Eurycercus (Bullatifrons) meridionalis, Bekker & Kotov & Elmoor-Loureiro, 2010

Bekker, Eugeniya I., Kotov, Alexey A. & Elmoor-Loureiro, Lourdes M. A., 2010, The genus Eurycercus Baird, 1843 (Cladocera: Eurycercidae) in the Neotropics, Journal of Natural History 44 (41 - 42), pp. 2481-2508 : 2484-2495

publication ID	https://doi.org/ 10.1080/00222933.2010.488752
persistent identifier	https://treatment.plazi.org/id/03D887D2-EF05-8732-C904-FA27FC175DD3
treatment provided by	Felipe
scientific name	Eurycercus (Bullatifrons) meridionalis
status	sp. nov.

Treatment

Eurycercus (Bullatifrons) meridionalis View in CoL sp. nov.

( Figures 2–7 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7 )

Eurycercus lamellatus O. F. Müller View in CoL in Montú and Gloeden, 1986: 46, figs 13e–g.

Etymology

The species name is an adjective referring to its southern distribution. Type locality

Canal de Sarita , Estação Ecológica do Taim, Rio Grande do Sul, Brazil, coordinates: 32.6408° S, 52.62333° W. The type series was collected on 29 December 2001 by L.M.A. Elmoor-Loureiro GoogleMaps .

The Estação Ecológica do Taim is located within a larger area called the Taim Hydrological System, at the extreme south of Brazil (32°30′ to 32°40′S, 52°20′ to 52°40′ W). The reserve encompasses a variety of habitats such as beaches, dunes, forests, grasslands and, especially, lakes and wetlands. The complex of lakes and wetlands is locally known as “banhado”, where the emergent macrophytes could cover more than 30% of the area, with predominance of Scirpus californicus , Scirpus giganteus and Zizaniopsis bonariensis ; among the fluctuant macrophytes, Salvinia herzogii , Azolla caroliniana and Lemma valdiviana are the most frequent ( Paz 2003). The climate of the region is subtropical humid or type Cfa, according to the Köppen classification ( Waechter and Jarenkow 1998).

Type material

Holotype. Adult parthenogenetic female, mounted on a slide in PVL, MNRJ20411 View Materials .

Paratypes. Three females in alcohol, MNRJ20410 View Materials ; three females in alcohol, MCN2554 ; two adult parthenogenetic females, AAK M-0904; 11 dissected parthenogenetic females on slides EL00890-00900 and EL00904 .

Other material studied

Ten females from an artificial pond caused by sand mining at Parque Municipal do Iguaçu , Curitiba, Estado do Paraná, Brazil, collected on 12 May 2006 by G. P. Neves, AAK M-0905. Coordinates: 25°31′48″ S, 49°13′22″ W GoogleMaps .

The Parque Municipal do Iguaçu, located at the Metropolitan Region of Curitiba, has a complex of natural and artificial ponds, marginal to the upper Iguaçu River; large macrophyte stands, particularly of the genus Eichhornia and Pistia , occur at the edge of the ponds ( Abilhoa and Agostinho 2007). The specimens of E. meridionalis were sampled from an artificial pond, formed in a depression in the ground, caused by sand mining. For ponds of Parque Municipal do Iguaçu, Abilhoa and Agostinho (2007) reported pH between 6.8 and 7.8, and concentration of dissolved oxygen between 4.35 and 6.73 mg /l. The climate in both regions is also subtropical humid or type Cfa, according to the Köppen classification, with mean temperature between 10°C and 22°C ( Abilhoa and Agostinho 2007).

Diagnosis

Adult parthenogenetic female. Dorsal margin with a dorsal bubble bearing head pores. In anterior view, body wide, median dorsal keel absent. Rostrum short; posterior portion of head shield with a distinct straight section of the margin immediately anterior to the point of mandibular articulation; lateral pores elongated. Labral keel medium-sized, terminating in a broadly rounded apex. Postabdomen with a shallow distal anal embayment, with 102–122 preanal teeth. Teeth at base of preclaw portion short, predominantly clustered (doubled or tripled). Antenna I relatively short, but protruding greatly beyond tip of rostrum; antennular sensory seta arising somewhat basally to antenna I middle; denticles in rows encircling antennular surface specially small. IDL of limb I with three bisegmented setae, among them, a remarkable strong hook-like seta, but not as large as in E. macracanthus . IDL supplied with five to nine long distal spinules, six to ten long proximal spinules, four to seven very short marginal spinules and seven to nine short basal spinules. Limb II scraper 5 with 20–25 denticles, scraper 6 with 18–23 denticles, scraper 7 with 19–23 denticles; filter plate with eight setae. Nine setae in filter plate III; eight setae in filter plate IV, eight setae in filter plate V. Intestine with a single loop. Length up to 2.02 mm.

Description

Parthenogenetic female. In lateral view body subovoid in larger females ( Figures 2A,E View Figure 2 , 3A View Figure 3 ) and subrectangular in small females ( Figures 2F View Figure 2 , 3B View Figure 3 ), maximum height of the body in its middle portion (BH/BL = 0.53–0.68 in juveniles, 0.54–0.69 in largest adults). Dorsal margin evenly convex, interrupted only by a bubble-like head pore ( Figures 2B View Figure 2 , 3C View Figure 3 ). Posterodorsal angle expressed, more or less rounded in both adults and juveniles. Posterior margin slightly convex, smoothly rounded, posteroventral angle broadly rounded. In larger adults ventral margin with a slight prominence immediately anterior to the margin middle. In anterior view, body wide, not compressed laterally, maximum width of body at level of mandibular articulation. Median dorsal keel is absent. Parthenogenetic females carry few eggs in the brood pouch.

Head ( Figure 3C View Figure 3 ) large, with dorsal margin regularly arched from rostrum to region of dorsal head pores. Border line between head shield and valves obscure in preserved animals. Rostrum well expressed, short. Frontal head pore as transverse split, located somewhat anteriad to antennule bases on ventral surface of head ( Figure 2H,I View Figure 2 ). 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. Head shield little longer than wide (HW/ HL = 0.82–0.83 in juveniles, 0.76–0.91 in largest adults), with maximum height at level of mandibular articulation. Its anterior portion (= portion anterior to level of mandibular articulation) more than twice as large as posterior one ( Figure 3D View Figure 3 ), broadly rounded with slightly projected rostral region; posterior portion with a distinct straight section of the margin immediately anterior to the point of mandibular articulation ( Figure 3D View Figure 3 ). A single major “head pore” (dorsal organ) as a ringed, suboval field of special cuticle located on a dorsal bubble ( Figures 2B,C View Figure 2 ), MHP = 0.022 mm in juveniles, 0.022 –0.024 mm in largest adults. A minute, elongated ovoid lateral pore located at either side of major pore, closer to it ( Figures 2C View Figure 2 , 3E,F View Figure 3 ), distance between lateral head pores growing proportionally with growth of head shield (IP/HW = 0.06–0.08 in juveniles, 0.05–0.07 in largest adults). Head pores “projecting from the rounded head like a bubble with the median pore at the top” is a diagnostic trait of the subgenus Bullatifrons according to Frey (1975: 293).

Labrum as a fleshy body, with a medium-sized median keel, terminating in a broadly rounded apex, keel anterior margin slightly convex, without setulation, posterior margin almost straight. Distal labral plate with rich setulation ( Figure 3C View Figure 3 ).

margin of head, head pores and postabdomen; (E) adult; (F) juvenile; (G) instar variability of postabdomen general shape; (H) head, ventral view; (I) frontal head pore. Scale bars: 1 mm (A,E–G); 0.1 mm (B–D,H); 0.01 mm (I).

Paired lateral projections on labrum well-developed ( Figure 3G View Figure 3 ), horn-like, with apexes directed anterior. Distinct low fold surrounds base of labrum ( Figure 3C View Figure 3 ).

Valves generally ovoid (VL/BL = 0.75–0.85 in juveniles, 0.70–0.80 in largest adults), with very obscure, almost invisible under optical microscope reticulation. Anteroventral portion of valves slightly prominent anterior, with a special narrow flap ( Figure 3H–J View Figure 3 ). Continuous row of setae along ventral rim of valves, the anteriormost members short ( Figure 3A View Figure 3 ), setae then sharply increasing in size posterior to the prominence on ventral margin, and finally gradually decreasing in size to posteroventral valve portion. Posteroventral angle with a row of thin spinules, small denticles between them ( Figure 3K,L View Figure 3 ). This row continues to ventral portion of posterior margin ( Figure 3M,N View Figure 3 ), whereas dorsal portion of posterior margin armed with small, curved, densely located spinules lacking setules between them ( Figure 3O,P View Figure 3 ).

Thorax without external traces of segmentation, with six limb pairs. Abdomen thick, no abdominal projections on dorsal part of all segments ( Figures 2A View Figure 2 , 3B View Figure 3 ).

Postabdomen as a large (PL/TL = 0.33–0.40 in juveniles and the same in largest adults), broad ( PH /PL = 0.55–0.65 in juveniles, 0.51–0.57 in largest adults), flattened plate with subparallel dorsal and ventral margins ( Figures 2D View Figure 2 , 4A–C View Figure 4 ). Anus opens distally; hence the whole slightly convex dorsal margin represents the preanal margin of postabdomen. Dorsodistal (preanal) angle well expressed, distal anal embayment shallow, dorsal portion of distal (= anal) margin straight to slightly concave. Postanal angle obtuse, rounded ( Figures 4F–J View Figure 4 ). Preclaw portion of postabdomen, named as “distal expansion” by Hann (1990), as a conical prominence. Ventral margin of postabdomen slightly convex, a conspicuous, chitinized thickening of integument distally to claw base ( Figure 4G View Figure 4 ). Armature of the preanal margin as a series of preanal teeth (NT = 78–96 in juveniles, 102–122 in largest adults), slightly and gradually increasing in size in distal direction; a small gap lacking any teeth ( Figure 4D View Figure 4 ) at base of postabdominal setae; teeth in middle of preanal margin with sharp tips ( Figure 4E View Figure 4 ); distalmost tooth considerably larger than the others, located just on dorsodistal angle of postabdomen. On preclaw portion of postabdomen there are crescentic clusters of spines (homologues of lateral setae or postanal teeth of chydorids), distalmost members particularly large, predominantly clustered ( Figure 4I–K View Figure 4 ), teeth at base of preclaw portion short, also predominantly clustered (doubled or triplet). Subparallel rows of minute setules on whole lateral surface of postabdomen.

Postabdominal setae short (about half of preanal margin length), bisegmented, distal segment shorter than basal one and bilaterally setulated. Setae are located on a distinct, nut-like base.

Postabdominal claw relatively robust (CL/PL = 0.29–0.33 in juveniles, 0.26–0.29 in largest adults); with massive base; weakly and evenly tapered in distal direction, and slightly curved ( Figure 4F–H View Figure 4 ). Two pectens of denticles on outer surface of dorsal side of claws ( Figure 4H View Figure 4 ). Two basal spines, first (distal) long (DS/CL = 0.31–0.45 in juveniles, 0.31–0.37 in largest adults), second (basal) short (BS/CL = 0.15–0.21 in juveniles, 0.12–0.18 in largest adults; BS/DS = 0.32–0.52 in juveniles, 0.36–0.48 in largest adults), located dorsally immediately at base of claw.

Antenna I (antennule) relatively short (AL/BL = 0.10–0.11 in juveniles, 0.09–0.12 in largest adults; AL/DA = 2.7–3.0 in adults); with maximal width in basal half, with its distal two-thirds evenly tapering distally ( Figure 5A View Figure 5 ); protruding greatly beyond tip of rostrum ( Figure 3C View Figure 3 ). Slender antennular sensory seta long (about half antenna I length), arising somewhat basally to antenna I middle ( Figure 5A View Figure 5 ). Nine bisegmented aesthetascs, with pointed teeth around them. No setules at anterior margin of antenna I. Numerous short rows of minute denticles encircling antennular surface.

Antenna II relatively short. Several projections on its external surface in coxal region ( Figure 5B–D View Figure 5 ). On one of them with two bisegmented setae, unequal in length, next projection with semi-circular row of setules; distalmost projection inflated, 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, basalmost 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; in addition, distal segments with a third row of short, densely distributed setules ( Figure 5G View Figure 5 ). 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 subequal; length of spine situated on basal segment of exopod somewhat shorter than length of second segment ( Figure 5E,F View Figure 5 ).

Mandibles relatively elongated ( Figure 3A View Figure 3 ), articulated with integument between head shield and valves. Maxilla I with three densely setulated setae and a fourth short seta-like structure. Maxilla II absent in both adults and juveniles. It appears in embryos of Eurycercus lamellatus , but fully degenerates by the time of birth ( Kotov 1995, 1996).

Limb I large ( Figure 6A,B View Figure 6 ). Epipodite without a finger-like projection. Two accessory setae, unequal in size and setulated in distal parts, are the distalmost structures of the distal portion of limb I. ODL distally with two setae of very unequal size ( Figure 6C View Figure 6 ). IDL with three bisegmented setae, named as “clasping hooks” by Fryer (1963), and after him, Frey (1973) and Hann (1990) generally decreasing in size towards endites, among them, a remarkable strong hook-like seta. Also IDL supplied with four groups of spinules ( Figure 6D–G View Figure 6 ), named here after Hann (1982): long distal spinules (five or six in juveniles, five to nine in largest adults), long proximal spinules (four to six in juveniles, six to ten in largest adults), very short marginal spinules (four to six in juveniles, four to seven in largest adults) and short basal spinules (six to eight in juveniles, seven to nine in largest adults); a field of minute denticles on IDL basally, named as grinding tubercles by Frey (1975). Endite III with three setulated, bisegmented posterior setae of similar size ( Figure 6A View Figure 6 :a–c), and a setulated, stiff anterior seta 1 with a small, slender sensillum near its base. Endite II with three posterior setae ( Figure 6A View Figure 6 :d–f) analogous to those on eIII, and a stiff, setulated anterior seta 2, a very small sensillum near its base. Endite I with three posterior setae (g–i), and a stiff anterior seta 3. Two ejector hooks anteriorly on outer portion of limb corm ( Figure 6A,B View Figure 6 ). Well-developed maxillar process, earlier shown in embryos to be a remainder of gnathobase I ( Kotov 1995), 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 ( Figure 6H View Figure 6 ). At inner side of limb, a row of eight stiff scrapers; setae 1–3 with more delicate feathering, setae 4–8 with relatively robust denticles ( Figure 6I View Figure 6 ). Scraper 5 with 15–19 denticles in juveniles and 20–25 denticles in largest adult; scraper 6 with 15–17 denticles in juveniles and 18–23 denticles in largest adult; scraper 7 with 13–19 denticles in juveniles and 19–23 denticles in largest adult. Posteriorly on limb corm 8 soft setae: distalmost one ( Figure 6H View Figure 6 :a) short; next two ( Figure 6H View Figure 6 :b,c) longest, relatively stout, bilaterally armed in distal portions by short setules; basalmost ones ( Figure 6H View Figure 6 :d–h) similarly feathered by long hairs. Distal armature of gnathobase with four setae ( Figure 6J–K View Figure 6 ), one of them a minute sensillum (1), located far from the others, a row of denticles (four or five in juveniles, four to eight in largest adults) crossing near it. Filter plate with eight long, densely setulated setae; distalmost seta of filter plate clearly smaller than the others, second and third are slightly shorter than others. Additional bunch of setules basal to filter plate.

Limb III with relatively large epipodite lacking a finger-like projection ( Figure 7A View Figure 7 ). Exopodite flat, smaller than those of limbs IV and V. Distally, five setae of unequal size ( Figure 7A View Figure 7 :1–5), among them seta 3 with a special three-dimensional armature (supplied with two rows of strong setules and a row of delicate setules, Figure 7B View Figure 7 ); distal group consists of three setae (6–8), seta 8 especially long. Distal portion of inner limb part forms a partly isolated lobe, distal endite sensu Kotov (2000a, b), external endite sensu Dumont and Silva-Briano (1998) with three bisegmented anterior setae (1–3). Basal endite, internal endite sensu Dumont and Silva-Briano (1998) somewhat larger than distal endite. Marginally, a row of four stiff setae ( Figure 7C View Figure 7 :4–7), a small sensillum near seta 4. Seven long soft setae of subequal size ( Figure 7C View Figure 7 :a–h) on limb corm posteriorly. Gnathobase weakly demarcated from basal endite, distal armature with four members, one of them ( Figure 7C View Figure 7 :1) a large, bottle-shaped sensillum located far from the others. Nine setae in filter plate.

Limb IV with pre-epipodite as a setulated hillock; epipodite large, ovoid, without a finger-like projection ( Figure 7D View Figure 7 ). Exopodite oval, with two distal, relatively stout, bisegmented setae of unequal size, armed by short setules ( Figure 7D View Figure 7 :1,2), other six setae feathered bilaterally by very long hairs ( Figure 7D View Figure 7 :3–8). Marginally on inner limb face, a row of four stiff anterior setae ( Figure 7E View Figure 7 :1–4). Seta 1 shorter, setae 2–4 of equal size, feathered by long setules in distal part, small receptors near bases of setae 2 and 3. Posteriorly, five soft setae ( Figure 7D View Figure 7 :a–e) with subequal length. Distal armature of gnathobase with four members ( Figure 7E View Figure 7 :1–4). One of them a long, bisegmented seta, densely feathered in distal part ( Figure 7E View Figure 7 :2), two others small ( Figure 7E View Figure 7 :3,4), a large, bottleshaped sensillum ( Figure 7E View Figure 7 :1) is a fourth member of gnathobasic armature (similar to limb III). Filter plate IV with eight setae, middle ones longer than marginal ones.

Limb V with pre-epipodite as a setulated hillock; epipodite without a finger-like projection. Exopodite very large, with four short distal ( Figure 7F View Figure 7 :1–4) and three large lateral ( Figure 7F View Figure 7 :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 the basalmost seta. Gnathobase with one characteristic, bent hook, and a small denticle. Filter plate with eight setae ( Figure 7F View Figure 7 :a–g).

Limb VI triangular, with epipodite lacking a finger-like projection and a bunch of setules somewhat distal to it; its inner margin setulated ( Figure 7G View Figure 7 ).

Intestine has a single loop ( Figure 3B View Figure 3 ).

Ephippial female, male. Unknown.

Length

0.57–2.02 mm.

Differential diagnosis

See Table 1 and Discussion for differentiation of American species of Eurycercus (Bullatifrons) .

Distribution

The species is distributed in the South Atlantic and the Upper Río Paraná basins of Brazil (Estado do Paraná and Estado do Rio Grande do Sul) .