Jotus remus, Otto & Hill, 2016

Otto, Jürgen C. & Hill, David E., 2016, Males of a new species of Jotus from Australia wave a paddle-shaped lure to solicit nearby females (Araneae: Salticidae: Euophryini), Peckhamia 133 (1), pp. 1-39 : 7-32

Jotus remus , new species

Type specimens. The holotype male (♂ #5, collected as penultimate and reared to adulthood 13 JAN 2015), four paratype males (♂ #1-4), and nine paratype females (♀ #1-9) were collected at Gloucester Tops, Barrington Tops National Park in New South Wales (32.08969° S, 151.59412° E, 30 DEC 2014 - 1 JAN 2015, elevation 1159 m, coll. J. Otto). All types will be deposited in the Australian Museum, Sydney . Additional spiders were collected 1 NOV 2015 for the study of behaviour.

Etymology. The species group name ( remus, Latin , m., nom., English translation oar or paddle) is a reference to the presence of a flat 'paddle' comprised of long setae associated with the modified metatarsus and tarsus III of the adult male.

Diagnosis. The presence of a paddle at the end of each leg III uniquely identifies this species. Otherwise, these are very similar to other Jotus with respect to structure of the male and female genitalia and general appearance. Male J. auripes and J. frosti are readily distinguished from J. remus by the distinctive appearance of their pedipalps and legs I ( Figures 2-3 ). Females of most Jotus are unknown and it is thus unclear what characters may be used to distinguish them. Compared to the female of an undescribed Jotus species from Barrington Tops ( Figure 4 : 5-6), the carapace and legs of the female J. remus are distinctly darker in colouration.

Description of male ( Figures 8-14 ). These are small to medium-sized jumping spiders, 4.86-5.69 mm in body length (N=5). Chelicerae are convex, of medium size, black and glabrous, with isolated medial setae and a distinct fringe of smaller, brown setae distally, above the dark red fangs ( Figure 10 : 1). The dorsal surface of the pedipalps is dark, covered with long white to dark brown (varies by individual) setae. Setae of the dorsal patella of each pedipalp are lighter in colour, white to light brown. The height of the clypeus is about 2/3 of the AME diameter. The clypeus bears many long white setae, most projecting ventromedially. The ALE are large, 1/2 to 2/3 of the AME diameter. The AME are contiguous. All anterior eyes are fringed with small white to light brown scales or setae. Scale cover of the eye region and carapace varies greatly between individuals, from dark brown or black and glabrous, to brown or red-brown at the front. This may be the result of aging or rubbing, as males collected earlier in the season (November) had a more complete scale cover like the holotype. A median thoracic tract of white scales or setae extends from the middle of the eye-region toward the rear, ending where the carapace drops off steeply midway from the posterior eye row to the posterior margin. When the scale cover is largely intact, this tract appears to be pointed at either end, resembling a stretched diamond. There is a broad lateral band of white scales or setae on either side of the otherwise dark carapace, extending from just below the PLE (but not in front of this) toward the rear. This band is near the margin on either side, but is not marginal. The carapace is about 3/2 as long as wide.

The dorsal opisthosoma is medially dark brown to black, narrower toward the rear. This area is flanked by broad lateral bands of white to off-white scales. Below, the opisthosoma is dark brown medially, and mottled light to dark brown laterally. The anterior spinnerets ( Figure 10 : 5-7) are long, black and glabrous. The posterior spinnerets are much shorter, covered with white to brown setae. From below, the coxae, sternum, labium, and endites are black and glabrous. From below the legs are also mostly black, with scattered white to brown setae.

Legs I and II are the shortest and of similar length, mostly black but with scattered patches of white to brown setae (variable by individual), most on the dorsal femora ( Figure 10 : 3). Again, this variation may be due to aging or rubbing. The distal tarsi of legs I are light-coloured as in other Jotus . Legs III and IV are similar in length, with legs IV slightly longer ( Figure 11 : 8). The metatarsi and tarsi of legs III are specially modified in the adult male ( Figure 10 : 8-11; Figure 11 : 6, 8), with many long, off-white or light brown fringing setae on both the anterior and posterior margins forming a distinctive 'paddle'. The metatarso-tarsal joint is extremely narrowed, and the tarsus itself is somewhat flattened and of an atypical shape. The tarsi of legs I, II and IV also bear a very short fringe of stout setae ( Figure 10 : 3-5).

The male pedipalp ( Figure 13 ) is typical for Jotus , with a relatively short but heavy spiral of the embolus. The apex of the embolus is divided into two or three heavy projections. The retrolateral tibial apophysis ( RTA) is notched distally like that of other Jotus and related genera in the Saitis clade.

Description of female ( Figures 15-18 ). Female Jotus remus are somewhat larger (5.34-6.57 mm in length, N=9) and strongly resemble the males in colouration and general appearance, but lack any special modifications of legs III. The chelicerae are black, glabrous, and convex. The width of the clypeus is at lease 2/3 the diameter of the AME, and as in the male bears long white setae directed medio-ventrally. The pedipalps are black to dark brown and covered with white to off-white setae. The ALE are about half the diameter of the AME, and the AME are nearly contiguous. All anterior eyes are surrounded by light brown scales or setae. The carapace is black to dark brown with only scattered setae in the eye region, mostly around the lateral eyes. As in the male, a median thoracic tract of scales extends from the middle of the eye region toward the rear, ending at the beginning of the posterior slope of the carapace. There are also wide lateral, but not marginal, bands of white setae on the carapace. Again as in the male, these bands extend only behind the eye region, not in front of it.

The medio-dorsal opisthosoma is dark, but not as distinctly marked as the male. Laterally the margins are covered with brown to off-white setae and may be mottled somewhat. The anterior spinnerets are dark. From below the female is lighter in colour and more brown than the male, but darker in life ( Figure 16 ). Legs I and II are shorter and similar in length. Legs III and IV are longer and also similar in length. Above, the legs bear scattered groups of off-white scales, most conspicuously on the dorsal femora.

As in other Jotus species, the epigynum of the female has a prominent pair of anterior spermathecae, visible through the fossae ( Figure 18 ). These are similar in size to the posterior spermathecae.

Immatures. When compared with emergent (second instar) Maratus , Jotus remus are relatively dark and glabrous, with proportionately longer legs ( Figure 19 ).

Male display and male-female interactions. The three behaviours characteristic of male courtship display are shown in Figure 20 and may be observed in two online videos ( Otto 2015a, 2015b). These include 1) visual display in front of the female with legs I extended, 2) vibration in place on the opposite side of a leaf from the female, and 3) visual display of the paddle at the end of a leg III to a female on the opposite side of a leaf or stem.

The visual display in front of a female ( Figures 21-22 ), often at a distance, was not elaborate. This simplicity corresponds to the lack of ornamentation. When performing this display the male stood in an erect posture with the white-tipped legs I held erect and waved slightly.

The vibration display ( Figures 23-24 ) was generally performed when the female was on the opposite side of a leaf or stem, out of sight of the male. This display involved rapid bilateral movement of the flexed legs I, with the tarsi near the mid-line, up and down. At the same time the opisthosoma was bobbed up and down rapidly. The cadence of this leg movement was distinctive, often repeated at a rate of ~6/s, with intermittent acceleration to twice this rate (~12/s). This display was often interrupted as the male would reach over the edge of the leaf to display one of his paddles to the female.

Until we observed the behaviour of males in the presence of females, we could not understand how the paddle could be effective in visual display since it is flattened dorso-ventrally and thus would not be visible to a female in front of a male. In fact, this paddle is not used in face-to-face display by males, but is only used to attract the attention of a female on the opposite side of a leaf or stem ( Figures 25-30 ). The extended paddle is moved forward and backward in front of a female, and females turn to watch the paddle and frequently attack it ( Figure 30 ).

paddle of a male Jotus remus .

then jumping to attack the paddle of a male Jotus remus .

Females that continued to stalk and to attack the male paddle when it was displayed may have mated previously, but the males tended to be persistent and to continue this display nonetheless. Males were extremely skilled at evading the attacks of females and the nature of the paddle, comprised of long, soft scales, may make this difficult for the female to grasp. In many hours of observation of these male-female interactions not a single instance in which the male became injured or was caught was observed. Males appeared to have an uncanny awareness of the relative position and movement of females, even when out of sight. On the four occasions where mating was observed the female that was courted was a virgin and did not attack the paddle, but eventually stopped moving in response to movement of the paddle. The male then performed two very rapid and vigorous paddle strokes, the second approximately 0.6 s after the first. Approximately O.6 s after the second stroke he dashed to join the female on the opposite side of the leaf and immediately mated with her. The entire procedure from the first vigorous paddle stroke to mounting the female for mating was extremely rapid, completed in just over 1.2 s ( Figures 31-33 ). This procedure was followed on all four occasions. This double wave may be a signal to the female to indicate the intent of the approaching male, but it could also be a final and more extreme test of the receptivity of the female as indicated by her immobility. It should be noted that many other male salticids use the lack of movement or turning by a female as an indicator of receptivity. For example, Colonus (formerly Thiodina ) males move from side to side in front of females, approaching only when the female stops turning to face them ( Hill 2012). In the case of Jotus remus , however, males appear to be able to determine this lack of movement when the female is completely out of sight.

A mating pair of J. remus is shown in Figure 34 . When mating, males tend to hold the female securely with their rear legs, wrapping one paddle around the carapace near the face of the female. Unlike other salticids such as Maratus , J. remus males only mated with a single pedipalp during each encounter.

Habitat. Jotus remus were found on an exposed, higher elevation plateau at Gloucester Tops in Barrington Tops National Park, New South Wales ( Figure 35 ). The major tree species in this area were Snow Gums ( Eucalyptus pauciflora ) and Mountain Gums ( Eucalyptus dalrympleana ). The ground cover was mostly Snow Grass ( Poa sieberiana ) and Mat Rush ( Lomandra sp. ). As legs III are extended during flight (Figure 36) there is a possibility that the paddles of the male allow these spiders to glide or parachute as they jump down from trees as has been found in a number of insects (e.g., Dudley et al. 2007, Yanoviak 2009). This could be effective at the higher velocities associated with a free fall, but appears to have little effect on normal jumps by these spiders ( Figure 37 ). The paddles could also assist the males by improving their ability to secure a foothold or quickly flip to the underside of a leaf at the end of a jump (Figure 36: 2).

Figures

Figure 2. Adult male Jotus auripes from Sydney. As viewed from above this type species for the genus Jotus is quite unremarkable and typical of males of this genus. From the front, however, the long iridescent setae of the pedipalps and the bright red-orange setae that cover the femora of legs I and II are distinctive. The female J. auripes is known but has not been formally described (Otto & Hill 2012a, 2012b).

Figure 3. Adult Jotus frosti males photographed on Kangaroo Island, South Australia, by Jürgen C. Otto (28 OCT 2015). This impressive species is readily identified by the transverse band of white setae across the front of each pedipalp, the dark iridescent anterior femur I (2), and the combination of long black setae above and long white setae below each femur I.

Figure 4. Undescribed Jotus male (1-4) and a Jotus (conspecific?) female (5-6) photographed at Barrington Tops National Park, New South Wales, by Jürgen C. Otto (1 NOV 2015). This male has a prominent black brush beneath tibia I, but no special ornamentaion of the pedipalps. The pattern of scales on the carapace and opisthosoma is close to that of J. frosti and J. remus.

Figure 8. The five male types for Jotus remus. The holotype (♂ #5) was lighter with a heavier cover of scales and setae. This may be due to the recent molt of this spider. A broad lateral band extends only from the rear of the eye region to the rear in this species. Other than a general appearance quite similar to that of other Jotus, the prominent prolateral to retrolateral paddle associated with modifications of the metatarsus and tarsus of legs III is distinctive for this unusual species.

Figure 9. More views of the male holotype Jotus remus.

Figure 10. Details of living male Jotus remus. 1, Above the dark red-orange fangs can be seen fringes of brown setae projecting from each distal paturon. 2, Eye region of holotype male, covered with off-white to red-brown setae. 3, Right legs I- III. Note the light colour of tarsus I and the fringes of short but stout off-white setae associated with the tarsi of legs I and II. 4, Tarsus IV also has anterior and posterior fringes of stout, off-white setae. Note the erect spines associated with an increase of internal hydrostatic pressure as this spider prepared for a jump. Normally (5) these are not erect. 5-7, The anterior spinnerets are black and glabrous, usually covered by the setose posterior pair (6). Note the release of a dragline from an anterior spinneret (7). 8-11, Views of the distal right (8-9, 11) and left (10) leg III. Prominent anterior and posterior fringes form a paddle-like structure. The articulation of the metatarsus and tarsus is very narrow, and the tarsus is flattened somewhat.

Figure 11. Views of the holotype male Jotus remus in ethanol.

Figure 12. Two paratype male Jotus remus in ethanol.

Figure 13. Views of the left pedipalp of four male Jotus remus types in ethanol.

Figure 14. Underside of the living male holotype Jotus remus.

Figure 15. Views of living female Jotus remus.

Figure 16. Views of the underside of three living female Jotus remus. From below, these spiders are brown to dark brown with a more or less distinct 'U' shaped mark under the opisthosoma (1-2). This may be obscured in darker individuals (3).

Figure 17. Views of four female paratype Jotus remus in ethanol.

Figure 18. Epigyna of the nine female paratype Jotus remus in ethanol. The anterior direction is toward the top of the page. The anterior spermathecae are about the same size as the posteror spermathecae and are visible through the fossae. The septum between the fossae is generally wide.

Figure 19. Emergent (second instar) young of Jotus remus (1-6), Maratus personatus (7-9), M. pardus (10), and M. volans (11- 12). 7-12, After Otto & Hill (2014, 2015). Maratus juveniles are much more compact.

Figure 20. Behaviours associated with the courtship display of male Jotus remus (sequential but not consecutive frames from a 25 FPS video). 1, The male displayed directly in front of the female at a distance, with legs I elevated and extended. 2-5, With the female on the underside of a leaf, the male vibrated in place by moving legs I up and down rapidly while bobbing the opisthosoma. 6-7, The male waved one extended leg where the paddle could be observed by the female beneath the leaf.

Figure 21. Three sequences showing the visual courtship display of male Jotus remus in front of a female (sequential but not consecutive frames from a 25 FPS video). Subtle movement of legs I and side-to-side movement of the body relative to the previous frame is highlighted with arrows.

Figure 22. Photographs showing the visual courtship display of male Jotus remus in front of a female. 2, The female (at left) watched the male.

Figure 23. Consecutive frames (25 FPS video) showing the vibration display of a male Jotus remus on top of a leaf. The female was directly below this leaf. Arrows indicate the relative position of legs I in each frame (up or down). At times the ~6/s cadence of this display doubled to ~12/s (15-20).

Figure 24. Sequential frames (25 FPS video, not consecutive) showing alternation between paddle and vibration display by a male Jotus remus on top of a leaf. The female can be seen in outline below this leaf. 1-3, 12-14, Display of the paddle by extending it over the edge of the leaf. 4-11, 15, Vibration display. Arrows indicate position of legs I

Figure 25. Sequential frames (25 FPS video, not consecutive) showing display of the paddle of one leg III by a male Jotus remus. Note the attention of the female on top of the leaf. At times (5) this display was interrupted and the female turned away.

Figure 26. Photographs of display by a male Jotus remus. 1, Male on opposite side of a leaf from a female. In this position males engaged in vibration display. 2, Male displaying paddle to female beneath a leaf. 3, Male displaying to a female on top of a leaf. 4-6, 7-10, 11-14, Three sequences of paddle display by males.

Figure 27. Sequential frames (25 FPS video, not consecutive) showing display of the paddle by a male Jotus remus. 2-6, Here both paddles were displayed at the same time.

Figure 28. Sequential frames (25 FPS video, not consecutive) showing intermittent display of the paddle by a male Jotus remus. Note the attention of the female to the paddle when it was displayed. Paddle display alternated with vibration (3, 7-8).

Figure 29. Sequential frames (25 FPS video, not consecutive) showing a female turning to face the

Figure 30. Sequential frames (25 FPS video, not consecutive) showing a female approaching and

Figure 31. Sequential frames (25 FPS video, not consecutive) showing a male Jotus remus making a first (1-4) and then a second (5-9) rapid swing of a paddle in front of a female on the opposite side of a leaf, then quickly flipping to the top of the leaf (10-11) to mount that female (12-16). White arrows indicate the position of the paddle during each rapid swing.

Figure 32. Sequential frames (25 FPS video, not consecutive) showing a male Jotus remus raising one paddle (1-2), quickly moving the paddle forward (3), moving the paddle more slowly through a series of increments to the rear in view of a female beneath the leaf (4-9), vibrating (11-12), making one rapid swing of the paddle (13-14), vibrating (15-18), making a second rapid swing of the paddle (19-21), vibrating (22-26), and finally quickly dashing beneath the leaf to mate with the female (27-30). As also shown in Figure 32, the two rapid swings of the paddle were completed in about half a second.

Figure 33. Sequential frames (25 FPS, not consecutive) showing a female Jotus remus on top of a leaf turning to follow the rapid forward and slower rearward movement of the male's paddle (1-10). With the female watching the male raised one paddle (11) to complete a rapid swing in front of the female (12-13), briefly vibrated (14-16), completed a second rapid swing of the paddle (17-18), vibrated (19-20), and finally flipped quickly around to the top of the leaf to join the female (21-24). Both rapid swings of the paddle were completed in little more than half of a second.

Figure 34. Photos showing two (1-3, 4-6) mating sequences of Jotus remus.

Figure 35 (continued on next page). Habitat of Jotus remus at Gloucester Tops.

Figure 37. Selected composite images showing successive positions of a jumping male Jotus remus (1000 FPS video). The position of the pedicel was plotted with small circles a 1 msec intervals, superimposed on a grid of 1 mm squares (1 mm/msec corresponds to 100 cm/s). The take-off velocity (at position 7 at right side of grid) shown here was ~79 cm/s in a direction of 18.4° above horizontal (horizontal velocity ~75 cm/s, vertical velocity ~25 cm/s). The red line represents a ballistic flight trajectory from the take-off position, and the actual flight path (small circles) approximates this. Like other jumping spiders, Jotus use their dragline during these targeted jumps. Note the reversal of pitch (backward to forward) at the end of this jump.