Eurycercus beringi, Bekker & Kotov & Taylor, 2012

Bekker, Eugeniya I., Kotov, Alexey A. & Taylor, Derek J., 2012, A revision of the subgenus Eurycercus (Eurycercus) Baird, 1843 emend. nov. (Cladocera: Eurycercidae) in the Holarctic with the description of a new species from Alaska, Zootaxa 3206 (1), pp. 1-40 : 28-32

Eurycercus beringi sp. nov.

Figs 10–11

Eurycercus sp. nov. in Bekker 2011, Table 1.

Etymology. The taxon is named in honor of Vitus Jonassen Bering (1681–1741), the leader of the First and the Second Russian Kamchatka Expeditions, who discovered the Bering Strait, Alaska, and the Aleutian and Commander Islands. Now this region is named “Beringia”.

Type locality. Council #05: a roadside pond <1.5 m deep, 10 X 25 m, Seward Peninsula , Alaska, U.S.A. Geographic coordinates: 64.8807 N 163.6872 W. The type series was collected in 05.08.2006 by D. J. Taylor ,

Holotype. A parthenogenetic female in 90%, MGU Ml 108. Label of the holotype: “ Eurycercus beringi sp. nov., 1 parthenogenetic female from Council #05: a roadside pond (64.88071ºN, 163.6872ºW), Seward Peninsula, Alaska, USA, coll. in 05.08.2005 by D. J. Taylor, HOLOTYPE ”.

Paratypes. Eight parthenogenetic females in in 90%, MGU Ml 109. Eight parthenogenetic females in in 90%, AAK M-1117. All paratypes are from the type locality.

Other material excluded from type series in Alaska, U.S.A.: Nome Road #06: Roadside pond <1 m deep, coll. in 06.08.2005 by D. J. Taylor, DJT (64.5603, -165,4870) ; Nome #07: A pond 80x 55 m, coll. in 05.08.2005 by D. J. Taylor, AAK M-1121 (64.5604, -165.4872) ; Nome #10: A pond 20x 30 m, coll. in 06.08.2005 by D. J. Taylor, AAK M-1120 (64.6226, -165.4111) ; Nome #11: Unnamed pond 8 X 5m, coll. in 06.08.2005 by D. J. Taylor, AAK M-1123 (64.5133, -165.4057) ; 2011_ Nome 03, coll. in 03.08.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (64.55368, -165.4499) ; 2011_ Nome 05, coll. in 03.08.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (64.56152, - 165.4899) ; 2011_ Nome 13, coll. in 03.08.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (64.51241, -165.4224) ; 2011_ Nome 15, coll. in 03.08.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (64.49419, -165.3753) ; 2011_ Nome 17, coll. in 03.08.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (64.49532, -165.3728) ; 2011_ Nome 18, coll. in 03.08.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (64.4891, -165.3326) ; Council Road #10: A tundra pond 21.54 X 17.58 m, coll. in 05.08.2005 by D. J. Taylor, AAK M-1118 (64.8681, -163.6927) ; Council #11: Large (65 X 54 m) tundra pond, coll. in 05.08.2005 by D. J. Taylor, AAK M-1119 (64.8742, -163.6947) ; 2011_ Council 07, coll. in 29-07-2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (64.87984, -163.6878) ; 2011_ Council 09, coll. in 29.07.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (64.87365, -163.692) ; 2011_ Council 11, coll. in 29.07.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (64.86829, -163.6937) ; 2011_ Council 17, coll. in 02.08.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (64.82822, -163.6795) ; 2011_ Council 18, coll. in 02.08.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (64.64355, -164.3562) ; 2011_ Council 25, coll. in 02.08.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (64.8777, - 163.6893) . Teller Road #07: Roadside pond <1m deep, coll. in 04.08.2005 by D. J. Taylor, AAK M-1116 (65.0475, -166.1840) ; 2011_ Teller 13, coll. in 28.07.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (64.56004, -165.4736) ; 2011_ Pilgrim Road 01, coll. in 27.07.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (65.08334, -164.9122) ; 2011_ Pilgrim 03, coll. in 27.07.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (65.08134, -164.891) ; 2011_ Pilgrim 04, coll. in 27.07.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (65.08067, - 164,8887) ; 2011_ Pilgrim 703, coll. in 04.08.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (65.08895, -164,9228) . 2011_ Glacial Lake 992, coll. in 01.08.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros (64.82653, -165.6725) .

Short diagnosis. Parthenogenetic female. Dorsal head pores on a bubble-like projection located on a transverse fold. In anterior view, body moderately compressed laterally, median dorsal keel present only in a posterior portion of the valves. Rostrum short. Ocellus small. Lateral head drop-shaped. Labrum with a large median keel, with angled apex, reaching distal end of antenna I length. Postabdomen subovoid, preanal teeth pointed. Spines at base of pre-claw portion predominantly doubled. Antenna I with antennular sensory seta arising in middle. Denticles in rows encircling antennular surface small. On antenna II, spine situated on proximal segment of exopod somewhat shorter than second segment. Limb I IDL with a strong hook-like seta, the smallest IDL seta short. IDL with about 9 distal spinules, about 14 proximal spinules, about 13 marginal spinules and about 17 basal spinules. Eight setae in filter plate II, 9 setae in filter plate III; 8 setae in filter plate IV, 8 setae in filter plate V.

Description. Parthenogenetic female. Body sub-ovoid in lateral view body ( Fig. 10A ), maximum height of the body in its middle portion (BH/BL= 0.66–0.71). Dorsal margin in general convex, but interrupted by a prominent transverse fold, bearing also a bubble-like projection with head pores. Postero-dorsal angle well expressed, posterior margin slightly convex, postero-ventral angle broadly rounded. In larger adults ventral margin with a slight prominence immediately anterior to the margin middle. In anterior or dorsal view, body somewhat compressed laterally ( Fig. 10B ), maximum width of body at level of mandibular articulation. Median dorsal keel present only in a posterior portion of the valves. Intestine has a single loop, posterior intestinal caecum present.

Head large, with dorsal margin regularly arched from rostrum to region of dorsal head pores ( Fig. 10C ). Bor- der line between head shield and valves obscure in preserved animals in lateral view, but quite distinct in dorsal view ( Fig. 10B ). Rostrum short. Compound eye rather large, located near dorsal margin of head markedly closer to rostral extremity than to head pores. Ocellus small, located at antennule base, closer to eye than to tip of rostrum. A single major “head pore” as a ringed, sub-oval field of special cuticle located on aforementioned dorsal bubble (as E. macracanthus ), oriented somewhat posterior, this bubble sites on a prominent transverse fold (as a E. lamellatus ) ( Fig. 10D–E ). Lateral pore minute, drop-shaped and located at either side of major pore, closer to it.

Labrum fleshy, with a large median keel ( Fig. 10F ), terminating in a well-developed apex, which seems to be angular (although not too strongly angular as in E. lamellatus ), keel anterior margin convex, without setulation, posterior margin almost straight. Distal labral plate with rich setulation. Paired lateral projections on labrum welldeveloped, horn-like, with apexes directed anterior ( Fig. 10G ).

Valves generally ovoid (VL/BL= 0.73–0.86), with very obscure reticulation. Antero-ventral portion of valves slightly prominent, with a special narrow flap ( Fig. 10H ). Continuous row of setae along ventral rim of valves, in anterior portion they are short ( Fig. 10I ), then sharply increasing in size posterior to the prominence on ventral margin ( Fig. 10J ), and finally gradually decreasing in size to postero-ventral valve portion. Postero-ventral angle with a row of spinules, with minute setules between them. This row continues to ventral portion of posterior margin ( Fig. 10K ).

Thorax, abdomen as in previous species.

Postabdomen as a large (PL/BL= 0.37–0.45), relatively broad ( PH /PL= 0.38–0.49), flattened plate ( Fig. 10M ). It is more ovoid, than in previous species, with dorsal and ventral margins coming together distally. Dorso-distal (preanal) angle well expressed, distal anal embayment deep, dorsal portion of distal (=anal) margin slightly concave. Postanal angle obtuse, rounded ( Fig. 10N ). Pre-claw portion of postabdomen as a conical prominence. Ventral margin of postabdomen slightly convex. Armature of the preanal margin as a series of preanal teeth, slightly and fluently increasing in size in distal direction; a gap lacking any teeth at base of postabdominal setae ( Fig. 10O ); teeth in middle of preanal margin with sharp tips (NT= 97); distal most tooth somewhat larger than the others, located just on dorso-distal angle of postabdomen. On pre-claw portion of postabdomen there are crescentic clusters postanal teeth, distalmost members particularly large, predominantly clustered, teeth at base of pre-claw portion short, predominantly doubled ( Fig. 10N , arrows). Sub-parallel rows of minute setules on whole lateral surface of postabdomen (not represented in Fig. 10M due to their minute size). Postabdominal setae short (less than third of preanal margin length), bisegmented, distal segment slightly shorter than basal one and bilaterally setulated. Setae located on a distinct, nut-like base. Postabdominal claw relatively robust (CL/PL= 0.13–0.25); with massive base; weakly and evenly tapered in distal direction, and slightly curved. Two basal spines, first (distal) long (DS/CL= 0.30–0.43), second (basal) short (BS/CL= 0.15–0.27; BS/DS= 0.34–0.60), located dorsally immediately at base of claw.

Antenna I relatively short (AL/BL = 0.1; AL/DA=2.85–3.94); with maximal width in basal half, with its distal 2/3 portion evenly tapering distally ( Fig. 11A ); protruding greatly beyond tip of rostrum ( Fig. 10C ). Slender antennular sensory seta relatively short (about third of antenna I length), arising approximately in antenna I middle. Nine bisegmented aesthetascs, with pointed teeth around them. Numerous short rows of minute denticles encircling antennular surface. Antenna II relatively short ( Fig. 11B ). In coxal region, a projection with two bisegmented setae, unequal in length, next projection with semi-circular row of setules and a distalmost projection with numerous strong spinules. Massive basal segment with a relatively long seta distally on anterior surface, and rows of short setules. Both branches with elongated segments, basal most members particularly elongated; all segments with rows of short setules. Setae 0-0-3/1-1-3; both apical and lateral setae long, clearly bisegmented, with long hairs on both basal and distal segments. Spines 1-0-1/0-0-1. No additional spines on distal parts of any segments of either branch. Length of apical spines and of segments from which they arise sub-equal; spine situated on proximal segment of exopod shorter than second segment.

Mandible ( Fig. 10L ), maxilla I, maxilla II as in previous species.

Limb I large. Epipodite (not represented in Fig. 11C ) without a finger-like projection. Two accessory setae, unequal in size and setulated in distal parts, are the distal most structures of the distal portion of limb I (also not represented in Fig. 11C ). ODL distally with 2 setae of very unequal size. IDL with three bisegmented setae, one of them a remarkable relatively strong hook-like seta (but less strong as E. macracanthus ), the smallest IDL seta short. IDL supplied with long distal spinules (about 9 in largest adults), long proximal spinules (about 14 in largest adults), short marginal spinules (about 13 in largest adults) and short basal spinules (about 17 in largest adults); a field of minute denticles on IDL basally. Endite III with three setulated, bisegmented posterior setae of similar size (a–c), and a setulated, stiff anterior seta 1. Endite II with three posterior setae (d–f) and a stiff, setulated anterior seta 2, a very small sensillum near its base. Endite I with 3 posterior setae (g–i), and a stiff anterior seta 3. Two ejector hooks anteriorly on outer portion of limb corm. Well-developed maxillar process bearing three slender, fully and densely setulated setae on inner side of limb base.

Limb II with ovoid epipodite lacking a finger-like projection; exopodite as a small lobe ( Fig. 11E ). At inner side of limb, a row of eight stiff scrapers; setae 1–2 with more delicate feathering, setae 3–8 with relatively robust denticle. Posteriorly on limb corm 8 soft setae: distal most one (a) short; next two ones (b–c) longest, basal most ones (d–h) similarly feathered by long hairs. Distal armature of gnathobase with four setae, one of them a relatively large sensillum ( Fig. 11F , 1 ), located far from the others, a row of denticles (about 10 in largest adults) crossing near it. Filter plate with 8 long, densely setulated setae; distal most seta of filter plate clearly smaller than the others, second-third ones slightly shorter than others.

Limb III with relatively large epipodite bearing a finger-like projection ( Fig. 11G ). Exopodite flat, distally, five setae of unequal size ( Fig. 11G , 1–5 ); lateral group consists of three setae (6–8) increasing in size basally. Distal endite with three bisegmented anterior setae (1–3), basal endite with 4 stiff setae (4–7). Seven long soft setae of subequal size (a–h) on limb corm posteriorly. Gnathobase weakly demarcated from basal endite, distal armature with 4 members as in previous species. Nine setae in filter plate.

Limb IV with epipodite large, ovoid, bearing a finger-like projection ( Fig. 11H ). Exopodite oval, with two distal, relatively long, bisegmented setae of unequal size, armed by short setules (1–2), other six setae feathered bilaterally by very long setules (3–8). Marginally on inner limb face, a row of four stiff anterior setae (1–4). Seta 1 long, setae 2–4 approximately of equal size, feathered by long setules in distal part. Posteriorly, five soft setae with subequal length. Distal armature of gnathobase with 4 members ( Fig. 11I , 1–4 ). One of them a long, bisegmented seta, densely feathered in distal part (2), two others small (3–4), a large, bottle-shaped sensillum (1) is a fourth member of gnathobasic armature (similar to limb III). Filter plate IV with 8 setae, middle ones longer than marginal ones.

Limb V with pre-epipodite as a setulated hillock; epipodite with a finger-like projection ( Fig. 11J ). Exopodite very large, with four short distal (1–4) and three large lateral (5–7) setae. Inner portion of limb with a protruding flap-like distal projection, fringed by long setules. Three marginal setae on inner face of limb, distal member slightly protruding behind distal endopodite projection, a sensillum near basalmost seta. Distal armature of gnathobase with three members ( Fig. 11K ). Filter plate with 8 setae.

Limb VI triangular-shaped, with epipodite bearing a long finger-like projection and a row of setules somewhat distal to it; its inner margin setulated ( Fig. 11L ).

Ephippial female, male. Unknown

Length. Parthenogenetic females 0.77–2.66 mm, holotype 2.04 mm.

Comments. This is the most specific taxon of the subgenus, combining characters of Frey’s subgenera E. ( Eurycercus ) and E. (Bullatifrons). It means that previously it could be misidentified as E. lamellatus or E. longirostris - vernalis .

Distribution. E. beringi sp. nov. has been found definitively only on the Seward Peninsula in northwest Alaska. However, there are several records of “ E. lamellatus ” from arctic Alaska and southwest Alaska ( Frey 1971) that have the same medial antenna I seta position as E. beringi ( Reed 1962) . So there is a good chance that E. beringi is common and widespread in Alaska and perhaps even beyond this state.

Ecology. This species is very common and widespread on the Seward Peninsula in oxbow ponds, roadside ditch ponds, small tundra ponds and even among the emergent plants of a glacial lake (Salmon Lake). The species occurs in standing waters on mixed tundra-taiga and on tundra. E. beringi sp. nov. was missing however from the high conductivity ponds near the Pilgrim hotsprings and near the Safety Sound. E. beringi sp. nov. sometimes cooccurs with the less common E. glacialis . It also occurs when different predators of cladocerans are abundant (fish in Salmon Lake; Chaoborus and Heterocope in ponds).

Figures

FIGURE 1. Distribution of species from the subgenus Eurycercus (Eurycercus) emend. nov. in the Holarctic according to our original samples—no literature data included. E. lamellatus—grey circles. E. macracanthus—black circles. E. pompholygodes—solid quadrates (red in electronic version). E. microdontus—black stars. E. longirostris—grey quadrates. E. nipponica—solid triangles (green in electronic version). E. beringi sp. nov.—black crosses.

FIGURE 10. Eurycercus beringi sp.nov., parthenogenetic female from Council #05: a roadside pond <1.5 m deep, 10 X 25 m, Seward Peninsula, Alaska, U.S.A. A, lateral view. B, dorsal view. C, head. D–E, head pores, lateral and dorsal view. F–G, labrum, lateral and ventral view. H, valve. I, setae at antero-ventral valve portion. J, setae at postero-ventral valve portion. K, armature of valve posterior margin. L, mandible. M, postabdomen. N, its distal portion. O, its basal portion. Scale bar denotes 1 mm (A–C, H, L–M); 0.1 mm (D–G, I–K, N–O).

FIGURE 11. Eurycercus beringi sp.nov., head and thoracic appendages of parthenogenetic female from Council #05: a roadside pond <1.5 m deep, 10 X 25 m, Seward Peninsula, Alaska, U.S.A. A, antenna I. B, antenna II. C, limb I. D, inner distal lobe of limb I. E, limb II. F, distal armature of its gnathobase. G, limb III. H, limb IV. I, distal armature of its gnathobase. J, limb V. K, distal armature of its gnathobase. K, limb VI. Scale bar denotes 0.1 mm.