Leptotrombidium horridum (Schluger, 1960)

Stekolnikov, Alexandr A. & Antonovskaia, Anastasia A., 2021, Re-descriptions of eight chigger mite species (Acariformes: Trombiculidae) of the Leptotrombidium generic complex from Vietnam, Zootaxa 5057 (3), pp. 329-363 : 341-344

Leptotrombidium horridum (Schluger, 1960)

( Figs. 8–10 )

Trombicula (Leptotrombidium) horrida Schluger, 1960 (in Schluger et al. 1960b): 1790, fig. 1.

Leptotrombidium (Leptotrombidium) horridum: Vercammen-Grandjean & Langston 1976: 560 , pl. 152.

Leptotrombidium horridum: Stekolnikov 2013: 88 ; 2021: 118.

Diagnosis. SIF = 7B-B-3-2111.0000; fsp = 7.7.7; fCx = 1.1.1; fSt = 2.2; fPp = N/N/BNN; fSc: PL> AM> AL; Ip = 851–990; fD = 2H-(9–11)-8-(7–11)-6+(8–12); DS = 42–48; V = 38–46; NDV = 83–93. Standard measurements of type series given in Table 4 .

Description (larva) (based on lectotype and 24 paralectotypes, fD recorded in four specimens). IDIOSOMA ( Figs. 8A , 9B–G ). Eyes 2 + 2; 42–48 barbed dorsal idiosomal setae, including one pair of humeral setae, 9–11 setae in 1 st posthumeral row (C except humeral setae), 8 setae in 2 nd row (D), 7–11 setae in 3 rd row (E), 6 setae in 4 th row (F) plus 8–12 caudal setae; 4 sternal setae; 38–46 ventral setae; NDV = 83–93.

GNATHOSOMA ( Fig. 10A, B ). Cheliceral blade with tricuspid cap; gnathobase covered with puncta and bears 1 pair of branched gnathocoxal (tritorostral) setae; cheliceral base and palpal femur covered with puncta, palpal genu with few puncta; galeal (deutorostral) seta branched; palpal claw with 3 prongs; setae on palpal femur and genu nude, dorsal palpal tibial seta branched, lateral and ventral palpal tibial setae nude; palpal tarsus with 7 branched setae and tarsala (ω).

SCUTUM ( Figs. 8 , 9A ). Rectangular, moderately covered with rather large puncta, greatly projected posterior to PL, posterior margin slightly concave in middle part; AM posterior to level of AL, sensillary (trichobothrial) bases at level of PL or slightly posterior (P-PL – PSB = 0–6 µm); all scutal setae barbed similarly to dorsal idiosomal setae; PL ≥ AM> AL; flagelliform sensilla (trichobothria) with about 7 branches in distal half.

LEGS ( Fig. 10C–E ).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, 2 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) posterior to tarsala, pretarsala (ζ). Leg III: coxa 1B; trochanter 1B; basifemur 2B; telofemur 3B; genu 3B, genuala; tibia 6B, tibiala; tarsus 14B.

Distribution and hosts. This species was described from North Vietnam, Quang Ninh Province, ex Leopoldamys sabanus (= Rattus sabanus ) and Tupaia belangeri chinensis (= T. glis modesta ) ( Schluger et al. 1960b). Vercammen- Grandjean & Langston (1976) added also Leopoldamys edwardsi (Thomas) [= Rattus grochovskiae (nomen nudum)] and Tupaia glis (= T. ferruginea ) to the list of hosts, on the base of examination of syntypes.

Type material examined. Lectotype larva ( ZMMU L. horridum _04, specimen 5, designated here) ex Leopoldamys edwardsi [labeled as R. grochovskii (nomen nudum)] No 36, VIETNAM: Quang Ninh Province, Ha Lam District, Ha Long (= Hon Gai), 2 February 1956, coll. I.M. Grochovskaja. Eight paralectotypes larvae ( ZMMU L. horridum _01, specimens 1–3; ZMMU L. horridum _06, specimen 2; ZMMU L. horridum _08, specimens 4, 5; ZMMU L. horridum _09, specimens 2, 5; ZMMU Tdt-3248, specimen 2) ex L. edwardsi [labeled as R. grochovskii (nomen nudum)] No 40, 3 February 1956, other data same as for lectotype; three paralectotypes larvae ( ZMMU Tdt-3245, specimen 5; ZMMU Tdt-3246, specimens 2, 3) ex Tupaia belangeri [labeled as T. glis and T. hongaiensis (nomen nudum)] No 42, 3 February 1956, other data same; one paralectotype larva ( ZMMU Tdt-3249, specimen 2) ex L. edwardsi [labeled as Rattus sp. and R. grochovskii (nomen nudum)] No 44, 6 February 1956, other data same; one paralectotype larva ( ZMMU Tdt-3250, specimen 4) ex L. edwardsi [labeled as Rattus sp. and R. grochovskii (nomen nudum)] No 45, 6 February 1956, other data same; five paralectotypes larvae ( ZMMU Tdt-3260, specimen 2; ZMMU Tdt-3261, specimens 3, 4, 6; ZMMU Tdt-3262, specimen 1) with same data as lectotype; five paralectotypes larvae ( ZMMU Tdt-3264, specimen 4; ZMMU Tdt-3265, specimens 3, 5; ZMMU Tdt-3268, specimen 5; ZMMU Tdt-3272, specimen 3) ex Tupaia belangeri (labeled as T. glis and T. ferruginea ) No 29, 1 February 1956, other data same.

Remarks. Leptotrombidium horridum belongs to the alopeciatum group, which includes five species ( Stekolnikov 2013). It differs from L. spicatum Traub, 1960 , L. baluense (Traub and Audy, 1954) , and L. tupaianum Vercammen-Grandjean and Langston, 1976 in having the PL and dorsal idiosomal setae covered with usual uniform barbs vs. bearing 2–3 rows of short barbs and two lateral rows of large spikes. Leptotrombidium horridum differs from L. alopeciatum by the presence of nude ventral palpal tibial setae vs. branched (fPp = N/N/BNN vs. N/N/ BNB); by nearly doubled number of idiosomal setae (DS 42–48, V 38–46, and NDV 83–93 vs. 22, 22, and 44, respectively); by PL> AM vs. AM> PL; by sensillary bases situated at the level or posterior to SB vs. anterior; and by longer legs (Ip = 851–990 vs. 718–745).

Figures

FIGURE 8. Leptotrombidium horridum (Schluger, 1960), lectotype. A, dorsal aspect of idiosoma; B, scutum. Scale bars: 50 μm.

FIGURE 9. Leptotrombidium horridum (Schluger, 1960), lectotype. A, scutum; B, preanal seta; C, postanal seta; D, humeral seta (C antero-marginal); E, dorsal idiosomal seta; F, arrangement of dorsal idiosomal setae; G, ventral aspect of idiosoma. Abbreviations as in Fig. 2. Scale bars: 50 μm (A–E), 100 μm (F, G).

FIGURE10. Leptotrombidium horridum(Schluger, 1960).A, dorsal aspect of gnathosoma of paralectotype ZMMU L.horridum_ 01, specimen 1; B, ventral aspect of gnathosoma of paralectotype ZMMU L. horridum_01, specimen 1. C, leg I (trochanter– tarsus) of lectotype; D, leg II (trochanter–tarsus) of lectotype; E, leg III (trochanter–tarsus) of lectotype.Abbreviations as in Fig. 2. Scale bars: 50 μm (A, B), 50 μm (C–E).