Flow sensing behaviors of Xenopus laevis are stable across metamorphosis
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1
Brown University, Cognitive, Linguistic & Psychological Sciences, United States
A series of behavioral experiments was conducted to analyze flow sensing abilities over the course of development in the African clawed frog, Xenopus laevis. Animals’ movements, swimming speed, and orientation were analyzed in a flow tank, in which flow speed and flow dynamics could be manipulated. Behavioral responses, including rheotaxis, positioning, and station holding, were quantified to a range of flow speeds and at three developmental groups: young larvae at stages 48-55, metamorphic climax tadpoles at stages 57-66, and froglets 2 days to 8 weeks post-metamorphosis. All animals were tested in the dark, under no-flow (control) and flow (at variable flow rates) conditions. Data show that Xenopus laevis exhibits consistent positive rheotaxis across larval development and into the early post-metamorphic period. Strength of the rheotactic response did not vary with flow rate above a threshold for response. These results confirm those reported in an earlier study (Simmons et al. 2004) using a different flow field and testing low flow speeds only. Under conditions of flow challenge (strong current speeds), animals moved downstream away from the flow source, but then still turned into the flow to maintain positive orientation. Thus, position along the flow axis varied slightly with flow speed. Still, once an animal adopted a position in flow, it tended to maintain that position over the entire flow period. Observations of swimming behaviors suggests that downstream movements were active and directed, and not simply the result of passive push by the current. For tadpoles, flow also triggered downward movement towards the bottom of the tank (in the direction of decreasing water depth), and thus, they no longer suspended in the water column as they do in no-flow conditions. Thigmotactic behavior did not vary with flow speed. Visual cues, produced by a light source positioned either upstream or downstream, were ineffective in overriding positive rheotaxis to the current. At all ages, animals avoided areas of the tank where visual cues were available. These data suggest that positive rheotaxis is not appreciably influenced by visual cues. DASPEI and FM1-43 staining showed that the lateral line neuromasts changed in distribution between early larval and metamorphic climax stages; however, these anatomical changes were not related to the threshold or strength of rheotaxis. These data suggest that orientation to the current source is a biologically important behavior for Xenopus across development.
Acknowledgements
Funded by the Rhode Island Space Grant (NASA) to AMS and by a Research at Brown award to TTV.
References
Simmons AM, Costa LM, Gerstein H (2004). Lateral line-mediated rheotactic behavior in tadpoles of the African clawed frog, Xenopus laevis. Journal of Comparative Physiology A190:747-758.
Keywords:
flow sensing,
rheotaxis,
tadpole,
Xenopus
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster (but consider for student poster award)
Topic:
Sensory: Mechanosensation
Citation:
Lovato
AK,
Vu
TT and
Simmons
AM
(2012). Flow sensing behaviors of Xenopus laevis are stable across metamorphosis.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00003
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Received:
25 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Prof. Andrea M Simmons, Brown University, Cognitive, Linguistic & Psychological Sciences, Providence, Rhode Island, 02912, United States, Andrea_Simmons@brown.edu