Serrated mite (Myrmozercon serratus) and spatulate mite (Myrmozercon spatulatus) from Mexico with ant hosts

NEWS - Serrated mite (Myrmozercon serratus sp. nov. Kazemi, Klompen, Pérez-Lachaud & Lachaud) and spatulate mite (Myrmozercon spatulatus sp. nov. Kazemi, Klompen, Pérez-Lachaud & Lachaud) are reported based on adult and deutonymph specimens collected with ants in Mexico as the first records of this genus from the Neotropical faunal region.

Myrmozercon Berlese 1902 is one of the most morphologically diverse genera, including 28 extant species and one extinct species. Almost all species have been collected with ants. Now researchers describe two new species associated with two sympatric formicine ant species of the genus Camponotus Mayr in Quintana Roo, southern Mexico.

M. serratus has a dorsal shield with 30–34 pairs of slightly thickened and apically blunt setae, opisthonotal setae mostly with small denticles in the distal 1/3; a wide sclerotized band of marginal striations flanking the shield dorsolaterally in female, not fused, or narrowly fused medially; band bearing 6–10 pairs of setae.

Female sternal shield wide, subrectangular, narrowly fused to endopodal plates between coxae III–IV laterally. Sternal setae short; setae st4 present. Male sternitogenital shield with 6–7 pairs of setae (one ventral seta may be present or absent), st1 on lightly sclerotized area.

Epigynal shield longer than wide (length/width ratio ≈ 1.8). Anal shield with moderately enlarged anterolateral projections; circum-anal setae thickened, blunt. With 23–30 pairs of setae on dorsal soft cuticle and about 20 pairs of setae on ventral soft cuticle.

Metapodal shields absent in female, present in male. Deutosternal groove with 15–16 rows of 6–25 minute denticles. Palp chaetotaxy from trochanter to genu: 1-5-6; tibia and tarsus palps fused dorsally. Cheliceral digits poorly sclerotized, edentate.

Female legs trochanters I–IV with 6, 5, 5, 5, femora I–IV with 14, 11, 6, 5–7 setae, genua I–IV with 13, 11, 11, 11, and tibiae I–IV with 13, 10, 10, 10 setae, respectively; basitarsus IV with 4 or 5 setae. Male with similar leg setation, but trochanter IV with 6–7 setae; setae al2 on genu and tibia I present or absent.

By a combination of characters, including long legs with hypertrichous setae, a reticulate dorsal shield, and a subrectangular sternal shield, M. serratus is a member of a species group called Myrmozercon sensu lato Joharchi, Babaeian & Seeman (2015).

Within this group, M. serratus is most similar to M. antennophoroides Berlese 1903, M. hunteri Joharchi, Babaeian & Seeman 2015 and M. patagonicus Trach & Khaustov 2018 with 30–34 pairs of setae on the dorsal shield and a subrectangular sternal shield.

Differs from M. antennophoroides by the presence of only one pair of setae on the epigynal shield (vs. two pairs in M. antennophoroides), leg I is much longer than the dorsal shield, length ratio ≈ 1.7 (vs. leg I is shorter, length ratio of leg I/dorsal shield ≈ 1.37), and the gnathotectum is subtriangular, but not elongated (vs. subtriangular and elongated).

The new species can be distinguished from M. hunteri by the presence of 6 setae on trochanter I and 13 setae on tibiae I (vs. 5 and 10 setae respectively in M. hunteri), the presence of simple setae with pointed tips on the legs (vs. most setae on legs with club-like tips) and the presence of a broad sclerotized band of marginal lines surrounding the dorsal shield (vs. absent).

M. patagonicus can be distinguished from M. serratus by the presence of 19–21 rows of denticles in the deuterosternal groove (vs. 15–16 rows in M. serratus), the presence of metapodal platelets (vs. none), 4 setae on the femoral palps (vs. 5), and also 14 setae on genua I, 7–8 setae on femora III and 8 setae on femora IV (vs. 13, 6, and 6 setae, respectively).

M. spatulatus has a dorsal shield with 27–31 pairs of slightly thickened and apically spatulate setae; wide sclerotized band of marginal striations well-developed in female (less developed in male), surrounding the shield laterally and broadly fused posteromedially; band bearing 10–12 pairs of setae.

Female sternal shield wide, moderately narrow; with relatively long sternal setae, st2–3 as long as the distance between their insertions, st1 slightly shorter than st1–2 interval. Female sternal shield adjacent to, but not fused to, endopodals between coxae III–IV. St4 setae absent.

Male sternitogenital and deutonymphal sternal shield bear five and four pairs of setae, respectively. Epigynal shield large and wide, almost as long as wide (length/width ratio ≈ 0.9). Anal shield wide, anterolateral edges well-developed, circum-anal setae thickened, apically spatulate. With 7–10 pairs of setae on dorsal and 14–16 pairs of setae on ventral soft cuticle. Metapodal shields present.

Deutosternal groove with 18–19 rows in female and deutonymph, and 15 rows in male, each row with multiple denticles; palp chaetotaxy from trochanter to genu: 1-4-5. Cheliceral digits poorly sclerotized, edentate; spermatodactyl sickle-shaped.

Female femora I–IV with 13, 10, 6–7, 8–9 setae, genua I–IV with 13, 11, 11, 11, and tibiae I–IV with 13, 10, 10, 10 setae, respectively. Leg setae, especially dorsal setae on trochanter to tibia, apically spatulate.

M. spatulatus is included in Myrmozercon sensu lato mainly on the basis of the long legs with hypertrichous setae and the reticulate dorsal shield. In this group of species, the absence of metasternal setae is similar to M. iainkayi Walter 2003 and M. beardae Shaw & Seeman 2009).

M. iainkayi can be distinguished by several characters, for example, the presence of a hypertrichous dorsal shield with simple and short setae (vs. 27–31 pairs of fairly long and spatulate setae in M. spatulatus), coxae I–IV with 6, 6, 6, and 4 setae respectively (vs. the standard coxal set of setae) and a horseshoe-shaped sternal shield (vs. only slightly concave posteriorly).

M. beardae differs from M. spatulatus by differences in the shape of the sternal, epigynal and anal shields, in addition to characters such as the shape and number of setae on the dorsal shield. M. beardae has 23–25 pairs of short and simple setae (vs. 27–31 pairs of long and spatulate setae in M. spatulatus) and a difference in the setation on coxa IV, M. beardae has 2 setae (vs. 1).

The species epithet “serratus” was chosen on the basis of the shape of most setae in the opisthonotal region of the dorsal shield. “Spatulatus” was chosen on the basis of the shape of most dorsal and opisthogastral setae.

Original research

Pérez-Lachaud G, Klompen H, Kazemi S, Lachaud J. 2024. Myrmozercon mites are highly host specific: two new species of Myrmozercon Berlese associated with sympatric Camponotus ants in southern Quintana Roo, Mexico. PeerJ 12:e18197, DOI:10.7717/peerj.18197

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