Oribatid mites (Acari, Oribatida) from riverine environments of some islands in Oceania

Abstract A checklist of identified oribatid mite taxa from riverine freshwater environments from six islands in Polynesia (New Caledonia, Tahiti, Moorea, Rurutu, Tubuai, Raiatea) is presented; 18 species, 16 genera and eight families were recorded. Trhypochthoniellus longisetus (Berlese, 1904) and Trimalaconothrus albulus Hammer, 1972 prevailed on distribution. Fortuynia smiti sp. n. (Fortuyniidae) is described from New Caledonia. The new speciesis morphologically most similar to Fortuynia marina Hammen, 1960 from New Guinea, but it differs from the latter by the longer notogastral setae dm, lm, c2, p1, epimeral setae 3b and adanal setae ad1 and the presence of prodorsal lateral ridges.

Our research is based on total oribatid mite material, which was collected by Nathalie Mary and Harry Smit from rivers of six islands of the Pacific region: New Caledonia (Melanesia), Tahiti, Moorea, Rurutu, Tubuai, Raiatea (all Polynesia). The primary purpose of this paper is to present a checklist of identified taxa.
In the course of taxonomic identification we found a new species, belonging to the genus Fortuynia Hammen, 1960 (Ameronothroidea, Fortuyniidae). The secondary purpose of the paper is to describe and illustrate this species under the name Fortuynia smiti sp. n. The genus Fortuynia is proposed by Hammen (1960) with Fortuynia marina Hammen, 1960 as type species. Currently, it comprises 10 species and two subspecies, which collectively are distributed in the Pantropical and Subtropical regions (sensu Subías 2004Subías , updated 2013. The generic characters of Fortuynia were presented by Hammen (1960) and also summarized by Balogh and Balogh (1992) and Bayartogtokh et al. (2009). The identification keys to species of the genus have been presented earlier by Luxton (1986), Marshall and Pugh (2002) and Bayartogtokh et al. (2009).

Materials and methods
The oribatid mite material was collected by Harry Smit and Nathalie Mary from several Pacific Islands. Smit's oribatid mite material: all samples are water samples, made with a dip net. Mary's oribatid mite material: all samples were taken with a surber net when sampled the benthos of the rivers and streams. All specimens were studied in lactic acid, mounted in temporary cavity slides for the duration of the study, and then stored in 70% alcohol in vials. Body measurements are presented in micrometers. The body length was measured in lateral view, from the tip of the rostrum to the posterior edge of the ventral plate. Notogastral width refers to the maximum width in dorsal aspect. Lengths of body setae were measured in lateral aspect. Formula for leg setation are given in parentheses according to the sequence trochanter-femur-genu-tibia-tarsus (famulus included). Formula for leg solenidia are given in square brackets according to the sequence genu-tibia-tarsus. Terminology used in this paper mostly follows that summarized by Hammen (1960), Norton and Behan-Pelletier (2009).

Faunistic aspect
We recorded 18 species belonging to 16 genera and eight families. Ceratozetes hamobatoides Hammer, 1967 is a new record for Oceania (previously known from New Zealand), all other taxa were recorded in Oceania previously. Trhypochthoniellus longisetus (Berlese, 1904) and Trimalaconothrus albulus Hammer, 1972 prevailed on distribution (found in 19 localities on six and five islands, respectively). Also, Hydrozetes lemnae (Coggi, 1897) is registered from 11 localities (on five islands), Scheloribates praeincisus (Berlese, 1910) in six localities (on three islands). The majority of species (13 from 18) were found in 1-3 localities (Table 1). Comparing a previous investigation of oribatid
Material examined. Holotype (male) and six paratypes (all males): Locality 02. Type deposition. The holotype (in alcohol) is deposited in the collection of the Zoological Institute of the Russian Academy of Sciences, St. Petersburg, Russia; two paratypes (in alcohol) are deposited in the collection of the Siberian Zoological Museum, Novosibirsk, Russia; four paratypes (in alcohol) are deposited in the collection of the Tyumen State University Museum of Zoology, Tyumen, Russia.