A new genus of water mites (Acari, Hydrachnidia, Wettinidae) from bromeliad phytotelmata in the Brazilian Atlantic rainforest

Abstract Adults of Bromeliacarus cardoso gen. n., sp. n. are described from phytotelmata of Quesnelia arvensis (Vellozo) Mez. (Bromeliaceae) in the subtropical area of the Atlantic rainforest, São Paulo State, Brazil. The new genus Bromeliacarus is proposed and diagnosed, based primarily on the autapomorphic presence of 7–9 pairs of acetabula flanking the gonopore. A possible relationship between Bromeliacarus and other Wettinidae are discussed.


Introduction
Bromeliads phytotelmata (i.e. tank bromeliads) are considered biodiversity amplifiers in the environments where they occur due to the specificity of a high number of species in this habitat (Rocha et al. 2000, Gonçalves-Souza et al. 2010. Despite the taxonomy and biology of several bromeliad-dwellers, organisms are poorly understood (Frank and Lounibos 2008) and there are continuous studies increasing descriptions of new species and genera in different invertebrates groups such as dipterans (Epler 2010, Pinho et al. 2013, beetles (Clarkson et al. 2014, Albertoni and and water mites (Pešić et al. 2015, present study). The water mite fauna of bromeliad phytotelmata is insufficiently known (Kitching 2000). Although the first paper appeared in the early part of the 20 th century (K. Viets 1939), only a few more studies on water mites from this unusual habitat have been published (see review in Kitching 2000 andreferences in Pešić et al. 2015). Recently, an extensive sampling effort in bromeliad aquatic fauna for ecological studies in Brazilian subtropical area of the Atlantic rainforest provides material to improve taxonomic knowledge of bromelicolous water mites. The first paper resulting from that expedition dealt with the new species of the genus Xystonotus (Pešić et al. 2015). In this paper one new genus of the family Wettinidae is described.
After the revision by Cook et al. (2000), Wettinidae is recognized as separate family, which in addition to the Holarctic nominate genus, includes Stormaxonella K.O. Viets, 1962 (South Africa), Tasmanaxona Cook, 1986, Wheenyella Cook, 1986, and Wheenyoides Harvey, 1990 (all from Australia). The new genus described here is the first member of Wettinidae to exhibit a polyacetabulate condition, bearing 7-9 acetabula on each side flanking the gonopore. In other characters, notably in the presence of a large central shield surrounded by a ring of small platelets, the new species is similar to Stormaxonella K.O. Viets, 1962, a monotypic genus known only from streams in South Africa (K. O Viets 1962). This character state is apparently apomorphic, and may represent synapomorphy indicating a close relationship between Bromeliacarus gen. n. and Stormaxonella and members of the family Lethaxonidae which have a dorsal shield similar in structure. Cook et al. (2000) wrote about Lethaxonidae: "We interpret modifications of the first and fourth pair of legs found in members of Lethaxona and Lethaxonella as synapomorphies indicating common ancestry with Wettinidae." (p. 435). The same authors mentioned that a more detailed analysis of the relationship between the genera of Lethaxonidae and Wettinidae based upon on comparative larval morphology (only known for Wettina) is warranted (Cook et al. 2000, p. 441).

Material and methods
The sampling site is located in State Park of Ilha do Cardoso, São Paulo State, Brazil. This area is included in Atlantic Rainforest domain and shows most of coastal phytophysiognomies of rocky shores, mangroves and restingas (Bernardi et al. 2005). Mites were collected from phytotelmata of Quesnelia arvensis (Vellozo) Mez., a bromeliad species with terrestrial and epiphytic habits densely distributed in the understory of restinga. Each leaf of the bromeliad was carefully dissected and washed, and all detritus and water were collected in white trays. Mites and other fauna were extracted and fixed in 80% alcohol. The holotype will be deposited at the Acari Collection of the Departamento de Zoologia e Botânica (DZSJRP), São Paulo State University, Sao José do Rio Preto, São Paulo, Brazil; paratypes are deposited in the Zoological Collection of the Department of Biology, University of Montenegro, Podgorica.

Systematics
Family Wettinidae Cook, 1956 Genus Bromeliacarus Pešić, gen. n. http://zoobank.org/581654AA-B239-4585-BF32-20FACD7359DC Diagnosis. Characters of the family Wettinidae (see Cook et al. 2000): dorsum with a large central shield bearing two pairs of glandularia and a pair of postocularia ( Fig.  2D), flanked by ring composed of 6 pairs of platelets (Figs 1A, 2A), with 1 th , 2 nd , 3 rd , 4 th , and 6 th pairs bearing glandularia; 6 th pair of platelet fused to each other, occasionally on one side 5 th platelet fused with 4 th platelet. Venter with coxal plates and genital field fused into a ventral shield (Figs 1B, 2C, 2E); suture lines indicating posterior edges of anterior three coxal plates weakly indicated but directed posteriorly; IV-L insertion laterally, well separated from each other and without projections; coxoglandularia 1 in posterior edges of Cx-II; Cx-IV without glandularia; coxoglandularia 2 between Cx-IV and genital field. Legs: I-L stocky, I-L-6 with a long and deep claw socket extending over more than half the dorsal segment surface (Fig. 1E), claw large, ventral clawlet apically rounded, slightly longer than main claw (Fig. 1C); legs I-IV without swimming setae. Genital field with 7-9 pairs of acetabula; acetabular plates fused with ventral shield in both sexes (Figs 1B, 2C); suture lines between genital field and ventral shield obliterated; excretory pore incorporated into ventral shield. Gnathosoma with relatively long apodemes (Fig. 1K); palp slender, P-4 bearing two short ventral setae inserting in the centre and a peg-like mediodistal seta (Fig. 1F-G).
Type species. Bromeliacarus cardoso sp. n. Etymology. Named for its occurrence in bromeliad phytotelmata, and the Latin acarus meaning "mite".
Remarks. Adults of Bromeliacarus gen. n. share with those of all Wettinidae the apomorphic characteristic modifications of first leg (short and stocky with tarsal claw sockets exceptionally large and claws large with ventral clawlet slightly longer than main claw) and fourth leg (trochanter being long and massive, tarsal claw sockets reduced) and the posterior orientation of the suture lines between coxal plates. This new species is autapomorphic in having 7-9 pairs of genital acetabula flanking the gonopore. Other members of Wettinidae differ in exhibiting the plesiotypic character state of small number of genital acetabula (i.e., Stormaxonella K.O. Viets, 1962 with four pairs of acetabula, all other genera with three pairs of acetabula but one species of Wettina (W. octopora Cook) with four pairs. Due to the similar structure of dorsal shield, the new genus appears to be related to Stormaxonella K.O. Viets, 1962. This character state is apomorphic and may indicate that both genera belong to a monophyletic group within Wettinidae. However in light of striking difference in genital field and palp (Stomoxanella scutulata is autapomorphic in P-4 bearing one thick, spatulate seta medially in proximal third of segment) it would appear that divergence from a common ancestor have occurred early during wettinid evolution. Cook et al. (2000;437) claim that "the occurence of different clades on widely separated land masses in both the Northern and Southern Hemispheres suggests that members of this family were distributed throughout Pangea before it broke apart during the Jurassic".  -1, 25/14, 1.8; P-2, 44/28, 1.6; P-3, 32/20, 1.6; P-4, 48/15, 3.1; P-5, 28/8, 3.4; gnathosoma vL 72, with apodemes 105; chelicera total L 86. Legs: dL of I-L (Fig. 1D): 41,51,40,52,51,74;44,55,64,72;45,59,72,72;56,66,69,71,74. Male: Idiosoma (ventral view: Fig. 1C) L/W 434/375. Dorsal shield L/W 384/306, ratio 1.26; gnathosomal bay L 77; distance between IV-leg insertions 167; gonopore L/W 54/6, distance between most lateral pairs of Ac 148.

Bromeliacarus cardoso
Etymology. Named after the locality (State Park of Ilha do Cardoso, São Paulo, Brazil) where the new species was detected.
Distribution. Brazil; only known from the type locality. Habitat and biology. Members of Bromeliacarus cardoso sp. n., are unusual about their habitats, because they appear to live only in the water-filled leaf axils of the bromeliads,  where they walk attached to submerged detritus in bromeliads tank or free swimming in water column. Additional collecting effort is clearly needed in order to understand life history as well as habitat preferences of this species. However, as already mentioned by Albertoni and Fikáček (2014), the usual method used for searching for fauna inside bromeliads, i.e. dismantling the leaves one by one and washing the content in a tray, may not to be effective enough for very small species.