Le triclade Polycelis felina est un taxon intéressant par son rôle de bioindicateur important dans les cours d'eau et les petits environnements lotiques. Des informations ont été recueillies sur sa distribution dans les cours
        d'eau de la partie sud de la province de Lecco (N Italie) afin d'obtenir une image claire de ses préférences biologiques et écologiques et des particularités des biotopes dans lesquels on le trouve. Au total 194 sites sur 110 cours d'eau ont été prospectés durant la campagne de terrain menée
        en 2005 et 2006. Des populations de P. felina furent trouvées dans 26 % des sites visités. Les rôles respectifs, quant à la présence de P. felina, de la morphologie naturelle du cours d'eau, de la qualité de l'eau, et d'autres facteurs (tels la présence d'autres triclades, d'écrevisses et de
        larves de Salamandra salamandra) ont été analysés

MANENTI, Raoul

I-Revues

Rev. Écol. (Terre Vie), vol. 65, 2010.
 – 279  –
note brève
The role of waTercourse feaTures and of landscape sTrucTure 
in The disTribuTion of Triclads inhabiTing head waTers: 
The example of Polycelis felina
raoul manenti1
résumé. — le rôle des caractères du cours d’eau et de la structure du paysage sur la distribution 
des triclades dans le haut des cours d’eau : l’exemple de polycelis felina. — le triclade Polycelis felina est 
un taxon intéressant par son rôle de bioindicateur important dans les cours d’eau et les petits environnements 
lotiques. des informations ont été recueillies sur sa distribution dans les cours d’eau de la partie sud de la 
province de Lecco (N Italie) afin d’obtenir une image claire de ses préférences biologiques et écologiques et 
des particularités des biotopes dans lesquels on le trouve. au total 194 sites sur 110 cours d’eau ont été pros-
pectés durant la campagne de terrain menée en 2005 et 2006. Des populations de P. felina furent trouvées 
dans 26 % des sites visités. les rôles respectifs, quant à la présence de P. felina, de la morphologie naturelle 
du cours d’eau, de la qualité de l’eau, et d’autres facteurs (tels la présence d’autres triclades, d’écrevisses et 
de larves de salamandra salamandra) ont été analysés.
The ecological studies of macro-benthic taxa inhabiting watercourses mainly deal with 
organisms related to human activities and traditions, such as fishes and freshwater crayfishes, 
with less papers related to inconspicuous and less known organisms like Triclads. The ecologi-
cal studies dealing with these latter, and especially with species inhabiting lotic habitats, are 
few and often out of date. However, Triclads can play an important role in watercourse ecosys-
tems and are often very important as bio-indicators (Tachet, 2002).
In this context our paper presents information about the ecology of the stream-dwell-
ing triclad Polycelis felina Dalyell 1814 collected during a survey of the watercourses in the 
southern part of the Lecco district (Lombardy, Italy). In Italy the genus Polycelis occurs with 
three species such as P. nigra (muller 1774) and P. tenuis Ijima 1884 inhabiting lakes, ponds, 
marshes and rivers and P. felina distributed in streams, brooks, creeks with slow flowing and in 
different typology of springs (Campaioli et al., 1994; sansoni, 2001; manenti, 2003).
in spite of many laboratory studies about P. felina tolerance to many chemical substances 
or to experimental conditions (i.e. Kouyoumjian & Uglow, 1974; Brown et al., 1988; Kopjar et 
al., 2005), field studies on the ecology of this species are less frequent. Interesting data about 
the distribution and the ecology of some triclads, including P. felina, in the freshwater habitats 
1 Via san lorenzo, 47. i-23884 castello di brianza (lecco), italy. e-mail : manentiraoul@alice.it
 – 280  –
of North Wales and in the springs of central Pyrenees are provided by Wright (1972, 1974) and 
roca et al. (1992). Lock (1975) studied the role of gradient and substratum in the distribution 
of P felina in the watercourses of North Wales, finding that it had a much reduced ability to 
colonize the simulated steep-gradient bottoms and suggesting that the absence of P. felina from 
the steep-gradient regions of streams in North Wales is due to a behavioural inability to tolerate 
the current regimes present in the steep-gradient bottoms.
The purpose of our research was to obtain a clear picture of the distribution of P. felina in 
the watercourses of the studied area and of its ecological and biological preferences in order to 
increase the knowledge about this taxon.
maTerial and meThods
sTudy area
The study area (Fig. 1) covers the whole of the southern part of the Lecco province which has a continental climate. 
it is comprised in the catchment basins of the lambro and adda rivers. it is characterized by hilly and mountainous 
reliefs with a good cover of broadleaved woodlands. It has a diversified orographic structure and is crossed by a lot of 
watercourses which make up a dense hydrographic network characterized by different typologies of water bodies such 
as creeks, streams, brooks, resurgences and rivers. However, ongoing urban and industrial development is increasingly 
modifying the landscapes.
surVeys
For two consecutive years from 2005 to 2006 field investigations were carried out in all the watercourses of the 
area. We identified sampling localities on the basis of 1 : 25 000 or 1 : 10 000 topographical maps or by the direct 
exploration of the territory with no lotic water body being excluded a priori. Their elevation was 200-642 m above sea 
level, and was therefore within the usual range of the species (Tachet, 2002).
P. felina specimens were searched during the day performing samplings by moving the substrate for 5-10 minutes and 
using a thin-mesh dip net to collect the planarians, by hand lifting stones, observing the substrate elements and catching 
materials of the bottom of the watercourses. Every site has been observed at least twice during the study period.
habiTaT characTerizaTion
Sites were described by compiling a table of characteristics based on rapid bio-assessment protocols (Barbour et 
al., 2002) that includes parameters for the biological and ecological requirements of triclads (Tachet, 2002) and items 
referring to water quality and site resilience.
We recorded surrounding habitat characteristics on the basis of the 1 : 10 000 Vector Map of Lombardy, using the 
ArcView 3.2 GIS. In several studies it has been demonstrated that landscape structure plays an essential role in affecting 
the occurrence of stream-dwelling organisms such as salamanders (Ficetola et al., 2009; manenti et al., 2009) and 
crayfishes (Nardi et al., 2005).
The status of aquatic macro-invertebrates communities was evaluated according to the EBI protocol (Ghetti, 
1997) in 142 sites; a score ranging from 1 to 14 permits to put the macro-benthic communities into 5 categories 
indicating water quality, from I (unaltered macro-benthic community) to V (completely altered macro-benthic 
community).
In addition we evaluated the occurrence of other triclads and two other biotic parameters such as the occurrence 
of the autochthonous crayfish austropotamobius italicus (faxon 1814) and of the larvae of the amphibian salamandra 
salamandra (linnaeus 1758) in order to establish some possible correlation between the triclad and two of the most 
representative organisms in the watercourses biomass. Data on crayfish occurrence were extrapolated by Manenti (2006) 
while those on s. salamandra occurrence were taken from part of the data of Manenti et al. (2009). we cross-refered to 
those studies for further information on these species detectability.
resulTs
We investigated 194 sites on 110 watercourses. P. felina has been observed in 51 of them 
while in the other 143 sites the species has not been found (Fig. 1). P felina was detected at 
an altitude varying from 251 to 815 m a.s.l. with a majority of observations (37.3 %) taking 
place in the altitudinal range included between 301 and 350 m a.s.l. (Fig. 2). The altitudinal 
maximum of 815 m a.s.l. is reached in the central hilly part of the studied area.
 – 281  –
Speaking about environmental parameters in figures 3 & 4 it is possible to appreciate that 
most of the P. felina populations (77 %) were found in sites with a river course highly diversi-
fied and a high variety of substratum, corresponding to a great availability of shelters, while in 
negative sites percentages of the different typologies are more equally distributed.
Figure 1. — Distribution of Polycelis felina in the southern part of the lecco district. ○  =  negative sites, 
● = positive sites.
Figure 2. — Presence (+) and absence (-) of Polycelis felina according to altitude intervals.
0
10
20
30
40
50
60
200  -250 251 -300 301 -350 351 -400 401 -450 451 -500 501 -550 551 -600 >601
N
N  sites +
N  sites -
%  sites +
%  sites -
Altitudes
 – 282  –
It has not been possible to apply the EBI protocol at 79 sites that in some cases were 
temporary or too close to springs while in others the superficial water flow was fragmented 
into isolated pools or the flow velocity was near 0. Nevertheless, P. felina was more frequent 
where biological quality of the water was better; in any case it is interesting to note that this 
species was found in some (2.6 %) polluted sites (EBI class III) with an EBI score of almost 
7 (Figs 5 & 6).
most P. felina populations were found in wooded areas (64.7 %) and agricultural ones 
(31.4 %); however few of them (3.9 %) survive in artificial areas characterized by urban devel-
opment. In the watercourses we observed, the only other triclad found was the genus Dugesia; 
none of the sites inhabited by Dugesia sp. housed also P. felina.
Figure 3. — Presence (+) and absence (-) of Polycelis felina according to the variety of the river course.
Figure 4. — Presence (+) and absence (-) of Polycelis felina according to the variety of the substratum.
Variety of substratum
 – 283  –
A great percentage of the sites positive to P. felina were inhabited by autochthonous cray-
fishes (86.3 %) and used for deposition by salamandra salamandra (80.3 %) while negative 
sites were 75.5 % and 68 % without these taxa respectively (fig. 7).
Figure 5. — Presence (+) and absence (-) of Polycelis. felina according to the biological quality of the site expressed 
in ebi classes (ghetti, 1997).
Figure 6. — Presence (+) and absence (-) of Polycelis felina according to the biological quality of the site expressed 
in ebi scores (ghetti, 1997).
 – 284  –
discussion
This comprehensive survey of Polycelis felina throughout the lotic biotopes of the hydro-
graphic system of the southern part of the Lecco province has increased the knowledge of the 
distribution of this elusive species.
data about the altitudinal distribution of the species must be attentively considered 
because in the studied area sites located above 600 m a.s.l are few, and it might be possible 
that in this range the percentage of positive sites exceeds that of the negative ones. In any case 
P. felina seems to be absent from sites situated below 251 m a.s.l., showing a preference for 
the hilly district of the province. Talking about water quality, P. felina was found to be more 
versatile than its biotic score (ghetti, 1997) lets usually think, with some findings in condition 
of pollution and with not optimal macro-benthic community, even if the great percentage of 
sites inhabited by this triclad remains in a situation of unpolluted water. Interesting are the data 
about the variety of the river course and of the substratum that show the high diversity reached 
by the greatest part of the sites where P. felina lives. This fact, together with the indication 
resulting from the analysis of the land cover classes where positive sites are located, suggests 
the importance of human impact in determining the distribution of this species not only by 
watercourses pollution, but also by affecting the landscape structure. Comparison with the 
occurrence of the crayfish austropotamobius italicus and of the larvae of s. salamandra shows 
the affinity between these taxa in habitat preferences. Also for the latter has been evidenced the 
importance of a high percentage of wood cover around the damp biotopes (Nardi et al., 2005; 
fietola et al., 2009; manenti et al., 2009).
The number of sites where the genus Dugesia occurs is not so relevant, but gives in any 
case an indication about a possible competition and incompatibility between these triclads.
The results of this study although increasing the knowledge about P. felina suggest that 
further investigation of the habitat requirement are necessary to better define the importance of 
this taxon in the maintenance of freshwater biodiversity.
Figure 7. — Presence (+) and absence (-) of Polycelis felina according to some biological and ecological factors.
 – 285  –
references
BarBour, m.t., Gerristen, J., snyder, B.d. & striBlinG, J.B. (1999). — Rapid bioassessment protocols for use in 
streams and wadeable rivers : Periphyton, benthic macroinvertebrates and fish. second edition. epa 841-
B-99-002. U.S. Environmental Protection Agency ; Office of Water, Washington D.C., http ://www.epa.gov./
owow/monitoring/rbp/wp61/pdf/rbp.pdf (03-02-2004).
Brown, a.F. & Pascoe, d. (1988). — Studies on the acute toxicity of pollutants to freshwater macroinvertebrates. 5. 
The Acute toxicity of Cadmium to Twelve Species of Predatory. arch. f. Hydrobiol., 114 : 311-319.
camPaioli, s., Ghetti, P.F., minelli, a. & ruFFo, s. (1994). — Manuale per il riconoscimento dei macroinvertebrati 
delle acque dolci italiane. provincia autonoma di Trento, Trento.
Ficetola, G.F., Padoa-schioPPa, e. & de Bernardi, F. (2009). — Influence of landscape elements in riparian buffers 
on the conservation of semiaquatic amphibians. cons. Biol. 23 : 114-123.
Ghetti, p.f. (1997). — indice biotico esteso (i.B.e.). Provincia Autonoma di Trento, Agenzia provinciale per la prote-
zione dell’ambiente, Trento.
lock, M.A. (1975). — An experimental study of the role of gradient and substratum in the distribution of two stream-
dwelling triclads, crenobia alpina (dana) and Polycelis felina (dalyell) in north wales. freshwater Biol., 
5 : 211-226.
manenti, r. (2003). — Il ruolo ecologico delle Bevere. Pp 37-44 in : Bevere : un territorio da salvare. comitato 
bevere, briosco (mi).
manenti, r., Ficetola, G. F. & de Bernardi, F. (2009). — Water, stream morphology and landscape : complex habi-
tat determinants for the fire salamander salamandra salamandra. amphibia-Reptilia, 30 : 7-15.
nardi, P. a., Bernini, F., Bo, t., Bonardi, a., Fea, G., Ghia, d., neGri, a., razzetti, e., rossi, s. & sPairani, 
m. (2005). — status of austropotamobius pallipes complex in the watercourses of the Alessandria province 
(n-w italy). Bull. franc. Pêche Piscic. : 585-598.
roca, J. r., riBas, m. & aGrave, J.B. (1992). — Distribution, ecology, mode of reproduction and karyology of 
freshwater planarians (Platyhelminthes ; Turbellaria ; Tricladida) in the springs of the central Pyrenees. ecog-
raphy, 15 : 373-384.
koPJar n., horvat, t., kalaFatic, m. & kovacevic, G. (2005). — Toxicity testing of herbicide norflurazon on an 
aquatic bioindicator species - the planarian Polycelis felina (daly.). aquatic Toxicology, 73 : 342-352.
kouyoumJian, h.h. & uGlow, r.F. (1974). — some aspects of the Toxicity of p,p’-ddT, p-p’-dde and p,p’-ddd 
to the Freshwater Planarian Polycelis felina (Tricladida). envir. Pollution, 7 : 103-109.
sansoni, g. (2001). — Macroinvertebrati dei corsi d’acqua italiani. Provincia Autonoma di Trento. Agenzia provin-
ciale per la protezione dell’ambiente, Trento.
tachet, h. (2002). — invertébrés d’eau douce. cnrs éditions, paris.
wriGht, J.F. 1972. — The distribution of stream-dwelling triclads (Platyhelminthes) in North Wales. freshwater Biol., 
2 : 57-64.
wriGht, J.f. (1974). — Some factors affecting the distribution of crenobia alpina (dana), Polycelis felina (daly-
ell) and Phagocata vitta (Dugès) (Platyhelminthes) in Caernarvonshire, North Wales. freshwater Biol., 4 : 
31-59.



Le rôle des caractères du cours d’eau et de la structure du paysage sur la distribution des triclades dans le haut des cours d’eau : l’exemple de Polycelis felina

http://documents.irevues.inist.fr/bitstream/2042/55845/1/RevuedEcologie_2010_65_3_279.pdf

Le rôle des caractères du cours d’eau et de la structure du paysage sur la distribution des triclades dans le haut des cours d’eau : l’exemple de Polycelis felina

Abstract

Similar works

Full text

Available Versions

I-Revues