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Chapter 38. Living ostracods from the nature reserve “Hordter Rheinaue” (Germany)

Chapter 38. Living ostracods from the nature reserve “Hordter Rheinaue” (Germany)

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502 B.W. SCHARF



TEXT-FIG.

l-Nature reserve “HOrdter Rheinaue”. Dynamics of the meander and drying up of the meanderbelt (from Kinzelbach, 1976).



bow-lakes in the wet meander-belt while in the dry meander-belt we find running water, gravelpits, loam-pits and oxbow-lakes (Text-fig. 2 and Table 1).

A detailed description of the nature reserve “Hordter Rheinaue” and its waters is given in

Kinzelbach (1976) and Scharf and Kinzelbach (1976). For the vegetation in the individual localities see Dannapfel (1977), for the habitat of the localities studied see Scharf (1976).

Nearly all the waters are formed by the meandering Rhine river. Today some exist as separate

oxbow-lakes and others are part of the Michelsbach creek (see Text-figs. 1 and 2). Most of the

waters are surrounded by forest. Only the oxbow-lake “im alten Dorf” (No. 1 in Text-fig. 2) and the

“Altgraben” creek (No. 9) are situated between meadows and cultivated fields.

All the waters studied are shallow, i.e. less than 2 metres deep. Only the gravel-pits have a

depth of up to about 10 metres.



503



TEXT-FIG.

arebnc



ken monthly



504

I



UI



c)



.-



5



f?



??



puddle

Bollenkopf

Altrhein

Altrhein

Fischerhuttenrhein

Fischerhiittenrhein

Altrhein

Brennrhein

Sondernheimer Altrhein

Bollenkopf

Suhle

Brennrhein

made 1975, south

made 1975, north

made about 1971

made about 1940

made about 1968

Bananensee

Herrengrund

Mehlfurt, in the deep

Mehlfurt, gravel-margin

Mehlfurt, clay-margin

triangular gravel-pit

Sondernheimer Altrhein

Brand-Graben, mouth

Brand-Graben, middle

Brand-Graben, spring

Alt-Graben

Michelsbach

Michelsbach

flood-plain of Michelsbach

wet alder wood

Schlute

Schlute

drainage ditch

"im alten Dorf"



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506 B.W. SCHARF



The puddle (No. 36) dries up in each warm weather period. The Schlute (No. 3), the wet alder

wood (No. 5), probably the flood-plain of Michelsbach (No. 6), the Brennrhein (No. 29) and the

Altrhein (No. 34) dry up each summer. The Brennrhein (No. 25) was without water in the warm

summer of 1969. Normally a small amount of water remains in the oxbow-lake Brennrhein (No.

25) during summer.



METHODS

The methods of catching ostracods, of separating them from the substrate and preparing the

animals are d x r i b e d by Scharf (1976 and 1980).

In the period from April 1976 to March 1977 half of the localities were collected monthly (see

Table 1 and Text-fig. 2). Later on the other ones were visited. Between April and May 1985samples

were taken from localities 1-3, 14 and 28-35.

Dr. K.H. Dannapfel was kind enough to provide the sample from locality 28. This was a dry

mud sample so it was not possible to distinguish between living and subfossil animals.



RESULTS

AND DISCUSSION

List of the Ostracods Found

The list of the species which were found in the different localities of the “Hordter Rheinaue” is

given in Table 1. It distinguishes between living and subfossil/fossil occurrences. Under “living”

are placed all living animals or those that have just died, i.e. the muscles have not yet decayed. The

term “subfossil” is applied to all those animals whose remains are only a few years old, “fossil”

to those that are older. Often it is not possible to distinguish between subfossils and fossils.

Subfossil valves are examined to see if there are further species that have not been caught before

because of it being the wrong season. Sometimes the relation between living and subfossil animals

can be an indication of a specific biotope as will be seen later.

In the “Hordter Rheinaue” living specimens of 39 ostracod species were found and will be

figured in Scharf (in prep.). Among these species are some that are rarely found in Germany, for

example: Zlyocypris tuberculata, Candona weltneri var. obtusa, C. hartwigi, C. sarsi, C. wegelini,

C. caudata (only subfossil found in the “Hordter Rheinaue”), C. hyalina, Cypria lacustris, Notodromas persica and Zsocypris beauchampi. In the “Hordter Rheinaue” no new species nor any

species new to Germany were found.

The most frequently found species are given in Table 2. They are all common species.

TABLE

2-THE



MOSTFREQUENTLY

FOUND OSTRACODS



Cypria ophtalmica

Candona candida

Cypridopsis vidua

Physocypria kraepelini

Candonopsis kingsleii

Herpetocypris reptans

Candona albicans



number of localities

occurrences

living

subfossil

23

3

21

6

18

5

14

2

12

2

9

3

9

3



Living Ostracodafrom “Hordter Rheinaue



‘I



J



F



M



A



M



J



J



A



S



O



N



507



D



Herpetocypris reptans

Cypridopsis vidua

Candona neglecta



on



Candona hya Iina

Ca ndona hart wig i



0



Candonopsis kingsleii



0



llyocypris tuberculata



No todromas persica

Candona candida

~



~



~~



~



~~



TBXT-FIo. 3-Population distribution characteristics of some ostracods from the “Htirdter Rheinaue”.

m:adults, 0: instars. The gaps in February and August are due to the fact that there were no collections.



Phenology (Population Structure)

About 190 samples from different localities in various months were taken in the “Hordter

Rheinaue”. It is not possible to give the population structure characteristics of many species.

Some of the reasons for this are:

-Often only a few specimens were found so that it is not possible to make a reliable statement

because of the small numbers.

-The sediment was washed on a 250 pm mesh so that often many instars were not caught.

-In some localities adults and juveniles were found whereas in other localities only adults were

caught. For example: In the small running water Brand-Graben (Nos. 10-12) Cypria ophtalmicu

was present not only as adults but also as instars. However, only adults of the same species were

found in the oxbow-lakes Brennrhein (No. 25) and BGllenkopf (No. 27). It may be that the instars

are in the deeper parts of the bigger lakes. Mallwitz (1984) observed the same feature with other

species in some lakes in North-Germany.

In spite of these difficulties it is possible to give the population distribution characteristics of

some species (Text-fig. 3). Adults and juveniles of Herpetocypris reptans are present practically

throughout the year. Adults of Cypridopsis vidua were found all the year round, but instars only

in the summer time. This species is very frequent in the warm season while the adults are rare in

winter. The adults were caught much more frequently than the juveniles. Therefore it is possible

that thew are instars in winter time (compare Mallwitz, 1984).

Candona neglecta, C. hyalina, C . hartwigi and Notodromas persica have only one generation a

year in the “Hordter Rheinaue”. The adults appear in different months (Text-fig. 3). The population structure of Candonopsis kingsleii is similar than that of Candona hartwigi but it seems that C.

kingsleii has a further one or more generations in the early summer time. Ilyocypris tuberculutu

appears only during the warm period and it is not possible the give the number of generations a

year.

Candona candida seems to be a species with several generations in the year. However, this is

not coqect as Text-fig. 4 shows. In this figure the development of the Candona candida-population



TABLE

3-POPULATION DENSITY

OF OSTRACODA. AN kI"EMPT



Darwinula stevensoni

Candona balatonica

Ilyocypris gibba



TOGETHER

WITH 'THE DATA

OF THE "H~RDTER

RHEINAUE"

pop. density

remarks

reference

specimens/m2

57

Tressler (1957), cit.

in Thaler (1977)

up to 7.7 % of benthic

Ponyi (1966)

up to 0.8 % Crustacea

up to 1.5%



Lake Constance,

Germany



Cypria ophtalmica

Cytherissa Iacustris



up to 1,500,000

upto 100,000



Ltiiller (1969)



mesotrophic

GuU-Lake, Michigan,

USA

Balaton, partim in the

area of a sewage-idow,

Hungary



Darwinula stevensoni



up to about 8,000



McGregor (1969)



Cypridopsis vidua

Limnocythere inopinata

Cyclocypris ovum

Ilyocypris bradyi

Cypridopsis newtoni

Candona spec.

Darwinula stevensoni

Isocypris arnoldi



up to

up to

up to

up to

up to

up to

upto

upto



vordere Finstertaler

See, high mountain

region of Austria

Laguna de Magalhaes,

lagoon in the tropical

savanna of NorthBrasil

Loch Leven, U.K.



Cypria ophtalmica



about 7,000



outflow region



Ostracoda



lake

ol igotrophic

Gerat Lake, Canada

BaIaton, Hungary



species



Ostracoda, not speciiied



AT A REVIEW



16,800

6,600

3,900

2,300

2,100

2,000



up to 39% ostracods in

relation to total benthic

Crustacea



Ponyi et al. (1971)



mean biomass: 44 mg/mz



Bretschko (1972), cit.

in Thaler (1977)



relative abundance: 2.4%



Reiss (1973)



mean annual biomass:

100 mg/m2



Maitland and Hutspith

(1974), cit. in Thaler (1977)



up to 348 mg/m2 dry weight

up to 14.78 % of total dry wt.

up to 235 mg/m2dry weight

up to 0.072 % of total dry wt.

up to 68 mg/m2dry weight

up to 0.27 % of total dry wt.



Junk (1975)



800



400



45



Ostracoda

up to 13,390



central region



up to 9,015



littoral region of water

reservoir Bung Borapet,

Thailand



up to 26,246



m



TVBLE3-Continued



TABLE

3-POPULATION DENSITY

OF OSTRACODA. AN kI"EMPT

lake

lake

7 different lakes in

central

Amazonian region

ol igo

trophic

(black

water,

blended

Gerat

Lake,

Canada

watersHungary

and white water)

BaIaton,

Brad

eutrophic

Piburger See, Austria

Lake Constance,

Germany



mesotrophic

GuU-Lake, Michigan,

USA

Balaton, partim in the

area of alakes

sewage-idow,

eutrophic

Schmalsee, mud,

Hungary

North Germany

Schmalsee, sand,

North Germany

Liittauer

See, rhizoms

vordere

Finstertaler

of reed

detritus

See,

highwith

mountain

NorthofGermany

region

Austria

H6rdterdeRheinaue

Laguna

Magalhaes,

gravel-pit

Mehlfurt,

lagoon

in the

tropical

(15)

clay-margin

savanna

of NorthBrasil-Graben,

Brand

(10)U.K.

spring

Loch

Leven,

Sondemheimer

Altrhein

(13)

outflow

region

gravel-pit

Herrengrund

central

region (18)

loam-pit (21)

littoral

region of water

Brand-Graben,

reservoir

Bung Borapet,

mouth (12)

Thailand

Brennrhein (25)



species

species

Ostracoda



Darwinula stevensoni

Candona balatonica

Cypria ophtalmica

Ilyocypris

gibba

Cypria ophtalmica

Candona candida

Cytherissa

Iacustris

Darwinula stevensoni

Cypridopsis vidua

Cypridopsis vidua

Ostracoda inopinata

Limnocythere

Ostracoda ovum

Cyclocypris

Ilyocypris bradyi

Cypridopsis newtoni

Candona

spec.

Ostracoda

Darwinula stevensoni

Isocypris arnoldi



Ostracoda

Cypria

ophtalmica

Ostracoda, not speciiied

Cypridopsis vidua

Potamocypris variegata

Candona candida

Cyclocypris laevis

Ostracoda

Cypria ophtalmica

Physocypra kraepelini

Ostracoda

Cypridopsis vidua

Cypridopsis vidua

Cyclocypris ovum

Cypria ophtalmica

Candona candida



TOGETHER

WITH 'THE DATA

OF THE "H~RDTER

RHEINAUE"

pop. density

remarks

reference

specimens/mz

pop.

density

remarks

reference

specimens/m2

mean annual abundance:

Reiss (1976)

0.3-63 weight ”/,

57

Tressler (1957), cit.

(average: 51 %j

in Thaler (1977)

up to 7.7 % of benthic

Ponyi (1966)

up to 0.8 % Crustacea

Thaler (1977)

rnato

x.1.5%

biomass: 2,800 mg/m2

m a . : 250,000

up

mean annual biomass:

mean annual pop.

1,500 mg/m*

density:

130,000

up

to 1,500,000

Ltiiller (1969)

max. biomass: 190 mg/m2

max.: 100,000

3,600

upto

mean annual biomass: 50 mg/mz

mean annual pop.

max. biomass: 42 mg/m2

density:

up

to about3,000

8,000

McGregor (1969)

mean annual biomass: 15 mg/m’

max.: 1,900

mean annual pop.

density:

up to 39% ostracods in

Ponyi et al. (1971)

up

to 16,800 500

Wetzel(l984)

> 50.000

up

to 6,600

relation to total benthic

Mallwitz (1984)

(in

this paper the percentage

m ato. : 3,900

140,500

up

Crustacea

of each species at the three

mean

up

to annual

2,300

localities is given)

44,000

density:

up

to 2,100

up

m to

a . : 2,000

43,700

umean

p t o annual

800

udesnity:

p t o 400

8,000



m



AT A REVIEW



max.: 7,000

4,670

about

mean annual

density: 3,000

45



up to 3,440

upto 800

up to 2,800

up to 820

up to 530

uptoto13,390

1,400

up

u p t o 940

up to 9,015

upto 940

upupto

to 26,246

910

upto 660

UDtO

. - 900

-



mean biomass: 44 mg/mz



Bretschko (1972), cit.

in Thaler (1977)



relative abundance: 2.4%



Scharf (this paper)

Reiss (1973)



mean annual biomass:

100 mg/m2



Maitland and Hutspith

(1974), cit. in Thaler (1977)



up to 348 mg/m2 dry weight

up to 14.78 % of total dry wt.

up to 235 mg/m2dry weight

up to 0.072 % of total dry wt.

up to 68 mg/m2dry weight

up to 0.27 % of total dry wt.



Junk (1975)



VI



d



\b



510 B.W. SCHARF



BRANDGRABEN ( stream )



Candona candida



100

%



50

0



J



M



A



J



A



0



5



N



BRENNRHEIN ( oxbow - lake)



-



20--/



-



-



-



0



10

0.



M



Candona candida



>

O-----E



I



J



HIGH

WATER



ICE



I



J



A



M



F



b



I



I



A



D

J

1976 1977



S



I



I



0



N



J

D

1976 1977



F



M



TEXT-FIG.

4-Population distribution of



Cundonu cundidu and temperature in two localities of the “H6rdter Rheinaue”. A = adults, A-1 = ultimate larval stage, A-2 = penultimate larval stage and so on.



in Brennrhein (No. 25) is compared with that of the Brand-Graben (No. 12). The water of the shallow oxbow lake is warm in summer and cold in winter while the water of the Brand-Graben

stream is, in relation to the temperature, more equable. One can see that the percentage of the

penultimate larval stage A-2 increases until July and after that decreases. With the decrease of

A-2 in the autumn the percentage of the last larval stage and of the adults increases. The comparison shows that the development is more synchronized in the oxbow lake than in the stream,

probably because of the temperature. In the stream there are more development-stages at one time

and each single stage is to be found over a longer period than in the oxbow lake. Candona candida

has only one generation per year in the “Hordter Rheinaue”.

Density of Population

There is little data on the density of ostracod populations in the literature. An attempt has been

made to compile the available data and this is given in Table 3. Wetzel (1984) in summary states

that the individual density ranges from an average of 57 m-2 in the oligotrophic Great Slave Lake

to about 10,OOO m-2 in a mestrophic lake and finally to > 50,000 mw2in an eutrophic lake.

The ostracods form a great part of the biomass in some lakes. For example 64% of the total

dry weight of biomass in the depths of Lago TupC in the central Amazonian region are ostracods

(Reiss, 1976). Chaoboridae, Hydracarina and Ostracoda can be considered as the common stock



number of locality

Limnocythere inopinata

Darwinula stevensoni

Ibocypris bradyi

I. gibba

I. tubercdata

Candona candida

C.neglecta

C. weltneri var. obtusa

Candona hartwigi

C. mrchica

Candona albicans

Candona fabaeformis

Candona hyalha

C.protzi

Candonopsis kihgsleii

Cyclocypris laevis

C. ovum s. Klie

C.ovum s. Petkovski

Cypria lacustris

C.ophtalmica

Physocypria kraepelini

Notodromas persica

Eucypris zenkeri

Isocypris beauchampi

Herpetocypris reptans

Dolerocyprisfmciata

Cypridopsis vidua

Potamocypris variegata

mean annual density (n/mz)



7



8



10



12



13



sr

d



15



16



18

sr



sr



19



20



21



26



sr

26



r



sr

sr



sr

d



r



d

13



r



47



r



45



sr



r



28



81



64



r



11



sr



sr

sr



d



25



27



95



sd



22



r



38



d

d



sr

sr



r



sr



sr



sr



sr



sd



17



34



sr



sd

25

62



sr



sr



sr

sd



sr

16



22



26



sr

75

r

219



56

sd

148



d



18

20



sr



sd

r



sd



sd



sr



sr



sd



sd



80

d

438 1427



45



73



30



400



59



13

66



139



189



~



90



24



55



15 1207 1140



The percentage of the eudomiaant (> 10%)species is given in each case. d = dominant (10-5%),

sr = subrecedent 1%).



(<



r



sr



r



r



23



sd



d



sr



22

15



r



100



100



8



28



r

438



370



sd = subdominant (5-2%), r = recedent (2-1 %),



c.



512 B.W. SCHARF



of the macrobenthic fauna of central Amazonian lakes (Junk, 1973; Fittkau et al., 1975). The large

population density suggests that their role could sometimes be considerable in the metabolism of

lakes.

Such great numbers of ostracods as those given in the literature were not found in the waters of

the “Hordter Rheinaue” The biggest mean annual density was found in the Brand-Graben (Nos.

10 and 12) and in the clay margin of the gravel-pit Mehlfurt (No. 15). In the Brand-Graben Candona candida. Cypria ophtalmica and Cyclocypris laevis or else C . ovum were the most abundant

individuals. Leaves of alder and beech were predominant as organic material while in the gravel-pit

reed mace and its mud serve as a basis for the food of Cypridopsis vidua.

Certainly the absence of fish is a large factor in the relatively large number of ostracods in the

Brand-Graben. The population of Candona candida is reduced drastically by fish in the Piburger

(Thaler, 1977).

The lowest mean annual density of ostracods was found in Michelsbach (No. 8), at the gravelmargin of the gravel-pit Mehlfurt (No. 16) and in the youngest loam-pits (Nos. 23 nad 24) (Table

4). In each of these localities the content of organic material in the sediment is much smaller than

at the other localities.

Cypria ophtalmica, Physocypria kraepelini and Cypridopsis vidua are small and good swimmers.

Table 4 shows that they are not evenly distributed. One of the three species is always much more

numerous than the other two species. C. vidua seems to occupy the waters with submerged water

plants more successfullythan P. kraepelini or C . ophtalmica. For comparison, in the volcanic lakes

of the Eifel-region C. vidua lives in the belt of submerged water plants, C. ophtalmica prefers the

depths of the lakes and P . kraepelini is absent in these volcanic lakes (Scharf, 1980; Kempf and

Scharf, 1980).

Species Frequency in Relation to the Drying up of the Waters

In the “Hordter Rheinaue” there are only a few waters with many ostracod species. These are

the localities numbered 1 , 4, 27, 33, 7, 19 and 13 in Table 1. With the exception of the gravelpit Bananensee (No. 19) all the waters mentioned are oxbow lakes and they have never dried up

hitherto. All of these are deep enough to ensure that the ice in winter does not reach the bottom.

There are only very few species in the ephemeral waters or waters which rarely dry up such as

the localities numbered 36, 23,24, 26, 34, 17,31, 3 and 25 in Table 1. The Brennrhein (No. 25)

dried up at least once in the warm and dry summer of 1969. It is possible that some very tolerant

species have survived the drying up. It is also possible that there was re-colonisation and that the

ice in winter has diminished the species diversity.

Species frequency in relation to the age of the water

It was in the old oxbow lakes that most ostracod species within the “Hordter Rheinaue” were

found. In the youngest waters there were only a few species. The loam-pits are a good example

of this. Table 5 shows the occurrence of ostracod species in loam-pits of different ages. The

investigations were made in ihe years 1975 and 1976, i.e. the youngest loam-pit had just been

built. One can see that the number of species increases with the age of the loam-pit.

I have called the species in the youngest loam-pits pioneer-species. There are some features that

are characteristic of them (Table 6). The characteristic of being small is good for transport from one

body of water to another, especially if insects are the transporting agents. If an ostracod can swim,

the probability of it meeting an insect is large. Also, if an ostracod reproduces parthenogenetically,

only one specimen is enough to build a population. Nevertheless, it is also important that the

species occurs in neighbouring waters.

Cypridopsis vidua meets all thbe conditions. This may be the reason why C. vidua is the most



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Chapter 38. Living ostracods from the nature reserve “Hordter Rheinaue” (Germany)

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