New and rare species of hyporheic water mites from New Zealand (Acari: Hydrachnidia: Aturidae, Momoniidae), with the description of two new genera, one new subgenus and one new species

Recently collected material as well as material collected in the 1960s of Zelandopsis aturoides Schwoerbel, 1984 shows that this species does not belong in Zelandopsis, but in a new genus described in this paper. Moreover, a new genus was found in recent material from New Zealand, i.e. Acidoturus n. gen., with the type species A. parviscutatus n. sp.. A new subgenus of Momonia, i.e. Zelandomomonia, is erected to accommodate M. hopkinsi Schwoerbel, 1984. Furthermore, a redescription is given for Zelandopsis morimotoi Imamura, 1977 and the first description is given of the female of Notohygrobates kathrynae Cook, 1983.


Introduction
New Zealand drifted away from the Gondwana continent some 85 million years ago. So it is not surprising that the water mite fauna of New Zealand is for a large part made up of endemic genera. However, this applies to lotic genera only. While none of the genera occurring in standing waters is endemic, the share of endemics in the 49 genera occurring in streams and hyporheic habitats is near 70%. Most rich in genera (22) are the Notoaturinae Besch (Cook 1983, 1991, 1992, Pesic et al. 2010, Schwoerbel 1984, Smit 2015. The finding of material in the collection of the late Jürgen Schwoerbel, collected by K.H. Schminke, shed new light on one already published species. Moreover, material recently collected by the author contained included further interesting new or uncompletely documented taxa. The aim of this paper is to publish this new information, including the description of one new species and the proposal of two genera and one subgenus new to science.

Material and methods
The holotype of the new species described in this paper will be lodged in the Museum of New Zealand, Wellington (NMNZ). All non-type material will be lodged in Naturalis Biodiversity Center, Leiden (RMNH). The following abbreviations are used: asl = above sea level; Cx-IVfourth coxae; dgl-2 -dorsoglandularia 2; P1-5 -palp segments 1-5; IV-leg-2 -second segment of fourth leg. All measurements are in µm, measurements of palp and leg segments are of the dorsal margins. Ventral length is measured from the tip of Cx-I till posterior idiosoma margin.
Description -Male: The male matches the description given by Cook (1983), and here only measurements are given: Ventral length 545, dorsal length 510, width 332.
Female: Idiosoma 680 long and 486 wide, ventrally 688 long. Lateral eyes absent. Integument papillate. Dorsum with a large anterior plate, with one pair of glandularia and the preocularia, two pairs of muscle attachments and seven pairs of glandularia, the posterolateral pair enlarged. Coxae as described by Cook (1983) for the male, with a large area of secondary sclerotization lateral to Cx-III and Cx-IV. Genital field with three pairs of glandularia, one of the anterior acetabula divided (probably an individual aberration); genital plates 106 long. Preand postgenital sclerites large. Length of 78,74,82,28;118,168,142. Legs as in male, but I-leg-5 distally with a thin seta reaching to middle of I-leg-6. Excretory pore sclerotized, near posterior idiosoma margin.
Remarks -Thus far, one male only was known from North Island, New Zealand. This male was 486 long and thus smaller than the male of this study. A character not mentioned by Cook (1983) is the papillate integument. The female is described here for the first time. Apart from the genital field, it is similar to the male. Differences concern the pair of glandularia fused with the anterior dorsal plate (in the male free in the integument).
Diagnosis -(Female only) Integument smooth. Dorsal shield small, covering only half of the dorsum, consisting of unpaired anteromedial and posteromedial plates and two pairs of lateral platelets. Anteromedial plate with a pair of postocularia, much larger than posteromedial plate, the latter with two pair of glandularia. Anterolateral platelets each with two pairs of glandularia, posterolateral platelets without glandularia. No "free"glandularia (= dgl-2) on the dorsal shield. Anterodorsal portion of ventral shield protruding into a rounded hood. All coxae pointed. Projections associated with insertion of fourth legs very large. A pair of glandularia medially to insertions of fourth legs. Gonopore terminal in position, genital plates somewhat bulging and extending onto dorsum. Palp rather stocky, especially P4. IV-leg-2 much larger than other segments, suture line separating IV-leg-2 from IV-leg-3 obliterated.
Remarks -The remarkable small dorsal shield, much smaller than the dorsum, is not found in any other notoaturine genus. Moreover, an anteromedial dorsal plate much larger than the posteromedial plate, is also unique within the Notoaturinae. The configuration of the glandularia on the dorsal shield and the shape of the fourth leg are similar to those in Planaturus Cook, but the latter genus has a much larger dorsal shield with the anteromedial and posteromedial dorsal plates about equal in size. Furthermore, in this genus the projections associated with the insertions of the fourth legs are much smaller. Large projections associated with the fourth legs are also found in Abelaturus Cook, but species of this genus have a different configuration of the dorsal glandularia. Moreover, Abelaturus species have the gnathosoma attached to a protrusable tube, which is not developed in Acidoturus. Finally, the very stocky leg segments are similar to those of Taintaturus Cook and Hestaturus Cook species, but these genera have different configurations of the dorsal glandularia.
Acidoturus parviscutatus n. sp. Female: Unknown. Type species -Zelandopsis aturoides Schwoerbel, 1984 Etymology -The new genus name is a combination of the name Schwoerbel and the genus name Aturus. Remarks - Schwoerbel (1984) was not certain about the assignment of Zelandopsis aturoides. Now that more material is available, also of Zelandopsis Imamura, it is clear that Schwoerbel's species does not belong to the latter genus. The following differences can be found between Schwoerbelaturus n. gen. and Zelandopsis (in brackets): Dorsal shield without a free pair of glandularia (with a free pair), anteromedial dorsal plate very narrow (of normal width), Cx-I far projecting over frontal margin (not far projecting), P2 and P3 without denticles (with denticles), posterolateral platelet with glandularia (without glandularia), two pairs of glandularia between fourth legs insertion and genital field (one pair), one pair of glandularia near suture line Cx-III/Cx-IV (two pairs). Apart from Evidaturus, no other genus has a similar configuration of dorsal glandularia and plates. Besides a very rugose integument (smooth in the new genus), Evidaturus differs in much smaller projections associated with the insertion of the fourth coxae.
Schwoerbelaturus aturoides (Schwoerbel, 1984)  Remarks -According to Schwoerbel, the holotype should have pigmented lateral eyes. However, lateral eyes are not visible in either the holotype or in the additional three specimens. The slide with the holotype was not labelled properly, with neither Zelandopsis aturoides nor holotype written on it. However, as Schwoerbel (1984) had only one specimen at his disposal, and the specimen matches the description, we can assume that the specimen on this slide is the holotype.
Zelandopsis Imamura, 1977 The genus Zelandopsis was described by Imamura (1977) based on one male only, collected from the Twin Forks Creek, Paturau, South Island, New Zealand. According to Imamura, this male should have no acetabula. I visited this area in December 2018 but was unable to find the stream itself and an unnamed stream in this area was without water mites. However, in the Marlborough Sounds area I was able to collect several males and females of Zelandopsis morimotoi Imamura, which makes it possible to redescribe this species, including the first description of the female.
Remarks -The specimens collected in this study match the description given by Imamura (1977). Imamura was not able to find the acetabula in his only male specimen. As the male was collected during a zoological expedition, and not by Imamura himself, it is likely that it was fixed in ethanol. This makes specimens dark and some structures, like the indistinct acetabula, are difficult to see. Imamura illustrated some indistinct structures posterior to the male gonopore, apparently not aware that these were the acetabula. Another feature not mentioned by Imamura is the long second segments of legs I-III, which are longer than the other segments of these legs. Habitat. Interstitial, but occasionally collected in superficial waters.
Diagnosis -Lateral eyes present. Dorsum with one pair of platelets and three large unpaired plates. Venter soft, Cx-I+II separated from Cx-III+IV. Cx-IV long, with a slightly concave posteromedial margin, forming a genital bay; Cx-IV without a group of long setae near posterolateral margin, but three moderate large setae posterior to insertion of fourth legs. Insertions of fourth legs far distanced from lateral idiosoma margin. Genital field with three pairs of acetabula on a pair of genital plates in female, but in the gonopore field in male. Gonopore field of female much longer than genital plates, pregenital sclerite very small, postgenital sclerite moderately long and somewhat curved. P4 ventrally with one stout and one hair-like seta, P5 not tapering distally, with two stout claws. Legs without swimming setae. I-leg-5 elongated, I-leg-6 stocky, with an elongated claw.
Remarks -Due to the absence of swimming setae, the presence of large dorsal platelets and the atypical palp the species from New Zealand cannot be assigned to Kondia as proposed by Schwoerbel (1984). Previously, four subspecies were known of the genus Momonia, i.e. Momonia s.s., Kondia Sokolow, 1926, Paramomonia Yi & Jin, 2012and Orientmomonia Pešić, 2014. However, none of these subgenera match the description given above, and therefore, I propose to erect a new subgenus to accommodate M. hopkinsi.
was part of the collection of the late Jürgen Schwoerbel. Ulrike Mückenheim (Groß-Gerau) prepared most of the slides. Johannes Postma (Ann Arbor) reviewed the English.