Lecane dorysimilis, Dang, Mau Trinh, Segers, Hendrik & Sanoamuang, La-Orsri, 2015

Dang, Mau Trinh, Segers, Hendrik & Sanoamuang, La-Orsri, 2015, Psammon rotifers in Central Vietnam, with the descriptions of three new species (Rotifera: Monogononta), Zootaxa 4018 (2), pp. 249-265 : 257-258

Lecane dorysimilis new species

(Figs 7–8, 15–16)

Synonym: L. doryssa Harring, 1914 after Wang (1961: p. 122–123 figs 98a, b); Sarma (1988: p. 226, fig. 12b).

Type specimens. Holotype (IG 33091 RIR 237) and one paratype (IG 33091 RIR 238) in permanent slides deposited in the Royal Belgian Institute of Natural Sciences, Brussels, Belgium ( RBINS). Two slides containing one paratype each (SK-R0128-01, - 02) deposited in the Science Museum, Khon Kaen University, Khon Kaen, Thailand.

Type locality. Bau Thiem Lake (16°38'6.60"N, 107°21'51.00"E), Phong Binh community, Phong Dien district, Thua Thien Hue province, Vietnam.

Differential diagnosis. Lecane dorysimilis n. sp. has to date always been confused with L. doryssa Harring, 1914 . The two are indeed very similar, but differ in several details. In particular (compare Figs 7–8, 15–16 with 11– 12, 18–19):

• The lorica of L. dorysimilis n. sp. is definitely more elongate than that of L. doryssa , as can be seen by comparing the length/width ratio of dorsal and ventral plates in both ( Figure 51 : dorsal plate: z = 3.605 (p = 2.2e- 16) and ventral plate: z = 3.455 (p = 2.2e- 16);

• The lateral margins of the ventral plate show clear notches posteriorly of the head aperture in L. dorysimilis n. sp.;

• The disposition of the ornamental lorica folds is quite different; most notably in this respect is the inverse Ushape medially on the anterior half of the ventral lorica in L. doryssa , whereas in L. dorysimilis n. sp. the corresponding folds are interrupted, forming a cross-like shape;

• The foot pseudosegment of L. dorysimilis n. sp. is constricted laterally, and, in well-contracted specimens, does only scarcely project beyond the posterior margin of the ventral plate.

Description. Lorica stiff, both ventral and dorsal plates strongly ornamented. Dorsal plate anteriorly narrower, medially equally wide or wider than ventral plate. Head aperture margins straight or slightly convex, antero-lateral corners angulate. Ventral plate longer than wide, with incomplete transverse and longitudinal folds. Lateral margin with anterior notches. Lateral sulci shallow. Foot plate broad, with rounded triangular coxal plates. Prepedal fold narrow, elongate, lateral margins slightly biconvex, distally with median projection. Foot pseudosegment constricted laterally, not projecting. Two parallel-sided toes, bearing incompletely separated, slightly outwardly curved, elongate claws.

Measurements (mean (SD), in Μm): DPl 58.3 (1.8), DPw 46.2 (2.6), VPl 61.4 (3), VPw 43.8 (1.7), HAw 42.4 (2.1), Tl 17.2 (0.6) and Cl 11.4 (2.2).

Ecology and distribution. We found the new species co-occurring with L. doryssa in the hygropsammon of Bau Thiem Lake. Other distinguishable, incorrectly identified illustrated records of L. doryssa pertaining to L. dorysimilis n. sp. confirm the presence of the latter species from China (Liaoning Province: Wang, 1961) and India (Belgharia’s ponds, Calcutta: Sarma, 1988). It is very likely that the new species is even more widely distributed than can be reported here.

On account of the available literature data and unpublished observations by HS, we consider L. dorysimilis n. sp. to be a psammophile or, perhaps, even psammoxene, littoral taxon rather than a psammobiontic species.

Etymology. The name dorysimilis is formed by combining the specific name of species Lecane doryssa and similis , a Latin word meaning similar. The species name L. dorysimilis n. sp. thereby refers to its similarity and confusion with Lecane doryssa Harring.

Figures

FIGURE 51. Box plot showing the distribution of ratio length / width of dorsal and ventral plate of L. dorysimilis vs. L. doryssa, with value of permutation test (approximate = 1000).