Herpetacarus (Abonnencia) alticolus (Lawrence, 1951)

Stekolnikov, Alexandr A., 2024, Revision of South African chiggers (Acariformes: Trombiculidae) originated from the collection of R. F. Lawrence, with redescriptions of nine species, Zootaxa 5493 (1), pp. 1-35 : 6-11

Herpetacarus (Abonnencia) alticolus (Lawrence, 1951)

( Figs. 2–4 )

Ascoschoengastia alticola Lawrence, 1951a: 114 , fig. 16, a.

Euschoengastia alticola : Wharton & Fuller 1952: 73; Zumpt 1961: 161.

Herpetacarus (Herpetacarus) alticola : Vercammen-Grandjean 1965b: 86; 1966: 635, pl. F, 1.

Herpetacarus (Herpetacarus) alticolus : Stekolnikov 2018: 65 .

Diagnosis. SIF = 7B-N-3-2111.1100; fPp = B/B/BN(b)B; PL> AL> AM; fD = 2H-8(7)-6-6-6+(2–7); DS = 30–35; V = 22–36; NDV = 55–66; scutum telostigmal, with evenly arquate posterior margin; sensilla widely fusiform, with pointed tip; sensillary bases at level of PLs; Ip = 560–652. Standard measurements are in Table 2 .

Redescription (larval holotype, paratype, and 3 topotypic specimens). IDIOSOMA ( Figs. 2 , 3 ). Eyes 2 + 2, in ocular plate; 30–35 dorsal idiosomal setae, including one pair of humeral setae, densely covered with long thin barbs, 8 (7 in holotype) setae in 1 st posthumeral row (C excluding humeral setae), by 6 setae in next three rows plus 2–7 caudal setae; 4 sternal setae; 22–36 ventral setae; NDV = 55–66.

GNATHOSOMA ( Fig. 4D, E ). Cheliceral blade with tricuspid cap; cheliceral base, gnathobase, and palpal femur with sparse puncta; gnathobase with 1 pair of branched gnathocoxal (tritorostral) setae; galeal (deutorostral) seta nude; palpal claw with three prongs; setae on palpal femur and genu branched; dorsal and ventral setae on palpal tibia branched; lateral palpal tibial seta nude or bearing one branch; palpal tarsus with 7 branched setae and tarsala (ω).

SCUTUM ( Figs. 2A, B , 3H–J ). Nearly hexagonal, telostigmal, moderately covered with small puncta, anterior scutal margin concave, lateral margins almost straight, posterior margin slightly projected, evenly arquate; ALs situated in projected anterior angles of scutum; AM posterior to level of ALs; sensillary (trichobothrial) bases nearly at level of PLs (PSB – P-PL = 0–2); all scutal setae uniform with dorsal idiosomal setae; PL> AL> AM; sensilla (trichobothria) widely fusiform, with pointed tip, covered with small setules.

LEGS ( Fig. 4A–C ).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) slightly distal to level of tarsala, subterminala (ζ), parasubterminala (z), pretarsala (ζ). Leg II: coxa 1B; trochanter 1B; basifemur 2B; telofemur 4B; genu 3B, genuala (σ); 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 (σ); tibia 5B, tibiala (φ), mastitibiala; tarsus 14B, mastitarsala.

Distribution and hosts. This species was described from Champagne Castle, Drakensberg Mts., Natal (currently KwaZulu-Natal Prov.), South Africa, ex Grocidura flavescens (I. Geoffroy) (Eulipotyphla: Soricidae ) and Rhabdomys pumilio (Sparrman) ( Rodentia : Muridae ).

Material examined. Holotype and one paratype larvae (on separate slides), NM 4974, ex C. flavescens, Champagne Castle, Hostel, collector and date unknown ( Fig. 1 , 6–7 ). Three topotypic specimens on one slide (the upper, the lowest, and the middle specimens), January 1951, other data same ( Fig. 1 , 8 ).

Comparative material examined. Holotype larva of Herpetacarus africanus ( Radford, 1948) (labeled as lectotype of Ascoschoengastia africana ), NHM 1948-2-3 -32, ex Otomys angoniensis Wroughton (syn. O. tugelensis pretoriae Roberts ) ( Rodentia : Muridae ), South Africa, Onderstepoort, 22 May 1939, Zoological Survey ( Fig. 1 , 9 ). Topotypic larva of H. africanus , labeled as Euschoengastia africana (Radford) , ZIN 14505, ex O. angoniensis (syn. O. t. pretoriae), Pretoria, Onderstepoort, 26 May 1939, Zoological Survey ( Fig. 1 , 10 ). Holotype larva ( ZIN 10161, T-Tr.-81) and four paratypes ( ZIN 10162, 10163, 10165, 10166) of Herpetacarus octosetosus Stekolnikov and Matthee, 2019 , ex Saccostomus campestris Peters ( Rodentia : Nesomyidae ), South Africa, Hlalakahle, January 2015, coll. S. Matthee; two paratypes larvae ( ZIN 10169, 10171) of H. octosetosus , ex Mastomys sp. , South Africa, Gottenburg, January 2015, coll. S. Matthee.

Remarks. The holotype of H. alticolus differs from the paratype and three additional specimens examined by me in a wider scutum (AW–SB) and wider sensilla (S) ( Figs. 2A , 3J ; Table 1 ) that could be caused by an unsuccessful mode of slide mounting—namely, an excessive clearing and pressure. The holotype also has a lesser number of idiosomal setae (NDV = 55), as compared with other examined specimens of H. alticolus (NDV = 62– 66). The gnathosoma is indistinctly visible in the holotype; the dorsal palpal tibial seta looks nude (fPp = B/B/NNB) vs. heavily branched in the specimen with clearly visible palps ( Fig. 4D ), but I am not sure that this difference is real. Further, I assume that this seta is branched in H. alticolus .

This species is similar to H. octosetosus and H. africanus but differs from them both in fPp = B/B/BN(b)B vs. B/B/NNB and in the morphometric characters. Among these three species, H. alticolus has the smallest scutum (measurements AW–AP), shortest setae (AM–V max), and shortest legs (pa–TaIIIL), whereas H. africanus has the largest measurements ( Table 2 ). Herpetacarus octosetosus differs from H. alticolus by the subglobose or ovoid shape of sensilla vs. fusiform. Herpetacarus alticolus also differs from H. octosetosus and H. africanus in the position of sensilla closer to the level of PLs (PSB – P-PL = 0–2 vs. 3–7).

The arrangement of dorsal idiosomal setae in H. africanus is 2H-8-6-2-6-6-4-2, according to the original description ( Radford 1948), and 2H-8-8-6-6-4, according to Vercammen-Grandjean (1966) who examined the holotype. My examination of the holotype showed that the distribution of setae by rows in this specimen is identical to that in H. alticolus ( Fig. 3A, C ), with fD = 2H-8-6-6-6+10 (see also fig. 15 in the original description). Caudal setae are visible indistinctly in the holotype that could cause the difference between the numbers of idiosomal setae (DS–NDV) after Vercammen-Grandjean (1966) and the results of my examination ( Table 1 ). Radford (1948) gave only approximate numbers (“about thirty-six”) of both dorsal and ventral idiosomal setae.

Vercammen-Grandjean (1965b, 1966) followed by Stekolnikov (2018) included H. alticolus in the subgenus Herpetacarus (Herpetacarus) without examination of any material. My examination showed that this species has no palpal subterminala (ζ) and thus should be placed in the subgenus Herpetacarus (Abonnencia) Vercammen-Grandjean, 1960 .

The “ lectotype ” of H. africanus designated by Radford (1948) is a name-bearing type fixed originally, together with paratypes, and thus it is the holotype in the modern sense (ICZN Code, Art. 73.1.1). The date 22 May 1939 on its label is probably lapsus calami since Radford (1948) gave 26 May in the species description.

Figures

FIGURE 1. Slide labels. 1, Microtrombicula homopholis, holotype; 2, Hypotrombidium subquadratum, holotype; 3, Willmannium natalense, lectotype; 4, W. natalense, paralectotype 1; 5, M. nivaria, paratype; 6, Herpetacarus (Abonnencia) alticolus, holotype; 7, H. (A.) alticolus, paratype; 8, H. (A.) alticolus, slide with topotypic specimens; 9, H. (A.) africanus, holotype; 10, H. (A.) africanus, topotypic specimen (ZIN label is on the opposite side); 11, H. (A.) longispinus, holotype; 12, H. (A.) longispinus, topotypic specimen (ZIN label is on the opposite side); 13, Ascoschoengastia rhabdomyia, slide NM 5387; 14, Riedlinia (Trombigastia) cadei, specimen NM 6544/3 (pencil inscription “/3” is mine; my identification label is on the opposite side); 15, Schoengastia pseudocordyli, slide NM 4939/1 (pencil inscriptions are mine; my identification label is on the opposite side); 16, S. scincicola, holotype; 17, S. scincicola, paratype NM 4870/2; 18, S. scincicola, paratype NHM 1957-8-12-35; 19, S. scincicola, non-type specimen (renounced paratype) NM 4870/3; 20, S. monticola, holotype; 21, S. monticola, paratype NHM 1957-8-12-34; 22, S. monticola, non-type specimen (renounced paratype) NM 4827; 23, S. monticola, specimen NM 4810/1 (pencil inscription “/1” is mine; my identification label is on the opposite side); 24, S. gerrhosauri, paratype NHM 1957-8- 12-36; 25, S. mabuyana, paratype NM 26422; 26, S. mabuyana, paratype NM 26423; 27, Microtrombicula (Microtrombicula) zumpti, specimen NM 5871/1 (pencil inscriptions are mine; my identification label is on the opposite side); 28, Neotrombicula (Anamasticula) rhodesiana, holotype.

FIGURE 2. Herpetacarus (Abonnencia) alticolus (Lawrence, 1951), holotype (A), topotypic specimen, lowest on the slide (B, C), topotypic specimen, middle on the slide (D). A, B, scutum; C, dorsal aspect of idiosoma; D, ventral aspect of idiosoma; Scale bars: 50 µm.

FIGURE 3. Herpetacarus (Abonnencia) alticolus (Lawrence, 1951), holotype (A, B, J), topotypic specimen, middle on the slide (C, D), paratype (E–I). A, C, dorsal aspect of idiosoma; B, ventral aspect of idiosoma; D, arrangement of ventral idiosomal setae; E, humeral seta; F, dorsal idiosomal seta; G, preanal seta; H, J, scutum and eyes; I, sensillum. Abbreviations: AL, anterolateral scutal seta; AM, anteromedian scutal seta; H, humeral seta; PL, posterolateral scutal seta; u, uropore (anus); V, ventral idiosomal setae. Borders between rows of setae are showed by dotted lines. Scale bars: 100 µm (A–D), 20 µm (E–G), 50 µm (H–J).

FIGURE 4. Herpetacarus (Abonnencia) alticolus (Lawrence, 1951), topotypic specimen, lowest on the slide. A, leg I, trochanter–tarsus; B, leg II, trochanter–tarsus; C, leg III, trochanter–tarsus; D, dorsal aspect of gnathosoma; E, ventral aspect of gnathosoma. Abbreviations: Cb, cheliceral base; Cs, cheliceral blade; 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); ic, infracapitulum (gnathobase, gnathocoxa); MTa, mastitarsala; MTi, mastitibiala; PC, palpal claw (odontus); PF, palpal femur; PG, palpal genu; pST, parasubterminala (z); PT’, pretarsala I (ζ); PT”, pretarsala II (ζ); PTa, palpal tarsus; PTi, palpal tibia; S0, palpal tarsala (ω); S1, leg tarsala I (ω); S2, leg tarsala II (ω); ST, leg subterminala (ζ); ta, tibiala I (φ); tm, tibiala II (φ); tp, tibiala III (φ); µga, microgenuala I (κ); µta, microtibiala I (κ). Scale bars: 50 µm (A–C), 20 µm (D, E).

FIGURE 6. Ascoschoengastia rhabdomyia Lawrence, 1951, specimen NM 5387, third from right on the slide. A, dorsal aspect of idiosoma; B, arrangement of ventral idiosomal setae; C, scutum and eyes (sensilla missing); D, sensillum; E, dorsal idiosomal seta; F, preanal idiosomal seta; G, dorsal aspect of gnathosoma; H, ventral aspect of gnathosoma; I, leg I, trochanter–tarsus; J, leg II, trochanter–tarsus; K, leg III, trochanter–tarsus. Abbreviations as in Figs. 3 and 4. Scale bars: 100 µm (A, B), 50 µm (C, D), 20 µm (E, F), 20 µm (G, H), 50 µm (I–K).

FIGURE 7. Riedlinia (Trombigastia) cadei (Vercammen-Grandjean and Brennan, 1957), specimens NM 6544/1 (A, B), 6544/2 (D–K), 6544/3 (C). A, dorsal aspect of idiosoma; B, arrangement of ventral idiosomal setae; C, scutum (with only one broken sensillum) and eyes; D, dorsal idiosomal seta; E, preanal idiosomal seta; F, ventral aspect of gnathosoma; G, dorsal aspect of gnathosoma (dorsal palpal tibial seta invisible); H, palp, dorsal aspect; I, leg I, trochanter–tarsus; J, leg II, trochanter–tarsus; K, leg III, trochanter–tarsus. Abbreviations: S, sensillum; other abbreviations as in Fig. 3. Scale bars: 100 µm (A, B), 50 µm (C), 20 µm (D, E), 20 µm (F–H), 50 µm (I–K).

FIGURE 8. Schoengastia pseudocordyli Lawrence, 1949, specimen NM 4939/3. A, dorsal aspect of idiosoma; B, scutum. Scale bars: 50 µm.

FIGURE 9. Schoengastia pseudocordyli Lawrence, 1949, specimen NM 4939/3. A, dorsal aspect of idiosoma; B, arrangement of ventral idiosomal setae; C, scutum and eyes; D, humeral seta; E, dorsal idiosomal seta; F, preanal idiosomal seta; G, galeal (deutorostral) seta; H, dorsal aspect of gnathosoma; I, ventral aspect of gnathosoma; J, leg I, trochanter–tarsus; K, leg II, trochanter–tarsus; L, leg III, trochanter–tarsus. Abbreviations: S, sensillum; ζ, palpal subterminala (ζ); other abbreviations as in Figs. 3 and 4. Scale bars: 100 µm (A, B), 50 µm (C), 20 µm (D–F), 20 µm (G–I), 50 µm (J–L).

FIGURE 10. Schoengastia scincicola Lawrence, 1949, holotype (A), paratype NM 4870/2 (B, D), paratype NHM 1957-8-12- 35 (C). A–C, dorsal aspect of idiosoma; D, scutum. Scale bars: 50 µm.