Colurella psammophila Segers & Chittapun, 2001

Wei, Nan, Jersabek, Christian D., Xu, Runlin & Yang, Yufeng, 2019, New species and records of Colurella (Rotifera: Lepadellidae) from South China, with a key to Chinese Colurella, Zootaxa 4586 (3), pp. 475-490 : 482-486

Colurella psammophila Segers & Chittapun, 2001

( Figs. 7–9 )

This presumed Oriental endemic was to date only known from the hygropsammon of Mai-Khao peat swamp on Phuket Island, Thailand ( Segers & Chittapun, 2001; Chittapun et al., 2007). The present record is the second ever of this species ( Wei & Xu, 2014).

The specimens found in the Pearl River Estuary ( Figs. 7 , 8 ) and in Nandujiang River Estuary ( Tab. 1 ) showed great morphological variability, which mainly resulted in two forms with different lorica shape and fewer transitional specimens ( Fig. 8F, 8T ). Both forms frequently co-occurred in the samples of the mangrove swamp with all live ( Fig. 8 A–8C) and fixed ( Fig. 8 D–8T) specimens having a median keel ( Figs. 7E, 7F , 8 A–8C, 8K, 8S) in the ventral sulcus, but the two main forms differing in lorica shape as follows: (1) the typical form of the species as originally described ( Figs. 7A, 7B , 8 A–8E); (2) lorica ventral margin undulate with conspicuous median bulge and anteroventral lorica margin with shallow concavity or smoothly curved ( Figs. 7C, 7D , 8 G–8O). Possibly, this variability was to some extent caused by fixation effects, due to different levels of contraction. We examined numerous trophi of both forms, to confirm conspecificity ( Fig. 9 ). Besides, we found a single specimen with slightly larger and higher lorica and the anterior head aperture margins smoothly curved (dorsally and ventrally straight, medially curved in the original description) ( Figs. 7G , 8U ), which probably also belongs to Colurella psammophila .

This species was collected predominantly from swamps with shallow waters in South China. It was present over many months in mangrove swamps and estuarine habitats in Haikou, Hainan Province, so can be regarded as a eurythermal and euryhaline species (cf. Fontaneto et al., 2006; Fontaneto et al., 2008a).

Measurements. Body (N = 15 females): lorica length 70.0– 81.5 µm (mean = 74.8± 3.1 µm), lorica height 43.0– 48.9 µm (mean = 45.9± 1.9 µm), lorica width 34.4–38.4 µm (mean = 36.9± 1.3 µm, N = 8), anterior aperture width: 35.0–42.0 µm (mean = 39.0± 2.5 µm), second foot pseudosegment 6.0–8.0 µm (mean = 6.4± 0.7 µm), third foot pseudosegment 7.0–8.0 µm (mean = 7.4± 0.5 µm), toe length 33.0– 37.7 µm (mean = 35.0± 1.3 µm); lorica length/ height: 1.50–1.68 (mean = 1.59± 0.07 µm); third/second foot pseudosegment: 0.88–1.33 µm (mean = 1.15± 0.13 µm).

Colurella psammophila (?) specimen ( Figs. 7E , 8U ). Body (N = 1 female): lorica length 88.7 µm, lorica height 53.3 µm, anterior aperture width 46.5 µm, second foot pseudosegment 6.5 µm, third foot pseudosegment 7.8 µm, toe length 40.7 µm.

Figures

FIGURE 7. Colurella psammophila Segers & Chittapun, 2001. A–D. Left lateral view. E, F. Ventral view. G. Colurella psammophila (?), left lateral view. Scale bar: A–G: 50 µm. A–F: from one sample of the mangrove swamp site collected on 30 August, 2007; G: from the artificial pond site collected on 26 May, 2007.

FIGURE 8. Light microscope photograph of Colurella psammophila Segers & Chittapun, 2001. A–O, T. Left lateral view. P, Q. Dorsal view. R. Ventral view. S. Ventrolateral view. U. C. psammophila (?), left lateral view. Scale bar: A–H: 50 µm. A–C: live animals collected from Qi’ao Island on 28 July, 2018; D–T: fixed specimens all from one sample of the mangrove swamp site collected on 30 August, 2007; H: specimen collected from the artificial pond site on 26 May, 2007.

FIGURE 9. Colurella psammophila Segers & Chittapun, 2001, scanning electron microscope photographs of trophi. A. Complete set, ventral view. B. Complete set, dorsal view. C. Rami, unci and fulcrum, ventral view. D. Basal apophysis, ventral view. E. Rami and unci, dorsal view. Scale bar: A–B: 5 µm; C–E: 2 µm. ba: basal apophysis, bf: basifenestra, cr: crista rami, dc: dorsal manubrium chamber, f: fulcrum, m: manubrium, mau: major uncini; mc: median manubrium chamber, miu: minor uncini; r: ramus, ra: rami median apophysis, rs: rami scleropili, u: uncus, vc: ventral manubrium chamber. All specimens from one sample of the mangrove swamp site collected on 30 August, 2007.