Schnell Alexandra K.

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Schnell
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Alexandra K.
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  • Article
    Lateralization of eye use in cuttlefish : opposite direction for anti-predatory and predatory behaviors
    (Frontiers Media, 2016-12-12) Schnell, Alexandra K. ; Hanlon, Roger T. ; Benkada, Aïcha ; jozet-alves, christelle
    Vertebrates with laterally placed eyes typically exhibit preferential eye use for ecological activities such as scanning for predators or prey. Processing visual information predominately through the left or right visual field has been associated with specialized function of the left and right brain. Lateralized vertebrates often share a general pattern of lateralized brain function at the population level, whereby the left hemisphere controls routine behaviors and the right hemisphere controls emergency responses. Recent studies have shown evidence of preferential eye use in some invertebrates, but whether the visual fields are predominately associated with specific ecological activities remains untested. We used the European common cuttlefish, Sepia officinalis, to investigate whether the visual field they use is the same, or different, during anti-predatory, and predatory behavior. To test for lateralization of anti-predatory behavior, individual cuttlefish were placed in a new environment with opaque walls, thereby obliging them to choose which eye to orient away from the opaque wall to scan for potential predators (i.e., vigilant scanning). To test for lateralization of predatory behavior, individual cuttlefish were placed in the apex of an isosceles triangular arena and presented with two shrimp in opposite vertexes, thus requiring the cuttlefish to choose between attacking a prey item to the left or to the right of them. Cuttlefish were significantly more likely to favor the left visual field to scan for potential predators and the right visual field for prey attack. Moreover, individual cuttlefish that were leftward directed for vigilant scanning were predominately rightward directed for prey attack. Lateralized individuals also showed faster decision-making when presented with prey simultaneously. Cuttlefish appear to have opposite directions of lateralization for anti-predatory and predatory behavior, suggesting that there is functional specialization of each optic lobe (i.e., brain structures implicated in visual processing). These results are discussed in relation to the role of lateralized brain function and the evolution of population level lateralization.
  • Article
    Dramatic fighting by male cuttlefish for a female mate
    (University of Chicago Press, 2017-05-02) Allen, Justine J. ; Akkaynak, Derya ; Schnell, Alexandra K. ; Hanlon, Roger T.
    Male cuttlefish compete for females with a repertoire of visually dramatic behaviors. Laboratory experiments have explored this system in Sepia officinalis, but corroborative field data have eluded collection attempts by many researchers. While scuba diving in Turkey, we fortuitously filmed an intense sequence of consort/intruder behaviors in which the consort lost and then regained his female mate from the intruder. These agonistic bouts escalated in stages, leading to fast dramatic expression of the elaborate intense zebra display and culminating in biting and inking as the intruder male attempted a forced copulation of the female. When analyzed in the context of game theory, the patterns of fighting behavior were more consistent with mutual assessment than self-assessment of fighting ability. Additional observations of these behaviors in nature are needed to conclusively determine which models best represent conflict resolution, but our field observations agree with laboratory findings and provide a valuable perspective.
  • Preprint
    Giant Australian cuttlefish use mutual assessment to resolve male-male contests
    ( 2015-05) Schnell, Alexandra K. ; Smith, Carolynn L. ; Hanlon, Roger T. ; Harcourt, Robert
    Game theory models provide a useful framework for investigating strategies of conflict resolution in animal contests. Model predictions are based on estimates of resource-holding potential (RHP) and vary in their assumptions about how opponents gather information about RHP. Models can be divided into self-assessment strategies (energetic war-of-attrition, E-WOA; cumulative assessment model, CAM) and mutual assessment strategies (sequential assessment model, SAM). We used laboratory-staged contests between male giant Australian cuttlefish, Sepia apama, to evaluate RHP traits and to test game theory models. Mantle length was a key indicator of RHP because it predicted contest outcome, whereby larger individuals were more likely to win a contest. Winners and losers did not match behaviours, ruling out the E-WOA. There was no relationship between contest outcome, duration and escalation rates, arguing against the CAM. Persistence to continue a contest was based on RHP asymmetry, rather than loser and/or winner RHP, providing support for the SAM. Motivation to fight was determined from a male’s latency to resume a contest following the introduction of a female during a contest. The latency to resume a contest was negatively related to the size of the focal male and positively related to the size of their opponent. These results show that competing males are able to gather information concerning RHP asymmetries, providing support for mutual assessment. Furthermore, males showed significant behavioural differences in their responses to relatively larger than to relatively smaller opponents. Using an integrative approach, our study provides a well-substantiated example of mutual assessment.