Dimorphic male scutal patterns and upper-eye facets of Simulium mirum n. sp. (Diptera: Simuliidae) from Malaysia

Abstract

Background: A species of Simulium in the Simulium melanopus species-group of the subgenus Simulium (formerly misidentified as S. laterale Edwards from Sabah and Sarawak, Malaysia) is suspected to have dimorphic male scutal color patterns linked with different numbers of upper-eye facets. This study aimed to confirm whether or not these two forms of adult males represent a single species.

Methods: DNA sequences generated from four genetic loci, the mitochondrial-encoded COI, COII, 12S rRNA and 16S rRNA genes, of both forms of Simulium sp. males were compared with each other and also with those of the females and larvae of the same species. Four other related Simulium spp. were also used for comparison.

Results: Both the concatenated dataset and single-locus phylogenetic analyses indicate that the two distinct morphological males of Simulium sp. are indeed conspecific, and represent, together with their associated females and larvae, a distinct species.

Conclusions: Based on DNA analyses, Simulium sp. is proven to show dimorphism in males and is herein described as a new species, Simulium mirum Takaoka, Sofian-Azirun & Low. This is the first report of such a novel species among the family Simuliidae.

Fig. 1

Heads and thoraces of the female, and two male forms of Simulium mirum n. sp. (a) Female. b Form A male. c Form B male. All are shown in dorsal view

Fig. 2

Maximum likelihood phylogenetic tree of the Simulium melanopus species-group from East Malaysia based on concatenated sequences of COI, COII, 12S rRNA and 16S rRNA genes. Bootstrap and posterior probability values [ML/MP/NJ/BI] are shown on the branches

Fig. 3

Female of Simulium mirum n. sp. (a) Antenna (left side; outer view). b Third segment of maxillary palp with sensory vesicle (left side; frontal view). c Cibarium (frontal view). d Basitarsus and second tarsomere of hind leg (left side; outer view). e Claw. f Eighth sternite and ovipositor valve (right half; ventral view). g Ovipositor valve (right side; anteroventral view). h genital fork (ventral view). i Terminalia showing eighth sternite, ovipositor valve, paraproct and cercus (lateral view). j Paraproct showing anteroventral sclerotized plate (left side; anterior view). k Spermatheca. Scale-bars: 0.1 mm for (d); 0.05 mm for (a); 0.02 mm for (b), (c) and (f)–(k); 0.01 mm for (e)

Fig. 4

Male of Simulium mirum n. sp. (a) Third segment of maxillary palp with sensory vesicle (left side; frontal view). b Scutal color pattern of form A (dorsal view). c Scutal color pattern of form B (dorsal view). d Basitarsus and second tarsomere of hind leg (left side; outer view). e Coxites, styles and ventral plate (ventral view). f Coxite (right side; ventrolateral view). g and (h) Styles (right side; (g), ventrolateral view; (h), medial view). i Ventral plate and median sclerite (lateral view). j Ventral plate (caudal view). k Median sclerite (caudal view). l Paramere (right side; caudal view). m Aedeagal membrane (right half; caudal view). n Dorsal plate (ventral view). o and (p) Tenth abdominal segments and cerci (right side; (o), lateral view; (p), caudal view). Scale-bars. 0.1 mm for (d); 0.02 mm for (a) and (e)–(p)

Fig. 5

Pupa of Simulium mirum n. sp. (a) Part of face near its border to frons showing central area covered with tubercles (front view). b Frontal trichomes. c Facial trichome. d–g Thoracic trichomes (d, mediodorsal; e, anterolateral; f, mediolateral; g, ventrolateral). h Anterior half of thorax and gill filaments (left side; lateral view). i Middle part of upper filament of dorsal pair showing annular ridges forming reticulate patterns (lateral view). j Slender seta on dorsal surface of abdominal segment 1. k Short slender seta, minute slender seta and minute somewhat stout seta on dorsal surface of abdominal segment 2. l and (m) Cocoons (l, lateral view; m, dorsal view). Scale-bars: 1.0 mm for (l) and (m); 0.1 mm for (h); 0.05 mm for (a); 0.02 mm for (b)–(g) and (i)–(k)

Fig. 6

Larva of Simulium mirum n. sp. (a) Head capsule showing postgenal cleft (ventral view). b Mandible. c Hypostoma. Scale-bars: 0.05 mm for (a); 0.02 mm for (b) and (c)