A recent record of Romanogobio antipai (Actinopterygii, Cyprinidae, Gobioninae) from the Danube River in Bulgaria

Abstract

The Danube delta gudgeon, Romanogobioantipai , has been considered to be extinct because there were no reliable recent observations. The latest record confirmed by a voucher specimen dating from 1992. We report here on a specimen of R.antipai collected in 2016 in the Bulgarian sector of the Danube main stream using a bottom drift net at a depth of 8 m. The species determination is supported by morphological examination including discriminant and cluster analyses in comparison with three syntypes and five non-type specimens of R.antipai , samples of the R.kesslerii species complex and R.vladykovi . Romanogobioantipai most clearly differs from both R.kesslerii and R.vladykovi by proportional measurements (caudal peduncle depth, head width, eye horizontal diameter, and interorbital width), from R.kesslerii also by the number of scales above and below the lateral line (6 and 4, respectively, (vs. commonly 5 and 3), and from R.vladykovi , also by 8½ branched dorsal-fin rays (vs. 7½) and the vertebral caudal region longer than the abdominal vertebral region (abdominal+caudal vertebrae 19+21 or 20+21, vs. commonly 20+20 or variants with a caudal region shorter than the abdominal one). The possibility that R.antipai represents a deep-water cophenotype of either R.kesslerii or R.vladykovi , cannot be excluded. The new record demonstrates that R.antipai is still extant in the lower Danube but may be restricted to greater depths in the main channel and the deltaic branches.

Full text

A recent record of Romanogobio antipai, from the Danube River in Bulgaria 105
A recent record of Romanogobio antipai
(Actinopterygii, Cyprinidae, Gobioninae) from the
Danube River in Bulgaria
Nina G. Bogutskaya1, Tihomir Stefanov2, Alexander M. Naseka1,
OlegA.Diripasko3
1 Naturhistorisches Museum Wien, Burgring 7, Vienna 1010, Austria 2 National Museum of Natural History,
1 Tsar Osvoboditel Blvd, 1000 Soa, Bulgaria 3 Institute of Fisheries and Marine Ecology, 8 Konsulska St,
Berdyansk, 71118, Ukraine
Corresponding author: Nina G. Bogutskaya (nina.bogutskaya@nhm-wien.ac.at)
Academic editor: S. Kullander|Received 14 December 2018|Accepted 23 January 2019|Published 27 February 2019
http://zoobank.org/73D054EE-A662-43B1-AC5D-1A7176839372
Citation: Bogutskaya NG, Stefanov T, Naseka AM, Diripasko OA (2019) A recent record of Romanogobio antipai
(Actinopterygii, Cyprinidae, Gobioninae) from the Danube River in Bulgaria. ZooKeys 825: 105–122. https://doi.
org/10.3897/zookeys.825.32434
Abstract
e Danube delta gudgeon, Romanogobio antipai, has been considered to be extinct because there were no
reliable recent observations. e latest record conrmed by a voucher specimen dating from 1992. We re-
port here on a specimen of R. antipai collected in 2016 in the Bulgarian sector of the Danube main stream
using a bottom drift net at a depth of 8 m. e species determination is supported by morphological
examination including discriminant and cluster analyses in comparison with three syntypes and ve non-
type specimens of R. antipai, samples of the R. kesslerii species complex and R. vladykovi. Romanogobio
antipai most clearly diers from both R. kesslerii and R. vladykovi by proportional measurements (caudal
peduncle depth, head width, eye horizontal diameter, and interorbital width), from R. kesslerii also by the
number of scales above and below the lateral line (6 and 4, respectively, (vs. commonly 5 and 3), and from
R. vladykovi, also by 8½ branched dorsal-n rays (vs. 7½) and the vertebral caudal region longer than
the abdominal vertebral region (abdominal+caudal vertebrae 19+21 or 20+21, vs. commonly 20+20 or
variants with a caudal region shorter than the abdominal one). e possibility that R. antipai represents
a deep-water cophenotype of either R. kesslerii or R. vladykovi, cannot be excluded. e new record dem-
onstrates that R. antipai is still extant in the lower Danube but may be restricted to greater depths in the
main channel and the deltaic branches.
ZooKeys 825: 105–122 (2019)
doi: 10.3897/zookeys.825.32434
http://zookeys.pensoft.net
Copyright Nina G. Bogutskaya et al. 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.
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Keywords
Danube delta gudgeon, morphology, meristics, distribution, conservation status
Introduction
Romanogobio Bănărescu, 1961 is a genus of bottom-dwelling, rheophilic gudgeons
with a wide distribution in temperate Eurasia. Six species were reported from the
Danube basin (Kottelat and Freyhof 2007, Friedrich et al. 2018). Among them, Ro-
manogobio antipai was described, as Gobio kessleri antipai, by Bănărescu (1953: 300,
318) based on a series of syntypes from the Danube delta at Sulina (12 specimens col-
lected by Grigore Antipa before 1909) and the lower reaches of the Danubian tributary
Argeş (one specimen collected by Băcescu). In the same paper, representing a study of
morphometric features within the “Gobio kessleri” group of populations distributed in
Romania, Bănărescu also recognized a new form, Gobio kessleri kessleri natio banaticus
(the name is not available from this publication, but available as Gobio kessleri banati-
cus from Bănărescu 1960: 121) and compared both new forms with the nominotypical
subspecies. As the correct original spelling of the specic name is kesslerii (Kottelat
1997), we use it hereafter.
Bănărescu (1953) distinguished Romanogobio antipai from R. kesslerii and R. k.
banaticus on average values of the postorbital distance (10.5% of body length vs 8.5–
10%), barbel length (10.5–13% of body length vs 8–11.5%), eye diameter (5.5% of
body length vs 5.6–6.4% R. excluding kesslerii (Dybowsky, 1862) from Bulgaria with
4.8–5.6%, and 75.2% of interorbital distance vs 81.9–98.5%), snout length (9.4%
of body length vs 9.4–11.7%), and maximum body depth (18.4% of body length vs
1.8–17.7% excluding R. kesslerii from the Dniester with an average of 18.5%). Conse-
quently, no clear dierences between the three taxa were presented, and later Bănărescu
(1960, 1961) reported the occurrence of specimens morphologically intermediate be-
tween R. antipai and R. kesslerii in the Danube tributaries Ialomiţa, Argeș (Dâmboviţa)
and Siret (Bizau and Milcov Rivers), recognized as such also by Bănărescu and Nalbant
(1973). Bănărescu (1961, 1999: 151) repeated the most typical features of R. antipai
from the Danube delta (smaller eye and deeper body), adding smaller body length in
adults (“apparently not exceeding 6 cm”), commonly 4 scales (vs commonly 3) be-
tween the lateral line and the pelvic-n origin, caudal-peduncle width at the anal-n
origin commonly about equal to caudal-peduncle depth (vs larger in kesslerii), and
short lateral blotches (vs commonly elongated in banaticus). e distribution range
was widened (Bănărescu 1961: 344) to include the lower reaches of the Siret River
and its tributaries, the Milcov, Putna, and Birlad Rivers, and the lowest reaches of the
Argeş and Ialomiţa Rivers. Similar data were later published in the book on the shes
of Romania (Bănărescu 1964: 454–455, g. 195).
Bănărescu (1992, 1994a, 1999: 150, g. 21) again restricted the range of R. antipai
to the lowest reaches of the Danube, mentioning that before 1959, it was distributed
upstream to the Argeş River mouth (some 430 river kilometres). He emphasized that it

A recent record of Romanogobio antipai, from the Danube River in Bulgaria 107
markedly diered from other members of the R. kesslerii complex by its morphological
features, which were related to dwelling in deep water of the main stream of the river.
Bănărescu (1992, 1994a, 1999) treated the Danube delta gudgeon as a subspecies
(Gobio kesslerii antipai) but mentioned that it deserved the rank of species. Kottelat
and Freyhof (2007) considered it as a valid species and Friedrich et al. (2018) found
no arguments to reject this status.
e sample of Romanogobio antipai from the Danube delta at Sulina, described by
Bănărescu based on G. Antipa’s collections (before 1909) was not the only one from
the Danube delta. Smirnov (1971) provided meristic and morphometric data on a
sample of 24 specimens collected by him in April 1961 in the Ukrainian part of the
delta (Chilia Arm) near Izmail and identied it as R. kesslerii. is sample was later
included in the book on Ukrainian shes by Movchan and Smirnov (1981: 344, tab.
181). Bănărescu (1999: 158) suggested that Smirnov’s (1971) specimens from Izmail
belonged to R. antipai because they had a deeper body and a smaller eye.
e most recent published record of R. antipai from the lower section of the Dan-
ube may be that of Marinov (1978) who reported Gobio kesslerii from the main course
of the Danube in Bulgaria. e true R. kesslerii only occurs in middle reaches of tribu-
taries and has not been recorded from the deep main stream of the Danube (e.g.,
Chichko 1937, Mihailova 1970, Dikov et al. 1994).
e absence of recent records of R. antipai lead some authors to the conclusion
that the species might be extinct (Bănărescu 1994b, Kottelat 1997). Its conservation
status was later evaluated as extinct (Kottelat and Freyhof 2007, Freyhof and Kottelat
2008) because it was supposed that all known ichthyological surveys conducted since
the 1960s to 2003 in suitable habitats in the Danube delta had failed to nd it; how-
ever, this statement is not entirely correct as there is a specimen in Natural History
Museum ‘Grigore Antipa’ collected in 1992 (described below).
In 2016, TS collected a gudgeon specimen in the Bulgarian sector of the Danube
main stream using a bottom drift net at a depth of 8 m, near the village of Vetren (river
kilometer 395). is specimen (Figs 1–2) was preliminarily identied by AN as Ro-
manogobio antipai because of its small eye and 8½ branched dorsal-n rays distinguish-
ing it from both R. kesslerii and R. vladykovi (Fang, 1943). e present note is devoted
to a comparative description of the specimen to test this hypothesis.
Material and methods
Methods for counting n rays and scales, and for measurements, follow Kottelat and
Freyhof (2007) except that head length, postorbital length, and interorbital width in-
clude the skin fold. In the examined samples, standard length is used for some rela-
tive measurements. Body length, which is the length to the posterior margin of the
posterior-most scale on the base of the caudal n (called standard length II by Holčík
et al. (1989: g. 12), is also measured and the data are compared for diagnostic charac-

Nina G. Bogutskaya et al. / ZooKeys 825: 105–122 (2019)
108
Figure 1. Lateral view of Romanogobio antipai NMNHS specimen 68.7 mm SL, Danube at Vetren
(a)MGAB/BN760 specimen 64.9 mm SL, lower Argeş R. (b) ANSP syntype 47.8 mm SL, Sulina (c)
and R. kesslerii NMNHS, 65.7 mm SL, Tsibritsa River (d).
ters taken from the literature. All measurements were made point-to-point with a dial
caliper and recorded to the nearest 0.1 mm. Vertebral counts taken from radiographs
follow the scheme by Naseka (1996). To avoid probable discrepancy in lateral-line
count, we provide not only the number of lateral-line scales to the posterior margin of
the hypurals but also numbers of total lateral scales and total lateral-line scales. Statis-
tical analyses were done using Microsoft Excel, Statistica 6.0 (Statistic for Windows.
Statsoft; Discriminant Functional Analysis, DFA), and SPSS Statistics V23.0 (IBM
SPSS; Cluster Analysis, CA).

A recent record of Romanogobio antipai, from the Danube River in Bulgaria 109
Figure 2. Dorsal view of the head of Romanogobio antipai, NMNHS specimen 68.7 mm SL, Danube at
Vetren (a) MGAB/BN759, SL 47.7 mm, Sulina (b) ANSP syntype 47.8 mm SL, Sulina (c) and R. kesslerii
NMNHS, 65.7 mm SL, Tsibritsa River (d).

Nina G. Bogutskaya et al. / ZooKeys 825: 105–122 (2019)
110
Abbreviations
ANSP, Academy of Natural Sciences, Philadelphia, USA; NB, Bănărescu Nalbant
Ichthyology Collection (now in Muzeul de Istorie Naturala ‘Grigore Antipa’); ICBB,
Institutui of Stiinte Biologice, Bucharest, Romania; IUCN, International Union for
Conservation of Nature; MGAB, Muzeul de Istorie Naturala ‘Grigore Antipa’, Bu-
charest, Romania; NMNHS, National Museum of Natural History, Soa, Bulgaria;
NMW, Naturhistorisches Museum Wien, Vienna, Austria. BL, body length; HL, lat-
eral head length; rkm, river kilometer; SD, standard deviation; SL, standard length.
Material examined
We specically selected for comparison mostly those specimens of R. kesslerii that were
donated and/or identied by Petru Bănărescu and followed his original descrimina-
tion of the forms within the R. kesslerii species complex. Specimens of Romanogobio
vladykovi were selected from localities geographically close to Bulgaria and of a com-
parable length range.
NMNHS [no number], SL 68.7 mm, Bulgaria: Danube near Vetren, 395 rkm,
44.142637N, 27.029662E, 8 July 2016, coll. T. Stefanov.
Romanogobio antipai. All from Romania. Type material: MGAB 49908 (as Gobio kes-
sleri antipai), 1, SL 46.2 mm, labelled as holotype, Romania: [Danube at] Sulina,
before 1909, leg. G. Antipa; MGAB (ISBB 0519), 1, SL 50.8 mm, labelled as
paratype, same data as MGAB 49908; ANSP 98961 (as Gobio kessleri antipai),
1, SL ca. 47.8 mm, labelled as paralectotype (misspelled as lectoparatype), same
data as MGAB 49908, don. P. Bănărescu as paratype; non-type: MGAB (ISBB
0714, BN760, as Gobio kessleri antipai), 3, SL 64.9, 28.6 and 26.2 mm, Romania:
lower Argeş River at Olteniţa, 26 July 1961, coll. and det. P. Bănărescu; MGAB
(BN759, as Gobio kessleri antipai), 1, SL 47.7 mm, Romania: Sulina Branch, ”27–
28th miles”, Danube delta, Oct. 1992; MGAB (ISBB 3567, BN758, as Gobio kes-
sleri antipai), 1, SL 30.1 mm, Romania: Saint Gheorghe Branch, Danube delta, no
date, coll. V. Leonte. ANSP 98961 was examined on photos (lateral, dorsal, and
ventral aspects) and an X-radiograph.
Romanogobio banaticus (but see Friedrich et al. 2018: 346 on R. carpathorossicus
(Vladykov, 1931) as senior synonym of this species). NMW 65539, 30, SL 31.1–
7.9 mm, Romania: Timiş at Urseni, Timişoara, 6 Sept. 1962, don. and det. P.
Bănărescu as Gobio kesslerii banaticus.
Romanogobio kesslerii s.l.. NMW65532, 12, SL 33.3–57.9 mm, Romania: Tur at Turu-
lung, northeast of Satu-Mare, 5 Sept. 1963, don. and det. P. Bănărescu, as interme-
diate between Gobio kesslerii kesslerii and Gobio kesslerii banaticus; NMW 65538,
9, SL 39.4–74.7 mm; Romania: Milcov at Focsani, Moldau, 14 Sept. 1963, don.

A recent record of Romanogobio antipai, from the Danube River in Bulgaria 111
and det. P. Bănărescu as Gobio kessleri antipai with a comment: “not very typi-
cal”, as Gobio kessleri kessleri in Bănărescu (1999: 146); NMNHS [no number],
10, SL 55.1–66.5 mm; Bulgaria: Tsibritsa River [right tributary to Danube, NW
Bulgaria] near Yakimovo, 43.62245N, 23.33022E, 18 July 2012, coll. T. Stefanov.
Romanogobio kesslerii kesslerii. NMW 60250, 6, SL 50.1–61.2 mm; Romania: Areş Ri-
ver at mouth of Mureş, Transsylvania, 2 Oct.1949, don. and det. P. Bănărescu (in
Gobio); NMW 65535, 4, SL 50.6–61.5 mm; Romania: Bereteu at Roşiori-Bihor,
north of Oradea, 4 Sept. 1963, don. and det. P. Bănărescu (in Gobio); NMW
90883, 2, SL 85.3–91.2 mm; Ukraine: Smotrich River at Kamenetz Podol’ski
[Dniester drainage], 7 May 1921, det. P. Bănărescu, 1991 (in Gobio).
Romanogobio vladykovi. NMW 53356, 2, SL 76.7–81.4 mm; Serbia: Nisch [Niš, Great
Morava-Danube], Dec. 1894; NMW65537, 20, SL 46.4–81.4 mm; Romania:
Timiš River at Peciu Nou [Danube drainage], 28 Aug. 1863; NMW 60234, 2, SL
73.2–77.2 mm; Romania: Bega R. [Danube drainage], Banat, Sept. 1943.
Results
General appearence of the NMNHS presumed R. antipai specimen from the Danube
at Vetren is shown in Figs 1–2 together with a syntype and a non-type R. antipai speci-
men in comparison to R. kesslerii and R. vladykovi. Counts, descriptive states of the
pectoral-n length, and measurements are presented in Tables 1, 2. Examined charac-
ter states in this specimen coincide considerably with those in the three type specimens
of R. antipai and ve non-type specimens, and demonstrate its dierences from the
samples of both the R. kesslerii species complex and R. vladykovi. As the standard length
averages 96.8% of the BL (calculated in the Romanogobio material examined in this
study), the dierence between relative measurements (in % SL and in % BL) is slight
and the morphometric character states that have been considered as diagnostic for
R.antipai vs. R. kesslerii are conrmed. ey include maximum body depth, 19–25%
SL (17–25.5% of BL; in parentheses, data from Bănărescu (1953, 1961, 1999) and
Movchan and Smirnov (1981) are summarized); caudal peduncle depth, 8–9% SL (7–
9% of BL) and 35–38.5% of caudal peduncle length; eye diameter, 5–6% SL (5–6%
of BL), 20–23% HL (18–24% HL), and 59–68.5% of interorbital width (61–81%
of interorbital width). e NMNHS specimen has 6 and 4 scales, respectively, above
(to the dorsal-n origin) and below (to the pelvic-n origin) the lateral line similar to
the three type specimens of R. antipai and the topotypical specimen from Sulina thus
conrming the opinion (Kottelat and Freyhof 2007, Friedrich et al. 2018) that this
character is one of the most dependable diagnostic characters for the species. All other
counts are identical or very close in the NMNHS specimen and R. antipai examined in
this study (Table 1). None of the R. antipai specimens had 7½ branched dorsal-n rays
thus conrming its main dierence from R. vladykovi characterized by 7½ branched
dorsal-n rays (Naseka et al. 1999; Naseka 2001).

Nina G. Bogutskaya et al. / ZooKeys 825: 105–122 (2019)
112
Table 1. Meristic data for examined specimens of Romanogobio antipai and R. kesslerii species complex.
Dorsal-n
branched rays
Anal-n
branched rays
Pectoral n relative to pelvic-n origin Scales between
lateral line and
dorsal-n origin
Scales between
lateral line and
pelvic-n origin
7½ 8½ 9½ 6½ 7½ not
reaching
almost
reaching
reaching behind 5 6 2 3 4
R. antipai MGAB 49908 syntype 1 1 1 1 1
R. antipai MGAB/ISBB 0519 syntype 1 1 1 1 1
R. antipai ANSP 98961 syntype 1 1 1 1 1
Non-type MGAB R. antipai, n=5 5 1 4 1 5 5
Presumed R. antipai NMNHS specimen 1 1 1 1 1
R. k. kesslerii. NMW 60250, 65535. Danube drainage, n=10 10 10 7 1 2 10 10
R. k. kesslerii. NMW 908803, Dniester drainage, n=2 2 2 2 2 2
R. banaticus. NMW 65539, Danube drainage, n=30 27 3 30 26 3 1 29 1 30
R. kesslerii s.l. NMW 65532, NW Romania, n=12 12 12 6 1 5 12 1 11
R. kesslerii s.l. NMW 65538, NE Romania, n=9 8 1 6 3 5 3 1 9 9
R. kesslerii s.l. NMNHS, NW Bulgaria, n=10 10 10 10 6 2 1 1 10 10
R. vladykovi NMW 53356, 60234, 65537, Danube drainage, n=24 24 24 24 10 14 15 9
Table 1. Continued.
Predorsal abdominal
vertebrae
Abdominal vertebrae Pre-anal caudal
vertebrae
Caudal
vertebrae
Total vertebrae
10 11 18 19 20 21 2 3 4 19 20 21 38 39 40 41 42
R. antipai ANSP 98961 syntype 1 1 1 1 1
Non-type MGAB R. antipai, n=5 2 3 4 1 3 2 5 4 1
Presumed R. antipai NMNHS, n=1 1 1 1 1 1
R. k. kesslerii NMW 60250, 65535. Danube drainage, n=10 2 8 1 8 1 7 3 3 5 2 2 7 1
R. k. kesslerii NMW 908803, Dniester drainage, n=2 2 2 2 2 2
R. banaticus. NMW 65539, Danube drainage, n=30 9 21 26 4 4 21 5 2 19 8 1 18 10 2
R. kesslerii s.l. NMW 65532, NW Romania, n=12 1 11 7 5 5 7 1 7 4 4 8
R. kesslerii s.l. NMW 65538, NE Romania, n=9 1 8 3 6 4 5 1 5 3 1 8
R. kesslerii s.l. NMNHS, NW Bulgaria, n=10 10 2 8 2 8 2 8 4 6
R. vladykovi Danube drainage, Romania and Ukraine, n=46 (from Naseka
2001).
9 37 4 38 4 12 46 8 4 29 12 3 31 11 1
R. vladykovi NMW 53356, 60234, 65537, Danube drainage, Romania
and Serbia, n=24
3 21 19 5 12 12 5 15 4 2 16 6

A recent record of Romanogobio antipai, from the Danube River in Bulgaria 113
Table 1. Continued.
Total lateral-series scales Total lateral-line scales Lateral-line scales to posterior
hypural margin
39 40 41 42 43 44 39 40 41 42 43 37 38 39 40 41 42
R. antipai MGAB 49908 syntype 1 1 1
R. antipai MGAB/ISBB 0519 syntype 1 1 1
R. antipai ANSP 98961 syntype 1 1 1
Non-type MGAB R. antipai, n=5 1 3 1 2 3 1 1 2 1 1
Presumed R. antipai NMNHS, n=1 1 1 1
R. k. kesslerii NMW 60250, 65535. Danube drainage, n=10 3 4 3 1 2 5 2 2 2 5 1
R. k. kesslerii NMW 908803, Dniester drainage, n=2 1 1 1 1 1 1
R. banaticus NMW 65539, Danube drainage, n=30 8 9 3 1 8 9 2 4 6 9 1
R. kesslerii s.l. NMW 65532, NW Romania, n=12 2 4 6 4 3 5 2 2 6 2
R. kesslerii s.l. NMW 65538, NE Romania, n=9 7 2 3 4 2 3 4 2
R. kesslerii s.l. NMNHS, NW Bulgaria, n=10 6 3 1 2 5 2 1 6 4
R. vladykovi NMW 53356, 60234, 65537, Danube drainage, Romania and Serbia, n=24 1 7 5 10 1 1 8 6 8 1 1 9 8 6

Nina G. Bogutskaya et al. / ZooKeys 825: 105–122 (2019)
114
Table 2. Measurements and counts for examined specimens of R. antipai, R. kesslerii and R. vladykovi. Gap between ranges or ranges only slightly overlapping: *
between R. antipai and R. kesslerii, ** between R. antipai and both R. kesslerii and R. vladykovi, *** between R. antipai and R. vladykovi; **** no statistical dierence;
remaining characters display statistically signicant dierences (Kruskal-Wallis test, p<0.01) but ranges overlapping.
Characters R. antipai n=6 R. kesslerii n=26 R. vladykovi n=22
R. antipai
NMNHS
min max Mean SD min max Mean SD min max Mean SD
SL, mm 68.67 46.20 68.67 54.44 9.743 45.11 74.69 59.53 5.776 46.39 81.42 60.21 10.310
Body depth at dorsal-n origin (% SL)* 25.43 18.56 25.43 20.37 2.671 15.59 18.63 16.88 0.834 17.50 23.00 19.20 1.277
Depth of caudal peduncle (% SL)* 9.20 8.13 9.20 8.49 0.388 6.33 7.67 7.04 0.358 8.30 10.15 9.06 0.416
Depth of caudal peduncle (% length of caudal peduncle)** 38.47 34.80 38.47 36.72 1.416 24.90 33.44 30.23 2.599 39.32 49.69 44.12 3.117
Predorsal length (% SL) 46.56 44.43 46.56 45.57 0.832 43.41 49.32 46.73 1.415 46.29 49.40 47.57 0.949
Postdorsal length (% SL) 41.90 37.29 41.90 39.89 1.945 39.56 47.49 43.91 1.884 39.48 43.83 41.56 1.432
Prepelvic length (% SL) 48.89 47.76 50.60 48.79 0.989 44.79 49.78 47.45 1.218 48.41 52.79 50.65 1.423
Preanal length (% SL) 70.21 69.60 72.20 70.74 0.875 67.12 73.01 69.91 1.653 69.90 76.28 73.23 1.181
Pectoral – pelvic-n origin length (% SL) 23.92 22.95 24.60 23.88 0.650 21.15 25.42 23.51 0.865 23.29 27.32 25.58 1.423
Pelvic – anal-n origin length (% SL) 23.13 21.70 23.13 22.17 0.535 18.66 24.84 21.55 1.374 20.12 24.59 22.86 1.080
Caudal peduncle length (% SL) 23.93 22.61 24.00 23.15 0.632 20.21 29.11 23.80 2.502 18.68 22.98 20.63 1.440
Pectoral-n length (% SL) 23.18 22.05 23.18 22.55 0.440 19.69 24.00 22.20 1.320 18.49 22.89 20.75 1.162
Pelvic-n length (% SL) 19.67 17.52 19.67 18.54 0.732 16.13 19.10 17.94 0.743 14.22 18.69 16.35 1.266
Head length (% SL)**** 25.99 24.80 25.99 25.34 0.499 23.35 27.20 25.75 0.986 24.05 27.60 26.21 0.794
Head length (% body depth) 102.23 102.23 132.63 121.08 10.537 127.58 186.49 153.40 11.409 111.64 156.60 137.16 11.096
Head depth at nape (% SL)* 17.21 14.90 17.21 16.10 0.791 13.06 15.84 14.38 0.734 14.60 16.57 15.79 0.531
Head depth at nape (% HL) 66.22 59.30 68.70 64.48 3.209 52.81 59.43 55.82 1.971 57.09 64.32 60.27 1.975
Barbel length (%HL) 34.29 34.29 47.90 41.41 5.128 26.90 50.00 39.45 5.569 25.42 40.21 31.97 4.092
Maximum head width (% SL)** 15.42 14.61 16.20 15.38 0.653 13.13 15.19 13.83 0.547 12.90 15.77 14.70 0.767
Maximum head width (% HL) 59.33 58.20 64.00 61.25 2.719 50.03 56.98 53.64 2.192 49.83 59.08 55.98 2.024
Snout length (%SL)**** 11.33 8.40 11.33 9.75 0.997 8.94 11.98 10.57 0.625 9.07 11.74 10.16 0.696
Snout length (%HL) 43.59 36.00 43.60 39.40 2.654 37.86 46.38 41.04 2.337 35.93 42.79 38.75 1.903
Eye horizontal diameter (% SL)** 5.24 5.20 5.94 5.49 0.285 5.78 8.15 6.63 0.642 6.36 8.28 7.48 0.463

A recent record of Romanogobio antipai, from the Danube River in Bulgaria 115
Characters R. antipai n=6 R. kesslerii n=26 R. vladykovi n=22
R. antipai
NMNHS
min max Mean SD min max Mean SD min max Mean SD
Eye horizontal diameter (% HL)*** 20.17 20.17 23.97 22.06 1.301 22.72 29.97 26.25 1.809 24.69 32.29 28.54 1.874
Eye horizontal diameter (% interorbital width)** 58.73 58.73 67.50 63.35 4.101 75.25 130.37 103.18 14.774 86.33 121.43 103.22 7.479
Postorbital distance (% HL)**** 44.15 43.20 48.76 45.89 2.111 37.27 48.97 42.38 2.756 37.93 45.81 41.91 2.408
Interorbital width (% SL)* 8.93 8.15 8.93 8.56 0.375 5.23 8.33 6.56 0.811 6.74 7.96 7.26 0.368
Interorbital width (% HL)** 34.34 32.48 35.78 34.25 1.316 19.46 31.26 25.45 2.970 25.12 30.25 27.70 1.384
Number of predorsal vertebrae**** 11 10.00 11.00 10.67 0.516 10.00 11.00 10.50 0.510 10.00 11.00 10.82 0.395
Number of abdominal vertebrae*** 19 19.00 19.00 19.00 0.000 18.00 21.00 19.42 0.703 20.00 21.00 20.18 0.395
Number of caudal vertebrae 21 20.00 21.00 20.83 0.408 19.00 21.00 20.00 0.632 19.00 21.00 19.91 0.610
Number of preanal caudal vertebrae 4 3.00 4.00 3.50 0.548 2.00 3.00 2.58 0.504 2.00 3.00 2.45 0.510
Total vertebrae**** 40 39.00 40.00 39.83 0.408 38.00 41.00 39.42 0.809 39.00 41.00 40.09 0.610
Dierence between abdominal and caudal numbers*** -2 -2.00 -1.00 -1.83 0.408 -2.00 2.00 -0.58 1.065 -1.00 2.00 0.27 0.827
Dorsal-n branched rays (without ½)*** 8 8.00 8.00 8.00 0.000 8.00 8.00 8.00 0.000 7.00 7.00 7.00 0.000
Scales in lateral row 44 41.00 44.00 42.67 1.033 40.00 42.00 41.08 0.744 39.00 43.00 41.14 1.037
Lateral-line scales (total)*** 43 41.00 43.00 42.00 0.894 39.00 42.00 40.73 1.002 39.00 43.00 41.00 1.024
Lateral-line scales (to posterior margin of hypurals)*** 42 39.00 42.00 40.33 1.366 38.00 40.00 38.88 0.766 37.00 40.00 38.77 0.869
Scales above lateral line* 6 6.00 6.00 6.00 0.000 4.00 5.00 4.96 0.196 5.00 6.00 5.59 0.503
Scales below lateral line* 4 4.00 4.00 4.00 0.000 3.00 3.00 3.00 0.000 3.00 4.00 3.32 0.477

Nina G. Bogutskaya et al. / ZooKeys 825: 105–122 (2019)
116
Note on syntypes of R. antipai
As already claried (Kottelat 1997), the species group name antipai is based on 13 syn-
types (Bănărescu 1953: 300) without any catalogue numbers. Soon after, Bănărescu
(1961: 344) designated a holotype (“Mus. Gr. Antipa Bukarest, Col. Ichth. Nr. 4) but
this action is not valid (Art. 74.5 of the International Code of Zoological Nomenclature;
International Commission on Zoological Nomenclature 1999). e referred article of
the Code says that a subsequent use of the term “holotype” does not constitute a valid
lectotype designation unless (italics ours) the author, when wrongly using that term, ex-
plicitly indicated that he or she was selecting from the type series that particular specimen
to serve as the name-bearing type. We do not know a publication by Petru Bănărescu
where he used the term holotype for that specimen explicitly indicating its name-bearing
role. However, it cannot be excluded that a valid lectotype designation has been already
undertaken by someone because the ANSP syntype is labelled as a paralectotype.
Comparisons
The three examined samples of Romanogobio kesslerii s.l. demonstrate a statistically sig-
nicant dierence in ten morphometric and ve meristic characters (Table 3) but the
ranges of character values overlap considerably and the number of specimens is small.
We combined all specimens in a single sample in order to estimate general ranges of
character values without a special analysis of variation within the R. kesslerii complex.
As can be seen from Table 2, examined specimens of R. antipai including the
NMNHS specimen from the Danube at Vetren, most clearly (with a gap or ranges
only slightly overlapping) dier from both R. kesslerii and R. vladykovi by the caudal
peduncle depth (35–38.5% caudal peduncle length vs 25–33 and 39–50, respectively),
a wider head (58–64% HL vs 50–59), a smaller eye (5–6% SL and 59–67.5% inter-
orbital width vs 6–8 and 75–130), and a wider interorbital space (32.5–36% HL vs
19.5–31; 8–9% SL vs 5–8) with shallow orbital notches (Fig. 2a–c). Romanogobio
antipai can be further distinguished from R. kesslerii, besides the number of scales
above and below the lateral line (6 and 4, respectively, in all examined R. antipai vs
commonly 5 and 3 in R. kesslerii s.l.), by a deeper body (19–25% SL vs 16–19), a
deeper caudal peduncle (8–9% SL vs 6–8), and a deeper head (59–69% HL vs 53–59).
Besides morphometric characters mentioned above, all examined specimens of R.
antipai including the NMNHS specimen can be clearly distinguished from R. vladykovi
by the number of branched dorsal-n rays, 8½, in contrast to 7½ found in all specimens
of R. vladykovi examined in this study. Naseka (2001: 111) mentioned that 8½ rays can
be rarely found in R. vladykovi; a revision of his primary data (radiographs) revealed a
single specimen with 8½ branched dorsal-n rays out of 46 examined. Romanogobio
antipai further diers from R. vladykovi by the vertebral structure (Table1, 2) hav-
ing abdominal+caudal counts 19+21 or 20+21, which means that the caudal region is
longer than the abdominal region vs. commonly (in 52 out of 70 specimens) 20+20 or
21+21 or variants with a caudal region shorter than the abdominal one.

A recent record of Romanogobio antipai, from the Danube River in Bulgaria 117
A DFA (Fig. 3) showed dierentiation of the three groups of samples identied
as R. antipai, R. kesslerii and R. vladykovi (the number of unbranched dorsal-n rays
was excluded from the analysis as demonstrating zero variability within the groups)
and the groups were 100% classied as predicted (Table 4). A CA (Fig. 4) supported
the grouping.
To conclude, the analysis conrmed previously reported discriminating character
states (number of branched dorsal-n rays, relative size of the eye and the interorbital
space, relative depth of the caudal peduncle) and introduces a new character (verte-
bral counts) for discriminating Romanogobio antipai from R. kesslerii and R. vladykovi.
However, relative taxonomic status of these three species still waits for a phylogenetic
analysis based on molecular data. It cannot be excluded that R. antipai is a deep-water
ecophenotype of either R. kesslerii or R. vladykovi. e new record demonstrates that R.
antipai is still extant in the lower Danube but at present can only be found at a greater
depth in the main channel and the deltaic branches. Currently classied as Extinct us-
ing IUCN criteria, the conservation status of Romanogobio antipai needs revision, in
light of the new record from 2016.
Figure 3. DFA (Euclidean distance, complete linkage clustering algorithm), distribution of discriminant
scores along two canonical discriminant functions established to discriminate between three groups of
samples (R. antipai, R. kesslerii and R. vladykovi). Solid circle corresponds to NMNHS specimen identied
as Romanogobio antipai.

Nina G. Bogutskaya et al. / ZooKeys 825: 105–122 (2019)
118
Table 3. Measurements and counts for examined specimens of Romanogobio kesslerii species complex. * refers to characters demonstrating statistically signicant
dierences (Kruskal-Wallis test, p<0.01).
Characters R. kesslerii Danube n=10 R. kesslerii Romania n=6 R. kesslerii Bulgaria n=10
min max Mean SD min max Mean SD min max Mean SD
SL, mm 50.10 63.42 59.06 3.952 45.11 74.69 57.37 10.157 55.06 66.51 61.31 3.584
Body depth at dorsal-n origin (% SL) 15.59 17.93 16.81 0.916 16.54 18.30 17.39 0.649 15.73 18.63 16.65 0.787
Depth of caudal peduncle (% SL)* 7.08 7.67 7.37 0.195 6.79 7.34 7.04 0.211 6.33 7.08 6.70 0.214
Depth of caudal peduncle (%length of caudal peduncle) 24.90 33.24 28.84 3.215 28.24 32.85 31.17 1.629 27.17 33.44 31.05 1.865
Predorsal length (% SL) 46.10 48.81 47.39 0.874 44.23 46.70 45.90 0.934 43.41 49.32 46.56 1.826
Postdorsal length (% SL)*44.25 47.49 45.58 1.260 41.26 44.25 43.27 1.133 39.56 44.64 42.63 1.537
Prepelvic length (% SL) 46.33 49.78 47.84 1.324 46.27 48.69 47.32 0.976 44.79 49.33 47.15 1.250
Preanal length (% SL) 67.12 73.01 70.44 2.227 68.81 71.04 69.90 0.842 67.14 71.01 69.39 1.274
Pectoral – pelvic-n origin length (% SL) 22.95 23.89 23.27 0.335 23.18 25.18 23.92 0.705 21.15 25.42 23.51 1.230
Pelvic – anal-n origin length (% SL) 18.66 22.29 21.06 1.307 20.72 22.16 21.34 0.467 18.91 24.84 22.16 1.644
Caudal peduncle length (% SL)*24.49 29.11 26.35 1.642 21.15 24.14 23.18 1.139 20.21 23.70 21.62 1.099
Pectoral-n length (% SL)*22.82 24.00 23.24 0.362 20.43 23.99 22.47 1.167 19.69 23.09 21.01 1.063
Pelvic-n length (% SL) 17.69 19.10 18.36 0.451 17.19 18.71 18.09 0.508 16.13 18.74 17.44 0.832
Head length (% SL) 25.54 27.20 26.40 0.458 23.35 26.66 25.47 1.181 24.25 26.86 25.28 0.977
Head length (% body depth) 144.23 186.49 158.35 12.847 127.58 159.58 147.35 11.663 139.47 170.77 152.09 8.209
Head depth at nape (% SL)* 13.97 15.84 14.91 0.697 13.83 14.97 14.49 0.410 13.06 14.56 13.79 0.454
Head depth at nape (% HL) 53.04 59.43 56.36 2.349 54.72 59.23 57.01 1.428 52.81 56.20 54.56 1.058
Barbel length (% HL) 32.95 47.64 39.49 5.449 37.63 50.00 43.50 4.540 26.90 43.61 36.99 5.233
Maximum head width (% SL) 13.18 14.30 13.61 0.404 13.13 15.19 14.08 0.657 13.21 14.73 13.91 0.571
Maximum head width (% HL)*50.03 52.57 51.25 0.976 53.24 56.98 55.35 1.504 53.15 56.43 55.01 0.861
Snout length (% SL)*10.37 11.20 10.69 0.264 8.94 10.41 9.85 0.534 10.21 11.98 10.89 0.616
Snout length (% HL)*39.37 42.13 40.40 0.869 37.86 39.61 38.66 0.687 38.32 46.38 43.12 2.260
Eye horizontal diameter (% SL) 6.20 8.15 7.03 0.772 5.78 7.26 6.47 0.570 5.92 6.77 6.31 0.244
Eye horizontal diameter (% HL) 25.14 29.97 27.47 1.896 25.31 27.57 26.29 0.802 22.72 27.36 25.00 1.321
Eye horizontal diameter (% interorbital width) 78.47 130.37 103.10 18.289 75.25 112.80 93.59 14.198 97.90 122.36 109.01 7.799

A recent record of Romanogobio antipai, from the Danube River in Bulgaria 119
Characters R. kesslerii Danube n=10 R. kesslerii Romania n=6 R. kesslerii Bulgaria n=10
min max Mean SD min max Mean SD min max Mean SD
Postorbital distance (% HL) 39.71 48.97 43.11 3.323 42.00 45.47 43.86 1.350 37.27 43.56 40.75 2.001
Interorbital width (% SL)*6.04 7.90 7.00 0.635 6.39 8.33 7.06 0.709 5.23 6.24 5.81 0.367
Interorbital width (% HL)*22.93 30.92 26.52 2.674 25.06 31.26 27.71 2.241 19.46 25.43 23.03 1.827
Number of predorsal vertebrae*10 11 10.80 0.422 10 11 10.83 0.408 10 10 10.00 0.000
Number of abdominal vertebrae*19 21 20.00 0.471 19 20 19.50 0.548 18 19 18.80 0.422
Number of caudal vertebrae 19 21 19.90 0.738 20 21 20.50 0.548 19 20 19.80 0.422
Number of preanal caudal vertebrae 2 3 2.30 0.483 2 3 2.67 0.516 2 3 2.80 0.422
Total vertebrae*39 41 39.90 0.568 40 40 40.00 0.000 38 39 38.60 0.516
Dierence between abdominal and caudal numbers -2 20.10 1.101 -2 0-1.00 1.095 -2 0-1.00 0.667
Dorsal-n branched rays (without ½) 8 8 8.00 0.000 8 8 8.00 0.000 8 8 8.00 0.000
Scales in lateral row*41 42 41.50 0.527 41 42 41.33 0.516 40 42 40.50 0.707
Lateral-line scales (total) 40 42 41.10 0.994 40 42 41.00 0.894 39 42 40.20 0.919
Lateral-line scales (to posterior margin of hypurals)* 39 40 39.50 0.527 38 40 38.67 0.816 38 39 38.40 0.516
Scales above lateral line 4 5 4.90 0.316 5.0 55.00 5.0 5 5 5.00 0.000
Scales below lateral line 3 3 3.00 0.000 3.0 33.00 3.0 3 3 3.00 0.000

Nina G. Bogutskaya et al. / ZooKeys 825: 105–122 (2019)
120
Figure 4. CA (SPSS, k-means) for three groups of samples (R. antipai, R. kesslerii and R. vladykovi). No
1 refers to NMNHS specimen identied as Romanogobio antipai.

A recent record of Romanogobio antipai, from the Danube River in Bulgaria 121
Acknowledgements
NGB was supported by Lise Meitner Programme of National Science Foundation of
Austria (M 2183-B25). Our sincere thanks go to Ernst Mikschi and all other members
of the NMW Fish Collection, and Melanya Stan and Alexandru Iftime (MGAB), for
their valuable help in studying the collections under their care; Mark Sabaj Pérez and
Kyle Luckenbill (ANSP) for sending photos and a radiograph of a R. antipai syntype;
and to Alice Schumacher (NMW) for making photos of NMW specimens.
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