Maratus chrysomelas (Simon, 1909)

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 : 16-24

The chrysomelas group of the genus Maratus

The chrysomelas group is a clade that presently includes two closely related species, M. chrysomelas ( Simon 1909) and M. nigromaculatus ( Keyserling 1883) . Based on his examination of male pedipalps, Żabka (1987) first recognized this close relationship. M. chrysomelas has been more recently redescribed by Waldock (2002), who included the first description of the female, and we have also published photographs of this relatively well-known species ( Otto & Hill 2012b, 2012c). M. chrysomelas is widely distributed in Australia and is known from many localities where it has been captured, for the most part, in wet pit-fall traps ( Waldock 2002). M. nigromaculatus is less known and apparently restricted in distribution to coastal areas of Queensland. Curiously, the male specimen of M. nigromaculatus examined by Żabka was missing its opisthosoma, the most distinctive feature of this species. The female of M. nigromaculatus has not been described. Fortunately, Keyserling (1883) supplied a very good drawing of the male, and we have subsequently identified and documented this species from photographs taken in Wynnum, Brisbane ( Otto & Hill 2012b, 2012c).

In addition to similarities in the detailed structure of their pedipalps, male M . chrysomelas and M. nigromaculatus share many other features ( Figures 17-18 ). The long legs III of both species are very similar, dark brown with bright white setae covering the metatarsi and tarsi. The white setae of the metatarsi III are clearly separated from those of the tarsi III by a dark ring . The pedipalps of both are covered with bright white setae, and are held laterally (and moved little) to expose the dark, glabrous chelicerae during display . Both raise and flatten their opisthosoma and extend fringes of long setae as they display . The dorsal plate of the opisthosoma of both species is covered with bright iridescent scales interupted by two dark longitudinal bands, mostly continuous in M . chrysomelas but appearing as a line of dark spots in M. nigromaculatus (hence the name). In Emerald , Queensland, there is a population that appears to represent M. chrysomelas , but includes a variety of male forms in which these bands vary from continuous as in typical M. chrysomelas to interrupted or spotted as in M. nigromaculatus ( Figure 19 ). Since this population is located near the range of M. nigromaculatus on the Queensland coast, we suspect that these forms represent gene introgression from that species into a local population of M. chrysomelas . Courtship behaviour of the two species is shown in Figures 20-23 .

Although we have few observations of the display of M. chrysomelas ( Figure 20 ), this appears to be similar to that of M. nigromaculatus , and relatively simple. In both species the pedipalps are generally separated and held in position to expose the chelicerae. The legs III tend to be held in a fairly constant v-shaped configuration, with some bilateral waving. When moving from side-to-side in front of a female, the fan of both species is also rotated slightly from side-to-side. More significant rotation of the fan of M. nigromaculatus has been observed when a male was in a stationary position close to a female ( Figure 23 ). In many respects the simplicity of this display, and the movement of the colourfully fringed fan, resemble the display of male M. fimbriatus . The decoration and use of legs III rather than legs I, and continuous separation of the pedipalps during display by males of the chrysomelas group is, however, quite different.

Figures

Figure 17. Courtship display by two male Maratus chrysomelas from Western Australia. The opisthosoma of the male from Cape Le Grand near Esperance (5-7) on the southwestern coast was wider than that of the male from Warwick Open Reserve near Perth (1-4; 31.837 S, 115.8163 E). Note the expansion of the elevated and flattened opisthosoma to reveal a fringe that is much narrower than that of male M. nigromaculatus (Figure 18). As in the latter species, the bright white pedipalps were held apart to reveal the dark, glabrous chelicerae during display.

Figure 18. Four different male Maratus nigromaculatus (1, 2-4, 5, 6-7), recently rediscovered in the vicinity of Brisbane. Keyserling (1883) also described this spider from 'Rockhampton', but no other localities are known. The spiders shown here (and in Figures 21-23) were either collected at Nudgee Beach Reserve in Brisbane, or reared from eggs produced by females collected at that site. This appears to be a coastal species, living amongst grass or pig face plants (Carpobrotus) along the borders of estuaries.

Figure 19. Fourteen different male Maratus photographed in their natural habitat, a grassy patch in Emerald, Queensland. Several males in this group (1-2) look like typical M. chrysomelas, while others exhibit the wider fringes and dark spots or (at the posterior) dashes on the dorsal plate characteristic of M. nigromaculatus, or something intermediate between the two species. This may represent gene introgression from that closely-related species into a nearby population of M. chrysomelas. Photographs copyright © Laurence Sanders, used with permission.

Figure 20. Courtship display by a male M. chrysomelas from Cape Le Grand near Esperance, WA. Selected, sequential frames from a 25 fps video are shown. Movement of the legs (bilateral waving) and pedipalps (raising and lowering), limited rotation of the elevated fan, and side-stepping are highlighted with arrows. There was little independent movement of the fan.

Figure 21. Composite images showing sequential positions (1-19, selected from 25 fps video frames) of a male M. nigromaculatus running rapidly from one side to the other of a female that he was facing.

Figure 22. Male M. nigromaculatus displaying as it stepped from side to side directly in front of a female. This sequence (1- 20) includes selected sequential frames from a 25 fps video. Arrows indicate the moderate rotation of the opisthosoma and bilateral waving of legs I that accompanied this rapid stepping movement (also indicated by arrows). As with M. chrysomelas (Figure 20), pedipalps were held to the sides of the chelicerae and moved little during this display.

Figure 23. Male M. nigromaculatus displaying in place directly in front of a female at a distance of ~1 cm. Consecutive frames from a 25 fps video are shown. Some bilateral waving of legs I (5-6), and very limited up and down movement of the pedipalps (38) can be seen. The main movement was side-to-side rotation of the elevated and expanded fan cycling at a rate of ~2/s.