Chiasmanyssus cavernicola, Gomes-Almeida & Pepato, 2021

Gomes-Almeida, Brenda K. & Pepato, Almir R., 2021, A new genus and new species of macronyssid mite (Mesostigmata: Gamasina: Macronyssidae) from Brazilian caves including molecular data and key for genera occurring in Brazil, Acarologia 61 (3), pp. 501-526 : 507

Chiasmanyssus cavernicola n. gen. n. sp.

Zoobank: A34F4774-19C6-41E7-AFCB-023910A345A0

Diagnosis — Female: Elongated dorsal shield, holotrichous, bearing 27 pairs of setae, all setae long and subequal, except j2, z2, s1–s2 small (and J5 minute). Unarmed dorsum with approximately 84 pairs of long setae and ventral opisthosoma with approximately 48 pairs of setae; peritrema long, extending from level of anterior margin of coxae II to the middle of coxae IV; palpal trochanter with a small blade-like ventral process. Male: anterior margin of the dorsal shield not discernible from the soft cuticle; with neotrichous condition on opisthonotal region; a pair of additional minute setae, laterally to J4 and J5, on neotrichous area of opisthonotal region. Four pairs of caudal setae on unarmed dorsum and four pairs of setae on unarmed venter. Protonymph: Subrectangular podonotal shield with lateral borders biconcave at level of z2 and z4, posterior region almost square; with j2 very close to j1. Trapezoidal pygidial shield with J4 and Z4 small than others (except J5 minute). Unarmed dorsum with 12 pairs of long setae. Unarmed venter with four pairs of median setae between ventral shields and a pair of caudal setae, without setae flanking the anus.

Description. Female — Measurements summarized in table 4.

( Figures 2–4 )

Idiosoma — ( Figures 2A–B ). Oval, moderately sclerotized and striated integument; all setae smooth. Dorsum ( Figure 2A ). Dorsal shield entire, elongated, longer than wide, and narrow, even at its widest, distinctly tapered in the middle of opisthonotal region; reticulated sculpture on all its area; holotrichous condition with 27 pairs of setae, 16 on podonotum and 11 on opisthonotum; j and J series complete with j1, j2 and j3 on dorsal shield; all setae long and subequal except j2, z2, s1–s2 small and J5 as microsetae ( Figure 3A ); one pair of lyrifissures near on margin lateral to setae j1 and four pair of pores on margin lateral to setae j3 and J4 and near s4 and z6. Unarmed dorsum with approximately 84 pairs of long setae. Venter ( Figure 2B ). Tritosternal base not expanded; Tritosternum bipartite with long and fimbriate laciniae ( Figure 3B ). Presternal area is weakly sculptured. Sternal shield nearly square, anterior margin with a small medial prominence; strongly sclerotized and punctate, except for a smoother X-shaped portion on central sternal shield ( Figure 3C ); anterior and posterior corners absent; three pairs of sternal setae relatively long, st1 and st2 on the sclerotized part and st3 inserted on X-shaped region on shield; two pairs of sternal pores. Metasternal setae (st4) on unarmed integument with third pair of pores accompanying metasternal setae. Epigynal shield expanded anteriorly, median projection extends under the sternal shield, no anterior scale-like markings; posterior margin pointed ( Figure 3C ); one pair of genital setae, approximately at the middle of epigynial plate. Anal plate pyriform; long and narrow cribrum; one pair of adanal setae (pan) and one postanal seta (pon) ( Figure 3D ). Endopodal plates small and triangular between level of coxae

II and III. Opisthosoma with approximately 48 pairs of setae ventrally, slender, except caudal setae, being thicker, similar to the setae on unarmed dorsum. Peritreme long, extending from anterior margin of coxae II to the middle of coxae IV ( Figure 2B ). Peritrematic shield free from dorsal shield but interrupted by two “nodules” on the anterior dorsum between coxae I and II and in the middle ventral between coxae II and III ( Figure 2A–B ). Peritrematic shield posterior to the stigma fused with the parapodal shield around the posterior margin of coxa IV ( Figure 2B ).

Figures

Figure 2 Chiasmanyssus cavernicolan. sp. female. A – Idiosomatic dorsum; B – Idiosomatic ventral. Scale Bars: A & B 20 µm.

Figure 3 Chiasmanyssus cavernicolan. sp. female. A – Dorsal shield; B – Tritosternum; C – Sternal shield, note the distinct X-shaped sclerotization and epigynal shield; D – Anal shield. Scale bars: A 20 µm; B, C & D 50 µm.

Figure 4 Chiasmanyssus cavernicolan. sp. female. A – Gnathosomatic dorsal; B – Gnathosomatic ventral; C – Venter palpal genu with distinct circular (spatulate) and membranous seta; D – Dorsal palpal genu with lyrifissure; E – Palpal trochanter with ventral process; F – Chelicera. Scale bars: 50 µm.