Heatherellidae Walter, 1997

Seeman, Owen D., Minor, Maria, Baker, Michelle R. & Walter, David Evans, 2018, A revision of the Heatherellidae (Parasitiformes: Mesostigmata) with a new genus and two new species from Australasia, Zootaxa 4434 (3), pp. 441-465 : 442-443

Heatherellidae Walter, 1997

Heatherellidae walter, 1997 : 168.

Type genus— Heatherella walter, 1997 .

Diagnosis: Gamasine Mesostigmata . Adults covered in a thick cerotegument; oval idiosoma ringed with bifurcate marginal (r -R) setae (up to 28 pairs) and gland-bearing protuberances (up to ten pairs), each with or without emergent, spout-like lip. Protuberances and s -S series setae on upper margin of extensive opisthogastricperitrematal-marginal shield; this shield with numerous spicules and/or microtubercles; dorsum with most of the usual setae for Mesostigmata except setae s3 absent, setae z2 present or absent, r -R series hypertrichous; setae j1 and z1 ventral; dorsal shields sometimes sexually dimorphic but always with series of pre-pygidial platelets and pygidial shield bearing setae J5 flanked by small lateral shields bearing setae Z4. Anal region raised, with five circumanal setae. Gnathosoma ventral, between first pair of legs, and protected dorsally by idiosoma. Chelicerae slender, elongate, with short digits, setiform pilus dentilis, without excrescences; cheliceral seta elongate, inserted laterally on fixed digit. Palpal setation, trochanter, femur, genu, tibia, respectively: 2–5–6–14. Leg I slender, antenniform, without apotele; leg setation: coxae I–IV, respectively: 2–2–2–1; trochanters 6–5–5–5; femora 13– 11–7–6; genua: 13–11–10–10, formulas: 2 3/2, 3/1 2; 2 3/1, 2/1 2; 2 2/1, 2/1 2; 2 2/1, 3/1 1; tibiae 12/13 (± av2)- 10 9 10; formulas: 2 3/2, 3/1 2; 2 2/1, 2/1 2; 2 1/1, 2/1 2; 2 2/1, 2/1 2. Female with dorsal shield undivided, fused with or free from submarginal and marginal shields anteriorly, bearing nine pairs of setae (j3–j6, J1–J4, z5); lateral submarginal shields with four pairs of setae (z6, Z1–3); setae s2–s6, S1–S5 and Z5 on marginal shield; sternal shield subdivided, st1 on jugularia or in soft cuticle; st2 on single plate; st3–4 on 1–2 pairs of platelets; a single subtriangular genital shield with one pair of setae. Male genital opening intercoxal, covered by pair of sclerites; st1 on jugularia or in soft cuticle; chelicera without spermatodactyl; femur II and sometimes genu II with seta av1 a blunt spur.

Comments. The setation of the legs and palps is mostly consistent throughout the family including the new taxa described below. The only variable seta is av2 on femur I, which is absent in the new genus. However, Walter (1997) missed a small dorsal seta on trochanter III: the correct setation for trochanters I-IV, respectively, is 6–5–5– 5, not 6–5–4–5.

The spout-like gland openings are characteristic of the Heatherellidae , but the number of well-developed protuberances varies interspecifically (7–10 spout-like protuberances; Table 1). The pores associated with setae s6 are sometimes indistinguishable from other large idiosomal pores ( Fig. 15 ); those associated with setae s4 are sometimes enlarged pores and raised only slightly ( Fig. 25 ); while those associated with setae s5 often appear as a raised pustule ( Figs 34–35 ). This latter form appears similar to that found in the Epicriidae . Alberti (2013) explored the fine structure of the single pair of idiosomatic protuberances in Epicrius mollis ( Kramer, 1876) and pointed out the glandular nature of the pair he refers to as the pustule. Although they appear very similar in Heatherellidae and Epicriidae , the pustules of E. mollis may not be homologous with those in the Heatherellidae because they are unlikely to be derived from the same pore. The pustule of Epicriidae lies behind seta s6 ( Moraza 2005; Alberti 2013) but in the Heatherellidae , the pustule-like structure is anterior to seta s6, and closely associated with seta s5 ( Figs 34–35 ).

The classification of the Heatherellidae is problematic. Walter (1997) reasoned that the family belonged in the suborder Monogynaspida, and of its cohorts, regarded the family most closely related to the Epicriina, Microgyniina or Zerconina, but no synapomorphy could place the Heatherellidae in any of these cohorts. Lindquist et al. (2009a) essentially followed Walter (1997) by classifying the Heatherellidae in its own monogynaspid cohort, the Heatherellina , but Lindquist et al. (2009b) suggested a close relationship with the Epicrioidea.

In regards to the Epicrioidea, and in contrast to the state of classification in 1997, Lindquist et al. (2009a) treated the Epicriina and Zerconina as superfamilies of the Epicriiae, a subcohort of the cohort Gamasina . This classification is supported by molecular evidence, which placed the Epicriiae as the first branch within the Gamasina ( Klompen et al. 2007). This molecular evidence also excluded the Microgyniina and Uropodina from the Gamasina . Thus, if the Heatherellidae share a sister-relationship with the Epicrioidea, then under the classification of Klompen et al. (2007) and Lindquist et al. (2009b), the Heatherellidae are gamasine mites within the Epicriiae.

Evidence for a Heatherellidae-Epicriidae sister relationship was provided by Lindquist et al. (2009b), who noted the possible synapomorphies of a thick cerotegument ( Figs 30–31 ), hypertrophied cheliceral seta, fragmented sternal shields and loss of the peritreme. Our new genus has a short but well-developed peritreme, thus eliminating this synapomorphy, although we note that the Epicriiae show considerable variation in peritreme development. Usually, nymphs have well-developed peritremes that are reduced, sometimes entirely, in adults ( Solomon 1978; Lindquist & Moraza 1998; Moraza & Lindquist 1998). Heatherellidae also show this ontogenetic reduction. Deutonymphs of the new genus have long peritremes, which are greatly reduced in the adult, and some poorly preserved deutonymphs of H. acanthocharis and H. callimaulos have short but distinct peritremes; these are obsolete in the adult stage.

Further putative synapomorphies with the Epicriidae are the laterally placed cheliceral seta, leg I without apotele and, usually in Epicriidae , a large, idiosomal pustule near seta s5 (see Alberti 2013). The dorsal setation is also similar to some Zerconidae , with a trend towards the marginal placement of the z -Z series (except z5) close to the s -S series, and hypertrichy in the r -R series. In three Heatherellidae species this hypertrichy is similar to some Zerconidae in that the r -R setae are duplicated (i.e. there are 22 pairs). Therefore, we propose that the Heatherellidae should be considered as a superfamily of the subcohort Epicriiae, and represent the only known southern hemisphere representatives of this subcohort.

Figures

FIGURE 15. Heatherella callimaulos walter, 1997, female holotype, dorsum. First pair of tubercles are somewhat concealed. The only marginal seta shown is r1. Two types of pores: 12 pairs large (shaded grey) and ten pairs of smaller pores (unshaded). Platelets behind main dorsal shield not obvious (dotted lines).

FIGURE 25. Aheatherella mira n. sp. male, dorsum.

FIGURES 34–37. (34) Heatherella acanthocharis walter, 1997, dorsomarginal protuberances, pustules and pores of paratype female (P-s5 pustule; P-s6 pore; P-S1 protuberance), dorsal view of flattened specimen, right side; (35) Aheatherella mira n. sp., dorsomarginal protuberances, pustules and pores of paratype female (P-s5 pustule; P-s6 protuberance with closely associated seta), dorsal view of ventrolateral fragment with broken r-setae, left side; (36) Heatherella osleri n. sp., peritreme of paratype female (ventral view, right peritreme of mite); (37) Aheatherella mira n. sp. peritreme of paratype female (ventral view, left peritreme of mite; sclerotised eXopodal portion of eXopodal-peritrematal shield shaded).

FIGURES 30–31. Heatherella acanthocharis walter, 1997, scanning electron micrographs. (30) idiosoma, showing sloughed certotegument, scale bar = 100 µm; (31) podonotum, with mostly intact cerotegument (fractured behind setae j3 and laterad z3).