Afrotrombicula (Afrotrombicula) nigeriensis ( Ewing, 1928 )

Stekolnikov, Alexandr A., 2023, A revision of the chigger genus Afrotrombicula (Acariformes: Trombiculidae), Zootaxa 5323 (1), pp. 27-55 : 36-39

Afrotrombicula (Afrotrombicula) nigeriensis ( Ewing, 1928)

( Figs. 7 , 8 )

Trombicula nigeriensis Ewing, 1928: 78 ; Radford 1942: 60; Taufflieb 1960: 224; Audy & Vercammen-Grandjean 1961: 132; Zumpt 1961: 138; Bassini-Silva et al. 2021: 80.

Trombicula (Trombicula) nigeriensis: Thor & Willmann 1947: 269 ; Wharton & Fuller 1952: 68.

Afrotrombicula (Afrotrombicula) nigeriensis: Kolebinova & Vercammen-Grandjean 1978: 103 , fig. 9B; 1981: 417. Neotrombicula nigeriensis: Whitaker et al. 1983: 31 .

Afrotrombicula nigeriensis: Stekolnikov 2018: 123 ; 2019: 27 .

Diagnosis. SIF = 7BS-B-3-3111.1000; fPp = B/B/NNB; PL> AM> AL; fD = 2H-6-8-8-… or 2H-6-6-6-…, next rows ambiguous; DS = 37–50; V = 51–67; NDV = 97–112; palpal femur and genu with puncta; scutum nearly hexagonal, almost as long as wide, with dense small puncta; posterior scutal margin prominent, straight or slightly concave in center and obliquely cut at edges; f 1 distal to S 1; f 2 behind S 2; Ip = 908–963. Standard measurements are given in Table 2 .

Redescription (7 non-type specimens). IDIOSOMA ( Fig. 7 ). Eyes 2 + 2; 37–50 dorsal idiosomal setae, including one pair of humeral setae, covered with well-developed barbs, 6 setae in 1 st posthumeral row (C, excluding humeral setae), 6 or 8 setae in 2 nd row (D), 6 or 8 setae in 3 rd row (E), distribution of posterior setae by rows ambiguous; 4 sternal setae; 51–67 ventral setae; NDV = 97–112.

GNATHOSOMA ( Fig. 8B–D ). Cheliceral blade with tricuspid cap and 1 weakly developed dorsal tooth; cheliceral base, gnathobase, and palpal femur with dense puncta, palpal genu with few puncta; gnathobase with 1 pair of branched gnathocoxal (tritorostral) setae; galeal (deutorostral) seta thick and branched; palpal claw with 3 prongs; setae on palpal femur and genu branched; dorsal and lateral setae on palpal tibia nude; ventral palpal tibial seta branched; palpal tarsus with 7 branched setae, nude subterminala (ζ) and basal tarsala (ω).

SCUTUM ( Fig. 8A ). Nearly hexagonal, almost as long as wide, densely covered with small puncta, anterior scutal margin slightly sinuous, lateral margins almost straight and parallel, posterior margin prominent, straight or slightly concave in center and obliquely cut at edges; AM at level of AL, sensillary (trichobothrial) bases at about equal distances from AL and PL; all scutal setae uniform with dorsal idiosomal setae; PL> AM> AL; flagelliform sensilla (trichobothria), with ca. 5 branches in distal part.

LEGS ( Fig. 8E–G ). All 7-segmented, with 1 pair of claws and claw-like empodium. Leg I: coxa with 1 branched seta (1B); trochanter 1B; basifemur 1B; telofemur 5B; genu 4B, 3 genualae (σ), microgenuala (κ); tibia 8B, 2 tibialae (φ), microtibiala (κ); tarsus 22B, tarsala (ω), microtarsala (ε) distal to tarsala, subterminala (ζ), parasubterminala (z), pretarsala (ζ). Leg II: coxa 1B; trochanter 1B; basifemur 2B; telofemur 4B; genu 3B, genuala; tibia 6B, 2 tibialae (φ); tarsus 16B, tarsala (ω), microtarsala (ε) behind tarsala, pretarsala (ζ). Leg III: coxa 1B; trochanter 1B; basifemur 2B; telofemur 3B; genu 3B, genuala; tibia 6B, tibiala; tarsus 14B, mastitarsala.

Type deposition. 49 syntypes (USNMENT 01758355–01758403) in USNM ( Bassini-Silva et al. 2021) .

Distribution and hosts. This species was described from Nigeria (Ibadan) ex Funisciurus leucogenys oliviae (Dollman) (syn. Funisciurus auriculatus oliviae ), F. anerythrus (Thomas) ( Rodentia : Sciuridae ), and Lemniscomys striatus (L.) ( Rodentia : Muridae ). Whitaker et al. (1983) reported this species ex Lophuromys sikapusi and Rattus rattus (L.) from the same locality (Ibadan). Stekolnikov (2019) added one more locality ( Nigeria, Ilashe) and host, F. pyrrhopus (F. Cuvier) , based on the material from the personal collection of Vercammen-Grandjean.

Material examined. Seven specimens ( MHNG) ex Funisciurus pyrrhopus , 4 mi. S. Ilashe, Western Region , Nig [eria] ( Nigeria, Ilashe, 6°42′ N, 2°47′ E), 9 Nov. 1966, collector J.C.G[eest], identified by V-G (P.H. Vercammen-Grandjean) .

Remarks. Ewing (1928) described Afrotrombicula nigeriensis quite briefly, without data on the setation of legs and palps, without illustrations and standard measurements; it has never been redescribed afterwards. Kolebinova & Vercammen-Grandjean (1978) provided a drawing of its scutum, and later, these authors ( Kolebinova & Vercammen-Grandjean 1981) gave its measurements to compare with A. gabonica , but apparently based on the aforementioned new material from the personal collection of Vercammen-Grandjean (currently deposited in MHNG). It is evident because these measurements (except for the leg lengths) almost exactly coincide with the mean for seven specimens from MHNG ( Table 2 ). Moreover, these authors did not report about examination of the A. nigeriensis type series.

The chigger collection of USNM was inaccessible to me, therefore I provisionally rely on the material from MHNG, but an examination of the type series is highly desirable to confirm the species identity. Some details of the original description give evidence that the specimens examined by Ewing (1928) could be different from the material identified by Vercammen-Grandjean. Thus, Ewing stated that in Trombicula nigeriensis “dorsal plate much broader than long, posterior margin broadly and almost evenly rounded”, whereas in the above material, the scutum is only slightly wider than long (mean PW = 85 and mean SD = 76), and its posterior margin is not rounded broadly and evenly ( Fig. 8A ) .

Figures

FIGURE 7. Afrotrombicula nigeriensis (Ewing, 1928), non-type material from MHNG. A, arrangement of dorsal idiosomal setae; B, arrangement of ventral idiosomal setae (anus invisible); C, dorsal idiosomal seta; D, preanal seta. Abbreviations as in Fig. 5. Scale bars: 100 µm (A, B), 20 µm (C, D).

FIGURE 8. Afrotrombicula nigeriensis (Ewing, 1928), non-type material from MHNG. A, scutum and eyes; B, ventral aspect of gnathosoma (cheliceral blade lost, setae of palpal tarsus invisible); C, ventral aspect of palpal tibia and tarsus (ventral tibial seta lost); D, dorsal aspect of gnathosoma; E, leg I, genu–tarsus; F, leg II, genu–tarsus; G, leg III, genu–tarsus.Abbreviations as in Fig. 6. Scale bars: 50 µm (A, E–G), 20 µm (B–D).