Vietnamella sp. B

Auychinda, Chonlakran, Sartori, Michel & Boonsoong, Boonsatien, 2020, Vietnamellidae (Insecta, Ephemeroptera) of Thailand, ZooKeys 902, pp. 17-36 : 17

Vietnamella sp. B Figs 1B , 4B, E, H, K

Material examined.

Thailand; 1 larva (immature) on slide, Tak Province, Mae Ra-Merng, 17°31'18.7248"N, 98°3'36.8064"E, 26.X.2015, A. Watcharangkool leg. (ZMKU).

Description.

Larva (in alcohol, Fig. 1B ). Body length 6 mm without cerci; body reddish with dense setae lateral and on margin of head.

Head. Reddish with a sharp pair of occipital tubercles and a single sub-occipital tubercle medially; two projections below eyes: inner pairs of projections small, spine-like and sharp; outer pair large, triangular, cone shaped with five unequal serrated spines (Fig. 4B, E ), basal spine the largest. Labrum, similar to V. thani and V. maculosa sp. nov. Labium, glossae width greater than length, glossae and paraglossae with dense setae on surface, labial palpi three segmented, basal segment broader and longer than the second, apical segment small; palpi with tiny setae. Left mandible and right mandible slender, mostly similar to the other Vietnamella species. Maxillae slender, maxillary palpi three segmented with tiny setae, length ratio from basal to apical = 1.3:1:1. Hypopharynx, lingua and superlinguae nearly round with setae on surface.

Thorax. Pronotum with small sharp anterolateral projections, slight protuberances below the anterolateral projections. Forefemur strongly expanded with serrations or teeth projections on ventral margin; transverse ridge serrated with small setae. Midfemur without any projection. Hindfemur without any projection, expanded, longer than midfemur; dorsal margin with a row of hair-like setae. All claws similar, with one small denticle basally.

Abdomen. Tergite I-VI and VIII-X with pair of median ridges or tubercles progressively; tergite VII with a single tubercle (Fig. 4H ); posterolateral angles of terga II-IX extended into sharp projection; tergite X with a pair of moderately-developed tubercles (Fig. 4K ); lateral margins of tergite with dense setae. Gills on segments III-VI similar in structure with dorsal and ventral lamella, the latter further divided into two clusters, each with several smaller lobes; gill VII small, with two lamellae but ventral lamella divided into three lobes.

Diagnosis.

The larva of Vietnamella sp. B can be separated from those of other species based on the following characteristics: i) outer pairs of projections on the head are large and stout, triangular, and cone shaped, with five unequally serrated spines (one large spine + four small spines), and ii) the abdominal tergites II-IX have a pair of projections or tubercles at the posterolateral margin except for tergite VII which has only a single projection (Fig. 4H ).

Remarks.

The larval description given herein agrees with larvae of other species belonging to the genus Vietnamella , including the presence of a pair of projections on the head, the expanded femur and the forefemur with serrations on the outer dorsal margin. The larva described here has serrated spines on the outer projection of the head that differ from the other valid species of Vietnamella .The outer serrated projection is similar to that of Vietnamella sp. A from India (Selvakuma et al. 2018), but it differs in the number and character of the outer projection spines (four equal serrated spines in Vietnamella sp. A, five unequal serrated spines in Vietnamella sp. B). Although Vietnamella sp. B was not a mature larva, the phylogenetic analysis showed it belonged to a clearly different clade and had a high genetic distance compared to the other species (Fig. 12 ; Table 2 ). Formal description of this species is pending more material.

Distribution.

Tak Province.

Adult and egg.

Unknown.

Figures

Figure 1. Vietnamella spp. A Vietnamella maculosa sp. nov., habitus in dorsal view B Vietnamella sp. B, habitus in dorsal view. Scale bars: 1 mm.

Figure 4. Vietnamella spp. Vietnamella maculosa sp. nov. (A, D, G, J): A outer projection on head (arrow) D inner and outer projections on head G, J tubercle on tergite VII and X; Vietnamella sp. B (B, E, H, K): B outer projection on head (arrow) E inner and outer projections with serration on head H, K tubercles on tergite VII and X; Vietnamella thani (C, F, I, L): C outer projection on head (arrow) F inner and outer projections on head I, L tubercles on tergite VII and X. Scale bars: 1 mm (A-C); 0.5 mm (G); 0.1 mm (D-F, H, I); 0.05 mm (J-L).

Figure 12. Bayesian interference of Ephemerelloidea. The COI phylogenetic construction of Vietnamella and sister groups with the percentages indicating branch probability support. Potamanthellus edmundsi was used as the outgroup.