Coronatella (Coronatella) cf. bukobensis ( Weltner, 1896 ) sensu Sars (1916)

Sinev, Artem Y., 2020, Revision of the elegans-group of Alona s. lato and its status as a subgenus of Coronatella Dybowski & Grochowski, 1894 (Cladocera: Anomopoda Chydoridae), Zootaxa 4732 (4), pp. 501-526 : 515-518

Coronatella (Coronatella) cf. bukobensis ( Weltner, 1896) sensu Sars (1916)

Figs (9A-H)

Weltner 1986: 1-11, Fig. 16-18, 20, 32 ( Alona ); Daday 1910: 132, Pl. 7, Fig 15-16 ( Alona rectangula var. bukobensis ); Sars 1916: 336-337, pl. XL, Fig. 3, 3a ( Alona ); Smirnov, 1971: 365,

Fig. 423-424 ( Alona ). Not Alona bukobensis in Ekman 1904: 10-14 , Fig. 5 -10; Gauthier, 1928: 321, Fig. 40.

Material examined. Over 50 parthenogenetic females, 7 ephippial females, and 4 males from Dune Pan, near Road 27, North of Blauwbergstrand, Cape Town, Republic of South Africa, 2.10.1990, coll. D.G. Frey, DGF-8934; over 30 parthenogenetic females from swimming pool at picnic area near Olienhut, Mountain Zebra National Park, Cape Province, Republic of South Africa, 2.10.1990, coll. D.G. Frey, DGF-8999;

Description. Parthenogenetic female. General. In lateral view, body oval, moderately compressed laterally, low in juveniles ( Fig. 6 A-C); moderately high in adults ( Fig. 6C , 7 A-C). Maximum height at middle of body. Height-length ratio about 0.65 in adults. Dorsal margin convex, postero-dorsal and postero-ventral angles broadly rounded. Posterior margin convex, ventral margin almost straight, antero-ventral angle rounded. Ventral margin ( Fig. 6D ) with 40-50 setae. About 10 anterior setae longer than others. Postero-ventral angle ( Fig. 6E ) with over 70 setulae not organized into groups. Carapace, except antero-dorsal portion, covered by moderately thick, sparsely spaced longitudinal lines.

Head relatively small, triangle-round in lateral view, rostrum short, pointing downward. Eye slightly larger than ocellus. Distance from the tip of rostrum to the ocellus equal or slightly greater than that between the ocellus and the eye.

Headshield with maximum width behind mandibular articulation, without any prominent sculpture ( Fig. 6F ). Rostrum short, broadly rounded. Posterior margin of headshield broadly rounded. Three narrowly connected major head pores ( Fig. 6G ), middle pore slightly smaller than others, located at the middle between others. PP about 0.3 IP. Lateral head pores located at about 0.7 IP distance from midline, at the level between anterior and middle major head pore.

Labrum relatively large ( Fig. 8A ). Labral keel of moderate width (height/width ratio about 1.5), with a rounded or blunt apex. Anterior margin of keel convex, posterior margin without clusters of setulae.

Thorax two times longer than abdomen. Dorsal surface of abdominal segments not saddle-shaped. No abdominal projections.

Postabdomen ( Fig. 6 H-I, 7D) short, of moderate width, with almost parallel margins in anal portion, weakly narrowing in postanal portion, with broadly rounded dorsal distal angle. Length about 2.2–2.4 height. Ventral margin from almost straight to weakly convex. Basis of claws bordered from distal margin by clear incision. Distal margin weakly convex. Dorsal margin with distal part about 1.8 times longer than preanal one; postanal and anal portions of similar length. Postanal portion weakly convex to straight; anal portion weakly concave. Preanal angle well defined, postanal angle not defined. Postabdomen with three-four moderately long composite marginal denticles in distal portion ( Fig. 7E ), followed by 6-7 clusters of smaller elemental marginal denticles, decreasing in size basally, along preanal and anal margin. About 10 lateral fascicles of setulae; 4-5 distalmost fascicles wide, closely spaced, with setulae longer than marginal denticles, with distalmost setula only slightly thicker than others. Additional groups of smaller fascicles in anal portion above the main row. Postabdominal claw ( Fig. 7F ) weakly curved, of moderate length, as long as preanal portion of postabdomen. Basal spine long and thin, about 1/3 of length of claw, a cluster of 3-5 long setulae located near its base.

Antennule ( Fig. 6J ) comparatively large, almost reaching tip of rostrum, with four clusters of long setulae at anterior face. Length/width ratio about 2.5. Antennular sensory seta slender, three times shorter than antennule, arising at about 2/3 distance from the base. Nine aesthetascs, three longest about 2/3 length of antennule.

Antenna short ( Fig. 7G , 8B ).Antennal formula, setae 0-0-3/1-1-3, spines 1-0-1/0-0-1. Basipodite robust, branches short and stout. Basal segments of both branches almost two times longer than middle and apical segments. Seta arising from basal segment of endopodite thin, reaching the end of endopodite. Seta arising from middle segment of endopodite shorter than apical setae. Both apical segments with one shorter and two longer setae of similar thickness. Spine on basal segment of exopodite much longer than middle segment. Spine from apical segments longer than apical segments.

Thoracic limbs. Five pairs.

Limb I ( Fig. 8 C-D) of moderate size. Epipodite oval, without process. Accessory seta short, about 1/3 length of ODL seta. ODL seta with minute setulation. IDL with 3 setae, seta 1 very small. Seta 3 as long as ODL seta; seta 2 slightly shorter than seta 2. Setae 2 and 3 ( Fig. 7H ) armed with robust spinules, two basalmost spinules on seta 2 and basalmost spinule on seta 3 much thicker and longer than others. Endite 3 with four setae of same length. Endite 2 with seta “d” as long as setae of endite 3; seta “e” long, about 2/3 length of limb itself; seta “f” about 2/3 length of seta e. Endite 1 with 2 distally setulated 2-segmented setae “g”-”h” and a long flat seta “i” as long as setae “a”-”d”. No naked inner setae (2-3) and sensillae on endites 1 and 2. Five rows of thin long setulae on ventral face of limb. Two ejector hooks of similar size. Maxillar process with single seta.

Limb II ( Fig. 8E ). Exopodite elongated, with seta about 2/3 length of exopodite. Eight scraping spines armed with thin setulae: scrapers 1-5 long, increasing in length distally; scraper 3 thicker than neighbours; scrapers 6-8 short, of similar size. Small seta located near the base of scraper 1. Distal armature of gnathobase with 4 elements. Filter plate with 7 setae, the two posteriormost ones considerably shorter than others.

Limb III ( Fig. 8 F-H). Epipodite oval, without process. Exopodite subrectangular, with 6 setae. Seta 3 being longest, seta 5 about 1/3 length of seta 3; seta 1 about 1/5 length of seta 3; other setae very short. Setae 1-4 plumose, seta 5 armed with thick setulae in distal portion, seta 6 naked. Distal endite with three setae; two sensillae located between their bases. Two distalmost setae (1–2) slender, sharp, of similar length, with long denticles in distal part; basalmost setae shorter, flattened and setulated. Basal endite with 4 outer setae (a–d) slightly increasing in length basally. Gnathobase not clearly separated from basal endite. Four inner setae (4–7) slightly increasing in size basally; a sensillum near the base of distalmost seta. Distal armature of gnathobase with four elements; the first one an elongated, cylindrical sensillum; the second a geniculated seta; two others are short spines with fused bases. Filter plate with seven setae.

Limb IV ( Fig. 8 I-K). Preepipodite setulated; epipodite oval, without process. Exopodite irregularly rounded, with 6 setae. Seta 3 longest; setae 1 and 2 about 4/5 length of seta 3; seta 5 about 2/3 length of seta 3; setae 4 and 6 short. Setae 1-4 flattened, plumose; setae 5 and 6 slender, with short setulae in distal portion. Inner lobe of limb IV with 4 setae ( Fig. 3N ). Distalmost seta (1) slender, sharp; flaming-torch setae (2-4) with narrow basal portion, armed with 7-9 thin setulae each. Sensillum strongly curved. Three soft setae (a-c) slightly increasing in size basally. Gnathobase with 2-segmented seta, and a small hillock distally. Filter plate with 5 setae.

Limb V ( Fig. 8L ). Preepipodite setulated; epipodite oval without process. Exopodite oval, not divided into two lobes, with four plumose setae decreasing in size basally. Inner limb portion a rounded lobe, with setulated inner margin. At inner face, two setae, one 1.5 times longer than another. Filter plate not found.

Ephippial female ( Fig. 6K ) with body slightly higher than parthenogenetic female, dorsal margin with depression between valves and headshield. Ephippium light yellow-brown in preserved specimens, with moderately developed egg locules, covered by weak polygonal sculpture (not shown on the drawing).

Male. Body ( Fig. 6L ) oval, lower than in female, height/length ratio about 0.6. Ocellus and eye of smaller than in female.

Postabdomen ( Fig. 6M ) short, slightly narrowing distally in postanal portion, with broadly rounded dorso-distal angle. Ventro-distal angle well-defined, obtuse. Sperm duct openings located ventrally almost at the end of postabdomen. Preanal angle well-defined, postanal angle not defined. Distal part of postabdomen 1.5 times longer than preanal, anal portion 1.5 times longer than postanal one. Clusters of short setulae in place of marginal denticles, lateral fascicles of setulae same as in female. Postabdominal claw 1.5 times shorter than that of female, with fourfive strong spines on the inner side. Basal spine long, about 0.3-0.4 length of claw.

Antennule ( Fig. 6O ) thicker than in female, with 10 terminal and 2 lateral aesthetascs. Lateral aestetascs about 2/3 length of antennule. Male seta arising at 2/3 length from tip, about 1/3 of antennule length.

Thoracic limb I ( Fig. 8 G-H) with short U-shaped copulatory hook 2.5 times shorter than limb itself. Copulatory brush present, copulatory brush seta short. Ventral face of limb below them with double row of short thick setulae. Inner distal lobe without seta 1, setae 2 and 3 much shorter and thinner than in female; seta 2 slender, without any spines at the middle, distal portion armed with thin setulae; seta 3 moderately thick, curved, with single spine at the middle and thin posterior portion armed with thin setulae, longer than seta 2; male seta curved, shorter than seta 3.

Size. In single studied instar I juvenile female, length was 0.25 mm, height 0.17 mm; in instar II juvenile female length 0.31-0.33 mm, height 0.19–0.21 mm; in adult parthenogenetic female length was 0.34–0.42 mm, height 0.22–0.27 mm. In adult male, length was 0.34–0.35 mm, height 0.20-0.22 mm.

Differential diagnosis. Cornatella cf. bukobensis is very close morphologically to the Palaearctic C. rectangula , but differs from it in less developed spines on IDL setae 2-3 and in more elongated male postabdomen. C. cf. bukobensis clearly differs from species of the monacantha -clade ( C. monacantha , C. undata , C. hardingi , C. acuticostata ) in absence of denticles on posteroventral angle of valves; from species of the trachystriata -clade ( C. trachystriata , C. paulinae ), in less developed longitudinal lines on the valves, not covering whole valve, in not truncated rostrum, and in strongly differentiated spinules on IDL seta 2-3; from C. begoniae in strongly differentiated spinules on IDL setae 2-3; from C. circumfimbriata and C. serratalhadensis in uniform, not organized in groups setulae of posterovenbtral corner of valves; from C. poppei in different shape of male postabdomen and short straight basal spine on male postabdominal claw; from C. anemae in smaller size and posteroventral corner of valves with over 80 setulae; from C. holdeni in greater size, and much smaller spine on basal segment of antenna exopodite.

Taxonomic notes: At the moment, it is impossible to be sure of studied material identity with with Central African populations used for original description of Alona bukobensis , but in any case their morphology fully agree with that of both Weltner (1896) and Sars (1916) descriptions. No material from Central Africa were available for the study. C. (C.) cf. bukobensis is closely related to C. (C.) rectangula , parthenogenetic females and these two species can be differentiated only by limb morphology. Due to a high level of similarity between these species, they are probably confused in all early studies on biodiversity of African Cladocera . During the last half-century, С. (С.) rectangula was recorded in Mali ( Dumont et al. 1981), Sudan ( Dumont et al. 1984), Nigeria ( Egborge et al. 1994), Cameroon ( Chiambeng & Dumont, 2005), but all these records lack morphological descriptions, and could belong to C. (C.) cf. bukobensis as well.

Distribution: So far C. (C.) bukobensis is recorded from East and South Africa, but probably distributed in the whole Subsahel Africa.

Figures

FIGURE 3. Coronatella (Ephemeralona) elegans (Kurz, 1875) comb. nov. from Laguna de El Hito, Cuenca, Castilla La Mancha, Spain. A-D, adult parthenogenetic female. A, labrum. B-C, postabdomen. D, antennule. E-F, antenna. G, juvenile male of instar I, postabdomen. H-I, juvenile male of instar II. H, postabdomen. I, antennule. J-L, adult male. J, postabdomen. K, postabdominal claw. L, antennule.

FIGURE 5. Coronatella (Ephemeralona) elegans (Kurz, 1875) comb. nov. from Mainzer Sand, Germany. A-C, adult parthenogenetic female. A, lateral view. B, postabdomen. C, IDL and ODL of thoracic limb I. D-G, adult male..D, lateral view. E, postabdomen. F, frontal part of thoracic limb I (copulatory brush seta not shown). G, IDL of thoracic limb I.

FIGURE 6. Coronatella (Coronatella) cf. bukobensis (Weltner, 1897) from Dune Pan, near Road 27, North of Blauwbergstrand, Cape Town, Republic of South Africa. A-B, juvenile females of instar I and II. C-I, adult parthenogenetic female. C, lateral view. D, ventral margin of valves. E, posteroventral angle of valves. F, head shield. G, head pores. H-I, postabdomen, J, antennule. K, ephippial female. L-O, adult male. L, lateral view. M, postabdomen. O, antennule.

FIGURE 7. Coronatella (Coronatella) cf. bukobensis (Weltner, 1897) from Dune Pan, near Road 27, North of Blauwbergstrand, Cape Town, Republic of South Africa, adult parthenogenetic female. A-B, lateral view. C, dorso-lateral view. D, postabdomen. E, postanal margin of postabdomen. F, postabdominal claw. G, antenna. H, setae of IDL of limb I.

FIGURE 8. Coronatella (Coronatella) cf. bukobensis (Weltner, 1897) from Dune Pan, near Road 27, North of Blauwbergstrand, Cape Town, Republic of South Africa.A-L, adult parthenogenetic female. A, labrum. B, antenna, C-D, limb I. E, limb II. F, exopodite of limb III. G-H, inner portion endite of limb III. I, exopodite of limb IV. J-K, inner portion of limb IV. L, limb V. M-O, adult male. M, thoracic limb I. N-O, IDL setae and copulatory hook of thoracic limb I.