Monthly Archives: March 2018

What makes you unique ?

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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

  1. 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.
  2. Duboule, D. The rise and fall of Hox gene clusters. Development 134, 2549–2560 (2007). Retrived online at https://www.nature.com/articles/nature11696

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Video depicts how  chromatophores embedded in the skin of octopus   expand or contact to enhance camouflaging. Video credit-https://www.youtube.com/watch?v=OWbanx8U4cM

 

Octopus bimaculoide , my species of interest is classified further as member of subclass Coleoidea and order Octopoda. There are various distinguishing features of this organism but I am choosing to headline their chromatophores embedded in their skin for today.

O. bimaculoide, a coleoid cephalopods evade predators by changing the appearance, marking and texture of their skin. Camouflage in cephalopods depend on central nervous system, eyes and skin (chromatophores). (2)

The morphology of chromatophores in coleoid cephalopods is unique compared to other members of mollucsa as well as different phylums such as Arthropoda.(1)

Chromatophores in coleoid cephalopods have evolved into small, elastic pigment granules filled cells with surrounding muscle cells. When the muscle cells contracted, they stretch the cells into pigmented sheet and when the muscles relax, the chromatophore shrinks back to small circles. This contraction and relaxation changes their appearance faster than other animal.(Fig A and B) (1,3)

Cephalopods utilize their well-developed eyes to gather information about the brightness, contrast and edges of light in their surroundings. Information gathered highly affects changes in the color, texture and markings of their skin. This also serves as a means of communication.

New studies has determined that the skin of O. bimaculoides can sense light independent of the central nervous system.It’s ability  to sense light is not as detailed but can sense increases and brightness.(3)

 

 

Chromatophores in skin of O. bimaculoides reaction when illuminated. Photos from infrared video of adult O. bimaculoides funnel skin light-activated chromatophore expansion. (A) Contracted state of chromatophores after 3 s of exposure to bright white light. (B) Expanded chromatophores after 6 s of exposure to bright white light. (C) Chromatophores in skin of O. bimaculoides reaction when illuminated. Scale bars: 100 μm.

 

Joke of the day

How do you make an octopus laugh? You give it ten-tickles.

References

1.Hickman et al (17) Integrated principle of zoology, McGraw-Hill Education chapter 29 page 642. Viewed online on 3/1/2018 at https://newconnect.mheducation.com/flow/connect.html

2.Messenger, J. B. (2001). Cephalopod chromatophores: neurobiology and natural history. Biol. Rev. Camb. Philos. Soc. 76, 473-528. doi:10.1017/S1464793101005772. Viewed online on 3/1/2018 at http://onlinelibrary.wiley.com.ezproxy.gsu.edu/doi/10.1017/S1464793101005772/abstract;jsessionid=EE9341B5C9616D73519F116B64E411F1.f04t02

3.Ramirez M. Desmond, Oakley Todd (2015) Understanding the dermal light sense in the context of integrative photoreceptor cell biology. Journal of Experimental Biology 2015, 218: 1513-1520;  doi: 10.1242/jeb.110908. Viewed online on 3/1/2018 at https://labs.eemb.ucsb.edu/oakley/todd/publications/107