Stylops nassonowi Pierce

Straka, Jakub, Alqarni, Abdulaziz S., Juzova, Katerina, Hannan, Mohammed A., Hinojosa-Diaz, Ismael A. & Engel, Michael S., 2015, Rediscovered parasitism of Andrenasavignyi Spinola (Hymenoptera, Andrenidae) by Stylops (Strepsiptera, Stylopidae) and revised taxonomic status of the parasite, ZooKeys 519, pp. 117-139 : 123-127

Taxon classification Animalia Strepsiptera Stylopidae

Stylops nassonowi Pierce Figs 4, 5, 6-13, 20-21, 22-26

Stylops nassonowi Pierce 1909: 105 [F]. Resurrected name [previously synonymized with Stylops melittae Kirby by Kinzelbach (1978)].

Stylops savignyi Hofender 1924: 254 [F]. New synonyms.

Diagnosis.

Female puparium. The female puparium of Stylops nassonowi is almost indistinguishable from its sibling species, Stylops aterrimus Newport (compare Figures 6-13, with Figures 14-19). There is probably no stable character that could differentiate female puparia of both species in terms of their morphology and coloration. However, the following few characters occur in one of the species with a higher probability, or are more pronounced in one of the two species: Stylops nassonowi has the prothoracic flange of the brood opening typically more produced forward, less numerous mandibular sensilla (less than 10), and pigmentation of the prothorax more uniform except a pale apical part to the abdominal segment of the cephalothoracic venter (well visible in Figures 12, 13). By contrast, Stylops aterrimus is more complex in pigmentation than Stylops nassonowi , its dark markings on the ventral surfaces of the meso- and metathorax are usually well-developed and the metathorax has a more or less distinct transverse dark band, ultimately giving its apical half a nuanced darker appearance than the basal half (well visible in Figures 14-16). Stylops nassonowi differs from other species (such as when compared to Stylops ater Reichert, Stylops melittae Kirby, Stylops nevinsoni Perkins, Stylops spreta Perkins, and Stylops thwaitesi Perkins) mainly in body and head size (larger than Stylops nevinsoni , Stylops spreta , and Stylops thwaitesi ), in the short, dark, basal band (large dark basal band in Stylops ater , Stylops nevinsoni , Stylops spreta , and Stylops thwaitesi ), described coloration of the cephalothorax, in the shape of the prothoracic flange of the brood opening (strongly curved in Stylops thwaitesi ; straight in Stylops spreta ; uniformly curved in Stylops melittae , but slightly curved in Stylops aterrimus and Stylops nassonowi ), in the shape of the head corners (strongly curved in Stylops spreta , but only slightly curved in the other species), in the shape and sclerotization of the hypostomal and cephalic ridges (strongly sclerotized and dark in Stylops melittae , but less pronounced in the other species), and the length of the clypeal sensilla.

First instar. Body elongate as in other species of Stylops except for Stylops melittae , which has wider abdomen. Head dorsally with two olfactory foveae and four pairs of setae in contrast to Stylops melittae , which has seven pairs of setae and no foveae. The frontal margin of the maxillae is not sagging in Stylops aterrimus and Stylops melittae , in contrast to that of Stylops nassonowi . The cervix is indistinct in Stylops nassonowi rather than more defined in Stylops melittae , the latter possessing a narrower head ventrally. The caudal margins of the dorsal segments have spinullae, except for the pro- and mesothoracic segments, which are covered basally (bases are covered by the tergal margin and therefore not visible rather than fully exposed), while in Stylops melittae some spinullae are covered and there is a gap in the center of dorsum where no spinullae are present. The sternal plates are broader than in Stylops melittae .

Redescription.

Female and female puparium. Head two times wider than long, width to length 1.97-2.53 (n = 13, x = 2.15 mm), width 0.60-0.76 mm (x = 0.68 mm), length 0.30-0.36 mm (x = 0.32 mm); head posteriorly defined by single incomplete or ill-defined cephalic ridge on dorsal surface, paired cephalic ridge on ventral surface and posterior head thickening (lower margin of brood opening). Head corners short and narrow on ventral surface, slightly diverging posteriorly, head corners shorter than head on dorsal surface laterally, but inner posterior extension of ventral cephalic ridge (joint of ventral cephalic ridge and posterior head thickening) extends as far as head posterior margin on dorsal surface; ventral cephalic ridge posteromedially oriented; head corners not produced laterally beyond prothorax, head narrower than prothorax and thus cephalothorax continuously diverging posteriorly. Mandibles large, not extending from head contour in ventral view; inner apical tooth well-developed; apex ventrally with 5-8 sensilla, intermandibular distance 0.17-0.20 mm (x = 0.19 mm). Labiomaxillary area about 2 –2.5× longer than wide; maxillary area distinctly prominent, overlapping mandible at about one third of its width, maxilla with 7-16 sensilla laterally; labial area without sensilla, more or less prominent and faintly divided into two parts medially (probably postmentum and prementum). Oral ridge (hypopharynx) well developed, rectangular, apically straight, occupying about half of intermandibular area; epipharynx slightly produced, pale, about as long as oral ridge. Hypostomal ridge (from outer margin of mandible to cephalic ridge and separating maxillary area from head corner) slightly sinuous, about as long as intermandibular distance or slightly longer. Labral area well developed, large, arcuate apically, slightly darker than clypeus in most specimens. Clypeus transverse, exceeding mandibles laterally and apically, apex straight or slightly concave, lateral corners prominent, with about 10-30 short sensilla laterally. Brood opening wide, distinctly wider than distance between mandibles; prothoracic flange (dorsal cover of brood opening) sclerotized, arcuate, laterally curved more than medially, apical margin almost straight, in some specimens more produced forward than in others; posterior head thickening (lower margin of brood opening) more uniformly arcuate than flange; overlap of prothoracic flange and posterior head thickening relatively short, about as long as cephalic ridge thick; joint of posterior head thickening and ventral cephalic ridge small, often serrate, slightly lighter than cephalic ridge. Cephalothorax usually slightly wider than long, but longer than wide in some specimens, width to length 0.85-1.18 (x = 1.05), width 1.05-1.41 mm (x = 1.24 mm), length 1.04-1.27 mm (x = 1.18 mm); cephalothorax compact, all segments fused, pigmentation denser laterally than medially. Pro- and mesothoracic intersegmental ridges distinct medially on ventral surface; paired pro- and mesothoracic ridges variable in size, usually distinct on dorsal surface. Pro- and mesothorax uniformly light yellowish-brown except pale prothoracic ridge and slightly darker surrounding integument, posterior part of mesothorax with pair of dark brown spots variable in size (absent in some specimens), distinct lighter area in center of mesothoracic ridge; metathorax uniformly pigmented with paired posterolateral dark brown spots (absent in some specimens); abdominal part of cephalothorax dichromatic, apical part lightest of cephalothorax, nearly transparent, and basal band dark brown, basal band short, not extending toward spiracles, division between basal band and remainder of cephalothorax nearly straight in all parts. Spiracles not prominent, positioned at widest part of posterior part of cephalothorax. Canalis prolifer on abdominal segments I–VII; single median tuba prolifera positioned on posterior third of segments II–VI.

First instar. Body length 135-192 μm (without caudal setae); caudal setae approximately one half body length; with minute terminal leaf-like structure ( “Haftlappen”: vide Pohl 2000). Head dorsally with four pairs of setae and two olfactory foveae. Mandibles with short setae. Maxillae distinct; frontal margin of maxillae emarginate; rudimentary maxillary palpi circular; ventral opening of praeoral cavity semicircular and isolated from cervix; labium reduced.

Posterior margin of dorsal tergites with spinullae, all spinullae covered basally by tergal margin except for pro- and mesothoracic segments. Each thoracic tergite with two submedian and lateral rows of setae. Coxae broad; each coxa bearing one coxal bristle and 6-7 cuticular outgrowths distributed among three coxal teeth at anterior part of coxa; coxal bristle on pro- and mesothorax at least two times as long as coxal teeth. Trochanterofemur always with femoral spur and bristle almost as long as coxal bristle, and one cuticular outgrowth. Pro- and mesotarsi elongate and slightly enlarged, metatarsi rod-like. Sternal plates broad, with one pair of setae on each plate, with a few outgrowths (about 6) on their posterior margins. Precoxal pleural membrane with small number of microtrichia (about 3) on prothorax, and with transverse row of microtrichia on meso- and metathorax. Short row of cuticular outgrowths ( “Spinulaeplatte” sensu Borchert 1963) on sternite I. Posterior margins of abdominal sternites with spinullae, some spinullae covered basally. Abdominal segment X with anus, shortened and fused with segment IX, positioned dorsally; segment XI split in two parts and positioned ventrally, bearing caudal setae.

DNA sequences.

Stylops nassonowi differs significantly in DNA barcode sequence distance, which is consistently about 4% or more from other species, including Stylops aterrimus . At the same time, the distances within the species are about 1.5% in distance or even less (Table 2). The only exception is an individual collected in eastern Turkey, which differs from all other sequenced individuals of Stylops nassonowi in 1.3-1.9% distance and might represent an isolated population or perhaps different subspecies. Greater sampling is needed across the distribution of the species, particularly the Levant and elsewhere in Arabia.