Redescription of adults of Prasadiseius cocytes (Prasad, 1970) (Acari: Otopheidomenidae)

A BSTRACT — Females and males of Prasadiseius cocytes (Prasad, 1970) (Acari: Otopheidomenidae) are redescribed based on live specimens collected during an expedition to Peru in August 2010. Several idiosomal structures, the dorsal and ventral setal pattern, and some details of gnathosoma are illustrated using photographs. Interspeciﬁc variation and presence of seta r5 are also discussed.


INTRODUCTION
described the first otopheidomenid mite, Otopheidomenis zalelestes, based on the specimens that he found in the tympanum of moths (Lepidoptera: Noctuidae) collected in several states of the USA, and erected the new family Otopheidomenidae. Later, Prasad (1968Prasad ( -1987 described several new species from museum-preserved moths of Noctuidae and Sphingidae. These ectoparasitic mites are considered closely related to the Phytoseiidae, a family of predatory mites (Krantz and Khot, 1962;Evans, 1963;Chant, 1965;Chant and Yoshida-Shaul, 1992;Chant and McMurtry, 2007). It is interesting to note that some otopheidomenids have spermatheca similar to the phytoseiids while others do not. The otopheidomenids have the movable digit of chelicera greatly reduced or absent and, with few exceptions (Katydiseius and Orthopteroseius), have a terminal anal shield. Wainstein (1972) proposed a new classification for the Otopheidomenidae and established a new genus Prasadiseius for the mites described from sphingid moths. Zhang (1995) reviewed the systematics and biology of this family, and divided the family into 3 subfamilies: Otopheidomeninae Treat, 1955;Treatiinae Wainstein, 1972;and Katydiseiinae Fain and Lukoschus, 1983. The subfamily Otopheidomeninae includes 3 genera: Noctuiseius Prasad, 1968;Otopheidomenis Treat, 1955;and Prasadiseius Wainstein, 1972. Species of Prasadiseius infest sphingid moths only and species of Noctuiseius and Otopheidomenis infest noctuid moths only. Prasad (1970a) described Otopheidomenis cocytes from sphingid moths (Lepidoptera: Sphingidae) collected in Loreto, Pucallpa, Peru in 1962 on Cocytius duponchel (Poey). Later, it was transferred to Prasadiseius by Wainstein (1972). The genus is characterized by the following features: (1) Dorsal shield entire with the lateral margin partially incised, which divides the shield into the podonotal and opisthonotal region; (2) Podonotal region with 8-9 pairs of dorsal sehttp://www1.montpellier.inra.fr/CBGP/acarologia/ ISSN 0044-586-X (print). ISSN 2107-7207 (electronic) 165 tae; (3) j1 pair of setae absent; (4) Only one pair of ventral setae (JV1) present between the genital (in females) or sternogenital shield (in males) and the anal shield; and (5) Parasitic on sphingid moths. This species was found in unusually heavy infestations on museum preserved specimens of Manduca rustica (Fab.) (Lepidoptera: Sphingidae) collected in Ecuador (Prasad, 2011b). In addition, it was found to be widely distributed in Neotropical countries including Brazil, Ecuador and Peru in South America and Guatemala in Central America (Prasad, 2011c).
It is interesting to note that the immature stages of most species of Otopheidomenidae have not been described and the adults of these mites have not been described in detail using the system of Lindquist and Evans (1965) adapted in Phytoseiidae by Rowell et al. (1978), Chant and Yoshida-Shaul (1989, 1991, 1992, and Chant and McMurtry (2007). Prasad (1970a) did not include a detailed description of P. cocytes. His description was based on specimens found on museum preserved moths that had been collected many years before. Mites of this genus had never been observed alive on live hawk moths until August 12, 2010, when they were seen by the author in large numbers on live moths collected in Amazonian forest of Peru (online video, www.indirapublishinghouse.com). The mites were collected, processed and identified as Prasadiseius cocytes, which is redescribed herein based on fresh material. A large series of photographs is used to illustrate the species that show many more details of its morphology than in previous works, and uses the current idiosomal chaetotaxy as proposed by Prasad (2011a).

MATERIALS AND METHODS
The details of the materials and methods are given in Prasad et al. (2011). After obtaining permit from the Government of Peru, live moths were collected during August 10-18, 2010 and observed. Mites were collected in 70% ethanol and brought to the USA for preparation and identification by the author. Most of the mites were mounted directly in Hoyer's medium. The slide specimens were dried for a week on a slide-warming hot plate (at 45 -47°C) and later rung with Glyptal, and labeled. The author identified the mites using an Accu-Scope 3000 phase-contrast microscope (Accu-Scope, New York, USA) under 400x -1000x magnification. Photographs were taken using a mounted Micrometrics TM camera on the microscope and saved in Photoshop CS2. Measurements were taken directly from the slide-mounted specimens using the Micrometrics system. All measurements are given in micrometers (µm) with the average of the measurements given in brackets. All of the photos of the females and males were taken from specimens collected at the same collection (VP10-36), except for Figs. 21 and 22 (male), which were taken from specimens collected from another collection (VP10-38). Each figure caption has the magnification in which it was taken (200x vs. 400x), followed by the mite collection number (VP10-36 or VP10-38) and the photo number. Voucher specimens will be deposited in the Natural History Museum, Lima, Peru; Museum of Biodiversity, The Ohio State University, 1315 Kinnear Road, Columbus, OH 43212, USA; the US National Museum, Washington, DC, USA; and in the author's collection. The collection data of Prasadiseius cocytes on different moths and locations on which this paper is based are as follows: (1)      setae j3, j4, j5, z2, z3, z5. Note setae z2 and z3 comparatively larger than tiny setae j3, j4, and j5. Scale-like and hexagonal reticulation patterns are clearly seen on the shield (400x, VP10-36: 59).    and right coxa III (RCIII), with 3 pairs of sternal setae (ST1 -ST3) on it. Note distance between ST2 -ST2 much larger than ST1 -ST1 or ST3 -ST3. Also, note vertical distance between ST2-ST3 on each side much shorter than ST1 -ST2. Measurement of vertical distance between ST1 -ST3 and diagonal distance between ST1 -ST3 are also of diagnostic use (400x, VP10-36: 103).                (125)], bent anteromedially (may be straight), located on the anterolateral margin of the idiosoma, beside the podonotal shield. Idiosomal dorsum with 12 pairs of setae, of which 11 pairs (j3, j4, j5, j6, J2, J5, z2, z3, z5, Z5, s4) are on the dorsal shield (DS) and 1 pair (r3) [13 -15 (14)] is on the integument, located lateral to the podonotal shield and close to the peritreme.
Gnathosoma (Fig. 26) -The tectum is rounded anteriorly. The palp length is 105 -120 (112). The spermatodactyl (Fig. 26) is 60 long. Similar to the female, the details of the gnathosoma in the male are difficult to study at the magnification of a phase contrast microscope and may require studies using a scanning electron microscope (SEM).

DISCUSSION
Variation in the dorsal idiosomal setae (Figs. 1-4, 33) -The greatest variation was observed in the j4 and j5 setae. Although these 2 pairs of setae were often present in their normal locations, occasionally, one seta of the setal pair (e.g. j4) was placed well anterior to the corresponding seta on the other side of the body (Figs. 1, 3, 4, 33). Occasionally, a seta was absent on one side but present on the other side (Figs. 17,29). In comparison to j4, setae j5 appeared to be more consistent in its location and position ( Fig. 3) but, occasionally, one was placed well ante-rior to the other (Figs. 1, 17, 18). The position of setae z2 was also variable. These are normally located anterolateral to j3 (Fig. 1), but occasionally they occurred in their normal lateral position but not anterior to j3 (Figs. 3, 17). Setae z3 were located in their normal position, lateral and posterior to z2, and approximately in line with and lateral to j4-j5 (Figs. 1,  3, 4). Occasionally, one or both the J2 setae were not clearly evident or one was slightly shorter than the other (Fig. 2). The same was the case with setae J5 where one appeared shorter than the other and was difficult to observe (Fig. 2). All dorsal setae, except for Z5, were very tiny but easy to observe at 400x magnification. Some of the differences in length of these tiny setae mentioned above could be due to the position of the setae on the dorsal shield or to difficulties in observing and measuring them with the optics that were used. When the setae were observed properly, having the correct depth of focus, their length was normal and within the limit of variation, but when they were photographed one seta would sometimes appear shorter than the other. Prasad (1970a) drew a complete set of setae (12 pairs) on the idiosoma for P. cocytes showing 11 pairs on the shield (8 pairs of podonotal and 3 pairs of opisthonotal) and 1 pair (r3) on soft integument, but did not give the chaetotaxy. It was subsequently provided by (Prasad, 2011a). He did not discuss variation either, which is done in this paper. In his original paper, he showed the z2 setae located anterolateral to j3, z3 in line with j4 -j5, and s4 located posterior to r3 and slightly anterior to z5. These setae are in the same position as previously described, unless otherwise mentioned.
A very important and puzzling variation was found in some of the adult females of P. cocytes that were collected from Peru in this study. The r5 setae, which have never been seen before in any species of Prasadiseius, were found present on soft integument in some adult females (Figs. 27, 28). These were symmetrical, located in their normal position, medial and slightly posterior to the posterior end of the peritreme and posterolateral to s4. In these cases, the r3 setae were always present. In Phytoseiidae, r5 has been considered a variable seta (Chant and McMurtry, 2007).  The same is found in the present study in Prasadiseius spp. A study of a large series of these adults in the future will be necessary to determine if this presence is constant in the species.
Variation in the ventral idiosomal setae -The most significant variation noted in one female was in the sternal setae, in which the ST1 pair of setae and one of the ST2 setae were absent, resulting in the presence of only 3 sternal shield setae versus its normal complement of 6 setae (Fig. 30). The setae in this case were not broken, as no setal bases or sockets were evident. Occasionally, a female was seen having only one of the ST5 setae (Fig. 31). In addition, the ST5 present in adult males was found absent in one male (Fig. 35).
Variation in the shape of the sternal shield -Prasad (1970a) illustrated the sternal shield of this species as being much longer than wide and without showing the anterior and posterior triangular extensions or the shield-shape pattern. These are clearly visible in the present study (Figs. 9,30) and on the paratypes of P. cocytes examined (Fig. 34). It is believed that the use of the measurements of the vertical distance between bases of ST1 -ST3 and diagonal distance between ST1-ST3 for the measurement of the length of the sternal shield is more appropriate than measuring the sternal shield, including the triangular flares that vary in the different specimens.
Variation in the shape of the genital shield -Prasad (1970a) illustrated a rounded posterior margin of the genital shield. In the present study, it was found to be roughly truncated (Figs. 10, 31). This difference may be due to the way the specimens are mounted on slides or to the age of the mite as it was found round when females were gravid and had eggs.
The variations mentioned above seem to be normal interspecific variation. However, presence of r5 is puzzling and needs further investigation. So does study of large population of these mites present on one host if two species or sub-species are present.

REMARKS
The description of different species of Otopheidomenidae using better optics with higher magnification capabilities, such as the use of low temperature scanning electron microscopy LT-SEM and/or regular scanning electron microscopy (SEM), would lead to a better understanding of the morphological features in these mites. The study and description of the immature stages and the study of a large series of these mites are necessary to learn more about the variation in this and other species than is discussed in this paper. Detailed studies of the different gnathosomal structures and leg chaetotaxy are also needed for better understanding of these mites.