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. 2023 Sep 4;12(9):1204.
doi: 10.3390/biology12091204.

Mysterious Morphology: An Investigation of the Octopus Keel and Its Association with Burrowing

Cheyne Springbett  1 , Katie Cordero  1 , Garrett Ellis  1 , Carly Haeger  1 , Kirt L Onthank  1
Affiliations

Mysterious Morphology: An Investigation of the Octopus Keel and Its Association with Burrowing

Cheyne Springbett et al. Biology (Basel). .

Abstract

The octopus keel is a trait that has been hypothesized to be connected with burrowing in octopuses, but has never been explored in any detail. We investigated the association between these two traits using two approaches. First, we examined the phylogenetic correlation between the presence of a keel and known burrowing behavior in cirrate octopuses. Second, burrowing and non-burrowing captive Muusoctopus leioderma were evaluated for keel prominence to determine whether the keel is lost more rapidly in non-burrowing individuals. Pagel's test for the coevolution of binary characteristics showed the model of best fit for the resulting phylogenetic tree to be one of evolutionary interdependence, and that non-burrowing Muusoctopus leioderma lost their keels over time, while burrowing individuals maintained their keels. Together, these results indicate the keel may be a trait associated with burrowing in octopuses.

Keywords: Muusoctopus leioderma; burrowing; evolution; keel; octopus; phylogeny; sediment.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Octopus holding and laboratory setup, with water system, lighting, and all 5 experimental mud tanks shown.
Figure 2
Figure 2
Keel prominence values vs. time in captivity for burrowing and non-burrowing individuals. Individual shapes connected by thin lines show keel prominence for individual octopuses during captivity, with blue showing burrowing individuals and red showing non-burrowers. Thick lines show results of LME. Results show a significant interaction between burrowing and day, with non-burrowing octopuses losing their keels faster than non-burrowers (ANOVA, days/burrow, Χ2 = 4.66, df = 1, p-value = 0.031).
Figure 3
Figure 3
Multi-species phylogenetic tree showing results of Pagel’s binary character correlation test between keel presence and known burrowing/burying behavior. Tree includes 110 benthic octopus species. Results show interdependence to be the model of best fit (AIC = 188.43, p-value < 0.001).
See this image and copyright information in PMC

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