Alonella hampelae, Alonso, Miguel & Kotov, Alexey, 2017

Alonso, Miguel & Kotov, Alexey, 2017, A new species of Alonella Sars, 1862 (Crustacea: Cladocera: Chydoridae) from the Ecuadorian Andes, Zootaxa 4290 (3), pp. 581-590 : 583-587

Alonella hampelae sp. nov.

( Figs. 1–3 )

Etymology. This taxon is named after Prof. Dr. Henrietta Hampel (University of Cuenca, Ecuador), in recognition of her enthusiastic promotion of Limnology in Ecuador creating the Laboratory of Hydrobiology at the Department of Water Resources and Environmental Sciences of Cuenca University.

Type locality. Juan Manuel Pool near Osohuaico lake in the Cajas National Park , Azuay Province, Andes Australes, Ecuador. Coordinates: 2°50’12.024’’S, 79°12’37.171’’W. Altitude: 3775 m a.s.l.

Type material. Holotype: undissected adult parthenogenetic female in a tube with 4% formalin deposited at the Museo Ecuatoriano de Ciencias Naturales del Instituto Nacional de Biodiversidad, Quito, Ecuador. Accession number MECN-SI-Cal-0 0 0 5 . Holotype label: “ Alonella hampelae 1 parth. ♀ Charco Juan Manuel 2 anex. Osohuayco, CJ-196 Cajas National Park. Azuay, Ecuador ”. Coll. Henrietta Hampel, April 2015.

Paratypes: Ten adult parthenogenetic females from type locality. Coll. Henrietta Hampel, April 2015. Accession number MECN-SI-Cal-0005.

Other material examined. All in the collection of the Laboratory of Hydrobiology of the Department of Water Resources and Environmental Sciences of the Cuenca University ( Ecuador). All localities from Cajas National Park: Patococha 1 lake, code QN L135 (2°48’34.23’’S, 79°10’27.50’’W, 3841 m a.s.l.), February 2015 ; Temporary pool Charca Anostráceos , code LU L159 (2°47’2.92’’S, 79°14’51.94’’W, 4131 m a.s.l.) Mars, 2015; Mangacocha 1 lake, code SU L170 (2°49’52.99’’S, 79°16’16.09’’W, 4009 m a.s.l.) March 2015 ; Pool 1 annexed to Ingacocha 1 lake, code SU L175 (2°51’19.64”S, 79°16’32.67’W, 4046 m a.s.l.) Mars , 2015; Shallow lake 2, annexed to Ingacasa lake , code SO L176 (2°51’15.59’’S, 79°16’41.52’’W, 3971 m a.s.l.) April , 2015; Pool annexed to Culebrillas lake , code SO L192 (2°49’50.55’’S, 79°16’38.90’’W, 3953 m a.s.l.) April , 2015; Juan Manuel pool annexed to Osohuaico lake, code LIA L196 (2°50’12.024’’S, 79°12’37.171’’W, 3775 m a.s.l.), May 2015 ; Atucpamba 2 shallow lake, code AT L200 (2°51’55.38’’S, 79°18’38.54’’W, 4156 m a.s.l.), May, 2015;

Diagnosis. Parthenogenetic female. Body light brown, subovoid, elongated for the genus; posterodorsal angle well defined; posteroventral angle evenly rounded, lacking any denticles. Ventral margin of carapace armed with marginal setae differentiated into three groups; setae of posterior group longest. Surface of valves with broad flattened crests parallel to anterior margin in anterior half, oblique in posterior half; fine striae within cells forming by crests. Rostrum elongated, pointing somewhat inwards. Compound eye and ocellus of similar size. Head shield rhomboidal, maximum width behind level of mandibular articulation, provided with fine longitudinal anastomosing striae; its posterior part rounded; postpore distance (PP) about 0.7 interpore distance (IP); lateral head pores minute, located at headshield midline. Labral keel long, with convex anterior margin, tip projecting beyond tip of rostrum. Antenna II with third terminal seta of endopod relatively short, only five times longer than apical segment; spine on proximal segment of exopod small; apical spines of endopod and exopod long. Postabdomen moderately short, slightly tapering distally; preanal and postanal angles expressed; anal margin concave, as long as postanal margin; preanal margin longer than anal margin; dorsodistal angle rounded and slightly prominent distally; dorsal margin provided with teeth in postanal portion each tooth accompanied by single additional denticle; lateral row of 3 or 4 crescents of short setulae in postanal portion and lateral clusters of longer setulae in anal and preanal portions. Postabdominal claw shorter than anal margin, slightly curved, with two basal spines, proximal one three times shorter than distal one; length of distal one as diameter of claw at its base. Outer distal lobe (ODL) of limb 1 with a long terminal seta and a very short, naked lateral seta; inner distal lobe (IDL) with relatively short first seta, longer second seta and third seta intermediate in length between previous two setae, each with distal segment unilaterally armed with short setulae; setae 2 and 3 of the first and second endite respectively, long and slender. Scrapers of limb II of similar size and morphology; filter plate II with eight setae. Exopodite of limb III with seven setae, seta 4 longest; setae 6 and 7 of basal endite thick, bended, and armed with strong serration; filter plate III with eight setae. Exopodite IV with seven setae, filter plate IV with six setae. Exopodite V subovoid with four setae; gnathobase armed with single small element; filter plate V with three setae. Size up to 0.40 mm.

Description. Adult parthenogenetic female. Habitus ( Fig. 1 A). Body light brown. Length 0.34–0.40 mm; body height/length ratio about 0.63–0.68. In lateral view body subovoid, elongated for the genus, maximum height in the middle. Dorsal margin evenly arched from tip of rostrum to posterodorsal angle. Body compressed laterally. One or two eggs in brood pouch.

Carapace ( Fig. 1 B–C). Ventral margin with slight prominence in its middle, armed with 61–69 marginal setae each with fine setulae along posterior side. Marginal setae, differentiated into three groups; setae of anterior quarter long, those of second quarter shortest, those of posterior half again longer, setae in middle of this portion longest among all marginal setae. Postero-ventral angle evenly rounded. Posterior margin weakly convex. Row of minute submarginal setulae of uniform size starting at inner valve face posterior to last marginal seta and continuing towards postero-dorsal angle. Surface of carapace with a very particular reticulation consisting of broad flat crests parallel to anterior margin in anterior half part and oblique in posterior half. Fine striae within crests.

Head ( Fig. 1 A) triangle-rounded in lateral view. In lateral view, rostrum elongated pointing somewhat inwards. Compound eye and ocellus of similar size. Head shield ( Fig. 1 D, E) rhomboidal, maximum width behind level of mandibular articulation; very low projection posterior to latter; head shield length about 1.3 its width; ornamentation consisting of fine longitudinal anastomosing striae. Rostrum elongated, with a rounded tip. Posterior part of head shield as right angle with rounded vertex. Two major head pores of similar size, with a wide connection between them ( Fig. 1 E), PP about 0.7 IP in adults. Lateral head pores minute, located at headshield midline, somewhat closer to anterior major head pore.

Labrum ( Fig. 1 F). Labral keel long, with convex anterior margin, its tip projecting beyond tip of rostrum. Apex rounded, with faint notch in anterior margin.

Antennule ( Fig. 2 A). Approximately twice as long as wide. Antennular sensory seta slender, about 0.8 times length of antennule body and implanted in a third of antennular length from distal end. Nine aesthetascs of markedly different size, all shorter than antennular body, barely exceeding the tip of the rostrum.

Antenna II ( Fig. 2 B). Relatively short. Basal segment distally with marginal row of spinulae. Exopod little longer than endopod, all segments cylindrical. Setulation on all segments very scarce. Antennal formula: setae 0-0- 3/1-1-3 (exopod/endopod); spines 1-0-1/0-0-1. Setae on endopod: one on proximal segment not reaching end of apical spine; among three apical setae two long, as long as seta of middle segment, third seta short, only five times longer than apical segment. Exopod with three apical setae, as long as those of endopod. Spine on proximal segment of exopod small. Endopod and exopod apical spines long; former slightly longer than latter.

Postabdomen ( Fig 2 C) moderately short, slightly tapering distally. Preanal and postanal angles expressed; anal margin concave, as long as postanal margin; preanal margin longer than anal margin; dorso-distal angle rounded, slightly prominent distally. Dorsal margin provided with teeth organized in groups of 2–4 members in its proximal portion, postanal portion with single teeth, each accompanied by single accessory denticle. Lateral row of 3 or 4 crescents of short setulae in postanal portion and lateral clusters of longer setulae in anal and preanal portions. Postabdominal setae about half length of postabdomen; large and bilaterally armed with thin setulae in its distal half. Postabdominal claw shorter than anal margin, slightly curved, with continuous series of thin setulae along dorsal margin and two basal spines, proximal one three times shorter than distal one; length of distal one as diameter of postabdominal claw at its base. Three regularly spaced, transverse crescents of short setulae across ventral margin.

Limb 1 ( Fig. 3 A). Outer distal lobe (ODL) long, its terminal seta with distal segment bilaterally armed with minute setulae, its lateral seta very short, naked. Inner distal lobe (IDL) with relatively short first seta, longer second seta and third seta of intermediate length, all unilaterally armed with short setulae distally. Endite 3 with three thick posterior bilaterally setulated setae (a–c) and unilaterally setulated anterior seta 1; setae 1 and c being the longest. Endite 2 with a row of thick spinulae; three posterior setae (d–f) and thin naked anterior seta 2; first posterior seta being shortest, two others significantly longer; all unilaterally armed with strong setulae. Endite 1 with three long posterior setae (g, h, i) and anterior naked seta 3 significantly longer than seta 2; posterior setae bilaterally armed with short setulae distally. About seven or eight bunches of long thick setulae on ventral face of limb. Fascicles of thin setulae on inner face of limb. Two ejector hooks of subequal size.

Limb II ( Fig. 3 B). Exopodite small, with a single short, naked seta. Inner-distal limb portion with eight scrappers, setae 1–2 armed with fine setulae, other setae armed distally with thin spinulae. Setae 1 and 3 the longest; setae 2, 4 and 5 of intermediate size; setae 6–8 the shortest. Distal armature of gnathobase with bunch of thick setulae and four setae. Filter plate II with eight setae, two anteriormost members considerably shorter than others.

Limb III ( Figs 3 C–D). Exopodite ( Fig. 3 C) subrectangular, with four distal setae (1–4), three lateral setae (5– 7). Seta 4 longest, setae 1–2 of intermediate size, setae 3, 5, 6 and 7 shortest. Distal endite with three anterior setae (1–3); proximalmost seta 3 much shorter, apparently naked; geniculated sensillum near bases of setae 2 and 3. Basal endite with four anterior setae (4–7) increasing in size proximally; setae 4 and 5 naked; setae 6 and 7 thick, bended and armed with strong serration. Posterior surface with six soft bilaterally setulated setae (a–f). Gnathobase not clearly demarked from basal endite; distal armature with three setae, long bent sensillum invading basal endite, bunch of thick setulae. Filter plate III with eight setae, anterior one armed with thick setulae.

Limb IV ( Figs. 3 F–G). Exopodite wide, subovoid, with seven setae of unequal size. Inner-distal portion ( Fig. 3 G) with four marginal setae (1–4). Distalmost seta 1 stout, naked; setae 2–4 stout, with bent distal segments armed with thick setulae; sensillum located proximal to seta 4. On posterior surface, four soft plumose setae. Distal armature of gnathobase with three setae. Filter plate IV with six setae.

Limb V ( Fig. 3 H). Pre-epipodite rounded and setulated. Epipodite subovoid, with a finger-like projection. Exopodite large, subovoid, with single distal seta 1 and three lateral setae (2–4); two projections bearing long thick setulae distal to seta 1. Inner limb portion as elongated, flat lobe, with setulated inner margin, setae 1 and 2 located near bases of this lobe, both unilaterally armed with thick setulae; seta 1 slightly longer than seta 2. Gnathobase armed with single small setal remain. Three setae in filter comb.

Ephippial female, ephippium and male. Unknown. At this latitude seasonality is scarcely expressed, therefore the probability of finding gamogenetic specimens is very low.

Distribution and ecology. Alonella hampelae sp. nov. is so far known only from the Cajas National Park, in the Southern part of Ecuadorian Andes. It appears in small lagoons and temporary ponds, always associated with submerged macrophytes. Waters have significant amounts of DOC coming from the adjacent terrestrial ecosystems dominated by paramo grassland (pajonal). Water mineralization is very low (9.84–91.50 µS/cm).

Differential diagnosis. This species is unique among the species of Alonella having no denticle(s) at the postero-dorsal valve portion. The new species is most similar to A. excisa ( Fischer, 1854) , but differs from the latter in: (1) more elongated body (height/length = 0.63–0.68); (2) absence of any denticles at the postero-ventral valve portion; (3) evenly rounded postero-ventral valve portion instead of making a postero-ventral angle; (4) setules after (= posterior to) the last marginal seta similar in size with the following setules at the posterior margin; (5) head shield with more elongated rostrum and a very low projection posteriorly to the mandibular articulation; (6) smaller PP distance (about 0.7 IP distance); (7) less expressed dorso-distal angle of postabdomen; (8) each postanal tooth in middle portion of postanal margin with a single, small accompanying denticle; (9) anterior setae 6 and 7 on proximal endite of thoracic limb III specially thick and supplied with a specially strong serration.

Figures

FIGURE 1. Alonella hampelae sp. nov. from the CajaS National Park, Azuay Province, Ecuador. A – F, adult parthenogenetic female. A, habituS. B, left valve. C, poSteroventral angle of valve. D, head Shield. F, head poreS and poSterior margin of head Shield. G, labrum.

FIGURE 2. Alonella hampelae sp. nov. from the CajaS National Park, Azuay Province, Ecuador. A – C, adult parthenogenetic female. A, antennule. B, antenna II. C, poStabdomen.

FIGURE 3. Alonella hampelae sp. nov. from the CajaS National Park, Azuay Province, Ecuador. A – H, adult parthenogenetic female. A, limb I. B, limb II. C, exopodite of limb III. D – E, inner portion of limb III. F, exopodite of limb IV. G, inner portion of limb IV. H, limb V.