Occigamasus, a new genus of pergamasine mites, with description of two new species from the west coast of North America (Parasitiformes: Gamasina: Parasitidae)

Occigamasus n. gen., O. lindquisti n. sp. and O. makarovae n. sp. from Vancouver Island (Canada) and Oregon (U.S.A.) are described. Five other new species and their sites are noted but not enough specimens were available for adequate descriptions. Cycetogamasus californicus (Banks) sensu Hennessey and Farrier, 1988 is transferred to Occigamasus as a new combination.


Introduction
Predatory mites of the Family Parasitidae Oudemans, 1901 are important soil and litter inhabitants in the Holarctic region. The family was divided into two subfamilies Parasitinae Oudemans, 1901 andPergamasinae Juvara-Balş, 1972. Various studies of parasitid mites have been done in Europe (Berlese 1906;Bhattacharyya 1963;Athias-Henriot 1967a, 1967b, 1967c, 1971Micherdzinsky 1969, Hyatt 1980. However, the diversity of these mites in North America has been scarcely investigated with the most important works being those of Banks (1904Banks ( , 1910 and Ewing (1909). Farrier (1988, 1989) re-examined and further described and illustrated the species of Parasitidae described by Banks and Ewing. Initially a systematic revision of thirty species in ten families of gamasine mites was published (1988), including seven species in six genera of Parasitidae, followed by a paper concerning only the family Parasitidae (1989) from North and South Carolina. In the latter paper, fourteen species, including one new genus and four new species were described, and new synonymies, new combination and a lectotype designated.
Scant information is available about parasitid mites in Canada. Richards (1976) published a paper concerning Parasitidae mites associated with bumblebees in Alberta. An estimated 35 species representing 6 genera of Parasitidae were recorded, without attributed names, as occurring in Canada (Lindquist et al. 1979); and that number of species was increased to 51, with almost twice as many species estimated to await discovery (Beaulieu et al. 2019). This paper deals with Pergamasinae mites from North America: Vancouver Island, British Columbia and Alberta (Canada) as well as Oregon (USA). Here, I describe an unusual new genus, Occigamasus and two new species, O. lindquisti and O. makarovae. The sites of other undescribed species belonging to the new genus, which need more specimens to be described adequately, are indicated.

Material and Methods
The mites studied (52 slides) are from the Canadian National Collection (CNC) deposited in the Research and Development center, Agriculture and Agri-Food, Ottawa. E. E. Lindquist collected most of the mites from Vancouver Island and Oregon. L. Russel collected one sample from Oregon and A. Fjellberg another one from Comox Glacier -Vancouver Island.
The specimens were mounted in Hoyer's medium and became flattened, so that not all the characters are easily visible. The morphological terminology and the system of setal notation for the chelicerae and palpi follows Evans and Till (1979). Terminology for the leg chaetotaxy is based on Evans (1963). The setal notation for the idiosomal dorsum follows Lindquist and Evans (1965) and that for the opisthogaster follows Lindquist (1994). The notation for adenotaxy is based on the system presented by Johnston and Moraza (1991) which is slightly different from that established by Athias-Henriot (1969a). For comparison with other papers the nomenclature of Athias-Henriot (1969a) is given in parentheses: gdj2 (gd1); gdj4 (gd2); gds3 (gd3); gds4 (gd4); gdz5 (gd5); gdz6 (gd6); gdZ2 (gd7); gdZ3 (gd8); gdZ4 (gd9). Measurements of female structures: epigynium shield height (h) is the length from the tip of the shield to its posterior margin, epigynium basal width (b) represents the length of the posterior margin; setal distance st-st is a transverse measurement between insertions of the two setae of the pair st on sternal shield. Leg length is taken from the base of the coxa to the apex of the tarsus; tarsus I and IV length were taken from the base of the segment to its apex, without the pretarsus. Measurements in micrometers are specified after each structure. The following abbreviations are used: hyp. hypostomatal setae, pcx. palpcoxal setae. The definition of cingulum follows Athias-Henriot 1977, as a sclerotized strip which fuses the peritrematal shield with the anterolateral corner of the opisthogastric shield at the level of coxa IV.
The material is deposited in the Canadian National Collection (CNC) of Insects and Arachnids, Ottawa and the Museum d'Histoire Naturelle (MHNG), Geneva, Switzerland (one male, two females of O. lindquisti and one female paratype of O. makarovae).

Taxonomy
The new genus has a peculiar combination of features which make it unique in the subfamily Pergamasinae (Juvara-Balş 2002; Hrúzová and Fend'a (2018). The main characteristics to define a new genus in this subfamily are: Both sexes: The position of peritrematal shield in connection with the dorsal and ventral one; the presence or absence of the cingulum (Athias-Henriot 1977); the chaetotaxy of dorsal and ventral idiosoma, and the number of gland-pores, especially the presence or absence of gland-pore gv1; the shape of the gnathotectum and the form of the palpfemoral and palpgenual setae al. Female: the number of teeth on movable digit of chelicera and the characteristics of the epi-and endogynium.
The new genus shares with Paragamasus Hull 1918 sensu lato (Athias-Henriot 1971, Karg 1993, Hrúzová and Fend'a 2018) the following characteristics: the number of dorsal setae and the leg chaetotaxy (Evans 1963), the peritrematal shield, which is free posteriorly and attached anteriorly to dorsal shield, the trifid gnathotectum and the spatulate setae al1, al2 inserted on palpgenu. The form of dorsal setae s1, s2 (very tiny) and those of male's genital lamina, rounded with a concavity at its anterior margin, resemble those described (Micherdzinski 1969, Juvara-Balş 1977 in Aclerogamasus Athias-Henriot, 1971, a former subgenus of Paragamasus sensu lato. The new genus Occigamasus differs from the other genera of Pergamasinae in having four teeth on movable digit of female chelicera and the peritrematal shield free posteriorly. This characteristic is found only in Heteroparasitus (Medioparasitus) athiasae (Juvara-Balș 2002) but this genus is different in many other features. Witalinski (1972) noted a variation of three or four teeth on the movable digit in Heteroparasitus quadratus Witalinski, 1972. The fact that some species have four teeth seems to be an allopatric characteristic. Other characteristics which characterize Occigamasus are the pilose seta inserted on dorsal face of fixed digit as well as the palpfemoral seta al pectinate with four tines (O. lindquisti n. sp.) or more in the other related species. These features are otherwise specific to some genera of the subfamily Parasitinae.
On podonotum all the setae of the dorsal hexagon (z5, j5, and j6) are similar in length and width. In Occigamasus n. gen. seta pd2 is very long on tarsus IV. This characteristic is homoplastic, being described also in some species of Paragamasus, Thenargamasus, Leptogamasus and even in the subfamily Parasitinae (Athias-Henriot 1969a, Micherdzinski 1969, Hrúzová and Fend'a 2018.

Descriptions
Occigamasus new genus Figs. 1-9 Type species -Occigamasus lindquisti n. sp. Diagnosis -Dorsal shield of adult entire in female, with a median transverse suture between the podonotum and opisthonotum in male. Podonotum with 22 pairs of acicular, simple setae, slightly curved; setae s1 and s2 tiny (6-14). Opisthonotal region with 20-21 acicular, simple setae, their tips reaching the following row of setae. Dorsal adenotaxy with five gland pores: gdj2, gdz5, gds4, gdz6, gdZ3. Ventral adenotaxy with three pairs of gland pores: gv1 and gv3 with one solenostome, gv2 with two solenostomes; gv1 located closed to medial line of posterior margin of sternal shield or in vicinity of seta st3. Epigynium subapical structure spindle-like. Endogynium formed as a big sack which has various structures inside. Ventrianal shield with eight pairs of opisthogastric setae, ZV1 very short (6-7), JV5 inserted on soft cuticle. Peritrematal shield free from ventrianal shield posteriorly and attached to podonotal region of holodorsal shield anteriorly.
Gnathotectum simply trifid. Hypognathal groove with 10-11 denticulate rows. Palpgenu with setae al1, al2 spatulate; palpfemoral seta al pectinate with four or more tines. Movable digit of female chelicera with four teeth, movable digit of male with two teeth; dorsal seta on fixed digit pilose. Trochanter IV, dorsally, with a small protuberance bearing a tiny spine at its apex (Fig. 5E).
Diagnosis -Length of idiosoma: 936-940 female, 768-816 male. Both sexes: gnathotectum with three simple prongs, the central one slightly shorter than the lateral ones. Female: epigynial spindle-like structure 72 long; endogynium a double sack with two curved prongs on its posterior margin and one or two denticles on lateral walls; sternal shield with gland pores gv1   located medially on posterior margin; on tarsus IV seta pd2, 240 long. Male: armature of leg II with simple rounded protuberance on genu, triangular spur on tibia and a basal protuberance on femoral apophysis; on tarsus IV seta pd2, 190-216 long.
Etymology -The species is dedicated to the eminent acarologist Evert E. Lindquist who collected the mites and gave us the opportunity to study the material.
Diagnosis -Female endogynium a double sack with a median finger-like protrusion and a membrane with two anterolateral denticles; spindle-like epigynial structure long (66-72). Male femoral apophysis thumb-like.
Etymology -The species is dedicated to Olga Makarova for her major contributions to systematics of Gamasina families, including Parasitidae.
Description -Only the characteristics specific to O. makarovae are described. Chaetotaxy, adenotaxy and poroidotaxy as in the new genus.
Ventral idiosoma -Characteristics of sternal shield, paragynia, metagynial sclerite, epigynium as well as their dimensions as in O. lindquisti. Gland pore gv1 located medially, distance gv1-gv1 = 24. Endogynium (Fig. 7C) a big sack with a median finger-like protrusion on its posterior margin and a membrane with two anterolateral denticles; epigynium with a long  (Fig. 8E). Chelicera (Fig. 8B): movable digit with four teeth; fixed digit with two small teeth between apex and pilus dentilis and behind it a denticulate ridge ended with a tooth; dorsal seta pilose.
Ventral idiosoma -Genital lamina rounded with subgenital microsclerite rectangular with anterolateral corners rounded. Other characteristics as in O. lindquisti.
Gnathosoma -All the characteristics as in female.
Remarks -I could not observe all the characteristics of the deutonymph. The two specimens were squashed so that the posterior part of the idiosoma was in bad condition and the chelicerae were hidden into the gnathosoma. However, I remarked two peculiar characters. On the podosoma the setae s2 and r4 were inserted outside the shield like in Parasitinae (Hyatt, 1980). The seta R1 is located on the opisthonotal shield as in Pergamasinae (Bhattacharyya, 1963). The leg I has apically a ventral fissure which was not mentioned in Pergamasinae.
Probably this strip of desclerotization helps the movement of tarsus I which is a sensory segment.
The most important feature distinguishing the female of O. makarovae from O. lindquisti is the shape of the endogynium (Figs. 2E, 7C). The posterior margin of the endogynium has in O. lindquisti two curved prongs about 12 long while in O. makarovae only a finger-like protrusion. The fixed digit of the chelicera of these two species is different. Both species have two denticles between pilus dentilis and apex. The inner margin of O. lindquisti, which follows the denticles, is smooth whereas in O. makarovae, behind the pilus dentilis, there is a denticulate ridge ended by a tooth. The male of O. makarovae is similar to those of O. lindquisti but it is recognizable by the characteristics of femoral apophysis on leg II and by those of the fixed chelicera. In O. makarovae the femoral apophysis is thumb-like whereas O. lindquisti has a protuberance on its base. The fixed digit of chelicera in O. makarovae has a truncate apex and those of O. lindquisti a slightly hooked one.

Undescribed species of Occigamasus new genus and their sites
In the Canadian National Collection of Acari (CNC) I identified material of other undescribed species belonging to the new genus. Unfortunately, there was not enough material to describe the new taxa properly. The specimens are mounted dorsally or ventrally so that not all characteristics could be observed. The males are absent in some of the samples. To facilitate future systematic studies, I will mention the sites from where they were sampled, the characteristics of the female endogynium which separate these species (Fig. 7) and some morphological features. Unless otherwise indicated, the samples were collected by E. E. Lindquist.

Discussion
The geographical distribution of Occigamasus is, until now, limited to the west coast of North America i.e., Vancouver Island, Oregon and California which are included in the Oregonian biotic province and to the Waterton Lakes National Park, Alberta which belong to the Montanian biotic province (Dice 1943p.128 in Scudder 1979. A preliminary examination of additional material containing the undescribed species 1-5 suggests that in the future we will be able to divide Occigamasus into several species groups. Therefore, for a better understanding of this genus and its species diversity, to find and examine additional specimens from more localities in northwestern North America. The form of setae on the legs, especially those of tarsus IV and tarsus I, the latter dorso-distal sensory field, has been thoroughly examined only in some genera of Parasitidae (Athias-Henriot 1969aMicherdzinsky 1969;Hennessey and Farrier 1989;Al-Atawi et al. 2002). On tarsus I the number and form of solenidia differ among the genera of Pergamasinae (Micherdzinsky 1969, Juvara-Balş unpublished data). For example, Occigamasus has fewer solenidia when compared with Aclerogamasus (Juvara-Balş 1977). The leg chaetotaxy in the whole family needs a revision in order to evaluate the importance of this characteristic in taxonomy.
Another problem brought up during this study, is placement of the species Cycetogamasus californicus (Banks). This species was described as Gamasus californicus by Banks (1904), then transferred by Essig (1958) to the genus Parasitus and subsequently included by Hennessey and Farrier (1988) in the genus Cycetogamasus Athias 1980, subfamily Parasitinae. The genus Cycetogamasus established by Athias-Henriot (1980) belongs to the" neogamasidienne series" (série néogamasidienne Athias-Henriot 1977 which is a different lineage from Pergamasus, Parasitus or even Neogamasus. The main characteristics of females of this genus are the separation of the podonotum and opisthonotum, presence of the cingulum, setae ZV1 very small, and the movable digit with three teeth. Athias-Henriot (1980) added four other species to the genus Cycetogamasus and specified "je range dans ce nouveaux taxon une série, probablement hétéroclite d'espèces "néogamasidienne" (1980 pg. 289). The female of C. californicus differs from those species by the following characteristics: absence of the cingulum, four teeth on the movable digit of the chelicera and dorsal shield not separated, only with a partial transverse split behind setae z6 (Figs. 17, 18, lectotype in Hennesey and Farrier 1988). The common features of female C. californicus with Occigamasus are: scutum peritrematal free posteriorly; on podonotum, 20-22 pairs of acicular setae, s1 and s2 tiny; 22 pairs of acicular setae on opisthonotum; opisthogaster with ZV1 tiny and gv2 double, eight pairs of opisthogastric setae; movable digit of female with four teeth; palpgenual al setae entire and palpfemoral al seta pectinate.
I conclude that C. californicus must be included in the new genus Occigamasus which belongs to the subfamily Pergamasinae Juvara-Balş.
Another species which should be reviewed is Neogamasus sakhalinus Volonikhina, 1993. This species cannot be included in the genus Neogamasus, as defined by Athias-Henriot 1977, for the following reasons: lack of a cingulum in the female and two teeth on male's movable digit, versus one in Neogamasus. The description and figures are not very detailed and need to be augmented with the characteristics of legs chaetotaxy as well as those of the dorsal and ventral adenotaxy. N. sakhalinus belongs to the "neogamasidien series"sensu Athias-Henriot 1980, with genus placement yet to be determined.
The mites included in this heterogeneous group need more research in order to redefine the genus or subgenus categories.
I have had the opportunity to study other material, undescribed species, from the CNC from western and eastern Canada and also from Virginia State, U.S.A. The Parasitidae from North and South Carolina have been identified by Hennessey and Farrier (1989). There are great differences between the specimens from the east and those from the west. The species collected from the eastern Canada and northeastern U.S.A. are more similar with those of Europe. Hennesey and Farrier found in Carolina soils Psilogamasus hurlbutti Athias-Henriot (1969b) (subfamily Parasitinae) which was collected from Tanzania and Phytiogamasus primitivus (Oudemans,1904) (subfamily Pergamasinae) which is a Gondwanian species dispersed in the southern hemisphere (Juvara-Balş and Athias-Henriot 1972). At present the paucity of information on the systematics of Parasitidae mites does not permit a discussion of the relationships between Occigamasus of northwestern North America and other genera found on the east coast of Asia (Athias-Henriot 1977Tseng 1995). Probably their closest relatives may be found on the east coast of Asia.