Sense and Insensibility – An Appraisal of the Effects of Clinical Anesthetics on Gastropod and Cephalopod Molluscs as a Step to Improved Welfare of Cephalopods

Abstract

Recent progress in animal welfare legislation stresses the need to treat cephalopod molluscs, such as Octopus vulgaris, humanely, to have regard for their wellbeing and to reduce their pain and suffering resulting from experimental procedures. Thus, appropriate measures for their sedation and analgesia are being introduced. Clinical anesthetics are renowned for their ability to produce unconsciousness in vertebrate species, but their exact mechanisms of action still elude investigators. In vertebrates it can prove difficult to specify the differences of response of particular neuron types given the multiplicity of neurons in the CNS. However, gastropod molluscs such as Aplysia, Lymnaea, or Helix, with their large uniquely identifiable nerve cells, make studies on the cellular, subcellular, network and behavioral actions of anesthetics much more feasible, particularly as identified cells may also be studied in culture, isolated from the rest of the nervous system. To date, the sorts of study outlined above have never been performed on cephalopods in the same way as on gastropods. However, criteria previously applied to gastropods and vertebrates have proved successful in developing a method for humanely anesthetizing Octopus with clinical doses of isoflurane, i.e., changes in respiratory rate, color pattern and withdrawal responses. However, in the long term, further refinements will be needed, including recordings from the CNS of intact animals in the presence of a variety of different anesthetic agents and their adjuvants. Clues as to their likely responsiveness to other appropriate anesthetic agents and muscle relaxants can be gained from background studies on gastropods such as Lymnaea, given their evolutionary history.

Short and Long-Term Effects of Anesthesia in Octopus maya (Cephalopoda, Octopodidae) Juveniles

“…Nonetheless, similarly to ethanol, stressful reactions and inking were eventually noted ( Garcia-Franco, 1992 ). Controversial opinions whether magnesium chloride produces adequate general anesthesia or simply act as neuromuscular blocking agent are discussed in the literature ( Andrews et al, 2013 ; Polese et al, 2014 ; Fiorito et al, 2015 ; Butler-Struben et al, 2018 ; Winlow et al, 2018 ), however, no consensus is completely achieved to date.…”

“…Cold sea water (commonly also referred as hypothermia) as anesthetic agent has the advantage of avoiding the use of chemicals (and potential associated negative effects) ( Gleadall, 2013b ) and, despite the popularity of use in the past, its anesthetic properties are questionable ( Andrews and Tansey, 1981 ; Gleadall, 2013b ; Fiorito et al, 2015 ; Winlow et al, 2018 ). Muscle relaxation is usually reported to lack in animals exposed to cold sea water (e.g., Andrews and Tansey, 1981 ).…”

“…Another relevant factor to be considered for anesthetic selection, are the induction and recovery times. Anesthesia should have rapid action, with stress reactions and hyperactivity, reduced to a minimum; similarly, recovery should not last long and none or minimum side-effects are desirable ( Winlow et al, 2018 ). For fishes, recommended times of induction and recovery should be preferably not longer than 3 and 5 min, respectively ( Ross and Ross, 2008 ).…”

Comparison of embryonic and adult shells of Sepia officinalis (Cephalopoda, Mollusca)

“…officinalis eggs were collected in Luc-sur-Mer (Normandie, France) and kept in the lab in artificial sea water (salinity: 35 ppt -closed circulatory system), at 18°C. Eggs were opened and the embryos (whose stage is determined by morphological characteristics) were immerged in sea-water with 5% Ethanol, following recommendations of Buttler-Struben et al 2018and Winlow et al (2018) and according to directive 2010-63-UE and French decree 2013-118.…”

Octopus maya white body show sex-specific transcriptomic profiles during the reproductive phase, with high differentiation in signaling pathways

“…In this study, octopuses were anesthetized with ethanol 3% in sea water at experimental temperatures [22,23] to enable humane killing [24] in consideration of ethical protocols [25], and the animals’ welfare during manipulations [26,27]. Our protocols were approved by the experimental Animal Ethics Committee of the Faculty of Chemistry at Universidad Nacional Autónoma de México (Permit number: Oficio/FQ/CICUAL/099/15).…”