Maratus fimbriatus, Otto & Hill, 2016

Otto, Jürgen C. & Hill, David E., 2016, Maratus fimbriatus, a new peacock spider from the Darling Riverine Plains of New South Wales, with a review of the Maratus chrysomelas group (Araneae: Salticidae: Euophryini), Peckhamia 136 (1), pp. 1-24 : 1-14

Maratus fimbriatus , new species

Type specimens. The holotype male (♂ #1), one paratype male (♂ #2), and two paratype females (♀ #1- 2) were collected near Nyngan , New South Wales (31.68110 °S, 147.41246 °E, 22 SEP 2013, coll. J. Otto). These will be deposited in the Australian Museum, Sydney . Additional specimens (24♂, 5♀) in the collection of the Australian Museum were also examined ( Table 1, below).

Etymology. The species group name ( fimbriatus, Latin , m., adjective, English translation fringed) refers to the presence of a prominent fringe of long setae encircling the opisthosoma of the adult male.

Diagnosis. The decoration of legs I and the opisthosoma of males is unlike that of any other known Maratus species. The dorsal opisthosoma is encircled by a prominent fringe, and bears two bold white longitudinal lines in front, with the black, glabrous dorsal plate (scute) exposed to the rear. The inner and outer rings of the embolus of the male pedipalp are fused and shaped like a wheel rim, not typical of Maratus , and the posterior spermathecae of the female epigynum are relatively small and joined anteriorly by prominent sclerotized ducts also not seen in most Maratus .

Description of male ( Figures 1 -5). Males (N=26) ranged from 3.8 to 4.3 mm in length. This includes the two type males and 24 males in the collection of the Australian Museum ( Table 1).

The carapace is dark brown to black in life, fading to a lighter yellow-brown on the sides in preserved specimens. Except for the margins, the carapace, including the clypeus, bears an incomplete and variable covering of off-white setae with more prominent off-white stripes extending to the rear behind the lateral eye row on either side. As in other Maratus , one or more stout setae may project forward at the median between the AME. Red-brown setae are scattered along the margins of the eye region. An indistinct middorsal tract of off-white setae may extend to the rear behind the eye region, or it may be lacking. The margins of the carapace, the proximal segments of the pedipalps, and the chelicerae are all dark brown to black and glabrous. The eyes do not have the blue or green colouration found in many other Maratus . The ALE are about 4/7 the diameter of the AME, separated from them by less than 1/5 the diameter of an AME. The small PME are nearly equidistant between the ALE and the PLE.

The anterior 2/3 of the dorsal plate of the opisthosoma is covered with a circular area of black scales, interrupted by two longitudinal white stripes (parens) that may converge toward the front or rear of the circular area ( Figure 2 ). Behind this the dorsal plate is exposed, black, glabrous, and very shiny. Laterally the dorsal plate is flanked by a thick fringe of long, curved, bicoloured setae on either side. These appear bright white when folded against the opisthosoma where only the distal part of each seta is exposed, but project a brilliant blue, iridescent colour toward the front when the opisthosoma is flattened and these fringes are extended to expose the coloured, proximal part of each seta ( Figure 1 :12). From the rear, the proximal portion of each fringing setae is dark brown and not iridescent. The lateral fringes come together at an acute angle (point) toward the rear when retracted. The underside of the opisthosoma is covered with off-white setae but may bear a circular area of brown setae toward the rear, and the brown covers of the book lungs are exposed. The spinnerets are relatively small, brown, and unremarkable. The coxae and trochanters of all legs are dark with a cover of off-white setae. The sternum is dark brown to black with off-white setae around the margins. Like the chelicerae, the labium and proximal segments of the pedipalps including the endites are dark brown to black and glabrous.

Legs I and II are about the same length, much shorter than legs III and IV. Legs III and IV are about the same length. All legs are indistinctly marked and covered with off-white to light-brown setae, with more white on the dorsal femora. Legs I have special markings used in display, however, to include glabrous yellow-brown to brown surfaces of the anterior femora, with all segments distal to the femora dark brown on the underside with few setae.

As viewed from below (Figure 5) the pedipalps resemble those of other Maratus . Two rings of the embolus are prominent and appear fused, with no separation evident. The inner or lower ring has a smooth or rounded surface and the outer ring is flattened, with a sharp outer edge. Together, the two fused rings of the embolus have the appearance of a wheel rim. The long, bright white setae of each dorsal tibia and cymbium resembles a 'pom pom', offset by the dark, glabrous proximal segments of each pedipalp. These figure prominently in the male display.

the opisthosoma are dark. Note the dark, glabrous proximal segments of the pedipalps (1).

Description of female ( Figures 6-7 ). The two paratype females and five females from the collection of the Australian Museum (N=7) ranged from 3.6 to 4.9 mm in length.

The body, legs, and pedipalps of females are covered with a 'salt and pepper' pattern of light to dark brown setae with many light or dark brown spots ( Figure 6 ). Many long white setae project anteromedially from the clypeus. As in other Maratus , one to several small, stout setae may extend toward the front from the median of the clypeus, just below the AME. The sides of the carapace bear a covering of long off-white setae, but, as in the male, there is no marginal band but instead a broad, brown, glabrous area. The chelicerae are also brown and glabrous. The ALE are about 1/2 the diameter of the AME. The small PME are almost equidistant from the ALE and the PLE.

The anterodorsal midline of the opisthosoma bears a black figure in the shape of a double-headed arrow, and behind this is an off-white or light-brown triangular spot on either side ( Figure 6 :9). The ventral opisthosoma and ventral femora are covered with off-white setae. The spinnerets are relatively small and brown. The underside of more distal leg segments are more glabrous and brown. The sternum is brown and glabrous but fringed with off-white setae as in the male. Legs I and II are nearly equal in length, much shorter than legs III and IV which are also nearly equal in length.

The paired 'windows' (fenestrae or fossae) of the epigynum are large as is typical in this group of spiders ( Figure 7 ). The paired posterior spermathecae are prominent but relatively small, somewhat separated from the fenestrae. Prominent ducts of varying degree of sclerotization can be seen anterior to the posterior spermathecae.

Courtship display ( Figures 8-14 ). A video of this display is available for viewing online ( Otto 2016). With respect to the lateral expansion of the opisthosoma including a wide fringe of encircling setae, and the relative simplicity of the display, the male Maratus fimbriatus resembles the two species of the chrysomelas group (see below). When males present themselves to females, they raise and flatten their opisthosoma, and expand the opisthosomal fringes. When partly expanded, these fringes extend toward the front. When fully expanded, the fringes form a broad band of iridescent light blue encircling the dorsal plate ( Figures 13-14 ). However, M. fimbriatus is unique among the known Maratus with respect to its use of legs I rather than legs III when displaying to a female at a distance. Although the use of legs I is common in other Salticidae (e.g., Hill 2014), the only instance in which we have observed the use of these legs in the display of Maratus involved the male-male combats or agonistic encounters of M. vespertilio ( Otto & Hill 2012a) . As in other Maratus , legs I of M. fimbriatus males are relatively short, although they are ornamented and appear dark from the front. In laboratory observations females tended to actively stalk or jump at courting males with their own legs I extended ( Figures 8-10 ). It is possible that this kind of aggressive behaviour by the females is a normal feature of male-female encounters, and that the extended legs I also serve to protect males.

The observed fan dance of male M. fimbriatus in front of a female was relatively simple, involving slight side-to-side movement of the fan as the male stepped from side-to-side ( Figure 11 ), with legs I extended and pedipalps raised together in front of the chelicerae. Directly in front of an attentive female, the male stopped stepping and cyclic movement of the fan from side-to-side (~2/s) was greater, with limited movement of the pedipalps and legs I ( Figure 12 ).

Habitat and distribution ( Figures 15-16 , Table 1). The types for Maratus fimbriatus were collected in an open semi-arid riverine plain woodland near Nyngan. All individuals were found on patches of cracked clay surface ( Figure 15 :4). Additional specimens from the collection of the Australian Museum that were examined were collected from areas to the north which belong to the same bioregion, commonly referred to as the Darling Riverine Plains ( NSW 2016a, 2016b).

Figures

Figure 1. Views of holotype (1-6) and paratype (7-12) male Maratus fimbriatus. When retracted, the fringes join to form a sharp white tip at the end of the opisthosoma (10). When expanded during courtship display (11, 12), the light blue, iridescent colour of these fringes is revealed to the female.

Figure 2. Dorsal opisthosoma of 15 male Maratus fimbriatus from the collection of the Australian Museum, Sydney. The catalog number of each specimen is shown at the upper right of each photograph (Table 1). The width and distance between the two white stripes varies. In some specimens these stripes converge to either the front (e.g., 11) or the rear (e.g., 14); in other examples (e.g., 1) they are nearly parallel. In most cases (e.g., 13, arrows) a fine posterior-lateral notch interrupts each stripe. This feature may also be observed in the male types (Figure 1).

Figure 6. Views of the two female types (1-8, 9-13) for Maratus fimbriatus. These have a fairly uniform 'salt and pepper' colouration. On the anterodorsal midline is a black figure in the shape of a two-headed arrow, and behind this on either side is a lighter coloured triangular spot (9). These may assist in the field identification of this species.

Figure 7. Views of female Maratus fimbriatus in ethanol. The epigynum is figured for two female specimens from the Australian Museum (8, 9), as well as the two paratype females (10-12). The smaller pair of posterior spermathecae in each example is somewhat separate from the large anterior (toward the top as shown here) 'windows' (fenestrae or fossae) of the epigynum. Prominent ducts of variable sclerotization proceed toward the anterior from these spermathecae.

Figure 8. Three sequential photographs showing a male Maratus fimbriatus moving from side to side and approaching an attentive female (out of focus, at left). This and subsequent videos and photographs of male-female interaction were recorded in the laboratory in a naturalistic setting.

Figure 9. Frames from video (25 fps) recordings of male-female interaction in Maratus fimbriatus. 1-3, Sequential frames showing a female raise her legs I during a male approach (2), and then return to a less defensive position as the male backed off (3). Subsequently this female jumped at the male. 4, This female (at left) also watched and then jumped at the male.

Figure 10. Sequential photographs showing a male (upper left) eliciting the attention of a female Maratus fimbriatus that subsequently (3) prepared to jump at him.

Figure 11. Display by a male M. fimbriatus while side-stepping in front of a female (sequential 25 fps video). Arrows indicate direction of stepping, movement of the fan, and (15-17) limited movement of the pedipalps relative to the previous frame.

Figure 12. Display by a stationary (not stepping) male M. fimbriatus directly in front of a female (sequential 25 fps video). The fan was rotated from side-to-side (~2/s cycles), and the pedipalps were alternately moved apart and then brought together.

Figure 13. Photographs of courtship display by the holotype (1-3) and paratype (4-9) male Maratus fimbriatus. 7-8, Note the distinct separation of the 'pom pom' distal pedipalps from the dark, glabrous proximal pedipalps and chelicerae. The anterior surface of femora I is glabrous and light brown or dark olive in colour dorsally.

Figure 14. More photographs of courtship display by the paratype (♂ #2) male Maratus fimbriatus. 1-3, From the side, the anterior orientation of the partly extended fringe can be seen clearly. 8-9, In nature, reflections off of the shiny black posterior portion of the dorsal plate may appear as a very bright pair of vertical lines, contributing to the visual effect of the vertical white stripes of the fan.

Figure 15. Views of the type locality near Nyngan, New South Wales, featuring a riverine plain woodland (NSW 2016c).

Figure 16. Distribution of Maratus fimbriatus in New South Wales. 2, Detail of inset in (1). See Table 1 for description of numbered localities. Background images courtesy of the NASA Visible Earth project.