The retinae of Ewyattus bleekeri, an aberrant salticid spider from Queensland

Abstract

The retinal ultrastructure of an aberrant salticid spider, Euryattus bleekeri (Doleschall, 1859) is described, and discussed in the context of a model of the evolution of the Salticidae previously proposed by Jackson & Blest (1982a). The evolutionary model suggested that the Salticidae are derived from web‐building ancestors that acquired the strategy of invading the webs of other species and families of spiders; it predicts that the evolution of the principal eyes preceded that of the accessory eyes, and that traces of this sequence of events should be observable in contemporary forms. Euryattus exhibits an unusual pattern of web‐dependency (Jackson, 1985). The principal eyes conform to those of ‘advanced’ Salticidae, but the anterior lateral eyes exhibit two features associated, so far, with the primitive Spartaeinae: transverse sections of the rhabdoms present rectangular (rather than circular) profiles, and the non‐pigmented glial cytoplasm is depleted of microtubules. These findings marginally support a case for Euryattus having primitive affinities, but their import is ambiguous, and the evidence cannot be regarded as conclusive. Possible affinities between the Gnaphosidae and Salticidae based upon common tactics of web‐invasion are qualified by a comment on the retinae of the two families.