Maratus nubilis, Ju & Otto & Hill, 2022

Ju, Otto, rgen C. & Hill, David E., 2022, Maratus nubilis, a new peacock spider in the chrysomelas group from southwestern Australia (Araneae: Salticidae: Euophryini), Peckhamia 264 (1), pp. 1-29 : 5-28

Maratus nubilis , new species

Type specimens. The holotype male (♂ #1), three paratype males (♂ #2-4), and three paratype females (♀ #1-3) were collected in the Denmark Catchment State Forest near Perillup , Western Australia (S34.613671°, E117.178650°, 27 NOV 2021, coll. Flynn Prall and James McMulkin). All types will be deposited in the Western Australian Museum, Perth .

Etymology. The species group name, nubilis (Latin, adjective) is a reference to the obscure or beclouded appearance of the transverse bands of the dorsal opisthosomal plate or fan of the male.

Diagnosis. Detailed structure of the male pedipalp ( Figure 9 ) places M. nubilis in the Maratus chrysomelas group, but is not very different from other members of this group. However the pattern of scales and setae associated with the fan (dorsal opisthosomal plate) of the male (Figure 3:11) is quite different from that of any other Maratus .

Description of male ( Figures 5-9 ). Males (n=4) ranged from 3.3-3.7 mm in length. The cuticle of the carapace is black in living males, yellow-brown in specimens preserved in alcohol. The subsequent description pertains to the living spider. The clypeus is mostly black and glabrous, with relatively few scattered brown setae. The chelicerae are black and glabrous, with only a few scattered setae near the medial margin. Dorsally (or from the front, in a normal position), each pedipalp is banded, with the tibia and cymbium both black proximally, bearing a thick cover of off-white setae for most of their length, and black distally. Brown or orange scales (varies by individual) surround the eyes and cover both the eye region and the sides of the carapace. The PME are closer to the PLE than to the ALE. A thin white band of scales is present along the lateral margins of the carapace, but there is no mediothoracic band behind the eye region.

Stout, mostly white setae project upward and forward at the anterior margin of the opisthosoma. The fan (dorsal opisthosomal plate) is covered with alternating transverse bands comprised of either lightiridescent-blue-green or white-to-grey scales. The color saturation of the iridescent bands varies according to the angle of illumination. On either side the opisthosoma is flanked with a prominent fringe of long, proximally grey, distally white setae or plumes. When fully expanded during courtship the fan, with these plumes, is about twice as wide as the opisthosoma itself. Although a small, triangular colular tuft is present, this is grey rather than white. The spinnerets are dark grey. Below, the opisthosoma is brown in colour, densely covered with off-white setae. From below, the coxae and sternum are brown, with many scattered white to off-white setae, longer around the posterior margin of the sternum. The labrum and endites are brown and glabrous.

Legs I and II are shorter and of similar length, legs III and IV longer, legs III the longest. All of the legs are banded, mostly black to dark brown but with a band of white to off-white setae or orange setae (varies by individual) around the distal end of each segment, from the patella to the metatarsus. On legs III these off-white setae are particularly long, also present on the distal end of each tarsus, and the femora are mostly black. The detailed structure of the pedipalp is similar to that seen in other members of the chrysomelas group, with a heavier outer apex converging at the tip with an inner apex (or sclerotized inside end of the apex) of the embolus, appearing as two sides of an acute triangle ( Figure 9 ).

Description of female (Figures (10-13). Females (n=3) ranged from 3.9-4.4 mm in length. This description pertains to the living female. The carapace of the female is dark brown. The clypeus is covered with stout, long white to off-white setae, some projecting anteromedially above the anterior margin of the carapace and the chelicerae. The chelicerae are mostly glabrous and dark brown. The PME are slightly closer to the PLE than to the AME. The margins of the carapace are wide, dark brown, and glabrous. The pedipalps are light brown, with a cover of long white to off-white setae. Above the margin the carapace has a relatively uniform cover of off-white to light brown or orange setae, with a regular row of white or off-white setae just above each lateral margin. Extending behind the eye region is a mediothoracic stripe of more densely-packed setae. At the front of the dorsal opisthosomal is a group of stout, mostly white, setae projecting forward. The dorsum, and lateral sides of, the opisthosoma is irregularly mottled with alternating areas of light-brown, off-white, and dark brown setae, variable by individual. The venter of the opisthosoma is lightly mottled, mostly uniformly covered with off-white setae. A small, triangular tuft of off-white colular setae is present, above the grey spinnerets.

Legs I and II are shorter and about the same length, legs III and IV longer and about the same length. All legs are uniform in colour and banded, with bands of off-white setae toward the end of each leg segment, separated by dark brown and more glabrous bands around each joint. From below, the coxae and sternum are brown to dark brown, with scattered setae, and longer off-white setae projecting from the lateral and posterior margins of the sternum. The labium is dark brown and glabrous. The endites are lighter yellow-brown and glabrous. The epigynum ( Figure 13 ) is typical for the group, with a large posterior spermatheca behind a fossa (window) on either side, and variably sclerotised ducts visible through the posterior part of each fossa.

Immatures. An emergent (instar II, stage that emerges from the brood sac) Maratus nubilis is shown in Figure 14 . The general colouration of this instar resembles that of the female, but with little pigmentation of the cuticle (except for the eye region) and far fewer setae. Older immatures ( Figure 15 ) have distinct transverse tracts of off-white setae, or chevrons, on the dorsal opisthosoma.

Courtship display ( Figures 16-19 ). Our observations of courtship display by the male are based on video records of spiders on natural vegetation in the laboratory. When a female is sighted, a male may rear one leg and slowly wave the elevated fan over a small amplitude ( Figure 16 ; ~2 Hz left-to-right cycles, ~4° amplitude). During this display the fringe of the fan is not expanded laterally, and the male remains in place, with some movement of the pedipalps. The appears to represent a form of advertisement, or at least "hesitancy" on the part of a male that is evaluating the response of a female.

Apart from this "advertisement," we have observed a single mode of courtship display, or fan dance, of the male ( Figures 17-19 ). This display involves elevation of legs III, usually behind the fan and often flexed at the tibiometatarsal joint so that legs III are at least partly concealed behind the fan. In addition, the male may step slowly from side to side, in small increments, as the fan is waved continuously. The speed and amplitude of this dance can change dynamically. In one of the two examples charted here ( Figure 17 ), a male switched from a slower pace with smaller amplitude in place (2 Hz, 3°) to a much faster pace with a larger amplitude (7 Hz, 12°), accompanied by side-stepping. In the second example ( Figure 18 ), a male switched from a faster pace with an even higher amplitude (7 Hz, 20°) to a slower pace with a moderate amplitude (4 Hz, 11°). In addition to side-stepping, the pedipalps, held apart to expose the dark, glabrous anterior surface of the chelicerae, may also be moved ( Figure 19 ).

right waves (~2 Hz, ~4°) of the elevated, but not extended fan.

134. 5.32s 135. 5.36s 137. 5.44s 139. 5.52s 141. 5.60s 73.6° 64.4° 71.7° 56.5° 64.4° 142. 5.64s 144. 5.72s 146. 5.80s 148. 5.88s 149. 5.92s 63.2° 52.7° 46.4° 59.2° 48.1° 151. 6.00s 153. 6.08s 155. 6.16s 158. 6.28s 160. 6.36s 54.9° 54.3° 42.8° 47.8° 37.3° 161. 6.40s 163. 6.48s 165. 6.56s 167. 6.64s 169. 6.72s 34.0° 40.4° 39.8° 29.8° 27.6°

amplitude ~12° ~7 Hz

to the right

5°

2

/) amplitude ~3°

inclination ~2 Hz

0

fan

Δ

(

-5° to the left

1 2 3 4 5 6s

Figure 17 (continued from previous page). Sequential frames from a 25 fps video of the fan dance of a male Maratus nubilis . As shown in the chart, this male switched from low speed, low amplitude fan waving in place to a much faster and higher amplitude display while side-stepping.

amplitude ~20°, ~7 Hz amplitude~11°, ~4 Hz to the right 2 10° /) inclination 5° 0 fan -5° Δ (-10° to the left 1 2 3 4s Figure 18 (continued from previous page). Sequential frames from a 100 fps video of the fan dance of a male Maratus nubilis . This male switched from a faster, higher amplitude mode of display with side-stepping to a slower, lower amplitude display in place.

Habitat. Maratus nubilis was found in the Denmark Catchment State Forest in southwestern Australia, in open areas of sandy-clay soil, within a winter-wet shrubland dominated by Melaleuca ( Figure 20 ).

Figures

Figure 5 (continued on next page). Living male types for Maratus nubilis. 4-5, Note the extended fringes of the fan, and the exposed pedipalps of this male, during courtship. 6, Detail of left leg III during courtship, showing how it is often flexed to the rear at the tibiometatarsal joint.

Figure 6. Ventral view of living male types for Maratus nubilis.

Figure 7. Detailed views of the scale cover and fringes of the fan of the male types for Maratus nubilis. 1-2, Two views of the fan of living spiders. 3-4, Two views of the fan of the holotype preserved in alcohol, showing the impact of illumination on the color saturation of the iridescent scales. 5-6, Two views of the fan of a paratype, also showing the impact of illumination on color saturation.

Figure 9. Views of the male holotype for Maratus nubilis, in alcohol. 2-9, Medial to lateral views of the left pedipalp. Note how the longer, outer apex of the embolus meets a short and thin inner apex or scelotized edge of the embolus at the tip, appearing as two sides of an acute triangle (5-7).

Figure 13. Ventral view of the epigynum of female paratypes for Maratus nubilis in alcohol. The anterior direction is toward the top of the page.

Figure 14. Living emergent (instar II) Maratus nubilis.

Figure 15 (continued on next page). Living immature (instar III or IV) Maratus nubilis. Different individuals are identified by number.

Figure 16. Sequential frames from a 120 fps video of a male Maratus nubilis displaying in front of a female. This advertisement or tentative display included extension of one leg III (frames 1, 19) and slow, low amplitude left-to

Figure 17 (continued on next page). Sequential frames from a 25 fps video of the fan dance of a male Maratus nubilis.

Figure 18 (continued on next page). Sequential frames from a 100 fps video of the fan dance of a male Maratus nubilis.

Figure 19. Sequential frames from a 25 fps video of the fan dance of a male Maratus nubilis. These frames illustrate slight movements of pedipalps and the flexion of legs III to the rear, at the tibiometatarsal joint, during this dance. One or both legs III may be flexed and at least partly concealed behind the fan, as shown here.

Figure 20. Habitat of Maratus nubilis in the Denmark Catchment State Forest. Photographs © James McMulkin, used with permission.