Leydigia (Leydigia) leydigi (Schoedler, 1863)

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 : 12-14

I. Leydigia (Leydigia) leydigi (Schoedler, 1863)

Lynceus quadrangularis O. F. Müller in Leydig 1860, p. 221 –223, Pl. 8: fig. 59;

Alona leydigii Schoedler, 1863, p. 27 ; P.E. Müller 1867, p. 174; Hellich 1877, p. 84 –85, fig. 41; Matile 1890, p. 145, fig. 29; Stingelin 1895, p. 243 –244;

Leydigia quadrangularis (Leydig) in Kurz 1875, p. 58 –59, Pl. 2: fig. 2; Sars 1890, p. 46; Lilljeborg 1901, p. 494 –499, Pl. 60: figs 6–17, Pl. 61: figs 1–3; Daday 1903, p. 62; Birge 1918, p. 721; Bigelow 1922, p. 120, Pl. 2: fig. 17; Volterra D'Ancona 1933, p. 47 –48, figs 5–8; Leonard and Ponder 1949, p. 191, Pl. 4: fig. 25; Pennak 1953, p. 374, figs 236B–C; Pennak 1978, p. 379, fig. 266B–C; Flössner 1972, p. 325, fig. 153; Dumont 1989, p. 139.

Leydigia leydigi ( Schödler, 1863) in Keilhack 1909, p. 90, figs 169–170; Spandl 1923, p. 28 –29, fig. 1a–b; Bowkiewicz 1926, p. 59; Krasnodebski 1937, p. 364; Behning 1941, p. 288 –290, fig. 119; Motaş and Orghidan 1948, p. 128, fig. 7; Frey 1959, p. 37, figs 15–18; Scourfield and Harding 1966, p. 49, fig. 8A; Frey 1962, p. figs 15–18; Šrámek- Hušek et al. 1962, p. 355–356, fig. 132; Herbst 1962, p. 90, fig. 71; Manuilova 1964, p. 220, fig. 107; fig. 25; Scourfield and Harding 1966, p. 38, fig. 82; Smirnov 1967, p. 558, Pl. 15: figs 1–6; Fryer 1968, p. 362 –272, figs 139–147; Smirnov 1971, p. 450 –454, figs 554–558; Prószyṅska 1978, p. 67–68; Sloka 1981, p. 88, fig. 66; Hann 1981, Tab. 1; Chengalath 1982, Tab. 1–2, 1987, p. 37; Ibrasheva and Smirnova 1983, p. 100, fig. 32 (after Smirnov, 1971); Margaritora 1983, p. 129, figs 83D–H, 84C; Negrea 1983, p. 320 –322, fig. 131; Balvay 1984, p. 234; Yoon and Kim 1993, p. 381 –385, figs 1–2; Hollwedel 1995, p. Tab. 1; Røen 1995, p. 249–251, fig. 115; Alonso 1996, p. 363 –365, fig. 163; Flössner 2000, p. 353 –355, fig. 130A–K; Hollwedel 2001, 2002: Tab. 1 –3; Kotov 2003, p. 148–161, figs 1–76.

? Leydigia leydigi in Chiang Shieh-chih and Du Nan-shan 1964, p. 210–211, fig. 141A–C.

Leydigia quadrangularis var. wojnowiensis Dybowski et Grochowski, 1895, p. 150 (Nomen nudum); 1898, p. 49–51, fig. 8.

? Leydigia quadrangularis var. leopolitana Dybowski et Grochowski, 1895, p. 150 (Nomen nudum).

Type locality. Not reported precisely by Schödler, but all water bodies studied by him were from Berlin City or its vicinity ( Forró 1984), Germany .

Type material. Not present in Schödler's collection in the Zoologisches Museum für Naturkunde, Humboldt-Universität, Berlin, Germany ( Forró 1984) .

Material examined. Russia (Asian): Vikhoreva River, near Ust' - Ilimsk water Reservoir, collector unknown, AAK 2003-001 ; and Lake Srednee, near Baikal-Lena Bay , coll. 30.08.1999 by N. G. Sheveleva, NMK 2168 ; Lake Khanka , border with China, coll. 11.07.1990 by E. I. Shornikov . Japan: Lake Sone-numa near Lake Biwa , coll. 12.12.2001 by M. Nishino and A. Ohtaka, AAK 2002-019 . USA: A pond in Buffalo , New York, coll. 16.06.2004 by A. A. Kotov, AAK 2005–206 ; Swan Pond, Long Island , New York, coll. 06.2004 by D. J. Taylor & A. A. Kotov, AAK 2005–215 .

Material examined earlier. See Kotov (2003) for list of material from Great Britain, Germany, Poland, Italy, Hungary, Norway, European Russia, Canada.

Diagnosis. Female. Body ovoid to triangular-rounded, maximum height in posterior half, dorsal margin slightly curved to almost straight in posterior part, postero-dorsal and postero-ventral angles rounded, although defined; in anterior view, body less compressed laterally than in most species, dorsum rounded in section. No coarse and fine striations on carapace. Eye smaller than ocellus. Head shield wide, PP = 3 IP, lateral head pores about 0.5–0.7 IP distance from midline at level of central major head pore or somewhat posteriad. Labral keel wide, triangular-rounded, with well-defined apex, without setules at posterior margin, and with short setules on anterior margin, 2–3 series of medium-sized setules on sides. Setae in middle of ventral margin of carapace with short setules, rudimentary setules between their bases, in its posterior portion these setae armed slightly asymmetrically. Posterior to last marginal seta, a submarginal row of setules on inner face of entire posterior margin of valve, in region of postero-ventral angle these are fine and dense, located close to margin, while in middle of margin somewhat more robust and sparse, located far from margin; marginal membrane with minute setules.

Postabdomen broad, robust, preanal margin short, straight, provided with variable number of shallow incisions, sometimes not visible. Preanal angle well defined, while postanal angle ill-defined or absent. Postanal margin uniformly arched, separated from base of claws by shallow incision, distal margin or angle absent. Postanal marginal denticles organised in about 16–18 clusters, but in some specimens these clusters not distinguishable within the row. 12–14 fascicles of relatively short lateral setae, decreasing in size baslly, in middle 3–4 setae in each fascicle, distalmost longest, but next and third setae only slightly shorter. About 10–12 fascicles of lateral setules on basal half of postanal and anal margin. Postabdominal claw short (somewhat shorter than anal plus preanal portions) slightly and gently curved, basal spine stout, with pointed tip, not adpressed to claw, as long as claw diameter at base, or longer, 2–3 setules on claw near its base.

Antenna I not reaching tip of rostrum, with 4 transverse rows of sparce, relatively short setules on anterior face, no setules at distal end. Antennular sensory seta relatively short, arising at distance of 1/3 of antennule length from distal end, longest aesthetasc half of antennule length. Antenna II with short coxal setae, 3–5 spine-like setules on second and third endopod segments, apical swimming setae with basal segments bilaterally armed with fine setules, and distal segments with robust setules on one side and short setules on other side. Basal and distal lateral setae of unequal size, both shorter than distal setae. No insertions within distal segments of apical or lateral setae.

Trunk limb I with ODL large, elongate, without setules. IDL with three medial clusters of small setules, and 3 marginal clusters, basal and middle of moderate-sized setae, the distal with short seta, first IDL seta small, with numerous, short setules distally; others subequal in length, but setulated in different manner. Endite 3 with a long, naked seta 1, endite 2 with seta 2 small, endite 1 without seta 3, a sensillum on each endite, two ejector hooks of similar size. On limb II, exopodite small, ovoid, with bundle of fine, short setules, distal scraper on limb II with naked basal segment, on special lobe, with basal cluster of long setules and distal cluster of shorter setules. On limb III, exopodite with three large lateral and two large distal setae, seta 2 armed bilaterally with short setules, in filter plate distalmost seta with inflated basal segment. Exopodite of limb IV with setae 1 and 2 slender, armed with short setules, distalmost seta of filter plate with inflated basal segment, all setae with inflated tips. On limb V gnathobase a setulated hillock.

Length 410–935 µm.

Ephippial female. In anterior view body compressed laterally, expanded in region of egg, and low, thick dorsal keel. Hexagonal 'reticulation' is an illusion, these are only contours of epidermis cells, no distinct border between ephippium and rest of valves.

Length 655–820 µm.

Adult male. Body more triangular than in female, but with approximately same height, hexagonal reticulation visible on valves. Labral keel with obscure ridges on lateral sides, and associated fascicles of setules.

Postabdomen elongate, ventral margin with step in region of penis, distal margin well-defined. 17–19 clusters of marginal denticles in postanal and anal regions, size as in female, 10–14 lateral fascicles of setae, about 10 lateral fascicles of setules in basal portion of postanal and anal regions. Postabdominal claws shorter and more robust than in female, basal spine strongly adpressed to claw as in female. Penis thin, long, slightly and gently curved, with pair of gonopores at tip, each opens on a relatively long projection.

Antenna I more robust than in female, with 13 'aesthetascs' of unequal length distally, one is actually the additional male seta.

Limb I with long, U-shaped copulatory hook, ODL as in female, IDL with male seta, and two largest setae with different setulation (as in female), all these setae of similar size, shortest IDL setae absent. Copulatory brush consisting of relatively short, robust setules. Copulatory brush setae relatively short, with inflated basal part.

Length 528–590 µm.

Redescription, taxonomic comments. See expanded comments in Kotov (2003).

Leydigia quadrangularis var. wojnowiensis Dybowski et Grochowski, 1898, p. 49 –51, fig. 8 was first established as a Nomen nudum ( Dybowski & Grochowski, 1895, p. 150). But then the taxon was described and illustrated. No significant difference with L. leydigi was reported by the authors ( Dybowski & Grochowski 1898): their morphometry based on a limited number of specimens seems inconsistent.

Differential diagnosis. Only two species are well-studied within the subgenus. L. leydigi differs from its closest relative L. louisi having: (1) body less compressed laterally; (2) presence of more or less defined postero-dorsal angle; (3) short lateral setae on postabdomen; (4) postabdominal setae with sparse setules; (5) no chitinous insertions within swimming setae.

Distribution. At present I can confirm the presence of L. leydigi in the Holarctic only. L. leydigi is common with numerous records from Germany ( Hollwedel 1995; Hollwedel 2001; Hollwedel 2002), Poland ( Krasnodebski 1937; Prószyṅska 1978), European Russia (Kotov, 2003), Canada ( Hann 1981; Chengalath 1982; Chengalath 1987).