Clypeocaenis multisetosa Soldán, 1978

Vannachak, Viengkhone, Malzacher, Peter & Sangpradub, Narumon, 2024, Contribution to the genus Clypeocaenis Soldán, 1978 (Ephemeroptera: Caenidae) from Lao People’s Democratic Republic with a key to Oriental species, Zootaxa 5501 (4), pp. 501-523 : 514

Clypeocaenis multisetosa Soldán, 1978 ( Figs. 8–11 )

Clypeocaenis multisetosa Soldán, 1978: 122 (orig. desc., Figs 20–24).

Materials examined. 2 male larvae (THNHM-I-00029780–00029781). Vientiane Capital, outlet Stream of Nam Xouang Reservoir, Naxaythong District , 18°14’50.92”N, 102°27’52.32”E, 187 m a.s.l., 15.XII.2019, deposited in the Natural History Museum, Thailand . 3 male and 4 female larvae (Cl / Laos.005), Lao PDR, Khammouane Province, Xebangfai District , Xe Nou River , 17°4’5.56”N, 105°4’13.68’’E, 154 m a.s.l., 6.I.2022, deposited in NUoL-AIC . 1 male and 3 female larvae (Cl / Laos.007) Savannakhet Province, Songkhone District, Xe Bang Hieng River , 16°05’51.42”N, 105°22’33.13”E, 126 m a.s.l., 24.XI.2019, deposited in KKU-AIC, all V. Vannachak leg.

Egg: Oval-shaped, with 134–143 μm in length and 98–100 μm in width. Very flat cap-shaped epithema. Chorion finely porous, both micropyle and sperm guide not visible ( Fig. 11C, D ).

Remarks. Clypeocaenis multisetosa was initially reported from India by Soldán in 1978. The specimens from Lao PDR were identified as Cl. multisetosa based on a combination of morphological features, including the number and arrangement of setae on the clypeal protrusion with less than 20 long setae ( Fig. 9A ), maxillary palp two segmented, labial palp with second segment short and irregularly trapezoidal, and third segment elongated ( Fig. 9D, F ). Distinctive transverse row of short stout setae on the dorsal surface of the forefemur, marginal setation patterns on the mid and hind femora ( Fig. 10A–C ), median projections and spines on tergum II, and the characteristic posterior margin process of terga VIII and IX, as well as the structure of the operculate gill ( Fig. 11A, B ). The specimens from Lao PDR exhibit some variations compared to the original description by Soldán (1978), such as the presence of 6–7 setae on the operculate gill’s medial ridge and 4–5 denticles on the tarsal claw, in contrast to the 3–4 setae on the medial ridge and 6–8 denticles on the tarsal claw as reported by Soldán (1978). Additionally, shield-shaped microtrichia on the body surface and operculate gills, resembling a spider web with a smooth margin, were observed in Cl. multisetosa ( Fig. 8C ), differing from the characteristics of Cl. oligosetosa ( Fig. 8A ). The microtrichia band on the ventral side of the operculate gills follows closely along the lateral margin, terminating well before the gill’s hind margin. This band comprises clusters of 2 or 3 spines and single spines, primarily located on the inner margin of the band ( Figs. 8D , 12B ). Eggs extracted from mature female larvae are documented for the first time.

Distribution and habitats. Clypeocaenis multisetosa specimens were documented in the Vientiane Capital, Khammouane, and Savannakhet Provinces of the Lao PDR ( Figs. 13A, C, D , 14 ). This species was located in the littoral zones of the Xe Nou River, Xe Bang Hieng River, and the outlet stream of the Nam Xouang Reservoir. The ecological characteristics of the Xe Nou and Xe Bang Hieng Rivers have been previously mentioned. The outlet stream of the Nam Xouang Reservoir meanders through a village. Surrounding areas comprise residential settlements, agricultural fields, gardens, and areas designated for livestock activities. The water velocity within this stream is noted to be low (less than 0.5 m /s). The substrate primarily consists of bedrock, interspersed with boulders, sand, silt, and accumulations of detritus leaf litter, providing a diverse habitat for Cl. multisetosa .

Figures

FIGURE 8. Clypeocaenis oligosetosa Soldán, 1983 (A, B) and Clypeocaenis multisetosa Soldán, 1978 (C, D). A, C. High magnification view of microtrichia on the dorsal surface of operculate gills. B, D. Microtrichia band on the ventral side of operculate gills. Scale bars: A = 20 μm; C = 50 μm; B, D = 100 μm.

FIGURE 9. Clypeocaenis multisetosa Soldán, 1978, collected from Xe Nou River, Xe Bang Hieng River, and outlet Stream of Nam Xouang Resurvoir in Lao PDR, A. Head capsule. B. Labrum. C. Mandibles. D. Maxillae. E. Hypopharynx. F. Labium. Scale bars: A, D (left maxillary palp) = 500 μm; B, C (right mandible), E = 200 μm; C (left mandible) = 300 μm; D, F (right maxillary palp) = 400 μm.

FIGURE 10. Clypeocaenis multisetosa Soldán, 1978, from Xe Nou River, Xe Bang Hieng River, and outlet Stream of Nam Xouang Resurvoir, Lao PDR, A. Forefemur. B. Mid femur. C. Hind femur. D. Foreclaw. E. Mid claw. F. Hind claw. Scale bars: A, B = 500 μm; C = 400 μm; D–F = 100 μm.

FIGURE 11. Clypeocaenis multisetosa Soldán, 1978, from Xe Nou River, Xe Bang Hieng River, and outlet Stream of Nam Xouang Resurvoir in Lao PDR, A. Abdominal terga II–VII. B. Operculate gill. C, D. Eggs. Scale bars: A, B = 500 μm; C, D = 100 μm.

FIGURE 12. Microtrichia bands on the ventral side of the operculate gill, as previously documented. A. Clypeocaenis soldani. B. Clypeocaenis multisetosa. C. Clypeocaenis oligosetosa. D. Clypeocaenis kaveri. E. Clypeocaenis afrosetosa. F. Clypeocaenis laosensis sp. nov. G. Mekongellina sangpradubae.

FIGURE 13. Habitats of the genus Clypeocaenis Soldán, 1978 in Lao PDR, A. Xe Nou River, Xebangfai District, Khammouane Province. B. Tha Hao Stream, Xaybury District, Savannakhet Province. C. Xe Bang Hieng River, Songkhone District, Savannakhet Province. D. Outlet Stream of Nam Xouang Reservoir, Naxaythong District, Vientiane Capital.

FIGURE 14. Geographic distribution of the Clypeocaenis laosensis sp. nov. (circle), C. oligosetosa (star); C. multisetosa (triangle).