Disparalona cf. hamata ( Birge, 1879 )

Disparalona cf. hamata ( Birge, 1879) View in CoL

Material examined. 1 adult female, catalog number:

UARC321 M– UARC 325M.

Remarks. Eight valid species of the genus Disparolona have been described worldwide: Disparolona rostrata (Koch, 1841) , Disparolona acutirostris ( Birge, 1879) ; D. hamata ; Disparolona leei (Chien Shing-ming, 1970); Disparolona caudata Smirnov, 1996 ; Disparolona leptorhyncha Smirnov, 1996 ; Disparolona ikarus Kotov and Sinev, 2011 and Disparolona smirnovi Klimovsky, 2015 . Of these, D. leptorhyncha and D. hamata have been recorded in the Neotropics, and the la er was originally described as Pleuroxus hamatus by Birge (1879) from North America; however, Smirnov (1996) allocated the species to the genus Disparalona .

e specimen from Colombia has an elongated body, and the posterior portion of body is remarkable lower than the anterior ( Fig. 3E), short rostrum ( Fig. 3F), and valve with ne striae (arrowed in Fig. 4A). Antenna of moderate size ( Fig. 4B), the proximal segments of each branch are twice as long as and more massive than the other two, antennal formula: setae 0-0-3/0-1-3, rst endopodal segment with a small spine (arrowed in Fig. 4B). Keel not prominent, distal portion short and rounded. Postabdomen about 3.4 times as long as wide, with preanal angle not prominent ( Fig. 4C); postabdominal claw with two basal spines, the distal about 0.25 the length of the claw and the proximal two times shorter than the proximal one ( Fig. 4D). IDL of limb I with three setae, the seta 3 is hook-like ( Fig. 4E, F), ODL with one long and one short accessory seta, the outer one very short ( Fig. 4E) which was variable in size (arrowed in Fig. 4F). Limb II with eight scrapers, the seta of exopodite is longer than scrapers 8, 7, 6 and 4 ( Fig. 5A). Exopodite of limb III is rectangular, with two lateral setae (5– 6) and four distal setae (1–4) ( Fig. 5B); seta 7 was not observed and, taking into account that only one specimen was examined, it is probable that it could be due to variability or it could have been broken. Nevertheless, more specimens should be examined and observed to con rm it. e exopodite of limb IV is oval with seven setae (1–7) ( Fig. 5C). Epipodite of limb V ovoid; exopodite with two hillocks densely setulated near the inner limb portion (arrowed in Fig. 5E) and a single distal (1) and three lateral (2–4) setae ( Fig. 5D, E); inner limb portion elongated ( Fig. 5F), with setulated inner margin, with two setae of equal size; lter comb with three setae.

e specimen from Colombia bears the diagnostic features of D. hamata reported by the authors based on the study of material from Venezuela, Brazil, Sudan and Mali ( Rey and Vásquez, 1986; Zoppi de Roa and Vásquez, 1991; Smirnov, 1996; Elmoor-Loureiro, 1997). However, some subtle differences can be observed in our specimen: (1) the outer small seta of the ODL of limb I is absent in gures of specimens from Venezuela ( Rey and Vásquez, 1986, pl. V, g. 14; Zoppi de Roa and Vásquez, 1991, g. 10B), whereas it is present in populations from Colombia (present data, Fig. 4D, E); (2) the exopodite of limb IV bears seven setae in specimens from Colombia (present data, Fig. 5B), whereas populations from Venezuela have six (Zoppi de Roa and Vásquez, 1991, g. 10I), and probably these two structures were overlooked in specimens from Venezuela owing to their size. Unfortunately, Smirnov (1996) and Elmoor-Loureiro (1997) did not illustrate these structures, making comparisons impossible.

Disparalona hamata View in CoL has been poorly described ( Birge, 1879; Rey and Vásquez, 1986; Zoppi de Roa and Vásquez, 1991; Smirnov, 1996; Elmoor-Loureiro, 1997; Kotov et al., 2012), and a detailed redescription is required. Bearing in mind the non-cosmopolitanism concept ( Frey, 1982) and the type locality of D. hamata View in CoL in North America, specimens from South America may be a new taxon.

In the Neotropical region, D. hamata View in CoL can be easily separated from D. leptorhyncha by the following characteristics: (1) the rostrum is longer in D. leptorhyncha (see Smirnov, 1996, gs. 309, 310; Van Damme and Dumont, 2010, g. 9A) than in D. hamata View in CoL (see Birge, 1879, g. 13; Smirnov, 1996, g. 296; Flössner, 2000, as Alonella hamulata ( Birge, 1910) , g. 106A; present data, Fig. 3F); (2) seta III on the IDL of limb I is thicker in D. hamata View in CoL (see Smirnov, 1996, g. 300; Flössner, 2000, as Alonella hamulata , g. 106G; present data, Fig. 4D, E) than in D. leptorhyncha (see Smirnov, 1996, g. 319; Van Damme and Dumont, 2010, g. 9f).

Distribution. It has a wide distribution and is a complex of species with, probably, local endemism. D.hamata has been reported in Afrotropical, Nearctic, Neotropical, Palaearctic, and Oriental regions ( Kotov et al., 2013). Nevertheless, the Oriental population could be a new species ( Sinev and Sanoamuang, 2011); therefore, further analysis of D. hamata is required.

Ecology. e surveyed area was dominated by Campsiandra comosa , which is one of the typical plants of the zone. Cladocerans were most numerous in habitats associated with the roots of plants. e water temperature during sampling was 30.2°C, conductivity 6.7 S.cm –1 value, pH 6.6, and dissolved oxygen 8.2 mg /L.