Research Article |
Corresponding author: Eduard Solà ( edu.sola@gmail.com ) Academic editor: Fredric Govedich
© 2015 Eduard Solà, Ronald Sluys, Ori Segev, Leon Blaustein, Marta Riutort.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Solà E, Sluys R, Segev O, Blaustein L, Riutort M (2015) The taxonomic status of Dugesia biblica from Israel and Turkey (Platyhelminthes, Tricladida, Dugesiidae). ZooKeys 506: 1-12. https://doi.org/10.3897/zookeys.506.9663
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The taxonomic status of Dugesia biblica (Platyhelminthes, Tricladida, Dugesiidae) from Israel and Turkey is problematic due to its morphological similarity with D. sicula since these nominal species present overlapping characters. In this study we analyzed histological preparations of specimens of these two nominal species and also compared mitochondrial COI gene sequences from Israeli populations to the already known haplotype composition of D. sicula. We concluded that these animals belong to the same species and therefore we consider D. biblica to be a junior synonym of D. sicula. This implies that the distribution range of D. sicula is even wider than previously thought, and that the species is present all around the Mediterranean Basin and on many of its islands.
Platyhelminthes , Tricladida , Dugesia , taxonomy, synonymy, biogeography, Israel, COI , haplotype, karyology, morphology, Turkey
The freshwater planarian fauna of Israel has been relatively well studied (
Dugesia biblica was originally described from fissiparous specimens collected from the Jordan River in Israel (
In the course of our studies on the evolution and diversification of the genus Dugesia in the Mediterranean region (cf.
New samples of Dugesia from Israel were obtained during winter, spring and summer seasons in 2009 and 2010. We visited 32 localities (Table
Israeli sampling localities from where Dugesia specimens were collected. The species have been identified on the basis of the COI gene sequence.
Code | Locality | Species | Sampling date | Site description | Coordinates |
---|---|---|---|---|---|
SHE | Ein Shefa | D. sicula | 06/25/2009 | Fast flowing man made spring channel | 33°0'34.47"N, 35°8'11.15"E |
BAN | Nahal Banias | D. sicula | 08/27/2009 | Fast flowing stream | 33°14'47.44"N, 35°41'23.75"E |
BET | Nahal Betzet | D. sicula | 09/01/2009 | Isolated temporary pools within dry stream | 33°4'32.84"N, 35°13'34.18"E |
TEO | Ein Te’o | D. sicula | 02/03/2010 | Shallow spring with moderate water flow | 33°7'55.95"N, 35°34'8.54"E |
ENU | Ein Nun | D. sicula | 02/03/2010 | Shallow spring with moderate water flow | 32°50'18.35"N, 35°30'39.41"E |
EHU | Einot Huga | Not D. sicula | 05/09/2010 | Shallow spring - rather saline water ≤2000 mg Cl/l | 32°31'2.68"N, 35°32'17.27"E |
EOV | Ein Ovdat | D. sicula | 05/09/2010 | Partly connected with slowly flowing spring pools of a desert stream | 30°49'25.07"N, 34°45'50.00"E |
TZU | Ein Tzuba | D. sicula | 05/10/2010 | Shallow man-made spring pool | 31°46'58.33"N, 35°7'45.72"E |
SAT | Ein Sataf | D. sicula | 05/10/2010 | Small spring pool inside a man-made underground cave | 31°46'15.77"N, 35°7'38.00"E |
GED | Ein Gedi | Dugesia sp. | 08/04/2010 | Small shallow spring pool - desert area | 31°28'0.60"N, 35°23'19.11"E |
DAN | Dan Springs | Not D. sicula | 08/18/2010 | Shallow slowly flowing stream | 33°14'56.82"N, 35°39'1.95"E |
Total genomic DNA was extracted by using the commercial reagent DNAzol (Molecular Research Center Inc., Cincinnanti, OH), following the manufacturer’s instructions. A fragment of the cytochrome c oxidase subunit I (COI) was amplified using specific primers. Sequences and annealing temperatures for the pair of primers are given in Table
Forward (F) and Reverse (R) primers used in the amplification and sequencing of the COI mitochondrial gene sequence.
Name | Direction | Sequence 5’−3’ | Annealing temperature (°C) | Source |
---|---|---|---|---|
BarT | F | ATGACDGCSCATGGTTTAATAATGAT | 43 |
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COIEF3 | F | CCWCGTGCWAATAATTTRAG | 43 |
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COIR | R | CCWGTYARMCCHCCWAYAGTAAA | 43 |
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The number of Dugesia individuals analyzed per locality ranged between 1 and 7, depending on the available number of specimens and the success of sequencing (Table
Individual | Locality | Polymorphic | Haplogroup | Haplotype in Figure |
GenBank Acc. Number |
---|---|---|---|---|---|
D01TEO | Ein Te’o | No | A | 7 | KR140038 |
D01BAN | Nahal Banias | No | B | 2 | KR140035 |
D02BAN | Yes | − | − | KR140040 | |
D03BAN | Yes | − | − | KR140045 | |
D04BAN | No | B | 2 | KR140049 | |
D02SHE | Ein Sheva | No | B | 3 | KR140043 |
D03SHE | No | B | 3 | KR140047 | |
D04SHE | Yes | − | − | KR140052 | |
D05SHE | Yes | − | − | KR140056 | |
D06SHE | No | B | 3 | KR140059 | |
D01BET | Nahal Betzet | No | B | 8 | KR140036 |
D02BET | No | B | 8 | KR140041 | |
D03BET | No | B | 8 | KR140046 | |
D04BET | No | B | 3 | KR140050 | |
D05BET | No | B | 3 | KR140053 | |
D01TZU | Ein Tzuba | No | B | 4 | KR140039 |
D02TZU | No | B | 4 | KR140044 | |
D03TZU | No | B | 4 | KR140048 | |
D07TZU | No | B | 4 | KR140062 | |
D08TZU | No | B | 4 | KR140063 | |
D09TZU | No | B | 4 | KR140066 | |
D10TZU | No | B | 4 | KR140067 | |
D04SAT | Ein Sataf | No | B | 5 | KR140051 |
D05SAT | No | B | 5 | KR140055 | |
D06SAT | No | B | 5 | KR140058 | |
D07SAT | No | B | 5 | KR140061 | |
D11SAT | Yes | − | − | KR140068 | |
D06EOV | Ein Ovdat | No | B | 1 | KR140057 |
D07EOV | No | B | 1 | KR140060 | |
D09EOV | No | B | 6 | KR140065 | |
D01ENU | Ein Nun | Yes | − | − | KR140037 |
D02ENU | Yes | − | − | KR140042 | |
D05ENU | Yes | − | − | KR140054 | |
D09ENU | Yes | − | − | KR140064 | |
D16ENU | Yes | − | − | KR140069 |
Material examined (collections Naturalis Biodiversity Center, Leiden):
Dugesia biblica:
ZMA V.Pl. 698.1, Banias Waterfall, Israel, transverse sections on 6 slides, V.Pl. 698.2, ibid., sagittal sections on 8 slides.
ZMA V.Pl. 699.1, Ein El Hanea, Israel, January 1972, sagittal sections on 8 slides; V.Pl. 699.2., ibid., transverse sections on 12 slides.
ZMA V. Pl. 813.1, spring, 5 km NW of Bucak, Turkey, sagittal sections on 2 slides; V.Pl. 813.2, ibid., sagittal sections on 3 slides; V.Pl. 813.3, ibid., frontal sections on 2 slides.
ZMA V.Pl. 814.1, stream near Yerkopru, Hadim, Turkey, sagittal sections on 4 slides; V.Pl. 814.2, ibid., sagittal sections on 3 slides; V.Pl. 814.3, ibid., frontal sections on 3 slides.
Dugesia sicula:
ZMA V.Pl. 7152.1, Tripes, Chios, Greece, 2 May 2010, sagittal sections on 10 slides.
Out of the 32 localities that we visited in Israel, about one-third (11) yielded specimens of Dugesia (Fig.
Unfortunately, preservation and histological problems eventually prevented us of carrying out detailed morphological analyses on the reproductive apparatus of Israeli Dugesia specimens from the various newly sampled populations (Table
We were successful in obtaining COI sequences for 8 out of the 9 sampling localities; 25 out of the 35 sequences obtained for the present study presented no polymorphism, while the remaining sequences showed between 1 and 12 polymorphic positions. We used both the 25 COI non-polymorphic sequences from presumed Israeli D. biblica obtained for this study (Table
Most of the Israeli COI haplotypes are identical or are only 1−4 positions removed from the major D. siculaCOI haplotype B (Fig.
Haplotype network of Dugesia sicula and presumed D. biblicaCOI sequences. Filled red circles correspond to haplogroup A, filled blue circles correspond to haplogroup B, and filled brown circles correspond to haplogroup C of D. sicula (as defined in
Additionally, we compared the polymorphic sequences of the Israeli Dugesia not included in the haplotype network (Table
The results of our molecular analyses suggest a wide distribution of D. sicula throughout Israel (Fig.
We have been unable to find any stable structural morphological difference between sicula populations and presumed biblica populations. All of these animals are characterized by distinctly acentral opening of the ejaculatory duct; asymmetrical oviducal openings into the bursal canal; rather thick layer of circular muscles around bursal canal; bursal canal that runs somewhat laterally to the penis; zone of mesenchymatic gland cells around bursal canal; somewhat bilobed seminal vesicle; somewhat irregularly running bursal canal, with irregular diameter; distinct patch of cyanophil secretion in dorsal section of penis papilla.
Characteristic of D. biblica is the occurrence in the field of a sexually reproducing diploid form with a chromosome complement of 2n = 18, and a triploid form that reproduces asexually by fission with a set of 3n = 27 + 1−5 supernumerary chromosomes. Under laboratory conditions, the normally fissioning animals can be induced to develop reproductive organs. The structure of the copulatory organs of these sexualized animals is identical to that of the normally sexually reproducing diploid forms. However, in the diploid forms, testes and ovaries show their normal dimensions and development, whereas in the sexualized animals the testes are underdeveloped and the ovaries hyperplasic (cf.
The situation that (1) in the field some populations may reproduce asexually and show a triploid set of 3n = 27 + 2−3 B chromosomes, (2) others reproduce sexually and show a complement of 2n = 18 gradually decreasing, metacentric chromosomes, and (3) sexualized, triploid specimens show hyperplasic ovaries and poorly developed testes is well-known for D. sicula (cf.
In addition to the morphological and karyological similarities between nominal Dugesia biblica and D. sicula (see above), our molecular analysis shows presumed biblica populations to be molecularly indistinguishable from sicula populations. The Israeli haplotypes obtained are either identical to previously obtained sicula or present few differences from these. Therefore, on the basis of our integrative analysis, we consider D. biblica to be a junior synonym of D. sicula.
This conclusion holds true for one of the two Turkish populations of presumed biblica described by
We thank Heather Bromley for fruitful discussion. We are indebted to Gema Blasco for support in the laboratory. E. Solà acknowledges support from Synthesys, the European Union-funded Integrated Activities grant (project grant: NL-TAF 5151). This research was also supported by BES-2009-022530 Grant from the Ministerio de Ciencia e Innovación (to E. Solà), and by grants CGL2008-00378 and CGL2011-23466 (to M. Riutort).
Supplementary Table
Data type: occurence
Explanation note: Localities in Israel from which no specimens of Dugesia could be obtained during our samplings.