Comparative study of the oospore morphology of two populations of a rare species Chara baueri A. Braun in Cedynia (Poland) and Batzlow (Germany)

Abstract

Morphological features of oospores of Chara baueri A. Braun, one of the rarest charophyte species worldwide, were studied based on 100 oospores collected from a small and temporarily dried mid-field pond near Cedynia, Western Poland. This is the first Polish and fifth presently known locality of this species. For comparison 67 oospores from a German population (similar pond localized near Batzlow, Germany) were also measured. So far, data on morphology of C. baueri oospores as well as the species ecology are limited. The only more detailed study of oospores for this species was earlier performed on 15 oospores from Kazakhstan. Largest polar axis (LPA, length), largest equatorial diameter (LED, width), isopolarity index (ISI = LPA/LED × 100), number of ridges, width of fossa, distance from apical pole to LED (AND) and anisipolarity index (ANI = AND/LPA × 100) were measured. The comparative analysis revealed that the oospores from Poland are generally bigger and more prolate than the German ones. The differences for most of studied parameters were statistically significant. The finding is discussed in the context of habitat differentiation of both studied sites. Moreover, the results obtained of oospore measurements for both populations differs from most of the data known so far from the literature.

Full text

Introduction
Charophytes are multicellular organisms that occur in
fresh and brackish water bodies throughout the world [1,2].
As macroscopic green algae they form neither tissues nor
typical organs for vascular plants (Fig. 1). eir macroscopic,
equisetum-like body is called a “thallus” and is attached to
the bottom by delicate rhizomes. e main axis of charophyte
thalli is composed of a number of nodes and internodes. e
nodes are places where side-branches and whorls of branchlets
are formed in numbers depending on the genus and species.
Charophytes produce sexual propagules: oogonia (female)
and antheridia (male) on the branchlets. Charophytes develop
many other elements of morphology (e.g. bract cells, spine
cells, stipulodes) that also vary among taxa.
Oospores are the mature oogonia (becoming dark aer
fertilisation), which are surrounded by a resistant wall made
up of many layers (Fig. 2). e oospore wall ornamentation can
be species specic, e.g. for genus Nitella [1], and can be helpful
in distinguishing of the species [3-10]. Charophyte oospores
can also be preserved in sediments and used as indicators of
past conditions [11-13].
Chara baueri A. Braun (Chara scoparia Bauer ex Reichen-
bach) is one of the rarest species of the Characeae family
worldwide. e only currently known sites of this species are
localized in Kazakhstan and Germany [14-16].
A new locality of Chara baueri (the rst known locality of
this species in Poland) was found in August 2008, in a mid-
eld pond localized near Cedynia, mid-Western Poland [16].
Nowadays, Chara baueri occurs most numerously (3 sites)
in Brandenburg (Germany), about 40 kilometers west of the
Polish locality (Fig. 3).
e species is characterized by a stem with a triple cortex
with distinct solitary spine-cells and ecorticate branchlets built
by 3-4 segments with a specic coronula at the top of the nal
segment. Stipulodes are distributed in 1 tier, 1 per branchlet.
All those features were well developed by individuals found
in Polish population and clearly distinguishing Chara baueri
from other Chara species [16]. e only species that could be
mixed up in this case is Chara braunii Gmel., however, this is
distinguished by being the only totally ecorticate Chara species
in Poland.
It is also worth emphasizing that Chara baueri was amal-
gamated with Chara muelleri (described for population found
in Australia) by Wood [17]. e oospores as well thalli of that
taxon have been examined in a study by Casanova [6]. Still,
Abstract
Morphological features of oospores of Chara baueri A. Braun, one of the rarest charophyte species worldwide, were studied
based on 100 oospores collected from a small and temporarily dried mid-eld pond near Cedynia, Western Poland. is is the
rst Polish and h presently known locality of this species. For comparison 67 oospores from a German population (similar
pond localized near Batzlow, Germany) were also measured. So far, data on morphology of C. baueri oospores as well as the
species ecology are limited. e only more detailed study of oospores for this species was earlier performed on 15 oospores from
Kazakhstan. Largest polar axis (LPA, length), largest equatorial diameter (LED, width), isopolarity index (ISI = LPA/LED × 100),
number of ridges, width of fossa, distance from apical pole to LED (AND) and anisipolarity index (ANI = AND/LPA × 100) were
measured. e comparative analysis revealed that the oospores from Poland are generally bigger and more prolate than the Ger-
man ones. e dierences for most of studied parameters were statistically signicant. e nding is discussed in the context of
habitat dierentiation of both studied sites. Moreover, the results obtained of oospore measurements for both populations diers
from most of the data known so far from the literature.
Keywords: Chara baueri, oospores, Characeae, charophytes
Acta Societatis Botanicorum Poloniae
Journal homepage: pbsociety.org.pl/journals/index.php/asbp
ORIGINAL RESEARCH PAPER Received: 2011.06.16 Accepted: 2012.05.25 Published electronically: 2012.06.24 Acta Soc Bot Pol 81(2):131-136 DOI: 10.5586/asbp.2012.012
Comparative study of the oospore morphology of two populations of a rare
species Chara baueri A. Braun in Cedynia (Poland) and Batzlow (Germany)
Andrzej Pukacz1*, Patrycja Boszke2, Mariusz Józef Pełechaty2, Uwe Raabe3
1 Collegium Polonicum, UAM-Viadrina, Kościuszki 1, 69-100 Słubice, Poland
2 Department of Hydrobiology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
3 Landesamt für Natur, Umwelt und Verbraucherschutz (LNUV) NRW, Postfach 101052, 45610 Recklinghausen, Germany
* Corresponding author. Email: pukacz@europa-uni.de
This is an Open Access digital version of the article distributed
under the terms of the Creative Commons Attribution 3.0 License
(creativecommons.org/licenses/by/3.0/), which permits redistribution, commercial
and non-commercial, provided that the article is properly cited.
© The Author(s) 2012 Published by Polish Botanical Society

132
© The Author(s) 2012 Published by Polish Botanical Society
Pukacz et al. / The comparative study of Chara baueri oospore morphology
current taxonomic approaches are not sucient to conrm the
conspecicity of these disjunct populations [7,15].
Resulting from the rarity of Chara baueri, the data on its
ecology and habitat requirements are very limited [1,14-16].
To date, the only detailed study on morphological features of
oospores of Chara baueri has been carried out by Hutorowicz
[18] on the basis of 15 oospores, collected by Sviridenko in
Kazakhstan, in 1995. us, the aim of this study was to char-
acterize and compare the morphological features of oospores
of Chara baueri from two new populations, regarding also
their habitat.
Material and methods
Material was collected from two separated populations: (i)
near Cedynia, Western Poland (rst locality of this species
in Poland, found and studied in August 2008, [16]) and (ii)
near Batzlow, Germany (found in 2006 [15]; Fig. 3). For both
localities oospores and environmental data were collected in
August 2008.
e studied sites of Chara baueri are shallow mid-eld
ponds. Individuals of Chara baueri, from which oospores
were collected, occurred on mineral substratum at the depth
of 15-20 cm, on a very insolated parts of habitat. Both sites
diered as regards the vegetation structure. Pond near Cedynia
was dominated by vascular plants (mainly Ceratophyllum sub-
mersum L.) and Chara baueri occurred there in small patches,
whereas in pond near Batzlow no vascular vegetation was
found and it was co-dominated by Chara baueri and Nitella
mucronata (A. Braun) Miguel in equal proportions.
e oospores were collected from the living plants, from
dierent parts of the thallus, choosing only mature oospores
(dark colored or black). Morphological features of oospores
were studied based on 100 oospores collected from Polish
site near Cedynia. For comparison 67 oospores from a Ger-
man population were measured. All material was stored and
measured dry.
e largest polar axis (LPA, length) and the largest equato-
rial diameter (LED, width) were measured and then isopolar-
ity index (ISI = LPA /LED × 100) was calculated (Fig. 3). e
number of ridges, width of fossa, distance from apical pole to
Fig. 1 Morphological structure of charophytes, main features.

133
© The Author(s) 2012 Published by Polish Botanical Society
Pukacz et al. / The comparative study of Chara baueri oospore morphology
LED (AND) and anisipolarity index (ANI = AND/LPA × 100)
were also examined according to Horn and Rantzien [19]. All
measurements were performed using a stereoscopic micro-
scope Olympus SZX 9. Additionally, the SEM photographs
were taken at Electron and Conphocal Microscope Laboratory
(Faculty of Biology, Adam Mickiewicz University, Poznań,
Poland). Prior to the SEM images the standard cleaning pro-
cedure of careful calcium carbonate precipitation removing
was used [20].
For both ponds basic physical-chemical parameters, reect-
ing habitat conditions, were determined. e measurements of
conductivity, oxygen concentration, temperature and pH were
performed at the central site of each pond, using the multi-
functional Elmetron CX-742 eld apparatus. Water samples
for chemical analyses (total hardness, concentration of total
phosphorus and total nitrogen) were collected from the surface
layer and analysed according to commonly used analytical
methods in accordance with the “Standard methods” [21].
All statistical computations (basic descriptive statistics,
box-whiskers graphs and Mann-Whitney U-test) were done
with the use of Statistica 8.1 soware.
Results and discussion
Oospores of Chara baueri collected in Poland were prolate
or perprolate (ISI index 156-291) and had an ovoid to ellip-
soidal shape (ANI index 20-53.6). ey were dark brown or
black with prominent ridges and did not have the so called
“shoulder” (indentation in the upper part of the oospore), a
typical feature of some species (Fig. 2). e SEM analysis did
not reveal any specic wall ornamentation details, hence it was
not possible to describe it more precisely.
e measurements of oospores from Polish site revealed
quite wide variability. e length was in range of 400-667 µm,
averaging 514 ±41.9 µm, whereas width ranged from 183 to
300 µm, with an average of 262 ±25.7 µm (Tab. 1). ere were
8-11 ridges on the oospore surface, most oen 9. e mean
width of fossa was 44.7 ±10.9 µm, as they can be from 25 to
66.7 µm. e coecient of variation ranged from 8.2% for
oospore length to 24.4% for width of fossa.
e oospores from German site were 417-550 µm long,
averaging 479 ±33.9 µm and 216 to 300 µm wide, with an
average of 259 ±19.6 µm. Width of fossa ranged from 25 to
58.4 µm, with an average of 42.9 ±7.6 µm. e number of
ridges was similar to those accounted for Polish (8-11 ridges
on the oospore surface, with an average of 9.7 ±0.6) locality.
e values of coecient of variation were lower than for Polish
oospores and ranged from 6.2% for number of ridges to 18.5%
for ANI index.
To summarize, the oospores from Poland are bigger and
more prolate than the German ones. In the case of oospores
collected from the German site the variation coefficients
were lower for each feature studied. In particular, the main
Feature Mean SD Median Min. Max. V (%)
Cedynia (Poland), N = 100
ISI index 198 25.4 194 156 291 12.8
ANI index 35.9 7.3 34.5 20 53.6 20.3
LPA (µm) 514 41.9 500 400 667 8.2
LED (µm) 262 25.7 267 183 300 9.8
Number of ridges 9.2 0.8 9 8 11 8.7
Width of fossa (µm) 44.7 10.9 41.7 25 66.7 24.4
AND (µm) 184 40.5 183 100 316 22
Batzlow (Germany), N = 67
ISI index 186 16.6 186 139 238 8.9
ANI index 38.4 7.1 37.9 24.1 60.7 18.5
LPA (µm) 479 33.9 483 417 550 7.1
LED (µm) 259 19.6 267 216 300 7.6
Number of ridges 9.7 0.6 10 8 11 6.2
Width of fossa (µm) 42.9 7.6 41.7 25 58.4 17.7
AND (µm) 184 32.4 184 117 283 17.6
Tab. 1 Features of oospores of Chara baueri.
AND – distance from apical pole to LED; ANI index – anisipolarity
index AND/LPA × 100; ISI index – isopolarity index LPA/LED × 100;
LED – largest equatorial diameter; LPA – largest polar axis; Max. –
maximum; Min. – minimum; SD – standard deviation; V – variation
coecient.
Fig. 2 Oospore morphology of Chara baueri (specimen from Polish
site).
Fig. 3 Distribution map of Chara baueri sites.

134
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Pukacz et al. / The comparative study of Chara baueri oospore morphology
size features had narrower ranges of values as compared to
Polish population. Statistical analyses proved the dierences
for most of parameters are signicant (Fig. 4). According to
Mann-Whitney U-test only width of fossa and LED revealed
no statistically sound dierences (p > 0.05).
Looking for the reason of the assessed dierentiation it
should be stressed that the material for presented comparison
was in both cases collected in a similar range of time and
the sites (ponds) are situated just at a distance of few dozen
kilometers. at preclude possible inuence of the climate.
Both sites diered as regards aforementioned structure of
vegetation, that might indicate habitat dierences (Tab. 2).
However, the values of presented properties of water in most
of cases did not reveal visible dierences. e comparison of
basic properties of water quality revealed that both ponds are
highly eutrophic. Although data on the relationship between
the morphometry of oospores and habitat conditions are lack-
ing in worldwide literature, it can be presumed that this is just
what may be one of main reasons of assessed dierentiation
of oospore characteristics. Moreover it should be stressed, that
in this kind of small and shallow reservoirs also charophytes
may inuence on the habitat conditions. Such type of rela-
tions has been already described in the theory of alternative
stable states wherein strong competitive interactions between
phytoplankton and hydromacrophytes against habitat condi-
tions background were stated with important contribution of
charophytes [22-24]. It may be pointed out, e.g. by lower values
of calcium in the pond near Batzlow, that was almost entirely
overgrown by charophytes.
Even though both the Polish and German ponds are shallow
and characterized by very similar habitat properties of water
they dier as regards the size and water level uctuations. e
Fig. 4 Comparison of Chara baueri oospore features for: a Polish population; b German population.

135
© The Author(s) 2012 Published by Polish Botanical Society
Pukacz et al. / The comparative study of Chara baueri oospore morphology
whole pond near Batzlow is small, temporary ecosystem. By
contrast, the pond near Cedynia is bigger, with a permanent,
central deeper basin, that is surrounded (in wet years) by lit-
toral part which is also more preferable for charophytes. So,
in the same weather conditions, during dry period, the water
level in the pond near Cedynia does not change so rapidly
as in pond near Batzlow. Moreover, both ponds dier with
respect to the vegetation structure. e pond near Cedynia was
dominated by vascular plants, whereas pond in Batzlow was
co-dominated by Chara baueri and Nitella mucronata with no
vascular plants occurring. As was suggested by Casanova [7], in
temporary habitats oospore size can vary less because there is
strong selection pressure for germination success (which is also
related to oospore size), and in permanent habitats there can be
greater variation because there is more vegetative reproduction
and less sexual reproduction.
Another factor that can inuence the variation in oospore
size for the investigated populations may be the local variabil-
ity of weather uctuations during the vegetation season. e
eld ponds, as very shallow ecosystems, localized in the open
area are very susceptible to weather changes, especially to the
torrential rains or strong winds. Such atmospheric conditions
occur very oen in a local scale, but at the same time it can
diversify unstable ecosystems, even if the distance between
individual ponds is not very long.
e obtained data shows not only the dierences between
studied populations. Comparing the results to the most of
previously reported literature data [18,25-27], variation ranges
of the Chara baueri oospore features in the studied populations
were generally wider. It may be concluded that the oospores of
both, the Polish and German population were in most cases
bigger then in above cited literature. However, Hollerbach and
Krassavina [27] postulated that the length may reach 720 µm,
which is much more then was stated for samples from popula-
tions studied. On the other hand, maximal length found by
Hutorowicz [18] was only 574 µm.
e number of ridges (8-11) also diered the investigated
populations from the most of literature data, giving 8 ridges
as the most typical for this species [13,25,26]. It is, however,
consistent with the population from Kazakhstan, described by
Hutorowicz [17].
What is crucial here, the presently known data about Chara
baueri, show clearly that the species from dierent sites do
not reveal signicant dierences as regards the species-typical
morphometric features [1,14-16]. e reason of some discrep-
ancies between the obtained results and the literature data
regarding oospore features may results, e.g. from dierent
number included in particular investigations, dierent parts
of thalli from which the oospores were taken, the diversied
maturity or dierent habitat properties.
With reference to the information mentioned in introduc-
tion that Chara muelleri, found and described for Australia was
amalgamated with Chara baueri as the same species, it is worth
to stress out that presented results, as well as literature data
[13,18,25-27] diers clearly from the data given by Casanova
[7]. at may strongly suggest, that the species found and
described for Australia is not Chara baueri.
Even though this results may suggest ongoing speciation
within Chara baueri species, such an event has not been
documented yet. Despite considerable isolation of the presently
known localities of Chara baueri sites (four in Europe and one
in Kazakhstan), it is highly probable that they are dispersed at
much bigger area between Europe and Central Asia. Limited
knowledge about distribution of this species in all likelihood
results from very peculiar (temporary) type of ecosystems
occupied by this species [15,16].
e presented results widen the current knowledge about
this extremely rare species. However, to know better the
mechanisms of distribution and dierentiation of Chara bau-
eri, continuation of the investigations as well as additional
analyses (especially the genetic ones) would also be desirable.
Acknowledgments
The authors would like to thank Dr. Ingeborg Soulie-
Marsche (Institut des Sciences de l'Evolution, Universite Mont-
pellier, France) for her support and precious comments that
improved the manuscript.
We are also grateful to all peer-reviewers for the eort they
made to improve our paper.
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