New records of Coronatella (Crustacea, Branchiopoda, Chydoridae) from Colombia with the first report of Coronatella undata and of the male of Coronatella monacantha

Biological samples obtained from a small temporary pond of northern Colombia yielded the first record Coronatella undata Sousa, Elmoor-Loureiro and Santos, 2015 and of the male of C. monacantha (Sars, 1901) for Colombia. In this study, the morphology of female of Coronatella undata and female and male of C. monacantha was described and compared to other species within the genus. C. undata was originally described from Brazil and, among the species of the Coronatella monacantha complex, seems to be closely related to C. acuticostata (Sars, 1903). C. undata shows some similarities with C. monacantha, but it can be identified by important diagnostic characters such as: 1) posterior-ventral corner of valve with two denticles, 2) seta on exopodite of trunk limb II rudimentary, 3) filter comb of trunk limb II with six setae, 4) ODL seta of trunk limb I shorter than longest seta of IDL. C. monacantha is the most reported species in the Neotropical region and the male most resemble C. paulinae Sousa, Elmoor- Loureiro & Santos, 2015 in relation to (i), length/wide of postabdomen ratio (ii) basal spine almost straight and (iii)) long basal spine reaching the mid-length of basal spine. However, they can be separated by (i) number of lateral seta on the antennule, (ii) postanal angle, (iii) position of gonopore (iv) presence of a denticle on posterior-ventral corner of valve

vegetation (macrophytes). Environmental parameters were measured with a WTW 3111 conductivity meter gear. Biological samples were taken with a 25 L bucket within the vegetation area until filtering 175 L. Samples were filtered with a zooplankton net (mesh size 55 μm) and then preserved in 96% ethanol with previous addition of carbon dioxide from soda water as narcotic.
In the laboratory, samples were stained with Bengal rose and concentrated to 50 mL volume. A Bogorov chamber was used to sort and count cladocerans, with the aid of a stereomicroscope and then processed for taxonomical identification. Specimens were measured in lateral position, from the anterior end of the head to the posterior margin of carapace, and dissected to examine the taxonomically relevant appendages. Dissected specimens and appendages were mounted in glycerine and sealed with Canada balsam. The appendages with taxonomic relevance were photographed using a Kodak Easy Share C140 digital camera adapted to a compound microscope at 1000× magnification. Identifications of these species were made according to Sinev (2004) and Sousa et al. (2015Sousa et al. ( , 2016b. The dissected animals (slides) were deposited at the Centro de Colecciones Biológicas held at the Universidad del Magdalena, Colombia (CBUMAG) where they are available for consultation and/ for further examination.

Diagnosis parthenogenetic female
The specimens from Colombia share the diagnostic features from specimens of Coronatella undata previously reported from Brazil (Sousa et al., 2015). Body ovalrectangular ( Figure 1A), small animal-sized, with length ranging 224-249 μm (n =2, average = 236 μm), length /height ratio about 1.44. Valves arched anteriorly and striated, posteroventral corner with two denticles ( Figure 1G), followed by spinules not arranged in groups. Rostrum short, blunt and projected downward, ocellus smaller than eye, antennules not exceeding the tip of rostrum ( Figure 1B). Head shield with three main connected head pores, middle one being the smallest ( Figure 1C); IP/PP ratio
The genus Coronatella has a worldwide distribution (Sinev, 2020) with records in Africa, Asia, South America, Central America, North America, and Europe (Van Damme and Dumont, 2008b;Van Damme et al., 2010;Van Damme, 2016). Members of this genus inhabits chiefly all type of freshwater bodies, such as: lakes, rivers, swamps, temporary ponds (Fuentes-Reinés and Zoppi de Roa, 2013;Sousa et al., 2015), and some species -e.g. C. rectangulacan tolerate a wide range of salinity and C. salina Alonso, 1996 is adapted to saline to hyperhaline waters (Van Damme and Dumont, 2008a;Sinev et al., 2009;Sinev, 2020). Further advances on the systematics of the genus led Sinev (2020) to divide it in two subgenera: Coronatella s. str. and Coronatella (Ephemeralona), and he recognized distinct species-groups in the former subgenus such as: monacantha-group, and circumfimbriata-group, rectangulagroup and trachystriata-group.
During a survey of the plankton community of a temporary pond at Pivijay, Magdalena-Colombia, were collected specimens of Coronatella monacantha and C. undata. In this work, we report for the first time the occurrence of C. undata for Colombia and expand the characterization of C. monacantha, providing the description of the male. Moreover, we present a brief diagnosis of the parthenogenetic females in order to support the identification of found specimens.
Postabdominal claw about 1.66 longer than the anal margin, basal spine about two times as long as claw width at base, reaching half of postabdominal claw length ( Figure 2B). IDL of trunk limb I with two unequal setae armed with strong and long spines ( Figure 2C). ODL with a seta shorter than longest IDL seta ( Figure 2C). Trunk limb II with a rudimentary seta on exopodite (arrow, Figure 2D), inner portion with eight scrapers gradually decreasing in size towards gnathobase, eighth scraper shortest, gnathobase with three modified elements, filter comb with six setae, the first one shorter than the other ( Figure 2D).
Morphological variability: One female presented a notch at the apex of the labrum ( Figure 1E

Diagnosis of parthenogenetic female
Body oval-rectangular ( Figure 3A), small animal-sized, body length ranging 252-280 μm (n =5, average = 268 μm). Body 1.5 times as long as high. Valves arched anteriorly and striated, posteroventral corner with one denticle ( Figure 3D), followed anteriorly by spinules arranged in groups. Head shield with three main connected head pores, the middle one being the smallest ( Figure 3B); IP/PP ratio about 2.1. Labrum triangular, labral keel with tiny denticle ( Figure 3C). Rostrum, antennule and antenna as C. undata. Postabdomen short, length/ height ratio about 2.4 times ( Figure 3E), preanal margin about 1.95 longer than both anal and postanal margin respectively; postanal part with 7 denticles and 6-8 lateral fascicules. Postabdominal claw about 1.5 longer than the anal margin, base armed with setules; basal spines about two times as long as claw width at base, reaching half of postabdominal claw length ( Figure 3F). IDL of trunk limb I with two unequal setae armed with strong and long spines ( Figure 3G). ODL with a seta longer than longest IDL seta ( Figure 3G). Exopodite of trunk limb II with a seta about 1/3 of the exopodite length  Figure 3H); inner margin as in C. undata; gnathobase with three modified elements, filter comb with seven setae, the first one being the shortest ( Figure 3I).
Morphological variability: One female showed a notch on labral keel, at 1/3 from the apex (arrow in Figure 3C).

Description of male
Habitus. Body rectangular, smaller than female ( Figure 4A), total length 224 μm (n = 2). Rostrum as in female, ocellus 1.6 larger than the eye. Carapace with striation, postero-ventral corner of the valves as in females, with a denticle ( Figure 4D). Antennules not exceeding the tip of the rostrum ( Figure 4A), with nine aesthetascs of different length at the apical margin (four aesthetascs were not illustrated), with two lateral sensory setae; antennule of one male carries a short seta inserted at the distal third of the inner margin ( Figure 4B). Antenna as in female. Labrum triangular shaped, labral keel with a tiny ventral corner of valve not arranged in group in C. undata (Sousa et al., 2015, figs 9; present data, fig. 1G) vs. the opposite condition is presented in C. monacantha (Sinev, 2004, figs. 5, 6), 6) labral keel often with denticles in C. monacantha (Sinev, 2004, fig. 11, Fuentes-Reinés andZoppi de Roa, 2013, fig. 12B, Sousa et al., 2015, figs. 11E, F) whereas in C. undata without denticles (Sousa et al., 2015, figs. 9G, H, present data, figs. 1D,E) Coronatella undata can be easily identified by its important diagnostic characters such as: 1) posterior-ventral corner of valve with two denticles, 2) exopodite of trunk limb II with rudimentary seta, 3) filter comb of trunk limb II with six setae, 4) seta of ODL of trunk limb I shorter than the longest seta of IDL. These distinctive traits are present in the specimens from Colombia. However some subtle differences were observed in our specimens, 1) length ratio of spine on first endopodal segment/second endopodal segment about 1.4 in the Colombia specimens vs. 1.3 in the Brazilian populations (Sousa et al., 2015, fig . 9J), 2) labral keel not wavy in the Colombia specimens vs. wavy in Brazilian populations (Sousa et al., 2015, figs. 9G, H), 3) length ratio IP/PP about 2.0-3.6 in Brazilian populations vs 3.1 in Colombian specimens. Coronatella constitutes a genus in which are frequent intra-(e.g., C. anemae) as well as interspecific (e.g., C. holdeni) morphological variability (Van Damme and Dumont, 2008b), therefore, we do not consider such differences as signs of a separate status of the Colombia populations.
C. monacantha seems to be the most reported species of the genus in the Neotropical region since it has been recorded in Colombia (Fuentes-Reinés and Zoppi de Roa, 2013, present data), Brazil (Sousa et al., 2015), Argentina and Paraguay (Debastiani-Júnior et al., 2015). Some morphological variability has been reported for this species, such as the labrum with or without denticle, the size of denticle on the posteroventral corner of the valve, size of limb V, position of the lateral head pores (Sinev, 2004;Sousa et al., 2015). Nevertheless, there are some consistent characters that can be useful and easy to identify in parthenogenetic females of C. monacantha, such as: (i) the presence of a denticle on the posteroventral corner of the valve, (ii) ODL seta longer than longest IDL seta, and (iii) exopodite length seta ratio about 1/3 the length of exopodite itself and (iv) PP/IP ratio about 2-2.1 Among the males of subgenus Coronatella, C. monacantha most resemble C. paulinae when observing (i), the radio length/wide of the postabdomen (ii) basal spine almost straight and (iii)) length of basal spine reaching the midlength of postabdominal claw. However, they can be separated by (i) antennule with one lateral seta in C. paulinae (Sousa et al., 2016a, fig. 3) vs. two setae in C. monacantha (present data, fig 4B), (ii) postanal angle well expressed or defined in C. paulinae (Sousa et al., 2016a, figs 5, 6) vs. not expressed in C. monacantha (present data, fig 4E), (iii) gonopores opened in ventral base of postabdominal claws in C. monacantha (Present data, Fig. 4E), whereas in C. paulinae the gonopores are located far from the base (Sousa et al., 2016a, Fig 5, 6), and (iv) posterior-ventral of valve without denticle in C. paulinae (Sousa et al., 2016a, fig. 2) vs. with one denticle in C. monacantha (present data, Fig 4D). Comparison with other known males of subgenus Coronatella, see Table 1. denticle ( Figure 4C). Postabdomen smaller than female ( Figure 4E), tapering distally, about 2.26 times as long as height; preanal angle well defined, anal margin two times longer than postanal margin; postanal margin armed with small distal setulae ( Figure 4F) and six small groups of fascicles. Postabdominal claw long ( Figures 4E, 4F), about 2 times as long as the basal spine and as long as the anal margin; basal spines slender and slightly curved near the tip ( Figure 4F), longer than the mid-length of the postabdominal claw; gonopores situated ventrally to the postabdominal claw base.
Trunk limb I ( Figure 4G), proportionally smaller than on female, copulatory hook U-shaped, arms relatively similar in length, copulatory brush present, IDL with two setae (2-3) of different length and armed with short spines; male seta similar in length to the smallest IDL seta; ODL seta about 1.5 longer than IDL seta.

Discussion
Coronatella undata is included in the subgenus Coronatella and belongs to the C. monacantha-complex which comprises at least another Neotropical species (i.e., C. monacantha Sars, 1901), one Afrotropical (C. hadingi, Brehm, 1957) and one Oriental species (C. acuticostata Sars, 1903) (Van Damme, 2016). Among the species of the Coronatella monacantha complex, C. undata seems to be closely related to C. acuticostata sharing the presence of two denticles on posterior-ventral corner of the valve, ODL seta shorter than longest IDL seta, and similar length of the basal spine, but they can be separated by (i) labral keel with denticle in C. acutiscostata while in C. undata without denticle, (ii) shorter IDL seta with two thin spines in C. acutiscostata vs. three thick spines in C. undata, (iii) and postanal margin wider in C. undata than in C. acutiscostata.
Cladocerans are microcrustaceans that exhibit a wide range of plasticity (Miyakawa et al., 2013), therefore, it is not surprising the high variability observed in morphological structures in the genus Coronatella. Hence, their identification is not an easy task, likewise, some members of this group can form species complexes -e.g., rectangula group-complex, monocantha group-complex, etc. -that make more difficult the identification. However, the Coronatela male provides important characters -e.g.
The genus Coronatella seems close to genera Anthalona Van Damme, Sinev & Dumont, 2011 and Magnospina Sousa, Elmoor-Loureiro & Santos, sharing a similar postabdomen and in the reduction of the limbs (Van Damme andDumont, 2008b, Van Damme et al., 2011). When comparing the male of C. monacantha with the males of the latter genera, they are also alike by possessing a naked male seta and two modified setae on the IDL of limb I; nevertheless they differ by (i) antennules with two lateral setae in C. monacantha (present data, fig. 4B) and Magnospina (Sousa et al., 2016b, Fig 28) vs. one lateral seta in Anthalona (Alonso, 1996, Fig 141O, Sinev and Hollwedel, 2002, Fig. 10, Van Damme et al., 2011 . 15D), (ii) basal spine long, about half-length of postabdominal claw in C. monacantha the postabdomen-which is a potential structure that allow to distinguish among Coronatella species (Sousa et al., 2015). This fact has also been observed in others group of cladocerans (Korovchinsky andSheveleva, 2009, Kotov andFuentes-Reinés, 2015;Kotov, 2015). Such morphological variabilities in microcrustaceans have been few investigated (Korovchinsky, 1997). In cladocerans, these variations have been associated with abiotic and biotic factors (Havens and Beaver, 2011). However, these factors have not been properly researched (Sousa et al., 2011).
The values of environmental variables measured in the temporary pond of Pivijay, suggest that this waterbody presents eutrophic conditions. This fact could possibly be influencing the cladoceran populations. An eutrophic waterbody could induce morphological changes in cladocerans. For instance, it has been observed in Bosmina freyi a wide variation in body size and length of antennules and mucron probably due to abiotic factors like both high temperature and concentration of nutrients (López-Cardona et al., 2021), but further research should be done in order to clarify this statement.