New morphological data on Kurzia longirostris (Daday, 1898) (Crustacea, Branchiopoda) from the Congo River Basin

339 New morphological data on Kurzia longirostris (Daday, 1898) (Crustacea, Branchiopoda) from the Congo River Basin Camila Moreira-Silva1, Francisco Diogo Rocha Sousa2, Lourdes M. A. Elmoor-Loureiro2, Mwapu Isumbisho3, Hugo Sarmento4, Alberto V. Borges5, Gilmar Perbiche-Neves1,4 1 Programa de Pós-graduação em Ciências Biológicas (Zoologia), Universidade Estadual Paulista, Instituto de Biociências, Botucatu, Brazil 2 Universidade Federal de Jataí, Instituto de Biociências, Laboratório de Taxonomia Animal, Jataí, Brazil 3 Unité d’Enseignement et de Recherche en Hydrobiologie Appliquée, Département de Biologie-Chimie, ISP/Bukavu, Bukavu, Democratic Republic of the Congo 4 Universidade Federal de São Carlos, Departamento de Hidrologia, São Carlos, Brazil 5 University of Liège, Chemical Oceanography Unit, Liège, Belgium Corresponding author: Camila Moreira-Silva (camoreir[email protected]) Copyright: © Camila Moreira-Silva et al. This is an open access article distributed under terms of the Creative Commons Attribution License (Attribution 4.0 International – CC BY 4.0). Research Article Abstract Africa is recognized for its high levels of endemism across many groups of organisms, including Cladocera. Several studies contributed to our understanding of the diversity and geographic distribution of some groups of Chydoridae on this continent. The literature, however, points to species presumed to occur naturally on other continents, suggesting that both diversity and endemism in Africa continue to be underestimated. Despite the absence of more comprehensive knowledge about the morphology of Kurzia longirostris (Daday, 1898) from the terra typica (Oriental region), our findings revealed small morphological differences between populations of the Congo River when compared with literature reports. Looking at the high morphological variability along the range of its geographic distribution, it becomes clear that K. longirostris might be indicated as a species complex. Thus, the idea of continental endemism should be tested in a future revision of the group. Key words: Africa, Chydoridae, Congo Basin, endemism, taxonomy Introduction The cladoceran fauna of Africa is recognized for its high endemism, especially regarding Chydoridae (Chiambeng and Dumont 1998; Sinev 2006, 2008; Smirnov 2008; Van Damme and Dumont 2008, 2009; Van Damme and Eggermont 2011; Van Damme et al. 2011, 2013a; Neretina and Sinev 2021). Currently, the diversity on the African continent is better understood thanks to several studies of species groups within Leydigia Kurz, 1875, Acroperus Baird, 1843, Anthalona Van Damme, Sinev & Dumont, 2011, Coronatella Dybowsky & Grochowski, 1894, Nicsmirnovius Chiambeng & Dumont, 1999, Matralona Van Damme & Dumont, 2009, Alona Baird, 1843, and Biapertura Smirnov, 1971 emend. Sinev 2020 (Van Damme et al. 2003, 2011; Van Damme and Dumont 2008, 2009; Kotov 2009; Sinev 2009; Neretina and Kotov 2015; Van Damme 2016). Nevertheless, literature Academic editor: Kay Van Damme Received: 13 November 2024 Accepted: 26 September 2025 Published: 31 October 2025 ZooBank: https://zoobank. org/85A6C54F-AEA2-4B4F-8F922849567CF3AC Citation: Moreira-Silva C, Sousa FDR, Elmoor-Loureiro LMA, Isumbisho M, Sarmento H, Borges AV, PerbicheNeves G (2025) New morphological data on Kurzia longirostris (Daday, 1898) (Crustacea, Branchiopoda) from the Congo River Basin. ZooKeys 1257: 339–354. https://doi.org/10.3897/ zookeys.1257.141692 ZooKeys 1257: 339–354 (2025) DOI: 10.3897/zookeys.1257.141692 340 ZooKeys 1257: 339–354 (2025), DOI: 10.3897/zookeys.1257.141692 Camila Moreira-Silva et al.: Kurzia longirostris from the Congo River Basin suggests that there are species with a wide range of distribution in the Old World, found throughout the southern Palearctic, Afrotropical, and Oriental zones, such as Anthalona harti Van Damme, Sinev & Dumont, 2011 (Van Damme et al. 2011) and Leberis punctatus (Daday, 1898) (Neretina and Sinev 2016). At the same time, there are several reports of taxa considered as species complexes, which might harbor separate local species in Africa, for instance, Prendalona guttata (Sars, 1862) (also “Alona” guttata), Alona intermedia Sars, 1862 and Chydorus sphaericus (O.F. Müller, 1776) (Dumont et al. 1981; Dumont 1981; Van Damme and Eggermont 2011). These reports suggest that chydorid diversity and endemism in Africa is still underestimated (Van Damme and Dumont 2008, 2009). Kurzia longirostris (Daday, 1898) also occurs in the Afrotropical zone, presenting a wide range of distribution including the Oriental zone (its terra typica), Neotropical, South Asian, and Australasian regions (Gauthier 1937; Rajapaksa and Fernando 1986; Rey and Saint-Jean 1969; Smirnov 1971; Dumont 1981; Hudec 2000; Padhye and Dumont 2015; Sinev 2016). The discovery history of this taxon began when Eugen von Daday described Alona longirostris (Daday, 1898). Later, Sars (1901) reported the presence of this species in Brazil and suggested its transfer to the genus Pseudoalona Sars, 1901. The name Pseudoalona longirostris was used in the following years (Brehm 1933, 1934; Gauthier 1937), until the revision from Harding (1957) indicating that this species belonged to the genus Kurzia Dybowski & Grochowski, 1894, a classification that has been used since then (Smirnov 1971; Hudec 2000; Sinev 2016; Neretina et al. 2017). Besides K. longirostris, this genus is composed of four other species. Kurzia latissima Kurz, 1874 with a natural distribution in the Palearctic zone despite reports from Africa and the Neotropics (Smirnov 1971; Chiambeng and Dumont 2005). According to Hudec (2000) Kurzia media Birge, 1879 should be considered as a valid species, with reports from the Holarctic and Neotropical zones (Fuentes-Reinés et al. 2022; Andrade et al. 2024). Kurzia brevilabris Rajapaksa & Fernando, 1986 is distributed in South East Asia; however, it does not co-occur with K. longirostris (Rajapaksa and Fernando 1986). Finally, Kurzia polyspina Hudec, 2000 was described (Hudec 2000) from the Neotropical zone and is currently known from Mexico to southern Brazil (Elmoor-Loureiro 2002; Elmoor-Loureiro et al. 2023). In addition to its wide geographic distribution across tropical and subtropical regions, morphological data on K. longirostris indicate considerable variation, particularly in the postabdomen, rostrum, and labrum. These observations highlight the need for a comprehensive taxonomic review, with special attention to detailed limb morphology. To address this, we examined African populations of K. longirostris collected from rivers and streams of the Congo River Basin, Democratic Republic (DR) of Congo. Materials and methods Morphological analyses Observations were carried out in binocular stereo microscope, mounted in drops of glycerin on slides and studied under an Olympus BX41 phase contrast microscope to investigate their morphological traits. The presentation of morphological structures follows the suggestions of Van Damme (2016). To enumerate the limb setae, we adopted the homology criteria of Kotov (2000a, 2000b), 341 ZooKeys 1257: 339–354 (2025), DOI: 10.3897/zookeys.1257.141692 Camila Moreira-Silva et al.: Kurzia longirostris from the Congo River Basin which exhibited stability when tested in different groups of cladocerans (Kotov et al. 2010). All drawings were made using a camera lucida and digitally covered using a graphic tablet (Wacom IntuosTM) and Adobe Illustrator 2020. SEM processing The samples were initially fixed in 2.5% glutaraldehyde in 0.1 M phosphate buffer (pH 7.3) for 4 h, followed by three washes in distilled water (5 min each). They were then post-fixed in immersed in 0.5% osmium tetroxide in distilled water for approximately 30–40 min (Perbiche-Neves et al. 2015). Subsequently, the material was washed three× in distilled water (10 min each), followed by dehydration through a graded ethanol series, starting at 7.5% progressing to 100%. Finally, samples were dried by critical point drying, mounted on stubs and sputter-coated for scanning electron microscopy analysis. All processing and acquisition of scanning electron microscopy (SEM, Quanta 200, FEI Company) images were performed at the Electron Microscopy Center of the Botucatu Institute of Biosciences, UNESP, Botucatu Campus, Brazil. Abbreviations of scientific collections FDRS = Personal collection of Francisco Diogo Rocha Sousa. Abbreviations used in the figures and the text: en = endite; ep = epipodite; ex = exopodite; gfp = gnathobasic filter plate; gn = gnathobase; IP = interpore distance (distance between the anterior and posterior major head pores); IDL = inner distal lobe; il = inner lobe; L1 = First limb; L2 = Second limb; L3 = Third limb; L4 = Fourth limb; ODL = outer distal lobe; PP = postpore distance (distance between the posterior major head pore and the posterior border of the head shield); s = sensillum. Results Taxonomy Class Branchiopoda Latreille, 1817 Order Anomopoda Sars, 1865 Family Chydoridae Dybowsky & Grochowski, 1894 emend. Frey, 1967 Subfamily Aloninae Dybowsky & Grochowski, 1894 emend. Frey, 1967 Genus Kurzia Dybowsky & Grochowski, 1894 Kurzia cf. longirostris (Daday, 1898) Alona longirostris in Daday (1898) Alona macrohyncha in Daday (1900) Pseudoalona longirostris in Sars (1901), Brehm (1933, 1934) and Gauthier (1937) Material examined. • Eight adults parthenogenetic females from the Congo main river channel, Congo River Basin, DR Congo (-0.60979, 17.6667 and -4.02029, 18.21978), material collected between 17.xii.2013 and 06.v.2015 (FDRS0703). • Five adult females from the Kasai River, Congo River, DR Congo 342 ZooKeys 1257: 339–354 (2025), DOI: 10.3897/zookeys.1257.141692 Camila Moreira-Silva et al.: Kurzia longirostris from the Congo River Basin (-3.26218, 17.46914 and -3.26218, 19.2611), material collected between 20.iv.2015 and 26.iv.2015 (FDRS0704). • One adult parthenogenetic female from the Itimbiri River, Congo River Basin, DR Congo (2.06387, 22.69562), material collected on 13.vi.2014 (FDRS0705). • One adult parthenogenetic female from the Ikelemba River, Congo River Basin, DR Congo (0.10862, 18.29738), material collected on 19.vi.2014 (FDRS0706). • One adult parthenogenetic female from the Ruki River, Congo River Basin, DR Congo (0.07411, 18.31294), material collected between 20.vi.2014 (FDRS0707). • One adult parthenogenetic female from the Kamatsha River, Congo River Basin, DR Congo (-3.71521, 18.92626), material collected between 25.iv.2015 (FDRS0708). Description of parthenogenetic females. General habitus (Figs 1A, B, 4A, B): rounded body in lateral view, length 0.42– 0.52 mm (n = 17), height/length ratio 0.68–0.75; dorsal margin arched, with moderate dorsal keel, without lateral projections; in dorsal (Fig. 1C) and ventral views (Fig. 1D); body laterally compressed. Carapace (Figs 1E, 4E): covered by longitudinal lines on valves and head shield; anteroventral margin rounded, with an evident flange; ventral margin almost rounded, with a distinctive rounded angle at 2/3 of margin’s length. Setae at valve ventral margin 38–44, organized into three groups; anterior group with 5 or 6 long setae, median group with up 21 shorter plumose setae, posterior group with up 17 plumose setae. Posterior margin clearly rounded, armed with spinulae exceeding marginal line of valves. Cephalic structures (Figs 1F–J, 4F): ocellus smaller than eye. Head shield (Fig. 1F) covered by longitudinal lines. Rostrum (Figs 1F, G, 4C, D) long and slightly curved, in frontal view tip not sharp, about 1.3–2.0× longer than antennular body; posterior margin triangular. Head pores (Figs 1H, 4G, H): 3 main head pores with anterior and posterior ones longer than median pore, connected by a thick rim; posterior pore transversally elongate, sometimes bilobed; lateral pores inserted in a deep depression, distance from median main head pore about 1.6× PP; PP/IP about 0.42. Labrum (Fig. 1I, J) short, armed with lateral horns; keel triangular, free of spines or notch, apex round or slightly sharp. Antennule – A1 (Fig. 1K) approximately 4.5–5.0× longer than wide, never extending beyond tip of rostrum; antennular sensory seta slender, about 2.5–3.1× shorter than length of antennular body, inserted near mid-length of antennular body; 9 aesthetascs which 3 are longer than others but shorter than antennular body, protruding beyond tip of rostrum. Antenna – A2 (Fig. 1L): basal segment thick, with a short spine; first exopodite segment of similar length to first endopodite segment, armed with 2 clusters of long setulae, apical seta bisegmented and plumose, longer than segment itself; second exopodite segment with a bisegmented, plumose seta equal in length to longest apical setae of third segment; apical spine similar in length to endopodite apical spine; first endopodite segment armed with a spine about 2× shorter than apical spine on third segment; antennal formula (exo/endo): spines 001/101, setae 113/003. Maxilla (Fig. 1M) well developed, with 2 long setulate setae. Thoracic limbs (Figs 2A–I, 4I): 5 pairs of thoracic limbs. First limb (Figs 2A–C, 4J). Epipodite oval, armed with a short digitiform projection. ODL seta bisegmented, armed with fine, short spines, longer than the IDL third seta; accessory seta plumose, similar in length to ODL seta. IDL 343 ZooKeys 1257: 339–354 (2025), DOI: 10.3897/zookeys.1257.141692 Camila Moreira-Silva et al.: Kurzia longirostris from the Congo River Basin Figure 1. Kurzia cf. longirostris (Daday, 1898) from the Congo River Basin, DR Congo, parthenogenetic female. A, B. Habitus; C. Dorsal view; D. Ventral view; E. Ventral margin of carapace, median and posterior portions; F. Rostrum; G. Idem, frontal view; H. Head pores; I. Labral keel; J. Idem, frontal view showing the lateral horns; K. Antennule; L. Antenna; M. Maxilla. 344 ZooKeys 1257: 339–354 (2025), DOI: 10.3897/zookeys.1257.141692 Camila Moreira-Silva et al.: Kurzia longirostris from the Congo River Basin Figure 2. Kurzia cf. longirostris (Daday, 1898) from the Congo River Basin, DR Congo, parthenogenetic female. A. First limb; B. Idem, endite 3; C. Idem, ODL and IDL; D. Second limb; E. Third limb; F. Idem, basal endite; G. Fourth limb; H. Idem, basal endite and gnathobasic filter plate; I. Fifth limb. Scale bars: 0.05 mm. 345 ZooKeys 1257: 339–354 (2025), DOI: 10.3897/zookeys.1257.141692 Camila Moreira-Silva et al.: Kurzia longirostris from the Congo River Basin (en4) with 1 group of short setulae on corm, 3 setae present; seta 1 armed with spines, length about ½ as long as setae 2–3; seta 2 slightly shorter than seta 3; setae 2–3 chitinized and bisegmented, armed with relatively short, thick proximal spines. Endite 3 with 4 setae; anterior seta 1 thin and unarmed about 1.4× longer than posterior seta (c); posterior setae (a–b) of similar length among themselves, armed with spines on the middle part, shorter than anterior seta 1; seta (c) armed laterally with short spines, shorter than the setae (a–b). Endite 2 with 3 posterior setae present (d–f); seta (d) armed with short spines near to middle part, about 1.7× shorter than seta (e); seta (e) long, armed laterally with short spines; seta (f) about 1.2× longer than seta (d) and 1.3× shorter than seta (e). Endite 1 with 2 posterior setae of similar length (g–h), which are bisegmented and densely setulate on distal part. Ejector hooks all similar length and armed with spines; ventral face of the limb with 6–8 clusters of thick setulae. Gnathobase not studied. Second limb (Fig. 2D). Exopodite without seta, armed with 2 rows of short spinulae. Inner limb portion armed with 8 scrapers; scraper 1 similar in length of scraper 2; a long element present near to scraper 1 base; scrapers 3–4 similar in length, about 0.8 of scraper 1 length; scrapers 5 shorter than the scarper 3–4, about 0.8 length of scraper 1; scrapers 6–7 of similar length, shorter than the scraper 5, about 0.4 length of scraper 1; scraper 8 shorter than scrapers 6–7, about 0.3 length of scraper 1; scraper 6–8 armed with thicker spines than on other scrapers. Proximal portion of the gnathobase setulate, armed with 4 elements; filter plate with 7 setulate setae. Third limb (Fig. 2E, F). Epipodite oval, with 2 short projections. Exopodite rectangular armed with 5 distal and 2 lateral setae; seventh seta setulate, longer than the sixth, similar in length to third seta; fifth seta geniculated, densely setulate, about 3.3× longer than fourth seta, about 2.5× longer than second seta; fourth seta densely setulate, about 2.2 longer than third seta; second seta plumose, about 3× longer than third seta, about 1.2× longer than first seta; first seta armed laterally with short setulae. Distal endite with three setae (1–3), seta (1–2) scraper-like, seta (3) curved and armed with many setulae bilaterally implanted; 4 plumose posterior setae increasing in length toward to posterior part of the endite (a–d). Basal endite with 4 soft anterior setae 4–7) of similar length. Gnathobase armed with four elements, first being a cylindrical sensillum, second a geniculated and relatively short seta, third and fourth elements naked; filter plate with five plumose setae. Fourth limb (Fig. 2G, H). Pre-epipodite oval and densely setulate; epipodite oval with two projections. Exopodite wide, with six plumose marginal setae; sixth seta slightly longer than fifth seta; fourth seta about 0.8 of sixth seta length; third seta about 0.6 of sixth seta length; second seta longer than the first seta, about 0.4 of sixth seta length; first seta about 1.8× shorter than the third seta, about 0.3 of sixth seta length; third seta about 1.5× longer than second seta. Distal endite with 4 setae (1–4); seta 1 chitinized; flaming-torchlike setae (3–4) markedly shorter than the seta 1. Basal endite armed with 3 setulate setae which increase in length towards to gnathobase (a–c). Gnathobase with 2 elements, armed with a seta of similar in length to width of endite; filter plate with 5 setae. Fifth limb (Fig. 2I). Pre-epipodite rounded and densely setulate; epipodite oval, with 2 projections. Exopodite bilobate, armed with 4 plumose setae; first 346 ZooKeys 1257: 339–354 (2025), DOI: 10.3897/zookeys.1257.141692 Camila Moreira-Silva et al.: Kurzia longirostris from the Congo River Basin seta about 2× shorter than fourth seta; second and third setae similar in length, about 1.6× longer than first seta; fourth seta about 1.4× longer than second and third setae. Internal lobe wide, rounded and with many setulae; setae 1–2 setulate; seta 1 about 1.6× longer than seta 2. Gnathobase armed with 2 elements, filter plate absent. Abdominal and postabdmominal structures: Abdomen (Fig. 3A). About 3× shorter than thorax, 2 transverse rows of setulae present on dorsal surface. Postabdomen (Figs 3A–C, 4K–M) narrow, about 4.5–7.5× longer than wide; ventral margin slightly curved; preanal and anal margins of similar length, angles prominent; postanal part elongate, margin markedly concave, distalmost part projected beyond postabdominal claw base; 8–12 marginal denticles, distalmost denticles sometimes isolated, proximal most denticles might be accompanied by 1–4 fine, short spines; 11–16 lateral fascicles formed by thin, short spinulae. Postabdominal setae about 0.6 of postabdomen length, bisegmented, armed with setulae in the distal segment. Postabdominal claw with spicules on surface, longer than anal Figure 3. Kurzia cf. longirostris (Daday, 1898) from the Congo River Basin, DR Congo, parthenogenetic female. A. Postabdomen; B. Idem, illustrating strongly concave postanal dorsal margin; C. Idem, detail distalmost part and terminal claws. Scale bars: 0.05 mm. 347 ZooKeys 1257: 339–354 (2025), DOI: 10.3897/zookeys.1257.141692 Camila Moreira-Silva et al.: Kurzia longirostris from the Congo River Basin margin, about 0.35–0.50 of length of postabdomen; pecten with proximalmost spinulae longer than distalmost ones. Basal spines (Fig. 4M) armed with spiculae, about 0.08–0.09 of length of postabdominal claw, shorter than width of postabdominal claw at its base. Figure 4. Kurzia cf. longirostris (Daday, 1898) from the Congo River Basin, DR Congo, parthenogenetic female. A, B. Habitus; C, D. Rostrum; E. Posteroventral corner of carapace; F. Head shield (arrows show position of lateral head pores); G, H. Head pores; I. Trunk limbs; J. First limb, ODL, and IDL; K. Postabdomen; L. Idem, postabdominal claws; M. Idem, basal spines. 354 ZooKeys 1257: 339–354 (2025), DOI: 10.3897/zookeys.1257.141692 Camila Moreira-Silva et al.: Kurzia longirostris from the Congo River Basin Smirnov NN (1971) Chydoridae Fauny Mira. Fauna USSR. 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