New data of poorly known species Gammarus orientalis (S. Karaman, 1934) (family Gammaridae) from Asia Minor (Contribution to the Knowledge of the Amphipoda 292)

The poorly known taxon Gammarus orientalis (S. Karaman, 1934), described and known from Derbend in Erdschias-dag Mts (=Erciyas-dagi), on 2100 m about sea level (Asia Minor) is described and figured based on holotype and paratypes. As the known taxonomic characters of this taxon were scarce and incomplete, this taxon was considered the synonym of Gammarus balcanicus Schäferna, 1922. The established morphological characters and geographical distribution of orientalis support distinct status of this taxon.

G. Karaman & Pinkster (1977a, 1977b, 1987 working on revision of freshwater members of genus Gammarus from Europe, Asia Minor and Near East, in attempt to facilitate the recognition of single taxa, have divided all species into 3 artificial groups: -Gammarus balcanicus Group [taxa with scarce pilosity of pereopods 3 and 4]; -Gammarus pulex Group [taxa with densely setose pereopods 3 and 4]; and Gammarus roeselii Group [taxa with dorsal carina or teeth on metasome].

Research Article
G. Karaman (1977) put together numerous populations of Gammarus balcanicus Group, known under various names from former Yugoslavia, into single large taxon, Gammarus balcanicus Schäferna, 1922, based on large similar variability of taxonomical characters.
The recent molecular and genetic investigations of many different populations of Gammarus balcanicus Group in Europe, provided by various scientists (Mamos et al., 2014;Mamos et al., 2016, etc) indicated that Gammarus balcanicus (sensu auctorum) is composed of numerous distinct taxa, and these studies are still in the process.
Some of these taxa have distinct characters and are easy to recognize (G. pljakici, etc.); some other taxa show large morphologic variability and mosaic spread of taxonomical characters, what made very difficult or impossible separation of single taxa based on morphological characters only, and were usually attributed to the Gammarus balcanicus complex only. It is necessary to analyze taxonomical characters of each of these taxa combined with molecular and genetic investigations to obtain a real position of these taxa and its validity. Our redescription of Gammarus orientalis from morphological aspect is our attempt to facilitate the recognition of single known taxa (species, subspecies or forms) within the G. balcanicus-Complex.

Material and Methods
The studied material was partially dried and later preserved in 70% ethanol. For recovering of dried specimens we used the method of Thompson, J.R., Thompson, M.H. & Drummond (1966).
The specimens were dissected using a WILD M20 microscope and drawn using a camera lucida attachment. All dissected appendages were submersed in the mixture of glycerin and water for study and drawing. The body-length of examined specimens was measured from the tip of head to the end of telson using camera lucida. All illustrations were inked manually. After the end of the study, the dissected bodyparts were submerged in Liquid of Faure and covered by thin cover glass.
Some morphological terminology and seta`s formulae follow Karaman`s terminology (Karaman, G. 1969a;2012) for setae of last mandibular palpus article [A= setae on outer face; B= setae on inner face; C= additional setae on outer face; D= lateral marginal setae; E= distal long setae]. Term "setae" and "spines" are used based on its shape, not origin.
The advantage of use of Liquid of Faure is the possibility to remove the dissected body-parts from Liquid of Faure by water, and study it again in the various positions under the microscope. The work is based on provided morphological and ecological investigations and data.
Urosome low, not compressed laterally; urosomal segments 1-2 with mid-dorsal and dorsolateral groups of elements (each group consisting of 1-2 spines and 1-2 setae as long as or slightly longer than spines ( fig. 4E); median group is composed of 2 poorly separated groups of spines and/or setae. Urosomal segment 3 on each dorsolateral side with group of 2-3 spines and 1-2 short setae, dorsomedian group is composed of 2 median setae.
Urosomal segment 1 on each ventroposterior corner with 1 weak spine near basis of uropod 1peduncle.
Head with short rostrum and subrounded lateral cephalic lobes; eyes ovoid, not exceeding the diameter of antenna 1 peduncular article 1 ( fig. 1A).
Antenna 2 moderately slender, peduncular articles 4 and 5 nearly of equal length ( fig. 1E), each of them with bunches of short setae along ventral margin; several short setae are attached laterally and dorsally of the articles also. Flagellum moderately slender, slightly longer than last peduncular article and consisting of 11 articles bearing several setae each (setae are as long as or slightly longer than diameter of articles themselves) ( Gnathopods 1-2 of moderate subequal size, but of different shape. Gnathopod 1: article 2 along anterior and posterior margin with numerous long setae in proximal part, and shorter setae in distal part (fig. 2A); article 3 along posterior margin with one distal bunch of setae; article 5 is shorter than article 6, along anterior margin with one median and one distal bunch of short setae, along posterior margin with 4-5 transverse rows of short setae ( fig. 2A). Propodus almost ovoid, tapering distally, along posterior margin with 4 transverse rows of relatively short straight setae; palm with irregular margin provided with numerous spines and short setae. Dactylus curved, along outer margin with one median seta ( fig. 2B).
Gnathopod 2: article 2 along both margins with numerous long setae; article 3 at posterior margin with one distal bunch of setae (fig. 2C); article 5 shorter than article 6, along anterior margin with one median and one distal bunch of setae, along posterior margin with 5 transverse rows of setae. Propodus longer than broad, with parallel lateral margins, along posterior margin with 8 transverse rows of setae (fig. 2D); palm concave in the middle, with 2-3 corner and one median palmar spine accompanied by 3-4 long setae; dactylus along outer margin with one median seta ( fig. 2D).
Pereopods 3-4 moderately slender and relatively scarcely setose. Pereopod 3 is rather longer than pereopod 4, article 2 along anterior and posterior margin with long straight setae ( fig. 3E). Article 4 along posterior margin with 5 bunches of straight setae nearly as long as diameter of article itself; article 5 along posterior margin with 4 groups of single spines and several straight setae nearly as long as diameter of article itself; article 6 along posterior margin with 4 bunches of single short spine accompanied by 1-2 short setae; dactylus short and strong, at inner margin with slender median spine-like seta.        Pereopods 5-7 rather stout. Pereopod 5 is slightly shorter than pereopods 6 and 7 ( fig. 4A, C, D). Pereopod 5: article 2 (basipodit) only slightly longer than broad, almost quadrate, along anterior margin with row of single short marginal spines, along posterior margin with 8-9 very short setae, ventroposterior dilatation not forming a lobe ( fig. 4A). Articles 4-6 along anterior and posterior margin with groups of short spines (spines are much shorter than diameter of articles themselves), accompanied sometimes with single very short simple seta. Dactylus short and strong, at inner margin with one spine-like seta near basis of the nail, along outer margin with 1 median short seta; nail much shorter than pedestal ( fig. 4B).
Pereopod 6: article 2 remarkably longer than broad, along anterior margin with row of 4-5 single short spines and one proximal bunch of setae; posterior margin is slightly concave in the middle and bears 8-9 short setae, ventroposterior dilatation not forming a lobe; dactylus short and strong ( fig. 4C).
Pereopod 7 nearly as long as pereopod 6; article 2 longer than broad, tapering distally, along anterior margin with row of several short single spines and with proximal bunch of setae; along posterior convex margin appear nearly 12 short setae. At ventroposterior corner of inner face of article 2 appear one spine and 2 short setae ( fig. 4D). Articles 4-6 along anterior and posterior margin with bunches of short spines accompanied sometimes with single short seta; dactylus like that of pereopod 5.
Uropod 1: peduncle with dorsoexternal row of spines, dorsointernal margin with distal spines only. At proximal outer face of peduncle appear one spine; inner ramus hardly longer than outer one or almost equal, both rami with lateral and distal spines.
Uropod 2: inner ramus slightly longer than outer one. Uropod 3: many setae on uropod 3 of male 8.0 mm paratype are missing (broken) ( fig. 1F]; second article very short, not reaching diameter of article 1 ( fig. 1F; 5C). Uropod 3 of holotype male is moderately setose ( fig. 5C): inner ramus reaching ½ of outer ramus-length, along inner (mesial) margin are attached plumose setae and single short spines, along outer margin appear plumose setae; at the tip of inner ramus appear 2 short spines and setae. Outer ramus 2-articulated: first article along inner (mesial) margin with several plumose setae, along outer margin with several bunches of short spines and single longer plumose setae.
Telson only slightly longer than broad (ratio: 70:65), tapering distally; each lobe on top bearing 2 short spines accompanied by 2-3 setae (the longest setae are slightly longer than spines); each lobe with 2 groups of short setae or one short spine and 2 setae ( fig. 1G).
Female 7.8 mm (paratype), ovigerous, with 11 eggs: Rather similar to the males, but stouter and generally more setaceous.
Urosome low, not compressed laterally; urosomal segments 1 and 2 on each dorsolateral side with bunch of 1-2 spines and single short setae, median group of spines and setae divided into 2 bunches. Dorsolateral groups on urosomal segment 3 consisting of 3 spines; median group on urosomal segment 3 consisting of 2 setae only ( fig. 5E).
Gnathopods 1-2 smaller and weaker that these in male. Gnathopod 1: article 2 along anterior and posterior margin with numerous long setae, being shorter towards distal part of article (fig. 8A); article 3 with one group of setae at posterior margin. Article 5 slightly shorter than propodus and provided with 2 bunches of setae along anterior margin; along posterior margin are attached 3 transverse rows of setae. Propodus weak, almost ovoid, longer than broad, with 3-4 transverse rows of setae and spines along posterior margin; palm inclined, bearing 2 corner spines and setae, median palmar spine absent. Dactylus curved, with one median seta along outer margin ( fig. 8A, B).
Gnathopod 2: article 2 along both margins with long setae (fig. 8C); article 3 at posterior margin with one distal bunch of setae; article 5 slightly shorter than propodus, along anterior margin with 3 bunches of setae, along posterior margin with several transverse rows of setae. Propodus weak, longer than broad, with parallel lateral margins bearing along anterior margin 2-3 bunches of setae, along posterior margin with 5 transverse rows of setae ( fig. 8C); palm moderately inclined, relatively short and without median palmar spine, but defined by 2 short corner spines ( fig. 8D); dactylus curved, with one median seta at outer margin ( fig. 8C).
Pereopods 3-4 moderately slender and more setaceous than these in male. Pereopod 3 is slightly stronger than pereopod 4, its article 2 along anterior and posterior margin with long straight setae ( fig. 6B). Articles 3, 4, and 5 along posterior margin with several bunches of straight setae (the longest setae are much longer than diameter of articles themselves). Article 4 at anterior margin with one median spine and distal bunch of longer setae, article 5 along anterior margin with distal bunch of setae. Article 6 along posterior margin with 5 groups of 1-2 short spines accompanied by single short setae ( fig. 6B). Dactylus short and strong, at inner margin with one spine-like seta near basis of the nail.
Pereopod 4: similar to pereopod 3 but slightly smaller and less setaceous. Article 2 along both margins with long setae (fig. 6C); article 4 at posterior margin with 4 bunches of long straight setae (the longest setae are longer than diameter of article itself), along anterior margin with 2 median bunches of short setae and one distal bunch of long setae. Article 5 at posterior margin with 3 groups of short spines; single setae exceeding the diameter of article itself; article 6 at posterior margin with 4 groups of short spines and single short setae; dactylus short and strong ( fig. 6C).
Pereopods 5-7 relatively short. Pereopod 5 only slightly shorter than pereopods 6 and 7; article 2 rather longer than broad, along anterior margin with row of short spines, along posterior margin with 7-8 short setae; ventroposterior dilatation developed. At anterior proximal corner on inner face of article 2 are implanted 3 setae ( fig. 7A). Articles 4 and 5 along anterior margin with several bunches of setae up to as long as diameter of articles themselves, along posterior margin with 2 bunches of short spines ( fig. 7A). Article 6 along anterior and posterior margin with several bunches of short spines mixed with short single setae; dactylus short and strong.
Pereopod 6: article 2 longer than broad, along anterior margin with several short spines, along posterior almost straight margin with nearly 11 short setae, ventroposterior lobe not developed ( fig. 7B). At anterior proximal corner of inner face on article 2 are implanted several setae ( fig. 7B). Article 4 at anterior margin with 4 groups of spines and setae, along posterior margin with one median and 2-3 distal spines; article 5 at anterior margin with 3 groups of spines mixed with single setae; article 6 at anterior margin with 4 groups of short spines, along posterior margin with single setae and distal spines and setae.
Pereopod 7: article 2 longer than broad, along anterior margin with row of 5 short spines, along posterior convex margin appear nearly 13 short setae; ventroposterior lobe absent ( fig. 7C); on inner face of article 2 appears one subventral short spine and seta, in proximal part are implanted 2-3 long anterior setae and 2 short posterior setae ( fig. 7C); mediofacial setae on inner face of article 2 absent. Articles 4-6 scarcely setose, but along both margins with bunches of spines mixed with single short setae ( fig. 7C). Dactylus short and strong.
Pleopods 1-3 with 2 retinacula each, peduncles poorly setose. Uropods 1-2 like these in male but slightly shorter. Uropod 3 in paratype on slide ( fig. 7D) (unknown size) is moderately short, peduncle with median and several distal spines. Inner ramus longer than peduncle (ratio: 60:50), exceeding half of outer ramuslength ( fig. 7D) (ratio: 60:105), along outer margin with 2 lateral spines and several single long plumose setae, along inner (mesial) margin with one median long plumose seta ( fig. 7D); tip of inner ramus with several long simple and plumose setae and 2 spines. Outer ramus 2-articulated: first article along outer margin with 3 median and one distal groups of spines mixed with single simple setae, along inner (mesial) margin appear several plumose setae; second article short, not reaching maximal diameter of first article and bearing several longer distal simple setae.
Uropod 3 of paratype female 7.8 mm: peduncle nearly as long as inner ramus ( fig. 6D); inner ramus reaching nearly half of outer ramus (ratio: 48:95), along outer margin with 3 lateral groups of setae mixed with single spines ( fig. 6D), along inner margin with 2 median and bunch of distal setae; Outer ramus 2articulated, first article along outer margin with 3 lateral and one distal bunch of spines mixed with single setae, along inner (mesial) margin with single lateral and distal setae; second article short, with distal bunch of setae. As the specimens were dried, the setulae of plumose setae are not visible ( fig. 6D).
Telson nearly as long as broad, each lobe at tip with 2 spines and 2 short setae, and with one facial spine or 2 setae ( fig. 5F).
Variability: Female uropod 3 is slightly shorter and more setaceous than that in male, inner ramus reaching or only slightly exceeding half of outer ramus-length (figs. 6D; 7D) with rather variable pilosity. Uropod 3 of male and female, of holotype and paratype of Stanko Karaman`s slide (figs. 5C, 7D) are with well visible plumose setae; uropod 3 of paratypes males and females dried, numerous setae are broken and plumose setae are not well visible ( fig. 1F, 6D).
Urosomal dorsal groups of spines and setae are rather variable, but always all groups of elements are present ( fig. 4E; 5D; 7E), sometimes the median groups of elements on urosomal segment 1 is consisting of two groups of setae only.
Pereopods 3 and 4 in females are more setaceous than these in males. Pereopods 5-7 in females are with slightly stouter basipodites and slightly more setaceous articles 4-5 than these in males. Epimeral plates 2 and 3 with 2-4 subventral spines each, ventral setae absent.

Remarks and affinities
The comparison of specimens of Gammarus balcanicus Schäferna, 1922 from type-locality (Kolašin in Montenegro) with these of Gammarus orientalis (S. Karaman, 1934) from type-locality (Derbend in Erdschias-dag, (=Erciyas dagi, Asia Minor) show some differences: absence of calceola on antenna 2 in males, presence of dorsolateral group of elements on urosomal segment 1, slightly shorter inner ramus of uropod 3, slightly more setaceous pereopods 3-7 in females, narrower coxa 3 and 4 in males and females, etc.
Various other population of G. balcanicus (s. auct.) show large variability of taxonomical characters and different combination of single morphological characters. For this reason, it is not possible, based on morphological characters only, to recognize all single taxa; molecular, genetic and other advanced studies will help to recognize single taxa and their status.
The presence of very similar or morphologically almost identical populations within G. balcanicus Complex spread over very large distances (western Balkan-Asia Minor, Northern Italy-Crimea, etc.) indicate the probably convergence of morphological characters in various distinct taxa because of similar ecological conditions. Evidently, populations of Gammarus balcanicus (sensu auct.) are in full process of differentiation and are splitting into numerous populations more or less separated morphologically, ecologically or genetically from type-species and other populations.

Conclusion
Gammarus balcanicus Complex of taxa is composed of various taxa morphologically very similar to each other, what made the recognition of single taxa based on morphological differences only, hazardous or problematic, and needs the use also other methods combined for recognition of distinct taxa.
On the other hands, continuous differentiation and splitting of various populations on ecological, geographical, molecular and genetic basis into numerous populations on various degree of segregation, in present time, suggest that the real separation of single taxa to each other will be very difficult and sometimes conditional, what will open large field for subjective decisions of investigators which of these populations will be considered as distinct taxon or not. Finally, which type of taxa we will accept: morphospecies, ecospecies, evolutionary species, genetic species, biospecies, taxonomic species, etc.? Further investigations will make a progress in resolving of this problem.
Additional difficulty is a possible presence of seasonal variations of single taxonomical characters over the year within one population, already observed in very close genus Echinogammarus Stebbing 1899 [Echinogammarus tibaldii Pinkster & Stock 1970, forma roco and forma bolo in Italy, etc.] (G. Karaman, 1993). We observed similar morphological differences in some populations of G. balcanicus-Complex in Balkan also, although we are not sure if these differences are of seasonal or some other origin.