New species of water mites from New Guinea (Acari: Hydrachnidia, Halacaridae)

The following new species are described from the Indonesia part of New Guinea: Oxus litoralis, O. reticulatus, Limnesia longiseta, L. papuensis, L. pseudopatens, Procorticacarus minutus, Australiobates hyalinus, A. setosus, A. sylvestris and Arrenurus basegensis. The following new species are reported for the fauna of New Guinea, i.e. Limnochares australica Cook, 1986, Oxus orientalis Walter, 1915, Litarachna denhami (Lohmann, 1909) and Rhombognathus scutulatus Bartsch, 1983. Piona piersigi (Daday, 1900) is redescribed.


INTRODUCTION
Although the first paper on the water mites of New Guinea was published by Daday as early as 1901, it took more than eighty years before the second publication appeared. Imamura (1983) described two new species from Papua New Guinea. Oudemans (1905) described a new Limnesia species from New Guinea, but the (larval) specimen did not belong to the Hydrachnidia. The most comprehensive study was published by Wiles (1997b); he reported 75 species, while four genera (Eylais, Hydrachna, Hydrodroma and Monatractides) were not elaborated upon. Together with the publication of Smit (1996) from Waigeo, the total number of known species from New Guinea now stands at 79.
In March 2010 I made a collecting trip to Papua province (Indonesia), and visited the coastal area between Jayapura and Sentani, the surroundings of Wamena (including Pass Valley), the Nipsan district in the central mountain range and Lake Habbema. A few specimens from other parts of New Guinea will be treatedin this paper as well. Water mites of the genus Monatractides Viets are published in a separate paper (Pešić and Smit 2011). In this paper the remaining water mite genera will be treated.

MATERIALS AND METHODS
All but two specimens presented here were collected in Papua province, New Guinea, Indonesia.This is not explicitely stated for each species in the text of this paper, except for the new species described.
All material was collected by the author, unless stated otherwise.

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ural History Museum, London. All material will be lodged in the Netherlands Centre for Biodiversity Naturalis, Leiden. Measurements of paratypes are given in brackets. All measurements are in µm, measurements of palp and leg segments are of the dorsal margins.

SYSTEMATICS FAMILY LIMNOCHARIDAE GRUBE, 1859
Genus Limnochares Latreille, 1796 Limnochares (Cyclothrix) australica Lundblad, 1941 Material Remarks -The specimens from New Guinea are provisionally assigned to L. australica, as adults are difficult to identify. Variation in size and shape of legs segments, as well as genital field is large, and adults of the Indian L. crinita Koenike, 1898 cannot be distinguished from L. australica (Lundblad 1947, Cook 1967). However, based on larval morphology, Martin and Smit (2002) showed that the two are separate species. I collected at both pools water skaters (Insecta: Gerridae), but none were parasitized. Research on the larval morphology is needed to elucidate the status of this species from New Guinea. New for the fauna of New Guinea.

FAMILY OXIDAE K. VIETS, 1926
The genera Oxus and Frontipoda have been synonymized by Besch (1964), which is followed by Di Sabatino et al. (2009). Oxidae are a cosmopolitan family.

Genus Oxus Kramer, 1877
Thus far only two species have been reported from New Guinea (Wiles 1997b).
Diagnosis -Coxal field with two pairs of glandularia, PI and PIV relatively long, PV stocky.
Etymology -Named for the type locality being situated along the coast.

Oxus orientalis
Remarks -The specimens from New Guinea are morphologically similar to the specimens from New Caledonia and Australia, but differ in dimensions of palp and leg segments. Most dimensions of the specimens from New Guinea are larger, but 323 length of IV-leg-5 is intermediate between specimens from New Caledonia and Australia. As there is much variation in lengths of leg segments , I assigned the specimens from New Guinea to O. orientalis. There are two more species known with only one pair of glandularia on the coxal field (sensu Cook 1986), i.e. O. pictus (Daday, 1898)  Diagnosis -Coxae with a reticulate pattern; excretory pore on a long platelet; median strip without glandularia.
Etymology -Named for the reticulated pattern on the coxal area.
Remarks -The combination of coxae with a reticulate pattern, excretory pore on an elongated platelet and a dorsal median strip without glandularia is characteristic for the new species. A number of Australian species and one species from New Guinea have the excretory pore on a platelet (i.e. O. grenada , O. tasmanica , O. neotasmanica , O. zunova  and Oxus michellae (Wiles, 1997)), but in none of these species this platelet is elongated, while the reticulate pattern is absent.
Remarks -The nymph agrees well with the description of Wiles (1997b), who described the species from Lake Habbema itself. It has IV-leg-6 with a very long distal seta, and the stout setae of I-leg-4 are also long.
Remarks -A hyporheic species (Imamura 1983), found in gravel deposits of streams. Thus far only reported from Papua New Guinea.
Diagnosis -Dorsal setae very long; acetabula elongated, lying in an arc in the male.
Description -Male: Idiosoma dorsally 530 long and 328 wide, pear-shaped, colourless to paleyellow. Dorsum with two large plates, anterior plate 188 long and 244 wide, posterior plate 296 long and 284 wide, each plate with two pairs of setae. Posterior plate with two pairs of very long setae, anterior plate with only posterior pair very long ( Figure 3b). Suture lines of coxae indistinct. Posterior part of ventrum sclerotized. Glandula Limnesiae in the middle of third coxae, associated setae posterior of these glandularia ( Figure 3a). Genital field fused with ventrum, with three pairs of acetabula lying in an arc; gonopore 52 long. Acetabula elongated, anterior acetabulum 40 long and 16 wide. Lengths of PI-PV: 15, 70, 44, 72, 30. Ventral margin of PII with an anteriorly placed stout seta, ventral margin of PIV with two short setae and one long seta on a small tubercle (Figure 3c). Lengths of I-leg-4-6: 72, 88, 64. Lengths of IV-leg-4-6: 84, 102, 76; IV-leg-6 with a distal setae, 58 long. Claws of first, second and third legs large with a small clawlet, without claw blade. Legs without swimming setae.
Etymology -Named for the long dorsal setae.
Remarks -The new species is close to Limnesia baderi, but differs in size (the male of L. baderi is dorsally 429 long), the long setae (short in L. baderi) and the acetabula are elongated (rounded in L. baderi) and are lying in an arc (behind each other). Etymology -Named for its occurrence in Papua province.
Remarks -The new species is close to L. buruensis Viets, 1923 and L. argelooi Smit, 1996, but differs in having the first coxae fused medially (lying close to each other but not fused in L. buruensis and L. argelooi), the Glandula Limnesiae are located in the middle of the third coxae (similar in L. argelooi but in posteromedial corner in L. buruensis). Moreover, PIV of L. buruensis is more slender, while both L. argelooi and L. buruensis lack the small setal tubercle of PIV.
Diagnosis -Ventral margin of PII with a broad, posteriorly directed stout seta, which is contracted at its tip.
Deutonymph: Idiosoma 595 -868 long and 486 -656 wide. As adult, with provisional genital field with two fused pairs of acetabula. Ventral margin of PII without seta.
Remarks -The new species is very close to Limnesia patens from Java (Viets 1935) and India (Cook 1967), and differs only in the shape of the palp. The stout seta of the ventral margin of PII is broad and contracted distally in the new species, while in L. patens it is not contracted. Moreover, the longest dorsal setae of PII is longer in L. patens (length 56 in female, 42 in L. pseudopatens), while PIV is much stronger bowed in L. patens. Another very similar species is Limnesia szalayi Viets, 1955 from northern Australia. The latter species has a dorsal platelet, while PIV is more narrowed distally.

Genus Procorticacarus K.O. Viets, 1978
Members of the genus Procorticacarus from Australia were initially described as a subgenus of Corticacarus Lundblad, 1936. The subgenus Procorticacarus, to which all Australasian species belong, was raised to a full genus by Harvey (1998). The genus Procorticacarus is only known from the Australasian region, with 22 species reported from Australia (Harvey 1998, Smit 2001, and nine from New Guinea (Wiles 1990(Wiles , 1994. Remarks -Previously reported from Papua New Guinea and Papua province ("Irian Jaya"), Indonesia (Wiles 1990(Wiles , 1994. Remarks -Previously reported from Papua New Guinea and Papua province ("Irian Jaya") by Wiles (1994).
Procorticacarus kingi (Wiles, 1991) ( Remarks -Previously reported from Papua New Guinea (Wiles, 1991(Wiles, , 1994. The female specimen from Papua province has a differently shaped pre-genital sclerite ( Figure 6). Moreover, the dorsal plates are more angular and with less interspace. However, the specimen is juvenile, and differences may be related to this.  Diagnosis -Small species, with a characteristic configuration of dorsal plates and platelets: two large plates flanked by ten pairs of smaller plates. Posterior large plate flanked by a pair of curved plates.
Etymology -Named for its small size. Remarks -The new species is well characterized by the configuration of the dorsal plates and platelets. The absence of ventral denticles of PII and PIII is rare within the genus, only shared by the Australian P. angulicoxalis (K.O. Viets, 1978).
Remarks -In the slender palp (Figure 8b), I-leg-5 with two slender stout setae of which is longer than the other (Figure 8c) and the genital field with the acetabula lying almost in a line (Figure 8a), the specimen from Waigeo matches the description by Wiles (1997a). Thus far, the species has been reported from Papua New Guinea and Papua province ("Iran Jaya"), Indonesia.
Etymology -Named for the hyaline setae of the legs.
Remarks -The presence of hyaline setae on the dorsal margin of the legs is characteristic for the new species. Australiobates plumosa Wiles, 1997 has somewhat similar setae, but these are more numerous and plumose.
Description -Female. Idiosoma 526 long dorsally and 421 wide, ventral length 583. Idiosoma without platelets or reticulation. Gnathosoma with a long anchoral process. Coxoglandularia 4 near suture line of third and fourth coxal plates. Posterior apodemes of fourth coxal plates long (Figure 11a). Genital field with three pairs of acetabula, these occupying most of the area of the genital field and lying in an arc. Lengths of 90,124,134,34. PIV slender, ventral margin of PIV with 3-4 stiff, thin setae, besides the two stout setae. PII and PIII with 3-4 short, stout setae near or on dorsal margin (Figures 11b, 11c). Lengths of I-leg-4-6: 227, 267, 143. I-leg-5 anteroventrally with two closely inserted, relatively blunt setae (Figure 11d). Lengths of 318,198. All legs with numerous short, fine setae, swimming setae absent. Male: Unknown.
Etymology -Named for the relatively many setae on PIV.
Remarks -The new species is somewhat close to A. bruijni Wiles, 1997, but this species lacks the stiff setae of the ventral margin of PIV, and the genital field is more slender, with the posterior acetabulum not extending posteriorly of the gonopore.
Etymology -Named for its occurrence in the forest.
Remarks -No other Australiobates species from New Guinea has I-leg-5 with anteroventral acute setae and PIV with blunt setae. The only Australian species with the combination of these characters are A. ombatus  (PIV more slender and PV has large downturned setae) and A. rudagus  (PIV with heavy ventral setae). FIGURE 12: Australiobates sylvestris n. sp., holotype female: a -ventral view; b -palp; c -I-leg-5-6. Paratype male: d -genital field. Scale bar = 50 µm. ).
ming setae compared to female, e.g. IV-leg-5 with four and IV-leg-4 with three swimming setae (Figure 13e). All legs with numerous heavy setae.
Female: Idiosoma 778 -1266 long and 624 -1065 wide; colour of chitinized parts as in male. Medial distance of third + fourth coxal plates large ( Figure  14a). Genital plates more or less curved, with anteriorly two acetabula on a platelet, posteriorly 7 -12 acetabula on a platelet and in between 1 -2 acetabula lying free in the idiosoma (Figure 14b). Pregenital sclerite 92 wide, postgenital sclerite 84 wide. Lengths of 136,66,134,42. Ventral margin of PII convex, with two short, heavy setae medially and one on dorsal margin (broken off in illustrated palp). PIII with three heavy setae (one seta lost in illustrated palp). Ventral margin of PIV with two small, setal tubercles, well distanced from each other; third ventral seta on a small tubercle, which is lying more distanced from ventral margin ( Figure  14c). Lengths of I-leg-4-6: 170, 203, 211 (the latter till tip of segment). Lengths of IV-leg-4-6: 211, 243, 194. All legs with numerous swimming setae and numerous heavy setae.
Remarks -The illustrations of Daday (1901) are very sketchy, and therefore new illustrations are provided. Daday (1901) reported the species from German New Guinea, nowadays Papua New Guinea.