Prosopistoma carinatum, Boonsoong, Boonsatien & Sartori, Michel, 2019

Boonsoong, Boonsatien & Sartori, Michel, 2019, Review and integrative taxonomy of the genus Prosopistoma Latreille, 1833 (Ephemeroptera, Prosopistomatidae) in Thailand, with description of a new species, ZooKeys 825, pp. 123-144 : 129-132

Prosopistoma carinatum sp. n. Figures 1D, 1F, 6, 7, 8, 9, 10, 12E, 12F, 14

Material examined.

Holotype. THAILAND; Holotype, 1 mature larva, Kanchanaburi province, Thong Pha Phum, Ban Pra Chum Mai, 14°35'01.4"N, 98°34'54.3"E, 233 m, 11.IV.2015, B Boonsoong leg. (ZMKU); Paratypes. 1 larva same data as holotype (MZL, GBIFCH00657926); 6 larvae same data as holotype (ZMKU); 1 mature larva, 8 larvae, Kanchanaburi province, Ban Pra Chum Mai, 14°35'01.4"N, 98°34'54.3"E, 233 m, 26.IV.2016, B Boonsoong leg. (ZMKU).

Additional material.

THAILAND; 1 larva, Nakhon Si Thammarat province, Lan Sa Ka, Khao Luang water fall, 11°06'24.36"N, 101°28'43.08"E, 533 m, 2.VII.2016, B Boonsoong leg. (ZMKU); 1 larva, Narathiwat province, Waeng district, Ai Sae, 5°47'45.9"N, 101°50'5.46"E, 64 m, 21.IV.2018, B Boonsoong leg. (ZMKU).

Distribution.

Kanchanaburi province (W), Nakhon Si Thammarat province (S), Narathiwat province (S).

Diagnosis.

The larvae of Prosopistoma carinatum sp. n. can be distinguished from those of other species by the combination of the following characteristics (Table 3): (i) carapace with two longitudinal ridges on each side of the midline on its surface (Fig. 1F), (ii) antenna 7-segmented, (iii) carapace with three pale-coloured depressions on each side, (iv) carapace with a very narrow flange width and strong convexity, (v) carapace with a typically brown colouration and a distally irregular (zig-zag) yellow pattern at 0.7 times the length of the carapace, (vi) carapace with circular scale-like structures, (vii) presence of three long serrated bristles at the base of the inner canine and (viii) ventral margin of the fore-tibia with nine pectinate setae.

Description

(in alcohol). Body length 1.94-2.43 mm excluding caudal filaments.

Head. Head yellowish with median blackish ocellus between antennae (Fig. 8A), head width approximately 3 times length. Epicranial ecdysial sutures prominent, passing through the anterior margin of the lateral ocelli, and between the compound eyes and the antennal bases and continuing to the lateral margin of the head (Fig. 8B). Antenna 7-segments (Figs 6A, 8B, 8C), longer than the distance from antennal base to anterior margin of head; segment I usually retracts into head capsule; segment III the longest and shorter than combined length of segments IV–VII, antenna segment VII minute (Fig. 8C). Labrum (Fig. 6D) narrow, 3 times wider than long, anterior margin fringed with dense fine setae. Left and right mandibles similar (Fig. 6E, 6F). Outer canine of mandibles subequal and broader than inner canine, with three apical teeth, a smaller outer tooth and a larger inner tooth with a serrated margin near the apex and three small spines; inner canine with two apical teeth, including a larger inner one with a serrated inner margin near the apex with three spines. Three long serrated bristles arising from the base of the inner canine (Fig. 6G). A single stout feathered seta lateromedially on each mandible (Fig. 6E, 6F). Maxillae (Fig. 6H) crowned by a rigid canine and three subequal moveable dentisetae; three long-feathered stout bristles arising near the base of the apical canine and dentisetae on the galea-lacinia. A single unserrated bristle arising approximately 2/3 of the way down the sclerotised section of the galea-lacinia. Maxillary palpi 3-segmented, segment II the longest, length ratio of maxillary palp segments from basal one to apical: 1.9:2.2:1(Fig. 6H).

Carapace. Carapace general colouration dark brown, distally with an irregular (zig-zag) yellow pattern at 0.7 times the length of the carapace (Fig. 1D). Two longitudinal ridges on the anterior surface region, and two short ridges on the pale surface area (Figs 1D, 1F, 9A, 9C, 9D). Carapace with one pale-coloured circular depression on lateral side of the anterior region (Figs 1F, 9B) and two pale-coloured striped depressions at the midline. Carapace flange width very narrow. Cuticle of carapace coarsely pitted and interspersed with scale-like structures (Fig. 9E, F). Distal margin of the carapace protruding slightly over the exhalent notch (Figs 1D, 9A). In lateral view, carapace strongly convex, with a convexity (ratio of maximum carapace height to length along the posterior margin of the carapace) range 0.56-0.58. Sternum pitted, with coarse scale-like structures within the triangular sternal plate (Fig. 8D, F).

Legs. Dorsal margin of fore femur with 14 short simple setae (Fig. 7A); ventral margin of fore tibia with nine pectinate setae (Figs 7B, 10C). Anterior and posterior surface of femur covered with scale-like pattern (Figs 7A, 10A). Tarsal claws of all three pairs of legs sharp and without denticles.

Abdomen. Abdominal gills (Fig. 7 C–G). Gill I with lamellate upper portion, margin serrated, lower portion divided into multiple filaments (Fig. 7C). Gill II expanded to form broad leaf-like lamella (Fig. 7D). Gills III-V with multiple branching filaments (Fig. 7E, F). Gill VI tiny, unbranched (Fig. 7G). Posterolateral projections of abdominal segments VII–IX broad, apex pointed. Caudal filaments small, retractile, short, feathered.

Subimago and Imago.

Unknown.

Etymology.

The name carinatum (Latin for carinate or keeled), refers to the prominent keels or ridge-like mesonotal convexity of the species.