Maratus caeruleus Waldock 2013

Jürgen C. Otto & David E. Hill, 2014, Spiders of the mungaich group from Western Australia (Araneae: Salticidae: Euophryinae: Maratus), with one new species from Cape Arid, Peckhamia 112 (1), pp. 1-35 : 10

Maratus caeruleus Waldock 2013

Maratus caeruleus ( Figure 1 ), with a reported male body length of 7.89 mm, is perhaps one of the largest Maratus ( Waldock 2013, Fig. 25 however depicts a body length ~5 mm). It is known only from type specimens collected on the ground (22 OCT 2008), on Middle Island in the Recherche Archipelago just 15 km from the type locality of the related M. avibus ( Figure 13 ). Like the smaller M. avibus , this spider lacks a central dark figure on the dorsal opisthosoma. Shallow seas presently separate this Archipelago from the mainland, but these were elevated areas on the mainland during the last glacial maximum (LGM, ~15- 20Ka). M. caeruleus may represent a case of island gigantism (or the island rule; Lomolino 2005). Given the small size of Middle Island, a difference in selection based on community composition, as well as the rapid evolution (genetic drift) associated with a small island population ( Ellstrand and Elam 1993), may have led to a recent, rapid divergence of M. caeruleus from the mainland species M. avibus .

Figures

Figure 1. Photographs (1-3) and approximate drawings (4-6) of the extended male opisthosomal fan of species in the mungaich group of the genus Maratus. Photographs show fans of living spiders. Drawings are based on descriptions (Waldock 2013) or, in the case of M. karrie, on specimens collected by Darlington that we examined. Waldock described the iridescent scales of these spiders (blue in drawings 4-6) as 'bright blue to rose-gold' under halogen lights, and did not distinguish the appearance of living animals from specimens under alcohol. Our examination of the scales of M. karrie (Figure 14; Hill & Otto 2011), as well as photographs of the M. caeruleus holotype, suggest that the colour of the iridescent background in these drawings is similar to that shown in the photographs. Each scale bar = 1.0 mm. Scale bars associated with each photograph are based on our records. Scale bars associated with each drawing are based on the length of each respective spider in Waldock's (2013) text description and generally do not agree with the scale bars in her figures.

Figure 13. Cape Arid and Middle Island. 1, Type localities where M. avibus and M. caeruleus have been found, superimposed on an old nautical map of the southwestern coast (1802 survey published by Forrest et al. 1878). Depths are in fathoms (1 fathom = 1.822 m). Coastlines on this early survey map are only approximate. 2, View of Middle Island in the Recherche Archipelago (at right rear, in the distance) from Cape Arid. Several smaller islands nearer to the coast can also be seen. Presently Middle Island is separated from the Cape by a shallow strait.

Figure 25. Dorsal opisthosoma of a male M. sarahae (♂#5), with fan extended (1) and retracted or folded around the lateral margins (2). Numbers 1-12 identify features that are compared with corresponding features of M. mungaich in Table 2. As in M. mungaich, the fan of M. sarahae is very wide.