Leptotrombidium globosum (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 : 334-337

Leptotrombidium globosum (Schluger, 1960)

( Figs. 3–5 )

Trombicula (Leptotrombidium) globosa Schluger, 1960 (in Schluger et al. 1960b): 1796, fig. 5.

Leptotrombidium (Leptotrombidium) globosum: Lakshana 1973: 7 ; Vercammen-Grandjean & Langston 1976: 337, pl. 55; Kudryashova 2004: 19; Chau et al. 2007: 47, fig. 19.

Leptotrombidium globosum: Stekolnikov 2013: 119 ; 2021: 117.

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 = 746–776; fD = 2H-(10–12)-(15–22)+(53–61); DS = 85–90; V = 67–73; NDV = 152–162. Standard measurements of type series given in Table 2 .

Description (larva) (based on lectotype and 3 paralectotypes, fD recorded in three specimens). IDIOSOMA ( Figs. 3A , 4B–G ). Eyes 2 + 2; 85–90 barbed dorsal idiosomal setae, including one pair of humeral setae, 10–12 setae in 1 st posthumeral row (C except humeral setae), 15–22 setae in 2 nd posthumeral row (D) plus 53–61 setae with unclear distribution by rows (sometimes 3 rd row, E, with 26–28 setae, recognized); 4 sternal setae; 67–73 ventral setae; NDV = 152–162.

GNATHOSOMA ( Fig. 5A, 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; 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. 3 , 4A ). Nearly rectangular, moderately covered with rather large puncta, posterior margin broadly rounded; AM posterior to level of AL, sensillary (trichobothrial) bases at level of PL or slightly posterior (P-PL – PSB = 1–3 µm); all scutal setae barbed similarly to dorsal idiosomal setae; PL ≥ AM> AL; flagelliform sensilla (trichobothria), with about 7–8 long branches in distal half.

LEGS ( Fig. 5C–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 15B.

Distribution and hosts. This species was described from North Vietnam, Quang Ninh Province, ex Leopoldamys sabanus (Thomas) (= Rattus sabanus ) ( Schluger et al. 1960b). Vercammen-Grandjean & Langston (1976) added to the list of hosts Leopoldamys edwardsi (Thomas) [= Rattus grochovskiae D. Tien (nomen nudum)] and Tupaia belangeri chinensis (Anderson) (= T. glis modesta ), based on examination of syntypes. Later it was also recorded from Thailand, ex Mus sp. , Niviventer niviventer (= Rattus niviventer ), and T. glis ( Lakshana 1973) .

Type material examined. Lectotype larva ( ZMMU Tdt-3276, specimen 4, designated here) ex L. edwardsi [labeled as Rattus sp. and R. grochovskii (nomen nudum)] No 36, VIETNAM: Quang Ninh Province, Ha Lam District, Ha Long (= Hon Gai), 2 February 1956, coll. I.M. Grochovskaja. Three paralectotypes larvae ( ZMMU Tdt- 3260, specimen 1; ZMMU Tdt-3261, specimen 1; ZMMU Tdt-3262, specimen 5) with same data as lectotype.

Remarks. Leptotrombidium globosum belongs to the magnum species group, which includes, in total, 15 species ( Stekolnikov 2013). It differs from L. magnum (Schluger, 1960) (and two species synonymized with it in the present paper, L. dooleyi Nadchatram, 1970 and L. submagnum Wang, Li and Shi, 1988 ) in having the posterior scutal margin evenly rounded from the level of PL vs. greatly projected posterior to PL and straight in the middle part, the lesser number of setae in 1 st posthumeral row (10–12 vs. 14–17), greater NDV (152–162 vs. 118–130); smaller scutum (PW 74–77, SB 30–33, and SD 46–49 vs. 79–89, 33–39, and 51–58, respectively); PL> AM vs. AM ≥ PL, and shorter legs (Ip = 746–776 vs. 851–946).

Leptotrombidium globosum differs from L. keukenschrijveri (Walch, 1924) in having the evenly rounded posterior margin of scutum (vs. slightly bilobate and concave in center); by PL> AM vs. AM> PL; by greater NDV (152–162 vs. 114), by 10–12 setae in 1 st posthumeral row vs. 16 (8 + 8), and by larger scutum (AW 64–68, PW 74–77, and SD 46–49 vs. 59–61, 69–72, and 38–41, respectively).

Remaining species of the magnum group were described in 1980s–1990s in China ( L. arctonycis Xiang and Wen, 1984 , L. baoshui Wen and Xiang, 1984 , L. biji Wen and Xiang, 1984 , L. caudatum Wen, Zhou, Chen, Wang and Zhang, 1984 , L. huangchuanense Yang, 1994 , L. kunshui Wen and Xiang, 1984 , L. shuiqui Liao and Yuan, 1998 , L. shuminense Zhang, Deng and Wang, 1996 , L. sixinum Wen, Zhou, Chen, Wang and Zhang, 1984 , and L. xianglinense Wen, 1984 ). Two of them, L. arctonycis and L. xianglinense , are known only from the holotypes. Differences of all these species from L. globosum , L. magnum, and L. keukenschrijveri require further investigation.

Among these species from China, L. sixinum is the most probable candidate for the synonymization with L. globosum . The former species differs from L. globosum in PW 83–85 vs. 74–77, AM ≥ PL vs. PL> AM, lesser NDV (132 vs. 152–162), and in slightly longer legs (Ip 835 vs. 746–776). Statistical and taxonomic significance of these differences can not be estimated without a direct comparison of the type series. Two other species, L. biji and L. caudatum , are also similar to L. globosum by the shape of scutum, but differ in its greater size (in L. biji, AW 70–80, PW 85–103, AP 33–38; in L. caudatum, AW 73–79, PW 85–88, ASB 35–42; in L. globosum, AW 64–68, PW 74–77, ASB 32–33, AP 26–30) and in AM ≥ PL vs. PL> AM. Leptotrombidium biji also differs from L. globosum in much longer legs (Ip 1015–1049 vs. 746–776); L. caudatum has longer setae (AM 64–75, AL 48–56, PL 65–72, H 73–75 vs. 52–56, 44–47, 56–61, and 60–65, respectively) and lesser NDV (116 vs. 152–162).

Figures

FIGURE 3. Leptotrombidium globosum (Schluger, 1960). A, dorsal aspect of idiosoma in paralectotype ZMMU Tdt-3275, specimen 4; B, scutum of lectotype. Scale bars: 50 μm.

FIGURE 4. Leptotrombidium globosum (Schluger, 1960). A, scutum of lectotype; B, humeral seta (C antero-marginal) of lectotype; C, dorsal idiosomal seta of lectotype; D, postanal seta of lectotype; E, preanal seta of lectotype; F, arrangement of dorsal idiosomal setae in paralectotype ZMMU Tdt-3260, specimen 1; G, ventral aspect of idiosoma in paralectotype ZMMU Tdt-3260, specimen 1. Abbreviations as in Fig. 2. Scale bars: 50 μm (A–E), 50 μm (F, G).

FIGURE 5. Leptotrombidium globosum (Schluger, 1960). A, dorsal aspect of gnathosoma of lectotype; B, ventral aspect of gnathosoma of lectotype; C, leg I (trochanter–tarsus) of paralectotype ZMMU Tdt-3260, specimen 1; D, leg II (trochanter–tarsus) of paralectotype ZMMU Tdt-3260, specimen 1; E, leg III (trochanter–tarsus) of paralectotype ZMMU Tdt-3260, specimen 1. Abbreviations as in Fig. 2. Scale bars: 50 μm (A, B), 50 μm (C–E).