Acantholaelaps strategus

Joharchi, Omid, Halliday, Bruce, Tolstikov, Andrei V. & Trach, Viacheslav A., 2019, New records and new species of mites from Cuba, with description of a new genus of Laelapidae (Acari: Mesostigmata), Zootaxa 4612 (3), pp. 326-350: 331-339

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Acantholaelaps strategus

sp. nov.

Acantholaelaps strategus  sp. nov.

( Figures 12–52View FIGURES 12–16View FIGURES 17–20View FIGURES 21–26View FIGURES 27–32View FIGURES 33–36View FIGURES 37–38View FIGURES 39–40View FIGURES 41–44View FIGURES 45–46View FIGURES 47–52)

Female (n= 20).

Dorsal idiosoma ( Figures 12View FIGURES 12–16, 17, 18View FIGURES 17–20, 21, 23, 24, 26View FIGURES 21–26). Length 985–1150, width 525–593 (with variation in size) ( Figures 19 and 20View FIGURES 17–20). Dorsal shield oval, without lateral incisions, with very faint reticulate ornamentation ( Figures 12View FIGURES 12–16, 17, 18View FIGURES 17–20, 21, 23, 24, 26View FIGURES 21–26). Dorsal shield with 28 pairs of smooth and pointed setae (often appear wavy in slidemounted specimens), 15 pairs on podonotal shield (j1–6, z1–6, s1; s5–6), plus s2–4 and r2–6 off the shield in the soft skin, 13 pairs on the opisthonotal shield (J1–5, Z1 –5, S1, S2, S5); S5 longest (610–620), slightly wavy ( Figure 26View FIGURES 21–26), z1 shortest (25–27), z2 (150–180), z3 (290–370), z4 (227–290), z5 (150–190), z6 (240–310), j1 (114–120), j2 (130–170), j3 (262–300), j4 (75–120), j5 (112–117), j6 (99–150), J1 (56–120), J2 (63–130), J3, J4 (100–150), J5 (89–100). Setae s2–4 and r2–6, S 3–6, R1–6 and UR1–6 (64–90) on the lateral area of weakly sclerotised cuticle surrounding shield ( Figure 25View FIGURES 21–26). Dorsal shield setae variable in length (especially J series), some s -S setae inserted in the soft skin just outside the dorsal shield in some specimens ( Figures 17, 18View FIGURES 17–20). Shield with 13 pairs of discernible pore-like structures, seven on podonotum (idl, id1, id4, id5, id6, gd2, gd6) and six on opisthonotum (idm1, idm2, idm3, idm4, idm5, idm6).

Ventral idiosoma ( Figures 13View FIGURES 12–16, 19, 20View FIGURES 17–20, 22View FIGURES 21–26, 27View FIGURES 27–32, 33, 34View FIGURES 33–36). Tritosternum with paired pilose laciniae (150–170), columnar base 50–56 long, 36–39 wide; pre-sternal area weakly reticulated. Sternal shield longer than wide, length 221–225, narrowest between st1–st2 (140–145) and broadest at level of st3 (158–168), with straight anterior margin and irregular posterior margin, surface without distinct ornamentation, with variation in the size of the sclerotised area ( Figures 19 and 20View FIGURES 17–20). Sternal setae long and smooth, st1 (138–144) off the shield, one pair of lyrifissures on anterior margin of sternal shield and a pair of circular pores between st2 (138–146) and st3 (138–151). Metasternal platelets absent, metasternal setae st4 (138–166) and metasternal poroids located in weakly sclerotised cuticle. Endopodal plates I/II completely fused to sternal shield, endopodal plates II/III triangular, fused to sternal shield to varying degree in different specimens, sometimes free, endopodal plates III/IV not visible.

Genital shield long and tongue-shaped, length 300–370, maximum width 106–115, posterior edge rounded, surface with a few longitudinal lines, genital setae st5 (124–138) on edge of the shield, their position varying in different specimens. Circular paragenital poroids located on weakly sclerotised cuticle close to st5. Anal shield triangular (161–172 × 120–122), surface without distinct ornamentation, para-anal setae (111–114) at least double length of unpaired post-anal seta (50–55), cribrum large, anal pores indistinct. Opisthogaster with one pair very small oval metapodal plates, strongly hypertrichous, one pair of caudal setae greatly elongated and wavy (300–492). Peritrematal shield fused anteriorly with dorsal shield, free posteriorly, peritremes extending from coxa IV to posterior margin of coxa I, peritrematal shield broadly enlarged around stigmatic opening ( Figure 27View FIGURES 27–32), post-stigmatic section not conspicuous, with two pairs of pore-like structures one lyrifissure ‘ ip’, and one gland pore ‘ gp’ ( Figure 27View FIGURES 27–32).

Gnathosoma  . Epistome irregularly denticulate laterally, apical section smooth, with minute denticles in some specimens ( Figures 15View FIGURES 12–16, 35View FIGURES 33–36). Hypostomal groove with six rows of minute deutosternal denticles, 12–20 denticles per row, and smooth anterior and posterior transverse lines. Hypostome with four pairs of setae, internal posterior hypostomal setae h3 longest (121–126), h1 (61–68), h2 (50–58), palpcoxal pc (60–69) ( Figures 14View FIGURES 12–16, 28View FIGURES 27–32, 36View FIGURES 33–36). Corniculi robust and horn-like, reaching mid-level of palp femur. Palp setal numbers: trochanter 2 (vi, v2 long, 107–109), femur 5, genu 6, tibia 14, tarsus 15, all setae smooth and pointed, palp tarsal claw two-tined ( Figures 28, 29View FIGURES 27–32, 36View FIGURES 33–36). Internal malae complex, with two pairs of lobes, inner lobes narrow, with serrated edges, outer lobes narrow, pointed, shorter than inner lobes, with serrated edges ( Figure 14View FIGURES 12–16). Fixed digit of chelicera with a large backwardly-directed distal tooth followed by three smaller teeth and a row of 10–15 minute teeth ( Figures 16View FIGURES 12–16, 30View FIGURES 27–32), pilus dentilis short and robust, dorsal seta short, semi-erect, movable digit with two large medial teeth, arthrodial membrane a rounded flap with a corona, cheliceral lyrifissure distinct.

Legs. Legs II and III short (732–791, 740–818), I and IV longer (810–902, 991–1070) (excluding pretarsus). Chaetotaxy normal for free-living Laelapidae  . Leg I ( Figure 37View FIGURES 37–38): coxa 0 0/1, 0/1 0, trochanter 1 0/2, 1/1 1, femur 2 3/1, 2/3 2 (macroseta pd1 330–360), genu 2 3/2, 3/1 2 (macroseta pd1 190–210), tibia 2 3/2, 3/1 2. Leg II ( Figure 38View FIGURES 37–38): coxa 0 0/1, 0/1 0, trochanter 1 0/1, 0/2 1, femur 2 3/1, 2/2 1 (macroseta pd1 267–300), genu 2 3/1, 2/1 2 (pd1 longer than other setae on segment), tibia 2 2/1, 2/1 2 (ventral setae all thicker). Leg III ( Figure 39View FIGURES 39–40): coxa 0 0/1, 0/1 0, trochanter 1 1/1, 0/1 1, femur 1 2/1, 1/0 1 (macroseta ad1 388–410), genu 2 2/1, 2/1 1 (macroseta ad1 284–300), tibia 2 1/1, 2/1 1 (ventral setae all thicker). Leg IV ( Figure 40View FIGURES 39–40): coxa 0 0/1, 0/0 0, trochanter 1 1/1, 0/1 1, femur 1 2/1, 1/0 1 (macroseta ad1 533–564), genu 2 2/1, 3/0 1 (macroseta ad1 430–461), tibia 2 2/1, 3/1 2. Tarsi II–IV with 18 setae, 3 3/2, 3/2 3 + mv, md and subterminal blunt spines (al1 and pl1) ( Figures 38View FIGURES 37–38, 39, 40View FIGURES 39–40, 42–44View FIGURES 41–44). On tarsus II all ventral setae thicker, pd2 longer (98–103) ( Figures 38View FIGURES 37–38, 42View FIGURES 41–44). On tarsus III al2 (91–95), ad2 (116–120), pl2 (91–95) and pd2 (120–130) longer ( Figures 39View FIGURES 39–40, 43View FIGURES 41–44). Tarsus IV with four macrosetae, ad2 (178–191), pd2 (220–248) and al2 (125–140) and pl2 (125–140) ( Figures 40View FIGURES 39–40, 444). Pre-tarsi on legs II–IV with a pair of stout claws, each claw with a basal spur ( Figures 31–32View FIGURES 27–32), and a long thin membranous ambulacral stalk ( Figures 38View FIGURES 37–38, 39, 40View FIGURES 39–40, 42–44View FIGURES 41–44). Pre-tarsi I with a pair of simple claws and a long thin membranous ambulacral stalk ( Figure 41View FIGURES 41–44)

Genital structures. Insemination ducts opening on posterior margin of coxa III, sacculus indistinct, apparently unsclerotised.

Male (n = 1)

Dorsal idiosoma. Dorsal shield length 856, width 562; structure and chaetotaxy as for female.

Ventral idiosoma ( Figures 45View FIGURES 45–46, 47–49View FIGURES 47–52). Sternal, genital and endopodal shields fused to form a composite shield with four to five pairs of long setae (one pair of st1 on shield and another one off the shield) and one and two pairs of lyrifissures and pores respectively, genital opening at anterior margin of shield, posterior margin of shield irregular. Ventral sclerotised fragment free and irregular in shape, with 16 setae ( Figures 45View FIGURES 45–46, 48, 49View FIGURES 47–52). Anal shield as in female, with a rounded anterior margin, well separated from ventral shield ( Figures 45View FIGURES 45–46, 47–49View FIGURES 47–52), metapodal plates absent.

Gnathosoma  . Movable digit of chelicera with one large tooth, spermatodactyl longer than movable digit, sharply bent apically, with a small pore-like structure at back of distal bend, with truncate tip, fixed digit with one medium distal tooth and minute pilus dentilis ( Figures 46View FIGURES 45–46, 50View FIGURES 47–52).

Legs. Chaetotaxy as in female, av1 and av2 on tarsus II–III and av1 on tibia II stout, pointed and spine-like ( Figures 51, 52View FIGURES 47–52).

Type material. Holotype, female, Cuba, north of Matanzas Province, on Strategus sarpedon (Burmeister) ( Coleoptera  : Scarabaeidae  )  . Paratypes: 18 females and one male, same data as holotype  .

Additional material: One female, Brazil, MT, Chapada dos Guimarães, Cerrado, 15°16’ S 56°00’ W, 7 December 2015, A. Frolov & L. Akhmetova coll., under elytra of Strategus surinamensis hirtus Sternberg ( Coleoptera  : Scarabaeidae  ) (in TUMZ) and the host beetle is housed in the collections of Zoological Institute of Russian Academy of Sciences, Saint Petersburg, Russia (ZIN).

Type deposition. The holotype and 15 paratypes are deposited at the acarological collection of the Tyumen State University Museum of Zoology , Tyumen, Russia (TUMZ)  and three paratypes are deposited at the Departamento de Biología Animal y Humana , Facultad de Biología, Universidad de La Habana, Cuba  .

Etymology. The name of this species refers to its occurrence on beetles of the genus Strategus.

Remarks. The area of sclerotised cuticle between the sternogenital shield and anal shield in the male of Acantholaelaps strategus  is very unusual. In the single available specimen this sclerite is irregular in shape, has the same surface texture as the sternogenital shield, and is not covered by striated soft skin. It may be a fragment of a reduced sternogenital/ventral shield, but confirmation must await the collection of more males.

Female specimens of the new species show a remarkable range of variation in body size, length of medial dorsal shield setae, range of sclerotisation of the sternal shield, and the number of dorsal shield setae, but we believe that these differences represent intra-species variation. Costa & Hunter (1971) observed variation of this type in the related genus Coleolaelaps  , and speculated that the variation might represent differences between clonal strains in species that appear to be thelytokous. Our collection of A. strategus  includes 20 females and one male. These numbers suggest, but do not confirm, that this species reproduces by arrhenotokous parthenogenesis. The evolutionary significance of this intra-species variation would reward further study.

The geographic distributions of species of Acantholaelaps  and the other genera in Table 1 are probably influenced by the distribution of their specific hosts, depending on the degree of host specificity. The feeding habits of these mites are unknown, but they may be predators that feed on other small invertebrates in the microhabitats created by the beetles such as the hypopus stage of Astigmata mites.

The presence of the new genus in Cuba supports the need for further exploration in this area. Acantholaelaps  is apparently not endemic to Cuba, because a specimen has been collected in Brazil, but its distribution in surrounding countries remains unknown. The host beetle genus Strategus is widespread in the Neotropical Region and includes at least 31 species ( Ratcliffe, 1976). It is not yet known how many of these species carry specimens of Acantholaelaps  .