Download Feeding habits of Dictyogenus fontium (Plecoptera Perlodidae) in

Studi Trent. Sci. Nat., Acta Biol., 82 (2005): 77-83
© Museo Tridentino di Scienze Naturali, Trento 2006
ISSN 0392-0542
Feeding habits of Dictyogenus fontium (Plecoptera Perlodidae) in Alpine streams
(Trentino - NE Italy)
Bruno Maiolini* & Luana Silveri
Section of Invertebrate Zoology and Hydrobiology, Museo Tridentino di Scienze Naturali, Via Calepina 14, I-38100 Trento
(Italy)
*
Corresponding author e-mail: [email protected]
SUMMARY - Feeding habits of Dictyogenus fontium (Plecoptera Perlodidae) in Alpine streams (Trentino - NE Italy)
- Alpine high elevation streams host specialized benthic communites due to the harsh environmental conditions, and
Plecoptera Perlodidae and Perlidae include the most important predator species. The feeding habits of Dictyogenus
fontium (Plecoptera Perlodidae) was studied in high elevation Alpine streams. Sampling stations were on inlets and
outlets of three alpine lakes: Lake Lungo, Lake Marmotte and Lake Nero. Gut content analysis was used to assess prey
preferences. The composition of the benthic community of the sampling stations was assessed and the gut contents of
60 nymphs of D. fontium was analyzed. The benthic communities were dominated by Diptera, especially Chironomidae
and Simulidae, followed by Plecopetra, Tricoptera and Ephemeroptera. Results show a relationship between the structure of the local zoobenthos community and prey selection of D. fontium. Nymphs appeared to be rather opportunistic,
preying the most abundant invertebrate taxa present in the community.
RIASSUNTO - Abitudini alimentari di Dictyogenus fontium (Plecoptera Perlodidae) in torrenti alpini (Trentino
- NE Italia) - Nei torrenti Alpini d’alta quota, dove la comunità bentonica è altamente specializzata e adattata alle
difficili condizioni ambientali, i Plecotteri Perlodidae e Perliidae sono i maggiori predatori. Nel presente lavoro
sono state esaminate le abitudini alimentari del Plecottero Perlodiade Dictyogenus fontium in ambiente alpino. Le
stazioni di campionamento sono state poste su immissari ed emissari di tre laghi d’alta quota: il Lago Lungo, il
Lago delle Marmotte e il Lago Nero. Le preferenze alimentari di questi animali sono state studiate con il metodo
dell’analisi dei contenuti stomacali, basato sui residui chitinosi non digeriti. È stata individuata la composizione
della comunità bentonica di tutte le stazioni e analizzato il contenuto stomacale di 60 ninfe di D. fontium. La comunità zoobentonica è risultata dominata dai Ditteri Chironomidi e Simulidi, seguiti da Plecotteri, Tricotteri ed
Efemerotteri. I risultati mostrano una correlazione tra la composizione della comunità bentonica e la scelta delle
prede da parte di D. fontium. Si è evidenziato che le ninfe di D. fontium sono predatrici opportuniste che predano
i taxa più numerosi della comunità.
Key words: predation, stoneflies, gut contents, Alpine streams, Trentino
Parole chiave: predazione, Plecotteri, contenuti stomacali, torrenti alpini, Trentino
1. INTRODUCTION
“There is no discipline in hydrobiology that does not
require a study of the feeding and nutrition of aquatic
animals” (Monakov 2003).
The study of the feeding habits of aquatic macroinvertebrates has been implemented in the last ten years
because of its important contribute to the understanding
of the trophic structure of stream communities (Mihuc
1997; Resh & Rosemberg 1984). Predator species have
a very important role because they exert a top-down
control on the structure of the macroinvertebrate communities (Molles & Pietruszka 1987). In the last dec-
ades there was a strong impulse to the study of feeding
habits of stoneflies of the northern hemisphere (Allan
1982; Stewart & Stark 1988). One recent issue is the
linking of single species feeding habits with ecological
processes at the population and community level (Williams et al.1993). Alpine streams have a particular community structure in relationship with the harsh conditions of these habitats, due to low temperatures, channel instability, low nutrient availability etc. (Maiolini &
Lencioni 2000; Maiolini & Lencioni 2001). In Alpine
low order streams most predator species belong to the
orders Plecoptera and Tricoptera. To date, the studies on
predatory Plecoptera suggest the existence of different
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Maiolini & Silveri
feeding preferences in relationship with development,
ability to handle inactive but also active preys, and dimensions of the nymphs (Walde & Ronald 1987). In
fact, it has been demonstrated that there is a shift from
an herbivorous/detritivorous habit in the first instars,
to a strictly carnivorous diet in mature nymphs (Fuller
& Stewart 1977) Knowledge of possible variation in
diet is very important to understand the biology of a
species and in defining its role in community dynamics. To study the feeding habits of predator stoneflies
in the field, gut content analyses has proved to be a reliable method as it allows the identification of the preys
by the presence of undigested chitinous parts (Peckarsky 1996; Allan 1995).
In this work we present results deriving from gut
analyses of Dictyogenus fontium (Ris, 1896) in the aim
of producing evidence of prey preferences and prey selection in relation to community structure.
2. Study area
The study area is Val Lagolungo, in the Noce Bianco basin, in Val de la Mare (Stelvio National Park,
Trentino - Italy) (Fig. 1). In
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the valley there are 5 glaciers: Vedretta de la Mare, originating the Noce Bianco stream, glacier Careser, originating the Rio Careser stream, Vedretta Venezia, Vedretta Rossa and Vedretta del Cavaion (Gruppo Nazionale di Fisica Geomorfologica - C.N.R., 1986). A non glaciated sub basin with three alpine lakes (Lake Marmotte, 2705 m
a.s.l.; Lake Lungo, 2550 m a.s.l.; Lake Nero, 2621 m
a.s.l.) is located between the De La Mare and Careser
glaciers. These first order streams may be assigned to
Feeding
habits of Dictyogenus fontium in Alpine streams
the rhithron typology and are partially impacted by water withdrawing for hydropower production. Samples
from four stations were considered in this work: two
on the inlet of Lake Lungo (ImL1, 2730 m a.s.l., and
ImL2, 2600 m a.s.l.), one on the outlet of Lake Marmotte (EmM2, 2350 m a.s.l.) and the last on the outlet
of Lake Nero (EmN, 2620 m a.s.l.).
3. methods
Zoobenthic samples were collected seasonally from
2000 to 2002 and in each occasion the main environmental parameters, such as current velocity, conductivity, temperature and substrate composition, were
recorded (details on physico-chemical features are in
Boscaini et al. 2004). In each station and date five replicate benthic samples were collected with a 100 μm
mesh pond net, disturbing for one minute a 0.1 m2 area. Samples were preserved in the field with ethanol
to a final concentration of 75%. Organisms were sorted under a dissection microscope and identified to the
lowest possible taxonomical level.
The gut content of 60 nymphs of Dictyogenus fontium (Plecoptera, Perlodidae) (Fig. 2) was analyzed.
Length and width of the cephalic capsule and length
of the body (from the head to the last urite) was measured for each nymph (Fig. 3). Preys were identified using undigested chitinouse parts, especially head capsules. Gut content was compared with composition and
abundance of the benthic community in order to evaluate prey selectivity of predaceous stoneflies.
4. Results
60 nymphs of D. fontium were selected from the
116 sampled in the study area, and 44 of them had undigested chitinouse parts in the gut.
Fig. 1 - Study area: Val Lagolungo (Trentino) with lakes and
sampling stations.
Fig. 1- Val Lagolungo (Trentino) con le stazioni campionate.
Fig. 2 - Dictyogenus fontium (Ris.) with Chironomidae
(photo B. Maiolini)
Fig. 2 - Dictyogenus fontium (Ris.) con Chironomidae (foto
B. Maiolini).
Studi Trent. Sci. Nat., Acta Biol., 82 (2005): 77-83
79
Fig. 3 - Abundance and biodiversity of the benthic community in all stations. a) Diversity and relative abundance of the macrobenthic community. b) Diversity and relative abundance of stoneflies community. c) Taxa and number of preys.
Fig. 3 - Abbondanza e diversità della comunità bentonica nelle stazioni indagate. a) Diversità in taxa e abbondanza relative della comunità. b) Diversità in taxa e abbondanza relativa della comunità di Plecotteri. c) Taxa predati e numero
di prede.
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Maiolini & Silveri
(Fig. 3 - continued)
(Fig. 3 - continua)
Feeding
habits of Dictyogenus fontium in Alpine streams
Studi Trent. Sci. Nat., Acta Biol., 82 (2005): 77-83
In EmM2 the community was well diversified.
Diptera represented 80% of the community, with Chironomidae as dominant family in every seasons (mean
78%). Plecoptera, Tricoptera and Ephemeroptera accounted for 5%, 3% and 0.5% of benthic community,
respectively (Fig. 3).
D. fontium was the most abundant stonefly (61%)
and was the only predator species, followed by Leuctra sp. (36%) and Rhabdiopteryx alpina (Kuehtreiber,
1934) (2%), both herbivorous species (Fig. 3).
Ten D. fontium nymphs were selected for analyses
from this station. Body length of the nymphs ranged
between 28 mm and 3 mm.
Three nymphs had chitinouse parts in the gut.
80% of the preys were Chironomid larvae (20 of 25
items).
Other preys were Simuliidae (2 larvae), Limoniidae
(2 larvae) and Limnephiliidae (1 larva) (Fig. 3).
In EmN the benthic community was dominated by Chironomidae (60%), and Simullidae (34%).
Plecoptera were 1.7%, Tricoptera 1% and Efemeroptera 0.1% of the sampled community (Fig. 3). D. fontium was the most abundant predator stonefly (11% of
the stoneflies), followed by Perlodes sp. (6%) and herbivorous stoneflies as Leuctra sp. (39%) and R. alpina (44%) (Fig. 3).
Two of the four analyzed nymphs of D. fontium had
undigested residues in their gut. Their lengths were
11.7 mm and 7.1 mm. Preys were 15 Chironomidae
(Diamesa zerniy/cinerella group and Ortocladius sp.)
and one Simulidae (Prosimulium latimucro Enderlein,
1925) (Fig. 3).
ImL1 presented a well structured benthic community, Diptera were 73% of the total community with
Chironomidaes (62%) and Simulidae (8.5%) as most
abundant families. Within EPT, Tricoptera was the most
represented (16%), followed by Plecoptera (7%) and
Ephemeroptera (0.6%) (Fig. 3).
Plecoptera community was well diversified with the
predator species D. fontium (58%) and Isoperla rivulorum (Pictet, 1842) (7%), and the herbivorous Leuctra sp. �������
(17%), Nemoura sp. (5%), R. alpina (3%), [Nemoura Ris 1902 mortoni] (0.8%) and Protonemura sp.
(0.8%), (Fig. 3).
In this station, 37 nymphs of the 44 analyzed had
chitinouse residues and their body length ranged between 17.1 mm and 2.2 mm. Chironomidae (especially
Diamesae and Ortocladius sp.) were the most preyed
organisms. In one nymph we found 36 Chironomid
cephalic capsules. Residues of Athericidae, Limoniidae, Tricoptera Limnephilidae and Plecoptera were also found (Fig. 3).
Finally, in ImL2 the community was dominated by
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Chironomidaes (92%), followed by Simulidae (4%), Tricoptera (0.1%), Ephemeroptera (0.03%) and Plecoptera
(1%) (Fig. 6a). The Plecoptera community was diversified
with the predatory species D. fontium (12%) and the herbivorous ones R. alpina (21%), Nemoura sp. (39%), Protonemura sp. (24%). and Taenoipteryx (3%) (Fig. 3).
Four nymphs of D. fontium, with body length between
23 mm and 1.7 mm, were analyzed from ImL2: two had
no preys and other two had undigested parts of Chironomidae (7 organisms) and one springtail (Fig. 3).
5. Discussion
As expected in high Alpine streams, benthic communities were dominated by Diptera Chironomidae,
followed by EPT taxa (Kownacki 1991; Milner & Petts 1994; Lencioni et al. 2002; Maiolini & Lencioni
2000).
D. fontium is widespread in the Italian Alps, where it populates rhithral streams even at high elevation.
In Trentino it was recorded up to 2700 m a.s.l. (Lencioni et al. 2001). Nymphs have an annual life-cycle
with mature larvae from 15 to 25 mm long; adults
emerge from June to September (Consiglio 1980). D.
fontium is one of the biggest predatory stoneflies present in Alpine streams, but its feeding habits are still
poorly known.
Studies regarding carnivorous species allow investigating the food chains that regulate the structure of
stream communities (Allan 1995). Unfortunately, there are few studies on the predatory Plecoptera living in
Alpine environments, probably due to the relative recent interest towards these ecosystems.
Of the 60 examined nymphs, 16 had empty guts,
probably due to their larval stage as Perlodid and Perlid nymphs stop feeding during the last instars or near
moults (Elliot 2000; Fenoglio 2003; Fenoglio & Tierno de Figueroa 2003; Tierno de Figueroa & Fochetti
2001). In two cases the absence of preys was probably due to bad health conditions of the nymphs, visibly wounded.
32 nymphs had ingested individuals belonging to
only one taxon, 11 had ingested two different prey taxa. In one case a mature nymph (28 mm length, station EmM2) was found with gut residues. This is also
the only case in which one nymph ingested preys belonging to three different taxa (Chironomidae, Tricoptera Limnephilidae and Simulidae).
The choice of one or more prey taxa appeared not
to be associated with dimensions and developmental
stage of the nymphs. More data are needed to investigate statistical correlations.
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Maiolini & Silveri
Fenoglio and Bo (2004) found that Dictyognus alpinus (Pictet 1842) living at lower elevations in the
western Italian Alps (1500-2000 m a.s.l.) had a rather
clear prey preference for Chironomidae and Baetidae,
not strictly dependent on the available preys and in some cases the diet was integrated with vegetal fragments. Other studies (Dudgeon 2000; Fenoglio 2003) show
a clear link between prey selection and composition of
the local benthic community.
Our results indicate that D. fontium in high elevation Alpine streams feeds mainly on Chironomid larvae, which are the most abundant preys, and
that other preys, though present, are not actively selected.
The second preferred prey were blackfly and caddiesfly larvae, which were also the second and third
abundant taxa in the benthic community. Thus, predation in high elevation habitats with low macroinvertebrate densities seems driven by relative availability of possible preys.
Acknowledgements
Particular thanks to all the colleagues of the Section of Invertebrate Zoology and Hydrobiology for their
help in the field and in sorting the samples, to Romolo
Fochetti (Tuscia University) for taxonomical assistance
and to Maria Cristina Bruno for helpful comments on
the draft manuscript.
This work is part of the PhD project “Stonefly ecology in the Italian Alps”, assigned by the University of
Parma, tutor Giampaolo Rossetti.
These data were produced within the project CryoAlp (Role of the Alpine cryiosphere in the hydrology) founded by IMONT (Istituto Italiano per la Montagna).
REFERENCES
Allan J.D., 1982 - Feeding habits and prey consumption of
three predaceous stoneflies (Plecoptera) in a mountain
stream. Ecology, 63: 26-34.
Allan J.D., 1995 - Stream ecology. Structure and function of
running waters. Chapman and Hall, London (Britain):
400 pp.
Boscaini A., Corradini F., Lencioni V. & Maiolini B., 2004
- Caratterizzazione morfologica e chimico-fisica di
un sistema idrografico alpino (Parco Nazionale dello
Stelvio, Trentino). Studi Trent. Sci. Nat., Acta Biol., 80
(2003): 43-49.
Consiglio C., 1980 - Plecotteri (Plecoptera). In: Ruffo S. (a
cura di), Guide per il riconoscimento delle specie animali
Feeding
habits of Dictyogenus fontium in Alpine streams
delle acque interne italiane. Vol. 9. C.N.R. AQ/1/77,
Verona: 68 pp.
Dudgeon D., 2000 - Indiscriminate Feeding by a Predatory
Stonefly (Plecoptera Perliidae) in a Tropical Asian
Stream. Aquatic Insects, 22: 39-47.
Elliot J.M., 2000 - Contrasting diel activity and feeding
patterns of four specie of carnivorous stoneflies. Ecol.
Entom., 25: 26-34.
Fenoglio S., 2003 - Feeding habits of Anacroneuria nymphs
(Plecoptera, Perliidae). Boll. Soc. entomol. ital., 135 (1):
15-17.
Fenoglio S. & Tierno de Figueroa M., 2003 - Observations on the
adult feeding of some Neoperla and Anacroneuria species
(Plecoptera, Perlidae). African Entomology, 11: 138-139.
Fenoglio S. & Bo T., 2004a - Trophic caracterizazion of
Dictyogenus alpinus (Pictet, 1842, Plecoptera Perlodidae)
nymphs in the high Po valley (NW Italy). Zool. Baetica,
15: 167-174.
Fuller R.L. & Stewart K.W., 1977 - The food habits of stoneflies (Plecoptera) in the upper Gunnison River, Colorado.
Envir. Ent., 6: 293-302.
Gruppo Nazionale Geografia Fisica Geomorfologia - C.N.R.,
1986 - Ricerche geomorfologiche nell’Alta Val di Pejo
(Gruppo Cevedale). Geogr. Fis. Dinam. Quat., 9 (2):
143-144.
Kownacki A., 1991 - Zonal Distribution and classification of
the invertebrates communities in a high mountain stream
in South Tirol (Italy). Vern. Internat. Verein. Limnol., 24:
2010-2014.
Lencioni V., Maiolini B. & Zuccati S., 2001 - Temporal drift
patterns in a high mountain stream system (Conca, Adamello-Brenta Natural Park, Trentino, Italy). Studi Trent.
Sci. Nat., Acta Biol., 76 (1999): 113-123.
Lencioni V., Boscaini A., Franceschini A. & Maiolini
B., 2002 - Distribution of benthic invertebrates in
high mountain streams in the Italian Alps: a review
and recent finding. Atti del XII Convegno Soc. Ital.
Ecol. (S.It.E), Sabaudia (LT), 2001. Atti S.It.E., 25
(CD-ROM).
Maiolini B. & Lencioni V., 2000 - A glacial stream ecosystem
in the Italian Alps. Verh. International Verein. Limnol.,
27 (2): 716-719.
Maiolini B. & Lencioni V., 2001 - Longitudinal distribution
of macroinvertebrate assemblages in a glacially influenced stream system in the Italian Alps. Freshwat. Biol.,
46: 1625-1639.
Mihuc T.B., 1997 - The functional trophic role of lotic primary consumers: Generalist versus specialist strategies.
Freshwat. Biol., 37: 455-462.
Milner A.N. & Petts G.E., 1994 - Glacial rivers: physical
habitat and ecology. Freshwat. Biol., 32: 295-307.
Molles M. & Pietruszka R.D., 1987 - Prey selection by a
stonefly: the influence of hunger and prey size. Oecologia, 72: 473-478.
Monakov A.B., 2003 - Feeding of freshwater invertebrates.
Kenobi Production. Ghent, Belgium: 373 pp.
Studi Trent. Sci. Nat., Acta Biol., 82 (2005): 77-83
Peckarsky B.L., 1996 - Predatory-prey interactions. In: Hauer
F.R. & Lamberti G.A. (a cura di), Methods in stream
ecology. Academic Press New York: 431-451.
Resh V. & Rosemberg D., 1984 - The ecology of aquatic
insects. Praeger, New York/USA: pp.1350
Stewart K.W. & Stark B.P., 1988 - Nymphs of North American stoneflies genera (Plecoptera). Entomol. Soc. Of
America Thomas Say Foundation, 12: 460.
Tierno de Figueroa J.M. & Fochetti R., 2001 - On the adult
feeding of several european stoneflies (Plecoptera). En-
83
tomol. News, 112: 130-134.
Walde S.J. & Ronald W.D., 1987 - Spatial and temporal
variation in the diet of a predaceous stonefly (Plecoptera
Perlodidae). Freshwat. Biol., 17: 109-115.
Williams D.D., Barnes J.A. & Beach P.C., 1993 - The effects
of prey profitability and habitat complexity on the foraging success and growth of stonefly (Plecoptera) nymphs.
Freshwat. Biol., 29: 107-117.
Accettato per la stampa: 10 settembre 2006