A new genus and six new species of the Parabathynellidae (Bathynellacea, Syncarida) from the Kimberley region, Western Australia

Six new species of a new genus of the Parabathynellidae are described from the Kimberley Region, Western Australia. The erection of the new genus, Kimberleybathynella gen. nov., is based on the two‐segmented antenna, the partial fusion of the second and third segments of the maxilla, and the setal condition of the uropodal exopodite, where the outer seta is longer than the inner one. The one‐segmented exopodite of thoracopods I–VII and hemispherical form of male thoracopod VIII suggest the close relationship of Kimberleybathynella to the genus Atopobathynella.


Introduction
Bathynellaceans are known from all the continents except Antarctica and inhabit, with a few exceptions, freshwater aquifers. Although their worldwide distribution indicates an origin in the Upper Palaeozoic (Brooks 1962;Schram 1977), it is still controversial whether they entered the ground water via the coastal interstitial (Boutin and Coineau 1987;Coineau 1996) or the hyporheos of the fresh water (Schminke 1981). Recently, the northwestern part of Australia has come to receive the attention of biologists because of the diverse stygofaunas being found in limestone, calcrete, sedimentary, and regolith substrata in fresh, saline and anchialine waters (Humphreys 1999). As is typical of stygofaunas these assemblages are dominated taxonomically by crustaceans and many of them are regarded as having tethyan or gondwanan affinities (Poore and Humphreys 1992;Bruce and Humphreys 1993;Humphreys 1993;Yager and Humphreys 1996;Bradbury and Williams 1997).
Here we report on the occurrence of six new parabathynellid species from the Kimberley Region of Western Australia, five species from alluvial and regolith substrata in the Ord River catchment, East Kimberley and one from a calcrete in a palaeovalley in the Canning Basin ( Figure 1). The bulk of the Kimberley craton has not been submerged in the sea since at least the Palaeozoic (Humphreys 1999) but the peripheral lower elevations were submerged in the Cretaceous and probably the Eocene high sea level; the area was subject to continental ice sheets in the Permian. Careful inspection of the material and the discovery of new characters lead us to propose the establishment of a new taxon, Kimberleybathynella gen. nov., comprising these six new species. This is the fifth genus known from the Australian continent following Hexabathynella Schminke, 1972, Atopobathynella Schminke, 1973, Chilibathynella Schminke, 1973, and Notobathynella Schminke, 1973.

Material and methods
The samples were prepared and mounted in a mixture of glycerin-formalin. For the drawing and investigation, a Nikon Eclipse E600-Microscope with differential interference contrast equipment was used with oil immersion. Type material is deposited in the collection of the Western Australian Museum, Perth (WAM). OIA refers to the Ord Irrigation Area.

Diagnosis
Parabathynellidae. Body elongated and cylindrical. Antennule six-segmented. Antenna two-segmented. Labrum flat. Incisor process of mandible consisting of five spines. Maxilla four-segmented, second and third segments of maxilla half fused. Exopodite of thoracopods I-VII one-segmented. Male thoracopod VIII hemispherical, protopodite slightly protruded, basipodite without setae, inner margin of basipodite drawn out into projection. Distal spine of uropodal sympodite longer and thicker than other spines. Uropodal exopodite bearing a ventromedial seta and two terminal setae, of which the outer seta is longer than inner one.

Etymology
The generic name alludes to the region, where the majority of its species are found. Gender: feminine.

Etymology
The species is named after the large body size.

Description of adults
Size (mm). Body length: " 3.49-3.91, R 3.00-3.22, approximately 10 times as long as wide. Head as long as length of segments 1-4 ( Figure 2). The female differs from the male only in thoracopod VIII.
Antennule ( Figure 3A). Antennule six-segmented. First segment with one seta on inner distal margin, with two simple dorsal setae, and with one dorsolateral, one lateral and one ventromedial plumose setae. Second segment with one group of four plumose setae, one simple seta on inner distal margin and one ventral seta. Third segment with two setae on outer margin, one simple seta on inner distal margin and one ventral seta. Peduncle of third segment with three simple setae. Fourth segment with one stub seta and a plumose seta on dorsal margin, with two stub setae, and with two plumose setae on lateral apophysis. Fifth segment with two setae on inner margin, with two aesthetascs and one simple seta dorsally, and with one lateral aesthetasc. Sixth segment with four terminal setae and three subterminal aesthetascs.
Antenna ( Figure 3B). Antenna two-segmented, as long as the first segment of the antennule, proximal segment without setae, distal segment with two simple setae and one plumose seta terminally and one subterminal seta.
Labrum ( Figure 3C). Labrum flat, with four terminally denticulated median teeth flanked by eight to nine main and six to seven additional teeth on both sides.
Mandible ( Figure 3D). Mandible with incisor process of four teeth. Tooth of ventral edge small and triangular. Spine row consisting of five spines. Palp of one segment, with one apical seta being seven times as long as palp.   Maxillule ( Figure 3E). Maxillule two-segmented. Proximal segment with four setae on inner distal margin. Distal segment with two terminal claws, with three claws on inner edge, and with three simple setae on outer distal margin. The three simple setae barely reaching beyond the base of the terminal claws. Maxilla ( Figure 3F). Maxilla four-segmented. Second segment half fused with third segment; setal formula 2-4-15-1.
Thoracopod VIII. Thoracopod VIII of male ( Figure 3J) hemispherical in lateral view. Protopodite massive, with two hooks on inner margin. Penial region slightly protruded. Epipodite represented by a tiny hemisphere. Basipodite without seta, inner margin of basipodite drawn out into projection. Exopodite triangular, bearing one seta. Endopodite 50% of exopodite, denticulated terminally. Thoracopod VIII of female ( Figure 3K) in form of a bifurcated structure resulting from the basal fusion of left and right thoracopods. Distal end of each branch bifurcated.
First pleomere. First pleomere with a pair of two setae.
Uropod ( Figure 4D, F-H). Uropod bearing 20 spines on inner distal margin of sympodite. Distal spine twice as long as proximal spines of equal size. Endopodite 30% as long as sympodite, drawn out distally into slightly curved spur, with two setae of equal length at base of spur and further two subterminal setae on outer margin. Exopodite as long as endopodite, with two terminal and three lateral setae and one ventromedian seta. Outer member of both terminal setae 1.5 times as long as the marginally thicker inner seta.
Pleotelson ( Figure 4A). Pleotelson with one seta at base of furcal rami on both sides. Anal operculum flat, somewhat concave.
Furcal rami ( Figure 4B, C). Furcal rami 1.5 times as long as wide, with six spines and with two dorsal plumose setae.

Etymology
The species is named after the Kimberley region, where the species was collected.
Head as long as length of segments 1-4. The female differs from the male only in thoracopod VIII.
Labrum ( Figure 6C). Labrum flat, with two terminally denticulated median teeth flanked by seven main and six additional teeth on both sides.
Mandible ( Figure 6D). Mandible as in K. gigantea except the incisor process of three teeth.
Thoracopod VIII. Thoracopod VIII of male ( Figure 6J) hemispherical in lateral view. Protopodite massive, with two hooks on inner margin. Penial region slightly protruded. Epipodite represented by a tiny hemisphere. Basipodite without seta, inner margin of basipodite drawn out into projection. Exopodite triangular, bearing one seta. Endopodite 50% of exopodite, denticulated terminally. Thoracopod VIII of female ( Figure 6K) in form of a bifurcated structure resulting from the basal fusion of left and right thoracopods. Distal end of each branch sharply pointed.
First pleomere. First pleomere with a pair of setae.
Uropod ( Figure 7F, G). Uropod bearing 14-15 spines on inner distal margin of sympodite. Distal spine twice as long as proximal spines of equal size. Endopodite 30% as long as sympodite, drawn out distally into slightly curved spur, with two setae at base of spur and one further subterminal seta on outer margin. Exopodite as long as endopodite, with two terminal and two lateral setae and one ventromedian seta. Outer one of both terminal setae twice as long as the somewhat thicker inner seta.
Pleotelson ( Figure 7E, F). Pleotelson with one seta at base of furcal rami on both sides. Anal operculum flat, concave.
Furcal rami ( Figure 7E, F). Furcal rami 1.5 times as long as wide, with five spines and with two dorsal plumose setae.

Etymology
The species is named after the Argyle area, where the species was collected.

Description of adults
Size (mm). Body length: " 2.38, R 2.28, approximately 10 times as long as wide. Head as long as length of segments 1-4. The female differs from the male only in thoracopod VIII.
Labrum ( Figure 8C). Labrum flat, with two terminally denticulated median teeth flanked by 10 main and one or two additional teeth on both lateral sides.
Mandible ( Figure 8D). Mandible as in K. gigantea except the incisor process of three teeth.
Maxillule ( Figure 8E). Maxillule two-segmented, ornamentation as in K. gigantea except that the three simple setae on outer distal margin of the distal segment exceed the base of the terminal claws.
First pleomere. First pleomere with a pair of setae.
Uropod ( Figure 9E). Uropod bearing 14 spines on inner distal margin of sympodite. Distal spine twice as long as proximal spines of equal size. Endopodite 30% as long as sympodite, drawn out distally into slightly curved spur, with two setae at base of spur and one further subterminal seta on outer margin. Exopodite as long as endopodite, with two terminal setae, one lateral seta and one ventromedian seta. Outer one of both terminal setae twice as long as somewhat thicker inner seta.
Pleotelson ( Figure 9E, E). Pleotelson with one seta at base of furcal rami on both sides. Anal operculum flat, protruded slightly. Furcal rami ( Figure 9D, E). Furcal rami 1.2 times as long as wide, with five spines and with two dorsal plumose setae.

Etymology
The species is named after Mandora, where the species was collected.

Description of adults
Size (mm). Body length: " 1.38, R 1.33-1.41, approximately 14 times as long as wide ( Figure 11). Head as long as length of segments 1-3. The female differs from the male only in thoracopod VIII.
Antennule ( Figure 12A). Antennule six-segmented. First segment with one seta on inner distal margin, with one simple dorsal seta, and with one dorsolateral, one lateral and one ventromedial plumose setae. Second segment with one group of four plumose setae and one simple seta on inner distal margin. Third segment with two setae on outer margin, one simple seta on inner distal margin and one ventral seta. Peduncle of third segment with three simple setae. Fourth segment with one stub seta on dorsal margin, and with three plumose setae. Fifth segment with two setae on inner margin, with two aesthetascs and one simple seta dorsally, and with one lateral aesthetasc. Sixth segment with four terminal setae and three subterminal aesthetascs.
Antenna ( Figure 12B). Antenna two-segmented, setation as in K. gigantea.  Labrum ( Figure 12C). Labrum flat, with two median teeth flanked by four main and three additional teeth on both lateral sides. All teeth terminally denticulated.
Mandible ( Figure 12D, E). Mandible as in K. gigantea except the incisor process of three teeth.
Maxillule ( Figure 12F). Maxillule two-segmented, ornamentation as in K. gigantea except that the three simple setae on outer distal margin of the distal segment exceed the base of the terminal claws.
Thoracopod VIII. Thoracopod VIII of male ( Figure 12L, M) half-spherical in lateral view. Protopodite massive. Penial region protruded. Epipodite absent. Basipodite without setae, inner margin of basipodite drawn out into projection. Exopodite triangular, bearing three setae. Endopodite as large as exopodite, denticulated terminally. Thoracopod VIII of female ( Figure 12N) in form of a bifurcated structure resulting from the basal fusion of left and right thoracopods. Distal end of each branch sharp.
First pleomere. First pleomere with a pair of setae.
Uropod ( Figure 13D, E). Uropod bearing seven spines on inner distal margin of sympodite. Distal spine 1.5 times as long as and twice as thick as proximal spines of equal size. Endopodite 30% as long as sympodite, drawn out distally into slightly curved spur, with two setae at base of spur. Exopodite as long as endopodite, with two terminal setae and one ventromedian seta. Outer one of both terminal setae twice as long as somewhat thicker inner seta.
Pleotelson ( Figure 13E, F). Pleotelson with one seta at base of furcal rami on both sides. Anal operculum flat, protruded slightly.
Furcal rami ( Figure 13E, F). Furcal rami 1.2 times as long as wide, with five spines and with two dorsal plumose setae.

Etymology
The species is named after the setation on pleomeres.

Description of adults
Size (mm). Body length: R 1.56-1.96, approximately 10 times as long as wide ( Figure 14). Head as long as length of segments 1-4. Male unknown.
Labrum ( Figure 15C). Labrum flat, with two terminally denticulated median teeth flanked by five main and seven additional teeth on both lateral sides. Maxillule ( Figure 15F). Maxillule two-segmented. Proximal segment with four setae on inner distal margin. Distal segment with two terminal claws, with four claws on inner edge, and with three simple setae on outer distal margin. The three simple setae on outer distal margin of the distal segment exceed the base of the terminal claws.
Thoracopod VIII. Thoracopod VIII of female ( Figure 16E) in form of a bifurcated structure resulting from the basal fusion of left and right thoracopods. Distal end of each branch blunt.
Uropod ( Figure 16H). Uropod bearing 11 spines on inner distal margin of sympodite. Distal spine 1.5 times as long and twice as thick as proximal spines of equal size. Endopodite 20% as long as sympodite, drawn out distally into slightly curved spur, with two setae at base of spur. Exopodite as long as endopodite, with two terminal setae and one ventromedian seta. Outer one of both terminal setae twice as long as somewhat thicker inner seta.
Pleotelson ( Figure 16G, H). Pleotelson with one seta at base of furcal rami on both sides. Anal operculum flat, protruded slightly.
Furcal rami ( Figure 16G, H). Furcal rami 1.2 times as long as wide, with six spines and with two dorsal plumose setae.

Etymology
The species is named after the presence of six pairs of walking legs in adults.

Description of adults
Size (mm). Body length: " 0.90-1.35, R 1.20-1.45, approximately 12 times as long as wide ( Figure 17). Head as long as length of segments 1-3. The female differs from the male only in thoracopod VIII.
Labrum ( Figure 18C). Labrum flat, with three median teeth flanked by six main and two additional teeth on both lateral sides. Median teeth terminally denticulated.
Mandible ( Figure 18D). Mandible as in K. gigantea except the incisor process of three teeth.
Maxillule ( Figure 18E). Maxillule two-segmented, ornamentation as in K. gigantea except that the three simple setae on outer distal margin of the distal segment exceed the base of the terminal claws.
First pleomere. First pleomere with a pair of setae.
Uropod ( Figure 19D, E). Uropod bearing six (left) or seven (right) spines on inner distal margin of sympodite. Distal spine 1.5 times as long and thick as proximal spines of equal size. Endopodite 30% as long as sympodite, drawn out distally into slightly curved spur, with two setae at base of spur. Exopodite as long as endopodite, with two terminal setae and one ventromedian seta. Outer one of both terminal setae twice as long as somewhat thicker inner seta.
Pleotelson ( Figure 19C, D). Pleotelson with one seta at base of furcal rami on both sides. Anal operculum flat, protruded slightly.
Furcal rami ( Figure 19C, D). Furcal rami 1.2 times as long as wide, with four (left) or five (right) spines and with two dorsal plumose setae.

Discussion
The number of antennal segments, the structure of mouth parts and the form of male thoracopod VIII are considered to be decisive characters in grouping the species as well as in subdividing the family Parabathynellidae (Schminke 1973). In this context the six new species cannot be assigned to known genera, although they display unique features in the characters listed in the diagnosis. A two-segmented antenna is found in Nipponbathynella Schminke, 1973 andHabrobathynella Schminke, 1973; however, in these genera, the second and third segments of the maxilla are either not fused (Nipponbathynella) or are fully fused (Habrobathynella), and the male thoracopod VIII is either cylindrical (Nipponbathynella) or spherical (Habrobathynella). The two-segmented exopodites of thoracopod I-VII and the absence of a ventromedial seta on the uropodal exopodite precludes any relationship of the six new species to both genera. On the other hand, the hemispherical form of male thoracopod VIII in the six new species is very similar to Atopobathynella Schminke, 1973. Other similarities are the onesegmented exopodites of thoracopods I-VII and the presence of a ventromedial seta on uropodal exopodite which suggests possible inclusion of the six new species into this genus. However, Atopobathynella has a one-segmented antenna, a sexual dimorphism on the second segment of the male antennule, a maxilla with clearly separated second and third segments, equal-sized spines on the uropodal sympodite, and on the uropodal exopodite the inner terminal seta, which is usually longer than the outer one (Schminke 1973).
Hence, we propose that the six new species be assigned to the new genus Kimberleybathynella gen. nov., which seems to be closely related to Atopobathynella. The half fusion of the second and third segments of the maxilla is otherwise unknown within the Parabathynellidae and thus regarded as a strong autapomorphy of Kimberleybathynella. In the context of the relationship to Atopobathynella, the characters of equal-sized spines on the uropodal sympodite, and that on the uropodal exopodite, the outer terminal seta is usually longer than the inner one, justify the erection of this genus.
The six new species, K. gigantea n. sp., K kimberleyensis n. sp., K. argylensis n. sp., K. mandorana n. sp., K. pleochaeta n. sp., and K. hexapoda n. sp., can be recognized by several characters listed in Table I. Whereas many of these characters are meristic, some characters are remarkable. Particularly, the presence of the setae on pleomeres I-V in K. pleochaeta and the absence of the thoracopod VII in H. hexapoda. In all the species yet described, of both Parabathynellidae and Bathynellidae, only the first pleomere has a pair of setae or twoor one-segmented appendages as rudimentary pleopod. However, K. pleochaeta cannot be segregated from Kimberleybathynella, as it shares with the other five new species all the characters of the generic diagnosis. The absence of thoracopod VII is rare among known parabathynellids and otherwise present in all species of Hexabathynella Schminke, 1972 andof Hexaiberobathynella Camacho andSerban, 1998. So, one can establish a new genus No. of spines on furcal rami 6-7 5 5 5 6 6 based on this character. However, K. hexapoda does not essentially differ from its congeners in the characters of generic diagnosis and we do not find any need to establish a new genus.

Habitat
Four distinct habitats are represented in the sampling. Weber Plains comprises an alluvial deposit in an abandoned valley of the former course of the Ord River. The area is now included in the Ord Irrigation Area and has partly been subject to intensive irrigation agriculture for several decades, including high pesticide usage on e.g. cotton but the area is now largely under sugar cane. Bores at Argyle Diamond Mine are mostly in the Lamboo Complex comprising extremely fractured fresh granite/diorite, but PB1 is in the basalt of the Antrim Plateau Volcanics. The area has a thin regolith overlying Proterozoic rocks.
Most of the bathynellids and other stygofauna are found in colluvium distant from surface drainage lines, but a few samples were taken from alluvium associated with the drainage lines, which in this region are mostly active only following monsoonal rain. Friday Well bore in the Canning Basin is associated with a mound spring and palaeodrainage line in the Great Sandy Desert, probably with calcrete (A. Storey, personal communication).

Water quality
Water temperature in all cases exceeded 30uC (Table II) with pH.7 and specific conductance within the range 1-4 mS cm 21 . In contrast, dissolved oxygen was generally low and highly stratified in most bores, being ,7% saturation in bore 37S. Unlike many inland sites in Western Australia (Watts and Humphreys 2003;Balke et al. 2004), the salinity of these sites (Table III) lies within the bounds of the world average fresh water