Alpinalona cajasi, Alonso & Sinev, 2017

Alonso, Miguel & Sinev, Artem Y., 2017, Relocation of Alona manueli Sinev & Zawisza 2013 and a new closely related species from the Ecuadorian Andes to the new genus Alpinalona (Cladocera, Chydoridae, Aloninae), Zootaxa 4350 (3), pp. 563-573 : 566-571

Alpinalona cajasi sp. nov.

( Figs. 1–3 )

Etymology. Species name refers to El Cajas National Park (Azuay Province; southern Ecuadorian Andes) where it has been found.

Type locality. Shallow lagoon annexed to Yantahuaico lake in the Cajas National Park, Azuay Province, Ecuador. Position: 250’7.428”S; 7920’31.696” W. Altitude: 4085 masl.

Type material. Holotype: parthenogenetic female from the type location, MECN SI-Cal-0007 coll. Henrietta Hampel, March 2015.

Paratypes: 10 parthenogenetic females, 4 gamogenetic females and 2 males from the type location, MECN SI-Cal-0007 coll. Henrietta Hampel, March 2015.

Comparative material examined: All in collection of Laboratory of Hydrobiology of the Departamento de Recursos Hídricos y Ciencias Ambientales de la Universidad de Cuenca ( Ecuador). All localities from El Cajas National Park: Charca Anostráceos, code LUL159 (247’2.92”S, 7914’51.94”W, 4131 masl) March, 2015; Anexo Estrella 1, code CAL139 (251’5.88”S, 7920’19.72”W, 4125 masl) March, 2015; Anexa Culebrillas, code SUL190 (249’42.52”S, 7916’46.25”W, 3971 masl) April, 2015.

Diagnosis. Parthenogenetic female. Body sub ovoid, of moderate height, maximum height at middle of body. Dorsal margin uniformly curved; postero-dorsal angle prominent; postero-ventral angle broadly rounded and provided with about 20 short setulae organized in groups, without denticles. Body moderately compressed laterally. Ventral margin with about 50–60 setae. Head shield with broadly rounded posterior angle; rostrum short, broadly rounded. Two major head pores with narrow connection between them, PP about 2 IP. Lateral head pores minute, located at about same IP distance from midline, at level between major head pores. Labrum of moderate size; labral keel moderately wide, with convex anterior margin and rounded or blunt apex; anterior margin of keel convex, posterior margin without any setulae. Postabdomen moderately short and broad, subrectangular, maximum height at the middle of postanal margin. Length about 2.3–2.4 height. Ventral margin straight. Dorso-distal margin broadly rounded. Dorsal margin convex in postanal part and concave in anal part; preanal, anal and postanal margins of similar length. Preanal angle well-defined, postanal angle not defined. Preanal margin almost straight. 7–8 short postanal marginal groups of 3–5 denticles, each group formed by one bigger distal denticle followed by others decreasing in size proximally; 3–5 groups of marginal thin denticles on anal margin. 12–14 well-developed lateral fascicles of setulae; posteriormost setae of postanal fascicles very thick and long, about 1.5–2 width of postabdominal claw base. Distal postanal fascicles narrow, consisting of 4–6 setulae only, other more proximal fascicles of moderate width. Postabdominal claw weakly curved, slender, as long as preanal margin of postabdomen. Basal spine moderately short, thin, about 0.2 length of claw itself. Antennule long and narrow; antennular sensory seta 1.7 times shorter than antennule. Antennal formula, setae 0–0–3/1–1–3, spines 1–0–1/0–0– 1. Seta arising from basal segment of endopodite slightly shorter than endopodite. Spine on basal segment of exopodite shorter than middle segment. Apical spine of exopodite longer than apical segment; apical spine of endopodite equal or little shorter than apical segment. Thoracic limbs as for genus.

Male. Body low oval, height/length ratio about 0.53. Dorsal margin straight; posterodorsal angle prominent. Postabdomen similar in shape to that of female, but more narrow. Gonopores located at some distance from end of postabdomen. Ventral margin straight, with defined step at location of gonopores. Distal margin convex, distal angle broadly rounded. Preanal angle well-defined, postanal angle not defined. Distal part of postabdomen nearly as long than preanal, anal and postanal portions of similar length. Wide clusters of short thin spinulae in place of marginal denticles. Lateral fascicles of setulae same as in female. Postabdominal claw short, shorter than preanal portion of postabdomen; basal spine straight, about 0.17 claw length. Antennule without lateral aethetascs. Male seta arising at 1/4 antennule length from tip, about 0.5 antennule length. Limb I with U-shaped copulatory hook, its distal portion 1.5 times longer than basal one. A row of moderately long setulae located under copulatory brush on ventral face of limb. IDL without seta 1; setae 2 and 3 of similar length, much thinner and shorter than in female, male seta large, hook-like, almost as long as seta 3.

Description. Parthenogenetic female. Habitus. In lateral view body moderately high ( Fig. 1A ), maximum height at middle of body, height-to-length ratio 0.57–0.68 in adults; juvenile females with lower body than adult females. Body moderately compressed laterally. Dorsal margin uniformly curved; postero-dorsal angle characteristically protruding; postero-ventral angle broadly rounded; posterior margin weakly curved; ventral margin almost straight; antero-ventral angle rounded. Valves with well-developed linear sculpture. Ventral margin of valves ( Fig. 1B ) with 50–60 setae, about 15 anterior setae long, next 12–15 setae very short, followed by setae something shorter than the anterior ones, evenly decreasing in length posteriorly. Postero-ventral angle ( Fig. 1C ) bears about 20 short setulae of unequal length, organized into 2–3 groups. A row of about 200 setulae of unequal length, with very long setulae separated by shorter ones, along posterior margin on inner side of valve.

Head triangular-rounded in lateral view. In lateral view, rostrum short, pointing something forward. Ocellus and eye of similar size. Shape of head shield ( Fig. 1E ) as for genus, with maximum width behind the mandibular articulation; length about 1.4 width. Rostrum short, broadly rounded. Posterior part of head shield with broadly rounded distal angle. Two main head pores of similar size with narrow connection between them ( Fig. 1F ), PP about 2IP in adults. Lateral head pores minute, located at about same IP distance from midline, at level between main head pores.

Labrum ( Fig. 2G ) of moderate size; labral keel moderately wide, height-to-width ratio about 1.8, with rounded, blunt or slightly low-cut apex; anterior margin of keel convex, posterior margin without any setulae.

Thorax two times longer than abdomen. Middle abdominal segment not saddle-shaped, no abdominal joint.

Postabdomen ( Fig. 2A, B ) moderately short and broad, subrectangular, maximum height at the middle of postanal margin. Length about 2.3–2.4 height. Ventral margin straight. Dorso-distal margin broadly rounded. Dorsal margin convex in postanal part and concave in anal part; preanal, anal and postanal margins of similar length. Preanal angle well-defined, postanal angle not defined. Preanal margin almost straight. 7–8 short postanal marginal groups of 3–5 small denticles, each group formed by one bigger distal denticle followed by others decreasing in size proximally; 3–5 groups of marginal thin denticles on anal margin. 12–14 well-developed lateral fascicles of setulae; posteriormost setae of postanal fascicles very thick and long, about 1.5–2 width of postabdominal claw base. Distal postanal fascicles narrow, consisting of 4–6 setulae only, other more proximal fascicles of moderate width.

Postabdominal claw ( Fig. 2A ) weakly curved, slender, as long as preanal margin of postabdomen. Basal spine moderately short, thin, about 0.2 length of claw itself. Group of small spinulae located near the base of claw before basal spine.

Antennule ( Fig. 1H ) long and slender, length about 3 width, with four clusters of setulae on inner face. Antennular sensory seta slender, 1.7 times shorter than antennule, arising at 2/3 distance from the base. Nine aesthetascs of similar size, about half-length of antennule, projecting beyond anterior margin of the head shield.

Antenna ( Fig. 1I ) with antennal formula setae 0-0-3/1-1-3, spines 1-0-1/0-0-1. Basal segment massive, branches of moderate length, basalmost segments of both branches 1.5 times longer than others. Seta arising from basal segment of endopodite thin, surpassing tip of distal segment. Seta arising from middle segment of endopodite of similar size than apical setae. All apical setae of similar size and thickness. Spine on basal segment of exopodite slightly shorter than middle segment. Apical spine of exopodite longer than apical segment; apical spine of endopodite equal or little shorter than apical segment.

Thoracic limbs: five pairs.

Limb I ( Fig. 3A ) of moderate size. Epipodite oval, without projection. Accessory seta short, 4 times shorter than ODL seta. ODL seta with very short setulae in distal part. IDL with 3 setae, seta 1 sharp, about 1/6 length of ODL seta, setae 2 and 3 of moderate thickness, armed with thin setulae in distal part, seta 3 almost as long as ODL seta, seta 2 about 2/3 length of ODL seta. Endite 3 with four setae subequal in length. Endite 2 with three outer setae of different length, longest of them (e) longer than ODL seta and inner naked seta on anterior face. Endite 1 with two 2-segmented setae (g–h); a flat, geniculated seta (i) shifted to limb base, and inner naked setae on anterior face. Maxillar process long and narrow, with single setulated seta. Four–five rows of long setulae on ventral face of limb. Two ejector hooks, one of them slightly longer than other.

Inner portion of limb with eight scraping spines increasing progressively in length distally, armed with denticles of similar size. Distal armature of gnathobase with four elements. Filter plate II with seven setae, two posteriormost members considerably shorter than others.

Limb III. ( Figs. 3C–E ) Epipodite oval. Exopodite subquadrangular, with seven setae. Seta 3 longest; setae 6 about 0.45 length of seta 3; other setae short, more than two times shorter than seta 6. Setae 1–5 plumose, seta 6 armed bilaterally with hard setulae, seta 7 with short thin setulae at the middle. Distal endite with 3 setae and two small sensillae; two distalmost setae (1–2) scraping, slender, sharp, with denticles in distal part; basalmost seta (3) shorter, flattened, geniculated, bilaterally provided with setulae. Basal endite with 4 setae (a–d). Gnathobase with sensillum, small spine and a geniculated seta. Filter plate III with seven setae.

Limb IV ( Figs 3F–G ). Pre-epipodite setulated; epipodite with finger-like projection 1.5 times longer than epipodite itself. Exopodite subquadrangular, with six plumose setae. Setae 1–3 being longest; setae 2 slightly shorter than setae 1- 3; seta 5 about 2/3 length of seta 3; setae 4 and 6 about 1/2 length of seta 3; seta 4 shorter than seta 6. Inner portion with four setae and small bottle-shaped sensillum. Scraping seta slender, sharp, flaming-torch setae of similar shape, decreasing in size basally; small sensillum located between bases of setae 3 and 4. Three inner setae of similar length than filter plate setae. Gnathobase with long seta bent over endite, sensillum and small hillock distally. Filter plate IV with five setae.

Limb V ( Fig. 3H ). Preepipodite setulated, epipodite oval, with finger-like projection. Exopodite of moderate size, separated into two lobes, with four plumose setae evenly decreasing in length basally; seta 4 short, three times shorter than seta 1. Inner lobe moderately broad, widening distally. At inner face, two setae, distal seta 1.5 times longer than basal seta; large hillock and a small sensilla-like structure are located near its base. Filter plate V absent.

Ephippial female and ephippium. Ephippial female ( Fig. 2C ) of same size as parthenogenetic female. Dorsal margin more chitinized. Ephippium light brown.

Male. Body ( Fig. 2D ) lower than in female, height/length ratio about 0.53. Both eye and ocellus of size as in female.

Head similar to that of female. PP nearly IP distance.

Postabdomen ( Fig. 2E ) similar in shape to that of female, but more narrow, Length about 2.7 height. Gonopores located at some distance from the end of postabdomen. Ventral margin straight, with defined step at the location of gonopores. Distal angle broadly rounded. Preanal angle well-defined, postanal angle not defined. Distal part of postabdomen 1.6 times longer than preanal, anal portion slightly shorter than preanal portion. Clusters of short setulae in place of marginal denticles. Lateral fascicles of setulae same as in female.

Postabdominal claw short, shorter than preanal portion of postabdomen; basal spine straight, about 0.17 of claw length.

Antennule ( Fig. 2F ) short and moderately broad, length about two widths. 12 aesthetascs, of similar length, all of them terminal projecting beyond anterior margin of the head shield. Male seta about 1/3 of antennule length, arising at 1/4 length from tip.

Limb I ( Figs. 3I ) more massive than in female, copulatory hook U-shaped, its distal portion 1.5 times longer than basal one. A row of moderately long setulae located under copulatory brush on ventral face of limb. IDL without seta 1, setae 2 and 3 of similar length, much thinner and shorter than in female; male seta large, hook-like, almost as long as seta 3.

Size. In adult females length 0.48–0.58 mm, height 0.28–0.36 mm; length of adult males was 0.41–0.43 mm, height 0.22–0.23 mm.

Differential diagnosis. Alpinalona cajasi sp. nov. and A. manueli , the only two species in the genus, are quite similar. However, several features separate them easily, these are: (1) posterodorsal angle of carapace in A. cajasi sp. nov. shows a characteristic prominence formed by the dorsal union of the valves which extends backwards a little. This is a rare characteristic among Aloninae . In A manueli the porterodorsal angle of the carapace is broadly rounded; (2) female headshield is broader in A. cajasi sp. nov.; length/width about 1.4 in the new species and 1.6 in A. manueli ; (3) in females, PP distance in A. cajasi sp. nov. is about 2 IP whereas in A. manueli the PP distance is 0.8–1.2 IP; (4) in A. cajasi sp. nov marginal denticles of female postabdomen, mainly in postanal portion, organized in groups of 3–5 elements decreasing in size proximally whereas in A. manueli such denticles are single composite, nearly triangular, with 2–5 spinulae on posterior margin.

Distribution and ecology. Alpinalona cajasi n. sp. was, up to now, known only from the El Cajas National Park, in the Southern part of Ecuadorian Andes. It occurs both in the littoral of big lakes such as Patoquinuas and Sunincocha, and in small lagoons and temporary ponds, always associated with submerged macrophytes ( Myriophyllum quitense, Potamogeton paramoanus). Lakes are oligotrophic, although with significant amounts of DOC coming from adjacent lands dominated by paramo grassland (pajonal). Water mineralization is very low (9.84– 91.50 S /cm).

Figures

FIGURE 1. Alpinalona cajasi sp. nov. from the Cajas National Park, Azuay Province, Ecuador. A-I, adult parthenogenetic female. A, habitus. B, left valve. C, posteroventral angle of valve. D, marginal setae of anterior part of valve. E, head shield. F, head pores and posterior margin of head shield. G, labrum. H, antennule. I, left antenna.

FIGURE 2. Alpinalona cajasi 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, inner portion of limb IV. G, exopodite of limb IV. H, limb V. I, ventral margin, IDL and copulatory hook of limb I of adult male.

FIGURE 3. Alpinalona cajasi sp. nov. from the Cajas National Park, Azuay Province, Ecuador. A – B, adult parthenogenetic female postabdomen. C, ephippial female. D, adult male. E, adult male postabdomen. E, adult male antennule. Limb II triangle-rounded (Fig. 3 B). Exopodite elongated, of irregular shape, with short seta.