Euplotes balteatus (Dujardin, 1841) Kahl, 1932

Pan, Ying, Li, Liqiong, Shao, Chen, Hu, Xiaozhong, Ma, Honggang, Alrasheid, Khaled A. S. & Warren, Alan, 2012, Morphology and Ontogenesis of a Marine Ciliate, Euplotes balteatus (Dujardin, 1841) Kahl, 1932 (Ciliophora, Euplotida) and Definition of Euplotes wilberti nov. spec., Acta Protozoologica 51 (1), pp. 29-38 : 34-35

Euplotes balteatus

Comparison with other populations: In spite of the variability of its body shape and size, the high stability of the dorsal silverline system pattern, ventral infraciliature, and dorsal structure in vivo are important characters for the identification of Euplotes balteatus ( Tuffrau 1960, Curds1975, Song and Wilbert 2002, Jiang et al. 2010c). The China population corresponds closely with the populations studied previously in terms of its body shape, appearance of adoral zone of membranelles, ventral ciliature, double- eurystomus type silverline system and marine habitat ( Kahl 1932, Tuffrau 1964, Curds 1975). It differs slightly, however, in body size in vivo (<80 µm long vs.> 100 µm long) and the number of dikinetids of the mid-dorsal rows (ca. 15 vs. ca. 20). These, however, are regarded as populationlevel differences; hence its identity as E. balteatus is not in doubt ( Fig. 4A–C ).

Comparison with similar congeners from the same location: Four similar (small sized, ovoid body shaped) Euplotes species have been reported from the coastal waters of Qingdao in addition to E. balteatus , namely E. minuta Yocum, 1930 , E. parabalteatus Jiang et al., 2010 , E. orientalis Jiang et al., 2010 and E. raikovi Agamaliev, 1966 . E. minuta and E. raikovi can be easily separated from E. balteatus by the type of silverline system and the number of frontoventral cirri ( Fig. 5A–E, P–R ). Disparities between E. balteatus and E. parabalteatus include: 1) the number of dorsal kineties (8 vs. 6–7); 2) the number of adoral membranelles (28– 43 vs. 19–23); 3) the shape of macronucleus (C-shaped vs. slightly curved rod shaped); 4) the arrangement of frontoventral cirri (V/2 close to V/3 vs. V/2 close to VI/2) ( Fig. 5F–J ). E. orientalis is distinguished from E. balteatus in having two reduced cirri (IV/2 and V/2) each composed of single dikinetids (vs. two normalsized cirri in E. balteatus ) ( Fig. 5K–O ).

Morphogenesis: Five types of morphogenesis pattern have been recorded in Euplotes based on the segmentation pattern of the frontoventral transverse cirral anlagen, the absence/presence of reduced cirri and the migration of frontoventral cirri during the ontogenesis process; these are the affinis - type, the eurystomus - type, the charon - type, the raikovi - type, and the orientalis - type ( Curds 1975, Voss 1989, Wang and Song 1995, Martín-González et al. 1998). E. balteatus can be assigned to the charon - type, that is the frontoventral and transverse cirri are formed following the pattern 3:3:3:3:2. Based on the mode of formation of the caudal cirri, Euplotes can be divided into three further types: focardii - type, vannus - type and charon - type ( Serrano et al. 1992, Ma et al. 2008, Jiang et al. 2010c). E. balteatus belongs to the focardii - type in which a caudal cirrus is formed posterior to each of the rightmost two dorsal kineties/DKA in both dividers, hence the number of caudal cirri is constant ( Shao et al. 2010).

One noteworthy feature in the morphogenesis of E. balteatus is that it commences with the dedifferentiation of basal bodies in the mid-region of each dorsal kinety. These basal bodies proliferate to form sparsely distributed elementary anlagen, which then break apart and extend towards the both directions from the fraction spot along the longitudinal axis. These findings are consistent with those of Shao et al. (2010) who noted that the dorsal kineties in E. charon develop in an atypical primary mode.

Figures

Fig. 4A–K. Euplotes balteatus and Euplotes wilberti nov. spec. from life (A, G), after protargol (D, J, K) and silver nitrate (B, C, E, F, H, I) impregnation. Arrows point to the marginal cirri. A – ventral view of Euplotes balteatus, to show the ventral ciliature (from Kahl 1932); B, C – ventral and dorsal views of Euplotes balteatus, showing the silverline systerm (from Tuffrau 1964); D – Euplotes balteatus, to show variations in the shape of the macronucleus; E, F – ventral and dorsal views showing the silverline system; G–K – Euplotes wilberti nov. spec., to show the live morphology (G), silverline system (H, I), infraciliature (J, K) and macronucleus (K) (from Song and Wilbert 2002). Scale bar: 30 µm.

Fig. 5A–R. Morphology from life, infraciliature and silverline system of four morphologically similar Euplotes species. A–E – Euplotes minuta (from Song and Wilbert 1997a); F–J – Euplotes parabalteatus (from Jiang et al. 2010a); K–O – Euplotes orientalis (from Jiang et al. 2010b); P–R – Euplotes raikovi (from Jiang et al. 2010b). Scale bar: 20 µm.