Leptotrombidium arvinum (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 : 331-332

Leptotrombidium arvinum (Schluger, 1960)

( Figs. 1 , 2 )

Trombicula (Leptotrombidium) arvina Schluger, 1960 (in Schluger et al. 1960b): 1792, fig. 2.

Leptotrombidium (Leptotrombidium) arvina: Traub & Lakshana 1966: 271 , figs. 1–5; Lakshana 1973: 6; Chau et al. 2007: 40, fig. 15.

Leptotrombidium (Leptotrombidium) miculum arvinum: Vercammen-Grandjean & Langston 1976: 422 , pl. 100; Xiang & Wen 1984: 260; Wen 1984: 308.

Leptotrombidium (Leptotrombidium) arvinum: Kudryashova 2004: 13 .

Leptotrombidium arvinum: Chaisiri et al. 2016: 323 ; Stekolnikov 2013: 69 ; 2021: 112.

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 = 601–625; fD = 2H-8-6-6-2-2; DS = 26–28; V = 23–24; NDV = 49–52. Standard measurements of type series given in Table 1 .

Description (larva) (based on lectotype and 2 paralectotypes, fD recorded in one specimen). IDIOSOMA ( Figs. 1A , 2B–G ). Eyes 2 + 2; 26–28 barbed dorsal idiosomal setae, including one pair of humeral setae, arranged 2H-8-6-6-2-2; 4 sternal setae; 23–24 ventral setae; NDV = 49–52.

GNATHOSOMA ( Fig. 2H, I ). Cheliceral blade with tricuspid cap; gnathobase with sparse puncta and 1 pair of branched gnathocoxal (tritorostral) setae; proximal part of cheliceral base and palpal femur with sparse 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. 1 , 2A ). Rectangular, moderately covered with rather large puncta, greatly projected posterior to PL, posterior margin almost straight in middle part; AM posterior to level of AL, sensillary (trichobothrial) bases posterior to level of PL (P-PL – PSB = 6–8 µm); AL and PL densely covered with rather long thin barbs, PL slightly expanded proximally, covered with shorter and wider barbs, similarly to dorsal idiosomal setae; PL> AM> AL; flagelliform sensilla (trichobothria), with about 11 long branches in distal half.

LEGS ( Fig. 2J–L ). 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 21B, 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 15B.

Distribution and hosts. This species was described from North Vietnam, Nghe An Province, ex Tupaia sp. ( Schluger et al. 1960b). Later on, it was recorded in the following countries: in Thailand, from mammals Tupaia glis (Diard and Duvaucel) , Callosciurus caniceps (Gray) , C. erythraeus (Pallas) , C. finlaysonii (Horsfield) , Crocidura horsfieldii (Tomes) , Hylomys suillus S. Müller , Maxomys rajah (Thomas) (= Rattus rajah ), Menetes berdmorei (Blyth) , Niviventer niviventer (Hodgson) (= Rattus niveiventer ), Rattus rattus (L.), Berylmys berdmorei (Blyth) (= Rattus berdmorei ), Paradoxurus hermaphroditus (Pallas) , and birds Chalcophaps indica (L.), Pellorneum ruficeps Swainson ( Traub & Lakshana 1966), and Leopoldamys sabanus (= Rattus sabanus ) ( Lakshana 1973); in Laos, from T. glis and Dremomys rufigenis (Blanford) ; in Malaysia, from Tupaia sp. and Callosciurus caniceps (Vercammen- Grandjean & Langston 1976), and in China, from the specimens collected with a black plate ( Wen 1984).

Type material examined. Lectotype larva ( ZMMU Tdt-3144, specimen 4, designated here) ex Tupaia sp. No 611, VIETNAM: Nghe An Province, Phu Quy, 15 September 1956, coll. I.M. Grochovskaja. One paralectotype larva ( ZMMU Tdt-3144, specimen 2) with same data as lectotype; one paralectotype larva ( ZMMU Tdt-3143, specimen 3) ex Tupaia sp. No 610, other data same as for lectotype.

Remarks. According to the cluster analysis performed by Stekolnikov (2013), L. arvinum belongs to the arvinum species group, which includes also L. saigoni Stekolnikov, 2013 . The latter was described as Leptotrombidium (Leptotrombidium) miculum arvinum var. saigoni Vercammen-Grandjean and Langston, 1976 , from a single specimen, and raised to species by Stekolnikov (2013). This species differs from L. arvinum by the presence of 10 setae in 1 st posthumeral row, vs. 8, NDV = 58 vs. 49–52, and by slightly longer legs (Ip = 732 vs. 601–625).

Vercammen-Grandjean & Langston (1976) included L. arvinum in L. miculum , as a subspecies. However, according to Stekolnikov (2013), L. miculum belongs to the arenicola species group. The latter species differs from L. arvinum in having the sensillary bases situated at the level of PL vs. posterior to PL, shorter scutal setae (AM 32–38, AL 27–32, and PL 40–46, vs. 44–50, 35–39, 59–64, respectively), shorter idiosomal setae (H 41–43, D min 31–32, D max 37–40, and V max 31–33 vs. 60–61, 34–40, 52–55, and 33–45, respectively), and slightly shorter legs (Ip 554–602 vs. 601–625).

Figures

FIGURE 1. Leptotrombidium arvinum (Schluger, 1960), paralectotype ZMMU Tdt-3144, specimen 2. A, dorsal aspect of idiosoma; B, scutum. Scale bars: 50 μm.

FIGURE 2. Leptotrombidium arvinum (Schluger, 1960). A, scutum of lectotype (right sensillum lost, right AL broken); B, humeral seta (C antero-marginal) of lectotype; C, dorsal idiosomal seta of 2nd posthumeral row (D) of lectotype; D, postanal seta of lectotype; E, preanal seta of lectotype; F, arrangement of dorsal idiosomal setae in paralectotype ZMMU Tdt-3144, specimen 2; G, ventral aspect of idiosoma in paralectotype ZMMU Tdt-3144, specimen 2; H, dorsal aspect of gnathosoma of lectotype; I, ventral aspect of gnathosoma of lectotype; J, leg I (trochanter–tarsus) of lectotype (one claw lost); K, leg II (trochanter–tarsus) of lectotype; L, leg III (trochanter–tarsus) of lectotype. Abbreviations: AL, anterolateral scutal seta; AM, anteromedian scutal seta; Cb, cheliceral base; Cs, cheliceral blade; cxI, leg coxa I; cxII, leg coxa II; cxIII, leg coxa III; f1, microtarsala I (ε); f2, microtarsala II (ε); Ga, galeal (deutorostral) seta; ga, genuala I (σ); gm, genuala II (σ); gns, gnathocoxal (tritorostral) seta; gp, genuala III (σ); H, humeral seta; ic, infracapitulum (gnathobase); µga, microgenuala I (κ); µta, microtibiala I (κ); PC, palpal claw (odontus); PF, palpal femur; PG, palpal genu; PL, posterolateral scutal seta; pST, parasubterminala (z); PT’, pretarsala I (ζ); PT”, pretarsala II (ζ); PTa, palpal tarsus; PTi, palpal tibia; S, sensillum; S0, palpal tarsala (ω); S1, leg tarsala I (ω); S2, leg tarsala II (ω); ST, subterminala (ζ); sta, anterior sternal setae; stp, posterior sternal setae; ta, tibiala I (φ); tm, tibiala II (φ); tp, tibiala III (φ); V, ventral idiosomal setae; u, uropore (anus). Scale bars: 50 μm (A–E), 100 μm (F, G), 50 μm (H, I), 50 μm (J–L).