Leydigia (Neoleydigia) australis Sars, 1885

Kotov, Alexey A., 2009, A revision of Leydigia Kurz, 1875 (Anomopoda, Cladocera, Branchiopoda), and subgeneric differentiation within the genus, Zootaxa 2082 (1), pp. 1-84 : 30-38

IV. Leydigia (Neoleydigia) australis Sars, 1885

( Figs 107–111 , 116–161 )

Leydigia australis Sars, 1885, p. 35 –43, Pl. 7–8; Jolly 1967, Pl. K: fig. 9; Smirnov 1971, p. 462 –463, figs 577–578 (only Australian records); Shiel et al. 1982, Tab. 2; Smirnov and Timms 1983, p. 54; Shiel and Dickson 1995, p. 33; Smirnov 1995, p. 5; Griggs et al. 2001, fig. 1B (photo).

Not Leydigia australis Sars in Brehm 1964, p. 71–72; Chapman and Lewis 1976, p. 69, fig. 419.

Type locality. "The Centennial Park, near Sydney", New South Wales, Australia .

Possible type material (the labels lack exact information about locality, marked as " Australia "). 1 parth ♀ and 1 ♂, dissected on slides GOS F 18336 b–d; 9 parth. ♀♀, slide GOS F 9660; 6 parth. ♀♀, slide GOS F 9662 (bad condition); 40 parth. ♀♀., tube GOS F 18336 a; 1 ♂, tube GOS F 18337 .

Other material examined. Australia. Victoria: unknown locality, GOS F 9661 (bad condition); Lake Purrumbete, coll. 17.09.1970 by B. V . Timms , slide NNS MGU 2488 ; # 5249 from Mokoan Park, coll. 28.11.2001 by D. Nielsen at MDFRC , tube AAK 2002-015; New South Wales: Castlereagh River at Coonabarabran, coll. 10.08.1965 by B. V . Timms, tubes AAK 2003-028 and NNS 2000-043 (31º16'S, 149º17'E) .

Diagnosis. Parthenogenetic female. Body subovoid, maximum height in the middle or somewhat posterior to it, dorsal margin almost straight in posterior part, postero-dorsal angle well-defined, posterior margin in general convex, sometimes with a small depression. No coarse striation on valves, but a fine striation distinct. In anterior view, body significantly compressed laterally, dorsum like rounded triangle in section. Head relatively small, compound eye particularly small, ocellus of irregular shape, its size and shape variable, but always bigger than eye. PP = 4 IP, lateral head about 0.7 IP distance from midline. Labral keel subtriangular, posterior margin almost straight, with a group of long, fine setules, anterior margin convex, slightly undulating, with short setules in basal portion and lateral setules near posterior margin, no lateral groups on anterior margin. On valves, setae at middle of ventral margin with symmetrical setulation, their bases located submarginally, short setules between their bases. In posterior portion of margin, setae setulated slightly asymmetrically, posteriormost seta long. Submarginal setules of ventral portion of posterior margin fine, organized into successive series; in mid-dorsal portion longer and more sparsely distributed that setules in ventral portion A marginal membrane of fine 'setules' arises about 1/4–1/3 of distance along posterior margin from last marginal seta. Postabdomen elongate, of characteristic semicircular shape, with maximum height in the middle of postanal portion, Preanal margin shorter than anus, in general straight, with a system of small hillocks, preanal angle well defined, postanal angle from well-defined to smooth, postanal margin regularly arched from anus to well-defined dorso-distal angle, separated by deep depressions from base of claws. Postanal marginal short, with obscurely organised clusters of 4–5 series of marginal setules on anal margin. 14–16 fascicles of lateral setae, occupying most of margin, normally 4 setae in each fascicle in median part of margin, and marginalmost setae of each fascicle significantly larger then rest. Up to 6 setae in each fascicle in basal portion, about 6 fascicles of lateral setules on basalmost portion of postanal and anal margin. Postabdominal claw relatively long, only slightly curved, no setules at base of claw, no basal spine.

Antenna I elongated, not reaching tip of rostrum, body with 4 transverse rows of long setules and series of shorter, more robust setules at its tip. Sensory seta long, slender, arising 1/4 of way from distal end, a group of robust setules near its base. Largest aesthetasc about third part of appendage length, protruding behind tip of rostrum. Antenna II with 3–4 relatively long and stout spine-like setules on first, and 3–4 of these setules on second endopod segment. Apical swimming setae with basal and distal segments asymmetrically armed, no chitinous insertions within distal segments. Basal lateral seta short, distal lateral seta longer, but significantly shorter than apical setae.

Trunk limb I with ODL large, conical, with long seta with unilaterally setulated distal segment. IDL with 4 medial clusters of minute setules, and 3 marginal clusters of stout, relatively short setules, first IDL seta small, with few short setules distally; second and third IDL setae unequal in length, unilaterally setulated distally, endite 3 with relatively long seta 1 and small receptor near base, endite 2 with two longer soft setae (e–f) subequal in length, seta 2 short, naked, with sensillum near its base. Two ejector hooks of unequal size. Trunk limb II with small, ovoid exopodite, with a tuft of short, fine setules. Distalmost scraper with naked basal segment, on distal lobe with distal tuft of short setules and basal group of long setules. Trunk limb III exopodite trapezium-shaped, with 4 setae, seta 2 with distal segment armed with setules of two sizes, filter plate with distalmost and basalmost setae smaller than rest. On trunk limb IV, setae 1 and 2 short, armed with long, fine setules. Distalmost seta of filter plate with greatly inflated basal segment, all setae with inflated tips. Inner face of limb V, with short, blunt, fully setulated seta and long seta setulated only distally, a hillock near its base. Distal armature of gnathobase as a setulated lobe.

Ephippial female. Unknown.

Adult male. Body shape as in female, head large, rostrum long. Postabdomen elongated, shape as in female. Marginal denticles small, clearly organised in clusters. Penis completely absent, gonopores open on a low projection on ventral margin, some way from distal end of postabdomen. Antenna I more robust than in female, sensory seta arising 1/3 of appendage length from distal end, a group of robust setules near it, distally 13 'aesthetascs', one of them is, in reality, a male seta. Trunk limb I with thin, U-shaped copulatory hook, ODL as in female, IDL with male seta, and three setae of female type.

Size. Juvenile and adult parthenogenetic female 500–980 µm, adult male 460–490 µm.

Full redescription. Parthenogenetic female. General. In lateral view subovoid, low (body height/ body length = 0.56–0.66 in juveniles and 0.60–0.66 in adults), maximum height in the middle or somewhat posterior to it ( Figs 107 , 116–117 ). Dorsal margin uniformly curved in anterior part, almost straight in posterior part. Postero-dorsal angle well-defined, although rounded; posterior margin generally convex, sometimes with a slight depression in ventral portion, something like the 'step' in L. propinqua , but less obvious. Postero-ventral angle smoothly rounded; ventral margin slightly convex. No coarse striation on valves, but a fine striation distinct ( Fig. 142 ), also hexagonal reticulation (in reality, cell contours). 'Dots on valves' present, but they are not external structures. In anterior view, body significantly compressed laterally, maximum width in dorsal half, without dorsal keel, but like rounded triangle in section ( Fig. 118 ).

Head relatively small, triangle-round in lateral view, with short, blunt, downward pointing rostrum. Compound eye particularly small, ocellus of irregular shape, its size and shape variable, but always larger than eye, though never as much as 3 times (in contrast to description of Sars, 1885). Distances from tip of rostrum to ocellus and from ocellus to eye approximately equal. Head shield wide, maximum width in posterior half, in region of mandibular articulation, anterior portion with blunt rostrum, posterior portion a rounded triangle, with three major head pores with a particularly wide connection between them, PP = 4 IP ( Figs 119–120 ). Central pore somewhat narrower than anterior or posterior pore, located at the middle. Lateral head pores ( Fig. 121 ) about 0.7 IP distance from midline, at level of central major head pore.

Labrum with fleshy body, small distal plate, and large medial keel ( Figs 139–141 ). Distal labral plate short, setulated. Main body with lateral projections, and small setules distally. In lateral view, keel wide, triangular-ovoid, with rounded apex; posterior margin almost straight, with tuft of long, fine setules, anterior margin convex, sometimes very slightly undulated, with short setules in basal portion, a lateral group of setules near posterior margin, no lateral bunches at anterior margin.

Valves large, subovoid, with numerous setae on ventral margin, longest in middle and posterior portions. Anterior setae exactly marginal, slender, asymmetrically setulated with fine setules ( Figs 122–123 ), in middle of margin setae with symmetrical setulation, their bases located submarginally, short setules between their bases ( Fig. 124 ). Posterior setae setulated slightly asymmetrically, posteriormost seta long, no setules between bases ( Fig. 126 ). Posteriorly to the last marginal seta, a row of fine submarginal setules on inner face of valve, these organized into series ( Fig. 125 ); in region of incision on posterior margin (1/4–1/3 of posterior margin length from last marginal seta) setules become significantly shorter and located further from margin, then increase in size, setules in dorsal portion of margin therefore longer and more sparsely distributed than in ventral portion. Marginal membrane of fine 'setules' also present more dorsally ( Figs 127–130 ).

Thorax relatively long. Abdomen short, dorsal surface of segments with transverse rows of setules. Distal margin of basal and next abdominal segments inflated.

Postabdomen elongated, of characteristic semicircular shape, maximum height in the middle of postanal portion ( Figs 109–110 , 143–144 ). Ventral margin almost straight, with groups of minute setules. Preanal margin shorter than anus, with small projection for postabdominal setae posteriorly, in general straight, with a system of small hillocks ( Figs 111 , 145 ). Preanal angle well defined, postanal angle from well-defined to smooth. Postanal margin regularly arched from anus to well-defined dorso-distal angle, separated by deep depressions from base of claws. Each side of postabdomen with row of short postanal marginal denticles, obscurely organised in clusters ( Figs 146–147 ), passing evenly into 4–5 series of marginal setules on anal margin. On postanal margin, about 14–16 fascicles of stout lateral setae, occupying most of margin, decreasing in size basally, normally 4 setae in each fascicle in middle part of margin, and marginalmost setae of each fascicle significantly larger than the rest, up to 6 setae in each fascicle in basal portion. Fascicles of lateral setae merge gradually with 6 fascicles of lateral setules on basalmost portion of postanal and anal margin.

Postabdominal seta relatively long, markedly longer than anal plus preanal margin; its distal segment slightly shorter than basal one, and armed with long, densely located setules ( Figs 143–144 ).

Postabdominal claw shorter than preanal plus anal portion of postabdomen, gently curved, with a row of small setules along ventral margin ( Fig. 148 ). On lateral side, two successive series of slender setules along dorsal margin, setules of basal series long, distalmost setules not thicker than others, no small setules at claw base. No basal spine.

Antenna I ( Fig. 149 ) elongate, its distal end almost reaching tip of rostrum, body with 5 transverse rows of long setules and series of shorter and more robust setules at tip. Sensory seta long, slender, arising 1/4 of way from distal end, a tuft of robust setules near base, and a second group more basally on posterior surface. Nine relatively short aestetascs of varying size, largest about a third of appendage length, protruding behind tip of rostrum.

Antenna II ( Figs 108 , 150 ) relatively short. Coxal part with two sensory setae, and lobe with transverse row of fine, short setules. Basal segment robust, with transverse series of numerous, fine, long setules, rudimentary distal spine and series of minute setules at distal margin. Exopod longer than endopod, all segments cylindrical, with fascicles of setules; 3–4 long and stout spine–like setules on first, and 3–4 of these setules on second endopod segment.

Antennal formula, setae 0–0–3/1–1–3, spines 1–0–1/0–0–1. On both exopod and endopod three long apical swimming setae, all with basal and distal segments asymmetrically armed ( Fig. 151 ). No chitinous insertions within distal segments. Basal lateral seta short, distal lateral seta longer, but significantly shorter than apical setae. Spine on basal segment of exopod long, reaching middle of apical segment. Apical spines of exopod and endopod of subequal length, about 1.5 times as long as apical segments.

Trunk limb I ( Fig. 152 ) without accessory seta, ODL large, conical, bearing long seta with unilaterally setulated distal segment. IDL with 4 medial clusters of small setules, and 3 marginal clusters of stout, relatively short setules ( Fig. 153 ), and three bisegmented setae; first IDL seta small, with a few short setules distally; second and third of unequal length, unilaterally setulated distally.

Endite 3 with three soft setae (a–c), seta b shortest, a long stiff seta 1 anterior to them, a small receptor near base. On endite 2 seta d short, setae e–f large, subequal in length, a small, naked seta 2 with a sensillum near base on inner face of limb ( Fig. 154 ). Endite 1 with 2-segmented setae g–i, and a small, blunt seta 3. Fascicles of slender setules on inner face of limb, plus groups of longer and more robust setules at ventral margin. Two ejector hooks of unequal size. On limb base, a maxillar process as a lobe with a single row of setules.

Trunk limb II ( Fig. 155 ) with small, globular epipodite. Exopodite ovoid, small, without setae, but with a group of short, fine setules. Inner portion of limb ('endopodite') with eight scrapers. Distalmost scraper 1 with long setules distally, naked basal segment, on distal lobe with distal tuft of shorter setules and basal group of longer setules. A series of small projections posteriorly to distal scrapers. Portion of gnathobase bordering 'endopodite' somewhat inflated, and densely setose. Distal armature of gnathobase with four setae, filter plate with seven setae, distalmost with inflated basal segment.

Trunk limb III with globular epipodite. Exopodite trapezium-shaped, with two lateral setae of subequal size ( Fig. 156 : 3–4), and two distal setae (1–2) of unequal size and different armature, seta 2 with distal segment armed with setules of two sizes. In reality, this seta has 4 rows of setules, arranged as in Fig. 157 . Distal endite with three setae ( Fig. 156 : 1–3), distalmost (1) and middle one (2) stout, their distal segments with minute setules, basalmost (3) asymmetrically armed distally. Small sensillum near each of setae 2 and 3. Basal endite with four setae, armed with fine, relatively long setules distally, bottle-shaped sensillum near seta 1. On posterior limb face, four soft setae, all armed with fine setules.

Distal armature of gnathobase with very thick, bottle-shaped sensillum, long, slender seta, with long setules distally, and two smaller setae, with a group of long setules near them. Filter plate of six setae, distalmost and basalmost smaller than rest.

Trunk limb IV with setose pre-epipodite and globular epipodite. Exopodite wide, subovoid, with six setae ( Fig. 158 : 1–6). Setae 3–6 of decreasing size, with similar armature of long, fine setules, all in same plane, setae 2 and specially 1 shorter, with long, fine setules ( Fig. 159 ).

Inner portion of limb IV with four marginal setae ( Figs 158, 160 : 1–4). Distalmost seta 1 stout, with minute setules distally, setae 2–4 with inflated basal segments and slender distal segments, both unilaterally setulated. Slender sensillum near seta 2. On posterior face of limb, three soft setae (a, c–d) and a straight, trilobed sensillum (b), that is a member of row of soft setae also. Distal armature of gnathobase with thick, low, bottle-shaped sensillum, a long 2-segmented seta, with distal and basal segments unilaterally setulated, a small hook distally, and short receptor on anterior limb face. Filter plate with five setae, distalmost and basalmost with slightly inflated basal segment, all setae with inflated tips.

Trunk limb V with setose pre-epipodite, and subovoid epipodite. Exopodite large, subovoid, with four densely setulated setae ( Fig. 161 : 1–4), distally only a row of long setules. Inner portion of limb as elongated, flat lobe, with setose inner margin and group of particularly robust setules distally. On inner face, a short, blunt, fully setulated seta and long, seta setulated only distally, a hillock near its base. Distal armature of gnathobase a setulated lobe, two setae in 'filter plate'.

Ephippial female. Unknown.

Adult male. Only two males were available.

General. Shape as in female (body height/ body length = 0.63), but slight incision between head and valves ( Fig. 131 ). Head larger and rostrum longer than in female, major head pores as in female ( Fig. 132 ) lateral head pores at IP distance from midline. Anterior margin of labrum with short setules ( Fig. 133 ). No abdominal projections.

Postabdomen elongated, general shape as in female ( Fig. 134 ). Marginal denticles small, organised in clusters. About 14 lateral fascicles of setae, 4 setae per cluster in middle, only 2 in basal portion; about 6 lateral fascicles of setules in basal portion of postanal and anal regions ( Fig. 135 ). Postabdominal claws somewhat shorter than in female ( Fig. 136 ). No penis, gonopores open on a low projection on ventral margin, some way from distal end.

Antenna I ( Fig. 137 ), more robust than in female, and not projected significantly beyong tip of rostrum (in contrast to description of Sars 1885), with four transverse series of short setules and row of shorter, more robust setules distally, sensory seta arising about 1/3 of way from distal end, with group of robust setules near it, distally 13 'aesthetascs', one of them is, in reality, male seta, as in L. leydigi (see Kotov 2003). Antenna II: as in female.

Trunk limb I with thin, U-shaped copulatory hook, with 3 ridges distally, ODL as in female, IDL with male seta, and three setae of female type ( Fig. 138 ). Limb inflated near hook and provided with copulatory brush consisting of long, stout setules. Copulatory brush setae longer than smallest IDL seta, with bottleshaped basal part.

Size. Juvenile and adult parthenogenetic females from unknown locality in Australia (possible types) 500–760µm (n = 40), adult male, 490 µm (n = 1); parthenogenetic females from Castlereagh River 635–890 µm (n = 16). According to Sars (1885), "length of full-grown female 0.84 mm, of male 0.46 mm".

Differential diagnosis. In L. australis , postabdomen shape, four setae (without a rudiment of fifth seta) on exopodite III, and, especially, the absence of a penis in the adult male are unique in the genus. Only two species of the subgenus, L. australis and L. propinqua , have short setules on the anterior margin of the labral keel.

Taxonomical notes. The descriptions of Sars (1885) was detailed and accompanied by realistic pictures. The absence of robust (large-scale) striation on the valves, short setulation of the anterior margin of the labrum, numerous smooth hillocks on the preanal margin of the postabdomen, well-defined dorso-distal angle of the postabdomen, four setae on exopodite III, and the absence of a penis in the adult male were clearly represented. Although postabdomen shape only was used for determination of this species by subsequent authors, its understanding during the 20th century was in agreement with Sars' ideas. Only Chapman and Lewis (1976) most probably described L. laevis under this name. Brehm's (1934) record from Africa also seems to be a misidentification.

Alona australis var. ceylonica Daday, 1898, p. 41 –43, figs 19a–c was described from Sri Lanka, and reported by several subsequent authors ( Gurney 1907; Gurney 1916; Bär 1924; Fernando 1980; Fernando & Kanduru 1984). Smirnov (1971) regarded L. australis ceylonica as a valid subspecies of L. australis . In fact, the taxon described by Daday (1898) is not similar to L. ciliata , the most common species in tropical Asia. Most probably, this is a valid species, but I did not see it, and refer to it provisionally as incerta sedis.

Distribution. L. australis is found only in Victoria and New South Wales, Australia, but is relatively common there.

Figures

FIGURES 107–115. 107–111. Leydigia australis, parthenogenetic female from tube GOS F 18336a, possibly type material of G. O. Sars from unknown locality in Australia. 107–108. Adult and its antenna II. 109–111. Postabdomen and its preanal margin. 112–115 Leydigia macrodonta, lectotype, parthenogenetic female from slide GOS F9222, marked as "S.A.Mus. I", Republic of South Africa. 112–113. General view and head. 114–115. Distal and basal portion of postabdomen. Scale bar denotes 100 µm.

FIGURES 116–138. Leydigia australis from unknown locality in Australia, female from tube GOS F 18336a (116, 118, 122–124, 126, 130) and male from slide GOS F 18336d (131–138), possible type material of G. O. Sars; females from Castlereagh River at Coonabarabran, New South Walles, Australia, coll. 10.08.1965 by B. V. Timms (117, 119–121, 125, 128–129). 116–118. Parthenogenetic female in lateral and anterior view. 119–121. Head shield and dorsal head pores. 122–123. Setae at anterior portion of valve margin. 124. Setae at middle of ventral margin. 125–128. Armature of postero-ventral and middle portions of valve in inner view. 129–130. Postero-dorsal portion of valve margin. 131–133. Adult male, its dorsal head pores and labral keel. 134–136. Postabdomen, armature of postanal margin, and its distal portion. 137–138. Antenna I and limb I. Scale bar denotes 100 µm.

FIGURES 139–151. Leydigia australis, parthenogenetic female from unknown locality in Australia, possible type material of G. O. Sars (141, 144, 146–148), and from Castlereagh River at Coonabarabran, Australia (139–140, 142–143, 145, 149–151). 139–141. Labrum. 142. A fragment of valve surface. 143–145. Postabdomen and its preanal margin. 146–148. Its postanal margin and distal portion. 149–151. Antenna I, antenna II and its apical swimming seta. Scale bar denotes 100 µm.

FIGURES 152–161. Leydigia australis, thoracic limbs of parthenogenetic female from unknown locality in Australia, possible type material of G. O. Sars. 152–154. Limb I, its distal portion and endites 1–2. 155. Limb II. 156–157. Limb III and largest seta of its exopodite in transverse section. 158–160. Limb IV, two distalmost setae of its exopodite, and inner limb portion. 161. Limb V. Scale bar denotes 100 µm.