Gammarus morcae, Özbek & Aydin, 2023

Özbek, Murat & Aydin, Gökhan, 2023, A new amphipod from the depths of the Morca Sinkhole (Anamur, Türkiye): Gammarus morcae n. sp. (Amphipoda: Gammaridae), with notes on cavernicolous amphipods of Türkiye, Turkish Journal of Zoology 47, pp. 81-93 : 82-90

Gammarus morcae n. sp. ( Figures 2–10)

Material examined: Holotype male, 22.0 mm (ESFM-MALI/21-01), Morca Sinkhole , Anamur District, Mersin Province, Turkey, 01.vii.2021; collected by G. Aydın.

Paratypes: 4 females and 5 males (ESFM-MALI/21-02), same data as holotype .

ÖZBEK and AYDIN / Turk J Zool

Diagnose: Eyeless, unpigmented body covered with numerous simple setae ( Figures 2 and 9D), without keel or tubercles. Sexual dimorphism present (males larger than females, females more setose than males, both gnathopods sexually dimorphic). Antenna I is longer than 50% the length of the body; antenna II is about 50% the length of antenna I, gland cone long and straight. Maxilla I inner plate trapezoidal, with 11 plumose setae, outer plate with 11 multitoothed, comb-like spines; palps asymmetric. Mandibular palp article 3 with 1 group of A-setae, 1-2 groups of B-setae, 26-28 D-setae, and 4-5 E-setae; C-setae absent. All the coxal plates and epimeral plates bear numerous simple setae. Gnathopod II larger than gnathopod I; medial palmar spine present, palmar angles of both gnathopods with groups of strong palmar spines; dactyli with 1 seta along outer margin, nails with 1 setule along inner margin. Bases of pereopods V – VII with several setae on the inner and outer surfaces, proximal parts wider than the distal part, outer margin of dactyli of pereopods III–VII with 1 plumose seta. Urosomites with dorsolateral groups of spines. Dorsal and dorsolateral surfaces of the meso- and metasome segments with numerous simple setae. Pleopods I–III with 2 retinacula. Uropods I and II spinose; uropod III exopodite 1.9× longer than protopodite (in males); endopodite longer than 50% length of exopodite. Telson lobes elongated, with 3 or 4 distal spines per lobe. Coxal gills II–VII are stalked, triangular, or sacciform, gill 7 is the smallest. Body length 16.1–19.0 mm (♀♀), 17.2–23.0 mm (♂♂).

Etymology: The name of the new species is derived from the name of the type locality (Morca Sinkhole).

Description of holotype male: Body unpigmented. Antennal sinus deep. Posterior side of the head with some setae. Eyes are absent ( Figure 2). The antenna I ( Figures 2 and 3C) is longer than half of the body length, the first peduncle segment bears setae along the dorsal and ventral margin, setae much shorter than the diameter of the first peduncle segment; the second and third peduncle segments bear 3-4 groups of short setae (shorter than the segment where they implanted); the setation on the flagellar segments is weak. The length ratio of peduncular segments is 1:0.7:0.5. Main and accessory flagellum with 41 and 4 articles, respectively; flagellar segments with short simple setae in their distal parts. Aesthetasc-like structures are present on the flagellar segments (see the detail in Figure 3C).

Antenna II ( Figure 3B) is shorter than the half-length of antenna I (the length ratio is about 1:0.46). Gland cone straight and elongated, reaches the 0.25 length of the fourth peduncular segment. The fourth peduncular segment bears 11 groups of setae that are shorter than the diameter of the segment. The fifth peduncular segment bears 4 and 7 groups of setae along the dorsal and ventral margins, respectively. The setae along the ventral margin are longer than the diameter of the segment. Flagellum with 14 segments and the flagellar segments are not swollen, without flag-like setae. Calceoli is present on the 2nd–7th flagellar segments of antenna II.

The lower lip ( Figure 4) is without inner lobe and bears numerous small simple setae along the distal margins of both lobes.

Upper lip ( Figure 4) with numerous minute setules in the distal part.

Left mandible ( Figure 5) with 5-toothed incisor, lacinia mobilis with 4 dentitions, molar triturative. The first article of palp without setae, the second one with 14 setae. The third segment has 30 D-setae, 5 E-setae, two groups of A- and one group of B-setae. C-setae absent.

Right mandible ( Figure 5) has 3-toothed incisor and bifurcate lacinia mobilis.

Right maxilla I ( Figure 6) has 11 plumose setae along the inner margin of the inner lobe in addition to some tiny setules. The outer lobe bears 11 distal stout serrate spines and some tiny setules on the inner margin. Palp of the outer lobe with no seta in the first segment and four stout spines and two simple setae on the distal part of the second segment. The outer margin has no seta. The second article of left palp bears 7 spines and three simple setae on its distal part and no seta along the outer margin.

Maxilla II ( Figure 7) has a diagonal row of 13 plumose setae in the inner plate and some long simple setae on the distal part of the outer lobe. There are also a few tiny hairs in the proximal part of the inner margin of the lobe.

Maxilliped ( Figure 7) has 3 tooth-like spines and a spine in the distal part and the distal corner of the inner plate, respectively. Additionally, there are 7 plumose setae along the inner margin of it. Outer plate armed with 7-8 serrate stout setae in the distal part and 16 spines along its inner margin.

Coxal plates bear numerous simple setae and it is one of the discriminating characteristics of Gammarus morcae n. sp. Coxal plate I ( Figure 3A) is rectangular and bears many setae (~30) on the outer surface of the anterior and ventral sides. Coxal plate II ( Figure 3F) is triangular; setation is similar to that of the coxal plate I; bears more setae (~50). Coxal plate III ( Figure 8A) is rectangular, and bears several setae (~50) on the outer surface; additionally, 2-3 setae occur on the inner surface. Coxal plate IV ( Figure 8B) is longer than its width (l/w ratio is about 1:0.8); has a slightly convex distal margin; covered with many setae (~90). Coxal plates V and VI ( Figures 9A and 9B) bilobate. Coxal plate V bears 5 setae on the anterior lobe and many setae (~14) on the posterior lobe. Coxal plate VI ( Figure 9B) with no seta on the anterior lobe and some setae (~14) on the posterior lobe. Coxal plate VII ( Figure 9C) bears 1 seta along the anterior margin and many setae (~14) on the posterior margin.

Gnathopod I ( Figure 3A) has 10-12 long simple setae along both margins of the basal segment; the length of the setae can be up to twice the diameter of the basis. In the posterodistal corners of the basis and ischium, a group of short setae exists. The posterior and distal margins of the merus bear many simple setae. Carpus triangular; anterior margin bears four groups of simple setae; posterior margin

ÖZBEK and AYDIN / Turk J Zool

with 5-6 groups of simple setae. Propodus pyriform, anterior margin with seven groups (3 and 4 groups on inner and outer surfaces, respectively) of simple setae; middistal spine is present; posterodistal corner armed with a strong spine in addition to some small spines. Dactylus reaches the posterodistal corner and bears a simple seta along the outer margin in addition to a small setule around the distal part of the inner margin.

Gnathopod II ( Figure 3F) bears 4 or 5 long setae along the anterior and posterior margins of the basis in addition to some (9-10) shorter simple setae; the length of the setae can be more than twice the length of the diameter of the segment. Ischium bears a group of short and simple setae at the posterodistal corner. Merus bears a group of simple setae along each margin in addition to many setae at the distal margin. Carpus triangular, three groups of setae present along the anterior margin; posterior margin with 9-10 groups of setae. Propodus armed with 8 groups of short setae along the anterior margin; posterior margin with many groups of setae; medial palmar spine present; posterodistal corner armed with a strong spine in addition to some small spines. Dactylus reaches the posterodistal corner and bears a simple seta along the outer margin in addition to a small setule around the distal part of the inner margin.

Pereopod III ( Figure 8A) bears two groups of long setae near the proximal part of the anterior margin in addition to 3-4 groups of short simple setae near the distal part; the longer setae are shorter than twice the length of the diameter of the basis; posterior margin more setose, bears 7-8 groups of setae; setae on the proximal part are longer than those on the proximal part; some of them can

ÖZBEK and AYDIN / Turk J Zool

be more than twice length of the diameter of the segment. Ischium bears a group of short setae at the posterodistal corner. Merus and carpus bear short setae along their posterior margins. The anterior margin of the merus bears 4 groups of short setae while that of the carpus is bald. Propodus with three and five groups of short setae along the anterior and posterior margins, respectively. Dactylus bears a minute plumose seta along the outer margin in addition to two minute simple setae near the distal end of the inner margin.

Pereopod IV ( Figure 8B) bears 6-7 long and 5-6 short setae along the proximal and distal part of the anterior margin, respectively; setae can be longer than 1.5 times the length of the diameter of the segment; posterior margin more setose, bears 10-11 groups of long setae; some of them can be more than 1.5 times length of the diameter of the segment. Merus and carpus bear short setae along their posterior margins. The anterior margin of the merus bears 4 groups of armaments (each has a spine and a few short setae) while that of the carpus bears 3 groups of armaments. Propodus with five groups of short setae along the anterior and posterior margins. Dactylus bears a minute plumose seta along the outer margin in addition to one minute simple seta near the distal end of the inner margin.

Pereopod V ( Figure 9A) is slightly elongated. Basis has a setose posterior margin; setae present both on inner and outer margins; anterior margin with 7 groups of armament; length/width ratio of the basis is about 1.3. Ischium bears two groups of armaments along the anterior margin. Anterior margins of the merus and carpus without long setae; setae as long as or slightly longer than the accompanied spines. Merus has four groups of armaments along its anterior and posterior margins and the length/width ratio is about 4.0. Carpus bears 6-7 groups of armaments along both margins and the length/ width ratio of the segment is about 5.6. Propodus bears 7-8 groups of armaments along the anterior and posterior

ÖZBEK and AYDIN / Turk J Zool

margins and the length/width ratio of the segment is about 10.1. Dactylus bears a minute plumose seta along the outer margin in addition to two minute simple setae near the distal end of the inner margin.

Pereopod VI ( Figure 9B) is slightly elongated. Basis has a setose posterior margin; setae present both on inner and outer margins; anterior margin with 7 groups of armament; length/width ratio of the basis is about 1.6. Ischium bears one group of armament at the anterodistal corner. Anterior margins of the merus and carpus without long setae; setae as long as or shorter than the accompanied spines. Merus has 4-5 groups of armaments along its anterior and posterior margins and the length/width ratio is about 4.1. Carpus bears 5-6 groups of armaments along both margins and the length/width ratio of the segment is about 6.9. Propodus bears 7-8 groups of armaments along the anterior and posterior margins and the length/ width ratio of the segment is about 9.4. Dactylus bears a

ÖZBEK and AYDIN / Turk J Zool

minute plumose seta along the outer margin in addition to two minute simple setae near the distal end of the inner margin.

Pereopod VII ( Figure 9C) is slightly elongated. Basis has a setose posterior margin; setae present both on inner and outer margins; anterior margin with 6 groups of armament; a spine and a few accompanied short setae exist at the posterodistal corner of the inner surface; length/width ratio of the basis is about 1.7. Ischium bears one group of armament along the anterior margin. Anterior margins of the merus and carpus without long setae; setae as long as or shorter than the accompanied spines. Merus has four groups of armaments along its anterior and posterior margins and the length/width ratio is about 4.0. Carpus bears 6-7 groups of armaments along both margins and the length/width ratio of the segment is about 5.6. Propodus bears 6-8 groups of armaments along the anterior and posterior margins and the length/ width ratio of the segment is about 7.5. Dactylus bears a minute plumose seta along the outer margin in addition to two minute simple setae near the distal end of the inner margin.

Epimeral plates ( Figure 10) are not pointed. Epimeral plate I ( Figure 10A) bears a spine along the ventral margin and many (~25) setae along the posterior margin. Epimeral plate II ( Figure 10B) is more setose than Ep I, armed with three spines and 8-10 setae along the ventral margin; the posterior margin bears many (~16) setae. Epimeral plate III ( Figure 10C) has a similar setation to Ep II.

Pleopods ( Figure 10) Peduncle segments of pleopods bear many groups of simple setae in addition to 2 retinacula and 3-4 accompanied setae. Rami with 18-22 segments and bear numerous plumose setae.

Uropod I ( Figure 3D) has a longer peduncle than rami. Peduncle with a spine in proximal part in addition to 3 spines along the inner and outer margins and 3 spines in distal part. Both rami are about the same length. The inner ramus bears two spines along the inner margin, the outer margin bare. The outer ramus bears two groups of spines (2 × 2) along the inner margin and no spine on the outer side. Both rami bear 4-5 spines in their distal tips.

Uropod II ( Figure 3E) is much smaller than the first one (about 0.57:1). Peduncle longer than the rami and bears 2 spines along the inner margin, outer margin bare. The inner ramus is slightly longer than the outer one (1.3:1). The length and armaments of both rami look similar to each other, they bear three spines along their inner margins in addition to 4-5 longer spines on their distal tips.

Uropod III ( Figure 8D) peduncle bears 2 groups of spine and setae combination in the proximal part and 2 groups of spines in the distal part. Inner ramus slightly shorter than the outer one (~0.8:1); inner and outer margins with plumose setae; 6 and 2-3 spines present along the outer margin and distal end, respectively. The outer ramus has 6 groups of spines (1-1-2-2-2-1) together with 7-8 simple setae accompanied to each group along the outer margin; setae are longer than the spines. Article 2 of the outer ramus is shorter than the surrounding spines and has a few simple setae on the distal tip.

Telson ( Figure 8C) cleft and slightly elongated, each lobe bears 3-4 spines and 2 simple setae in the distal part. The setae are as long as the spines. The length/width ratio of the lobes is about 1:0.9.

Description of the allotype female:

Body length 15.2 mm; sexual dimorphism present ( Figure 11). Body more setose than male; head with many setae; antenna I is more setose and bears 37 and 4 flagellar segments in the main and accessory flagellum, respectively; antenna II bears longer setae on the peduncular segments, 13 flagellar segments present, calceoli absent; coxal plates bear more and longer setae; gnathopod I and II smaller than those of male; pereopods III to VII, epimeral plates and uropods are similar to male in terms of setation and armaments; dactylus more slender; armaments of urosomites are similar to that of male; telson with 3-4

ÖZBEK and AYDIN / Turk J Zool

apical spines together with a few simple setae per lobe. Oostegites are relatively narrow, without marginal setae, and present on gnathopod II to pereopod V.

Variability: Numbers of the flagellar segments of antenna I and II are variable (AI: 36-45; AII: 13-17). Calceoli can be present or absent on the flagellar segments of the males. Number of the setae on the coxal and epimeral plates can be variable.