the bobtail squid. Unique to octopus, the Hox genes were not in clusters but completely atomized.
These genes are responsible for the unique behavioral and physiological traits such as possessing the largest nervous systems among invertebrates ,camera-like eyes, highly functional arms, and a remarkably sophisticated adaptive camouflaging .
Joke of the day
Why did the octopus beat the shark in a fight? – Because the octopus was well armed.
Reference
- The octopus genome and the evolution of cephalopod neural and morphological novelties.
Albertin CB, Simakov O, Mitros T, Wang ZY, Pungor JR, Edsinger-Gonzales E, Brenner S, Ragsdale CW, Rokhsar DS. 2015. Nature. 524:220-224. - Duboule, D. The rise and fall of Hox gene clusters. Development 134, 2549–2560 (2007). Retrived online at https://www.nature.com/articles/nature11696