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Citation: Michalik P, Piacentini L, Lipke E, Ramírez MJ (2013) The enigmatic Otway odd-clawed spider (Progradungula otwayensis Milledge, 1997, Gradungulidae, Araneae): Natural history, first description of the female and micro-computed tomography of the male palpal organ. ZooKeys 335: 101–112. doi: 10.3897/zookeys.335.6030
The recently described cribellate gradungulid Progradungula otwayensis Milledge, 1997 is endemic to the Great Otway National Park (Victoria, Australia) and known from only one male and a few juvenile specimens. In a recent survey we recorded 47 specimens at several localities across the western part of the Great Otway National park. Our field data suggest that this species is dependant on the microclimate in the hollows of old myrtle beech trees since other hollow trees were very much less inhabited. Furthermore, we describe the female for the first time and study the male palpal organ by using X-ray microtomography. The female genitalia are characterized by eight spermathecae which are grouped in two quartets. The spermophor resembles the general organization of gradungulids, but is similar to Kaiya Gray, 1987 by a convoluted appearance within the embolus. The muscle 30 is located in the cymbium and resembles the organization of other non-entelegyne Araneomorphae.
Taxonomy, micro-CT, palp, spermatheca, web, Nothofagus
The family Gradungulidae consists of seven genera with 16 described species from eastern Australia and New Zealand (
We observed a total of 47 specimens (juveniles, females, one male) in the localities depicted in Fig. 1. Several individuals were collected for further analyses. The female genitalia were digested following the protocol of
Distribution map of Progradungula otwayensis in the Great Otway National Park, Victoria (Australia). Red marks indicate localities for the present study; black circles indicate localities given by
A Habitat with supporting web (blue arrow) and sturdy thread (red arrows) connecting with the retreat in the hollow of a Nothofagus cunninghamii tree B Catching ladder in front of a hollow in a large tree fern C Immature male of Progradungula otwayensis holding the catching ladder.
For the micro-CT analyses of the male palp, the sample was dehydrated in graded ethanol and stained with a 1% iodine solution for 12 hours. After washing in pure ethanol, the sample was scanned in ethanol with an Xradia MicroXCT-200 X-ray imaging system (Carl Zeiss X-ray Microscopy Inc., Pleasanton, USA) at 20 KV and 4 W (10.0 scintillator-objective lens unit, 11 s exposure time, 2.18 µm pixel size). The female genitalia were digested with enzymatic cleaner for contact lenses Ultrazyme, and dried after the iodine treatment using hexamethyldisilazane (HMDS). The scan was performed using the same system at 30 kV and 6 W (20.0 scintillator-objective lens unit, 6 s exposure time, 1.18 µm pixel size). The obtained data were processed using the 3D analysis software AMIRA v. 5.4.2 (Visage Imaging, Berlin, Germany). The spermophor was reconstructed by delineation of the contours in each section and a smooth surface was computed using the surface editor. The image stack is stored in MorphDBase under creative commons attribution (ID: P_Michalik_20130802-M-5.1, https://www.morphdbase.de/?P_Michalik_20130802-M-5.1).
ALE anterior lateral eyes
AME anterior median eyes
B bursa
bH basal hematodocha
Cb cymbium
E embolus
EF epigastric furrow
Gl glands
GP genital pockets
m29 muscle 29
m30 muscle 30
mA median apophysis
mH median hematodocha
PE process of embolus
PF postepigastric fold
PLE posterior lateral eyes
PME posterior median eyes
S spermophor
Sp spermatheca
St subtegulum
Te tegulum
Ue uterus externus
tm29 tendon of muscle 29
tm30 tendon of muscle 30
MACN Museo Argentino de Ciencias Naturales (Buenos Aires, Argentina)
MV Museum of Victoria (Melbourne, Victoria)
ZIMG Zoologisches Institut und Museum Greifswald (Germany)
Male holotype: AUSTRALIA: Victoria. Otway Ranges, Aire Crossing Track, 0.5 km N of Aire River crossing, 38°42’S, 143°29’E, 31 Jan 1995, G. Milledge (MV K3260, not examined).
AUSTRALIA: VICTORIA: Great Otway National Park: Little Aire Cascade Trail, E of Lavers Hill, 38.67032°S, 143.49810°E (GPS, ±100m), elev. 330m, 11 Feb 2013, Nothofagus, Eucalyptus, tree ferns wet forest, hand collecting, P.Michalik & M.J.Ramírez (MJR-Loc-125), two females (MACN-Ar 30666); Triplet Falls Trail, E of Lavers Hill, 38.67188°S, 143.49673°E (GPS, ±300m), elev. 300m (GPS), 10 Feb 2013, Nothofagus, Eucalyptus, tree ferns wet forest, hand collecting, P.Michalik & M.J.Ramírez (MJR-Loc-124), three females (MACN-Ar 30667, ZIMG II/28128, ZIMG II/28129); Maits Rest Trail, W Apollo Bay, 38.75492°S, 143.55495°E (GPS, ±200m), elev. 240m, 13–14 Feb 2013, Nothofagus, tree ferns wet forest, hand collecting, P.Michalik & M.J.Ramírez (MJR-Loc-126), one female (ZIMG II/28130); Melba Gully Trail, 38°41.726’S, 143°22.312’E (GPS, ±200m), elev. 328m, 15 Feb 2013, Nothofagus, tree ferns wet forest, hand collecting, P.Michalik & M.J.Ramírez (MJR-Loc-128), one male (ZIMG II/28127).
This species can be distinguished from Progradungula carraiensis by the single process on the embolus of the male palpal organ and the presence of eight spermathecae in the female genitalia.
(Figs 3–4).
Somatic characters of the female of Progradungula otwayensis. A Lateral view of prosoma and opisthosoma (ZIMG II/28128) B Dorsal view of prosoma (MV) C Ventral view of Prosoma (MV) D Frontal view of ocular area (ZIMG II/28128) E Ventral view of opisthosoma F Tarsus of leg I G Tarsus of leg IV H Calamistrum. I Ventral view of spinnerets. Scale bar in F–H is 500 µm.
Female genitalia. A Lateral view of the dome-shaped genital area (compare also to Fig. 3A) (MACN-Ar 30667) B Sagital section through genital area obtained by micro-CT (MACN-Ar 30667) C Posterior view of genital area (MACN-Ar 30667). Spermathecae in anterior (D) and ventral view (E) (ZIMG II/28128). Abbreviation: B bursa; EF epigastric furrow; GP genital pockets; Gl glands; PF postepigastric fold; Sp spermathecae; Ue uterus externus.
(mm, in MV). Carapace length 6.92; carapace width 4.66; caput width 2.66; abdomen length 8.51; abdomen width 7.18. Legs: length of segments (femur + patella/tibia + metatarsus + tarsus = total length): I 11.97 + 14.10 + 11.57 + 2.66 = 40.30, II 9.31 + 10.77 + 8.25 + 2.53 = 30.86, III 7.98 + 9.18 + 7.85 + 2.13 = 27.14, IV 9.98 + 10.91 + 9.44 + 2.13 = 32.46, palp 2.93 + 2.66 + - + 2.79 = 8.38.
Carapace yellowish brown, darker on cephalic area, particularly in eye region. Chelicerae, maxillae and labium reddish brown. Sternum reddish brown marginally, paler centrally. Legs yellowish brown. Abdomen fawn-coloured with dark brown dorsal pigmentation consisting of 3 chevron markings. Carapace longer than wide, widest between coxae II and III. Cephalic area elevated behind eyes (Fig. 3A). Clypeus sloping, as long as the median ocular quadrangle, with a strongly curved anterior border. Fovea pit-like.
Frontal view (Fig. 3D): anterior row slightly recurved, posterior row slightly procurved. Dorsal view (Fig. 3B): anterior row recurved, posterior row slightly recurved. AME < PME < ALE = PLE 0.23: 0.32: 0.35: 0.35. Interdistances: AME-AME 0.18, AME-ALE 0.33, ALE-PLE 0.08, PLE-PME 0.40, PME-PME 0.28. Median ocular quadrangle: length 0.58 mm, anterior width 0.55 mm, posterior width 0.87 mm. Clypeus height 0.50. AME black, remainder white.
Strong, vertical, slightly divergent. Three strong prolateral teeth, evenly spaced. Five very small retromarginal teeth (or denticles) in row on basal half of groove, with a spine on the apico-dorsal side. Stridulatory ridges absent.
Subparallel, external margin strongly curved and ending anteriorly in a bluntly pointed apex (Fig. 3C). Serrula present.
Free. Length 0.83, width 0.87. Apical margin indented, lateral margin subparallel below, sloping in toward apex above (Fig. 3C).
Length 3.33, width 2.20. Elongate, shield-shaped with pointed apex which extends back midway between coxae IV (Fig. 3C).
1423. Trochanters shallowly notched. Superior claws of 1st and 2nd legs dissimilar, with raptorial proclaws long and strongly developed (Fig. 3F), retroclaws shorter. Inferior claws of legs I and II slender and strongly hooked. Superior claws of legs III and IV similar (Fig. 3G). Accessory claw setae on all tarsi. Distal half of tarsus I and II with strong ventral setae. Calamistrum short, located in second quarter of metatarsus 4 (Fig. 3H).
(Approximate, slightly asymmetrical.) Femur I d (r2p1)-r2-r1-p1-1-2-p1-2-p1-2-2-3ap v 0-p1-0-0-0; patella r 1; tibia d 2-0-2-p1-0-p1-3 v 2-0-0-2-p1-0-2-0; metatarsus d r1-p1-p1-0-0-0-0 v p1-r1-p1-p1-r1-p1-r1-2ap; II; femur d (r2p1)-r2-2-p1-2-p1-2- 2-p1-3 v 0-p1-1-0-0; patella p 1; tibia d 2-p1-1-2-2-p1-p1-1-3 v 2-0-p1-r1-p1-2-0-2ap; metatarsus d 2-p1-2-r1-p1-r1-p1-p1-2ap v p1-r1-2-2-r1-p1-3ap; III; femur d (r3p1)-1-r1-2-p1-2-2-2-r1-3 v r1-p1-2-0-0; patella p 1 d 1 r 1; tibia d 2-1-p1-3-2-2 v 2-0-p1-r1-p1-2ap; metatarsus d 2-p1-p1-r1-p1-2- 2ap v 2-p1-p1-r1-p1-p1-r1-3ap; tarsus v 0-r1-0; IV femur d (r4p2)-r2-1-r2-p1-2-2-2-3 v 0-p1-p1-0-0-0; patella p 1 d 1; tibia d 2-2-p1-1-3-r1 v 2-0-0-p1-p1-2ap; metatarsus d 2-p1-2-r1-2ap v p1-2-p1-p1-p1-2-r1-3ap; tarsus v 0-1-0.
Single claw. Spines: femur d 0-0-1-1-3ap patella p 1 d 1-1, tibia d 1-1, p 0-2-0; tarsus d 2-2-1-2-3ap v 2-2-2ap.
Cribellum undivided, with narrow spinning field, as wide as basal span of anterior spinnerets (Figs 3E, 3I). Spiracles of posterior lung books well separated but joined by a transverse groove. Genital area swollen and only faintly sclerotized near the epigastric furrow (Fig. 3E).
Genital area distinct and dome-shaped (Figs 3A, 4A). Internal genitalia simple, with eight spermathecae grouped in two quartets (Figs 4D–E). The outer spermathecae are ovoid and have a short duct. The inner spermathecae can be grouped leading into the bursa through a long, slender convoluted duct (Fig. 4). Glandular projections are mainly present on the spermathecal ducts. A fold with two distinct sclerotized pockets is situated anterior/ventral to the spermathecae. A blind-ended invagination, the postepigastric furrow, is situated immediately posterior to the epigastric furrow.
(ZIMG II/28127; Fig. 5).
Right male palp of Progradungula otwayensis (ZIMG II/28127). A Prolateral view; the arrow marks the section plane of Fig. 5B B Section of the volume rendered male palp C Surface model of the spermophor superimposed on the volume rendering of the male palp (prolateral, ventral and retrolateral views). The cymbium, subtegulum and tegulum are partly removed in the prolateral view to show tendons, muscles and hematodochae. The arrow points to the opening of the embolus. Abbreviation: Cb cymbium; E embolus; m29 muscle 29; m30 muscle 30; mA median apophysis; mH median hematodocha; PE process of embolus; S spermophor; St subtegulum; Te tegulum; tm29 tendon of muscle 29; tm30 tendon of muscle 30.
Tegulum with short median apophysis. Embolus tube-like with a solid single hook-shaped process; tip of the embolus widened and hyaline; fundus sac-like, spermophor with an internal band delimited by two parallel ridges (Fig. 5B), distal part of the spermophor within the embolus partly convoluted and very thin (approximately 8µm in diameter); m30 and tm30 in cymbium; m29 in tibia and attaching to the spermophor.
The web structure is similar to Progradungula carraiensis (for details see
Endemic to the Great Otway National Park (Victoria). In addition to the locations reported by
Our data are in accordance with the previous detailed descriptions on the distribution and natural history of Progradungula species (
The female genitalia of Progradungula otwayensis are very similar to Progradungula carraiensis as the number of spermathecae is reduced compared to other gradungulids and they are bilaterally arranged (
As revealed by micro-CT analysis of the male palpal organ of Progradungula otwayensis, the spermophor has a thick wall and an internal band delimited by two parallel ridges, which in the micro-CT sections appears associated with glandular tissue. As described by
We are very grateful to Mike Rix (WMA, Perth, Australia) for advice regarding the localities and helpful comments on the manuscript. This study was funded by the German Science Foundation (DFG Mi 1255/5-1), CONICET (PIP 112-200801-03209) and ANPCyT (FONCyT, PICT-2007-01393). The material was collected under the permit number 10006549 (Department of Sustainability and Environment, Victoria). Mark Harvey (WMA, Perth, Australia) suggested the common name for this species.