The Effect of Antihistamines on the Pigments of Green Protista.

SUMMARY. A preliminary survey of the influence of a number of antihistamines on growth of several protozoa indicated that not only growth but also pigment formation in green forms was inhibited. Subsequently, it was demonstrated that molar concentrations of the drugs of less than 1 times 10⁻³ caused chlorosis of cultures of Euglena gracilis var. bacillaris, Chlamydomonas pseudococcum , and Chlorella vulgaris.
With the aid of one of the antihistamines, Pyribenzamine (CIBA), a permanently colorless culture of Euglena was obtained. This culture has been maintained in the chlorotic state in antihistamine-free medium through eighteen serial transfers in constant light. Comparative spectro-photometric studies were made of the pigments extracted from this new euglenid strain with those from normal green, dark-grown and streptomycin-bleached euglenas. Although the dark-etiolated forms retained small amounts of chlorophylls, neither of the drug-bleached cultures showed evidence of these pigments. Quantitatively, the carotenoid picture in dark-bleached and streptomycin-grown organisms was similar, but these pigments were greatly reduced in the Pyribenzamine-treated strain. Further studies on the identity of the carotenoids in the new euglenid are in progress.     

Floral traits and pollinator constancy: Foraging by native bees among three sympatric legumes

Abstract The foraging constancy of the solitary bee, Trichocolletes sp., was documented in a semi-arid ecosystem where three morphologically similar legumes co-occur. To quantify the degree of floral similarity among the forage plants, Dillwynia hispida, Dillwynia uncinata and Pultenaea densifolia, discriminant function analysis of petal dimensions and a spectral analysis of corolla colour was undertaken. Petal size varied moderately among species resulting in 2–14% of specimens being misclassified, usually as D. uncinata. Subtle variation in corolla colour in the ultraviolet wavelengths contributed to the distinctiveness of each species. All three species exhibit an UV-absorbing region at the base of the standard petal which contrasts sharply with the rest of the UV-rerlecting petal. Between 450 nm and 470 nm, per cent reflectance drops for D. hispida and P. densifolia, but remains steady for D. uncinata. Above 480 nm, parts of the standard petal in all species reflect similar amounts of light with little variation exhibited among species. Nectar was only offered by D. hispida and D. uncinata, whereas P. densifolia produced an excess of pollen which may serve as a reward. Despite the subtle differences in floral morphology and rewards among these sympatric legumes, Trichocolletes bees only remained faithful to a given species in 43% of 183 interplant flights. Inconstant foraging by Trichocolletes sp. increases the pool of resources because rewards in all three legume species can be obtained in exactly the same manner.