J. Acarol. Soc. Jpn., 20(2): 87-93. November 25, 2011 © The Acarological Society of Japan http://acari.ac.affrc.go.jp/ 87 First record of Hypoaspis (Gaeolaelaps) praesternalis Willmann (Acari: Mesostigmata: Laelapidae) from Japan 1 2 Miki SAITO * and Gen TAKAKU 1Hokkaido Research Organization, Kamikawa Agricultural Experiment Station, Pippu 078-0397, Hokkaido, Japan 2Hokkaido University of Education Sapporo, Ainosato, Kita-ku, Sapporo 002-8502, Hokkaido, Japan (Received 18 April 2011; Accepted 9 June 2011) ABSTRACT Hypoaspis (Gaeolaelaps) praesternalis Willmann, 1949, was collected from the soil of spinach-cultivated fields in greenhouses located in Hokkaido, northern Japan. This is the first record of H. (G.) praesternalis from Japan. Intraspecifi c variation was apparent in the length of the spermatodactyl of the male chelicera. Key words: Acari, Laelapidae, Hypoaspis (Gaeolaelaps) praesternalis, spinach fi elds, Japan INTRODUCTION The astigmatid mite species Tyrophagus similis Volgin is known as a harmful mite affecting the growth of spinach. We have investigated native predatory insects and mites to suppress the population of such Tyrophagus mites in spinach fi elds in Hokkaido, northern Japan, and collected several species of predatory mesostigmatic mites that could act as natural enemies (Saito and Takaku, 2010). One of them was identified with a laelapid species assigned to Hypoaspis (Gaeolaelaps) praesternalis Willmann, 1949 (Gamasina: Laelapidae), and this is the fi rst record of this species from Japan. In the present study, we briefl y describe the species based on male and female specimens with reference to variation in the length of female dorsal setae and the spermatodactyl of the male chelicera. MATERIALS AND METHODS Native predatory mites (Acari: Gamasina) were collected from the soil of spinach-cultivated * Corresponding author: e-mail: [email protected] This study was supported by a grant from “Research and development projects for application in promoting new policy of Agriculture Forestry and Fisheries” (No. 22005) from the Ministry of Agriculture, Forestry and Fisheries. DOI: 10.2300/acari.20.87 88 Miki SAITO and Gen TAKAKU fi elds in greenhouses located in Hokkaido, northern Japan. Soil was collected within 5 cm depth from the surface, and brought back to the laboratory in paper envelopes as soon as possible. The mites were extracted from the samples with a modifi ed Tullgren apparatus (screen mesh, 1 mm; light bulb, 40 W). In this apparatus, animals were collected in an acrylic jar containing 70% ethanol. Three hundred milliters of the soil was placed in the apparatus, and kept there for 2 days. Sorting of the mites was done by transferring the sample to a watch glass and examining the mites under a stereoscopic microscope. Some of the mites were mounted whole on glass slides in Hoyer’s medium (Krantz, 1978). Several mite specimens were dissected under a stereoscopic microscope after clearing in lactic acid. Each body part was mounted in Hoyer’s medium or polyvinyl alcohol–lactic acid mixture (PVA) medium. Observations were made with a light microscope and a differential interference contrast microscope. All measurements are given in micrometers (μm). Measurements in each description are provided as the range and averages with standard deviation in parentheses. The dorsal chaetotaxy follows the description by Lindquist and Evans (1965). Other terminology follows that of Evans and Till (1966). Voucher specimens have been deposited in the Zoological Collections of the Graduate School of Science, Hokkaido University, Sapporo, Japan. In this study, the generic and subgeneric concepts follow those by Evans and Till (1966), and we considered Gaeolaelaps as a subgenus of the genus Hypoaspis. Beaulieu (2009) gave generic status to Gaeolaelaps with a detailed description of the genus, and as a result, most species of the subgenus Gaeolaelaps were given a generic status. However, many species described under the subgenus Gaeolaelaps have been retained in the genus Hypoaspis s. lat. yet. To prevent confusion, we tentatively adopted a broader concept of the generic status of Evans and Till (1966) in the present study. DESCRIPTIONS Hypoaspis (Gaeolaelaps) praesternalis Willmann, 1949 [Japanese name: Tankan-hosotogedani, new] Hypoaspis praesternalis Willmann, 1949: 115–116, fi gs. 12, 13. Hypoaspis nolli Karg, 1962: 62–64, fi gs. 24, 25. Hypoaspis (Gaeolaelaps) praesternalis: Evans and Till, 1966: 173–175, fi g. 19. Female: Dorsum (Fig. 1A): Dorsal shield entire, reticulated, and in possession of 39 pairs of simple setae; length 408–476 (433.0±22.6), width at the level of coxae II 217–261 (229.4±13.6) (n=9). Two pairs of dorsal setae (px2 and px3) present between the J- and Z-series. Length of dorsal setae as follows: j1, 15–24 (19.9±3.0, n=7); j2, 21–30 (24.9±3.7, n=7); j3, 25–41 (33.2±4.6, n=9); j4, 27–38 (33.0±3.7, n=9); j5, 27–39 (33.3±4.2, n=9); j6, 30–39 (34.1±3.0, n=9); z1, 14–25 (20.1±4.6, n=7); Z5, 49–64 (57.8±4.4, n=8). Venter (Fig. 1B): Presternal area membranous and not sclerotized; surface reticulate and granular. Surface of sternal shield reticulate, pronounced laterally and anteriorly; 3 pairs of simple setae and 2 pairs of pores present; length 107–116 (111.8±2.7), width at the level of coxae II 77–85 (80.7±2.5) (n=9). Metasternal shield absent. One pair of simple metasternal setae and pores inserted on the membrane posterior to the sternal shield. Genital shield reticulate; width at Hypoaspis (Gaeolaelaps) praesternalis from Japan 89 the level posterior to genital setae 62–83 (68.0±6.6) (n=9); tongue-shaped with slightly convex posterior; 1 pair of simple genital setae lying on lateral margin of the shield. Anal shield reticulate; inverted triangle-shaped with a pair of simple paranal setae and a simple postanal seta; length 65–83 (69.9±6.4), width 68–81 (72.3±4.9) (n=9). Peritreme extends to the middle of coxa II. Peritrematal shield free from exopodal shields; anterior part fused with dorsal shield. Gnathosoma: Hypostome with 3 pairs of hypostomatic setae and a pair of deutosternal setae. Deutosternal groove with 6 transverse rows of denticles. Tectum denticulate. Fixed digit of chelicera with a pilus dentilis and 7 or 8 teeth; movable digit with 2 large teeth; length of movable digit 55–57 (55.8±1.3) (n=3). Legs: Tarsi I–IV with claws and ambulacra. Setae on tarsi II–IV relatively stout basally, tapering distally. Setae pl2 and pl3 on tarsus IV relatively stout, blade-like, and with blunt tip. Leg chaetotaxy typical for the genus; chaetotaxy as follows (femur; genu; tibia): I: 2, 2/1, 3/3, 2; 2, 3/2, 3/1, 2; 2, 3/2, 3/1, 2 II: 2, 3/1, 2/2, 1; 2, 3/1, 2/1, 2; 2, 2/1, 2/1, 2 III: 1, 2/1, 1/0, 1; 2, 2/1, 2/1, 1; 2, 1/1, 2/1, 1 IV: 1, 2/1, 1/0, 1; 2, 2/1, 3/0, 1; 2, 1/1, 3/1, 2 Male: Dorsum: Dorsal shield entire; dorsal ornamentation similar to that of female; length 335–384 (356.6±17.7); width 187–208 (195.4±7.5) (n=9) at the level of coxae II. Dorsal z1 ABj1 j2 j3 j4 j5 px2 px3 Z5 Fig. 1. Hypoaspis (Gaeolaelaps) praesternalis Willmann, female. A, dorsum; B, venter. 90 Miki SAITO and Gen TAKAKU Table 1. Variation of dorsal setae in the examined male specimens of Hypoaspis (Gaeolaelaps) praesternalis. ( ＋ , present; － , absent) Dorsal setae Specimen Number of dorsal setae px2 px3 S1 number Left Right Left Right Left Right Left Right 68 －－ ＋＋ －－ 37 36 113 ＋＋ ＋＋ ＋＋ 39 38 114 ＋＋ ＋＋ ＋＋ 39 38 137 －－ －＋＋＋36 38 146 －－ －＋ －－ 37 34 150 －－ ＋ －－－37 35 215 ＋＋ ＋＋ ＋＋ 38 38 422 ＋＋ ＋＋ ＋＋ 39 39 473 －－ ＋ －－＋ 37 38 chaetotaxy similar to female chaetotaxy, except for some variation; most specimens with paired px3 and some lacking both px2 (Table 1); some dorsal setae (e.g., one of paired z3, z6, J2, and S1) absent in some cases, paired S1 absent in a few specimens, and number of dorsal setae variable as shown in Table 1. Venter: Surface of holoventral shield reticulate; length 282–333 (300.7±18.0), width at the level of coxa II 64–76 (70.1±3.7), width at the level of coxa IV 113–145 (128.9±11.5) (n=9); possesses 4 pairs of setae in the sternal region, 4 pairs in the genito-ventral region, and 3 normal setae in the anal region. Peritreme same as in the female. Gnathosoma (Fig. 2): Gnathosoma same as in the female. Fixed digit of chelicera with a pilus dentilis, 1 or 2 distal teeth, and 2–4 proximal teeth; movable digit unidentate, with a long spermatodactyl; length of movable digit 25–36 (30.8±3.2); length of spermatodactyl of chelicera variable; length from base of movable digit to extremity of spermatodactyl 61–82 (72.2±8.0) (n=9); ratio of length of spermatodactyl to movable digit 1.80–2.77 (2.38±0.40) (n=9). Legs: Leg chaetotaxy same as that in the female. Each leg without spurs and protuberances. Material examined: 1♀, 3♂, soil of spinach-cultivated fi elds in greenhouses in Higashikawa, Hokkaido Prefecture, 1-X-2009, M. Saito; 6♀, 4♂, Higashikawa, Hokkaido Prefecture, 1-X- 2009, M. Saito; 2♀, 1♂, Asahikawa, Hokkaido Prefecture, 5-X-2009, M. Saito; 1♂, Eniwa, Hokkaido Prefecture, 26-X-2009, A. Iwasaki. Distribution: This species has been recorded from Europe (Evans and Till, 1966; Karg, 1962; Lapina, 1976; Willmann, 1949), Africa (Evans, 1953; Ryke, 1963; Van Aswegen and Loots, 1970), Russia (Bregetova, 1977), and China (Ma et al., 2001; Teng, 1982).