Leptotrombidium magnum (Schluger, 1960), Nagayo, Miyagawa, Mitamura and Imamura, 1916

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 : 345-348

Leptotrombidium magnum (Schluger, 1960)

( Figs. 11–13 )

Trombicula (Leptotrombidium) magna Schluger, 1960 (in Schluger et al. 1960b): 1796, fig. 4.

Leptotrombidium (Leptotrombidium) magnum : Lakshana 1973: 8; Vercammen-Grandjean & Langston 1976: 332, pl. 52; Kudryashova 2004: 25.

Leptotrombidium magnum : Stekolnikov 2013: 120 ; 2021: 122.

Leptotrombidium dooleyi Nadchatram, 1970: 150 , figs. 17–24, syn. nov.; Vercammen-Grandjean & Langston 1976: 338, pl. 56; Stekolnikov 2013: 120 .

Leptotrombidium (Leptotrombidium) submagnum Wang, Li and Shi, 1988: 140 , figs. 9–12, syn. nov.; Li et al. 1997: 178, fig. 2-1-101; Stekolnikov 2013: 119 .

Diagnosis. SIF = 7B-B-3-2111.0000; fsp = 7.7.7; fCx = 1.1.1; fSt = 2.2; fPp = N/N/BNN; fSc: AM ≥ PL> AL; Ip = 851–946; fD = 2H-(14–15)-(12–17)-(17–18)-(10–11)-(6–8)+(4–9); DS = 71–74; V = 55–56; NDV = 126–130. Standard measurements of type series given in Table 5 .

Description (larva) (based on lectotype and 17 paralectotypes, fD recorded in two specimens). IDIOSOMA ( Figs. 11A , 12B–G ). Eyes 2 + 2; 71–74 barbed dorsal idiosomal setae, including one pair of humeral setae, 14–15 setae in 1 st posthumeral row (C except humeral setae), 12–17 setae in 2 nd row (D), 17–18 setae in 3 rd row (E), 10–11 setae in 4 th row (F), 6–8 setae in 5 th row plus 4–9 caudal setae; 4 sternal setae; 55–56 ventral setae; NDV = 126–130.

GNATHOSOMA ( Fig. 13A–C ). 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; 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. 11 , 12A ). Rectangular, moderately covered with rather large puncta, greatly projected posterior to PL, posterior margin straight in middle part; AM posterior to level of AL, sensillary (trichobothrial) bases at level of PL or slightly posterior (P-PL – PSB = –5–4 µm); all scutal setae barbed similarly to dorsal idiosomal setae; AM ≥ PL> AL; flagelliform sensilla (trichobothria) with about 5 branches in distal part.

LEGS ( Fig. 13D–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, 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) at level of 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, Quang Ninh Province, ex Rattus tanezumi Temminck (= R. rattus tikos ), Leopoldamys sabanus (= Rattus sabanus ) and Tupaia belangeri chinensis (= T. glis modesta ) ( Schluger et al. 1960b). Later it was recorded in Thailand, from birds Napothera macrodactyla (Strickland) and Stachyris poliocephala (Temminck) ( Lakshana 1973) . Vercammen-Grandjean & Langston (1976) added also Tupaia glis (= T. ferruginea ) to the list of hosts, based on examination of syntypes.

Leptotrombidium dooleyi was described from Nepal, Daman, ex field mouse ( Apodemus sp. ), and from Nepal, Bokaikunde, 23 km NE Trisuli, ex Rattus nitidus (Hodgson) . Leptotrombidium submagnum was described from China, Hubei Province, Yichang County, Jiangjiamiao, ex Rattus losea (Swinhoe) .

Type material examined. Lectotype larva ( ZMMU Tdt-3268, specimen 3, designated here) ex Tupaia belangeri (labeled as T. glis and T. ferruginea ) No 29, VIETNAM: Quang Ninh Province, Ha Lam District, Ha Long (= Hon Gai), 1 February 1956, coll. I.M. Grochovskaja. Five paralectotypes larvae ( ZMMU Tdt-3262, specimen 3; ZMMU Tdt-3276, specimens 1, 2, 3, 5) ex L. edwardsi [labeled as Rattus sp. and R. grochovskii (nomen nudum)] No 36, 2 February 1956, other data same; one paralectotype larva ( ZMMU Tdt-3263, specimen 4) ex L. edwardsi [labeled as Rattus sp. and R. grochovskii (nomen nudum)] No 35, other data same; 11 paralectotypes larvae ( ZMMU Tdt-3265, specimens 1, 4; ZMMU Tdt-3266, specimens 1, 2, 4; ZMMU Tdt-3267, specimen 5; ZMMU Tdt-3268, specimens 4, 6; ZMMU Tdt-3272, specimens 1, 4, 5) with same data as lectotype.

Remarks. This species is a member of the magnum group ( Stekolnikov 2013). Its differences from L. globosum are provided above. Leptotrombidium magnum differs from L. keukenschrijveri by a larger scutum (AW 69–79, PW 79–89, and SD 51–58 vs. 59–61, 69–72, and 38–41, respectively) and by longer legs (Ip 851–946 vs. 702–738).

There are no evident differences between L. magnum and L. dooleyi , except for a longer AM (66–72 vs. 51–62) and, consequently, AM> PL vs. AM ≥ PL in the latter species that was used for discrimination of these species in the key published by Stekolnikov (2013) (couplet 270). Therefore, we synonymize here L. dooleyi with L. magnum.

Leptotrombidium submagnum is also definitely identical to L. magnum. The characters of the former species given by its authors to discriminate it from L. magnum and L. dooleyi were as follows: PL> AM> AL, PW/AP = 2.5, and 16–17 setae in 1 st posthumeral row ( Wang et al. 1988). According to our data, PW/AP = 2.47–2.89 (mean 2.69) in the type series of L. magnum. The number of setae in 1 st posthumeral row was 14 and 15 in the two paralectotypes with fD recorded. Taking into account a high level of variation in the arrangement of idiosomal setae in all chigger species with large DS, the difference between 14–15 and 16–17 cannot be estimated as taxonomically significant. The difference in the length of PL (50–59 in L. magnum and 62–66 in L. submagnum ) that resulted in AM ≥ PL vs. PL> AM is also not weighty. In addition, we can note that NDV is 118–125 in L. submagnum and 126–130 in L. magnum. This slight difference does not constitute a basis for species discrimination. Therefore, we synonymize here L. submagnum with L. magnum.

Figures

FIGURE 11. Leptotrombidium magnum (Schluger, 1960), lectotype (right sensillum lost). A, dorsal aspect of idiosoma; B, scutum. Scale bars: 50 μm.

FIGURE 12. Leptotrombidium magnum (Schluger, 1960). A, scutum of paralectotype ZMMU Tdt-3267, specimen 5 (right sensillum lost, posterior right eye not figured); B, humeral seta (C antero-marginal) of paralectotype ZMMU Tdt-3267, specimen 5; C, dorsal idiosomal seta of paralectotype ZMMU Tdt-3267, specimen 5; D, postanal seta of paralectotype ZMMU Tdt- 3267, specimen 5; E, preanal seta of paralectotype ZMMU Tdt-3267, specimen 5; F, arrangement of dorsal idiosomal setae in paralectotype ZMMU Tdt-3265, specimen 4; G, ventral aspect of idiosoma in paralectotype ZMMU Tdt-3265, specimen 4. Abbreviations as in Fig. 2. Scale bars: 50 μm (A–E), 100 μm (F, G).

FIGURE 13. Leptotrombidium magnum (Schluger, 1960), paralectotype ZMMU Tdt-3266, specimen 2. A, dorsal aspect of gnathosoma; B, galeal (deutorostral) seta; C, ventral aspect of gnathosoma (galeal seta broken); D, leg I (trochanter–tarsus); E, leg II (trochanter–tarsus); F, leg III (genu–tarsus); G, leg III (trochanter–telofemur). Abbreviations as in Fig. 2. Scale bars: 50 μm (A–C), 50 μm (D–G).