Maratus ammophilus, Otto & Hill, 2022

Otto, Ju. rgen C. & Hill, David E., 2022, Maratus ammophilus, a new peacock spider in the Fimbriatus group from Western Australia (Araneae: Salticidae: Euophryini), Peckhamia 273 (1), pp. 1-65 : 4-31

Maratus ammophilus , new species

Type specimens. The holotype male (♂ #1), five paratype males (♂ #2-6), and two paratype females (♀ #1-2) were collected at Pumpkin Hollow on the coast north of Perth , Western Australia (30.233116°S, 115.014010°E, 7-18 FEB 2021, coll. Caleb Bartell). ♂ #1-4 and ♀ #2 were caught as juveniles and raised to adulthood, ♂ #5 and ♀ #1 were caught as adults, and ♂ #6 was raised from an egg deposited by ♀ #1 . Three paratype males (♂ #7-9) and four paratype females (♀ #3-6) were collected at nearby South Bay, Green Head (30.073353°S, 114.978204°E, 7-18 FEB 2021, coll. Caleb Bartell). ♂ #9 was caught as an adult, ♂ #7-8 and ♀ #3-6 were collected as juveniles and raised to adulthood . All types will be deposited in the Western Australian Museum , Perth . M. ammophilus has also been observed at Lake Thetis in Cervantes (30.505942°S, 115.078376°E, JUL 2018; Su Rammohan, pers. comm.), and at the beach in Kalbarri (27.703654°S, 114.167276°E, JUN 2022; Michael Lun, pers. comm.).

Etymology. The species group name, ammophilus (Latin, adjective, m.), means sand-loving, a reference to the sandy beach habitat of these spiders.

Diagnosis. The distinctive wheel-rim shape of the embolus and the use of legs I in courtship clearly place the male Maratus ammophilus in the fimbriatus group of the genus Maratus . The male resembles M. speculifer with respect to the unusual shape and yellow-green colour of femora I, with a wider proximal subsegment separated from a narrower distal subsegment by a shelf on the anterior side. However, the overall colouration of the male M. ammophilus ( Figure 1 ) is quite different, like the female almost entirely off-white. The setae of the dorsal opisthosoma of M. ammophilus are off-white and moderately iridescent, whereas the fan of the male M. speculifer bears a singular dark and glabrous, shiny scute, the basis for its species name. In addition the anterior femora I and II of M. ammophilus have a transverse black bar at the distal end of each subsegment, or at least at the end of each proximal subsegment, easily visible from the front during courtship display.

Description of male ( Figures 4-7 ). Males (n=9) ranged from 3.2-3.8 mm in length. Almost the entire body, including the ventral opisthosoma, is covered with white to off-white or light-brown setae. The face is bright white, the chelicerae mostly glabrous and dark brown. An indistinct, middorsal thoracic tract of lighter setae may be present. The sides of the carapace have a distinct marginal band of white to offwhite setae. The PME are closer to the PLE than to the ALE. The dorsal opisthosoma tends to be light brown rather than white, often with a moderate iridescence.

Legs I and II of similar length, shorter than legs III and IV, all with indistinct dark bands at the joints. Legs III are the longest. Sternum, labium and endites are dark brown to grey, almost glabrous except for longer white to off-white setae radiating from the posterior and lateral margins of the sternum. Cuticle of the prosoma and opisthosoma dark, that of the appendages almost lacking pigment. Ventral surface of each femur I and II translucent and almost glabrous, yellow-green. Each femur I and II is divided into a proximal subsegment of greater diameter, and a distal subsegment of lesser diameter, each subsegment (or at least the proximal subsegment) marked distally by a dark transverse band on the ventral surface; these subsegments are separated by a distinct, ventral shelf associated with the transverse band of the proximal subsegment ( Figure 4 :8,52). Pedipalps are light in colour, covered with long white setae. The retrolateral tibial apophysis ( RTA) is unremarkable, similar to that of other Maratus . As is the case for other members of the fimbriatus group, the embolus resembles a wheel-rim, darker along the upper and lower margins of that rim, with a distally projecting terminus that bears the apical pore.

Description of female (figures 8-10). Females (n=5) ranged from 4.0- 4.9 mm in length. Colour very much like the male, although the yellow-green colouration beneath femora I and II may be subdued and obscured by long white setae.

Most of the type females have a fairly uniform but variable cover of off-white to light brown setae on the dorsum, but one (♀ #2, Figure 8 :4-12) is much more patterned or contrasty on the dorsum, with many areas bearing darker brown setae. Variable pigmentation of the cuticle is more evident in alcohol ( Figure 10 :1-20). All females have long, bright white setae on the face, projecting anteromedially over the top of the dark brown, glabrous chelicerae. Setae covering the lower sides of the carapace are also bright white. PME closer to the PLE than to the ALE. Legs I and II are shorter and of similar length, legs III and IV longer and also of similar length. The epigynum ( Figure 10 : 25-28) is unremarkable and similar to that of other Maratus , with large fossae and posterior spermathecae of similar size.

Immatures ( Figure 11 ). Immature Maratus ammophilus , even in the first emergent (free-living) instar ( II), have a colouration similar to that of adults.

Courtship ( Figures 12-16 ). Courtship display in Maratus ammophilus , as observed under natural conditions in the laboratory, is relatively simple, with the male moving intermittently (discontinuously) from side to side in front of the female, holding each new position with legs I extended and elevated to display the prominent markings on the underside of the femora, as legs III are extended to the sides. In this position, the ornamentation under legs II is also visible to the front. During this display the white pedipalps are held in place in front of the dark and glabrous chelicerae. As shown in Figure 12 , the male tends to keep legs II in place when moving the elevated and extended legs I and III to one side or the other, and may even keep legs II and IV in place during this movement without any stepping at all. This fixed placement or stance of legs II keeps them in a position where the ventral femora II, like the ventral femora I, are readily visible from the front. When legs III are widely extended this side-to-side rocking movement also has a see-saw effect.

The extent to which the opisthosoma is raised (never to a vertical position), or legs III are extended, varies. In addition, detailed placement of legs II and IV during each stance varies according to the surface on which the male is displaying. All aspects of this display are similar to those seen in other members of the fimbriatus group, although one species, Maratus fimbriatus , does not extend legs III, but also rotates the fan with each side-to-side movement.

Mating. The erection of spines during mating by spiders corresponds to the transient increase in internal fluid pressure that occurs as seminal fluid is pumped from each pedipalp into the corresponding (same side) sperm duct of the female. This is documented for Maratus ammophilus in Figure 17 .

Habitat. Maratus ammophilus has been found on sandy ground, in coastal dunes along the Indian Ocean in Western Australia ( Figures 2 , 3 :1-2, 18-19).

Figures

Figure 1. Adult males representing species in the fimbriatus group of the genus Maratus. Photo credit: 4, © Nick Volpe, used with permission.

Figure 2. Known distribution of species in the fimbriatus group of the genus Maratus. M. fimbriatus was previously divided into two allopatric species groups, one in the interior of New South Wales (described as M. fimbriatus), and the second in the interior of Queensland (described as M. licunxini). New records of this species that have been posted and documented with reliable photographs in iNaturalist by Stuart Harris, Laurence Sanders and Wayne Winnington-Martin are included here. We have examined a specimen in the Australian Museum from the Pilbara (7) that has been identified as M.?fimbriatus and recorded in the Atlas of Living Australia, and have determined that this represents a new, undescribed species with a much smaller fringe around the opisthosoma. In some cases more than one locality is marked by one circle. The known distribution of M. ammophilus is parapatric to the closely-related M. speculifer, with both species found on sands near the Indian Ocean coast of Western Australia. Other members of the group are known only from isolated sites in the interior of South Australia.

Figure 3. Males representing two different species in the Maratus fimbriatus group, both living on sandy ground near the western coast of Australia. 1-2, Male M. ammophilus at Lake Thetis, Jurien Bay (30.505942°S, 115.078376°E). In (1) a characteristic black bar across the front of each femur I can be seen. 3-4, Undescribed male Maratus sp. at Denham Beach, Shark Bay. In this species the front of each femur I (3) resembles that of Maratus sp. B (Figure 1:5). Photo credits: 1-4, © Su Rammohan, used with permission.

Figure 4 (continued on next page). Living male types for Maratus ammophilus. 8, Note the division of the left femur I into proximal and distal subsegments, separated by a darkly-pigmented shelf on the ventral side. 9-10, Courtship display, exposing the prominent features of legs I and II.

Figure 5. Ventral views of living male types for Maratus ammophilus.

Figure 6 (continued on next page). Male types for Maratus ammophilus, in alcohol.

Figure 7 (continued from previous page, continued on next page). Medial to lateral views of the left pedipalp of male types for Maratus ammophilus, in alcohol.

Figure 8 (continued on next page). Living female types for Maratus ammophilus.

Figure 10 (continued on next page). Female types for Maratus ammophilus, in alcohol.

Figure 11. Immature Maratus ammophilus. Numbers (#) correspond to the identification numbers assigned to adults.

Figure 12. Frames from a 50 fps video of courtship by a male Maratus ammophilus, showing four sequential positions held during display. The direction of movement from the previous frame is indicated with a blue arrow. Circles identify stationary legs on which this male pivoted. Throughout this sequence, the male held legs II in position. From 3-4 the male also held legs IV in position while rocking to the side.

Figure 13 (continued on next page). Sequential frames from a 50 fps video of courtship by a male Maratus ammophilus. At times (e.g., 8-9) a male may make more than one pivot in the same direction, with legs II in place.

Figure 14. Frames from a 25 fps video of a courting male Maratus ammophilus, showing successive positions held by that male in front of a female. The time of transition from the previous position is shown in each green arrow, and the time that this spider remained in the depicted position is shown in each red rectangle. The direction of movement from the previous frame is shown with a blue arrow.

Figure 15. Frames from a 25 fps video of a courting male Maratus ammophilus, showing successive positions held by that male in front of a female. The time of transition from the previous position is shown in each green arrow, and the time that this spider remained in the depicted position is shown in each red rectangle. 18, At the end of this sequence the male reached down to touch the courted female with legs I.

Figure 16 (continued on next page). Courting positions of male Maratus ammophilus. 4, 16-17, During courtship legs III are not always extended. 5-6, At times, particularly when more distant from a female, males did not elevate the opisthosoma during this display.

Figure 17. Sequential frames from a 25 fps video showing a mating pair of Maratus ammophilus. Extension of spines (arrows in even-numbered frames corresponds to a transient increase in internal fluid pressure of the male.