New data on freshwater psammic Gastrotricha from Brazil

Abstract Current knowledge of freshwater gastrotrich fauna from Brazil is underestimated as only two studies are available. The present communication is a taxonomic account of the first-ever survey of freshwater Gastrotricha in Minas Gerais State. Samplings were carried out yielding six species of three Chaetonotidae genera: Aspidiophorus cf. pleustonicus, Ichthydium cf. chaetiferum, Chaetonotus acanthocephalus, Chaetonotus heideri, Chaetonotus cf. succinctus, Chaetonotus sp., and also an undescribed species belonging to the genus Redudasys (incertae sedis): this is the first finding of specimens of Redudasys outside of original type locality. These preliminary observations suggest that the knowledge of the biodiversity of Gastrotricha in the Minas Gerais State, as well as in the whole Brazil, will certainly increase as further investigations are undertaken, and that freshwater Macrodasyida may be more common than previously thought.

known, possibly due to their microscopical size, body fragility, which make their study very diffi cult (Hochberg and Litvaitis 2000;Balsamo and Todaro 2002;Balsamo et al. 2005Balsamo et al. , 2008. However, despite the minute body size, they are recognized to have both a complex anatomy and life cycle (Weiss 2001).
Th e taxon consists of nearly 750 named species grouped into two orders, Macrodasyida and Chaetonotida (but see Kieneke et al. 2008), which are greatly diff erent in morphology, reproductive biology and ecology (Balsamo and Todaro 2002;Todaro and Hummon 2008). Macrodasyida comprise about 300 worm-like species, all interstitial in marine and estuarine habitats except for the two freshwater ones recorded only from their type locality (Hummon and Todaro, 2010): Marinellina fl agellata Ruttner-Kolisko, 1955 (Austrian river Ybbs) and Redudasys fornerisae Kisielewski, 1987 (Brazilian dam on the savannah near São Carlos city). Th e roughly 450 species of Chaetonotida are smaller, tenpin-shaped, and colonize marine, brackish and especially freshwater habitats, where two thirds of the species can be found.
Th e biodiversity of the Gastrotricha fauna in Brazil is still underestimated (Kisielewski 1991; Marques and Lama 2006; Garraff oni and Araujo in press) because, until now, only few studies have focused on the diversity and distribution of this taxon both in fresh waters (Kisielewski 1987(Kisielewski , 1991 and in marine waters Rocha 2004, 2005).
Regarding the freshwater habitat, Kisielewski (1991) reported 14 genera (including three new genera), and 59 species (26 of which new species), from various regions of São Paulo State (cities of São Paulo and São Carlos; Juréia Ecological Reserve), of Mato Grosso do Sul State (city of Corumbá), and Pará State (cities of Belém and Benevides), and from diff erent habitats, such as ponds, reservoirs, rivers, puddles in the tropical forest, mangrove and estuaries. In this study, the author stressed that the diversity of Brazilian fauna of inland-water Gatrotricha appears unusually high, and recommended further faunistic, detailed studies. However, no survey was done later on (Garraff oni and Araujo in press).
Th us, the aim of the present study is to provide the fi rst records of the Gastrotricha fauna from the State of Minas Gerais. Th is is the fi rst of a series of surveys that will be realized as an eff ort to increase the taxonomic and biogeographic knowledge of the Brazilian Gastrotricha, with special emphasis on the State of Minas Gerais. Furthermore, with the aim to stimulate new research on this group in Brazil, Garraff oni and Araujo (in press) prepared a taxonomic key for all Brazilian freshwater and marine Gastrotricha, and listed the main morphological characters used to identify species as a glossary with terminologies in Portuguese.
Th e morphological study and the identifi cation of gastrotrichs were performed using the terminologies and identifi cation keys presented in Kisielewski (1987), Balsamo and Todaro (2002), Balsamo et al. (2005) and Todaro and Hummon (2008). Th e descriptions followed the convention of Hummon et al. (1992), whereas the locations of some morphological characters along the length of the body were given in percentage units (U) measured from anterior to posterior. In-group systematization of Chaetonotus and Ichthydium followed Balsamo et al. (2009).
Descriptions of putative new taxa are beyond the scope of the present study, and their defi nitive affi liation will be made at the end of the ongoing taxonomical surveys in forthcoming papers. However, we provide a photograph of each taxon and the measurement of the main structures, for the benefi t of researchers working in the same area who might fi nd them in the meantime.
All adult formalin-glycerin whole-mounts specimens are kept in the meiofauna collection of the senior author at the Universidade Federal dos Vales do Jequitinhonha e Mucuri. Material. Soberbo: 2 specimens, Água limpa: 2 specimens, Preto River: 2 specimens, Gouveia: 2 specimens. Description. Th e description is based on a single adult specimen, 212.5 μm in total length. Head with oval edge and body long and wide. Body medium-sized, with head and neck weakly defi ned, but trunk and caudal base clearly distinct. Head with slightly fi ve lobes and two pairs of ciliary tufts. Hypostomion weakly developed as a fi ne transverse furrow appearing as a thin line. Pharynx 56.25 μm in length from the posterior edge of the mouth to the pharyngo-intestinal junction, that lies at U26. Alternating columns of pedunculated, unkeeled, elongate scales along the body.

Taxonomy
Remarks. Th e genus Aspidiophorus counts 30 species in the world with 9 marine species and 21 freshwater (Balsamo et al. 2009) and in Brazil there are fi ve freshwater species (Kisielewski 1991) and three marine Rocha 2004, 2005). Our specimens resemble A. pleustonicus Kisielewski, 1991 due to the long body, fi ve-lobed head and shape of pedunculated scales. However, they can be distinguished from A. pleustonicus, from the size of the mouth, larger than in the original description (Table  1), and the absence of the cuticular rods internal to the pharynx.
Material. Água Limpa: 2 specimens, Soberbo: 1 specimens, Preto River: 5 specimens. Description. Th e description is based on an adult specimen, 236 μm in total length. Head with three lobes and a one pair of ciliary tufts. Five peculiar cephalic scales with long spines present on the head. Two ventral plates at the sides of the hypostomion. Pharynx 65 μm in length from the posterior edge of the mouth to the pharyngo-intestinal junction that is at U27. Th e general long-spine distribution pattern shows two pairs of conspicuous lateral neck spines. Two pairs of long lateral spines at the furcal base.
Remarks. Kisielewski (1991) reported three distinct morphotypes of Chaetonotus acanthocephalus in Brazilian inland waters: two of them were collected in São Carlos city and one in Juréia Reserve. Our specimens appear to be close to one of the morphotypes found in São Carlos due to the presence of two pairs of long spines at the furcal base, and the peculiar transversal row of trunk spines (Kisielewski 1991:54, Figs 65-66). However, the body length, width and the posterior spines of the Diamantina specimens are larger than those observed from São Carlos (Table 3) Fig. h). Material. Água Limpa: 1 specimen, Soberbo: 2 specimens, Preto River: 2 specimens.
Description. Th e description is based on an adult specimen 137.5 μm in total length. Head with three lobes and two pairs of ciliary tufts. Pharynx 41 μm in length from the posterior edge of the mouth to pharyngo-intestinal junction, that is at U29. Anterior scales rounded and posterior ones pentagon-like shaped. Lateral spine denticle located near to the spine end.
Description. Th e description is based on an adult specimen 236.95 μm in total length. Head with three lobes and one pair of ciliary tufts. Pharynx 64.93 μm in length from the posterior edge of the mouth to the pharyngo-intestinal junction (PhIJ), at U27. Hypostomion as a weak transverse furrow. Th ree pairs of lateral parafurcal spines, the two posteriormost longer than the adhesives tube. Adhesive tubes very long and thin.
Remarks. Th e genus Lepidochaetus was originally described by Kisielewski (1991) to group some Chaetonotus species characterized by numerous, rounded, unkeeled  (Kisielewski 1991), due a similar scale shape and distribution, and rearmost lateral spines arranged in three pairs, which gradually grow in length in a caudal direction. However, they can be distinguished from the previously described species by the absence of cuticular rods and the neck sensorial bristles. Distribution. Brazil: Diamantina, Gouveia (Minas Gerais State).
Material. Cabral Mountains:1 specimen; Gouveia:1 specimen; Preto River: 1 specimen. Description. Th e description is based on an adult specimen 201.38 μm in total length. Head with fi ve lobes and two pairs of ciliary tufts. Pharynx 55.48 μm in length from the posterior edge of the mouth to the pharyngo-intestinal junction, lying at U27. On the middle trunk region, a transverse band of fi ve long dorsal spines, all terminally bifurcated, and of equal length (77.6 μm) and thickness. Paired spines at the furca base, not extending beyond the adhesive tube end.
Remarks. Within the subgenus Zonochaeta, four species (C. bisacer, C. cestacanthus, C. dracunculus, C. succinctus) are characterized by the presence of a series of long dorsal spines with concave apices (Balsamo 1990(Balsamo , 1999. In Brazil, only C. succinctus and C. bisacer were previously identifi ed (Kisielewski 1991), and the main diff erence between the two species is the presence of a pair of long spines at the furca base, which extend beyond the adhesive tube tip. Order Macrodasyida Remane, 1925 Genus Redudasys Kisielewski, 1987 Redudasys sp. Fig. 9, Table 7 Material. Água limpa: 8 specimens; Cabral Montains: 4 specimens. Video sequence (format .mov) is available at http://www.megaupload.com/?d=1F7NJ1XI Description. Th e description is based on an adult specimen 461.54 μm in total length. Cephalic cilia occur in one transverse dorsal row as well as in irregularly distributed tufts located at the anterolateral head margin. Th e mouth opening has a diameter of 10.1 μm. Pharynx 153.85 μm in length from the posterior edge of the mouth to the junction with the intestine. Two elongated caudal lobes, 25.64 μm long and 4.76 μm wide. Median caudal cone absent. Only anterior and caudal adhesive tubes are typically present. One anterior tube per side located laterally in the anterior part of the body. Seven tacticle bristles per side along the lateral body and one per side on the caudal end. Two pairs of caudal adhesive tubes. Th e inner tube (7.14 μm long) is usually 2/5 shorter than the external one (11.9 μm long).
Distribution. Brazil: Diamantina, Cabral Mountains (Minas Gerais State). Remarks. Th e specimens found in Minas Gerais State are undoubtedly members of the genus Redudays, an incertae sedis Macrodasyida taxon recorded from a freshwater environment (Kisielewski, 1987). However, the data gathered in the present study allow to exclude their affi liation to the single species described in this genus so far, Redudays fornerisae Kisielewski, 1987. Our specimens presented seven of tactile bristles per side along the body, and one per side on the caudal body end, that is a total of eight bristles per side, and in addition they had one anterior tube per side. Many of the great number of specimens found in our samples showed a large egg in the trunk region. Th e species Redudasys fornerisae presents six tactile bristles per side along the body and one per side on caudal body end, that is a total of seven bristles per side, and in addition they had two anterior tube per side. Furthermore, the description of Redudasys fornerisae was based on six adult individuals (Kisielewski, 1987). Indeed, the specimen used for the description was considered an adult individual by the presence of mature oocytes and a mature egg. For this reason, we strongly believe that the specimen here described is an adult and cannot be considered as an early stage of development of Redudasys fornerisae. Moreover, even in the smaller specimens from the twelve specimens (0,280 mm; Table 7) there are eight tactile bristles per side.

Discussion
Th e fi ndings presented here allow us to draw some remarks on the Gastrotricha of the State of Minas Gerais. It is worthwhile noting that a poor sampling eff ort has allowed us to obtain very interesting faunistic data and to identify seven distinct species, which suggest a high biodiversity of Gastrotricha in this State. Up to now, 22 species of Gastrotricha Chaetonotida had been described from Brazilian rivers with slow water current and quiet habitats (Kisielewski 1991). Th e most striking result of this study was the report of Redudasys specimens from diff erent streams in Minas Gerais State. Th us, the discovery of Redudasys specimens outside of the original record is of great biogeographic interest, as the adaptation of this macrodasyidan taxon to the freshwater habitats could have been followed by considerable radiation, mainly in the neotropical region.
Albeit a high diversity of endemic gastrotrich chaetonotidans has been recorded in the Brazilian fauna (e.g. Undula, Arenotus -Kisielewski 1987, 1991), most of Gastrotricha species and genera found in Brazil have a cosmopolitan distribution. As pointed out by Kisielewski (1987Kisielewski ( , 1991 and Hummon (2007), species of the Chaetonotidae genera Aspidiophorus, Chaetonotus, Heterolepidoderma, Ichthydium, Lepidodermella, Polymerurus have a very wide distribution and are known from Europe, Asia, North and South America (Chaetonotus species were also collected in Africa and Oceania, and Polymerurus species in Oceania). Furthermore, up to now, 60 Chaetonotida species have been reported in Brazilian inland waters and 34 were also found elsewhere in the world, showing that 57% of the freshwater species have intercontinental or cosmopolitan distribution.
Based on preview studies (Kisielewski 1987(Kisielewski , 1991Rocha 2004, 2005) and on our own results, it is important to emphasize that further investigations are needed to increase the knowledge of Brazilian gastrotrich fauna, which likely include a quite higher number of species.