Alona margipluma, Sousa, Francisco Diogo R., Santos, Sandro, Güntzel, Adriana Maria, Diniz, Leidiane Pereira, Júnior, Mauro De Melo & Elmoor-Loureiro, Lourdes M. A., 2015

Sousa, Francisco Diogo R., Santos, Sandro, Güntzel, Adriana Maria, Diniz, Leidiane Pereira, Júnior, Mauro De Melo & Elmoor-Loureiro, Lourdes M. A., 2015, Description of a new species of the costata - group (Cladocera, Chydoridae, Aloninae) from Brazil, Zootaxa 4040 (4), pp. 445-457 : 446-453

Alona margipluma sp. nov.

(Figs. 1–4)

Etymology. the name “ margipluma ” comes from two Latin words, margo (= margin) and pluma, which refers to thin setules between ventral setae of the carapace.

Type locality. Criminosa Lake (21º40’28.8”S, 57º53’28.5”W), Porto Murtinho, Pantanal, Mato Grosso do Sul, Brazil.

Type material. Holotype: undissected, adult parthenogenetic female in a tube with 92% ethanol deposited at the Museum of Zoology of the University of São Paulo under access number MZUSP 33196. The label of the holotype is: “ Alona margipluma sp. n., 1 parth. ♀ from to Criminosa Lake, Porto Murtinho, Pantanal, Mato Grosso do Sul, Brazil. Holotype ”.

Material Studied. Paratypes. Eight adult parthenogenetic females and two juveniles from Criminosa Lake (21º40’28.8”S, 57º53’28.5”W), Porto Murtinho, Pantanal, Mato Grosso do Sul, Brazil. Material collected on 10.i.2010 and 19.i.2010, leg. Adriana Maria Güntzel ( FDRS 0275). Two adult parthenogenetic females from the Amonguijá River (21º41’11.3” S, 57º52’54.8” W), Porto Murtinho, Pantanal, Mato Grosso do Sul, Brazil. Material collected on 18.xi.2009, leg. Adriana Maria Güntzel ( FDRS 0274). Four adult parthenogenetic females and one juvenile from Baía da Célia, Fazenda Nhumirim (18°59'27.5"S, 56°39'41.0"W), Pantanal, Mato Grosso do Sul, Brazil. Material collected on 07.ix.2000 by Valéria Barros ( FDRS 0276). Two adult parthenogenetic females from the Cachoeira II reservoir (07°58.338'S, 38°19.628'W), Serra Talhada, Caatinga, Pernambuco, Brazil. Material collected on 18.vi.2011, leg. Leidiane Pereira Diniz ( FDRS 0378). One adult parthenogenetic female from Capetinga Stream (15°57’40.6” S, 47°56’36.7”W), Água Limpa Farm, Cerrado, Distrito Federal, Brazil. Material collected on 01.ix.2006 by GEEA. Two adult parthenogenetic females from Cabocla I pond (15º48'16.6''S, 47º14'58.8'W”), Campo de Instrução de Formosa, Cerrado, Distrito Federal, Brazil. Material collected on 07.viii.2009 by GEEA ( FDRS 0273). Six parthenogenetic females from Paranoá Lake (15°43’47” S, 47°52’58”W), Cerrado, Distrito Federal. Material collected on viii.2014 by Ciro Joko, Mariana Lessa and Elisângela Rangel ( FDRS 0383). Slides containing dissected individuals deposited at the Laboratório de Biodiversidade Aquática, Universidade Católica de Brasília ( CLLA 001 to CLLA 018).

Diagnosis. Female. Maximum height at middle of body, body about 1.5 times as long as high, weakly compressed laterally. Head with ocellus and eye of different size. Three main pores connected; anterior pore larger than others; a wide connection between the posterior and middle pores, connection between the middle pore and anterior pore wide or relatively narrow; transverse lateral head pores about 0.7 – 0.85 IP; deep and rounded pockets, about 1.5 times longer than lateral head pores. Carapace covered by dense longitudinal lines; ventral margin almost straight, with 45–49 plumose setae per valve; thin setulae between marginal setae. Labral keel without a notch. Antennule about two times longer than wide. Antenna, antennal formula: spines 001/101, setae 113/003. Apical spine of endopodite and exopodite long, of similar size, with visible denticles. Apical setae bisegmented and setulated. Postabdomen slightly narrowing distally, about three times as long as wide. Pre-anal margin of similar size to anal margin, and shorter than postanal margin. Anal margin slightly concave, with 3–4 denticle groups. Postanal portion of postabdomen with acute distal portion. Ten-twelve well developed marginal denticles, each with several spinules on its anterior margin. Terminal claw longer than anal margin, with one group of short spinules on its base; pecten armed with a row of outer spinulae decreasing in size towards distal portion. Basal spine relatively short, shorter than width of claw base, without spinulae or setulae. Limb I with ejector hooks different in size, accessory seta implanted near the base; ODL with a thin seta, serrulated in the distal part; IDL with three setae; seta 1 small and thin; setae 2 and 3 bisegmented and armed with setulae, similar in size to ODL setae. Limb II with elongated exopodite bearing a non-setulated seta; scrapers 3 and 7 armed with robust denticles as compared to other scrapers. Limb III, fourth and fifth setae of exopodite relatively long. Limb IV, exopodite subquadrangular with setae 1–4 plumose; gnathobase armed with a bottle-shaped sensillum. Limb V, exopodite with four setae, divided into two lobes; gnathobase as a rounded lobe; filter comb with three long setae. Limb VI present. Male and ephipial female unknown.

Description. Parthenogenetic female. Habitus (Figs. 1A–B; 4A). Animal of a relatively large size 0.32–0.43 mm; in a lateral view, carapace oval, maximum height at middle of body, which is about 1.5 times as long as high. Dorsal margin convex. From a ventral view, body weakly compressed laterally. Dorsal keel absent.

Head (Figs. 1A; 2A–D; 4A, C). Ocellus and eye of different size. Headshield with maximum width behind the mandibular articulation, posterior margin wavy. Rostrum short, rounded, projected towards ventral margin of carapace. Three main pores connected; anterior pore larger than others; a wide connection between posterior and middle pore, connection between middle and anterior pore wide or relatively narrow. PP about 0.7–0.95 IP. Transverse lateral head pores about 0.7 – 0.85 IP, located at the level of middle main head pores. Deep and rounded pockets, about 1.5 times longer than lateral head pores.

Labrum ( Fig. 2 E) of moderate size. Labral keel without a notch; anterior margin convex, posterior margin with two clusters of setules.

Carapace (Fig. 1C–D; 4B) covered by longitudinal lines. Ventral margin almost straight, with 45–49 plumose setae per valve; thin setulae between marginal setae; middle group consists of short marginal setae; posterior group of long setae decreasing in size towards the posteroventral corner. Posterior margin armed with spinulae not arranged in groups and not projected beyond the margin.

Mandibles large relatively to body size.

First maxilla ( Fig. 2 H) well developed, with two long setulated setae.

Antennule ( Fig. 2 F) with length two times the width; four rows of setules on antennular body. Antennular sensory seta slender and short, about 2–2.5 times smaller than antennular body, inserted at two-thirds of antennule length from its base. Nine aesthetascs of different length, all projecting beyond the tip of rostrum. None of them exceeds the length of the antennules.

Antenna ( Fig. 2 G). Two coxal setae of equal length. Basal segment thick, with many spinulae and a short spine distally. First segment of exopodite with long and slender spinulae near its base and short spinulae at its terminal portion. Second segment with long and slender setulae located at median portion and short spinulae in its terminal portion. Endopodite segments with short spinulae at its terminal portion. Antennal formula: spines 001/101; setae 113/003. Setae on first segment of exopodite thin, not reaching mid length of terminal setae. Seta on second segment of exopodite bisegmented. Spine on first segment of endopodite short, not exceeding distal end of second segment. Apical spines of similar length, longer than apical segments and with visible denticles. Apical setae bisegmented and setulated.

Abdomen about two times shorter than thorax, armed with three rows of long abdominal setae.

Postabdomen (Figs. 1E–G; 4D–G). Slightly narrowing distally, about three times as long as wide, ventral margin slightly convex with at least three rows of spinulae. Pre-anal margin of similar size to anal margin and shorter than postanal margin. Anal margin slightly concave, with 3–4 groups of spinulae. Postanal margin almost straight, distal angle acute, slightly projected. Lateral fascicles arranged in 8–9 groups; first spinule of each fascicle longer and thicker than others; first three fascicles exceeding postabdomen margin. Ten-twelve well developed marginal denticles, each one with several spinulae on its anterior margin; most proximal denticles grouped. Postabdominal seta (Fig. 1E). About two times shorter than postabdomen; proximal portion naked; long setules armed bilaterally towards its distal portion. Terminal claw (Figs. 1E–H; 4G). Implanted in a projected basis of postabdomen, slightly longer than anal margin, uniformly curved, with a group of short spinules at its base; external pecten armed with a row of outer spinules. Basal spine relatively small, shorter than width of claw at its base, without spinulae or setulae.

Six pair of limbs.

Limb I ( Fig. 2 J–K). Epipodite oval with a long projection. Accessory seta implanted near base of ODL, which has a thin seta, serrulated in its distal part, with length about the same as the longest IDL seta; IDL (en 4) with three groups of spinules on its face and three setae: seta 1 about three times shorter than setae 2; setae 2 and 3 bisegmented and armed with setulae, seta 3 slightly longer than seta 2. Endite III with four setae; posterior setae (a– b) setulated, longer than the other two setae (posterior seta c and anterior seta 1). Endite II with one row of spinules; three posterior setae present (d–f), setae (f) and (e) similar in length and with thick spinules on the lateral face; setae (d) exceeding the midlength of seta (e); endite armed a single anterior stiff seta. Endite I with three posterior setae (g–i), two being bisegmented and setulated in distal part (g–h) and a short flat plumose seta (i), and a thin anterior stiff seta. Ejector hooks of different length. Ventral face of the limb with six groups of setulae organized in clusters, decreasing in size towards the distal portion. Gnathobase not studied.

Limb II ( Fig. 3 A–B). Exopodite elongated, with two rows of setulae and a naked seta. Inner limb portion armed with eight scrapers gradually decreasing in length towards gnathobase. Scrapers 3 and 7 armed with robust denticulation. Distal armature of gnathobase armed with four elements: first a sensillum, second an element with distal portion geniculated, third element armed with denticles, fourth element relatively short, not sharp. Filter comb with seven setae; first seta short, robust, with dense and long setulae; other setae long and with short setulae.

Limb III ( Fig. 3 C–D). Epipodite not studied. Exopodite relatively large, subquadrangular, with five distal and two lateral setae. Setae 1–2 setulated, similar in length. Third seta long, setulated, about 1.5 times longer than the sixth seta. Fourth and fifth setae shorter than setae 6–7, but longer than setae 1–2. Sixth seta about 1.3 times longer than the seventh seta, both naked. Distal endite with one sensillum and three setae (1–3), two scraper-like and similar in length (1–2), and third seta slightly curved and armed with many setules bilaterally implanted (3); four plumose posterior setae similar in length. Basal endite with four soft anterior setae, distalmost seta very long and robust; two sensillum near to first soft seta present. Gnathobase armed with four elements, the first being a cylindrical sensillum, the second a strong geniculated seta, third and fourth elements with tip acute, naked. Filter comb with seven setae.

Limb IV ( Fig. 3 E–H; 4H). Pre-epipodite round. Epipodite rounded, with a long projection. Exopodite subquadrangular with six marginal setae: setae 1–4 plumose; seta 1 slightly shorter than seta 2; third seta longer than all others; fourth seta subequal in length to the fifth seta; fifth seta slightly setulated unilaterally; sixth seta naked. Distal endite with four setae (1–4), one scraper-like and armed with one sensillum at the base (1), three flaming-torch-like (3–4); the first flaming-torch robust, with long setules (2) and three soft setae increasing in size proximally. Gnathobase armed with one bottle-shaped sensillum and one setulated seta implanted on a robust base. Filter plate with five slender setae.

Limb V ( Fig. 3 I). Pre-epipodite oval and densely setulated; epipodite with long projection. Exopodite unclearly divided into two lobes, with four plumose setae decreasing in size towards the internal lobe; setae 1–2 similar in length; fourth seta about 1.3–1.5 times shorter than the third seta. Internal lobe very wide, oval and with long setulae; two setulated setae on the inner face of the lobe, first seta about two times longer than the other. Gnathobase as a rounded lobe; filter comb with three long setae.

Limb VI ( Fig. 3 J). An elongated lobe, about two times longer than wide; apical margin of the lobe with long setulae; proximal margin armed with short setules.

Ephippial female. Unknown.

Male. Unknown.

Differential diagnosis. Alona margipluma sp. nov. clearly differs from species of the rustica -branch (see Hudec 1998; Sinev 1999; Sinev 2009a; Van Damme & Eggermont 2011), such as from Neotropical A. iheringula , in the morphology of the postabdomen, and main and lateral head pores. Differences in aforementioned structures are also observed as compared with A. weltneri Keilhack, 1905 (see Van Damme et al. 2011). Specifically, Alona margipluma sp. nov. differs from A. setigera because it has three main head pores. Because its large lateral head pores and distal postabdominal angle acute, Alona margipluma sp. nov. resembles A. costata , A. cheni and A. natalensis , but the former has different morphology of the exopodite of the limb V and the lateral head pores. Such as, in A. cheni and A. natalensis the pockets are shallow, about 2 and 3 times smaller than length of lateral head pores, respectively. In A. costata the pockets are deep, about two times longer than lateral head pores, and the basal spine on the postabdomen is longer than the width of terminal claw base. Alona margipluma sp. nov. has deep pockets, about 1.5 times longer lateral head pores, and basal spine is shorter than the width of terminal claw base. Furthermore, Alona margipluma sp. nov. can be recognized by the presence of thin setulae between setae on the valves, absent in another species (see Sinev 1999, 2008); long setae 4–5 on exopodite of the limb III; and bottleshaped sensillum on the basal endite of the limb IV. Other differences among A. costata , A. setigera , A. cheni , and A. natalensis are summarized in Table 1.

Distribution and ecology. So far, Alona margipluma sp. nov. has been found only in Brazil, in five localities. However, as the records of A. margipluma sp. nov. observed in this study are very distant from each other, it is possible that distribution of this species covers a considerable portion of the country. Alona margipluma sp. nov. is a species with preference for lentic waters; however, it was also found in lotic environments, associated with leaves in backwater zones (Capetinga Stream and Amonguijá River). Water bodies inhabited by A. margipluma sp. nov. (except Baía da Célia and Paranoá Lake) have temperatures ranging between 19.7 and 33.5 ºC, electric conductivity <300 µS/cm, pH 4.63–7.3, turbidity 31.3–100 NTU, total dissolved solids 0.071–0.187 g /L and dissolved oxygen 4.11–7.3 mg /L. In some localities, Alona margipluma sp. nov. was found together with A. cf. setigera , A. ossiani , A. iheringula , and A. guttata . Alona margipluma sp. nov. was collected associated exclusively with the spongy air-filled roots of Ludwigia helminthorrhiza Mart. in the Cachoeira II reservoir (Caatinga) or with a multispecific bank of macrophytes in the Cabocla I pond (Cerrado).

Figures

FIGURE 2. Alona margipluma sp. nov., parthenogenetic females. A, headshield. B – D, head pores. E, labral keel. F, antenule. G, antenna. H, maxila. I, limb I. J, limb I, ejector hooks and epipodite. K, limb I, IDL and ODL. Scale bars = 50 µm.

FIGURE 3. Alona margipluma sp. nov., parthenogenetic female. A, limb II. B, limb II, gnathobase. C, limb III, exopodite. D, limb III, endites. E, limb IV, exopodite. F, limb IV, endites. G, limb IV, sensillum. H, limb IV, distal endite seta. I, limb V. J, limb VI. Scale bar = 50 µm.