A Possible Pathway Connecting the Photosensitive Pineal Eye to the Swimming Central Pattern Generator in Young Xenopus laevis Tadpoles

1999 ◽  
Vol 54 (6) ◽  
pp. 323-337 ◽  
Author(s):  
David Jamieson ◽  
Alan Roberts
Keyword(s):  
Xenopus Laevis ◽  
Central Pattern Generator ◽  
Pattern Generator

The neuromuscular basis of rhythmic struggling movements in embryos of Xenopus laevis

1982 ◽  
Vol 99 (1) ◽  
pp. 197-205 ◽  
Author(s):  
J. A. Kahn ◽  
A. Roberts
Keyword(s):  
Xenopus Laevis ◽  
Electrical Activity ◽  
Central Pattern Generator ◽  
Large Amplitude ◽  
Motor Nerve ◽  
Sensory Stimulation ◽  
Pattern Generator ◽  
Rhythmic Movements ◽  
Nerve Activity ◽  
Xenopus Embryos

Xenopus embryos struggle when restrained. Struggling involves rhythmic movements of large amplitude, in which waves of bending propagate from the tail to the head. Underlying this, electrical activity in myotomal muscles occurs in rhythmic bursts that alternate on either side of a segment. Bursts in ipsilateral segments occur in a caudo-rostral sequence. Curarized embryos can generate motor nerve activity in a struggling pattern in the absence of rhythmic sensory stimulation; the pattern is therefore produced by a central pattern generator.

Responses of young Xenopus laevis tadpoles to light dimming: possible roles for the pineal eye

2000 ◽  
Vol 203 (12) ◽  
pp. 1857-1867 ◽  
Author(s):  
D. Jamieson ◽  
A. Roberts
Keyword(s):  
Xenopus Laevis ◽  
Water Column ◽  
Central Pattern Generator ◽  
Water Surface ◽  
Pattern Generator ◽  
Cement Gland ◽  
Solid Objects ◽  
Floating Objects ◽  
Behavioural Significance

When the light is dimmed, the pineal eye of hatchling Xenopus laevis tadpoles excites the central pattern generator for swimming, but the behavioural significance of pineal excitation is unclear. We show that tadpoles spend 99 % of their time hanging from the surface meniscus or solid objects using mucus secreted by a cement gland on the head. Attachment inhibits swimming, but unattached tadpoles swim spontaneously. Provided that their pineal eye is intact, they attach closer to the water surface in the dark than in the light and attach preferentially to the underside of floating objects that cast shadows. Dimming causes tadpoles swimming horizontally to turn upwards and is very effective in initiating upward swimming in unattached tadpoles. Similar pineal-dependent responses during swimming are present up to stage 44. Pinealectomy blocks responses to dimming at all stages. Recordings from immobilised tadpoles reveal that light dimming induces faster fictive swimming and that pineal activity is increased for up to 20 min during sustained light dimming. We suggest that the increase in pineal discharge during dimming increases the probability of upward swimming and, in this way, increases the probability of tadpoles attaching to objects higher in the water column that cast shadows.

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