Rhodacarella cavernicola, Moraza, Maria Lourdes, 2004

Moraza, Maria Lourdes, 2004, Rhodacarella, a new genus of Rhodacaridae mites from North America (Acari: Mesostigmata: Rhodacaridae), Zootaxa 470, pp. 1-10 : 4-8

Rhodacarella cavernicola sp.nov. ( Figs. 1–9 )

Diagnosis. Dorsal setae of idiosoma of moderate length and simple; podonotal and opistonotal chaetotaxy holotrichous (45 pairs of setae). Dorsal shields barely sclerotized, reduced and without ornamentation. Presternal shields present, nine pairs of ventral setae, Jv2 on the ventrianal shield.

Measurements. Idiosomal length 486 m; idiosomal width at level of seta s4 including soft marginal cuticle 188 m; podonotal shield length 207 m, width 158 at level of seta s3; opisthonotal shield length 219 m, width at level of setae Z3, 86 (2 specimens)

Description ( Figures 1–9 ). Adult female (holotype).

Gnathosoma: Tectum ( Figure 3 ) with a medial smooth pointed projection. Fixed digit of chelicera with well­developed pilus dentilis proximal to three subdistal teeth smaller than other four basal teeth; movable chela with two well­spaced teeth, the proximal smaller than basal; cheliceral seta and lyrifissures normal ( Fig. 5 ). Corniculi long and parallel; internal malae with lateral margin piloses, with long and acute apex extending slightly beyond tips of corniculi. Salivary styli as in Figure 4 . Deutosternal groove of subcapitulum ( Fig. 4 ) with smooth anterior margin discernible between bases of hp2 and with seven rows of denticles. Posterior pair of subcapitular setae similar to the other subcapitular setae; anterior pair of setae nearly twice as long as other pairs. Palpal chaetotaxy as described for the family; palgenu with seta al ­1 smooth, stouter than other genual setae and spatulate.

Idiosoma dorsum ( Figure1 ): Podonotum with 22 pairs of simple setae, including 16 pairs (j1–j6, z1–z6, s3–s6) on subpentagonal non­ornate podonotal shield, and six pairs (s1, s2, r2–r5) in soft marginal cuticle; j1, j2 and z1 on the anterior border of the shield; j1 43 m and j2, z1 half its length; other setae of similar moderate length; z6, s3, s4 and s6 on the border of the shield. Opisthonotum covered by a narrow opisthonotal shield with 15 pairs of simple setae (J1–J5, Z1–Z5, S1–S5) plus eight pairs of setae in the marginal soft cuticle (R1–R6, UR1, UR2); J5 short (half the length of J4); Z4 and Z5 are the longest setae. Dorsal and lateral idiosomal pore­like structures positioned as in Fig. 1 and include: on the podonotal shield idj3, idj6, idz1, ids4 and ids5; on the opisthonotal shield, idz6, ids6, idJ1­ idJ5, gidZ3, idS1, two idS3, idS4 gdS4, gdS5 and on the soft opisthonotal cuticle, idR3 and ivp.

Idiosomal venter ( Figure 2 ): Tritosternum with elongated base and paired barbed laciniae, which are free from each other along entire length. In front of tritosternum, there is a pair of smooth, well­sclerotized pre­endopodal shields. Presternal region with paired narrow punctate shields separated from the sternum by punctuated cuticle. Sternal shield weakly sclerotized, with almost straight anterior margin, punctate between anterior margin and st2 setae. Length of shield at medial region level, 91 m, width at level between coxa II and III, 113 m; st1 on the soft granulated cuticle; shield with three pairs of simple setae and three pairs of lyrifissures (iv1 on the anterior border, iv2 and iv3 on the posterior margin of the shield); posterior margin, convex at level of coxa III. Endopodal sclerite between coxae I and II well developed and free from the sternal shield. Genital shield long, length 128 m, width 49 m, with straight and punctuated posterior margin and a tongue­like epigynal margin overlapping posterior margin of sternal shield; genital setae on or off the shield and iv 5 in the soft, striated marginal cuticle, posterior to the genital setae. Peritreme length including the stigmata 84 m and with a very abbreviated peritrematal plate which bears one lyrifissure and one gland on the antiaxial margin. Two pairs of conspicuous metapodal platelets, anterior pair rounded, other small, ventral sclerites present. Opisthogaster with nine pairs of simple ventral setae, including one pair (Jv2) on the margin of the long and narrow ventrianal shield and eight pairs (Jv1, Jv3–Jv5, Zv1– Zv4) in the soft cuticle; Zv 1 in front of Jv1, Zv3 shorter (half other opisthogastric setae). Circumanal setae slightly pilose, paranal setae (length 34 m) in front of anal opening and postanal twice their length (69 m). Ventral pore­like structures positioned as in Fig. 2 , include ivo1, iv2 and posterior ivp.

Legs ( Figures 6–9 ). Excluding tarsus, length of leg I 331 m ( Fig. 6 ), leg II 251 m ( Fig.7 ), leg III 201 m ( Fig. 8 ) and leg IV 399 m ( Fig. 9 ). Coxa I and II with distal serrate margin behind condyle; coxae III and IV with distal margin smooth; coxa IV without second seta “ av ”. Pretarsi of legs I–IV with well­developed claws. Setation of trochanters of legs, respectively, 5­5­5­5; that of femora, 12­11­6­6; that of genua, 2 3/2 3/1 2 (13), 2 3/1 2/1 1 (10), 1 2/0 2/1 2 (8), 2 2/1 3/0 1 (9); that of tibia, 2 3/1 3/2 1 (12), 2 2/1 2/1 2 (10), 1­ 2/1 1/1 2 (8) – 2 2/1 2/1 1 (9). Genua II with av1 spine­like, enlarged seta.; femora IV with two spine­like setae; genua IV with one ventral setae and one short and thin pl; the two ventral setae of tibia IV are stout and tibia IV with one pl seta short and thin. Basitarsus II–IV with four setae.

Etymology. The species epithet “ cavernicola ”, is a reference to its habitat.

Material studied. Holotype adult female (mounted, permanent slide), 19 May 1990, W.C. Welbourn leg., ex bat guano ·15. Paratype, one adult female, with data same as for holotype.

Type­locality. U.S.A., Arizona, Cochise County, Kartchner Caverns State Park. Material deposited. Florida State Collection of Arthropods, Division of Plant Industry, Grainesville.

Discussion. In addition to the five genera mentioned earlier, other genera of Rhodacaridae have been described and, although their systematic position has been incertaesedis, their inclusion in the subfamily is now considered. Mediorhodacarus Shcherbak, 1976 ( M. tetranodulosus ) may be placed in the genus Rhodacarus based on its dorsal and ventral chaetotaxy and because of the presence of presternal shields in some species of Rhodacarus , such as in Rh. berrisforci . Similarly, Minirhodacarellus Shcherbak, 1980 (type species Rhodacarellus minimus Krag, 1961 ) should remain in the genus Rhodacarellus as the presence of the transverse suture is not a constant characteristic within the same genus, as found in Rhodacarus .

Afrogamasellus Loots & Ryke, 1968 and Afrocarellus Hurlbutt, 1974 from Africa ( Loots & Ryke, 1968) display characteristics of Rhodacaridae . Both genera have three pairs of dorsal setae on the anterior margin of the podonotal shield (j1, j2 and z1) and four arcuate scleronoduli as in Rhodacarellus . The presternal region has punctate sclerotization as in Afrogamasellus mongii and Afrocarellus lupangaensis , or well developed presternal jugular shields as in Afrogamasellus lyamunguensis . Basitarsus IV has three setae and the tectum has either a medial projection smooth or with apex dentate ( Afrogamasellus ), or three medial serrate branches (Afrocarellus). However, the arthrodial process at the base of the cheliceral digit in both genera is a brush (such as in Pararhodacarus ), the shielding is more extensive and, except for one seta in the female, six ventral setae are included in the ventrianal shield. Lateral podonotal shields and a transverse suture are absent; 23 pairs of podonotal setae (all setae or 22 on the shield); 20 pairs of opisthonotal shield setae and seven pairs of ventral setae, of which six are on the ventrianal shield.

The weakly sclerotized new genus shares with Rhodacarellus the presence of three pairs of setae on the anterior margin of the podonotal shield, hyp3 seta level with hyp2 and similar cheliceral structure of the female. However, Rhodacarellus has more reduced dorsal and ventral chaetotaxy, with only 19 pairs of opistonotal setae (four R setae, setae UR are absent) and seven pairs of ventral setae (Zv3 and Zv4 absent).

The presence of presternal scutella is another characteristic that distinguishes Rhodacarella nov. from Rhodacarus and Rhodacarellus , both of which have the anterior margin of the sternal shield separated from the rest by punctate sclerotization. Rhodacaropsis has well­developed presternal shields separated from the sternal shield by striated cuticle and has sternal setae st1 on the shield. Other genera of this family lack normal pre­endopodal shields and the endopodals between legs I and II are minute.

Krantz and Ainscough (1990) indicate the presence of 10 setae on genua and tibia IV (2 2/1 3/1 1) for the family Rhodacaridae and Krantz (1978) indicates tibia I with 13–14 setae (five or six dorsal and one or two pv setae 2 3/2 2(3)/1 2 or 2 3/2 3/2 2), genu IV 1 1/ 1 2/1 1 or 2 1/1 2/1 1) and tibia III 1 1/1 2/1 1 or 2 1/1 2/1 1. However, Rhodacarella nov. shows characteristics not found in the other genera included in the family such as 12 setae on tibia I (2 3/1 3/2 1) and nine setae on genu IV (2 2/1 3/0 1) and tibia IV (2 2/1 2/1 1). The reduced ventrianal shield with only one pair of ventral setae and scleronoduli absent may well represent characteristic feature of the genus.

Dorsal shielding and chaetotaxy resembles that of Protogamasellus (family Ascidae ) except for the absence of the transverse line across surface at level of setae z6 and J1. We have to remember that Protogamasellus has been considered a rhodacarid mite by several authors (genus Rhodacaropsis for Athias­Henriot, 1961; Bregetova & Shcherbak, 1977). The inclusion of this new genus in the Rhodacaridae is well established base on the following strong character states: 3­tined palp claw, coxa I with dorsal spine, sternal setae st1 on desclerotised punctate cuticle, and female with setae st4 on sternal shield.

Regarding generic character states, the opisthonotal chaetotaxy in Rhodacarella nov. (with 23 pairs of setae) and the ventral chaetotaxy (with nine pairs of ventral setae) may be considered primitive. The new genus exhibits the derivative characteristic of the absence of setae r6 (present in the other genera of the family), and loss of two setae on tibia I and one seta on genu and tibia IV.

Figures

FIGURES 1 – 2. Rhodacarella cavernicola sp. nov., female. 1. Idiosoma dorsal. 2. Idiosoma ventral.

FIGURES 3 – 9. Rhodacarella cavernicola sp. nov., female. 3. Tectum, 4. Subcapitulum. 5. Chelicera, antiaxial side. 6. Right leg I, dorsal side, 7. Right leg II, dorsal side, 8. Right leg III, dorsal side, 9. Right Leg IV, anterolateral side (dotted circles indicate ventral setae)