Alona altiplana, Kotov & Sinev & Berrios, 2010

Kotov, Alexey A., Sinev, Artem Y. & Berrios, Viviana Lorena, 2010, The Cladocera (Crustacea: Branchiopoda) of six high altitude water bodies in the North Chilean Andes, with discussion of Andean endemism 2430, Zootaxa 2430 (1), pp. 1-66 : 40-47

Alona altiplana sp. nov.

( Figures 19–22 )

Alona pulchella King in Megard 1967, p. 46, figs 29–32;

Alona pulchella var. cambouei Guerne & Richard in Dominguez 1973, p. 3 –7, figs 13–14.

Type locality. Crater Lake, Licancabur Volcano (locality 5).

Holotype. Adult parthenogenetic female in 90% alcohol, MGU Ml 95. Label of the holotype: " Alona altiplana sp. nov., 1 parth. ♀ from Crater Lake, Licancabur Volcano, Chile-Bolivia border, coll. in 04.ii.2007 by V. Gaete, HOLOTYPE ".

Paratypes. 20 parthenogenetic females, MGU Ml 96; 40 parthenogenetic females, AAK M-0410 .

Other material studied. 4 parthenogenetic females from locality 4; 13 parthenogenetic females from locality 3; 5 parthenogenetic females from locality 6.

Diagnosis. Parthenogenetic female. Body regular oval, of moderately high, in adults height/length ratio about 2/3, maximum height at the middle; body moderately compressed laterally. Dorsal margin convex, postero-dorsal and postero-ventral angles broadly rounded. Postero-dorsal angle with 35-50 setules not organised into groups. Ventral margin with about 35-45 setae. Head shield with broadly rounded posterior margin, rostrum short and rounded. Three major head pores with a narrow connection between them. PP less then 0.3 IP. Minute lateral head pores located about 1.2 IP distance from midline, at between anterior and middle major head pore. Labrum of moderate size, labral keel narrow, with convex anterior margin and a rounded apex. Postabdomen of moderate length and width, slightly narrowing distally, length about 2.5 height. Dorsal margin weakly convex in postanal portion, anal margin concave; distal part of postabdomen about 1.5 times longer than preanal one, postanal and anal margins approximately of similar length. Preanal angle well expressed, postanal angle not defined, distal margin straight, dorso-distal angle rounded. Postanal margin with 5–6 well-developed, sharp denticles, some of them with additional denticles near base; near them 5–7 broad lateral fascicles setules, the posteriormost seta of each fascicle longest, of same length as a marginal denticle. Postabdominal claw slightly longer than preanal portion of postabdomen. Basal spine straight or weakly curved, about 0.25 of the claw length. Antenna I of moderate size, with nine terminal aestetascs. Antennal formula: setae 0–0–3/1–1–3, spines 1–0–1/0–0–1. Seta arising from basal segment of endopod thin, as long as endopod. Spine on basal segment of exopod slightly shorter than middle segment. Spines on apical segments longer than apical segments. Limb I with accessory seta four times shorter than ODL seta. IDL with three setae, seta 1 well-developed, about 1/3 length of seta 3. Exopodite of limb III with seven setae, seta 5 being longest. Exopodite IV with six setae. Exopodite V with four setae, filter plate V absent. Epipodites IV and V without projections. Limb VI absent.

Small-sized species, length of adult 0.35–0.50 mm.

Description. Parthenogenetic female. In lateral view body regular oval, of moderate height, maximum height at middle of body ( Figs. 19A–E , 20A ), in adults height/length ratio about 2/3. Dorsal margin uniformly curved; postero-dorsal and postero-ventral angles broadly rounded; posterior margin uniformly curved; ventral margin almost straight; antero-ventral angle rounded. Body moderately compressed laterally ( Figs. 20B– D ).

Head of moderate size, triangle-round in lateral view, rostrum short, pointing downward ( Fig. 20E ). Eye larger than ocellus. Distance from tip of rostrum to ocellus in adults slightly greater than that between ocellus and eye, or equal to the latter. Head shield with maximum width behind mandibular articulation, without a reticulation or sculpture; rostrum short, broadly rounded; posterior margin of head shield broadly rounded ( Fig. 19F ). Three connected major head pores, connection between pores narrow; PP less than 0.3 IP ( Figs. 19G–H , 20F ). Lateral head pores minute, located about 1.2 IP distance from midline, at the level of middle major head pore. Labrum of moderate size; distal labral plate without setulation; labral keel narrow (heigh about than 2.5 width), with rounded apex; anterior margin of keel convex, posterior margin without any setules ( Fig. 19I ).

Valve ovoid, with obscure longitudinal lines, well-visible under SEM ( Figs. 20A–E, G ). Ventral with about 35-45 setae, first 7–11 setae long, next 10 setae short, other setae of moderate length ( Fig. 19J ). A row of about 100 setules along the posterior margin, this row located on inner side of valve, setules not organized into groups ( Figs. 19K–L ). Postero-dorsal angle bears 35–50 short setules of similar length, not organised in groups.

Thorax and abdomen subequal in length, dorsal surface of abdominal segments not saddle-shaped. No abdominal projections. Second abdominal segment with two transverse rows of long thin setules and groups of shorter setules ( Fig. 20H ). Postabdomen of moderate width, with almost parallel margins in postanal portion, straight distal margin and almost right dorso-distal angle, length about 2.5 height ( Figs 19M–O , 21A–C ). Ventral margin straight. Inflated basis of claws bordered from distal margin by clear incision. Dorsal margin with distal part 1.3–1.5 times longer than preanal one, with postanal and anal portions subequal in length. Postanal portion of distal margin straight, anal portion weakly concave. Preanal angle well-defined, postanal angle not defined. Preanal margin weakly convex to slightly sigmoid. Postabdomen with five-six well-developed marginal denticles, frequently with one-two additional minute spinules near base of each denticle, and with four-five groups of marginal setules on anal margin. Eight-eleven lateral fascicles of setules, six-seven distalmost fascicles large, with distalmost seta of each fascicle as long as marginal denticles. Additional row of three-five fascicles between lateral fascicles and marginal setules in preanal region. Postabdominal claw of moderate length, slightly longer than preanal portion of postabdomen. Basal spine about 0.25 of length of claw ( Figs 21B, D ).

Antenna I relatively short and wide, length about 2.5 widht, with two clusters of short setules at anterior face ( Figs 21E–F , 22A ). Antennular sensory seta slender, three times shorter than antenna I, arising at 2/3 distance from the base. Nine terminal aesthetascs, two longest of them about 1/2 length of antenna I. All aesthetascs projecting beyond anterior margin of head shield ( Fig. 21E ). Antenna II short and massive ( Figs 21E , 22B ). Antennal formula, setae 0–0–3/1–1–3, spines 1–0–1/0–0–1. Basal segment robust, branches short and broad, basal segments of both branches 1.5 times longer than others. One of terminal setae shorther than two others. Seta arising from basal segment of endopod of same length with endopod. Seta arising from middle segment of endopod of similar size with apical setae. Spine on basal segment of exopod shorter than middle segment. Apical spines longer than apical segments. Mandibles with asymmetrical molar surfaces as shown in Figs. 21G–H .

Five pairs of thoracic limbs.

Limb I ( Fig. 22C ), of moderate size; epipodite ovoid; accessory seta very short. ODL ( Fig. 22D ) with a long seta, armed with minute setules in distal part. IDL ( Fig. 22C ) with three setae and four-five clusters of small setules on ventral face, setae 2 and 3 2-segmented, shorter than ODL seta, both with thin setules in distal part, seta 1 of about 1/3 length of seta 1. Endite 3 with three posterior setae (a–c), and a shorter anterior seta 1. On endite 2 there posterior setae (d–f), setae e–f long, armed with robust setules in distal part, seta d similar to endite 3 setae a–c. Endite 1 with two 2-segmented setae g–h, both setulated in distal part, without a flat seta shifted to limb base. Six rows of thin long setules on ventral face of limb. Two ejector hooks, one of them somewhat larger than the other. Maxillar process with a short seta.

Limb II with exopodite elongated, supplied with a single naked seta of about 2/3 length of exopodite ( Fig. 22E ). Eight scraping setae (1–8), armed with spinules of similar shape, increasing in length distally. Distal armature of gnathobase with four elements. Filter plate with seven setae, the posteriormost three times shorter than others.

Limb III with oval epipodite; exopodite subrectangular, with seven setae ( Fig. 22F :1–7). Seta 5 being longest, seta 2 and 2/5 length of seta 5, other setae short. Seta 2 armed with stronger setules in distal part, seta 1 almost naked, all other setae plumose. Distal endite with three setae ( Fig. 22F : 1–3), two distalmost members slender, sharp, with distal parts unilaterally armed with sharp denticles; basalmost seta much shorter, bilaterally armed with long setules. Basal endite with four stiff setae, increasing in size toward the base ( Fig. 22G : 4–7), a small sensillum near the base of distalmost seta. Four soft setae increasing in size basally (a–d). Gnathobase not clearly separated from basal endite. Distal armature of gnathobase with four elements: an elongated, cylindrical sensillum; thin, bent seta; others two sharp spines. Filter plate III with seven setae.

Limb IV with oval epipodite, lacking a finger-like process; exopodite rounded, with six setae ( Fig. 22H : 1–6). Seta 4 longest, length of setae 1–3 evenly decreasing basally. Setae 3–6 plumose, seta 2 with short setules, seta 1 almost naked. Inner-distal portion of limb IV with four setae ( Fig. 22H : 1–4), seta 1 slender, sharp, three flaming-torch setae 2–4 of similar shape, armed with long setules, decreasing in size basally. Three soft setae increasing in size basally. Gnathobase with a small sensillum, a 2-segmented seta, and a small hillock distally. Filter plate with five setae.

Limb V with setulated pre-epipodite, epipodite oval, without a finger-like process. Exopodite oval, not divided into two lobes, with four plumose setae, decreasing in size basally ( Fig. 22I : 1–4), seta 1 four-three times shorter than seta 4. Inner limb portion an oval lobe, with setulated inner margin with two setae (1–2), 1 times longer than 2. Filter plate absent.

Ephippial female and male unknown.

Size. Parthenogenetic female 0.35–0.50 mm (height 0.24–0.30 mm), holotype 0.50 mm.

Differential diagnosis. Alona altiplana sp. nov. is a typical small-sized member of the Alona s. lat, it differs from most species of the same size by the characteristic morphology of postabdomen, which is moderately wide, with almost parallel margins and almost right distal angle, armed with well-developed marginal denticles and lateral setules. A. altiplana sp. nov. is similar in the general appearance and shape of postabdomen to a group of North American species - A. setulosa Megard, 1967 , A. borealis Chengalath & Hann, 1981 and A. lapidicola Chengalath & Hann, 1981 . A. altiplana sp. nov. differs from A. lapidicola in more narrow postabdomen with almost parallel margins, ocellus smaller than eye, and by absence of incisures on the posterior margin of the head shield. A. altiplana sp. nov. differs from A. borealis in short, broad rostrum and ocellus smaller than eye, from A. setulosa in un-interrupted connection between head pores and more narrow postabdomen with more developed marginal denticles.

Comments on taxonomic position. The closest relative of Alona altiplana sp. nov. is North American Alona setulosa , recently redescribed by Sinev (2009b). These two species have similar general habitus, morphology of postabdomen and all appendages. The most apparent difference between the species lies in the morphology of the head pores and armament of postabdomen (see above). Comparison of limb morphology reveals differences only in proportions of some setae of the level common for the closely related species of Alona s. lat., see Sinev (1999, 2001b, c), Van Damme and Dumont (2008a, b), etc. As pointed out by Sinev (2009b), Alona setulosa (and Alona altiplana as well) differs from the pulchella -group mainly in the morphology of postabdomen, which is long and narrow in all species of the group (see Sinev 2001b, c, 2002a, b). But the morphology of antenna I, antenna II, and thoracic limbs of these species is similar to that of pulchella - group. No detailed information about the appendages of A. borealis and A. lapidicopa is available, so relationships between these two species and Alona altiplan a sp. nov. are not clear.

Distribution. Alona altiplana sp. nov. is known from the lakes of North Chile and Bolivia; this species seems to be an endemic of the Andes .

Figures

FIGURE 19. Alona altiplana sp. nov., parthenogenetic female from Crater Lake, Licancabur Volcano, Chile-Bolivia border (A, L) and Salar de Lagunillas, Chile (B-K). A–B. Large adult; C. Juvenile of instar I; D. Juvenile II. E. Minimal size of reproduction; F. Head shield; G–H. Dorsal head pores; I. Labrum; J. Free margin of valve; K–L. Posterior margin. Scale bars 0.1 mm.

FIGURE 20. Alona altiplana sp. nov., parthenogenetic female from Crater Lake, Licancabur Volcano, Chile-Bolivia border. A–D. Large adult in lateral, ventral, anterior and dorsal view; E. Head; F. Dorsal head pores; G. Sculpture of valves; H. Abdomen. Scale bars 0.1 mm for A–E, 0.01 mm for F–H.

FIGURE 21. Alona altiplana sp. nov., parthenogenetic female from from Crater Lake, Licancabur Volcano, Chile- Bolivia border. A–C. Postabdomen; D. Postabdominal claw; E–F. Head; G–H. Molar surfaces of mandibles (right mandible on the right side of photo). Scale bars 0.01 mm.

FIGURE 22. Alona altiplana sp. nov., head and thoracic appendages of parthenogenetic female from Salar de Lagunillas, Chile. A. Antenna I; B. Antenna II; C. Limb I; D. Its outer distal lobe. E. Limb II; F–G. Limb III and basal endite of its inner-distal portion; H. Limb IV; I. Limb V. Scale bars 0.1 mm.