Riccardoella (Proriccardoella) tokyoensis Waki & Shimano, 2018

Waki, Tsukasa & Shimano, Satoshi, 2018, A new species of the genus Riccardoella (Acari: Prostigmata: Ereynetidae) from the land snail Tauphaedusa tau (Gastropoda: Clausliidae) in Japan, Zootaxa 4402 (1), pp. 163-174 : 165-170

Riccardoella (Proriccardoella) tokyoensis Waki & Shimano n. sp.

Japanese name: Wasurena-katatsumuri-dani ( Figs. 2–8 )

Diagnosis. Body size (length × width) in 6 females and 6 males (holotype and 5 paratypes): 293–318 × 150–171 and 286–312 × 153–168, respectively. Color pale yellowish-white. Surface of idiosoma, gnathosoma, and leg with striated cuticle. Eyespot absent. Idiosoma ovate, with 2 anterior sensilli (sci) and 2 posterior sensilli (f 2). All legs cylindrical. Length of tarsi and tibiae I–IV a bit longer than wide. One subcylindrical solenidion (ω) present on each tarsi I and II, inserted in almost dorsal position, close to seta ft ’’. Length of solenidia 4–7. Tibiae I with forked famulus being 63–80% as long as its guard seta. Trochanter I without seta. Femur I and tibia II with 5 and 2 setae, respectively. Tibia I with 4 setae.

Description. Body (idiosoma and gnathosoma). Length, excluding legs, in 6 females and 6 males (holotype and 5 paratypes): 293–318 (mean 309) and 286–312 (mean 295), respectively.

Integuments. Color pale yellowish-white (under a stereomicroscope). Surface of idiosoma, gnathosoma, and legs with striated cuticle.

Idiosoma (males and females) ( Figs. 2A–B , 6A–B , 7A–C ). Idiosoma oval. Idiosoma length 242–281 (mean 267) and width 150–171 (mean 162). One pair of lyrifissures (im) present between e 1 and f 2 ( Fig. 2 ). Lengths of dorsal idiosomal setae: vi 11–14, ve 2–4. sci 39–49, sce 10–14, c 1 6–11, c 2 10–13, d 1 8–11, e 1 8–11, f 1 9–12, f 2 36– 42, h 1 7–11, h 2 9–11. Lengths of ventral idiosomal setae 1a, 3a and 4a 3–5. Dorsal setae, except f 2 and sci, subcylindrical ( Fig. 6A ). Setae f 2 and sci long and narrow ( Fig. 6B ). Variation of setae: one male paratype (21306A) with additional c 1 setae ( Fig. 7A ) and another male paratype (21306D) with coupled 4a setae from one base ( Figs. 2B , 7B ). Striae between setae d 1 and e 1 mainly w-shaped, in two of type specimens (21306E and TW- 4 in NMNS) v-shaped ( Figs. 8A–B ).

Aggenital region of male ( Figs. 2B , 3B ). Two pairs of genital papillae. Genital area with external row of 5 aggenital setae ag and internal row of 5 genital setae g, all of them located generally. Lengths of aggenital and genital setae 3–5. Numbers of aggenital setae ag 3–5 due to variation or defluxion ( Figs. 2B , 3B ). Two pairs of pseudanal setae (ps) located basally. Lengths of setae ps 1 and ps 2 4–7 and 3–5, respectively. Variation and missing of those setae observed in 3 of 6 type specimens. Variation of pseudanal setae: one paratype (21306D) with right seta ps 2 as close to right ps 1 as the 1/2 length of ps 1 ( Fig. 2B ). Genital vestibule with 3 pairs of eugenital setae (eug). Length of setae eug 1, eug 2 and eug 3 4, 6, 4, respectively. One pair of lyrifissures (ih) close to h 2 ( Fig. 2B ).

Aggenital region of female ( Figs. 3A , 7C ). Numbers and position of setae generally identical to those of male. Numbers of genital (g) and ps 1 setae 4–5 and 0–1, respectively, due to variation or defluxion. Variation and defluxion of those setae were observed in 2 of 6 specimens in type series. Females containing eggs were not detected.

Gnathosoma (males and females) ( Figs. 2B , 4A–B ). Length 44–49 and width 30–41 (means 46 and 36, respectively). Eyespot absent. All setae not prolonged by a filament. Length of ventral setae sbc 1 and sbc 2 2–4 (mean 3) and 2–3 (mean 3), respectively. Palptarsus with 3 barbed setae (l’, l” and d), 4 long, situated in apical half of tarsus, and with 1 solenidion (3–4). Two setae on antiaxial surface of palptarsus dilated apically and one seta on paraxial surface cylindrical ( Fig. 4B ).

Legs (males and females) ( Figs 2B , 5A–D , 6C–E ). All legs cylindrical. Tarsi and tibiae I–IV a bit longer than width. Pretarsus with two claws and empodium. All legs setae not prolonged with apical filament. Setation on the legs as follows (I-II-III-IV, solenidia and famulus in parentheses): tarsi 12(ω)-8(ω)-7-7; tibiae 4(k”, φ)-2-3-3; genua 4-4-3-3; femora 5-4-3-3; trochanters 0-1-1-0; coxae 2-1-2-1. Leg chaetotaxy and solenidiotaxy shown in Table 1. Solenidial complement on tarsi 1-1-0-0 ( Fig. 6E ); no solenidia on other leg segments. Subcylindrical solenidion ω on tarsi I and II, usually inserted dorsally, near seta ft ’’. Length of solenidia on tarsi I, II 4–7. Ereynetal organ (φ) on tibia I oval ( Fig. 6C ). Ereynetal organ with famulus k” 6–8 long and ordinally seta l”, named guard seta, 9–12 long: length of famulus 63–80% the length of guard seta ( Fig. 6D ). Famulus forked distally ( Fig. 6D ). Femur IV with strong transverse constriction distinctly separating distal part. Claws approximately 10 times longer than wide and containing inconspicuous dents.

Single and double prime marks setae on anterior and posterior sides of the given leg segments, respectively. Parentheses refer to paired setae.

Type material and deposition. The holotype (male) and 7 paratypes (3 males and 4 females) collected by T. Waki are deposited at the Meguro Parasitological Museum in Tokyo , Japan (collection number: 21305 for the holotype, and 21306A–G for the paratypes as mounted slides). The remaining 4 paratypes are deposited at the Collection of Arachnida , Department of Zoology, National Museum of Nature and Science , Tokyo ( NMNS), previous name was the National Science Museum ( NSMT), each specimens labeled as TW-1, 2, 3, 4 on mounted slide. The type series were selected from 158 specimens, sampled from lungs of Tauphaedusa tau Boettger, 1877 (adults with shell length and width ca. 1.2 cm and ca. 0.3 cm, respectively), which lived in a litter layer in Rinshino-mori Park (35°37′28″N, 139°42′12″E, ca. 120,000 m 2, Fig. 1 ), a forest city park in Tokyo Metropolitan area , Japan, on June 2 and July 7, 2016. Forty-nine hosts were sampled, and 23 hosts were infected (infection prevalence: 46.9%).

Additional material. Two out of the 158 specimens were used for molecular analysis. The remaining specimens are stored in T. Waki’s personal collection.

Etymology. The name refers to the location where the type series was sampled.

Remarks. Setations of legs, palptarsus, and aggenital area and the morphology of famulus on tibia I in the genus Riccardoella are shown in Table 2. Riccardoella tokyoensis n. sp. is distinguished from other species of this genus by the following characters: tibia I with 4 setae (5 setae in other species); tibia II with 2 setae (3 setae in other species); femur I with 5 setae (4 or 6 setae in other species); absence of seta on trochanter I (1 seta in other species); body and idiosoma ca. 50–90% the length of those in the other species; length of setae on idiosoma ca. 25–70% the length of those in the other species (e.g., setae c 1 6–11 μm and 15–37 μm in R. tokyoensis and the other species, respectively).

Riccardoella tokyoensis resembles R. (P.) novaezealandiae Fain and Barker, 2004 in having 8, 7 and 3 setae on tarsus II, tarsi III–IV and femur III, respectively. However, the new species differs from R. (P.) novaezealandiae by the morphological features described in the previous paragraph. Additionally, R. (P.) novaezealandiae has the following morphological characteristics differing it from the new species: the presence of seta on trochanter I; femora I–II with 4 and 3 setae; coxa III with 3 setae; palptarsus with 4 setae; tarsus I with famulus: spoon-like in its apical part, and length equivalent to the guard seta; one pair of pseudanal setae.

Gene sequences and phylogenetic reconstructions. The sequences of mitochondrial COX1 (658 bp long) from R. tokyoensis were submitted to Genbank (accession numbers KY659465 and KY659466 ).

Comparing the COX1 amino acid sequence from R. tokyoensis with those of other species in GenBank’s protein database revealed that Ereynetidae sp. (Accession: AFW13453) is the closest relative (identity: 85%). The phylogenetic tree showed that the supercohort Eupodides, including the new species, formed a tight clade (boot strap value: 99) ( Fig. 9 ). Although the relationship was weak, Ereynetidae spp., including the new species, formed a monophyletic clade (boot strap value: 57) that was most closely related to Tydeidae . Additionally, the tree did not reject the sister-group relationship between Tydeoidea and Eupodoidea within Eupodides.

Figures

FIGURE 1. Sampling site of Riccardoella (Proriccardoella) tokyoensis n. sp..

FIGURES 2A, B. Riccardoella (Proriccardoella) tokyoensis n. sp.: male (paratype, male 21306D). A—dorsal view, Bventral view and coxae.Scale bar 50 µm. Arrows:variation of setae 3a, ps 1 and ps 2.

FIGURES 3A, B. Riccardoella (Proriccardoella) tokyoensis n. sp.: aggenital area in ventral view. A—female (paratype, 21306B), B—male (holotype, 21305). Scale bar 20 µm. Arrows:bases lacking setae.

FIGURES4A, B.Riccardoella (Proriccardoella) tokyoensisn. sp.: gnathosomain ventral view (paratype, male 21306D).Agnothosoma, B— right palptarsus.Scale bar 20 µm and 10 µm for fragments A and B,respectively.

FIGURES 5A–D. Riccardoella (Proriccardoella) tokyoensis n. sp.: right legs except for coxae in antiaxial face (paratype, male, TW-3 in NMNS).A–D—Leg I–IV, respectively.Scale bar50 µm.

FIGURES 6A–E. Riccardoella (Proriccardoella) tokyoensis n. sp. (male paratypes): setae and erenynetal organ on idiosoma and legs. A—setae h 1 and h 2 on idiosoma (paratype, TW-4 in NMNS), B—setae f 2 on idiosoma (arrow: a setal base) (paratype, TW-4 in NMNS), C—erenynetal organ φ, on tibia I (paratype, TW-3 in NMNS), D—famulus k” and guard seta l” on tibia I (paratype, TW-3 in NMNS), E—solenidion ω, and seta ft” on tarsus I(paratype, male in NMNS).

FIGURES 7A–C. Riccardoella (Proriccardoella) tokyoensisn. sp.: variation and defluxion of setae on idiosoma. A—doubled setae c 1 (arrows) (male, paratype 21306A), B—doubled setae 4a (arrow) (male, paratype 21306D), C— setal base with defluxion of seta ag 3 (arrow) (female, paratype 21306B).

FIGURES8A, B. Riccardoella (Proriccardoella) tokyoensisn. sp.: variation of lines between setaed 1 and e 1 on idiosoma.Aw-shaped lines (male, paratype 21306A), B—v-shaped lines (male, paratype 21306E).

FIGURE 9. Phylogenetic trees of Riccardoella (Proriccardoella) tokyoensis n. sp. and related taxa obtained from the Maximum-likelihood method using partial amino acid sequences of COX1. Only boot strap values above 50% are shown.The outgroup is Eniochthonius crosbyi (accession number in GenBank:AKT66632).