Alona yara, Sinev, Artem Y. & Elmoor-Loureiro, Lourdes M. A., 2010

Sinev, Artem Y. & Elmoor-Loureiro, Lourdes M. A., 2010, Three new species of chydorid cladocerans of subfamily Aloninae (Branchipoda: Anomopoda: Chydoridae) from Brazil, Zootaxa 2390, pp. 1-25 : 10-17

Alona yara sp. n.

( Figs. 5–7 )

Etymology. Yara is a name of a figure from Brazilian mythology, based on ancient Tupi and Guaraní mythology, who is considered the lady or the mother of the freshwaters.

Type location. Sarita Channel, Taim Ecological Station, Rio Grande do Sul, Brazil (32° 37' 29" S, 52° 35' 48" W). The type series was collected on 29.xii.2001 by L.M.A. Elmoor-Loureiro.

Holotype. An adult parthenogenetic female, MZUSP 19925.The label of holotype is: " Alona yara sp. nov., 1 parth. Ƥ from Taim, RS, Brazil, HOLOTYPE ".

Paratypes. 1) two parthenogenetic females ( MZUSP 19926), two parthenogenetic females ( MNRJ 21588), two parthenogenetic females (EL00715), four parthenogenetic females (AYS- 2008-11) from the type locality; 3) about 15 parthenogenetic females and two males from Bonita Pond Downstream, Planaltina, Distrito Federal, Brazil (15° 35' 57.6'' S, 47° 41' 46.4'' W), coll. by F.D.R. Sousa, on 25.viii.2006, among decomposing tree leaves (EL01634, AYS- 2008-13); 4) seven parthenogenetic females from East Channel, Taim Ecological Station, Rio Grande do Sul, Brazil (32° 38' 39.5" S, 52° 35' 04.0" W), coll. By L.M.A. Elmoor-Loureiro, on 29.xii.2001 (slides EL01381 to EL01383, AYS- 2008-10). 5) about 10 parthenogenetic females from Pico Itapeva Reservoir, near Campos do Jordão, São Paulo, Brazil (22° 46' 25.2" S, 45° 33' 24.1" W), coll. by L.M.A. Elmoor-Loureiro, on 15.xi.2002 (EL00741, slides EL01384 to EL01387). 6) 13 parthenogenetic females from Sobradinho Stream, near its spring, Sobradinho, Distrito Federal, Brazil (15° 38' 28" S, 47° 45' 53" W), coll. By L.M.A. Elmoor-Loureiro, on 18.viii.2006 (EL01632, AYS-2008-07).

Diagnosis. Alona of moderate size, length up to 0.61 mm. Body oval, moderately high, compressed laterally. Carapace weakly widening posteriorly, maximum height in the third fourth of the body. Posterodorsal and posteroventral angles broadly rounded. Posterior margin convex. Posterodorsal angle with 7–9 groups of large setules. Ventral margin veakly convex, with 50–60 setae. Carapace sculpture as longitudinal lines and dense longitudinal striae.

Ocellus large, in some specimen as large as eye. Head shield as for genus, rostrum short and rounded, posterior margin as obtuse distal angle. Three major head pores with a narrow connection between them, PP about 0.8–0.95 IP. Lateral head pores minute, located at about 0.5–0.6 IP distance from midline. Labrum of moderate size, labral keel wide, height about 1.5 times width. Anterior margin of keel convex, with notch near the apex, apex blunt, rounded or rarely acute, posterior margin with two clusters of setae.

Postabdomen wide, of moderate length, maximum height in the middle of postanal portion. Length about 2.5–2.6 height. Ventral margin straight. Distal angle broadly rounded. Dorsal margin weakly convex in postanal portion and weakly concave in anal one, distal part about 2.5 times longer than preanal one, postanal portion 1.5 times longer than anal one. Preanal angle weakly defined, postanal angle not defined. Postanal margin with 10–12 well-developed, single sharp denticles, each several spinules along anterior margin. Postanal portion with 10–12 broad lateral fascicles, posteriormost setae of each fascicle longest, 1.5 times longer than neighboring marginal denticles. Postabdominal claw equal in length to preanal portion of postabdomen. Basal spine long and slender, about 1/3 of the claw length.

Antennule elongated, length about 3–3.5 width. Antennular seta arising at 2/3 distance from the base. Nine long terminal aesthetascs, two longest about 3/4 length of antennule itself.

Antenna with antennal formula, setae 0-0-3/1-1-3, spines 1-0-1/0-0-1. Seta arising from basal segment of endopodite thin, almost reaching end of endopodite. Spine on basal segment of exopodite significantly shorter slightly than middle segment. Spines on apical segments shorter than apical segments.

Five pairs of trunk limbs. Accessory seta of limb I almost as long as ODL seta. IDL of limb I with three setae, seta 1 well-developed, about 1/3 length of ODL seta. Ventral face of limb I with 12–14 long single setules. Exopodite II with long seta, scraping setae not differentiated. Exopodite III with seven setae. Epipodites IV–V without projections. Exopodite V large, elliptical. Filter plate V absent.

Male. In lateral view, oval, moderately high, maximum height in the third fourth of the body, height/ length ratio about 0.55. Dorsal margin of valves almost straight.

Postabdomen broad, massive, maximum height at postanal angle. Length about 2.7 height. Postabdominal claws situated on small protrusion in ventral portion of convex distal margin. The sperm ducts open above the protrusion, posteroventral and posterodorsal angles distinctly rounded. Preanal and postanal angles weakly defined. Clusters of thin setules in place of female marginal denticles. Lateral fascicles of setules same as in female. Postabdominal claw short, strongly curved. Basal spine long, about half length of claw itself.

Antennule with 12 long terminal aesthetascs, three longest about 3/4 length of antennule itself. Male seta located close to the end of antennule, about 1/3 length of antennule. Limb I with U-shaped copulatory hook. The IDL has four setae; IDL seta 1 strongly reduced, IDL setae 2 and 3 much short and thin, the male seta curved, as long as seta 2. The copulatory brush seta about 2/3 of IDl seta 2. Ventral face of the limb under the copulatory brush with two rows of 9–11 stiff setules.

Differential diagnosis. Alona yara belongs to the quadrangularis -group of Alona s. lato, recently defined as Alona s. str. by Van Damme & Dumont (2008), and had all characteristic features of this group, separating it from other Alona -like species. They include: broad postabdomen with convex postanal margin, armed with well-developed marginal denticles and lateral fascicles of setules, head shield with angular posterior margin and three main head pores, very large, single setules on ventral face of limb I, characteristic shapes of exopodites III–V, and others (for full list see Van Damme & Dumont 2008). A. yara differs from A. quadrangularis (O.F. Müller, 1776) and A. kolweizii Van Damme et Dumont, 2008 by the number of ventral setules on the ventral face of limb I, from A. boliviana Sinev et Coronel, 2006 by the shape of the body and postabdomen, narrow labral keel, absence of projections on epipodites IV–V. Other characters separating these species are summarized in Table 2 .

Description. Parthenogenetic female. In lateral view, body oval, moderately high, compressed laterally ( Fig. 4 A–D, 5A–B). Carapace weakly widening posteriorly, maximum height in the third fourth of the body. Height-length ratio 0.58–0.6 in both juvenile females and adults. Dorsal margin convex, posterodorsal and posteroventral angles broadly rounded. Posterior margin convex. Posteroventral angle with 7–9 groups of large setules, with 5–9 setules in each, length of setules in groups increase posteriorly ( Fig. 4 F, 5C). Ventral margin weakly convex, with 50–60 setae. Anterior 17–20 setae long, next 10 setae very short, setae in the middle of anterior margin almost as long as anterior setae, toward posterior margin, length of setae gradually decrease. Anteroventral angle rounded. Carapace sculpture ( Fig. 5 D–E) as about 20 longitudinal lines and dense longitudinal striae.

Head relatively small, triangle-round in lateral view. In lateral view rostrum protruding downwards. Ocellus large, in some specimen as large as eye. Distance from tip of rostrum to ocellus about 1.5 times of that between ocellus and eye.

Head shield ( Fig. 4 G) with maximum width behind mandibular articulation, covered by fine striae. Rostrum short and rounded. Posterior margin as obtuse distal angle. Three major head pores with a narrow connection between them ( Fig. 4 H–I, 5F–G). Central pore significantly smaller than two others. PP about 0.8– 0.95 IP in adults. Lateral head pores located in small depressions about 0.5–0.6 IP distance from midline, at level between anterior and central major head pore. Around head pores striae absent.

Labrum of moderate size, without lateral projections ( Fig. 6 A–C). Labral keel wide, height about 1.5 times width. Anterior margin of keel convex, with notch near the apex, apex blunt, rounded or rarely acute, posterior margin almost straight, with two clusters of setae.

Thorax two times longer than abdomen. Dorsal surface of abdominal segments not saddle-shaped. No abdominal projections.

Postabdomen ( Fig. 5 H, 6D–E) wide, of moderate length, maximum height in the middle of postanal portion. Length about 2.5–2.6 height. Ventral margin straight. Basis of claws bordered from distal margin by clear incision. Distal margin straight, distal angle broadly rounded. Dorsal margin weakly convex in postanal portion and weakly concave in anal one, distal part about 2.5 times longer than preanal one, postanal portion 1.5 times longer than anal one. Preanal angle weakly defined, postanal angle not defined. Preanal margin almost straight.

Postanal margin ( Fig. 5 J, 6F) with 10–12 well-developed, single sharp denticles, each with several spinules along anterior margin, size of denticle increasing distally. Length of longest denticles slightly more than width of base of postabdominal claw, 2.5–3 times exceeding the width of the denticle base. Anal margin with 4–5 groups of marginal spinules and setules. Postanal portion with 10–12 broad lateral fascicles, posteriormost setae of each fascicle longest, 1.5 times longer than neighboring marginal denticles. Anal portion with numerous smaller fascicles, spaced irregularly, in two-three rows. Postabdominal claw ( Fig. 6 G) slender, of moderate length, equal to preanal portion of postabdomen. Basal spine long and slender, about 1/3 of the claw length.

Antennule ( Fig. 6 H) elongated, narrow, length about 3–3.5 width, with 3–4 clusters of short setules at anterior face. Antennular seta thin, of about half length of antennule, arising at 2/3 distance from the base. Nine long terminal aesthetascs, two longest about 3/4 length of antennule itself, all other exceeding half length of antennule. All aesthetascs projecting beyond anterior margin of the head shield.

Antenna relatively short ( Fig. 6 I). Basal segment robust, with short seta between branches, branches relatively short, all segments cylindrical, subequal in length. Seta arising from basal segment of endopodite thin, almost reaching end of endopodite. Seta arising from middle segment of endopodite of similar size to apical setae. Spine on basal segment of exopodite significantly shorter than middle segment. Spines on apical segments shorter than apical segments.

Thoracic limbs: five pairs.

Limb I of moderate size ( Fig. 7 A–B). Epipodite oval, without process. Accessory seta long, only slightly shorter than ODL seta, with long setules in distal part. ODL with one seta.

IDL with three setae and 3–4 clusters of stiff setules. IDL seta 1 well-developed, slender, weakly curved, about 1/3 of ODL setae, setae 2 and 3 with an annulus and dense setules in distal part, seta 3 as long as ODL seta, seta 2 slightly shorter. Endite 3 with four setae subequal in length and several clusters of large spinules. Endite 2 with two long distally setulated setae, one of them equal to ODL seta, other 1.5 times longer, shorter setulated seta and a short naked seta with small sensillum near its base on anterior face of limb. Endite 1 with two 2-segmented setae, both setulated in distal part, a flattened plumose seta pointed the limb base, and a naked seta of same size as that of endite 2 on anterior face of limb. Ventral face of limb with 12–14 very long setules not organized in clusters. Two ejector hooks, subequal in size. Maxillar process with single seta.

Limb II sub triangular ( Fig. 7 C). Exopodite elongated, with long slender seta as long as exopodite itself, and a cluster long setules in distal part. Eight scraping spines, spines 6–8 subequal in length, spines 2–5 evenly increasing in length distally, spine 1 significantly longer than spine 2. Size of denticles on basal part of spines evenly decreasing from basal to distal spines. Distal armature of gnathobase with four elements, two lateral are minute, pointed, one of the middle elements broad, with row of denticles. Filter plate of seven setae, the posteriormost member two times shorter than others.

Limb III. ( Fig. 7 D–F) epipodite oval, without finger-like projection. Exopodite widening distally shape, with seven setae. Seta 3 longest, setae 6 about 1/3 length of seta 3, other setae very short. Setae 1–5 plumose, seta 6 in distal part armed bilaterally with hard setules, seta 7 naked. Distal endite with 3 setae, two distalmost members scraping, slender, sharp, with denticles in distal part, short bottle-shaped sensillum located between their bases; basalmost seta flattened, bilaterally armed with long setules, small sensillum near its base. Basal endite with 4 plumose setae increasing in size basally. Four pointed soft setae increasing in size basally, a small bottle-shaped sensillum near the distalmost seta. Distal armature of gnathobase with four elements. First one an elongated, narrowing distally sensillum, second strongly geniculated seta, third and fourth-spines with fused bases. Filter plate of seven setae of equal length.

Limb IV ( Fig 7 G.–H). Pre-epipodite setulated; epipodite oval, without any projection. Exopodite sub quadrangular, with six setae. Seta 1 being longest, setae 2–3 slightly shorter, seta 4–5 of about 2/3 length of seta 1, seta 6 about half length of seta 1. Setae 1–4 flattened, plumose, setae 5–6 thin, naked. Inner portion of limb IV with four setae and retort-shaped sensillum. Scraping seta slender, sharp, three flaming-torch seta of similar shape, decreasing in size basally, with 8–10 long setules each. Small cylindrical sensillum near the base of scraping seta, larger, elongated sensillum between the bases of middle and basal flaming torch setae. Three soft setae ( Fig. 7 I) slightly increasing in size basally. Gnathobase with one long two-segmented seta and a small hillock distally. Filter plate of five setae, base of distalmost seta very broad.

Limb V ( Fig. 7 J–L). P re-epipodite setulated; epipodite oval, with any projection. Exopodite large, eggshaped, not divided into lobes, with four plumose setae. Seta 1–3 long, subequal in length, seta 4 very short ( Fig. 7 K), more than five times shorter than seta 5. Inner lobe as broad, widening distally lobe, with setulated inner margin. At inner face ( Fig. 7 L), two setae densely setulated in distal part, one of them as long as longer than exopodite seta 3, other two times shorter, with a broad-based sensilla-like structures near its base. Filter plate absent.

Ephippial female unknown.

Male. Similar in shape to juvenile female of instar II but slightly larger ( Fig. 4 J–K). Maximum height in the third fourth of the body, height/length ratio about 0.55. Dorsal margin of valves almost straight.

Postabdomen broad, massive, maximum height at post anal angle. Length about 2.7 height ( Fig. 6 J). Ventral margin straight. Postabdominal claws situated on small protrusion in ventral portion of convex distal margin. The sperm ducts open above the protrusion, posteroventral and posterodorsal angles distinctly rounded. Dorsal margin weakly convex in postanal portion and weakly concave in anal one. Preanal and post anal angles weakly defined. Preanal margin almost straight. Clusters of thin setules in place of female marginal denticles. Lateral fascicles of setules same as in female. Postabdominal claw strongly curved, much shorter than in female, length about 2/3 of that of anal margin. Basal spine long, bent at the middle, about half length of claw itself.

Antennule ( Fig. 6 K) shorter and broader than in female, with 12 long terminal aesthetascs, three longest about 3/4 length of antennule itself, all other exceeding half length of antennule. Male seta located close to the end of antennule, about 1/3 length of antennule.

Limb I ( Fig. 7 M) with U-shaped copulatory hook, with free arm almost as long as limb itself. The IDL has four setae; IDL seta 1 very short and thin, IDL setae 2 and 3 much thinner and shorter than in female, the male seta curved, as long as seta 2. The copulatory brush seta about 2/3 of IDL seta 2. Ventral face of the limb under the copulatory brush with two rows of 9–11 stiff setules. Soft seta of endite 3 much longer and thinner than in female, a cluster of long stiff setules near its base.

Size. In females of first juvenile instar, length 0.31–0.34 mm, height 0.19–0.22 mm, in females of second juvenile instar, length 0.39–0.42 mm, height 0.23–0.25 mm. In adult female, length 0.52–0.61 mm, height 0.31–0.36 mm. Length of two studied adult males was 0.43 and 0.44 mm, height 0.24 mm in both specimens.

Distribution and ecology. A. yara is distributed from Rio Grande do Sul (32° S) to Distrito Federal (15° S), and it has been found in a variety of water bodies (large wetlands, lakes, and streams), but always in association with marginal macrophytes or decomposing tree leaves. It is not seems to be specially associated with muddy bottom, as other species of the group.

Taxonomic notes. Recent revisions of Alona s. lato by Van Damme & Dumont (2008a, b) show that the amorphous, artificial group of Alona -like animals can be split into two main branches (Hexalona - and Coronatella -branches), both of them of supergeneric rank. Each branch include several large groups of species, defined by Sinev (1998, 1999, 2001a,c, 2009a), all of them of generic rank, but most of them not yet formally recognized as a genus. Numerous species of unclear affinity are present in both branches of Alona s. lato, their presence adds to confusion. Present state of Alona taxonomy is far from acceptable, and future revisions are urgently needed.

According to Van Damme & Dumont (2008a), Alona s. str. is a very small group characterized by numerous peculiarities in the limb morphology. It includes Palaearctic A. quadrangularis (the type species of the genus), Congolese A. kolweizii , and A. boliviana , known from Bolivian Andes. Revision of the group is not finished, taxonomic status of North American populations of A. cf. quadrangularis is not clarified. Birge (1892) described populations of quadrangularis -group from Wisconsin, USA as a separate species, Alona lepida Birge, 1892 . While validity of A. lepida is not proved, specimens described by Birge definitely differs from A. yara , as they had maximum length of 0.8 mm and very dense longitudinal lines on valves. We think that, among these species, A. boliviana is the one most closely related to A. yara , as both species have the same number of large setules on limb I.

Alona quadrangularis was reported from several regions of Brazil ( Bergamin 1940; Santos-Wisniewski et al. 2002; Eskinazi-Sant'Anna et al 2005; Sterza & Fernandes 2006) and Venezuela (Zoppi de Roa & Lopez 2008). Presence of A. quadrangularis s.str., a Palearctic species, in South America seems quite unlikely ( Frey 1987, 1995), and we assume that these records also belong to A. yara . Other South American species, A. boliviana seems to be an endemic of Andes and unlikely to be found outside of these mountains. In this case, the distribution of Alona . s.str is similar to that of Alona of affinis -group in South Africa ( Sinev 2009a)—the lowlands is inhabited by A. affinis (Leydig, 1860) , while the restricted area of Drakensberg mountains inhabited by endemic species A. martensi Sinev 2009 .

Ruiz & Bahamonde (1989) reported the presence of Alona quadrangularis in Lake Puyehue, Chile (about 185 m over the sea level). The status of this populations should be investigated, as the site is not located in the Andes, but it is isolated from Eastern populations by the Andes.

Figures

FIGURE 4. Alona yara sp. n. A – I—from the type locality: A – B—juvenile females of instar I and II; C – Iparthenogenetic female: C – D—lateral view, E—ventral margin of valevs, F—posteroventral corner of valves, G – head shield, H – I—head pores; J – K—males from Bonita Pond Downstream, Planaltina. Scale bars 0.1 mm for A – D, E, L, 0.05 mm for F – K.

FIGURE 5. Alona yara sp. n., parthenogenetic females: A – lateral view, B—ventro-lateral view, C—posteroventral angle of valves, D – E—sculpture of valves, F – G—head pores, H—postabdomen, I—denticles and setules of postabdomen. Scale bars 0.1 mm for A – D, 0.05 mm for H, 0.01 mm for D, F, H, 0.002 mm for E, G.

FIGURE 6. Alona yara sp. n., A – I—parthenogenetic female from the type locality: A – C—labrum, D – Epostabdomen, F—postanal margin of postabdomen, G—postabdominal claw, H—antennule and outline of rostrum, Iantenna; J – K—male from Bonita Pond Downstream, Planaltina: J—antennule, K—postabdomen. Scale bars 0.01 mm for A – E, H, 0.05 mm for F – G, J – K.

FIGURE 7. Alona yara sp. n., A – L—limbs of parthenogenetic female from the type locality: A—limb I, B — ODL and IDL of limb I, C—limb II, D—exopodite of limb III, E—inner portion of limb III, F—scrapers of limb III in alternative view, G—exopodite of limb IV, H—inner portion of limb IV, I—soft setae and first seta of filter plate of limb IV, J—limb V, K—basal portion of exopodite V, L—inner portion of limb V (setules on inner lobe not shown); M—limb I of male from Bonita Pond Downstream, Planaltina. Scale bars: 0.1 mm for D, G, J, 0.05 mm for A – C, E – F, H – I, K – L.

Tables

TABLE 2. Main differences between A. yara, A. boliviana, A. kolwezii and A. quadrangularis.

Character	A. yara	A. boliviana	A. kolwezii	A. quadrangularis
Length of adult female	0.52–0.61 mm	0.68–0.79 mm	0.5–0.6 mm	0.6–0.8 mm
Body shape	Oval, slightly widening distally	Significantly widening distally	Low oval, not widening distally	Significantly widening distally