According to ^{Van Damme, Maiphae, and Sa-Ardrit (2013)}, the genus Karualona comprises 7 species: K. karua (King, 1853), K. muelleri (Richard, 1897), K. iberica (Alonso & Pretus, 1989), K. alsafadi (Dumont & Brancelj, 1994), K. penuelasi (^{Dumont & Silva-Briano, 2000}), K. socotrana (^{Dumont & Silva-Briano, 2000}), and K. serrulata (^{Van Damme et al., 2013}). Of these species, K. muelleri and K. penuelasi surely occur in the Neotropics, while the presumed records of K. karua are doubtful (^{Sinev & Hollwedel, 2005}). Apparently, more species of this genus are present in the tropics, but they are waiting for their formal description (^{Kotov, Van Damme, et al., 2013}).

The study of composition and distribution of the genus Karualona in Colombia is still lagging. Up to now, the single valid species known to exist in Colombia is K. muelleri (^{Fuentes, Zoppi-de Roa, Gámez, Morón, & López, 2012}). ^{Pearse (1916)} reported Alonella karua in the Magdalena Department, but this record probably refers to K. muelleri, K. penuelasi or an undescribed species. Since no figures or description were presented in Pearse's paper, the specific identity cannot be confirmed. A recent biological survey of the aquatic fauna of a swamp of southern Magdalena yielded 2 parthenogentic females of K. penuelasi (^{Dumont & Silva-Briano, 2000}), which was originally described from Peñuelas Dam, Aguascalientes, Mexico. This study reports the first Colombian record of K. penuelasi , and indicates an important expansion of the known distributional range of this species, from Central America to South America.

Samples were taken from the aquatic vegetation in Cerro de San Antonio Swamp, Magdalena Department (10°19′30″N, 74°52′05″W), Colombia in June 2004. Water samples were collected using a 65 L bucket. Samples were filtered with a standard zooplankton net (45 μm mesh) and preserved in 70% ethanol. The specimens were dissected and the taxonomically relevant appendages were mounted in semi-permanent slides that were deposited in the Museo de Colecciones Biológicas of the Universidad del Atlántico, Barranquilla-Atlántico, Colombia (UARC210M-UARC214M). The appendages were photographed using a Kodak Easy Share C140 digital camera adapted to a compound microscope. The specimens were measured in lateral position, from the head to the posterior margin of the valves. Identifications were according with ^{Dumont and Silva-Briano (2000)}, ^{Elías-Gutiérrez et al. (2008)} and ^{Van Damme et al. (2013)}.

Karualona penuelasi was found associated with the aquatic macrophyte Eichhornia crassipes (Mart.) Solms. The analyzed specimens showed the typical characteristics of K . penuelasi . Body oval (Fig. 1A); body length from head to posterior part of valve ranging from 0.25 to 0.28 mm (n = 2, mean = 0.27 mm); length:height ratio 1.4, sculpture of valve with 10 striae (Fig. 1A); postero-ventral corner of valve with 3-4 setules between each pair of denticles (Fig. 1B); 2 main head pores; connected, as the genus (Fig. 1C); antenna II with setal formula 0-1-3/0-0-3; all apical setae of antennal exopod of same thickness (Fig. 1D and E). Inner distal lobe (IDL) of trunk limb I with 3 setae; inner and outer setae of different size; outer distal lobe (ODL) of limb I with long seta (Fig. 1F); all scrapers on trunk of limb II with denticles of equal thickness (Fig. 2A); postabdomen robust, lateral fascicles thin, short; distal setules length of lateral fascicles of postabdomen/postabdominal claw base width ratio about 1.5 (Fig. 2B and C); postabdominal claw with fine pecten and small basal spine on base (Fig. 2D).

Figure 1 Karualona penuelasi, parthenogenetic female: (A) habitus; (B) posteroventral angle of valve; (C) head pores; (D) distal portion of the endopod and exopod of antenna; (E) antenna; (F) limb I. 

Figure 2 Karualona penuelasi, parthenogenetic female: (A) limb II; (B) postabdomen; (C) lateral fascicles of postabdomen; (D) postadbominal claw. 

Karualona penuelasi is considered as a Neotropical species (^{Dumont & Silva-Briano, 2000}; ^{Kotov, Forró, Korovchinsky, & Petrusek, 2013}; Van Damme et al., 2013) and most closely resembles K. muelleri and K. karua in the body shape and valve sculpture, but these species can be separated by the following characters: (1) setae on the antennal exopod are of the same thickness in K . penuelasi and K. karua (^{Dumont & Silva-Briano, 2000}; figs. 2 and 3) while in K. muelleri the longest seta is thicker than the others (^{Sinev & Hollwedel, 2005}; fig. 19); (2) lateral fascicles of postabdomen are thin and short in K . penuelasi (^{Dumont & Silva-Briano, 2000}; fig. 15-2, present paper, Fig. 2C) while in K. muelleri and K. karua they are thick and long (^{Sinev & Hollwedel, 2005}; figs. 20-22; ^{Dumont & Silva-Briano, 2000}; fig. 15-5); (3) length of distal setules in lateral fascicles located on the postabdomen/diameter of postabdominal claw base ratio about 1.5 in K. penuelasi (^{Dumont & Silva-Briano, 2000}; fig. 15-2, present paper, Fig. 2C) while in K. muelleri and K. karua about 2 (^{Sinev & Hollwedel, 2005}; figs. 20-22; ^{Dumont & Silva-Briano, 2000}; fig. 15-5); (4) outer and inner setae of IDL of limb I of different size in K. penuelasi and K. karua (^{Dumont & Silva-Briano, 2000}; fig. 6-2; 6-3, present paper, Fig. 1F) while in K . muelleri both setae are of the same size (^{Sinev & Hollwedel, 2005}; fig. 25); (5) all scrapers of limb II with denticles of equal thickness in K. penuelasi and K. karua (^{Dumont & Silva-Briano, 2000}; figs. 9-2, 9-3, present paper, Fig. 2A) while in K. muelleri scrapers 3 and 6 present more robust denticles (^{Sinev & Hollwedel, 2005}; fig. 26); (6) length of scrapers 1 and 2 of limb II of the same size in K. penuelasi and K. muelleri (^{Dumont & Silva-Briano, 2000}; fig. 9-3; ^{Sinev & Hollwedel, 2005}; fig. 26; present paper, Fig. 2A) of different in size in K. karua (^{Dumont & Silva-Briano, 2000}; fig. 9-2); (7) postero-ventral corner of valve with 1-4 setules between each pair of denticles in K. penuelasi (^{Dumont & Silva-Briano, 2000}; fig. 5-1, ^{Sinev & Hollwedel, 2005}: 100; present paper, Fig. 1B), 5-7 in K. muelleri (^{Sinev & Hollwedel, 2005}; fig. 17) and 4 in K. karua (^{Dumont & Silva-Briano, 2000}; fig. 5-2).

In the surveyed area, K. penuelasi was found associated to the aquatic vegetation, where water temperature was 32.6 °C, conductivity 260 μS m⁻¹, total dissolved solids 120, and pH 8.4. The presence of K. penuelasi in nearby waters seems very likely, so a wider distribution in South America might be expected.

We are very grateful to Dr. Silva-Briano and Dr. Sinev Artem for their valuable consultations. This study was financially supported by the Fundación para la Participación, Capacitación y la Investigación Social "FUPARCIS".