Coronatella (Coronatella) jimenezae, Sousa & Fuentes-Reinés & Vásquez-Ramos & Eslava-Eljaieka & Elmoor-Loureiro, 2025

Coronatella (Coronatella) jimenezae sp. nov.

( Figs. 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 )

Etymology. The new species is dedicated to biologist Yaqueline Jiménez Moreno†, who was a passionate zooplankton researcher, and her love for science inspired those who had the privilege to know her.

Type locality. La Española fluvial lake, Meta department, Colombia (4°20’36.6”N, 72°03’35.2” W) GoogleMaps .

Material examined. 20 parthenogenetic females, 3 adult males and 1 juvenile male collected in November of 2022 by J. M. Vásquez-Ramos.

Type material. Holotype. Adult parthenogenetic female deposited in a tube with ethanol at the collection of Museo de Historia Natural Unillanos, Colombia, under access number: MHNU-P038 .

Allotype. Adult male from type locality deposited in ethanol at the collection of Museo de Historia Natural Unillanos. Access number: MHNU-P039 .

Paratypes. Eigth undissected parthenogenetic females in ethanol, MHNU-P040 . One dissected male in ethanol, MHNU-P041-1 . One dissected adult male, one undissected adult male, six dissected adult females and six undissected adult females ( JF-R); one adult male and four adult parthenogenetic females in ethanol ( FDRS0816 ) .

Description. Parthenogenetic female ( Figs. 1–2–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 ). General ( Fig. 1A View FIGURE 1 ). Body ovoid in lateral view and laterally compressed in anterior view, without lateral projections, dorsal keel moderate. Length ranging between 0.28–0.36 mm, height/length ratio about 0.5–0.6.

Carapace ( Fig. 1A–D View FIGURE 1 ). With at least 20 longitudinal lines on valves. Ventral margin with 32–34 setae not reaching the end of ventral margin, organized in three groups; anterior and posterior groups with setae longer than those in median group ( Fig. 1C–D View FIGURE 1 ); spinules not arranged into groups and not exceeding the marginal line present ( Fig. 1D View FIGURE 1 ). Posteroventral corner without denticles. Posterior margin of valve slightly undulated.

Cephalic structures ( Fig. 1E–I View FIGURE 1 ). Ocellus as large as eye. Rostrum ( Fig. 1E View FIGURE 1 ) relatively long, blunt, projected downward. Head pores ( Fig. 1F View FIGURE 1 ); three main head pores connected by narrow connection, median pore smaller than proximal and distal pores, PP/IP about 1.5; lateral head pores tiny, inserted at same level as the median pore.

Labrum ( Fig. 1E View FIGURE 1 ) with keel wide in lateral view, relatively short, naked, rounded apex.

Antenna I ( Fig. 1G View FIGURE 1 ) about 2.4 times longer than wide, with three long rows of setulae on the antennular body, never extending beyond the tip of the rostrum; antennular sensory seta slender, about 2.5–2.7 times shorter than the length of the antennular body, inserted at 2/3 of antennular body; nine terminal aesthetascs of different sizes not exceeding the length of the antennular body.

Antenna II ( Fig. 1H View FIGURE 1 ) with basipodite thick, with a short spine; branches of similar length; spine on the first exopodite segment longer than segment itself; spine on the third exopodite segment about two times longer than segment itself; first endopodite segment with a single row of long setulae close to the base, armed with a thin apical seta; second endopodite segment bearing a single row of setulae near apical part, armed with a bisegmented seta about 1.3 times longer than branch length. Antennal formula (exo/endo): spines 101/001, setae 003/113.

Maxilla ( Fig. 1I View FIGURE 1 ) well developed, with two long setulated setae.

Thoracic limbs: five pairs ( Figs 2A–I View FIGURE 2 ).

Limb I ( Fig. 2A–B View FIGURE 2 ). Epipodite with a long projection. ODL seta bisegmented, armed with fine and short spinelike setulae, similar in length to IDL third seta; accessory seta not found. IDL (en4) with two groups of short setulae on the corm, two setae present: seta 2 about 1.4 times shorter than seta 3, setae 2 and 3 armed with strong and relatively long proximal spines; basalmost spines about two times greater than the width of the base of the respective setae. Endite 3 with four setae; anterior seta 1 about 1.2 times shorter than posterior seta (c); posterior setae (a–b) of similar length among themselves, slightly longer than the anterior seta 1; seta (c) longer than the setae (a–b). Endite 2 with three posterior setae present (d–f); seta (d) armed with short setulae, about 2.2 times shorter than the seta (e); seta (e) long, armed with thick spinules on lateral face; seta (f) armed with thick spinules on lateral face, about 1.9 times longer than seta (d) and 1.2 times shorter than seta (e). Endite 1 with three posterior setae (g–i); setae (g–h) of similar length, bisegmented and slightly setulated; seta (i) about 1.3 times shorter than setae (g–h). Ejector hooks of different length. Ventral face of limb with 6–8 clusters, decreasing in length toward distal portion. Gnathobase not studied.

Limb II ( Fig. 2C View FIGURE 2 ). Exopodite without setae, armed with a row of setulae. Inner limb portion with eight scrapers; scraper 1 slightly longer than scraper 2; scraper 3 slightly longer than scraper 4, about 1.4 times shorter than scraper 1; scraper 4 slightly longer than scraper 5, about 1.7 times shorter than scraper 1; scraper 5 longer than scraper 6, about 2.2 times shorter than scraper 1; scraper 6–7 of similar length, about 2.9 times shorter than scraper 1; scraper 8 about 1.4 times shorter than scrapers 6–7. Scrapers 1–2 armed with fine robust spines each. Scrapers 3–8 armed with thick spines, scraper 6 with relatively strong spines. Proximal portion of gnathobase wide and densely setulated; distal portion armed with three elements and one sensillum, first element as a long seta. Filter comb armed with six setulated setae; the two most proximal setae shorter than the others.

Limb III ( Fig. 2D–E View FIGURE 2 ). Pre-epipodite not studied. Epipodite oval, with a short projection. Exopodite subquadrangular, armed with four distal and two lateral setae; sixth seta slightly longer than fifth seta; fourth seta plumose, about 1.5 times longer than third seta and 2.4 longer than second seta; third seta plumose, about 1.5 times longer than second seta and 3.4 times longer than first seta; first seta about 1.1 times shorter than second seta. Distal endite with three setae (1–3), setae (1–2) scraper-like, seta (3) armed with many setulae bilaterally implanted; four plumose posterior setae that increase in length towards the posterior part of the endite (a–d). Basal endite with four short, soft anterior setae (4–7) increasing in length towards to posterior part of the endite. Gnathobase armed with four elements, the first being a cylindrical sensillum (S), the second a geniculated and relatively short seta, third and fourth elements naked; filter plate with six setulated setae.

Limb IV ( Fig. 2F–G View FIGURE 2 ). Pre-epipodite not studied. Epipodite subquadrangular, with a long projection. Exopodite rounded with six marginal setae, setae 2–6 plumose; sixth seta about 1.4 times longer than fifth seta; fifth seta similar in length to second seta; fourth seta long, about 3.4 times longer than third setae; second seta about two times longer than third seta and 1.3 times longer than first seta. Distal endite with four setae (1–4); seta 1 chitinized; flaming torch-like setae (3–4) decreasing in length towards the base. Basal endite armed with three setulate setae that increase in length towards the gnathobase (a–c). Gnathobase with three elements, armed with a seta shorter than the endite itself; filter plate with five setae.

Limb V ( Fig. 2H–I View FIGURE 2 ). Pre-epipodite subquadrangular and densely setulated. Epipodite oval, with a long projection. Exopodite armed with four marginal plumose setae; first seta about 1.5 times longer than second seta; second seta about 1.2 times longer than third seta; third seta about 1.7 times longer than fourth seta. Internal lobe wide, rounded and with long terminal setulae, two setulated setae of different size on its inner face; the longest one exceeds the internal lobe. Gnathobase armed with two elements, filter plate absent.

Abdomen ( Figs. 1A View FIGURE 1 , 3A View FIGURE 3 ). About three times shorter than thorax, two transverse rows of setulae present at its dorsal surface.

Postabdomen ( Figs. 3A–B View FIGURE 3 ). Long, about 2.4 times as long as wide. Preanal margin about 1.9 times longer than anal margin and similar in length to postanal margin. Anal margin clearly concave, angles prominent, three groups of marginal denticles present. Postanal margin slightly rounded, tapering distally; 7–8 groups of marginal denticles, distalmost denticles merged; 8–10 groups of lateral fascicles armed with long setulae which do not exceed the level of marginal denticles.

Postabdominal seta ( Fig. 3A View FIGURE 3 ). About 0.5 of postabdomen length, bisegmented, provided with setulae in the distal segment.

Postabdominal claw ( Fig. 3A View FIGURE 3 ). About 1.5 times longer than anal margin, pecten with proximalmost spinulae longer than the distalmost ones; base armed with 2–4 long setulae. Basal spine inserted far of postabdominal claw base, relatively long and slender, about 2.5 times as long as width of the postabdominal claw at its base; armed with short spinulae.

Ephippial female. Unknown.

Male ( Fig. 3 View FIGURE 3 ). General ( Fig. 3C View FIGURE 3 ). Body ovoid in lateral view and laterally compressed in anterior view, without lateral projections. Smaller than the female, length ranging between 0.24–0.26 mm, height/length ratio about 0.6.

Carapace ( Fig. 3C View FIGURE 3 ). With longitudinal lines on valves. Ventral margin with a row of setae that do not reach its end, organized in three groups; anterior and posterior groups with setae longer than median group; spinules not arranged in groups, some spinules exceeding the marginal line ( Fig. 3D View FIGURE 3 ). Posteroventral corner without denticles.

Cephalic structures ( Fig. 3E View FIGURE 3 ). Ocellus as large as eye. Rostrum. Similar to female. Labrum. Similar to female. Antenna I about 2.1 times longer than wide, with three long rows of setulae on the antennular body, never extending beyond the tip of the rostrum; antennular sensory seta slender, about 2.1 times shorter than the length of the antennular body, inserted at 2/3 of antennular body; male seta subterminal short and robust, inserted at 3/3 of antennular body; 11 apical aesthetascs of different lengths present. Antenna II similar to that of the female.

Limb I ( Fig. 3F–G View FIGURE 3 ). Smaller than in females. Its copulatory hook U-shaped, with the two arms sub-equal in length. Copulatory brush present, seta of the copulatory brush as long as the male seta on the IDL. IDL with two setae (2–3) of different lengths and armed with relatively large proximal spines. Male seta (ms) about 1.7 longer than the IDL seta (2).

Abdomen ( Fig. 3C View FIGURE 3 ). About three times shorter than the thorax, three transverse rows of setulae present at its dorsal surface.

Postabdomen ( Fig. 3H View FIGURE 3 ). Rectangular, about 2.4–2.6 times longer than height.Anal and postanal margins similar in length, angle prominent. Postanal margin narrowing towards the distal portion; up to six groups of marginal spinulae present; 8–10 lateral fascicles. Gonopores opening ventrally, above the protrusion at the distal margin of the postabdomen.

Postabdominal seta. About 0.6 of the postabdominal length.

Postabdominal claw ( Fig. 3H–I View FIGURE 3 ) about 1.2 times shorter than anal margin, pecten armed with spinulae, median group longer than the distalmost one; tip with a slender and short flagellum. Basal spine about 2 times shorter than postabdominal claw, slender, relatively curved.

Differential diagnosis. The trachystriata -group could be recognized by the combination of following morphological characters: ventral setae of the carapace not reaching the end of ventral margin, posteroventral corner of carapace free of denticles or groups of setulae, a rostrum relatively large and blunt, a postabdomen tapering distally and exopodite of second limb without seta ( Kotov et al. 2011; Sousa et al. 2015; Sinev et al 2024). Thus, Coronatella jimenezae sp.nov. belongs to the trachystriata -group together with Asian C. trachystriata (Chen, Zhang & Liu, 1994) and Neotropical C. paulinae Sousa, Elmoor-Loureiro & Santos, 2015 . Looking at parthenogenetic females, the new species can be differentiated from C. trachystriata in the presence of a moderate dorsal keel on carapace, wide and rounded labral keel, presence of a seta on the first segment of antenna endopodite, and shape of postanal part of the postabdomen. Coronatella jimenezae sp. nov. can be differentiated from C. paulinae by the following characters: (1) PP/IP about 1.5 in C. jimenezae vs. 0.6 in C. paulinae ; (2) lateral head pores located at greater distance from midline in C. jimenezae , whereas in C. paulinae the lateral head pores are located near the midline; (3) on the first limb, the basalmost spines on the IDL setae are about two times greater than the width of the base of the respective setae, whereas in C. paulinae they are similar or slightly shorter than the base width of the respective setae; (4) on the second limb, the sixth scraper bears up to seven thick spines slightly smaller than the width of the scraper base, whereas in C. paulinae the spines are thin and markedly shorter than width of the scraper base; (5) seta 1 on the third limb exopodite is about 1.1 times shorter than the second seta in C. jimenezae , whereas in C. paulinae the proportion is 1.5; (6) gnathobase of fifth limb is lacking setae in C. jimenezae whereas in C. paulinae there is a single seta on gnathobase. Regarding males, Coronatella jimenezae sp. nov. differs from C. paulinae in shape of labral keel and proportion of the male seta on the first limb; in Coronatella jimenezae sp. nov. the tip of the postabdominal claw bears a slender and short flagellum, this morphological trait is a relevant autapomorphy of the species.

Distribution and biology. Coronatella jimenezae sp. nov. is reported only from La Española fluvial lake, located in the Manacacías river basin, Meta department, Colombia. The new species was collected in a site at a depth of 1.45m and in slightly alkaline water (pH = 7.32), temperature of 25.69 °C and oxygen saturation of 72.2%. Coronatella jimenezae sp. nov. is found in co-occurrence with several Chydoridae species, including the rare Matralona sp. ( Fuentes-Reinés et al. 2023b).