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Feeding habits of the European pond terrapin Emys orbicularis in Camargue (Rhône Delta, Southern France)

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  • Agenzia Regionale per la Protezione dell'Ambiente Ligure

Abstract

The diet of the European pond terrapin Emys orbicularis is poorly known, especially in the Mediterranean region. Bannikov (1951) showed that in the Russian Republic of Daghestan this species mainly feeds on aquatic and terrestrial invertebrates. Lebboroni and Chelazzi (1991) in Tuscany (Italy), and Kotenko (2000) in Ukraine noticed the predominance of invertebrates but a high occurrence of plant matter in the diet. The aim of our study was to determine the diet of E. orbicularis in Camargue, a Mediterranean habitat, and to investigate for eventual dietary shifts. Emys orbicularis is widespread in Camargue (Rhone river delta, southern France), an area where one of the two major populations of the French Mediterranean region is found (Cheylan, 1998). The diet of E. orbicularis in the Tour du Valat estate, Camargue (43◦30� N-4◦39� E), was studied from April to August 2003. In this region E. orbicularis is mainly found in two kinds of habitats: manmade irrigation canals and natural temporary marshes. During the study period, water levels in marshes were highest in April (55 cm), while drought occurred from the end of June until October. In this study E. orbicularis specimens were collected in all habitats independently from the season, but at the end of June, the marshes dried out making it impossible to sample terrapins in this habitat. European pond terrapins were captured preferentially by hands. Fyke nets, baited with beef, were also used occasionally. In these cases nets were visited every hour to prevent the terrapins from eating other trapped animals. Date of capture, sex, carapace length (CL)
Feeding habits of the European pond terrapin Emys orbicularis
in Camargue (Rhône delta, Southern France)
Dario Ottonello1,2, Sebastiano Salvidio2, Elisabeth Rosecchi1
The diet of the European pond terrapin Emys
orbicularis is poorly known, especially in the
Mediterranean region. Bannikov (1951) showed
that in the Russian Republic of Daghestan this
species mainly feeds on aquatic and terrestrial
invertebrates. Lebboroni and Chelazzi (1991) in
Tuscany (Italy), and Kotenko (2000) in Ukraine
noticed the predominance of invertebrates but
a high occurrence of plant matter in the diet.
The aim of our study was to determine the diet
of E. orbicularis in Camargue, a Mediterranean
habitat, and to investigate for eventual dietary
shifts.
Emys orbicularis is widespread in Camargue (Rhône river
delta, southern France), an area where one of the two major
populations of the French Mediterranean region is found
(Cheylan, 1998). The diet of E. orbicularis in the Tour du
Valat estate, Camargue (4330N-439E), was studied from
April to August 2003. In this region E. orbicularis is mainly
found in two kinds of habitats: manmade irrigation canals
and natural temporary marshes. During the study period,
water levels in marshes were highest in April (55 cm), while
drought occurred from the end of June until October.
In this study E. orbicularis specimens were collected in
all habitats independently from the season, but at the end of
June, the marshes dried out making it impossible to sample
terrapins in this habitat. European pond terrapins were cap-
tured preferentially by hands. Fyke nets, baited with beef,
were also used occasionally. In these cases nets were vis-
ited every hour to prevent the terrapins from eating other
trapped animals. Date of capture, sex, carapace length (CL)
1 - Station Biologique de la Tour du Valat, Le Sambuc
13200 Arles, France
Corresponding author; address: DIP.TE.RIS. Università
di Genova, Corso Europa 26, 16132 Genova, Italy
e-mail: dario.ottonello@herpetosavona.it
2 - DIP.TE.RIS. Università di Genova, Corso Europa 26,
16132 Genova, Italy
and habitat type were recorded on each capture, and only
specimens with evident sexual characters were considered
as adults (Lanza, 1983). All captured specimens were indi-
vidually marked by unique notch patterns on their carapace
and were held in separate buckets filled with shallow wa-
ter for 24 hours. The faecal samples collected were gently
washed with water and filtered with a 500-micrometer sieve,
stored in 70% alcohol and examined under a dissecting mi-
croscope. Prey items were identified down to the lowest pos-
sible systematic level, depending on their digestion state,
using aquatic macroinvertebrate keys and a reference collec-
tion. For each food type, the number of items and their wet
weight were recorded. Prey items were grouped into major
taxa for statistical analyses. Faecal samples from recaptured
animals were excluded from the analysis. Two periods could
be distinguished within the sampling season: the reproduc-
tive phase (from the end of April to the middle of July) and
the post-reproductive phase (from middle of July to the end
of August).
Dietary composition was evaluated using three different
indices:
frequency of occurrence of food item x,
Fx=(Nx/N),
where Nxis the number of faecal samples with food item x
and Nis the total number of faecal samples,
percentage abundance by number of food item x,
%Ax=(Tx/Tt)×100,
where Txis the number of prey xof each faecal sample and
Ttis the total number of prey items of all faeces samples,
percentage abundance by weight of food item x,
%Wx=(Yx/Yt)×100,
where Yxis the weight of prey xof each faecal sample and
Ytis the total weight of prey items of all faeces samples.
This index was only used to compare an eventual shift in
consumption of plant matter.
Plant remains and unidentified matter were not consid-
ered in the percentage abundance analysis because they did
not occur as discrete units. The number of molluscs was
probably underestimated because shell fragments were con-
sidered as a single food item. Vertebrata remains only refer
©Koninklijke Brill NV, Leiden, 2005. Amphibia-Reptilia 26 (2005): 562-565
Also available online - www.brill.nl
Short Notes 563
to bone fragments, and very few fish scales found were con-
sidered as incidentally ingested.
During this study faeces from 31 terrap-
ins were obtained: twenty-one females (mean
CL =164.3 mm; range 143.5-190.0 mm), six
males (mean CL =139.2 mm; range 118.5-
155.0 mm) and four juveniles (mean CL =
74.4 mm; range 67.0-90.6 mm). Because of the
small size of faecal samples of males and ju-
veniles, a statistical comparison between sexes
and between adults and juveniles was not possi-
ble.
In terms of frequency of occurrence E. orbic-
ularis mainly fed on aquatic invertebrates, such
as Coleoptera, Decapoda, Odonata, Gastropoda
and Heteroptera (table 1). The most frequent
prey of adults was the introduced red swamp
crayfish Procambarus clarkii that was absent
from juvenile samples (table 1).
Plant remains were present in 89% of adult
and 25% of juvenile faeces. Terrestrial or fly-
ing invertebrates (adult Libellulidae and Coena-
grionidae, Araneae and Formicidae), were also
important, occurring in about 45% of samples
and representing 61% of the number of prey
items of juveniles and 9% of prey items of
adults. Terrestrial arthropods were more abun-
dant in the diet of adult specimens from canals
than in those from marshes (χ2=24.437;
DF =1; p<0.001), and the weight of plant
matter was higher in the faeces of adult ter-
rapins from canals, than in those from marshes
(χ2=24.545; DF =1; p<0.001).
The consumption of plant matter was also dif-
ferent between reproductive and post-reproduc-
tive period (χ2=19.195; DF =1; p<0.001)
but, considering only canals, we did not no-
tice differences between samples collected in
these two periods (χ2=1.3931; DF =1;
p=0.238).
Our study showed that the European pond
terrapin is an opportunistic predator with a
broad dietary niche that could, as in many other
freshwater terrapins (Clark and Gibbons, 1969;
Georges, 1982; Chessman, 1986), vary from
carnivorous to omnivorous depending on habi-
tat, ontogenic stage or other factors. Indeed
in Camargue, faeces of juvenile E. orbicularis
were for the majority composed by animal re-
mains, whereas those of adults contained large
quantity of plant matter. These results must
be interpreted with precaution, given the small
sample size, but are consistent with those from
Tuscany, Central Italy (Lebboroni and Chelazzi,
1991). It is often difficult to determine whether
plant matter is ingested incidentally with ani-
mal prey or is a primary food item (Lindeman,
1996). However, its relatively high frequency
of occurrence and percentage of abundance by
weight in adult samples allow us to consider that
plant matter was intentionally ingested.
In spring, adult terrapins inhabit principally
freshwater marshes, and it is likely that the
higher productivity of these temporary habitats,
compared to that of permanent waters (Swason
and Meyer, 1977; Danell and Sjoberg, 1982;
Crome 1986), combined with the absence of fish
competition for trophic resources, offer to ter-
rapins the best environment to carry out their
activity patterns (i.e. feeding, mating, basking
and floating). Our study showed that terrapins
were principally carnivorous during this period,
and that they ingested plant matter incidentally.
When temporary marshes dry out, generally at
the end of June, terrapins can undergo aesti-
vation, as observed in Dordogne by Naulleau
(1991), or move to irrigation canals as observed
on Tour du Valat estate (Olivier unpublished
data). Starting from this period until August
the consumption of plant matter (i.e. algae and
macrophyta) and also terrestrial invertebrates
increased. This phenomenon was already ob-
served by Clark and Gibbons (1969) in juveniles
of another Emydidae, Trachemys scripta.They
proposed different factors that may explain the
increase of plant consumption: a greater diffi-
culty in obtaining insects later in the season,
a decreased abundance of insects, or the sat-
isfaction of nutritional requirements with plant
matter. Our results suggest that E. orbicularis
shifts its diet from carnivorous to omnivorous
depending on different habitat uses probably
564 Short Notes
Tab l e 1 . Percentage of abundance by number (%A) and frequency of occurrence (%F) of prey items in faecal samples of
Emys orbicularis:Ad=adult, L =larvae.
%A %F
Adults Juveniles Adults Juveniles
(N =27)(N=4)(N=27)(N=4)
MOLLUSCA Tot. 18.7 12.5 37.0 25.0
Gastropoda 18.7 12.5 37.0 25.0
Bithyniidae (Bithynia sp.) Ad 2.3 0.0 11.1 0.0
Lymnaeidae (Galba sp.) Ad 4.1 0.0 7.4 0.0
Physidae (Physella sp.) Ad 9.6 9.4 25.9 25.0
Planorbidae Ad 2.3 3.1 7.4 25.0
Undetermined remains Ad 0.4 0.0 7.4 0.0
ARACHNIDA Tot. 1.0 3.1 7.4 25.0
Acarina Ad 0.5 0.0 3.7 0.0
Araneae Ad 0.5 3.1 3.7 25.0
CRUSTACEA Tot 14.1 0.0 66.7 0.0
Conchostraca Ad 6.3 0.0 11.1 0.0
Decapoda Cambaridae Ad 7.8 0.0 66.7 0.0
(Procambarus clarkii)
INSECTA Tot 65.7 84.4 88.9 100.0
Coleoptera 40.2 25.0 55.6 25.0
Dytiscidae L 4.1 0.0 7.4 0.0
Dytiscidae Ad 12.8 18.7 44.4 25.0
Hydrophilidae L 4.1 0.0 11.1 0.0
Hydrophilidae (Berosus sp.) Ad 18.7 6.3 22.2 25.0
Noteridae Ad 0.5 0.0 3.7 0.0
Diptera 0.9 0.0 7.4 0.0
Chironomidae L 0.5 0.0 3.7 0.0
Unidentified Ad 0.4 0.0 3.7 0.0
Heteroptera 15.0 3.0 25.9 25.0
Corixidae (Corixa sp.) Ad 13.7 0.0 14.8 0.0
Notonectidae (Notonecta sp.) Ad 0.9 3.0 11.1 25.0
Pleidae (Plea sp.) Ad 0.4 0.0 3.7 0.0
Hymenoptera Formicidae Ad 3.2 31.3 11.1 75.0
Odonata 5.0 18.8 37.0 50.0
Aeshnidae L 1.4 0.0 11.1 0.0
Coenagrionidae Ad 1.4 15.7 14.8 50.0
Libellulidae L 0.4 0.0 3.7 0.0
Libellulidae Ad 1.8 3.1 11.1 25.0
(Crocothemis erythraea)
Trichoptera L 0.5 0.0 3.7 0.0
Unidentified Insecta 0.9 6.3 7.4 50.0
VERTEBRATA Undetermined remains 0.5 0.0 3.7 0.0
PLANT Undetermined remains 88.9 25.0
Unidentified organic matter 25.9 75.0
linked to differences in prey availability.Further
investigation and more data are needed to test
our hypothesis and to explain whether dietary
shifts of E. orbicularis in Camargue are linked
to different seasonal nutritional requirements, to
different habitat uses, or to differences in prey
availability. Vertebrate prey were rare in the fae-
ces, although amphibian larvae were regularly
observed during our sampling campaign, espe-
cially in freshwater marshes (Ottonello pers.
obs). Tadpoles and eggs could be preyed upon
by terrapins, as observed in northern Europe
(Skibinski, 1954), but would go undetected in
faeces due to complete digestion (Demuth and
Buhlmann, 1997).
Another important finding is that the exotic
red swamp crayfish Procambarus clarkii was
the most frequent prey at the study site. In-
Short Notes 565
deed, pond terrapins actively preyed on live
crayfish, as some terrapins were observed eating
red swamp crayfish in the wild (Ottonello pers.
obs.). This result may be explained by the recent
proliferation of this crustacean in most freshwa-
ter habitats of Camargue (Rosecchi et al., 1998).
This introduced crayfish is now food of many
birds, mammals and fish in different parts of Eu-
rope according to Geiger et al. (2005), who did
not quote any reptile. Therefore our study ads a
new species to their list of vertebrate predators.
Several methods have been suggested to con-
trol P. clarkii, as this invasive species is consid-
ered as a plague, in particular in Mediterranean
wetlands (Gutierrez-Yurrita and Montes, 1999;
Gherardi and Holdich, 1999). Our study sug-
gests that at least in Camargue, this alien species
could be limited by the natural predation ex-
erted by Emys orbicularis, a threatened native
species.
Acknowledgements. This study was supported by the
Sansouire Foundation (Biological Station “Tour du Valat”)
and by the European financial contribution “Leonardo Da
Vinci II” awarded by Commett Li.Sa. to Dario Ottonello.
We are grateful to Jean Oison and Anthony Olivier for their
help during sampling.
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... In particular, we wanted to test whether differences in the diet of E. orbicularis exist 129 between (i) month (temporal diet), (ii) populations (spatial diet), (iii) males and females 130 and (iv) adults and juveniles; early studies suggest that the diet of juvenile and adult 131 turtles from Emydidae family are different, with juvenile turtles being more carnivorous 132 (Clark and Gibbons, 1969;Hart, 1983;Ottonello et al., 2005). Thus, we hypothesized 133 that juveniles were more carnivorous than adults. ...
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Molecular technologies, such as metabarcoding, have become powerful tools for conservation purposes. Here, we present a non-invasive study analyzing the diet of one population of European pond turtle (Emys orbicularis) during its whole activity period and of four other populations during the same period, based on faecal sample, and using for the first time on this species, a long metabarcoding approach. Emys orbicularis is an emblematic freshwater species of wetlands in Europe. In several countries, this species is endangered and, in Switzerland, Emys orbicularis is ranked as critically endangered on the Swiss Red List. A national conservation program was created to reintroduce this species and raised the question if this reintroduced species could be a threat for other endangered species. We developed a new method of long metabarcoding analysis, using universal PCR primers to determine prey species occurrence in the faeces. The analysis conducted on 174 faeces collected on 142 individuals revealed 1153 preys from 270 species. Emys orbicularis consumed plants throughout the year with a more diverse diet during the reproduction period (April- June). This study therefore not only determines precisely the omnivorous and opportunistic diet of the Emys orbicularis, but also shows that this species is not a threat to its environment, as 85.5% of the consumed species were not list on the Swiss Red List. Moreover, it also demonstrated that the genetic analyses of faeces could be an efficient tool to determine trophic interaction with a high level of precision, yielding promising perspectives for food web ecology.
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... En la región del sur de Francia, Ottonello et al. (2005) comprobaron que había un cambio estacional en la alimentación, ya que en primavera se alimentaban de invertebrados y en verano realizaban una mayor ingesta de materia vegetal. Este patrón también se produce en las poblaciones ibéricas, como las que se encuentran en las charcas de Gándaras de Budiño (Pontevedra) que se alimentan de forma considerable de los frutos de los nenúfares (Cordero et al., 2008b). ...
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Insekten sind die artenreichste Tiergruppe auf der Erde. Es ist derzeit rund eine Million Arten bekannt, das entspricht mehr als 60 % aller Tierarten. Sie sind formen- und farbenreich, haben eine Vielzahl an Ernährungs- und Verhaltensweisen hervorgebracht und sind für den Menschen von großer Bedeutung. Das sogenannte „Insektensterben“, ein dramatischer Rückgang der Insektenbiomasse (und der Individuenzahlen) hat in den letzten Jahren für große Aufmerksamkeit gesorgt. Die Zahl der in Österreich vorkommenden Insektenarten wird auf rund 40.000 geschätzt. Während die Zahlen für besser bekannte Insektengruppen (z. B. Schmetterlinge, Heuschrecken, Libellen) sehr zuverlässig sind, sind die Angaben für einige artenreiche Insektengruppen (z. B. Fliegen, Hautflügler) nur Schätzwerte. Rund 345 Insektenarten gelten als in Österreich endemisch, d. h. sie kommen weltweit nur hier vor. Für jene endemischen Insektenarten, die über der Baumgrenze leben, gilt der Klimawandel als wesentlicher Gefährdungsfaktor. Umgekehrt führen Klimawandel und Globalisierung zu einem Anstieg der Artenzahlen in Österreich, wobei beide Faktoren vor allem relativ anspruchslose „Allerweltsarten“ begünstigten. Folgende Ökosystemleistungen von Insekten sind von besonderer Bedeutung: die Bestäubung, die Schädlingskontrolle, ihre Rolle als Nahrungsgrundlage für terrestrische Wirbeltiere und die Honigproduktion. Insekten spielen eine negative Rolle als Krankheitsüberträger oder Schädlinge in der Land- und Forstwirtschaft. Der Kenntnisstand von Verbreitungsdaten zu den Insektengruppen in Österreich ist heterogen. Der Schwerpunkt von GBIF-Austria1 liegt auf Schmetterlingsdaten, Verbreitungsatlanten oder vergleichbare Publikationen liegen nur für einige (populäre) Gruppen vor, und fehlen für die meisten Insektengruppen. Die Biodiversitätsarchive Österreichs (wissenschaftliche Belegsammlungen) sind unterdotiert. Um aktuellen Ansprüchen gerecht zu werden, sind Investitionen erforderlich, insbesondere hinsichtlich der Digitalisierung der Daten. Bestehende Monitoringprogramme (z. B. FFH-Richtlinie, Wasserrahmen-Richtlinie, BINATS2, ÖBM3-Kulturlandschaft) decken einen kleinen Teil der Insektenvielfalt ab, standardisierte, langfristig gesicherte Freiland-Erhebungen fehlen jedoch. Im schulischen und universitären Bereich sind Anstrengungen erforderlich, die organismische Biologie zu stärken und damit auch eine Grundlage für das Verständnis und die Akzeptanz von Schutzbemühungen zu schaffen. Bürgerwissenschaften (Citizen Science) können hier einen Ansatzpunkt bilden, eine wissenschaftliche Grundlage aber nicht ersetzen. 1 GBIF-Austria ist eine vom Bundesministerium für Klimaschutz, Umwelt, Energie, Mobilität, Innovation und Technologie geförderte Initiative österreichischer naturwissenschaftlicher Institutionen und Vereine. Ziel der Initiative ist es, Daten zur heimischen Artenvielfalt in großem Umfang über das Internet zugänglich zu machen und somit die internationale GBIF-Initiative auf nationaler Ebene umzusetzen (www.gbif.at). 2 Biodiversity – Nature – Safety 3 Österreichisches Biodiversitäts-Monitoring Insektenarten in Österreich Rolle der Insekten im Ökosystem relativ geringer Kenntnisstand Insekten in Österreich – Zusammenfassung 6 Umweltbundesamt  REP-0739, Wien 2020 Rückgänge von Insektenpopulationen wurden schon ab den 1990er-Jahren (bzw. viel früher) festgestellt. Mit der „Krefeld-Studie“ in Deutschland im Jahr 2017 rückte das Thema in den Fokus sowohl der Wissenschaft als auch einer breiteren Öffentlichkeit. Die Ursachenforschung gestaltet sich jedoch aufgrund der komplexen Zusammenhänge und der wenigen belastbaren Langzeituntersuchungen schwierig. Regionale Studien und Erklärungen für den lokalen Rückgang von Insektenpopulationen sind nicht in der Lage, ein offenbar globales Phänomen ausreichend zu erklären. Zu den übergeordneten Faktoren, die zum Insektensterben beitragen, zählen  Verlust an Lebensraum,  Verschlechterung der Lebensraumqualität, insbesondere durch Verlust von Lebensraumstruktur,  Klimawandel,  Insektizide,  Schadstoffeinträge, insbesondere flächendeckende Stickstoffeinträge,  Lichtverschmutzung,  gebietsfremde Arten,  Fragmentation der Landschaft und  Metapopulationsdynamik. Insektensterben ist ein komplexes und multifaktorielles Phänomen. Es ist nicht zu erwarten, dass es nur eine einzige Hauptursache für den Biodiversitätsverlust auf allen räumlichen Skalen und funktionellen Ebenen gibt. Für Österreich liegen keine quantitativen Daten vor, die einen Insektenrückgang belegen oder widerlegen könnten. Indizien, insbesondere lokale Studien und Gefährdungsanalysen (Rote Listen) lassen aber keinen Zweifel, dass die Rückgänge in Österreich stattgefunden haben und stattfinden. Auch wenn für viele Insektengruppen keine aktuellen Gefährdungsanalysen vorliegen, zeigen die vorhandenen Daten übergeordnete Bedrohungsbilder: Besonders gefährdet sind Insektenarten in ostösterreichischen Offenlandstandorten sowie Arten von natürlichen Fließgewässer-Uferstandorten, Feuchtwiesen, Quellen und Mooren. Es besteht hoher Forschungsbedarf, insbesondere die komplexen Ursachen für das Insektensterben betreffend. Es liegen jedoch genügend Informationen vor, um bereits jetzt Maßnahmen einzuleiten und umzusetzen, die die Gefährdung der Insekten in all ihrer Vielfalt und in ihrer ökologischen Leistungsfähigkeit reduzieren. Die gesellschaftliche Aufgabe besteht darin, Handlungsoptionen auszuloten, konkrete Maßnahmen für diese Erfordernisse auszuarbeiten und diese gemeinsam mit allen administrativen Organen und Interessengruppen sowie einer interessierten Öffentlichkeit umzusetzen.
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Based on a review and our own data, we present an overview of the ecological impacts on the trophic web of Mediterranean wetlands by an introduced Decapod Crustacean, the red swamp crayfish (Procambarus clarkii). P. clarkii lacks efficient dispersal mechanisms but is very well adapted to the ecological conditions of Mediterranean wetlands (fluctuating hydroperiods with regular intervals of drought). As an opportunistic, omnivorous species, which adapts its ecology and life history characteristics, such as timing and size at reproduction to changing environmental conditions, it became readily established in most of the Mediterranean wetland environments. High reproductive output, short development time and a flexible feeding strategy are responsible for its success as an invader. Like most crayfish, it occupies a keystone position in the trophic web of the invaded system and interacts strongly with various trophic levels. It e ciently grazes on macrophytes and is one of the main factors, besides the impact of flamingos, cattle and introduced fish, of the change of many water bodies from a macrophyte dominated, clear water equilibrium to a phytoplankton driven turbid water balance. Juveniles feed on protein rich animal food with the corresponding impact on the macroinvertebrate community in competition with other crayfish or fish species. At the same time, it serves as a prey for mammals, birds and fish. Due to its predatory and grazing activity, it efficiently canalises energy pathways reducing food web complexity and structure. Feeding also on detritus it opens, especially in marshlands, the detritic food chain to higher trophic levels which results in an increase of crayfish predators. As a vector of diseases, it has a severe impact on the preservation and reintroduction of native crayfish. P. clarkii accumulates heavy metals and other pollutants in its organs and body tissues and transmits them to higher trophic levels. Due to the long history of its presence, the complex interactions it established within the invaded ecosystems and the socio-economic benefits it provides to humans, prevention and control seem the most promising management measures to reduce the negative impact of this crayfish species.
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I conducted a comparative analysis of life-history attributes of two populations of painted turtles (Chrysemys picta) in the inland Pacific Northwest. A population inhabiting three wastewater lagoons contained proportionately more juveniles than one inhabiting a lake on a wildlife refuge. Average fecundity was significantly higher in the wastewater lagoon population (15.8 vs 13.4 eggs/clutch). Minimum size at the onset of sexual maturity was similar in the two populations for males and females (approximately 90 mm and 160 mm plastron length, respectively). However, turtles grew more rapidly and reached these sizes at younger ages in the wastewater lagoons (two years in males and 6-7 years in females) than in the lake population (three years in males and probably 8-10 years in females). These results contrast with local variation in the timing of maturity described for Trachemys scripta, for which females in populations of fast-growing turtles matured at the same age but at a larger body size with a concomitant increase in clutch size. The difference may be related to a contrast in the two species' clutch size-body size correlation, which is greater for T. scripta than C. picta. Interpopulational differences in fecundity and growth rate may have been related to caloric content and consistent seasonal availability of chironomid larvae and pupae fed upon heavily by the turtles in the waste-water lagoons. Lake turtles fed heavily upon odonate larvae in the early and middle active season, and on amphipods throughout the year. Comparison of the two study populations corroborates earlier reports of enhanced life-history parameters for C. picta in habitats that are nutrient enhanced by anthropogenic activity. Both study populations fit intraspecific patterns of increased clutch size and body size and later maturity for C. picta at more northern latitudes and higher elevations. The highly carnivorous diet of both populations, atypical for this species, may result in the relatively large body sizes and clutch sizes observed.
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A dietary change occurs from youth to maturity in the turtle Pseudemys scripta in South Carolina. Juveniles in their first year of growth were primarily carnivorous whereas adults were largely herbivorous. The shift from a carnivorous to a herbivorous diet occurred over the course of one summer. A positive correlation between the calcium content of the shell and size of the turtle is demonstrated. The food of juveniles contained a significantly higher percentage of calcium than the food of the adults.
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[Inventories of Crustacea and more generally aquatic invertebrates in the Camargue (Rhône Delta) have mainly involved Copepoda, Ostracoda, and Cladocera. Data on Decapoda have most often been collected in general faunal surveys and remain fragmentary, and this group has not been the subject of any special study. Over the period 1988-96, eleven species of Decapoda were recorded from fresh and brackish water in the eastern part of the Camargue. For two of these: Penaeus kerathurus (ForskÅl, 1775) and Palaemonetes varians (Leach, 1814) this study is the first published record for the region. The temporal trends and the habitat distribution of the various species, together with factors influencing this distribution, the migrations within the Camargue hydrosystem, and the arrival of introduced species are discussed., Inventories of Crustacea and more generally aquatic invertebrates in the Camargue (Rhône Delta) have mainly involved Copepoda, Ostracoda, and Cladocera. Data on Decapoda have most often been collected in general faunal surveys and remain fragmentary, and this group has not been the subject of any special study. Over the period 1988-96, eleven species of Decapoda were recorded from fresh and brackish water in the eastern part of the Camargue. For two of these: Penaeus kerathurus (ForskÅl, 1775) and Palaemonetes varians (Leach, 1814) this study is the first published record for the region. The temporal trends and the habitat distribution of the various species, together with factors influencing this distribution, the migrations within the Camargue hydrosystem, and the arrival of introduced species are discussed.]