Alpinalona, 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 : 564-566

Alpinalona gen. nov.

Type species. Alpinalona manueli ( Sinev & Zawisza, 2013) = Alona manueli Sinev & Zawisza, 2013

Etymology. From “alpina, –Latin –for alpine and – alona , referring to its habitat related to high mountains: Andes and the Neovolcanic Mexican Axis.

Description. Parthenogenetic female. In lateral view body oval moderately high, maximum height at middle of body. Body moderately compressed laterally. Dorsal margin uniformly curved; 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 with 40–60 setae, about 10–12 anterior setae long, next 5–7 setae very short, followed by setae of moderate length. Postero-ventral angle bears about 20 short setulae of unequal length, organized into 2–3 groups.

Head trianglur-rounded in lateral view. In lateral view, rostrum short. Ocellus and eye of similar size. Head shield with maximum width behind the mandibular articulation. 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. Lateral head pores minute. Labrum of moderate size; labral keel moderately wide; 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 moderately short and broad, subrectangular, maximum height at the middle of postanal margin. Length 2.3–2.5 height. Ventral margin straight. Distal margin conveх, distal angle broadly rounded. Dorsal margin convex in postanal part and concave in anal part. Preanal angle well-defined, postanal angle not defined. Preanal margin almost straight. Postabdomen provided with short postanal marginal denticles, and with 3 or 4 groups of marginal setulae 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. Postabdominal claw weakly curved, slender. Basal spine moderately short, thin, about 0.2 length of claw itself.

Antennule long and slender, length about 3 width. Antennular sensory seta slender, arising at 2/3 distance from the base. Nine aesthetascs of similar size.

Antenna 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, reaching tip of distal segment. Seta arising from middle segment of endopodite of similar size with apical setae. Apical setae of similar size and thickness. Spine on basal segment of exopodite slightly shorter than middle segment. Apical spines long.

Thoracic limbs: five pairs.

Limb I of moderate size. Epipodite oval, without projection. Accessory seta short. ODL seta with very short setulae in distal part. IDL with 3 setae, seta 1 sharp, short, setae 2 and 3 of moderate thickness, armed with thin setulae in distal part. Endite 3 with four setae subequal in length. On endite 2 there are three outer setae of different length and inner naked seta on anterior face. Endite 1 with two 2-segmented setae (g–h), a flat, geniculated seta (i) shifted to the limb base, and inner naked setae on anterior face. Four-five rows of long setulae on ventral face of limb.

Limb II triangle-rounded. Exopodite elongated, with short seta. Inner portion of limb with eight scraping spines increasing progressively in length distally, armed with denticles of similar size. No inner setae near base of scraper 1. Distal armature of gnathobase with four elements. Filter plate II with seven setae, two posteriormost members considerably shorter than others.

Limb III. Epipodite oval. Exopodite subquadrangular, with seven setae. Seta 3 longest, setae 6 about 1/3 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, two distalmost setae scraping, slender, sharp, with denticles in distal part; basalmost seta (3) shorter, flattened, geniculated, bilaterally provided with setulae. Filter plate III with seven setae.

Limb IV. Epipodite with long finger-like projection. Exopodite subquadrangular, with six plumose setae. Seta 1-2-3 being longest; 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 of limb IV with four setae and sensillum. Scraping seta slender, sharp; flaming-torch setae of similar shape, decreasing in size basally. Three inner setae. Gnathobase with two-segmented seta, sensillum and a small hillock distally. Filter plate IV with five setae.

Limb V. Epipodite with long finger-like projection. Exopodite of moderate size, bilobed, with four plumose setae. Inner lobe moderately broad, widening distally. At inner face, two setae, distal seta 1.5 times longer than basal seta. Filter plate V absent.

Male. Body low oval.

Postabdomen similar in shape to that of female, but more narrow, length about 3 maximum heights. Gonopores located at some distance from the end of postabdomen. Ventral margin straight, with defined step at the location of gonopores. Distal margin convex, distal angle broadly rounded. Preanal angle well-defined, postanal angle not defined. Anal and postanal portions of similar length. Wide clusters of short setulae or 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 0.17–0.25 of claw length.

Antennule with 12 terminal aesthetascs. Male seta thick, about 1/2–1/3 of antennule length.

Limb I with U-shaped copulatory hook, its distal portion 1.5 times longer than basal one. A row of 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.

Differential diagnosis. Outer morphology of the new genus is typical for Alona s. lato. Several features separate this new genus from other genera: (1) from Hexalona groups of Alona s. lato ( Flavalona , Prenda , guttata , affinis and intermedia groups) by absence of limb VI and filter plate V; (2) from Anthalona , Coronatella and elegans -group by seven setae on exopodite III, and by presence of well-developed seta 1 on IDL of limb III; (3) from Alona s. str. ( quadrangularis -group) and Ovalona , by two main head pores, lateral head pores located close to main pores, and by bilobed exopodite V; (4) from Ovalona by presence of seta i and inner setae 2–3 on limb I, and setae 4–5 of exopodite III being of same size; and (5) from Alona s. lato by weakly developed marginal denticles of postabdomen, clusters of thin setules on ventral surface of limb I, and by plumose setae 5–6 of exopodite IV.