Ontogenetic and Experience-Dependent Changes in Defensive Behavior in Captive-Bred Hawaiian Bobtail Squid, Euprymna scolopes

Evaluation of Candidates for Systemic Analgesia and General Anesthesia in the Emerging Model Cephalopod, Euprymna berryi

Cephalopods' remarkable behavior and complex neurobiology make them valuable comparative model organisms, but studies aimed at enhancing welfare of captive cephalopods remain uncommon. Increasing regulation of cephalopods in research laboratories has resulted in growing interest in welfare-oriented refinements, including analgesia and anesthesia. Although general and local anesthesia in cephalopods have received limited prior study, there have been no studies of systemic analgesics in cephalopods to date. Here we show that analgesics from several different drug classes may be effective in E. berryi. Buprenorphine, ketorolac and dexmedetomidine, at doses similar to those used in fish, showed promising effects on baseline nociceptive thresholds, excitability of peripheral sensory nerves, and on behavioral responses to transient noxious stimulation. We found no evidence of positive effects of acetaminophen or ketamine administered at doses that are effective in vertebrates. Bioinformatic analyses suggested conserved candidate receptors for dexmedetomidine and ketorolac, but not buprenorphine. We also show that rapid general immersion anesthesia using a mix of MgCl2 and ethanol was successful in E. berryi at multiple age classes, similar to findings in other cephalopods. These data indicate that systemic analgesia and general anesthesia in Euprymna berryi are achievable welfare enhancing interventions, but further study and refinement is warranted.

Age-dependent genetic variation in aggression

Understanding the extent to which behavioural variance is underlain by genotypic, environmental and genotype-by-environment effects is important for predicting how behavioural traits might respond to selection and evolve. How behaviour varies both within and among individuals can change across ontogeny, leading to differences in the relative contribution of genetic and environmental effects to phenotypic variation across ages. We investigated among-individual and among-genotype variation in aggression across ontogeny by measuring, twice as juveniles and twice as adults, both approaches and attacks against a three-dimensional-printed model opponent in eight individuals from each of eight genotypes (N = 64). Aggression was only significantly repeatable and heritabile in juveniles. Additionally, how aggression changed between juvenile and adult life-history stages varied significantly among individuals and genotypes. These results suggest that juvenile aggression is likely to evolve more rapidly via natural selection than adult aggression and that the trajectory of behavioural change across the lifespan has the potential to evolve. Determining when genetic variation explains (or does not explain) behavioural variation can further our understanding of key life-history stages during which selection might drive the strongest or swiftest evolutionary response.

Environmental estrogen exposure disrupts sensory processing and nociceptive plasticity in the cephalopod Euprymna scolopes

Endogenous estrogens affect multiple sensory systems, including those involved in processing noxious and painful stimuli. Extensive evidence demonstrates that estrogenic environmental pollutants have profound, negative effects on growth and reproductive physiology, but there is limited information about how estrogenic pollutants might affect sensory systems known to be modulated by endogenous estrogens. Here, we show that ethinyl estradiol, the most common artificial estrogen found in coastal marine environments, disrupts normal behavioral and neural responses to tissue injury in the sepiolid Euprymna scolopes (Hawaiian bobtail squid), which inhabits shallow tropical waters close to dense human habitation. Behavioral hypersensitivity and neural plasticity that occur normally after tissue injury were impaired both under chronic estrogen exposure beginning during embryogenesis and after a single, high dose co-incident with injury. This suggests that these naturally selected responses to injury, which function to protect animals from predation and infection risk, may be impaired by anthropogenic pollution.

Cephalopod Biology: At the Intersection Between Genomic and Organismal Novelties

Cephalopods are resourceful marine predators that have fascinated generations of researchers as well as the public owing to their advanced behavior, complex nervous system, and significance in evolutionary studies. Recent advances in genomics have accelerated the pace of cephalopod research. Many traditional areas focusing on evolution, development, behavior, and neurobiology, primarily on the morphological level, are now transitioning to molecular approaches. This review addresses the recent progress and impact of genomic and other molecular resources on research in cephalopods. We outline several key directions in which significant progress in cephalopod research is expected and discuss its impact on our understanding of the genetic background behind cephalopod biology and beyond.

Early-life injury produces lifelong neural hyperexcitability, cognitive deficit and altered defensive behaviour in the squid Euprymna scolopes

Injury occurring in the neonatal period in mammals is known to induce plasticity in pain pathways that may lead to pain dysfunction in later life. Whether these effects are unique to the mammalian nervous system is not well understood. Here, we investigate whether similar effects of early-life injury are found in a large-brained comparative model, the cephalopod Euprymna scolopes. We show that the peripheral nervous system of E. scolopes undergoes profound and permanent plasticity after injury of peripheral tissue in the early post-hatching period, but not after the same injury given in the later juvenile period. Additionally, both innate defensive behaviour and learning are impaired by injury in early life. We suggest that these similar patterns of nervous system and behavioural remodelling that occur in squid and in mammals indicate an adaptive value for long-lasting plasticity arising from early-life injury, and suggest that injuries inflicted in very early life may signal to the nervous system that the environment is highly dangerous. Thus, neonatal pain plasticity may be a conserved pattern whose purpose is to set the developing nervous system's baseline responsiveness to threat. This article is part of the Theo Murphy meeting issue 'Evolution of mechanisms and behaviour important for pain'.