Table 1
Description of tested planarias
| body length at t 0 (in mm) | |||
|---|---|---|---|
| species | family | range | average ± std error |
| Dugesia (= Schmidtea) polychroa | Dugesiidae | 5.5-10.0 | 7.8 ± 0.4 |
| Dugesia (= Girardia) tigrina | Dugesiidae | 5.2-9.5 | 6.7 ± 0.3 |
| Polycelis tenuis | Planariidae | 5.2-8.1 | 6.4 ± 0.2 |
The three species of planarias investigated, listed alphabetically. All species belong to the infraorder Paludicola (free-living freshwater planarias). Body length refers to the individuals used in the experiment; n = 12 for all.
Figure 1
Diel cycles in light irradiance and planarian activity. Light irradiance (top panel; average ± standard error; n = 10 for each time period) and average planarian individual activity (bottom three panels; average ± standard error; n = 12 for each time period) during the 24-h observation cycles, with observations carried out every 3 h starting at midnight on d1. Full daylight times are in yellow, nighttime hours in blue, and twilight hours in purple. Lower-case letters identify significantly different average values according to SNK tests (p ≤ 0.05) performed after significant one-way, type I ANOVAs on original (FD.polychroa = 5.746, p < 0.001; FD.tigrina = 42.766, p < 0.001; FP.tenuis = 2.041, p = 0.06; df = 7,88 for all) or log-transformed data (Flight = 278.783, p < 0.001, df = 7,72).
Table 2
Relationship between light and activity
| species | r 2 | p | type | trend |
|---|---|---|---|---|
| D. polychroa | 0.005 | 0.87 | lin | - |
| D. tigrina | 0.653 | <0.01 | log | - |
| P. tenuis | 0.0003 | 0.97 | lin | + |
Correlations between diel light irradiance and planarian activity, using the values reported in Figure 1 (n = 8 and df = 6 for each correlation). Best fitting correlations are reported for each species; lin = linear and log = logarithmic relationships; positive and negative trends are reported as "+" and "-", respectively.
Table 3
Across-species differences in activity
| time of observation | ANOVA | SNK separation | |||
|---|---|---|---|---|---|
| F | p | D. polychroa | D. tigrina | P. tenuis | |
| 0:00 | 7.665 | <0.01 | b | b | a |
| 3:00 | 5.499 | <0.01 | b | b | a |
| 6:00 | 0.790 | 0.51 | - - - test not performed - - - | ||
| 9:00 | 3.471 | 0.03 | b | a | b |
| 12:00 | 3.702 | 0.02 | b | a | ab |
| 15:00 | 6.920 | <0.01 | b | a | a |
| 18:00 | 3.630 | 0.02 | b | a | ab |
| 21:00 | 22.883 | <0.01 | b | c | a |
Across-species differences in activity (based on the data presented in Figure 1) according to one-way ANOVAs (df = 3,33 for all) coupled with SNK tests at p ≤ 0.05. Different letters identify SNK-based statistically different average activity, listed alphabetically (a = lowest value).
Figure 2
Daily peaks in planarian activity. Daily peak activity times for the three species examined, calculated as average angular-transformed hourly data. The angular concentration (rc), an inverse measure of individual variability, also is given. Pooled standard error, used to separate significantly different averages [49], was not calculated because species-specific daily peak activity times were not statistically separated (second-order Hotelling test: F = 1.407, p = 0.185).
Figure 3
Planarian activity following food inputs. Occurrence in active mode (as % of total number of individuals; average ± standard error) just before (13:00 or 1:00), at 5-min intervals for the first 30 min, and 1 h after daytime (left panels, in yellow) and nighttime food addition (right panels, in blue), for the three species examined. Lower-case letters identify significantly different average values according to SNK tests (p ≤ 0.05) performed after significant one-way, type I ANOVAs (D. polychroa: Fday = 4.509, p < 0.001; Fnight = 2.368, p = 0.02; D. tigrina: Fday = 3.734, p < 0.01; Fnight = 4.316, p < 0.001; P. tenuis: Fday = 0.616, p = 0.74; Fnight = 0.304, p = 0.95; df = 7,88 for all).