Coronatella (Coronatella) novaezealandiae ( Sars, 1904 )

Sinev, Artem Y., 2022, Redescription of two Australian cladocerans of the subfamily Aloninae Dybowski & Grochowski (Cladocera: Anomopoda: Chydoridae), Zootaxa 5124 (2), pp. 188-204 : 196-201

Coronatella (Coronatella) novaezealandiae ( Sars, 1904)

( Figs. 6–8 )

Sars, 1904: 634–635, Pl. 34, Fig. 7, 7a–b ( Alona novae-zealandiae ); Smirnov, 1971: 352, Fig. 401–403 ( Alona rectangula novae-zealandiae ); Smirnov & Timms, 1983: 44–45, Fig. 45–46 ( Alona rectangula novae-zealandiae ).

Type locality. D’Urville Island , New Zealand

Type material. Non-existent.

Material examined. Over 100 parthenogenetic females, over 20 ephippial females, over 20 males from drainage ditch at Tolderol Swamp, near Lake Alexandrina , South Australia , coll. D.G. Frey in 6.11.1986, sample DGF- 7966 in the collection of Prof. D.G. Frey at the National Museum of Natural History, Smithsonian Institutes, Washington D.C., USA, general access number 403774 .

Description. Parthenogenetic female. General: In lateral view, body low oval ( Figs. 6A , 7A–C ) moderately compressed laterally. Maximum height at middle of body. Height-length ratio about 0.6 in adults. Dorsal margin convex, postero-dorsal angle rounded, postero-ventral angles broadly rounded. Posterior margin convex, ventral margin almost straight, antero-ventral angle rounded. Ventral margin ( Fig. 6B ) with 30–40 setae. About 10 anterior setae longer than others; next 10 setae short; posterior setae of moderate length, being the longest in the middle of the group. Postero-ventral angle ( Fig. 6C ) with over 70 setules not organized into groups. Posterior half of valves covered by moderately thick, sparsely spaced longitudinal lines.

Head relatively small, triangular-round in lateral view, rostrum short, pointing downward. Eye much larger than ocellus. Distance from the tip of rostrum to the ocellus 1.5 times greater than that between the ocellus and the eye.

Head shield with maximum width behind mandibular articulation, without any prominent sculpture ( Fig. 6D ). Rostrum short, broadly rounded. Posterior margin of head shield broadly rounded. Three narrowly connected major head pores ( Figs. 6E , 7D ), middle pore slightly smaller than others, located at the middle between the other two. PP less than 0.5 IP. Lateral head pores located at about 0.7 IP distance from midline, at the level of middle major head pore.

Labrum relatively large ( Figs. 8A–C ). Labral keel of moderate width (height/width ratio about 1.5), with a rounded or blunt apex. Anterior margin of keel convex or wavy. Posterior margin without clusters of setules.

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

Postabdomen ( Figs. 6F–G , 7E ) short, of moderate width, with almost parallel margins and broadly rounded dorso distal angle. Length about 2.4–2.6 heights. Ventral margin from almost straight to weakly convex. Basis of claws bordered from distal margin by clear incision. Distal margin convex. Dorsal margin with distal part about 1.5 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 ), preceded by 6–7 clusters of smaller elemental marginal denticles, decreasing in size basally, along postanal and anal margin. About 9 lateral fascicles of setules; 5 postanal fascicles wide, closely spaced, with setules longer than marginal denticles, with distalmost setule only slightly thicker than others. Postabdominal claw ( Fig. 7F ) weakly curved, of moderate length, as long as preanal portion of postabdomen. Basal spine long and thin, about 1/4 of length of claw; a cluster of 3–5 long setules located near its base.

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

Antenna short ( Figs. 6I , 7F ). Antennal formula, setae 0-0-3/1-1-3, spines 1-0-1/0-0-1. Basipod 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 endopod thin, reaching to the end of endopod. Seta arising from middle segment of endopod shorter than apical setae. Both apical segments with one shorter and two longer setules of similar thickness. Spine on basal segment of exopod much longer than middle segment. Spine from apical segments longer than apical segments.

Limb I ( Figs. 8D–F ) 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) rudimentary. Seta (3) as long as ODL seta; seta (2) slightly shorter than seta (3). Seta (2) with distal portion longer than basal one, armed with robust spinules, 2–3 basalmost spinules slightly thicker and longer than others. Seta (3) with distal portion two times shorter than basal one, armed with robust spinules, basalmost element is a thick long spine, two times shorter than distal portion of seta. Endite 3 with four setae of similar length. Endite 2 with seta (d) as long as setae of endite 3, seta (e) long, slightly shorter than limb itself, seta (f) about 2/3 length of seta (e). Endite 1 with 2 long 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. Six rows of thin long setules on ventral face of limb. Two ejector hooks of similar size. Maxillar process with a single seta.

Limb II ( Fig. 8G ). Exopodite elongated, with a seta almost as long as exopodite. Eight scraping spines armed with thin setules: scrapers (1–5) long, increasing in length distally, scraper (3) slightly thicker than neighbours; scrapers (6–8) short, of similar size. Distal armature of gnathobase with 4 elements. Filter plate with 7 setae, 2 posteriormost setae considerably shorter than others.

Limb III ( Figs. 8H–J ). Epipodite oval, without process. Exopodite quadrangular, with 6 setae. Seta (3) being longest, seta (5) about 1/3 length of seta (3), setae (1) and (6) about 1/5 length of seta (3), other setae very short. Setae (1–4) plumose, seta (5) armed with thick setules in distal portion, seta (6) with very short setulae in distal portion. Distal endite with three setae and sensilla located between bases of setae (2) and (3). 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 a elongated, slightly curved sensillum; the second a geniculated seta; two others are short spines with fused bases. Filter plate with seven setae.

Limb IV ( Fig. 8K–M ). Preepipodite setulated; epipodite oval, without process. Exopodite subquadrangular, with 6 setae. Seta (3) longest, setae (1) and (2) about 2/3 length of seta (3), seta (5) about 1/2 length of seta (3), setae (4) and (6) short. Setae (1–4) flattened, plumose, setae (5) and (6) slender, with short setules in distal portion. Inner lobe of limb IV with 4 setae ( Fig. 8L ); distalmost seta (1) slender, sharp, flaming-torch setae (2–4) with narrow basal portion, armed with 7–9 thin setules 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. 8N–O ). 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, and a rounded sensilla located between their bases. Filter plate absent.

Ephippial female ( Fig. 6J , 7G ) with body higher than parthenogenetic female; dorsal margin more convex than in parthenogenetic female, without depression between valves and head shield. Ephippium ( Fig. 7H ) yellow-brown in preserved specimens, with moderately developed egg locules, partially covered by weak polygonal sculpture and minute dot-like depressions.

Male. General. Body ( Fig. 6K , 7I ) low oval, height/length ratio about 0.6. Ocellus larger than in female.

Postabdomen ( Fig. 6L ) short, narrowing distally in postanal portion, with broadly rounded dorso-distal angle. Postabdominal claws located at small protrusion at the middle of convex distal margin. Ventro-distal angle welldefined, obtuse. Sperm duct openings located ventrally at the end of postabdomen. Preanal angle well-defined, more prominent than in female, postanal angle weakly defined. Distal part of postabdomen 1.5 times longer than preanal; anal portion slightly longer than postanal one. Clusters of short setules in place of marginal denticles; lateral fascicles of setules similar to those of female. Postabdominal claw 1.5 times shorter than that of female, without strong spines on the inner side. Basal spine long, about 0.3 length of claw.

Antennule ( Fig. 6M ) thicker than in female, with 10 terminal and 2 lateral aesthetascs. Lateral aesthetascs about 2/3 length of antennule, located near base of male seta, terminal aesthetascs almost as long as antennule. Male seta arising at 3/4 length from tip, about 1/3 of antennule length.

Thoracic limb I ( Fig. 8P–Q ) 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 setules. Inner distal lobe without seta (1), setae (2) and (3) much shorter and thinner than in female; seta (2) without any spines at the middle; seta (3) with small spine at the middle; distal portions of setae armed with thin setules; male seta curved, shorter than seta (3). Endite 3 with seta (1) thinner and longer than in female.

Size. Adult parthenogenetic female length 0.36–0.44 mm, height 0.24–0.27 mm. In ephippial female body slightly higher, largest specimen with length of 0.42 mm and height of 0.28 mm. Adult male length 0.32–0.34 mm and height 0.19–0.2 mm.

Differential diagnosis: C. (C.) novaezealandiae shares all diagnostic character of the subgenus C. ( Coronatella ), including short and thin seta on basal segment of antennal endopod, limb I with short accessory seta, endopodite II with long seta, and small size (see Sinev 2020b). C. (C.) novaezealandiae habitually similar to C. (C.) rectangula , but it clearly differs in morphology of IDL setae, in C. (C.) rectangula IDL seta (2) bears two strong spines followed by very short thin setules, while in C. (C.) novaezealandiae it is armed by robust setules with basalmost elements only a little thicker than others.

C. (C.) novaezealandiae differs from any species of the monacantha -group (Oriental C. (C.) acuticostata (Sars, 1903) , African C. (C.) hardingi (Brehm, 1957) , Neotropical C. (C.) monacantha (Sars, 1901) and C. (C.) undata Sousa, Elmoor-Loureiro & Santos, 2015 ) (see Sousa et al. 2015; Van Damme 2016; Sinev 2016) in absence of any type of denticles on posteroventral margin of valves, and from species of circumfimbriata -group (North American C. (C.) circumfimbriata (Megard, 1967) and South American C. (C.) serratalhadensis Sousa, Elmoor-Loureiro & Santos, 2015 ) (see Sinev 2009a; Sousa et al. 2015) in non-differentiated spinules on posteroventral corner of valves. C. (C.) novaezealandiae differs from East Asian C. (C.) trachystriata (Chen, Zhang & Liu, 1994) and Brazilian C. (C.) paulinae Sousa, Elmoor-Loureiro & Santos, 2015 (see Kotov et al. 2011, and Sousa et al. 2015), in short, not truncated rostrum, and in presence of a strong spine on IDL seta (3) of limb I. C. (C.) novaezealandiae differs from African C. (C.) holdeni (Green, 1952) (see Van Damme & Dumont, 2008a) in shorter spine on basal segment of antenna exopod; in the latter species is extremely thick and reaching to the end of apical segment. C. (C.) novaezealandiae differs from South American C. (C.) poppei (Richard, 1897) in male postabdominal claw with a short, weakly curved basal spine, while in C. (C.) poppei it is very long and sigmoid ( Sousa et al., 2015). C. (C.) novaezealandiae differs from African C. (C.) cf. bukobensis (Weltner, 1897) and Balkanian C. (C.) begoniae ( Sinev & López-Blanco, 2018) in longer and more massive spine on IDL seta (3), and in shorter distal portion of both IDL setae (2) and (3); in two latter species distal portion of seta (3) is almost as long as basal one, and distal portion of seta (2) is longer than basal one (see Sinev & López-Blanco 2018; Sinev 2020b).

Distribution: New Zealand and Australia (South Australia & Kimberley Region, Western Australia).

Figures

FIGURE 6. Coronatella novaezealandiae (Sars, 1904), parthenogenetic female (A–I), ephippial female (J) and adult male (K–M) from drainage ditch at Tolderol swamp, South Australia, Australia. A, parthenogenetic female, lateral view. B, ventral margin of valves. C, posteroventral angle of valves. D, head shield. E, head pores. F–G, postabdomen. H, antennule. I, antenna. J, ephippial female, lateral view. K, male, lateral view. L, postabdomen. M, antennule.

FIGURE 7. Coronatella novaezealandiae (Sars, 1904), parthenogenetic female (A–F), ephippial female (G–H) and adult male (I) from drainage ditch at Tolderol swamp, South Australia,Australia.A–B, parthenogenetic female, lateral view. C, frontolateral view. D, head pores. E, postabdomen. F, antenna. G, ephippial female, lateral view. H, frontolateral view. I, male, lateral view.

FIGURE 8. Coronatella novaezealandiae (Sars, 1904) parthenogenetic female (A–O) and adult male (P–Q) from drainage ditch at Tolderol swamp, South Australia, Australia. A–C, parthenogenetic female, labrum. D, thoracic limb I. E, ODL and IDL of limb I. F, IDL of limb I. G, thoracic limb II. H, exopodite of thoracic limb III. I–J, inner portion of limb III. K, exopodite of thoracic limb IV. L–M, inner portion of thoracic limb IV. N, thoracic limb V. O, inner lobe of thoracic limb V. P–Q, male thoracic limb I.