Friday Cephalopod: Why are some cephalopods so clever?

I’m just ruined for some things. Here’s this article that’s smack dab in my wheelhouse: Grow Smart and Die Young: Why Did Cephalopods Evolve Intelligence? It’s a topic I’m very interested in, but the article fell flat for me. I’m going to be a bit nit-picky here.

The good part of the story is that it’s a review of various hypotheses for the evolution of intelligence in various clades. They propose 3 general classes of hypotheses.

  1. The Ecological Intelligence hypothesis. Intelligence arose in response to food foraging challenges. You’ve got to have a detailed knowledge of your environment in order to take advantage of scarce or difficult to extract food sources.
  2. The Social Intelligence hypothesis. Animals with complex social interactions build complex brains to match.
  3. The Predator/Prey hypothesis. Avoiding predation in some organisms might require an intelligence comparable to that required to negotiate social interactions.

Not mentioned is an alternative sort-of null hypothesis: there was no selection for intelligence at all. It hitch-hiked along with an expansion of neural tissue associated with morphological changes — intelligence is something that just emerges with a surplus of brains that arose for other reasons.

OK. With my addition, I think this is a reasonable framework for discussing the evolution of intelligence. Unfortunately, the paper has a couple of problems. One is that, well, it’s a review paper that doesn’t have any data or experiments or even any real evidence. It’s speculative, which is fine, but I went into it with higher expectations.

The one piece of information I found useful, though, was this table, which gathers together information about groups of animals with a reputation for intelligence and puts them in a comparative context. That’s what I like to see!

But. Here’s what bugs me: it’s comparing a whole taxonomic class, the cephalopods, with a couple of families. The cephalopods are diverse, with some impressively intelligent representatives, like the octopus. But market squid? Are they particularly bright? I don’t think so. We could say the same of primates — are we really going to compare Galago with Homo? This table would have benefited from a much tighter focus.

It also leaves out some features unique to various groups. Can we compare complex active camouflage with complex language? It seems to me that maybe there are different preconditions that can lead to intelligence, and maybe an illustration of the significant differences between them would be more informative? There could be many, radically different paths that lead to increased demands for more flexibility and intelligence — maybe all three of their hypotheses, and more, are all true.

For instance, look at the last rows of the table, on life history. That part is really interesting, and the paper does discuss it at length. Some cephalopods are intelligent creatures that are cruelly cursed by their nature with very short lifespans of 1 or 2 years, where reproduction is often a death sentence, and the opportunity to educate offspring is non-existent. What intelligence they do have has to be inherent, because there is so little opportunity for learning.

Also compare social lives. Cephalopods, depending on the species, are either solitary or live in large schools, and do not seem to form long-term social bonds; the vertebrates on the list are all social to various degrees, and do pair-bond. After reading the paper, I came away thinking that I mainly saw diversity and different forces that could all lead to intelligence, and don’t have much unity of mechanisms. There is at least a nice summary of cephalopod evolution.

Around 530 Mya a group of snail-like molluscs experienced a major shift in their morphology and physiology: their protective shell became a buoyancy device. The comparison with nautiluses, the only extant cephalopods that retained the external shell, suggests that this key event co-occurred with the emergence of arms, funnel, and crucially, a centralized brain. The increase in computational power at this stage might have been selected to support arm coordination for locomotion and object manipulation, as well as navigation in the water column and basic learning processes. Next, around 275 Mya the external shell was internalised (in the ancestors of cuttlefish and squid) or lost (in those of octopuses). It has been speculated that competition with marine vertebrates was a driving factor that led to dramatic changes in the lifestyles of these animals. First, the disappearance of the external shell allowed animals to occupy a wide array of ecological niches. Consequently, modern cephalopods are found in all marine habitats, from tropical to polar waters, and from benthic to pelagic niches. Second, the loss of the protective shell drastically increased predatory pressures and consequently the rates of extrinsic mortality. These novel ecological conditions might not have only played a major role in the emergence of sophisticated biological adaptations (e.g., lens eye, and chromatophores) but also in the coevolution of intelligence and fast life history of cephalopods.

Maybe intelligence is something that just arises in response to complex life strategies, where “complex” is an all-purpose buzzword for any of a million situations. If we ever meet aliens on a distant planet, this tells me you’d be unwise to try and predict what they’d look like or how they live or what the mechanisms behind their intelligence might be.

Friday Cephalopod: They’re going to outbreed us!

Here they come, the legions of cephalopods. Massive aggregations of brooding octopuses were found near Monterey Bay.

That’s not all. The University of Georgia had a single octopus in their aquarium, Octavius, presumed male, until they discovered a surprise one morning.

“I noticed this cloud of moving dots and I realised, ‘Oh my God, she had babies. There are babies. There are babies everywhere.’ And a sort of panic ensued,” aquarium curator Devin Dumont told Mary Landers at Savannah Now.

“I immediately started scooping them out and putting them in buckets and there were just buckets and buckets and buckets full of tiny octopi.”

Finding a tank full of baby octopuses (or octopodes for language pedants) would certainly be enough to shock anybody into mixing up their Greek and Latin word roots.

I, for one, welcome our breeding swarms of transgender octopuses, and will greet them as saviors when they emerge to release humanity from its misery.

Friday Cephalopod: The Ecstasy Protocol

The story of this experiment where octopuses were given a hit of Ecstasy (MDMA) is all over the interwebs right now, but not very many people have bothered to read the original paper, given the weird twist it’s been given, that these bored scientists were giving their pets drugs to see what they’d do. That isn’t the case at all. The first part of the paper is all about sequence analysis of the serotonin transporter gene SLC6A4 (the gene that is affected by MDMA), and a comparison of the gene in different phyla. This research starts with some serious, detailed work on the functional mechanics of the gene. If you want to study the role of serotonin in mood and behavior in humans, comparative work of this sort is essential if you want to puzzle out which bits and pieces of the gene are important.

The starting point of this work is the phylogeny, which tells us that serotonin is an ancient transmitter, and that many of the elements of its signaling process are evolutionarily conserved. It should also tell you that its history is complicated, because there are a lot of duplications and subtle variants.

(A and B) Maximum-likelihood trees of SLC6A transporters (A) and SLC6A4 serotonin transporters (B) in select taxa. Species are mapped to tree and protein identifiers in Table S3. For a larger version of (A), see Figure S1.
(A) A maximum-likelihood “best tree” for the SLC6A gene family. The maximum-likelihood tree produced by RAxML includes 503 proteins and 21 species, with tree building based on a MAFFT alignment of full-length sequences.
(B) The SLC6A4 gene family, a subtree of the maximum-likelihood “best tree” in (A).

Thus, monoamine transporters may represent an ancient innovation that arose early in bilaterian evolution, with various ancient and more recent duplications in different lineages.

We know, though, from the molecular work that the octopus has an SLC6A4 gene, and further, that the portion of the gene that binds to MDMA has been conserved. The next question, then, is to ask how this gene modulates octopus behavior. That’s when the test of exposing them to MDMA was proposed.

Of course, you don’t just give animals the drug and watch to see what happens. You’ve got to have a hypothesis. In this case, prior observations, much of it informal, in a different model system, Homo sapiens, was used to infer that MDMA exposure might increase social behavior (“I love you, man”), so they designed an experimental setup to directly test that behavior. Here it is.

(A and B) Diagrams illustrating timeline (A) and experimental protocol (B) for three-chambered social approach assay.
(C) Quantification of time spent in each chamber during 30-min test sessions (n = 4; two-way repeated-measures ANOVA: p = 0.0157; post hoc unpaired t test pre, social versus center p = 0.4301, object versus center p = 0.0175; post, social versus center p = 0.0190, object versus center p = 0.1781).
(D–K) Comparisons between pre- versus post-MDMA-treatment conditions (paired t test pre versus post, social time p = 0.0274; object time p = 0.1139; center time p = 0.7658; transitions p = 0.3993).
(L) Photograph of social interaction under the saline (pre) condition.
(M) Photograph of social interaction under the MDMA (post) condition.
Error bars represent the SEM.

The design is straightforward: since you can’t ask an octopus to explain the sensations they feel under MDMA, you give them a choice. They have a 3-chambered box, and they put the octopus they were testing in the center box. On the left, there is an object, a toy they can explore. On the right, there is another octopus, an opportunity to socialize. Will they prefer an inanimate object they can tinker with, or to approach a conspecific?

In observations without any drugs, they determined that, as expected, octopuses are relatively solitary animals — in part because nobody likes the males. Both male and female subjects spent most of their time in the central chamber, but would spend more time in the social chamber if the octopus there was a female, but if it was male, they were suddenly much more interested in hanging out with the object.

Nevertheless, somewhat surprisingly, both male and female subjects did exhibit social approach to a novel female conspecific, a finding that may reflect an adaptation of laboratory raised animals or an incomplete ethological description of the full repertoire of social behaviors in the wild. Although we cannot rule out the possibility that the female versus male social object preference effect is governed by relative size differences between subject and social objects, we think this is unlikely since we observed aversion to a male social object both when the subject was greater and smaller in size.

I’m just going to assume that the male aversion was because males are assholes, which is apparently a phylogenetically ancient trait.

What they clearly saw, though, was that under the influence of MDMA, the subject octopus switched to expressing a far greater interest in exploring the social object, whether it was a male or female. The animals responded to the entactogenic properties of the drug, an interesting observation that suggests that this is also a phylogenetically ancient trait.

A word of caution, in interpreting these data: there has been a tendency lately to cherry-pick examples of complex animal behavior to justify specific human social structures. What this work tells us is that there are conserved biochemical pathways that are regulated to trigger behaviors along a continuum — that diverse animals use serotinergic pathways as a kind of slider control, that can be ramped up to increase cooperative, social behavior, or tuned down to increase aggressive, asocial behavior. That this kind of neural regulative control exists, is conserved, and has deep roots in animal evolution cannot be used to argue that humans are naturally supposed to build capitalist dominance hierarchies any more than it can be used to claim that humans are adapted to live in cooperative communes full of peace, love, and understanding. The pathway is present in animals with diverse behavioral patterns.

Monoamine transporters, including human SERT, DAT, and NET, appear to be a bilaterian innovation, suggesting a possible ancient evolutionary role in nervous system centralization and elaboration, both hallmarks of the Bilateria, and the families have undergone complex patterns of gene duplication and loss throughout the clade over time. Phylogenetic analysis revealed clear orthologs of human SLC6A4 in octopuses, as well as high levels of conservation in the transmembrane domain and amino acid region critical to MDMA binding. Interestingly, we found that SLC6A4 is broadly conserved in the fruit fly, the worm, and most other bilaterian animals but is surprisingly absent in both of the eusocial hymenopteran insects, the honeybee and leaf cutter ant.

I’m sure that warning won’t stop everyone, though. I also expect that there will be some humans using it to argue that we all ought to be taking more E, a position that the research does not endorse at all, either.

One last thing I want to mention is a bit from the methods section (yeah, I read the methods): cephalopods are completely exempt from the ethical regulations for the care of laboratory animals, but the investigators followed them anyway.

Care of invertebrates, like O. bimaculoides, does not fall under United States Animal Welfare Act regulation, and is omitted from the PHS-NIH “Guide for the Care and Use of Laboratory Animals.” Thus, an Institutional Animal Care and Use Committee, a Committee on Ethics for Animal Experiments, or other granting authority does not formally review and approve experimental procedures on and care of invertebrate species, like O. bimaculoides, at the Marine Biological Laboratory. However, in accordance with Marine Biological Laboratory Institutional Animal Care and Use Committee guidelines for invertebrates, our care and use of O. bimaculoides at the Marine Biological Laboratory and at Johns Hopkins University generally followed tenets prescribed by the Animal Welfare Act, including the three ‘Rs’ (refining, replacing, and reducing unnecessary animal research).

You can’t punch a kitten with a meat hammer, but you can do it to an octopus, if you want, which seems backwards to me. No! I mean, you shouldn’t be allowed to punch any animal with a meat hammer in the name of science. But once again, our laws are inconsistent and arbitrary.