Moina australiensis Sars 1896
Creators: name: Neretina, Anna N.
name: Kirdyasheva, Anna G.
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Branchiopoda
Diplostraca
Moinidae
Moina
Moina australiensis

description: Moina australiensis Sars, 1896
(Figs. 1–10, 11A, B)
Moina australiensis Sars 1896: p. 18 –24, pl. 3, fig. 1–11.
Moina australiensis in Brehm 1953: p. 6 –9, fig. 2a–e.
Moina australiensis in Goulden 1968: p. 48 –51, fig. 21a–j.
Etymology. Sars named this species in honor of Australia, the continent where it was found (Sars 1896).
Type locality. Sydney, New South Wales, Australia (Sars 1896).
Type material. Potential author’s type material is kept at Zoological Museum, Oslo, Norway (GOS F 19249 and 19250).
Material examined from terra typica, Australia. Over 100 parthenogenetic females, 50 ephippial females and 20 males from a pond (S36.365645°, E148.934131°) near Carrolls Lake, limnetic, 10 km E Berridale, New South Wales, Australia, coll. 13.05.1975 by B.V. Timms, NNS-1997-217; over 100 parthenogenetic females, 50 ephippial females and 30 males from Boundary Lake (S36.538924°, E149.119192°), 18 km W Nimmitabel, near Cooma, Monaro Table land, New South Wales, Australia, coll. 14.05.1975 by B.V. Timms, NNS-1997-223.
Short diagnosis. Species of large size for the genus (length of adult parthenogenetic female up to 1.30 mm). Parthenogenetic female with body typical for the genus. Head and valves covered by fine hairs. Head without rostrum and head pore, ocellus absent. On inner side of valve, setulae near ventral setae are grouped into prominent bunches. Preanal and postanal margins of postabdomen covered by fine, relatively long hairs. Lateral side of postabdomen with a row of denticles decreasing in size towards tip. Antenna I relatively thick, its length almost five diameters of base. Structure of antenna II, maxilla I and thoracic limbs as for the genus. Ephippium darkbrownish, containing two resting eggs. Its dorsal chitinous plate wrinkled. Macrosculpture of ephippium represented by protruding knobs, some of them rugged. Male with elongated body. Gonopore opening in ventral surface of postabdomen near base of claws. Antenna I long, with four bisegmented hooks of similar size. Thoracic limb I with a long exopodite. Stiff seta 1 of male limb I having more thick basal segment than in female.
Redescription. Parthenogenetic female (Figs. 1 A–F, 2A–K, 3A–I, 4A–G, 5A–I, 11A–B). General. In lateral view, body broadly ovoid (Fig. 1A) or subovoid (Fig. 1B), maximum height in body middle (body height/length ratio about 0.85 in adults). Body shape may vary significantly due to increasing of brood pouch volume during development of embryos (Figs. 1 A–B). Dorsal margin convex, with a deep depression between head and valves. Posterodorsal angle broadly rounded, posteroventral angle well visible, triangular. Anteroventral angle broadly rounded (Figs. 1 A–B). Fine short hairs on head and valves (Figs. 1A, C, 4B).
Head (Figs. 1 A–D, 4A, 11A) relatively large, broadly ovoid in lateral view (Figs. 1 A–C, 4A), without a rostrum, and with a distinct supraocular depression (Fig. 1A, 11A). No ocellus near base of antenna I (Figs. 1 A–C, 11A). A shallow dorsolateral depression in posterior portion of head. Lateral, dorsal and frontal head pore absent. Dorsal and lateral surfaces of head covered by fine short hairs (Figs. 1A, C, 11A).
Labrum (Figs. 1 E–F) with fleshy main body, its ventral margin convex, labral plate densely setulated.
Valves (Figs. 1 A–B) large, broadly ovoid. Ventral margin of valve broadly rounded, convex, with short setae, decreasing in size posteriorly (Figs. 2 A–B, 3A–B). Posterior portion of ventral margin with a row of fine, exactly marginal setules (Figs. 3 B–D, 4C–F). Armature of this portion is significantly different in the different regions (Fig. 4C). Bunches of setulae adjoin to ventral setae (Figs. 2 B–C, 3B–C, 4D–E, 11B); posterior setule in each bunch especially thick and long (Figs. 4 D–E). Setulae located closer to the dorsal margin subequal in thickness, decreasing in length posteriorly (Figs. 2D, 3D, 4F). A setulated spine on inner face of valve near posteroventral angle (Figs. 2E, 3E, 4G). On outer surface valves show prominent sculpture represented by elongated polygons (Figs. 4B) and fine short hairs.
Thorax (Figs. 1 A–B) long; abdomen relatively short.
Postabdomen (Fig. 2F) triangular, elongated, conically narrowing distally. Postabdomen length/height ratio about 2.8. Ventral margin almost straight, covered by rows of fine setulae (Figs. 2 F–G, 3F). Anus located almost in middle of postabdomen. Preanal margin long, broadly convex (Fig. 2F), covered by fine relatively long hairs. Anal margin almost straight, almost two times shorter than postanal margin. Preanal and postanal angles smooth. Postanal margin covered by bunches of fine hairs (Figs. 2 F–G, 3F). Basis of claws not inflated (Figs. 2 F–G, 3F–G). In lateral face, postanal margin bears a large bident tooth (its branches always unequal in length) and a row of 11– 13 large, triangular plumose teeth (Figs. 2 F–G, 3F).
Postabdominal seta (Fig. 2F) long, subequal in length to postabdomen; its distal segment covered by fine hairs.
Postabdominal claw (Figs. 2G, 3F) robust, long (almost subequal in length than postanal margin), slightly curved, with particularly sharp tip. Its outer lateral side with a row of denticles decreasing in size towards tip. Prominent group of larger denticles near base of claw. Ventral margin of claw with about several denticles in its basal portion.
Antenna I (Figs. 2H) almost cylindrical, covered by concentric rows of minute denticles and fine long hairs. Antennular sensory seta slender, arising somewhat proximally to middle of antennular body on its lateral face. Nine short aesthetascs subequal in length.
Antenna II (Figs. 2 I–J) long. Coxal part with two setulated sensory setae subequal in length. Basal segment robust, with a short distal spine at outer face and a long seta at inner face (Figs. 2 I–J). Antennal branches elongated, four-segmented exopod slightly longer than three-segmented endopod, all their segments cylindrical, with concentric rows of fine denticles and long fine hairs. Antennal formula: setae 0-0-1-3/1-1-3, spines 0-1-0-1/0-0-1. Apical and lateral setae of endopod and exopod have similar armature: all with basal and distal segments bilaterally covered by fine setulae (Fig. 2J). Spine on second exopod segment has same length as spine between exopod and endopod branches (Fig. 2I). Apical spines of exopod and endopod subequal in length (Figs. 2 I–J).
Maxilla I (Fig. 2K) with three long densely setulated setae.
Thoracic limbs (Figs. 3 H–I, 5A–I): five pairs.
Limb I (Figs. 3 H–I, 5A) with elongated corm, inner distal lobe, or endite 5 (sensu Kotov 2013), with a single anterior seta (Fig. 5A: 1), bearing short setulae, and two soft setae (Fig. 5A: a, b). Armature of posterior soft setae similar in all limbs: both their segments armed with fine, long setulae (Fig. 5A: a–h). Endite 4 with a single, relatively short anterior seta (Fig. 5A: 2), and a single posterior seta (Fig. 5A: c). Endite 3 with two posterior setae (Fig. 5A: d–e), without anterior setae. Endite 2 with three posterior setae (Fig. 5A: f–h). Two ejector hooks of remarkably different size. No maxillar process (endite 1) on limb base.
Limb II (Figs. 5 B–E) with ovoid epipodite, limb distal portion as a large lobe bearing a large soft seta and a small lateral seta (Fig. 5B); three endites bearing four soft posterior setae (Figs 5B: e5–e3), and two small setae of unclear homology near gnathobase. Gnathobase with two clear rows of setae: four anterior setae; a single long seta (Fig. 5C: 1) near the beating seta (marked via arrows without number on Figs. 5 B–C) and two setae in the basal corner of the gnathobase (Figs. 5C, D: 2–3), increasing in size distally; and nineteen posterior setae (Figs. 5 B–C, E: a–s) of the gnathobase “filter plate”.
Limb III (Figs. 5 F–G) with setulated preepipodite and ovoid epipodite. Exopodite large, ovoid, bearing four distal and two lateral setae (Fig. 5F). Inner distal portion of limb with three endites: endite 3 with a single anterior (Fig. 5G: a) and a single posterior seta (Fig. 5G: 1); endite 2 with single anterior (Fig. 5G: 2) and two posterior setae (Fig. 5G: b–c); endite 1 with a single short anterior (Fig. 5G: 3) and four posterior setae (Fig. 5G: d–g). Long anterior seta (Fig. 5G: 4) located in the distal corner. All other parts of limb inner margin represent a single large lobe (probably this is a gnathobase (Kotov 2013)), bearing numerous setae (Fig. 5G: endite 5).
Limb IV (Fig. 5H) smaller than limb III. Exopodite, similar to that in limb III, also bearing four distal and two lateral setae. Inner distal portion of this limb with two endites: endite 2 with an anterior seta (Fig. 5H: 1) and a posterior seta (Fig. 5H: a); and endite 1 with an anterior seta (Fig. 5H: 2) and two posterior setae (Fig. 5H: b–c). The major portion of the limb inner margin is the gnathobase filter plate (Kotov 2013), consisting of numerous setae (Fig. 5H: endite 5).
Limb V (Fig. 5I) with large ovoid epipodite. Exopodite broadly ovoid, provided with a long distal and a small apical seta. Inner limb portion as a flat, setulated subrectangular lobe; and two setae unequal in size (Fig. 5I: 1, 2).
Ephippial female (Figs. 6A, 7A, 8 A–H, 9A–E). General body shape and appendages of ephippial female appearing similar to those of parthenogenetic female (Figs. 8 A–D), but with dorsal portion modified into ephippium, containing two resting eggs (e.g. Fig. 6A). Dorsal part of valves with reinforced dorsal wrinkled chitinous plate (Figs. 7A, 8E, 9 A–E). In dorsal view, this plate has the same thickness almost all over the ephippium (Fig. 9B). Ephippium (after formaldehyde fixation, living animals were not investigated by us) darkbrownish (Fig. 7A). Macrosculpture of ephippium represented by protruding knobs, well-recognizable both under light (Figs. 6A, 7A) and scanning electron (8E–H, 9A–E) microscopes; such knobs near anterior, ventral and posterior portions of ephippium significantly lower than in the central portion (Figs 8E, H, 9 A–C). Microsculpture as tiny irregular wrinkles on knobs, visible only under scanning electron microscope (Figs. 8 F–H, 9D–E).
Male (Figs. 6 B–K, 7B–D, 10A–C). General. In lateral view body ovoid, more elongated as compared to female (body height/length about 0.56) (Fig. 6B). Dorsal margin of valves slightly elevated above head, posteroventral angle distinct (Fig. 6B).
Head (Figs. 6 B–D) more elongated than in female. Labrum similar to females, with large, setulated distal labral plate (Figs. 6 E–F). Head pores absent. Compound eye large. Ocellus absent.
Valves (Fig. 6B) ovoid, longer than that in female, with short setae, decreasing in size posteriorly, along ventral margin (Figs. 6G). Posterior portion of ventral margin with successive series of fine, exactly marginal setulae (Figs. 6G).
Thorax (Fig. 6B) relatively long.
Abdomen (Fig. 6B) short.
Postabdomen (Figs. 6 H–I) generally as in female, with a large bident tooth distally (distal branch always significantly large than proximal branch), and row of about 9–11 large, triangular plumose teeth (Figs. 6 H–J). Gonopores open in ventral surface of postabdomen near base of claws (Figs. 6 H–J).
Postabdominal setae (Figs. 6B, H) almost two times longer than postabdomen. Its distal segment significantly longer than proximal one (Fig. 6H).
Antenna I (Figs. 6 C–D) very long and regularly curved, covered by tiny hairs and rows of small denticles (Figs. 6 C–D). Antennular sensory seta long, arising from first quarter of antennular body. Male seta more robust, located near sensory seta. Apical tip of antennular body separated into two parts: first one with nine short aesthetascs (Figs. 6 C–D, K, 7B–C, D), second one with four bicuspid hooks (Figs. 6 C–D, K, 7B–C, D).
Limb I (Figs. 10 A–C) essentially similar to parthenogenetic female, but with large, curved copulatory hook (Figs. 10 A–B) and long exopodite (Figs. 10 A–C). Exopodite bisegmented, with proximal portion covered by fine relatively long hairs and distal portions with small fine denticles (Fig. 10C). Stiff seta 1 (Figs. 10 A–B) has the basal segment thicker than in females.
Size. Adult parthenogenetic females up to 1.30 mm in length; ephippial females up to 1.10 mm in length; adult males up to 0.80 mm in length.
Variability. No significant variability between investigated populations was found.
Taxonomic remarks. Among Australian moinids, only Moina tenuicornis Sars, 1896 may be considered as a congener of M. australiensis (Figs. 11 A–F). Both species share some fine, but very consistent morphological features (see detailed comparison in Goulden (1968) and Smirnov (1976)), among them: (1) lack of a dorsal head pore (Figs. 11A, C); (2) distal portion of postanal margin with bunches of fine hairs (Figs. 2F, G, 3F, 8B, 11 D–E); (3) ephippium with two resting eggs. But they reliably differ from each other in: (1) proportions of antenna I and (2) structure of inner margin of valves. M. australiensis has a relatively short antenna I, with a length reaching almost five diameters of the base (Figs. 11A), while M. tenuicornis has elongated antenna I, with a length reaching eight diameters of base (Figs. 11C). In M. australiensis setulae near ventral setae are grouped into bunches (Fig. 11B), while in M. tenuicornis these setulae form a uniform row (Fig. 11F).
Ecology and distribution. M. australiensis was found to date in brackish water lakes with low turbidity (Timms 1993) and flooded rock holes with a broad range of physicochemical characteristics (Bayly et al. 2011). At the same time, M. tenuicornis was found in sewage ponds (Wellington, New Zealand), characterized by slightly alkaline water, dissolved oxygen concentration more than of 6 mg /liter and high concentrations of organic substances (Vidal 1973). Relatively similar conditions plus especially high turbidity were reported by Shiel et al. (1982). Probably, these two species differ in their ecological requirements, but further investigations are required on their preferences. Except for Vidal (1973), other publications with detailed descriptions of ecological conditions do not contain figures or microphotographs of investigated populations (Shiel et al. 1982; Timms 1993, 1997; Bayly et al. 2011) and we could not check accurateness of author’s identification.
According to Goulden (1968) and Smirnov (1976), distribution ranges of M. australiensis and M. tenuicornis are mainly restricted to Australia. There are no reliable data on occurrence of these taxa in other parts of Australasia or in the Oriental zone. Sars’ record of M. tenuicornis in South Africa (Sars 1916: pl. XXXV 2, 2a, 2b, 2c) seems doubtful in the frame of the continental endemism concept (Frey 1982), although a specimen illustrated by him has a relatively long antenna I (Sars 1916: pl. XXXV 2, 2a). Some other authors have recorded M. tenuicornis in Africa (e.g. Smirnov 1976; Clarke & Rayner 1999; Seaman et al. 1999). They pictured specimens with a relatively long antenna I as well (e.g. Seaman et al. 1999: fig. 4.8.: p), but, unfortunately, their descriptions lack data on the head pores, armature of valve, structure of distal portion of postanal margin and ephippium ornamentation.
description: Published as part of Neretina, Anna N. & Kirdyasheva, Anna G., 2019, A redescription of Moina australiensis Sars, 1896 (Cladocera: Moinidae) with short notes on Australian moinids, pp. 161-179 in Zootaxa 4577 (1) on pages 163-175, DOI: 10.11646/zootaxa.4577.1.10, http://zenodo.org/record/2628516