New records of Cladocera ( Crustacea : Branchiopoda ) from the Tomo River , Vichada , Colombia

Five species of cladocerans are reported from the Tomo River, Vichada, Colombia. Zooplankton samples were collected from the li oral zone with vegetation (Campsiandra comosa Benth). ree of them, namely Streblocerus pygmaeus Sars, 1901, Disparalona cf. hamata (Birge, 1879) and Alona isabellae Sousa, Elmoor-Loureiro and Santos, 2016 are new to the Colombian cladoceran fauna. Descriptive notes, comparative comments on morphology and variability and illustrations are also provided for some remarkable taxa. is is the rst report on the cladoceran fauna in the Tomo River.


INTRODUCTION
Cladocera is one of the main zooplankton groups which inhabits fresh, brackish and marine water (Alonso, 1996;Fuentes-Reinés et al., 2012); most of them occur in freshwater and associated with vegetation (macrophytes), but some taxa can be found in open water (Fuentes-Reinés et al., 2012).

Cladocera from Vichada
Nauplius, 26: e2018006 Fuentes-Reinés (2015b) reported 101 valid species of Cladocera for Colombia; nevertheless, this number could increase because only 19 departments among 31 have records of this group.
During the scienti c expedition "Vichada BIO" in 2017, some zooplankton samples were taken in the lower part of the Tomo River, located in the Orinoco region.e Tomo River is a tributary of the Orinoco River; the head of the river is located in the Meta department and crosses the Vichada department.Hitherto, there have been no single records of cladocerans in this system.
Based on samples collected from li oral habitats, we found several interesting taxa of Cladocera dwelling in the Tomo River.Descriptive notes, comparative comments on morphology and variability, and illustrations are also provided for some remarkable taxa. is work contributes to increasing the knowledge of this group in Colombia and the Neotropical region.

MATERIAL AND METHODS
Four samples were collected in the li oral zone among the roots of Campsiandra comosa Benth in the lower part of the Tomo River (05°48'02.5"N68°13'19.8"W), in April 2017.Water pH and temperature were measured with a multiparameter WTW 350i.Two hundred and eighty-eight (288) liters of water were taken using a 25-L bucket, then ltered through a zooplankton net (45 μm) and preserved in 70% ethanol.Samples were stained with bengal rose.
e ltered samples were concentrated to 50 ml and, with a Bogorov counting chamber, cladocerans were sorted and the obtained specimens were measured in lateral position from the anterior-most extremity of the rostral area to the posterior margin of the valve.Cladocerans were dissected and their appendages were mounted on slides with glycerin and sealed with Canada balsam; then, appendages were photographed using a Kodak Easy Share C140 digital camera adapted to a compound microscope.e specimens examined were deposited at the Museo de Colecciones Biológicas de la Universidad del Atlántico, Barranquilla-Atlántico, Colombia (Universidad del Atlántico Región Caribe -UARC), where they are available for consultation and/ or further examination.e identi cation of the species followed Smirnov (1992;1996), Fuentes-Reinés et al. (2012), and Sousa et al. (2016).

RESULTS
e taxonomic analysis of the cladoceran specimens collected yielded the identi cation of ve species belonging to two families and ve genera.e family Chydoridae showed the highest species richness (3) (Tab.1).ese are all new records for the Tomo River.Brief remarks, descriptions and illustrations about the relevant species are given below.Remarks.Macrothrix spinosa was the least abundant species among Macrothricidae in the samples and was originally described from Australia by King (1853).It is similar to its Neotropical congener M. squamosa; therefore, the la er species was accepted as a synonym of M. spinosa. is synonymy is based on the similarity of general characteristics, for example the general aspect of the valve, antennule, and postabdomen (Elmoor-Loureiro, 2007).Taking into consideration the concept of non-cosmopolitanism in cladocerans given by Frey (1982), it is possible that M. spinosa and M. squamosa constitute separate species; nevertheless, an exhaustive revision is required.

Family
Machrotrix spinosa is easily identi able by its oval body, antennule dilating distally, and the serrations along the dorsal part of the valve (see Fuentes-Reinés and Elmoor-Loureiro, 2015b).
Distribution.It occurs in the tropical and subtropical territories of the world (Smirnov, 1992); it seems to have a broad distribution in Colombia, and is recorded in the Caribbean region (Kotov and Fuentes-Reinés, 2015b). is is the rst record from the Orinoco region.
Remarks.It was one of the most abundant species in the samples.Its body is globular in lateral view, with convolute intestine (Fig. 1A) and divergent antennules (Fig. 1B).It can be di erentiated from its congeners by the postabdomen, which bears setae in the preanal marginal portion (Fig. 1C) instead of spines; these setae form distinct groups (Fig. 1D), as observed also in populations from Mexico, the U.S.A. and Brazil (Smirnov, 1992;Gar a-Espejo and Elías-Gutierrez, 2003), although they are not grouped in the population from the Nhamundá River (Smirnov, 1992).Body length is between 0.21 and 22 mm, average: 0.22 mm (n = 5).
Distribution.It has been recorded in the Neotropical, Nearctic and Oriental regions (Kotov et al., 2013); nevertheless, the population from China recorded by Chian and Du (1979) is considered to be a doubtful identi cation (Smirnov, 1992).is is the rst record from the Orinoco region and Colombia.Remarks.Alona isabellae was originally described by Sousa et al. (2016) based on specimens previously identi ed as Alona intermedia Sars, 1862 in Brazil (see Sousa et al., 2016).Its body is oval (Fig. 1E), maximum height at middle of body, body height/ length ratio about 0.63 µm, body length = 0.27 mm, average: 0.27 mm (n = 2), head with two major pores connected (Fig. 1F), postabdomen about 2.6 times as long as wide (Fig. 2A), with nine lateral fascicles and ten postanal marginal denticles.IDL and ODL

Cladocera from Vichada
Nauplius, 26: e2018006 Alona isabellae can be easily separated from other members of the Alona intermedia-group by the peculiarities of the spinule of distalmost fascicles, which is thicker than the others and goes beyond the postabdomen margin and the marginal denticles (arrowed in Fig. 2A, B).Another important diagnostic feature is the labrum with two short and ne spinules on the anterior margin and a cluster of setules on the posterior margin (Fig. 2C).ese two distinctive

Cladocera from Vichada
Nauplius, 26: e2018006 e specimens from Colombia have diagnostic features of A. isabellae as described by Sousa et al. (2016).ere are, however, some small di erences in our specimens: (1) proximal and distal denticles of the postabdomen with ne spinules in the populations from Brazil (Sousa et al., 2016, fig. 7O), while in Colombian populations this structure is only absent in distal denticles (Fig. 2B, present data); (2) scraper 4 and 5 of limb II di erent in length in specimens from Colombia (Fig. 2D), while they are of the same size in Brazilian populations (Sousa et al., 2016, g. 8F).

Cladocera from Vichada
Nauplius, 26: e2018006 Overall, these di erences are deemed to be intraspeci c variations and thus expand the knowledge on the morphometric variability of this species.
Distribution.Alona isabellae is so far known only from Brazil (Sousa et al., 2016) and Colombia (present study).Some records of A. intermedia have been recorded from Venezuela, Peru, and Paraguay (Daday, 1905;Stingelin, 1906;Delachaux, 1918;Rey and Vazquez, 1986), and these reports could correspond to A. isabellae or to a new species; nevertheless, an exhaustive review of these records is required.

Cladocera from Vichada
Nauplius, 26: e2018006 Remarks.e specimens from Colombia share the diagnostic features of A. dadayi previously reported
Distribution. is species has been recorded from the North to South America (Smirnov, 1996;Van Damme and Dumont, 2010).In Colombia, A. dadayi has been reported in Caribbean and Andean regions (Kotov and Fuentes-Reinés, 2015b). is is the rst record for the Orinoco region.
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.
In the Neotropical region, D. hamata 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
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 μS.cm -1 value, pH 6.6, and dissolved oxygen 8.2 mg/L.

DISCUSSION
Following Kotov and Fuentes-Reinés (2015b), Sinev and Fuentes-Reinés (2016) and the information presented in this study, the total number of cladocerans for Colombia has increased to 105 valid species.Keeping in mind these new records, the number of species belonging to the genera Alona and Stroblocerus increased to eight and two, respectively, whereas the genus Disparalona is recorded for the rst time from Colombia.In Colombia, the records of cladocerans in rivers are non-existent, which is probably due to insu cient e orts in cladoceran research, sampling difficulties, and taxonomical problems.This is in contrast to Brazil and Argentina, where some studies on cladoceran fauna have been carried out in a riverine environment (Paggi, 1992;Sera m Jr. et al., 2003;Sera m-Júnior et al., 2006;Sousa and Elmoor-Loureiro, 2012).Hitherto, we recorded five new species from the Vichada Department and three from Colombia (see Tab. 1).e richness and abundance of microcrustacean taxa were lower than expected, probably because the samples were taken only from a small part of the river and did not reach rare species.In Chydoridae and Macrothricidae, the richness is always in uenced by rare species, but on the other hand only one substrate (roots of Campsiandra comosa) was sampled.Most cladocerans, especially the family Chydoridae, are associated with macrophytes (Fuentes-Reinés et al., 2012).We expect that this manuscript will motivate an increase in the studies on riverine cladoceran fauna, supported by a strong taxonomic base, leading to new records and, consequently, to a be er comprehension of the Colombian diversity of freshwater microcrustaceans.

Figure 2 .
Figure 2. Alona isabellae Sousa, Elmoor-Loureiro and Santos, 2016, adult female from the Tomo River.A, Postabdomen; B, distal portion of postabdomen; C, labrum; D, limb II.Alonella dadayi Birge, 1910, adult female.E, Adult; F, head pores.characters are present in the Colombian specimens.especimens from Colombia have diagnostic features of A. isabellae as described bySousa et al. (2016).ere are, however, some small di erences in our specimens: (1) proximal and distal denticles of the postabdomen with ne spinules in the populations