Limits...
Fine-scale differences in diel activity among nocturnal freshwater planarias (Platyhelminthes: Tricladida).

Lombardo P, Giustini M, Miccoli FP, Cicolani B - J Circadian Rhythms (2011)

Bottom Line: Food was provided every 36 h, resulting in alternating day- and nighttime feeding events.The fine-scale differences in diel behavior among these three triclad species may not be sufficient to allow coexistence in the wild, with the nonnative D. tigrina eventually displacing D. polychroa and P. tenuis in many European waters.The link between planarian diel rhythms and ecological characteristics are worth of further, detailed investigation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Environmental Sciences - "Marco Giustini" Ecology Lab, Coppito Science Center, University of L'Aquila, I-67100 L'Aquila, Italy. physa@tiscali.it.

ABSTRACT

Background: Although most freshwater planarias are well known photonegative organisms, their diel rhythms have never been quantified. Differences in daily activity rhythms may be particularly important for temperate-climate, freshwater planarias, which tend to overlap considerably in spatial distribution and trophic requirements.

Methods: Activity of stress-free, individually tested young adults of three common planarian species was recorded at 3-h intervals in a 10-d experiment under natural sunlight and photoperiod during autumnal equinox (D:L ~12:12). Individual activity status was averaged over the 10-d experiment, each tested individual thus serving as a true replicate. Twelve individuals per species were tested. Food was provided every 36 h, resulting in alternating day- and nighttime feeding events. Activity during the first post-feeding h was recorded and analyzed separately. Statistical procedures included ANOVAs, correlations, and second-order analyses of angles.

Results: Dugesia (= Girardia) tigrina Girard 1850 exhibited clear nocturnal behavior, Dugesia (= Schmidtea) polychroa Schmidt 1861 was predominantly but not exclusively nocturnal, and Polycelis tenuis Ijima 1884 was relatively more active from midnight through noon. Species-specific activity peaks were statistically similar, with peaks at dawn for P. tenuis and just before midnight for the two dugesiids; however, D. tigrina was comparatively more active in the early night hours, while D. polychroa was more active than D. tigrina during daytime. D. tigrina also responded less readily to daytime food addition. P. tenuis remained poorly active and unresponsive throughout the experiment. Individual variability in diel behavior was highest for D. polychroa and lowest for D. tigrina. P. tenuis's general low degree of activity and late activity peak in the experiment may be related to a strong reliance on external stimuli.

Conclusions: The tested species are mainly nocturnal, consistent with their photonegative characteristics. The fine-scale differences in diel behavior among these three triclad species may not be sufficient to allow coexistence in the wild, with the nonnative D. tigrina eventually displacing D. polychroa and P. tenuis in many European waters. The link between planarian diel rhythms and ecological characteristics are worth of further, detailed investigation.

No MeSH data available.


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).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3094315&req=5

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).

Mentions: Food addition was associated with an increase in the level of activity for the two dugesiids, but not for P. tenuis (SNK separation in Figure 3). Significantly more dugesiid individuals had become active than inactive by 5-15 minutes after nighttime food addition (paired activity-vs.-inactivity t-tests [50]; results not shown). Daytime food addition was associated with a significant increase in activity only for D. polychroa, while D. tigrina remained significantly inactive as a population (paired t-tests; results not shown). P. tenuis remained significantly inactive throughout the food addition events regardless of time of day, while D. polychroa and D. tigrina remained significantly more active than pre-feeding conditions 1 h after food addition (SNK separation in Figure 3; incomplete for D. polychroa at night).


Fine-scale differences in diel activity among nocturnal freshwater planarias (Platyhelminthes: Tricladida).

Lombardo P, Giustini M, Miccoli FP, Cicolani B - J Circadian Rhythms (2011)

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).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3094315&req=5

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).
Mentions: Food addition was associated with an increase in the level of activity for the two dugesiids, but not for P. tenuis (SNK separation in Figure 3). Significantly more dugesiid individuals had become active than inactive by 5-15 minutes after nighttime food addition (paired activity-vs.-inactivity t-tests [50]; results not shown). Daytime food addition was associated with a significant increase in activity only for D. polychroa, while D. tigrina remained significantly inactive as a population (paired t-tests; results not shown). P. tenuis remained significantly inactive throughout the food addition events regardless of time of day, while D. polychroa and D. tigrina remained significantly more active than pre-feeding conditions 1 h after food addition (SNK separation in Figure 3; incomplete for D. polychroa at night).

Bottom Line: Food was provided every 36 h, resulting in alternating day- and nighttime feeding events.The fine-scale differences in diel behavior among these three triclad species may not be sufficient to allow coexistence in the wild, with the nonnative D. tigrina eventually displacing D. polychroa and P. tenuis in many European waters.The link between planarian diel rhythms and ecological characteristics are worth of further, detailed investigation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Environmental Sciences - "Marco Giustini" Ecology Lab, Coppito Science Center, University of L'Aquila, I-67100 L'Aquila, Italy. physa@tiscali.it.

ABSTRACT

Background: Although most freshwater planarias are well known photonegative organisms, their diel rhythms have never been quantified. Differences in daily activity rhythms may be particularly important for temperate-climate, freshwater planarias, which tend to overlap considerably in spatial distribution and trophic requirements.

Methods: Activity of stress-free, individually tested young adults of three common planarian species was recorded at 3-h intervals in a 10-d experiment under natural sunlight and photoperiod during autumnal equinox (D:L ~12:12). Individual activity status was averaged over the 10-d experiment, each tested individual thus serving as a true replicate. Twelve individuals per species were tested. Food was provided every 36 h, resulting in alternating day- and nighttime feeding events. Activity during the first post-feeding h was recorded and analyzed separately. Statistical procedures included ANOVAs, correlations, and second-order analyses of angles.

Results: Dugesia (= Girardia) tigrina Girard 1850 exhibited clear nocturnal behavior, Dugesia (= Schmidtea) polychroa Schmidt 1861 was predominantly but not exclusively nocturnal, and Polycelis tenuis Ijima 1884 was relatively more active from midnight through noon. Species-specific activity peaks were statistically similar, with peaks at dawn for P. tenuis and just before midnight for the two dugesiids; however, D. tigrina was comparatively more active in the early night hours, while D. polychroa was more active than D. tigrina during daytime. D. tigrina also responded less readily to daytime food addition. P. tenuis remained poorly active and unresponsive throughout the experiment. Individual variability in diel behavior was highest for D. polychroa and lowest for D. tigrina. P. tenuis's general low degree of activity and late activity peak in the experiment may be related to a strong reliance on external stimuli.

Conclusions: The tested species are mainly nocturnal, consistent with their photonegative characteristics. The fine-scale differences in diel behavior among these three triclad species may not be sufficient to allow coexistence in the wild, with the nonnative D. tigrina eventually displacing D. polychroa and P. tenuis in many European waters. The link between planarian diel rhythms and ecological characteristics are worth of further, detailed investigation.

No MeSH data available.