Jotus remus Otto &amp; Hill 2016, new species
Creators: name: Otto, Jürgen C.
name: Hill, David E.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Salticidae
Jotus
Jotus remus

description: <i>Jotus remus</i>, new species <i>Type specimens</i>. The holotype male (&amp;male; #5, collected as penultimate and reared to adulthood 13 JAN 2015), four paratype males (&amp;male; #1-4), and nine paratype females (&amp;female; #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. <i>Etymology</i>. The species group name (<i>remus</i>, Latin, m., nom., English translation <i>oar</i> or <i>paddle</i>) 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. <i>Diagnosis</i>. The presence of a paddle at the end of each leg III uniquely identifies this species. Otherwise, these are very similar to other <i>Jotus</i> with respect to structure of the male and female genitalia and general appearance. Male <i>J. auripes</i> and <i>J. frosti</i> are readily distinguished from <i>J. remus</i> by the distinctive appearance of their pedipalps and legs I (Figures 2-3). Females of most <i>Jotus</i> are unknown and it is thus unclear what characters may be used to distinguish them. Compared to the female of an undescribed <i>Jotus</i> species from Barrington Tops (Figure 4: 5-6), the carapace and legs of the female <i>J. remus</i> are distinctly darker in colouration. <i>Description of male</i> (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 <i>Jotus</i>. 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 <i>Jotus</i>, 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 <i>Jotus</i> and related genera in the <i>Saitis</i> clade. <i>Description of female</i> (Figures 15-18). Female <i>Jotus remus</i> 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 <i>Jotus</i> 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. <i>Immatures</i>. When compared with emergent (second instar) <i>Maratus</i>, <i>Jotus remus</i> are relatively dark and glabrous, with proportionately longer legs (Figure 19). <i>Male display and male-female interactions</i>. 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 <i>Jotus remus</i>. then jumping to attack the paddle of a male <i>Jotus remus</i>. 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, <i>Colonus</i> (formerly <i>Thiodina</i>) 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 <i>Jotus remus</i>, however, males appear to be able to determine this lack of movement when the female is completely out of sight. A mating pair of <i>J. remus</i> 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 <i>Maratus</i>, <i>J. remus</i> males only mated with a single pedipalp during each encounter. <i>Habitat</i>. <i>Jotus remus</i> 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 (<i>Eucalyptus pauciflora</i>) and Mountain Gums (<i>Eucalyptus dalrympleana</i>). The ground cover was mostly Snow Grass (<i>Poa sieberiana</i>) and Mat Rush (<i>Lomandra</i> 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 (<i>e.g.</i>, Dudley <i>et al.</i> 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).
description: Published as part of <i>Otto, Jürgen C. &amp; 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), pp. 1-39 in Peckhamia 133 (1)</i> on pages 7-32, DOI: 10.5281/zenodo.7173033
description: {"references": ["Otto, J. 2015 a. Spid-a-boo. Online video at: https: // www. youtube. com / watch? v = HkiwPkjpYpA", "Otto, J. 2015 b. Spid-a-boo 2. Online video at: https: // www. youtube. com / watch? v = r 4 YHf 6 nBbzE", "Hill, D. E. 2012. Notes on the jumping spiders Thiodina puerpera (Hentz 1846) and Thiodina sylvana (Hentz 1846) in the southeastern United States (Araneae: Salticidae). Peckhamia 99.1: 1 - 63.", "Dudley, R., G. Byrnes, S. P. Yanoviak, B. Borrell, R. M. Brown and J. A. McGuire. 2007. Gliding and the functional origins of flight: biomechanical novelty or necessity. The Annual Review of Ecology, Evolution, and Systematics 38: 178 - 201.", "Yanoviak, S. P., M. Kaspari and R. Dudley. 2009. Gliding hexapods and the origins of insect aerial behaviour. Biology Letters, Evolutionary Biology: doi: 10.1098 / rsbl. 2009.0029"]}