Ptygura libera Myers, 1934

Wei, Nan, Jersabek, Christian D. & Yang, Yufeng, 2019, Rotifers from China (Western Guangdong Province), with description of Lecane zhanjiangensis sp. nov. (Rotifera: Monogononta: Lecanidae), Zootaxa 4603 (1), pp. 66-80 : 66-80

Ptygura libera Myers, 1934

( Figs 5–6 )

Redescription of female. Corona ( Fig. 5A, 5E ) large, bilobate (circular corona with a dorsal gap in Myers (1934), misinterpreted trilobate in Nogrady (1976)) with a dorsal indentation and two red apical eyespots. Corona a circumapical band, well developed dorsally, poorly developed latero-ventrally ( Fig. 5E ), interrupted ventrally. One frontal protuberance in contracted stage ( Fig. 5B ). Neck indistinct, and body smoothly tapering into retractable foot of medium length, which terminates in a long peduncle anchoring to a membranous structure ( Fig. 5A, 5F ) connecting to the tube. Head and anterior part of the trunk usually bent dorsally while swimming ( Fig. 5E ). Anus near middle of the trunk, opening upwardly on the dorsal side ( Fig. 5C, 5D ). Lateral antennae long and slender. Tube ( Fig. 5A, F ) transparent oval to pyriform, inner sheath conspicuous, distinct cylindrical, outer layer gelatinous and difficult to see. Usually one or two eggs next to the foot.

Trophi malleoramate ( Fig. 6 ), nearly symmetrical. Unci plates consist of right/left: 14–15/14–15 weakly webbed teeth. Three right and four left major teeth almost straight with long lanceolate head. Minor teeth head sharply pointed. Rami elongate-triangular with short blunt alulae. Median rami apophyses inapparent in caudal view. Basal apophyses moderately developed. Manubria crescent-shaped with three chambers. Fulcrum short, with a weakly developed basal plate.

Comments. This widely-distributed species ( De Ridder & Segers, 1997; Segers, 2007) has previously been recorded from Afrotropical (e.g. Bērziņš, 1982; De Ridder, 1987; Koste & Tobias, 1987; 1989; De Ridder, 1992), Nearctic (e.g. Myers, 1934; Nogrady, 1976; 1983; Stemberger, 1990; Siegfried, 1991; Jersabek et al., 2003), Neotropical (e.g. Koste, 1972; Koste & Jose de Paggi, 1982; Vásquez et al., 1998; Garcia-Morales & Elias- Gutierrez, 2004; Garraffoni & Lourenço, 2012; Ferrando & Claps, 2016), Palaearctic? ( Sudzuki, 1992; Salem et al., 2016) and Oriental ( Umi et al., 2018) regions, with most records from the Nearctic and Neotropis. Ours is the first record for China.

Ptygura libera is known as a warm-stenotherm ( Nogrady, 1976; Koste & Tobias, 1987; Garcia-Morales & Elias-Gutierrez, 2004), that prefers less nutrient rich waters ( Salem et al., 2016; Umi et al., 2018) and tolerates low pH ( Koste, 1972; 1978; Umi et al., 2018). It frequently occurs as a dominant species in lakes and reservoirs etc. (e.g. Nogrady, 1976; Koste & Tobias, 1987; Siegfried, 1991; Stemberger, 1990; Umi et al., 2018). The species was found in summer, when it dominated the rotifer community of the Huguangyan Lake, an oligo-/mesotrophic closed maar lake with relatively low nutrient and chlorophyll content ( Zhang et al., 2015; Chen et al., 2018), confirming the ecological preferences of P. libera .

Figures

FIGURE 5. Light microscope photograph of Ptygura libera. A. Habitus, dorsal view. B. Habitus, lateral view. C–E. Anterior part of body, lateral view. F. Peduncle (attachment stalk) and gelatinous tube. Arrows show the excreting anus. Scale bar: A–F: 50 µm.

FIGURE 6. Ptygura libera, scanning electron microscope photographs of trophi. A. Complete set, frontal view. B. Complete set, caudal view. C. Unci and rami, frontal view. D. Unci and rami, caudal view. Scale bar: A–D: 2 µm.