Gammarus orientalis, Dana, 1852

Karaman, Gordan S., 2017, New data of poorly known species Gammarus orientalis (S. Karaman, 1934) (family Gammaridae) from Asia Minor (Contribution to the Knowledge of the Amphipoda 292), Ecologica Montenegrina 7, pp. 639-653 : 640-652

publication ID	https://doi.org/ 10.37828/em.2016.7.30
persistent identifier	https://treatment.plazi.org/id/0E4EEF24-FFAF-3233-FDA6-FA6ABA98FAD7
treatment provided by	Felipe
scientific name	Gammarus orientalis
status

Treatment

Gammarus orientalis (S. Karaman, 1934)

Rivulogammarus balcanicus orientalis View in CoL S. Karaman, 1934: 131, fig. 4 View Figure 4 ;

Gammarus balcanicus View in CoL (part.) G. Karaman & Pinkster, 1987: 211.

Material examined:

S-5924= Derbend , eastern site of Erdschias- dag (=Erciyas-dagi), Asia Minor ”, 2100 m about sea level, 20 exp., 3.6.1902 (leg.?) [holotype and paratypes] ;

-445= “Ostseite des Erdschias Dagh (=Erciyas-dagi), 3.6. 1902, 10 exp. (leg.?)”;

S-2169= (-540) Eastern side of Erdschias Dagh (=Erciyas-dagi), 3.6. 1902, 5 exp. (leg.?).

Description

Male 8.0 mm, paratype: Body relatively small, metasomal segments smooth, with 4-6 dorsoposterior marginal short setae each ( fig. 3D View Figure 3 );

Epimeral plates 1-3 with distinctly pointed ventroposterior corner ( fig. 3D View Figure 3 ), along posterior margin with 3-5 short setae. Epimeral plate 2 is provided with 2 subventral spines, epimeral plate 3 with 4 subventral spines.

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 View Figure 4 ); 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 1- peduncle.

Head with short rostrum and subrounded lateral cephalic lobes; eyes ovoid, not exceeding the diameter of antenna 1 peduncular article 1 ( fig. 1A View Figure 1 ).

Antenna 1 reaching half of the body-length; peduncular articles 1-3 progressively shorter, provided with several short setae only ( fig. 1B View Figure 1 ); main flagellum consisting of 19 articles scarcely setose ( fig. 1B, C View Figure 1 ), setae are much shorter than diameter of articles. Accessory flagellum slightly shorter than last peduncular article, consisting of 3-4, exceptionally only 2 articles ( fig. 1B, D View Figure 1 ).

Antenna 2 moderately slender, peduncular articles 4 and 5 nearly of equal length ( fig. 1E View Figure 1 ), 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) ( fig. 1E View Figure 1 ), calceola not observed. Antennal gland cone as long as or shorter than peduncular article 3 ( fig. 1E View Figure 1 ).

The mouthparts are basically the same as in other Gammarus species. Left mandible: incisor with 5 irregular teeth, lacinia mobilis with 4 teeth ( fig. 3B View Figure 3 ); right mandible with incisor provided with 4 irregular teeth, lacinia mobilis divided, bearing several small teeth ( fig. 3A View Figure 3 ). Mandibular palpus article 1 naked; palpus article 2 with 7 lateral setae ( fig. 3C View Figure 3 ); palpus article 3 shorter than article 2, subfalciform, along inner margin with 16-17 lateral D-setae, on tip with 5 long E-setae ( fig. 3A View Figure 3 ); on outer face is attached one group of 3 A-setae, on inner face is attached one group of 3 B-setae; C-setae absent.

Coxae 1-4 of the moderate size. Coxa 1 slightly longer than broad, with nearly straight of poorly concave anterior margin, along subrounded ventral margin appear scarce number of very short setae ( fig. 2A View Figure 2 ). Coxa 2 longer than broad, poorly tapering ventrally, with subrounded ventral margin bearing 4-5 very short marginal setae ( fig. 2C View Figure 2 ).

Coxa 3 much longer than broad, with nearly parallel lateral margins; ventroanterior corner is more subrounded than ventroposterior one; ventral margin bearing 3-4 short marginal setae ( fig. 3E View Figure 3 ). Coxa 4 longer than broad, with subrounded ventral margin bearing several short setae, ventroposterior lobe developed ( fig. 3F View Figure 3 ).

Coxae 5-7 progressively smaller. Coxa 5 and coxa 6 bilobed, with anterior lobe more narrow that posterior one, posterior lobe subrounded; both lobes with single very short setae only ( fig. 4A, C View Figure 4 ). Coxa 7 shallow, with concave ventral margin ( fig. 4D View Figure 4 ).

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 View Figure 2 ); 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 View Figure 2 ). 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 View Figure 2 ).

Gnathopod 2: article 2 along both margins with numerous long setae; article 3 at posterior margin with one distal bunch of setae ( fig. 2C View Figure 2 ); 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 View Figure 2 ); 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 View Figure 2 ).

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 View Figure 3 ). 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.

Pereopod 4: likes to pereopod 3 but less setaceous and setae are shorter ( fig. 3F View Figure 3 ). Posterior margin of article 4 with 4 bunches of several short setae each; posterior margin of pereopod 5 with 4 bunches of short spines and single short setae; article 6 along posterior margin with 4 groups of short spines and single short setae ( fig. 3F View Figure 3 ). Dactylus short and strong.

Pereopods 5-7 rather stout. Pereopod 5 is slightly shorter than pereopods 6 and 7 ( fig. 4A, C, D View Figure 4 ). 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 View Figure 4 ). 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 View Figure 4 ).

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 View Figure 4 ).

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 View Figure 4 ). 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.

Pleopods 1-3 with 2 retinacula each, peduncles are poorly setose.

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 View Figure 1 ]; second article very short, not reaching diameter of article 1 ( fig. 1F View Figure 1 ; 5C View Figure 5 ). Uropod 3 of holotype male is moderately setose ( fig. 5C View Figure 5 ): 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 View Figure 1 ).

Coxal gills large, ovoid, appear on gnathopod 2 and pereopods 3-7 ( figs. 2C View Figure 2 ; 3E View Figure 3 ; 4A, C, D View Figure 4 ).

Female 7.8 mm (paratype), ovigerous, with 11 eggs: Rather similar to the males, but stouter and generally more setaceous.

Head, mesosomal and metasomal segments like these in male ( fig. 5E View Figure 5 ). Epimeral plates 1-3 distinctly pointed, plates 1 and 2 with convex posterior margin bearing several short setae; epimeral plate 3 along posterior almost straight margin bearing 3-5 short setae ( fig. 5E View Figure 5 ); epimeral plate 2 with 2 subventral spines, epimeral plate 3 with 3 subventral spines ( fig. 5E View Figure 5 ).

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 View Figure 5 ).

Coxae 1-4 rather similar to these of male. Coxa 1 longer than broad, with almost parallel lateral margins and subrounded ventral margin bearing several very short setae ( fig. 8A View Figure 8 ). Coxa 2 longer than broad, subrounded ventral margin is provided with 3-4 short setae ( fig. 8C View Figure 8 ). Coxa 3 remarkably longer than broad, with parallel lateral margins and subrounded ventral margin bearing 3-4 short setae ( fig. 6B View Figure 6 ).

Coxa 4 longer than broad, ventroposterior lobe developed but shallow, ventral margin convex, with several short setae ( fig. 6C View Figure 6 ).

Coxa 5-7 progressively smaller. Coxa 5 broader than long, with anterior lobe more narrow than posterior one, only single short marginal setae are present ( fig. 7A View Figure 7 ). Coxa 6 bilobed, posterior lobe much larger than anterior one, with marked ventroposterior corner ( fig. 7B View Figure 7 ). Coxa 7 broader than long, with shallow ventral concave margin and with single marginal setae at anterior margin ( fig. 7C View Figure 7 ).

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 View Figure 8 ); 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 View Figure 8 ).

Gnathopod 2: article 2 along both margins with long setae ( fig. 8C View Figure 8 ); 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 View Figure 8 ); palm moderately inclined, relatively short and without median palmar spine, but defined by 2 short corner spines ( fig. 8D View Figure 8 ); dactylus curved, with one median seta at outer margin ( fig. 8C View Figure 8 ).

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 View Figure 6 ). 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 View Figure 6 ). 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 View Figure 6 ); 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 View Figure 6 ).

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 View Figure 7 ). 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 View Figure 7 ). 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 View Figure 7 ). At anterior proximal corner of inner face on article 2 are implanted several setae ( fig. 7B View Figure 7 ). 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 View Figure 7 ); 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 View Figure 7 ); 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 View Figure 7 ). 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 View Figure 7 ) (unknown size) is moderately short, peduncle with median and several distal spines. Inner ramus longer than peduncle (ratio: 60:50), exceeding half of outer ramus-length ( fig. 7D View Figure 7 ) (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 View Figure 7 ); 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 View Figure 6 ); 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 View Figure 6 ), along inner margin with 2 median and bunch of distal setae; Outer ramus 2- articulated, 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 View Figure 6 ).

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 View Figure 5 ).

Coxal gills are broad ( fig. 6B View Figure 6 ). Oostegites large, with long marginal setae ( fig. 6B View Figure 6 ).

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 View Figure 6 ; 7D View Figure 7 ) with rather variable pilosity.

Uropod 3 of male and female, of holotype and paratype of Stanko Karaman`s slide ( figs. 5C View Figure 5 , 7D View Figure 7 ) 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 View Figure 1 , 6D View Figure 6 ).

Urosomal dorsal groups of spines and setae are rather variable, but always all groups of elements are present ( fig. 4E View Figure 4 ; 5D View Figure 5 ; 7E View Figure 7 ), sometimes the median groups of elements on urosomal segment 1 is consisting of two groups of setae only.

Antenna 1 is always scarcely setose ( fig. 1B View Figure 1 ; 5A View Figure 5 ). Antenna 2 is moderately slender ( figs. 1E View Figure 1 ; 6B View Figure 6 ), on Karaman`s slides dilated by slide-cover ( fig. 5B View Figure 5 ), flagellum without visible calceola. Accessory flagellum consisting of 3-4 articles, exceptionally only 2 articles ( fig. 1B, 1D View Figure 1 ).

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.

Locus typicus: “Derbend, on the eastern site of Erdschias- dag (=Erciyas-dagi), Asia Minor, on 2100 m a.s.l.”

Holotype: male nearly 8 mm on slide. Holotype and paratypes are deposited in Karaman`s Collection in Podgorica , Montenegro .

Distribution: known from type-locality only.

Remarks and affinities

Stanko Karaman (1934) described the specimens from Derbend as Rivulogammarus balcanicus orientalis , n. ssp., based on scarce setation of pereopods 3 and 4,

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.