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Protistology 11 (4), 215-230 (2017)
Protistology
Taxonomy of Quadrulella longicollis and Q. symmetrica (Arcellinida: Hyalospheniidae) from the central part of the Balkan Peninsula
Stefan Luketa
University of Novi Sad, Faculty ofScience, Department of Biology and Ecology, Novi Sad, Serbia
| Submitted November 17, 2017 | Accepted November 23, 2017 |
Summary
The genus Quadrulella comprises most species of hyalosphenid testate amoebae with quadrangular shell plates. The taxonomic status of almost all species is questionable because they are poorly studied. Quadrulella symmetrica is the type species with cosmopolitan distribution. In this paper, morphological variability of Q. symmetrica based on two populations from the central part of the Balkan Peninsula is presented. Intermediate forms between Q. symmetrica s.s. and Q. madibai were registered; therefore, taxonomic status of these two recently delimited taxa is discussed. In one studied population, a specimen covered by mixed quadrangular and circular shell plates was observed. Recently, taxonomic status of Q. longicollis has been defined as questionable. Here are present morphological and morphometric data of Q. longicollis based on 130 examined specimens from Sargan Mountain (Serbia). The present study strongly supports the opinion that this taxon is a separate species within the genus Quadrulella.
Key words: biometry, morphometry, protists, taxonomy, testate amoebae
Introduction
Hyalosphenids are one of the well-studied groups of the testate amoebae. This group comprises comparatively large species and most of them live in mosses, well-studied habitats with regard to distribution, taxonomy and ecology of testate amoebae. Therefore, hyalosphenids are considered as important bioindicators and are commonly used in environmental monitoring and paleoecology. The existence of many undescribed or inadequately described morphospecies and especially pseudocryptic species is problematic for multidisciplinary studies. Consequently, a number
ofrelevant taxonomic studies have been undertaken recently (Torok, 2001; Todorov, 2002, 2010; Lara et al., 2008; Todorov et al., 2010; Heger et al., 2011; Kosakyan et al., 2012, 2013, 2016; Bobrov and Kosakyan, 2015; Luketa, 2015, 2016, 2017a, 2017b; Nicholls, 2015; Qin et al., 2016; Singer et al., 2015; Pérez-Juárez et al., 2017).
Taxonomy of hyalosphenid testate amoebae at the generic and species level is based on shape, composition and size of their shells. Within the family Hyalospheniidae four types of the shells are present: (1) shells composed only of an organic matrix (e.g. members of the genus Hyalosphenia), (2) shells composed of the organic matrix and
doi:10.21685/1680-0826-2017-11-4-3 © 2017 The Author(s)
Protistology © 2017 Protozoological Society Affiliated with RAS
unmodified shell plates of small testate amoebae or other similar materials such as diatom frustules (e.g. members of Nebela collaris complex and Longinebela tubulosa), (3) shells composed ofthe organic matrix and modified oval and/or circular siliceous plates (e.g. Gibbocarina galeata, Longinebela golemanskyi and L. speciosa), and (4) shells composed of the organic matrix and self-secreted square siliceous plates (members of the genera Quadrulella and probably Mrabella). The most surprising result of the study conducted by Kosakyan et al. (2016) is that square scaled hyalospheniids are not a monophyletic group. Namely, they have obtained sequences from Quadrulella subcarinata, a very rare tropical species from Africa, and concluded that this species is not closely related to other Quadrulella species. For this reason, these authors established a new genus for this species — Mrabella. A very rare species, Quadrulella plicata, is also included into the genus Mrabella because it has similar shape and keel, but it is smaller than M. subcarinata.
Only a small number of papers (Chardez, 1967; Vucetich, 1983; Lopretto and Vucetich, 1997; Luketa, 2015; Pérez-Juárez et al., 2017) were exclusively devoted to the genus Quadrulella. According to the recently published taxonomic concept of the genus Quadrullela (Kosakyan et al., 2016), this genus includes eleven valid species with pyriform or elongated-pyriform shells composed of self-secreted siliceous quadrangular plates. These testate amoebae inhabit peatlands, fens, wet mosses and humus rich soils. More recently, Pérez-Juárez et al. (2017) described Q. texcalense from a Mexican desert. Kosakyan et al. (2016) treated four species (Q. con-stricta, Q. lageniformis, Q. tubulata and Q. vas) as incertae sedis and Q. longicollis as a questionable species.
The present study reports the morphological and morphometric data for Q. longicollis and Q. symmetrica based on specimens from the central part of the Balkan Peninsula.
Material and methods
The material for the present study was collected from two localities in the central part of the Balkan Peninsula: (1) Sphagnum mosses collected in the Alagovac Lake region (43°17'44.8"N, 18°07'31.9"E), East Herzegovina on 18 April 2014, 19 August 2014, 11 May 2016, and 24 July 2016; (2) epigenous mosses collected on Sargan Mountain (43°49'40.10"N, 19°31'41.40"E), Serbia
on 17 August 2016. Morphological characters and morphometric variables were studied using a light microscope (Zeiss Axio Imager A1). Images were captured using an AxioCam MRc5 (Zeiss) digital color camera. Measurements were conducted in the program AxioVision 4.9.1. The following shell parameters were measured: shell length, shell width, aperture width, and area of the optical section. The following descriptive statistics were calculated: extreme values (minimum and maximum), median, arithmetic mean, standard error of the arithmetic mean, standard deviation, coefficient of variation (in percentage), skewness, and kurtosis. Statistical analysis was conducted using the program Statistica 13.2.
Results
Quadrulella longicollis
Description. The shell is elongated ovoid, colorless, transparent and compressed laterally, especially in the apertural region. The shell is composed of siliceous, quadrangular plates that are regularly arranged in transverse and longitudinal series (rows), with smaller plates close to the aperture. The aperture is terminal, oval, and convex in broad lateral view and concave in narrow lateral view, surrounded by a thin organic lip.
Population from Sargan Mountain. Figure 1 shows light micrographs ofsome specimens from this population, while Figure 2 shows frequency scatter plot analysis of the correlation between shell width and shell length. Morphometric characters of 130 specimens from Sargan Mountain were measured and the results are presented in Table 1. Coefficients of variation were low for all measured characters, ranging from 4.53% to 9.18%. For basic characters, the minimal variability was observed for shell length (4.53%), while the maximal variation coefficient was observed for area of the optical section (9.18%). For ratio characters, the minimal variability was observed for shell width/shell length ratio (5.68%), while the maximal coefficient was observed for aperture width/shell width ratio (7.33%).
The most frequent shell length (122 ^m) was registered in 14 specimens (Fig. 3A); the most frequent shell width (54 ^m) was registered in 18 specimens (Fig. 3B), and the most frequent aperture width (25 ^m) was registered in 37 specimens (Fig. 3C). Analysis of the size frequency distribution of shell length indicates that this population possesses
Fig. 1. Light micrographs of Quadrulella longicollis: broad lateral view of different specimens from Sargan Mountain, Serbia. Scale bars: 20 ^m.
continuous polymorphism. All measured specimens had shell length between 103 and 137 ^m. In this case, 69.23% of all specimens had shell length between 115 and 125 ^m, whereas only 6.92% were smaller than 115 ^m and 23.85% were larger than 125 ^m. Analysis of the size frequency distribution of shell width and aperture width indicates that this population is size-monomorphic. Shell width ranged from 45 to 64 ^m. However, 56.92% ofall measured specimens had shell width of 52—57 ^m, whereas 30.00% were narrower than 52 ^m and only 13.08% were wider than 57 ^m. The frequency analysis of aperture width shows the similar distribution pattern. Namely, all measured specimens had aperture width between 21 and 29 ^m. In this case, 71.54% of all specimens had aperture width of24—26 ^m, whereas only 14.61% had aperture narrower than 24 ^m and
only 13.85% had aperture wider than 26 ^m. Figures 3D—F show bag plot analyses of the correlation between shell length, shell width and aperture width.
The negative skewness value (—0.006) for shell length suggests an asymmetrical distribution with a long tail toward lower values. Since the negative value is not clearly different from zero, the asymmetry of shell length distribution was minimal. Moderate positive skewness value (0.298) was registered only for shell width/shell length ratio, while other variables were characterized by low positive values (0.119—0.249). Only shell width displayed negative kurtosis value (—0.113), meaning that this variable was characterized by flatter distribution than a standard Gaussian distribution. Other variables were found to have positive kurtosis values (0.084—0.563), indicating a distribution that
Table 1. Morphometric characterization of Quadrulella longicollis from Sargan Mountain (Serbia) based on 130 specimens (measurements in |jm).
Characters Min Max M x SE SD CV Sk Ku
shell length 103 137 122 121.94 0.48 5.53 4.53 -0.006 0.460
shell width 45 64 53.5 53.4 0.33 3.73 6.99 0.173 -0.113
aperture width 21 29 25 24.89 0.126 1.44 5.77 0.176 0.084
area of the optical section 3533 6052 4805.5 4825.5 38.83 442.78 9.18 0.205 0.348
shell width/shell length 0.37 0.50 0.44 0.44 0.00 0.02 5.68 0.298 0.176
aperture width/shell length 0.18 0.24 0.21 0.20 0.00 0.01 5.75 0.249 0.563
aperture width/shell width 0.39 0.57 0.47 0.47 0.00 0.03 7.33 0.119 0.309
Fig. 2. Frequency scatter plot shows the correlation between shell width and shell length of 130 specimens of Quadrulella longicollis from Sargan Mountain, Serbia. Ellipse represents 67% confidence interval.
is sharper than the standard Gaussian distribution. Low positive values (0.084—0.176) were observed for aperture width and shell width/shell length ratio, while moderate positive values (0.309—0.460) were registered for shell length, area ofthe optical section, and aperture width/shell width ratio. High positive value (0.563) was observed for aperture width/shell length ratio.
Quadrulella symmetrica
Description. The shell is ovoid or pyriform, colorless, transparent and compressed laterally, especially in the apertural region. Shell structure is more or less symmetrical, although asymmetrical shells were also present. The shell is composed of siliceous, quadrangular plates, which are usually regularly arranged in transverse and longitudinal series (rows), with smaller plates close to the aperture. One specimen in population from Sargan Mountain has shell covered by mixed quadrangular and circular plates (Fig. 4). The aperture is terminal, oval, convex in broad lateral view and often concave in narrow lateral view, surrounded by a thin organic lip.
Population from Sargan Mountain. Figure 5 shows light micrographs ofsome specimens from this population, while Figure 6 shows frequency scatter plot analysis of the correlation between shell width and shell length. Morphometric characters of 432 specimens from Sargan Mountain were measured and the results are given in Table 2. Coefficient of variation was moderate for area ofthe optical section (11.45%), while the other measured variables were characterized by low variability (from 4.98% to 8.53%). For basic characters, the minimal variability was observed for shell length (4.98%), while the maximal variation coefficient was observed for area ofthe optical section (11.45%). For ratio characters, the minimal variability was observed for aperture width/shell length ratio (5.82%), while the maximal variation coefficient was observed for aperture width/shell width ratio (6.91%).
The most frequent shell length (76 and 77 ^m) was registered in 49 specimens (Fig. 7A); the most frequent shell width (40 and 41 ^m) was registered in 55 specimens (Fig. 7B), and the most frequent aperture width (21 ^m) was registered in 132 specimens (Fig. 7C). Analysis of the size frequency distribution of shell length, shell width
Fig. 3. Morphological variability of QQuadrulella longicollis based on 130 specimens from Sargan Mountain, Serbia. Histograms show the size frequency distribution of the shell length (A), shell width (B), and aperture width (C); bag plots show the correlation between shell length and shell width (D), aperture width and shell length (E), and aperture width and shell width (F). Legend for bag plots: depth median ♦, characters on Y axes •, outliers ■.
Fig. 4. Specimen of Quadrulella symmetrica with mixed quadrangular and circular shell plates observed in a moss-dwelling population from Sargan Mountain, Serbia. Scale bar: 20 ^m.
and aperture width indicates that this population is size-monomorphic. Shell length ranged from 64 to 89 ^m. However, 72.92% of all measured specimens had shell length of73—80 ^m, whereas only 11.80% were smaller than 73 ^m and only 15.28% were larger than 80 ^m. The frequency analyses of shell width and aperture width show similar distribution pattern. Namely, all measured specimens had shell width between 33 and 55 ^m. In this case, 54.63% of all specimens had shell width of 41—47 ^m, whereas 37.96% were narrower than 41 ^m and only 7.41% were wider than 47 ^m. All measured specimens had aperture width between 17 and 25 ^m. However, 75.93% of all specimens had aperture width of 20—22 ^m, whereas only 17.36% had aperture narrower than 20 ^m and only 6.71% had aperture wider than
22 ^m. Figures 7D—F show bag plot analyses of the correlation between shell length, shell width and aperture width.
The negative values of skewness for shell length (—0.156) and aperture width/shell width ratio (—0.162) suggest an asymmetrical distribution with a long tail toward lower values. The asymmetry of aperture width (0.020) and aperture width/shell length ratio (0.090) was low, while high positive skewness values (0.535—0.612) were observed for shell width, area of the optical section and shell width/shell length ratio. The negative values of skewness were not observed, meaning that all variables were characterized by a distribution that is sharper than the standard Gaussian distribution. Low positive values were observed for aperture width (0.081), aperture width/shell length ratio (0.023), and aperture width/shell width ratio (0.131). High positive values (0.501—1.087) were observed for all other variables.
Population from the Alagovac Lake region. Figure 8 shows light micrographs of some specimens from this population, while Figure 9 shows frequency scatter plot analysis of the correlation between shell width and shell length. Morphometric characters of 462 specimens from the Alagovac Lake region were measured and the results are given in Table 3. Coefficient ofvariation was moderate for area ofthe optical section (12.08%), while the other measured variables were characterized by low variability (from 4.96% to 9.67%). For basic characters, the minimal variability was observed for shell length (4.96%), while the maximal variation coefficient was observed for area of the optical section (12.08%). For ratio characters, the minimal variability was observed for
Table 2. Morphometric characterization of Quadrulella symmetrica from Sargan Mountain (Serbia) based on 432 specimens (measurements in |jm).
Characters Min Max M x SE SD CV Sk Ku
shell length 64 89 77 76.92 0.18 3.83 4.98 -0.156 0.501
shell width 33 55 41 41.80 0.17 3.56 8.53 0.569 0.664
aperture width 17 25 21 20.69 0.06 1.27 6.13 0.020 0.081
area of the optical section 1735 3737 2474.5 2486.6 13.69 284.62 11.45 0.535 1.087
shell width/shell length 0.46 0.69 0.54 0.54 0.00 0.04 6.73 0.612 0.550
aperture width/shell length 0.22 0.32 0.27 0.27 0.00 0.02 5.82 0.090 0.023
aperture width/shell width 0.39 0.61 0.50 0.50 0.00 0.03 6.91 -0.162 0.131
Fig. 5. Light micrographs of Quadrulella symmetrica: broad lateral view of different specimens from Sargan Mountain, Serbia. Scale bars: 20 цт.
Fig. 6. Frequency scatter plot shows the correlation between shell width and shell length of 432 specimens of Quadrulella symmetrica from Sargan Mountain, Serbia. Ellipse represents 67% confidence interval.
aperture width/shell width ratio (6.50%), while the maximal variation coefficient was observed for shell width/shell length ratio (8.51%).
The most frequent shell length (81 ^m) was registered in 56 specimens (Fig. 10A); the most frequent shell width (44 ^m) was registered in 48 specimens (Fig. 10B), and the most frequent aperture width (22 ^m) was registered in 117 specimens (Fig. 10C). Analysis of the size frequency
distribution of shell length and aperture width indicates that this population is size-monomorphic. Shell length ranged from 69 to 93 ^m. However, 71.21% of all measured specimens had shell length of 77—85 ^m, whereas only 7.58% were smaller than 77 ^m and only 21.21% were larger than 85 ^m. The frequency analysis of aperture width shows similar distribution pattern. Namely, all measured specimens had aperture width between 18 and
Table 3. Morphometric characterization of Quadrulella symmetrica from the Alagovac Lake region (East Herzegovina) based on 462 specimens (measurements in |jm).
Characters Min Max M x SE SD CV Sk Ku
shell length 69 93 82 82.33 0.19 4.08 4.96 -0.008 0.179
shell width 38 58 45 46.04 0.21 4.45 9.67 0.389 -0.676
aperture width 18 26 22 21.91 0.07 1.55 7.05 0.230 -0.210
area of the optical section 2171 4097 2897.5 2929.81 16.47 353.95 12.08 0.484 0.007
shell width/shell length 0.44 0.68 0.55 0.56 0.00 0.05 8.51 0.233 -0.696
aperture width/shell length 0.20 0.33 0.27 0.27 0.00 0.02 6.86 0.164 0.641
aperture width/shell width 0.39 0.59 0.48 0.48 0.00 0.03 6.50 0.048 -0.012
Fig. 7. Morphological variability of Quadrulella symmetrica based on 432 specimens from Sargan Mountain, Serbia. Histograms show the size frequency distribution of the shell length (A), shell width (B), and aperture width (C); bag plots show the correlation between shell length and shell width (D), aperture width and shell length (E), and aperture width and shell width (F). Legend for bag plots: depth median ♦, characters on Y axes • , outliers ■.
Fig. 8. Light micrographs of Quadrulella symmetrica: broad lateral view of different specimens from the Alagovac Lake region, East Herzegovina. Scale bars: 20 ^m.
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Fig. 9. Frequency scatter plot shows the correlation between shell width and shell length of 462 specimens of Quadrulella symmetrica from the Alagovac Lake region, East Herzegovina. Ellipse represents 67% confidence interval.
26 ^m. In this case, 67.53% of all specimens had aperture width of 21—23 ^m, whereas only 16.88% had aperture narrower than 21 ^m and only 15.59% had aperture wider than 23 ^m. Analysis of the size frequency distribution of shell width indicates that this population is size-monomorphic. All measured specimens had shell width between 38 and 58 ^m. In this case, 43.07% of all specimens had shell width of 45—51 ^m, whereas 45.02% were narrower than 45 ^m and only 11.91% were wider than 63 ^m. Figures 10D—F show bag plot analyses of the correlation between shell length, shell width and aperture width.
The negative value ofskewness (—0.008) for shell length suggests an asymmetrical distribution with a long tail toward lower values. Moderate positive skewness values were observed for shell width (0.389) and area of the optical section (0.484). All other variables were characterized by low positive skewness values (0.048—0.233). Four characters (shell width, aperture width, shell width/shell length ratio, and aperture width/shell width ratio) displayed negative kurtosis values, meaning that they were characterized by flatter distribution than a standard Gaussian distribution. Because the negative values obtained for aperture width (—0.210) and
aperture width/shell width ratio (—0.012) were not clearly different from zero, the resulting deviation from normal Gaussian distribution was minimal. However, negative values for shell width (—0.676) and shell width/shell length ratio (—0.696) were clearly different from zero, indicating that the average size group has a lower dispersion. Other variables were found to have positive kurtosis values (0.007—0.641), indicating a distribution that is sharper than the standard Gaussian distribution.
Discussion
Taranek (1882) described Quadrulella symmetrica var. longicollis. This taxon is characterized by more elongate shell than the typical form of Q. symmetrica and, based on the original description, a shell length range from 80 to 150 ^m. Deflandre (1936) noted that specimens ofthis taxon are usually longer than 100 ^m. Ogden (1984) speculated that these could represent extra large specimens, as often seen in species of the genus Euglypha, and thus did not differentiate them from typical Q. symmetrica. Cerda (1986) examined specimens from Bolivia
Fig. 10. Morphological variability of of Quadrulella symmetrica based on 462 specimens from the Alagovac Lake region, East Herzegovina. Histograms show the size frequency distribution of the shell length (A), shell width (B), and aperture width (C); bag plots show the correlation between shell length and shell width (D), aperture width and shell length (E), and aperture width and shell width (F). Legendfor bag plots: depth median ♦, characters on Y axes •, outliers ■.
and noted the following measurements: shell length 130—150 ^m, shell width 60—70 ^m and aperture width 20—30 ^m. Kosakyan et al. (2012) based on molecular data concluded that Q. symmetrica var. longicollis is a separate species and made a new combination of this taxon: Quadrulella longicollis. Luketa (2015) based on eight specimens of Q. longicollis collected in Sphagnum mosses from the Vlasina Lake region (Serbia) noted the following measurements: shell length 111—131 ^m, shell width 50—57 ^m and aperture width 27—28 ^m. Kosakyan et al. (2016) concluded that population from the Vlasina Lake region may represent the true Q. longicollis. Luketa (2015) based on shell shape observed two shell types: broad and narrow. In the population from Sargan Mountain analysed in the present study, only broad shell types were observed.
Kosakyan et al. (2016) described new Sphagnum-dwelling species from Switzerland with variable neck length: Quadrulella variabilis. Based on seven sequenced specimens, they noted the following measurements: shell length 66—69 ^m, shell width 35—40.5 ^m and aperture width 17—18.5 ^m. Also, they concluded that the sequenced specimen of Q. longicollis from the study published in Kosakyan et al. (2012) might be a member of Q. variabilis. Namely, this specimen has shell length 96 ^m and it is longer than typical specimens of Q. variabilis, but they have similar size of aperture and shell plates. Gauthier-Lièvre (1957) observed Nebela ( Quadrulella) symmetrica var. longicollis from the Republic of Congo (Middle Africa) and noted the following measurements: shell length 80—95 ^m, shell width 40—46 ^m and aperture width 20—23 ^m. Green (1979) observed two specimens ofthis taxon in the open water of the Lake Sonfon (Sierra Leone, West Africa) and noted the following measurements: shell length 90 ^m, maximum shell width 45 ^m, and aperture diameter 19 ^m. The specimen from Kosakyan et al. (2012) morphometrically is very similar to specimens from the above mentioned African populations.
Kosakyan et al. (2016) considered that the typical Q. longicollis is longer than 100 ^m and thus does not overlap with the sequenced Q. variabilis. It is possible that the specimen from Kosakyan et al. (2012) represent an extremely short specimen of Q. longicollis. Namely, the shell size range proposed by Taranek (1882) included the specimen described in Kosakyan et al (2012). Another possibility is that the Q. longicollis complex includes four species: Q. variabilis (shell length 66—69 ^m), an undescribed
species (shell length 80—96 ^m), Q. longicollis s.s. (shell length 110—130 ^m), and a very long undescribed species (shell length 130—150 ^m). Detailed morphological, morphometric, ecological and molecular studies using additional populations are needed to clarify true taxonomic status of all taxa from Q. longicollis complex.
To the best ofmy knowledge, only two examples of Quadrulella members were noted with shells covered by mixed quadrangular and circular plates. Gauthier-Lièvre (1957) observed specimens of Q. tropica from Africa with shells covered by mixed quadrangular and circular plates. Later, Chung et al. (1992) noted some specimens of Q. symmetrica from South Korea with shell surface covered by quadrangular and circular shell plates. In addition, in the present study a specimen of Q. symmetrica from Sargan Mountain with similar shell structure was observed. These findings put forward new questions on the evolution of square plates. The specimens of Q. symmetrica with mixed shell plates may be classical mutants, mutants with atavistic nature, or a beginning of new phyletic lineage. In the first assumption, round plates are abnormal self-secreted plates. The second assumption indicates that the ancestor of the genus Quadrulella possessed the shell completely covered by round self-secreted plates. The third assumption suggests that specimens with mixed shell coverage present new species if round plates are the products of neutral or positive mutations. Further molecular and morphological studies based on large number of populations will resolve the taxonomic status of square scaled hyalosphenids.
Kosakyan et al. (2012) revealed an unexpected morphological and genetic variability of Q. symmet-rica, but they did not propose new taxonomic changes. However, Kosakyan et al. (2016) based on detailed study of this morphospecies concluded that Q. symmetrica is not a single species. Namely, they demonstrated that this taxon hosts at least three different genetic species that are well supported by the morphological characteristics: Q. symmetrica s.s., Q. variabilis and Q. madibai. Quadrulella variabilis is morphologically very similar to Q. symmetrica s.s., from which it differs by the dimensions of the shell and the size of scale plates (shell length 66—69 ^m, maximum plate size 7—9 ^m in Q. variabilis versus shell length 72—85 ^m, maximum plate size 10—12 ^m in Q. symmetrica s.s.). An interesting case is Q. madibai, which is morphologically similar to Q. symmetrica s.s. because of its large shell plates
Table 4. Comparative morphometric data of Quadrulella symmetrica based on three populations
from the Balkan Peninsula.
Characters Location N Min Max x References
shell length Vlasina Lake region 603 71 93 82.87 Luketa, 2015
Sargan Mountain 432 64 89 76.92 This study
Alagovac Lake region 462 69 93 82.33 This study
shell width Vlasina Lake region 603 39 58 47.72 Luketa, 2015
Sargan Mountain 432 33 55 41.80 This study
Alagovac Lake region 462 38 58 46.04 This study
aperture width Vlasina Lake region 603 20 29 23.61 Luketa, 2015
Sargan Mountain 432 17 25 20.69 This study
Alagovac Lake region 462 18 26 21.91 This study
area of the optical section Vlasina Lake region 603 2301 4164 3076.58 Luketa, 2015
Sargan Mountain 432 1735 3737 2486.60 This study
Alagovac Lake region 462 2171 4097 2929.81 This study
shell length/shell width Vlasina Lake region 603 0.47 0.72 0.58 Luketa, 2015
Sargan Mountain 432 0.46 0.69 0.54 This study
Alagovac Lake region 462 0.44 0.68 0.56 This study
aperture width/shell length Vlasina Lake region 603 0.24 0.35 0.29 Luketa, 2015
Sargan Mountain 432 0.22 0.32 0.27 This study
Alagovac Lake region 462 0.20 0.33 0.27 This study
aperture width/shell width Vlasina Lake region 603 0.40 0.58 0.50 Luketa, 2015
Sargan Mountain 432 0.39 0.61 0.50 This study
Alagovac Lake region 462 0.39 0.59 0.48 This study
Abbreviations: N - number of measured specimens, Min - minimum value, Max - maximum value, x - arithmetic mean
(maximum plate size 9—11 ^m in Q. madibai versus 10—12 ^m in Q. symmetrica s.s.). However, Q. symmetrica s.s. can be discriminated from Q. madibai based on its less slender and elongated shell (shell length/shell width ratio is 1.7—1.9 in Q. symmetrica s.s. versus 2.0—2.3 in Q. madibai). In addition, the general outline ofthe shell in Q. madi-bai is globally more tubular and does not present a distinct neck. Based on the detailed morphological and morphometric data presented in this study, it is not possible to distinguish Q. symmetrica s.s. and Q. madibai. Probably, Q. madibai represents only one extreme line of clones. Further molecular and morphological studies based on large number of populations will resolve the taxonomic status of these two taxa. Comparative morphometric data of three Q. symmetrica populations from the Balkan Peninsula are presented in Table 4.
Acknowledgments
I am very grateful to Dr. Ivo Karaman and Dr. László Barsi (University of Novi Sad, Serbia) for moss sample from Sargan Mountain. Also, I am very grateful to Dr. László Barsi for permission to use the Zeiss Axio Imager A1 light microscope.
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Address for correspondence: Stefan Luketa. Department of Biology and Ecology, Faculty of Science, University ofNovi Sad, Trg Dositeja Obradovica 2, 21000 Novi Sad, Serbia; e-mail: stefan.luketa@dbe.uns.ac.rs
