Adineta cf. acuticornis Haigh, 1967

Zeng, Yue, Wei, Nan, Wang, Qing, Iakovenko, Nataliia S., Li, Ying & Yang, Yufeng, 2020, Bdelloid rotifers (Rotifera, Bdelloidea) of China: diversity and new records, ZooKeys 941, pp. 1-23 : 1

Adineta cf. acuticornis Haigh, 1967 Figure 2 ; Table 3

Material.

Eight specimens found in mosses and two specimens found in lichens, from tropical (GD 6) and subtropical (YN 5-6, SC 2) zones (Table 2 ).

Description.

Body transparent and colorless, with smooth skin. No eyespots. Rostrum rather long when animal creeps and stretches out, distal rostral pseudosegment semi-circular and flattened. Rostral lamella divided into two broad sickles-like lobes, immobile, laterally elongated, no trace of cilia under the present microscope image. Small oval head, HW 63-90% of HL and 11-16% of TL, HL 15-18% of TL. Five rectangular denticles in each rake.

Neck width not distinct from head and trunk. The width of the first two pseudosegments of neck approximately equal to HW, the second neck pseudosegment much wider and swollen than the first one. Antenna of two pseudosegments, with length 56-64% of the bearing pseudosegment width. Trunk oval, BW 15-22% of TL. Rump conical, TrL 54-67% of TL. The stomach lumen very narrow and Z-shaped (Fig. 2D ). Oviparous; egg oval and smooth, one knob at each pole (Fig. 2C ); Vitellarium large with eight nuclei.

Foot slim and short, of four pseudosegments. Spurs long, the inner edge of the spurs almost parallel to the straight outer edge for two-thirds of its length, then a small bulge followed by a contraction and tapers to a sharp point (Fig. 2E ). SL 4-8% of TL, and 143-193% of SSW. Three long and unsegmented toes. Dorsal toe longer than two ventral toes. Trophi small, round. Dental formula 2/2.

Measurements.

The detailed measurements are summarized in Table 4 with a comparison of the original data from Haigh (1967).

Remarks.

Adineta acuticornis has not been found since its original description by Haigh (1967) and was considered as an endemic morphospecies of New Zealand ( Shiel and Green 1996). It was found in China for the firstly time also in the Oriental biogeographic region recorded in two provinces of China in 2017 or 2018. It was recorded in damp mosses on soil face in the type locality, whereas in this study, numerous specimens were recorded in both dry and damp mosses, and two specimens in lichens on soil surface.

A distinct characteristic differentiating this morphospecies from Adineta vaga Davis is its wide and rostral lamellae which are slightly wider than the anterior head, while the rostral lamellae of A. vaga are narrower than the anterior head. It differs from Adineta glauca Wulfert by its spur shape, which is short and has a flat base, while A. glauca spur with a swollen base. This morphospecies differs from Adineta longicornis Murray by its spur shape which has bulge, while A. longicornis spur is slender and acute ( Murray 1906: 5a, 5b).

The general morphology of the Chinese specimen conforms to the description of the New Zealand population, except the position of the spur contraction is closer to the tip (the contraction is in the middle of the spur in Haigh’s description) and the stomach lumen do not have distinct two loops as Haigh’s description. A comparison with Haigh’s (1967) body dimensions showed a similar body proportion (Table 4 ). Since there was no genetic evidence to prove it actual systematic status, we assigned ‘cf.’ (resembling original description) as the status of this find. Besides, we observed three new morphological features missed by Haigh (1967): each rake with five denticles, a larger vitellarium with eight nuclei and egg with one knob on each pole.

Figures

Figure 2. Adineta cf. acuticornis Haigh, 1967 A, B habitus, ventral view C egg D stomach lumen E spur. Scale bars: 50 μm (A-D); 10 μm (E).