Kurzia cf. longirostris ( Daday, 1898 )

Moreira-Silva, Camila, Sousa, Francisco Diogo Rocha, Elmoor-Loureiro, Lourdes M. A., Isumbisho, Mwapu, Sarmento, Hugo, Borges, Alberto V. & Perbiche-Neves, Gilmar, 2025, New morphological data on Kurzia longirostris (Daday, 1898) (Crustacea, Branchiopoda) from the Congo River Basin, ZooKeys 1257, pp. 339-354 : 339-354

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 ( FDRS 0703 ) . • Five adult females from the Kasai River , Congo River, DR Congo ( -3.26218, 17.46914 and -3.26218, 19.2611), material collected between 20.iv.2015 and 26.iv.2015 ( FDRS 0704 ) . • One adult parthenogenetic female from the Itimbiri River , Congo River Basin, DR Congo ( 2.06387, 22.69562), material collected on 13.vi.2014 ( FDRS 0705 ) . • One adult parthenogenetic female from the Ikelemba River , Congo River Basin, DR Congo ( 0.10862, 18.29738), material collected on 19.vi.2014 ( FDRS 0706 ) . • One adult parthenogenetic female from the Ruki River , Congo River Basin, DR Congo ( 0.07411, 18.31294), material collected between 20.vi.2014 ( FDRS 0707 ) . • One adult parthenogenetic female from the Kamatsha River , Congo River Basin, DR Congo ( -3.71521, 18.92626), material collected between 25.iv.2015 ( FDRS 0708 ) .

Description of parthenogenetic females.

General habitus (Figs 1 A, B , 4 A, 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. 1 C ) and ventral views (Fig. 1 D ); body laterally compressed.

Carapace (Figs 1 E , 4 E ): 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 1 F – J , 4 F ): ocellus smaller than eye. Head shield (Fig. 1 F ) covered by longitudinal lines. Rostrum (Figs 1 F, G , 4 C, 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 1 H , 4 G, 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. 1 I, J ) short, armed with lateral horns; keel triangular, free of spines or notch, apex round or slightly sharp. Antennule – A 1 (Fig. 1 K ) 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 – A 2 (Fig. 1 L ): 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. 1 M ) well developed, with 2 long setulate setae.

Thoracic limbs (Figs 2 A – I , 4 I ): 5 pairs of thoracic limbs.

First limb (Figs 2 A – C , 4 J ). 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 (en 4) 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. 2 D ). 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. 2 E, 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. 2 G, 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-torch-like 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. 2 I ). Pre-epipodite rounded and densely setulate; epipodite oval, with 2 projections. Exopodite bilobate, armed with 4 plumose setae; first 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. 3 A ). About 3 × shorter than thorax, 2 transverse rows of setulae present on dorsal surface. Postabdomen (Figs 3 A – C , 4 K – 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 margin, about 0.35–0.50 of length of postabdomen; pecten with proximalmost spinulae longer than distalmost ones. Basal spines (Fig. 4 M ) armed with spiculae, about 0.08–0.09 of length of postabdominal claw, shorter than width of postabdominal claw at its base.

Males. We did not encounter male specimens in our samples. Therefore, males were not studied. However, drawings and a short diagnosis of K. longirostris males can be found in Smirnov (1971).

Ephippial females. Not studied.

Variability.

Two individuals of Kurzia cf. longirostris ( Daday, 1898) had two short denticles on the posteroventral corner of the carapace (Fig. 1 E ). In the postabdomen, the postanal margin might be strongly concave with distalmost part very elongated (Fig. 3 B, C ). More than concave, mostly the distalmost part was elongated. There were some variations regarding the tip and length of the rostrum.

Distribution and biology.

Kurzia longirostris s. l. is widely distributed in the Oriental region ( terra typica) ( Daday 1898). In the Australasian region, this species was considered as possibly rare ( Smirnov and Timms 1983). Populations from the Neotropical region are observed in a few localities, especially in Brazil and Colombia ( Elmoor-Loureiro et al. 2023; Fuentes-Reinés et al. 2022). In the Afrotropics, besides the Congo River Basin ( DR Congo), the presence of the species extends throughout the basins of the Volta, Niger, and Chari Rivers ( Rey and Saint-Jean 1969; Smirnov 1971; Chiambeng and Dumont 2005; Neretina et al. 2017) (Fig. 5 ).

The populations examined here were collected from stretches with water temperatures ranging from 25.9 to 28.9 ° C, dissolved oxygen range of 1.29–6.76 mg / L - 1, pH of 3.63–7.18, and conductivity of 13.3–77.1 µS / cm (see Borges et al. 2019 for methods of measuring environmental parameters).

Figures

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.

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.

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.

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.

Figure 5. Geographic distribution of Kurzia longirostris s. l. (Daday, 1898) based on previous studies (Rey and Saint-Jean 1969; Smirnov 1971; Smirnov and Timms 1983; Rajapaksa and Fernando 1986; Smirnov and De Meester 1996; Hudec 2000; Chiambeng and Dumont 2005; Gutiérrez et al. 2008; Padhye and Dumont 2015; Neretina et al. 2017; Fuentes-Reinés et al. 2022), and GBIF (2025). The new records of Kurzia cf. longirostris (Daday, 1898) from the Congo River Basin, DR Congo, are presented as triangles.