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First published online April 23, 2004
Journal of Experimental Biology 207, 1803-1810 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00974

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Control of planula migration by LWamide and RFamide neuropeptides in Hydractinia echinata

Yuki Katsukura^1,*, Hiroshi Ando², Charles N. David³, Cornelis J. P. Grimmelikhuijzen⁴ and Tsutomu Sugiyama^1,

¹ Ishinomaki Senshu University, Ishinomaki 986-8580, Japan
² Hachinohe Institute of Technology, Hachinohe 031-8501, Japan
³ Zoological Institute, University of Munich, 80333 Munich, Germany
⁴ Zoological Institute, Department of Cell Biology, University of Copenhagen, DK-2100 Copenhagen, Denmark

View larger version (8K): [in a new window]   Fig. 1. Planula migration. Images of a single planula larva migrating toward light were captured at the rate of 1 image per 30 s and superimposed to create one figure. Note that the specimen oriented the blunt end of its spindle-shaped body toward light and that contraction and relaxation of tissue along the body axis accompanied migration. The specimen shown was migrating faster (1.2 mm min-1) than average (0.3 mm min-1, see Fig. 5C) thus facilitating visualization of changes in shape and position during migration. Scale bar, 1 mm.

View larger version (8K): [in a new window]   Fig. 2. Migration tracks of planula larvae in (A) normal seawater, (B) seawater containing 10-8 mol l-1 He-LWamide II, or (C) seawater containing 10-7 mol l-1 Hydra-RFamide I. The three tracks shown were obtained from independent experiments, but are shown together to aid comparison. The rectangular box surrounding the tracks represents the spectrophotometer cell with 30 mm light path and 10 mm width that was used as a container to observe planula migration.

View larger version (21K): [in a new window]   Fig. 3. Actogram of migration for planula larva in (A) normal seawater, (B) seawater containing 10-8 mol l-1 He-LWamide II, or (C) seawater containing 10-7 mol l-1 Hydra-RFamide I. The time of observation is plotted against step length (distance moved between two frames: 30 s).

View larger version (15K): [in a new window]   Fig. 4. Effect of He-LWamide II and Hydra-RFamide I on track length. Peptide concentration is plotted against the distance migrated during 1 h (track length). Values shown are means + S.E.M. Asterisks indicate results that are significantly different from the control values (shown in the far-left column in each panel) (t-test; *P<0.05, **0.01). Sample size was minimally 50.

View larger version (23K): [in a new window]   Fig. 5. Effect of various concentrations of He-LWamide II and Hydra-RFamide I on three parameters of migration: the number of active periods per hour (A,D,G), the length of active periods (B,E,H), and the speed of migration during active periods (C,F,I). Asterisks indicate results that are significantly different from the control values (shown in the far-left column in each panel) (t-test; *P<0.05, **0.01). Sample size was minimally 50.