Disparalona (Mixopleuroxus) leptorhyncha Daday 1905

Autor: Sousa, Francisco Diogo R., Elmoor-Loureiro, Lourdes M. A., Mugnai, Riccardo, Panarelli, Eliana Aparecida, Paggi, Juan César
Rok vydání: 2018
Předmět:
DOI: 10.5281/zenodo.5980005
Popis: Disparalona (Mixopleuroxus) leptorhyncha (Daday, 1905) Figs 1–3, 13 Leptorhynchus rostratus – Daday 1905: 169 –179, figs 24–25. Diagnosis Body elongated, length 0.36–0.58 mm, ventral margin with narrow aperture extending to posterior end. Carapace covered by striae, posterodorsal corner with or without notch; posterior border bears spinulae of which the proximal is as long as distal ones. Rostrum very long, about 3.5 times as long as antennular body, strongly curved. Labrum elongated, without keel. Antennule about twice as long as width, not exceeding the tip of rostrum. Antenna with coxal setae about 1.5 times as long as first exopodite segment, first endopodite segment armed with a short spine about 0.4 of the apical spine length. First limb with IDL seta 1 slender and naked, about 1.6 times shorter than second seta, seta 2 about 1.3 times shorter than third seta and armed with long setulae, third seta relatively slender, hook-like, heavily chithinized and with a group of short spines inserted at mid-length of seta. Second limb exopodite short, armed with a seta shorter than exopodite itself, inner limb portion armed with eight slender scrapers. Third limb exopodite rectangular, about three times as long as the width, fourth seta setulated, about two times as long as third seta. Fourth limb with first seta very slender and short, about 0.4 of length of the second seta. Fifth limb exopodite wide, rounded, armed with four plumose setae. Postabdomen anal margin about 0.7 of the preanal margin length, 12–13 marginal merged denticles, distalmost denticles with width-at-base/height ratio about 0.45, lateral fascicle formed by thin spinulae not separated in groups. Basal spines naked, distal, about 0.28 of the postabdominal claw length, proximal about 2.5 times shorter than distal one. Material examined BRAZIL – Distrito Federal: 33 parthenogenetic ♀♀, Ecological station of Águas Emendadas, Bonita Pond, 15°35´22.1″ S, 47°41´50.1″ W, Aug. 2006 and Mar. 2009, GEEA and L.M.A. Elmoor-Loureiro leg. (FDRS 0260–0264; EL 00467; EL 01268–01269; EL 01271–01277); 2 parthenogenetic ♀♀, Joaquim Medeiros Pond, 15°38´15.9″ S, 47°41´29.5″ W, Jan. 1979 and Sep. 2008, GEEA and L.M.A. Elmoor-Loureiro leg. (FDRS 0265; EL 01270); 12 parthenogenetic ♀♀, Gansos Pond, 15°40´33.1″ S, 47°41´37.4″W, Aug.2006 and Mar.2009, GEEA leg. (FDRS 0266–0268). – Goiás: 5parthenogenetic ♀♀, Formosa, Instruction Field of the Brazilian Army, Grande Pond, 15°49´59.29″ S, 47°13´55.42″ W, Aug. 2009 and Dec. 2009, GEEA leg. (FDRS 0269; EL 01746); 1 parthenogenetic ♀, Mineiros, Emas National Park, Capivaras Pond, 18°16.245´S, 52°50.529´W, Dec. 2000, G. Miranda leg. (EL 00884); 10 parthenogenetic ♀♀, Alto Paraíso, Chapada dos Veadeiros National Park, Sete Lagoas Pond, 14°04´11.47″ S, 47°39´18.31″ W, Jun. 2012, GEEA leg. (EL 02287). – Bahia: 2 parthenogenetic ♀♀, Pond in Roda Velha, 12°47´18″ S, 45°57´06″ W, Jul. 1985, L.M.A. Elmoor-Loureiro leg. (EL 0 0 466, EL 01266). – Minas Gerais: 4 parthenogenetic ♀♀, Januária, Peruaçu State Park, Jatobá pond, 14°56´13″ S, 44°37´35″ W, Sep. 2003, M.B.G. Souza leg. (EL 01976). – Pará: 1 parthenogenetic ♀, Porto Trombetas, Trombetas River, 1°30´0″ S, 56°19´30.34″ W, Jan. 1989, R.L. Bozelli leg. (EL 01825). Redescription of adult parthenogenetic female GENERAL HABITUS (Fig. 1A–E). Body elongated, length 0.36–0.58 mm, maximum height at middle of body, height/length ratio about 0.4; dorsal margin not arched, without dorsal keel or lateral projection; in dorsal and ventral view body not laterally compressed; ventral margin with narrow aperture which is extending to posterior end. CARAPACE (Fig. 1A–F). Covered by striae; anteroventral margin with a widened flange; ventral margin almost straight; 72–79 plumose setae per valve (the real number of setae is not represented in the figures), of which the posterior and anterior are as long as the middle ones, anterior setae located exactly at the valve margin and clearly not articulated, posterior setae internally articulated; posterodorsal corner with or without notch; posteroventral corner rounded, posterior border bears spinulae of which the proximal is longer than the distal ones. CEPHALIC STRUCTURES (Fig. 1G–N). Ocellus smaller than eye. Rostrum very long, about 3.5 times as long as antennular body, strongly curved, reaching the same level of ventral line of valve, with tip sharp or bifid; in frontal view may not be straight. Head shield (Fig. 1I –J). Anterior and posterior region triangular-shaped, covered by striae, posterior border irregularly waved; two main pores with two closely-set tiny pores between them, tiny pores located halfway between main head pores, PP/ IP about 0.35. Labrum (Fig. 1M–N). Elongated, without keel; lateral horns present. Maxilla (Fig. 1L). Well developed, with three setulate setae. Antennule – A1 (Fig. 1O). Length about two times the width, not exceeding the tip of rostrum; antennular sensory seta slender, about 1.3 times length of antennular body, inserted near to apex of the antennular body; nine aesthetascs which do not exceed the length of antennular body. Antenna – A2 (Fig. 1P). Coxal setae very long, about 1.5 times as long as first exopodite segment; basal segment thick with short and thin spine; first exopodite segment longer than first segment of endopodite; second exopodite segment with a long seta reaching or exceeding midlength of longest apical seta; first endopodite segment armed with a short spine about 0.4 of length of the apical spine; exopodite apical spine about 1.8 times longer than the segment itself, endopodite apical spine of similar length to apical segment; apical spines armed with short denticles. Antennal formula (exo/endo): spines 001/101, setae 113/003. THORACIC LIMBS (Fig. 2A–G). Five pairs of thoracic limbs. First limb (Fig. 2A). Epipodite oval shaped without projection; ODL armed with a short seta and a thin serrated seta longer than IDL first seta; IDL (en 4) with two groups of short setulae; three setae present, third seta relatively slender, hook-like, heavily chithinized and with a group of short spines inserted at mid-length of seta; seta 1 slender and naked, about 1.6 times shorter than second seta; seta 2 about 1.3 times shorter than third seta, armed with long setulae; endite 3 with four setae, posterior setae (a–b) of similar length and shorter than anterior seta 1, seta (c) of similar length to setae (a–b); endite 2 with three posterior setae present (d–f), seta (f) about 1.2 times shorter than seta (e), both setae bear thin setulae on the lateral face, seta (d) setulated and about two times shorter than seta (e); endite 1 with three posterior setae of similar length (g–i), bisegmented and densely setulated on distal part; stiff setae long, of similar length to seta (f), seta (j) not studied; ejector hooks of similar length to corm of limb and armed with spines; ventral face of the limb with nine groups of setulae organized in clusters, increasing in length towards the distal portion. Gnathobase as a setulated setae. Second limb (Fig. 2B–C). Exopodite short, armed with a seta shorter than exopodite itself; inner limb portion armed with eight slender scrapers; setulation on the scrapers is inconspicuous; scraper 1 with an accessory seta at its base, scraper 2 about 0.6 of length of scraper 1; proximal portion of gnathobase flattened; distal portion armed with three elongated elements, first element with distal portion sharp, geniculated, and setulated, second element armed with strong denticles, third element longer than mid length of others elements; filter comb with seven setulated setae. Third limb (Fig. 2D). Epipodite oval with a long projection; exopodite rectangular, about three times as heigh as wide, with four distal and three lateral setae; seventh seta setulated and longer than sixth and fifth setae; fourth seta setulated, about twice as long as third seta; third seta similar in length to exopodite corm; second seta setulated, longer than third and first setae, about 0.68 of length of the fourth seta; first seta thin and naked; distal endite with three slender setae, seta 2 about 0.7 of length of seta 1 (third seta not studied); six long and plumose posterior setae decreasing in length towards gnathobase (a–f); basal endite with four setae of similar length (4–7); gnathobase armed with a long and cylindrical sensillum; filter comb with eight setulated setae. Fourth limb (Fig. 2E–F). Pre-epipodite oval and densely setulated; epipodite oval with a long projection; exopodite with seven marginal setae; setae 2–7 plumose; seventh seta shorter than sixth and fifth setae and similar in length to third seta; fourth setae relatively long, about twice as long as second seta; first seta very slender and short, about 0.4 of length of the second seta; distal endite with four setae (1–4), one scraperlike (1), three setae flaming-torch-like slightly setulated (3–4) and similar in length to seta 1; basal endite armed with three setulated setae of similar length; gnathobase thick, with three elements, armed with one curved setulated seta which is about twice as long as width of endite; filter plate with six setae. Fifth limb (Fig. 2G). Pre-epipodite rounded and densely setulated; epipodite oval with a long projection; exopodite wide, rounded, armed with four plumose setae and two setulated hillocks implanted near first seta; first seta about 0.75 of length of the second seta; third and fourth setae similar in length and longer than other setae of limb; internal lobe elongated, relatively rectangular and with many setulae, two setae of similar length on inner face of the lobe, seta 1 armed laterally with thick spinulae and setulae; seta 2 setulated; filter comb with four setulated setae, about 0.75 of length of internal lobe setae. ABDOMINAL AND POSTABDOMINAL STRUCTURES. Abdomen (Fig. 1A). About three times shorter than thorax. Postabdomen (Fig. 3A–D). About 3.2 times as long as wide, ventral margin relatively straight with two rows of short spinulae; anal margin about 0.7 of length of the preanal margin, armed with a group of thin spines; postanal margin uniformly rounded and very long, about 2.5 times as long as anal margin, armed with 12–13 marginal merged denticles, distalmost denticles with width-at-base/height ratio about 0.45; lateral fascicle formed by thin spinulae not separated in groups; postabdominal setae about 0.7 of length of the postabdomen, bisegmented, armed with setulae from distal segment. Postabdominal claw (Fig. 3A, D). With two basal spines, about 0.28 of the length of the postabdomen and 1.3 times longer than anal margin, base naked; inner group of pecten with thin proximal spinulae; outer group separated in two groups, proximal with ticker spinulae. Basal spines (Fig. 3A, D). Naked, distal about 0.28 of length of the postabdominal claw, proximal about 2.5 times shorter than distal one. EPHIPPIAL FEMALE, EPHIPPIUM. Unknown. Male See Van Damme & Dumont (2010). Remarks According to Smirnov (1996a, 1996b), Disparalona (M.) leptorhyncha was initially described as Leptorhynchus rostratus. As the name rostratus was preoccupied in the genus of Disparalona, Smirnov (1996a) designated the epithet leptorhyncha. Disparalona (M.) leptorhyncha differs from all species of the genus by the absence of longitudinal lines on the carapace, antenna with very long coxal setae, long and curved rostrum, closely-set tiny pores located halfway between main head pores, labrum elongated and without keel (Fig. 1M–N); third seta on the IDL relatively long and slender, ejector hook in the first limb very long, stiff setae on the endites 2–3 long, of similar length to seta (f); seta on the exopodite of second limb short, scrapers long and slender, proximal portion of gnathobase flattened and naked (Fig. 2B–C); third limb exopodite three times as heigh as wide; postabdomen with short anal margin, postanal margin rounded with 12–13 merged denticles. This set of characters makes Disparalona (M.) leptorhyncha the most peculiar species of the genus when compared with hamata -complex and Holarctic species (Alonso 1996; Flössner 2000; Kotov & Sinev 2011; Klimovsky et al. 2015). Distribution and biology Disparalona (M.) leptorhyncha is an endemic species, with distribution limited to South America. This species occurs from Paraguay to the Brazilian Amazon (Daday 1905; Smirnov 1996a, 1996b; Van Damme & Dummont 2010; Sousa et al. 2013; Debastiani-Júnior et al. 2015; Elmoor-Loureiro 2017). Disparalona (M.) leptorhyncha is very common in reservoirs, floodplain environments, ponds, and shallow lakes.
Published as part of Sousa, Francisco Diogo R., Elmoor-Loureiro, Lourdes M. A., Mugnai, Riccardo, Panarelli, Eliana Aparecida & Paggi, Juan César, 2018, A revision of the genus Disparalona (Cladocera, Chydorinae) in South America, pp. 1-34 in European Journal of Taxonomy 460 on pages 3-9, DOI: 10.5852/ejt.2018.460, http://zenodo.org/record/1468450
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