Cerebrotypes in Cephalopods: Brain Diversity and Its Correlation With Species Habits, Life History, and Physiological Adaptations

Abstract

Here we analyze existing quantitative data available for cephalopod brains based on classical contributions by J.Z. Young and colleagues, to cite some. We relate the relative brain size of selected regions (area and/or lobe), with behavior, life history, ecology and distribution of several cephalopod species here considered. After hierarchical clustering we identify and describe ten clusters grouping 52 cephalopod species. This allows us to describe cerebrotypes, i.e., differences of brain composition in different species, as a sign of their adaptation to specific niches and/or clades in cephalopod molluscs for the first time. Similarity reflecting niche type has been found in vertebrates, and it is reasonable to assume that it could also occur in Cephalopoda. We also attempted a phylogenetic PCA using data by Lindgren et al. (2012) as input tree. However, due to the limited overlap in species considered, the final analysis was carried out on <30 species, thus reducing the impact of this approach. Nevertheless, our analysis suggests that the phylogenetic signal alone cannot be a justification for the grouping of species, although biased by the limited set of data available to us. Based on these preliminary findings, we can only hypothesize that brains evolved in cephalopods on the basis of different factors including phylogeny, possible development, and the third factor, i.e., life-style adaptations. Our results support the working hypothesis that the taxon evolved different sensorial and computational strategies to cope with the various environments (niches) occupied in the oceans. This study is novel for invertebrates, to the best of our knowledge.

Macroevolutionary Trade-Offs and Trends in Life History Traits of Cephalopods Through a Comparative Phylogenetic Approach

“…In this comparative study, we evaluated the life history traits of cephalopods considering their phylogenetic relationships, as suggested by Felsenstein (1985). This approach has been scarcely used in comparative studies of cephalopods, and particularly, the assessment of phylogenetic signal has only been conducted in five publications (i.e., Ibáñez et al, 2018Ibáñez et al, , 2019Ibáñez et al, , 2021Anderson and Marian, 2020;Ponte et al, 2021). In this sense, our research is among the few studies correctly addressing trait comparisons for cephalopods, suggesting that further research should incorporate this approach in comparative biology of cephalopods.…”

“…This published phylogeny was selected over other phylogenetic hypotheses (for example, Ibáñez et al, 2021), because it was constructed with the largest number of species, thus, enabling to combine the tree topology and life history traits (BL, EL, and PF). It is worth noting that other authors in the field (e.g., Marian, 2015;Ponte et al, 2021) have also employed the phylogenetic reconstruction published by Lindgren et al (2012) to evaluate macroevolutionary hypotheses of cephalopods according to other traits such as spermatophores and brains. For comparative purposes, all species lacking reproductive data (i.e., EL, PF, Supplementary Table 2) or species determination (21 tree tips, e.g., Bathypolypus sp., Gonatopsis sp., Notonykia sp., Benthoctopus sp.)…”

Cephalopod Behavior: From Neural Plasticity to Consciousness

“…Also evident from these studies are the differences between individuals; as contextual learning progresses, other characteristics of the subjects may become apparent, with inter-individual differences emerging in response (e.g., readiness) to stimuli (Borrelli, 2007 ; Borrelli et al, 2020 ). Of course, it should be noted that differences between species are to be expected, owing to different lifestyles and adaptive capabilities (Nixon and Young, 2003 ; Hanlon and Messenger, 2018 ; Ponte et al, 2021 ).…”

“…Testing Wilson's Behavioral Drive Hypothesis in cephalopods remains an attractive and intriguing idea (Borrelli, 2007 ). Such an approach should necessarily incorporate the relationship between the nervous system and the ecology in which it is embedded (e.g., environment and lifestyle/habits; Ponte et al, 2021 ). It should also consider the computational capacity of the brain - not simply its size.…”

A brain atlas of the camouflaging dwarf cuttlefish,Sepia bandensis

“…The giant cells are located in the ventral magnocellular lobe, and receive input from the optic lobes and statocysts (the cephalopod vestibular system) (Nixon & Young, 2003;Abbott et al, 1995). Second, the brachial, pedal and inferior frontal lobes of octopus are larger than the decapodiformes, which may facilitate their more sophisticated use of arms and tactile learning (Ponte et al, 2020). Third, the octopus vertical lobe is folded into gyri, creating a larger surface area (Young, 1971).…”