Disparalona (Mixopleuroxus) lucianae, Sousa & Elmoor-Loureiro & Mugnai & Panarelli & Paggi, 2018

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, European Journal of Taxonomy 460, pp. 1-34 : 15-21

Disparalona (Mixopleuroxus) lucianae sp. nov.

urn:lsid:zoobank.org:act:CA6C7D2D-BA07-4B0B-AE60-BDB6223F907F

Figs 7–9 , 13

Disparalona cf. hamata – Sousa & Elmoor-Loureiro 2008: 163, figs 3d–e. — Debastiani-Júnior et al. 2015: 24, table 2.

Diagnosis

Body elongated, oval, length 0.36–0.48 mm, dorsal margin uniformly arched, ventral margin with wide aperture which is located after middle of body, toward the anterior part. Carapace covered by longitudinal lines and striae between them, posterodorsal corner without evident notch; posteroventral corner rounded, posterior part bears a group of long and thin spinulae that exceed the border. Rostrum short, about 1.7 times longer than antennular body, slightly curved with tip sharp. Antennule length about two times the width, not exceeding the tip of rostrum. Antenna with coxal setae slightly shorter than first exopodite segment, first endopodite segment armed with a short spine about 0.3 of length of the apical spine. First limb IDL seta 1 slender and armed with thin spines at distal part, about 2.2 times shorter than third seta; seta 2 about 1.2 times shorter than third seta, armed with long hard setulae, third seta relatively thick, hook-like, heavily chithinized and with a group of short spines at distal part. Second limb exopodite with a long seta about 2.8 times as long as exopodite itself, inner limb portion armed with one element and eight scrapers, of which 1 and 3 of similar length. Third limb exopodite about 2.5 times height than width, fourth seta setulated, about 1.4 times as long as third seta. Fourth limb first seta slender and short, about 0.4 of length of the second seta. Fifth limb exopodite wide, rounded, armed with four plumose setae. Postabdomen with anal margin about 1.2 times shorter than preanal margin, 10 merged marginal denticles; distalmost denticle with width-at-base/height ratio about 0.23. Basal spines naked, distal about 0.22 of length of the postabdominal claw, proximal about 1.8 times shorter than distal one.

Etymology

The epithet ‘ lucianae ’ is given in honor to limnologist Luciana de Mendonça Galvão, an active researcher in the field of aquatic ecosystems in the Brazilian Cerrado Biome.

Material examined

Holotype BRAZIL: parthenogenetic ♀, Minas Gerais, Diamantina, Sempre Vivas National Park, Jequitaí River , 17°54´9.90″ S, 43°46´34.93ʺ W, Sep. 2010, GEEA leg. ( MUZUSP 38018 ).

Paratypes BRAZIL – Bahia: 12 parthenogenetic ♀♀, Bahia, Salvador, Lagoa de Duna , 12°50´55ʺ S, 38°16´53ʺ W, Oct. 2001 and Jul. 2002, E.M. Silva leg. ( EL 0 0 460 , EL 01254–01265 , EL 00461 ). – Goiás: 1 parthenogenetic ♀, Mineiros, Emas National Park, Formosa River , 18°15.591´S, 53°01.965´W, Nov. 2006, V. Barros leg. ( EL 00463 ); 27 parthenogenetic ♀♀, Alto Paraíso, Chapada dos Veadeiros National Park , Carioquinha waterfall, 14°08´41ʺ S, 47°49´17ʺ W, Mar. 2017, R.C. Sousa leg. ( FDRS 0519 ). – Minas Gerais: 100 parthenogenetic ♀♀, Diamantina, Sempre Vivas National Park, Jequitaí River, 17°54´9.90ʺ S, 43°46´34.93ʺ W, Sep. 2010 and May. 2010, GEEA and L.M.A. Elmoor-Loureiro leg. (EL 01940–01941, FDRS 0509); 75 parthenogenetic ♀♀, Diamantina, Sempre Vivas National Park, Inhacica River, 17°50´11.40ʺ S, 43°45´58.61ʺ W, May. 2010 and Sep. 2010, GEEA leg. (EL 0 2417, FDRS 0510); 1 parthenogenetic ♀, Diamantina, Sempre Vivas National Park, Filipe River, 17°29´S, 43°21´W, Sep. 2010, GEEA leg. (EL 02418); 26 parthenogenetic ♀♀, Diamantina, Sempre Vivas National Park, Preto River, 17°55´54.01ʺ S, 43°48´50.33ʺ W, May. 2010 and Jul. 2012, GEEA and C.F.A. Barros leg. (EL 0 1855, FDRS 0511–0515).

Description of adult parthenogenetic female

GENERAL HABITUS ( Figs. 7A–H ). Body elongated, oval, length 0.36–0.48 mm, maximum height located after middle of body, height/length ratio about 0.55; dorsal margin uniformly arched, without dorsal keel or lateral projection; in dorsal and ventral view body not laterally compressed; ventral margin with wide aperture which is located after middle of body, toward the anterior part.

CARAPACE ( Fig. 7D–E ). Covered by longitudinal lines and striae between them; anteroventral margin with a widened flange; ventral margin with slight depression before mid length of body; 80 plumose setae per valve (the real number of setae is not represented in the figures), of which the posterior and anterior groups are longer than middle group, anterior and posterior setae internally articulated, setae around median part located exactly at the valve margin and clearly not articulated; posterodorsal corner without evident notch; posteroventral corner rounded, posterior part bearing a group of long and thin spinulae that exceed the border.

CEPHALIC STRUCTURES ( Fig. 7I –N ). Ocellus smaller than eye. Rostrum short, about 1.7 times longer than antennular body, slightly curved with sharp tip; straight in frontal view. Head shield ( Fig. 7J–K ). Anterior and posterior region triangular shaped, covered by striae; two main pores with two closely-set tiny pores between them, which are located closer to the anterior than posterior main pore, PP/IP about 0.5. Labrum ( Fig. 7L ). Keel not prominent, distal portion short and rounded, lateral horns present. Maxilla. Not studied. Antennule – A1 ( Fig. 7M ). Length about two times the width, not exceeding the tip of rostrum; antennular sensory seta slender, slightly shorter than antennular body, inserted in the last third of antennular body; nine aesthetascs which do not exceed the length of antennular body. Antenna – A2 ( Fig. 7N ). Coxal setae slightly shorter than first exopodite segment; basal segment thin with a short and thin spine; first exopodite and endopodite segments of different lengths; first endopodite segment armed with a short spine about 0.3 of length of the apical spine; exopodite apical spine about 1.3 times as long as apical segment and about 1.6 times as long as endopodite apical spine. Antennal formula (exo/endo): spines 001/101, setae 113/003.

THORACIC LIMBS ( Fig. 8A–J ). Five pairs of thoracic limbs. First limb ( Fig. 8A–B ). Epipodite not studied; ODL armed with a thin seta and a serrated seta similar in length to IDL third seta; IDL (en 4) with two group of short setulae, three setae present, third seta relatively thick, hook-like, heavily chithinized and with a group of short spines at distal part; seta 1 slender and armed with thin spines at distal part, about 2.2 times shorter than third seta; seta 2 about 1.2 times shorter than third seta, armed with long hard setulae; endite 3 with four setae, posterior setae (a–b) of different length and longer than anterior seta 1, seta (c) of similar length to seta (a); endite 2 with three posterior setae (d–f), seta (f) about 1.5 times shorter than seta (e) being that both setae bear thin setulae on the lateral face, seta (d) setulated and about 2.5 times shorter than seta (e), stiff setae similar in length to seta (d); endite 1 with three posterior setae of similar length (g–i), bisegmented and densely setulated from distal part; stiff setae about 1.5 times shorter than seta (f), seta (j) not studied; ejector hooks about 1.3 times shorter than corm of limb and armed with spines; ventral face of the limb with seven groups of long setulae organized in clusters. Gnathobase as a setulated seta. Second limb ( Fig. 8C ). Exopodite with a long seta armed laterally with short spinulae, about 2.8 times longer than exopodite itself; inner limb portion armed with one element and eight scrapers; scrapers 1–5 armed with thin setulae, 6–8 armed with thick spinulae; scrapers 1 and 3 of similar length; scraper 2 slightly shorter than scrapers 1 and 3; scraper 4 about 1.5 times shorter than scraper 3; scraper 5 longer than scraper 4; scraper 6 about 1.5 times as long as scrapers 7 and 8; proximal portion of gnathobase not elongated and armed with six long setulae; distal portion armed with four elements, first element is a sensillum, second element elongate with distal portion sharp, setulated and geniculated, third element armed with strong denticles, fourth element longer than mid-length of other elements; filter comb with eight setulated setae, first seta densely setulated and shorter than others. Third limb ( Fig. 8D–E ). Epipodite oval with a short projection; exopodite rectangular, about 2.5 times as heigh as wide, with four distal and three lateral setae; seventh seta long, about 2.4 times as long as sixth seta and about twice as long as fifth setae; fourth seta setulated, about 1.4 times as long as third seta; third seta setulated, longer than length of exopodite corm, about 1.6 times shorter than second seta; second seta setulated, about 1.3 times as long as first setae, longer than fourth seta; first seta thin, armed laterally with short spinulae; setae (1–2) of distal endite slender, seta 2 about 0.75 of length of the seta 1, seta 3 not studied; six long and setulated posterior setae of similar lengths (a–f); basal endite with four setae (3–6), distalmost seta longer than others; gnathobase armed with a long and cylindrical sensillum; filter comb with eight setulated setae. Fourth limb ( Fig. 8F–I ). Pre-epipodite rounded and densely setulated; epipodite oval without projection; exopodite with seven marginal setae; setae 3–7 plumose; seventh seta shorter than sixth, fifth, fourth and third setae; fifth seta slightly shorter than fourth seta; fourth seta about twice as long as second seta; first seta slender and short, about 0.4 of length of the second seta; distal endite with four setae (1–4), one scraper-like (1), three setae flaming-torch-like slightly setulated (3–4) longer than seta 1; basal endite armed with three setulated setae of similar length; gnathobase thick, with two elements, armed with one curved setulated seta about longer than width of endite; filter plate with six setae. Fifth limb ( Fig. 8J ). Pre-epipodite rounded and densely setulated; epipodite oval without 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; second seta about 0.7 of the length of the third setae; fourth seta about 0.9 of the length of the third seta; internal lobe elongated, relatively oval and with many setulae, two setae of different length on inner face of the lobe, seta 1 armed laterally with thick spinulae and setulae; seta 2 setulated, about 0.6 of length of the seta 1; gnathobase without elements; filter comb with four setulated setae longer than seta 2 of internal lobe.

ABDOMINAL AND POSTABDOMINAL STRUCTURES. Abdomen ( Fig. 7A ). About three times shorter than thorax. Postabdomen ( Fig. 9A–E ). About 3.4 times as long as wide, ventral margin slightly arched with two rows of short spinulae; anal margin about 1.2 times shorter than preanal margin; anal margin armed with one group of thin spines; postanal margin almost straight and long, about 1.6 times as long as anal margin, armed with 10 merged marginal denticles; distalmost denticle with width-at-base/height ratio about 0.23; lateral fascicle separated in 11 groups with short and thin spinulae, distalmost group bears 2–5 spinulae; postabdominal setae about 0.46 of length of the postabdomen, bisegmented, armed with setulae from distal part. Postabdominal claw ( Fig. 9A–B, D–E ). With two basal spines, about 0.25 of the length of the postabdomen and slightly shorter than anal margin, base naked; inner group of pecten separated in two groups, proximal with thick spinulae, distal thin spinulae; outer pecten armed with thin spinulae. Basal spines ( Fig. 9E ). Naked, distal about 0.22 of length of the postabdominal claw, proximal about 3.2 times shorter than distal one.

EPHIPPIAL FEMALE, EPHIPPIUM. Unknown.

Male

Unknown.

Remarks

Disparalona (M.) lucianae sp. nov. is differentiated from D. (D.) rostrata , D. (D.) leei , D. (D.) ikarus , and D. (D.) smirnovi by the presence of seta 3 on the IDL thick, hook-like and heavily chithinized ( Fig. 8A ). Disparalona (M.) lucianae sp. nov. can be easily distinguished from D. (M.) hamata , D. (M.) chappuisi and D. (M.) striatiodes because it has the distal portion of labral keel short and rounded. Disparalona (M.) lucianae sp. nov. can be distinguished from D. (M.) tenuispina sp. nov. because the latter has a rostrum markedly short and curved, and about 1.3 times as long as antennular body, proximal basal spine of postabdomninal claw about 3.2 times shorter than distal one. Regarding the limbs, D. (M.) lucianae sp. nov. differs from D. (M.) tenuispina sp. nov. in the morphology of seta 2 of IDL, length of stiff setae on endites of first limb, and length of seta 1 on the exopodite of fourth limb. Disparalona (M.) caudata has a large body and postabdomen compared to D. (M.) lucianae sp. nov. ( Smirnov 1996a, 1996b). Disparalona (M.) lucianae sp. nov. differs from the D. (M.) acutirostris in the morphology of rostrum ( Frey 1961) and from D. (M.) leptorhyncha in the morphology of habitus, postabdomen and limbs.

Distribution and biology

Disparalona (M.) lucianae sp. nov. is the most common species of the hamata -complex occurring in Brazil. This species can be found in lentic water bodies such as, reservoirs, floodplain environments, ponds, and shallow lakes. Disparalona (M.) lucianae sp. nov. is somewhat common in lotic systems.

Figures

Fig. 7. Disparalona (Mixopleuroxus) lucianae sp. nov., parthenogenetic female. A–B. Habitus. C. Ventral view of carapace. D–E. Ornamentation of carapace. F. Anterior portion of ventral margin of carapace. G. Middle portion of ventral margin of carapace. H. Posterior portion and posteroventral corner of carapace. I. Rostrum. J. Head shield. K. Main head pores. L. Labrum. M. Antennule. N. Antenna. Scale bars = 50 μm. Figs B, D–E were not scaled.

Fig. 8. Disparalona (Mixopleuroxus) lucianae sp. nov., parthenogenetic female. A. First limb. B. Idem, stiff setae. C. Second limb. D. Third limb. E. Idem, epipodite. F–G. Fourth limb. H. Idem, distal endite. I. Elements. J. Fifth limb. Scale bar = 50 μm.

Fig. 9. Disparalona (Mixopleuroxus) lucianae sp. nov., parthenogenetic female. A–E. Postabdomen. A. Lateral view. B–D. Marginal denticles. E. Dorsal view of postabdominal claw (separation between claws not represented). Scale bar = 50 μm. Figs C–D were not scaled.

Fig. 13. Pictorial key to separation of species of Disparalona Fryer, 1968 occurring in South America.