Vision in the peafowl (Aves : Pavo cristatus)

The visual sense of the Indian blue-shouldered peafowl Pavo cristatus was investigated with respect to the spectral absorption characteristics of the retinal photoreceptors, the spectral transmittance of the ocular media and the topographic distribution of cells in the retinal ganglion cell layer. Microspectrophotometry revealed a single class of rod, four spectrally distinct types of single cone and a single class of double cone. In the case of the single cone types, which contained visual pigments with wavelengths of maximum absorbance (lambda(max)) at 424, 458, 505 and 567 nm, spectral filtering by the ocular media and the different cone oil droplets with which each visual pigment is associated gives predicted peak spectral sensitivities of 432, 477, 537 and 605 nm, respectively. Topographic analysis of retinal ganglion cell distribution revealed a large central area of increased cell density (at peak, 35,609 cells mm(-2)) with a poorly defined visual streak extending nasally. The peafowl has a calculated maximum spatial resolution (visual acuity) in the lateral visual field of 20.6 cycles degrees(-1). These properties of the peafowl eye are discussed with respect to its visual ecology and are compared with those of other closely related species.

Late Devonian acanthodians from Colombia

Acanthodian remains occur in micaceous siltstone lenses (presumed to have been deposited during a marine incursion) in the Cuche Formation (?Frasnian) of northeast Colombia. The acanthodians are represented by patches of scales from climatiidid Nostolepis sp. cf. N. gatijensis and a fin spine and scales from a new diplacanthid. Type material of N. gaujensis is from the Frasnian Sventoji regional stage in the Baltic, and Nostolepis sp. cf. N. gaujensis has been recorded in the Frasnian of Iran, as well as from Colombia. The new diplacanthid taxon shows affinity to Baltic and Antarctic diplacanthids. The fauna thus shows possible links to both Gondwanan and Euramerican acanthodian assemblages. (C) 2003 Elsevier Science Ltd. All rights reserved.