Dietary canthaxanthin reduces xanthophyll uptake and red coloration in adult red-legged partridges.

Carotenoids give color to conspicuous animal signals that are often the product of sexual selection. Knowledge of the mechanisms involved in carotenoid-based signaling is critical to understanding how these traits evolve. However, these mechanisms remain only partially understood. Carotenoids are usually viewed as scarce dietary antioxidants whose allocation to ornaments may trade off against health. This trade-off would ensure its reliability as a signal of individual quality. In the case of red (keto)carotenoids, the literature suggests that some species may show constraints in their uptake. Canthaxanthin is one of the most common ketocarotenoids in red ornaments of animals. It is often commercially used as a dietary supplement to obtain redder birds (e.g. poultry). We increased the dietary canthaxanthin levels in captive red-legged partridges (Alectoris rufa). This species shows red non-feathered parts mostly pigmented by another common ketocarotenoid: astaxanthin. We studied the impact on the uptake of carotenoids and vitamins and, finally, on coloration. We also tested the potential protective effect of canthaxanthin when exposing birds to a free radical generator (diquat). Canthaxanthin did not apparently protect birds from oxidative stress, but interfered with the absorption of yellow carotenoids (lutein and zeaxanthin). Zeaxanthin is a precursor of astaxanthin in enzymatic pathways, and their levels in tissues and eggs were lower in canthaxanthin-supplied birds. This led to lower astaxanthin levels in ornaments and paler coloration. As far as we know, this is the first report of a carotenoid supplementation decreasing animal coloration. The results have implications for understanding carotenoid-based signaling evolution, but also for improving husbandry/experimental procedures.

Selection of Apis mellifera workers by the parasitic mite Varroa destructor using host cuticular hydrocarbons.

The parasitic mite, Varroa destructor, is the most important threat for apiculture in most bee-keeping areas of the world. The mite is carried to the bee brood cell, where it reproduces, by a nurse bee; therefore the selection of the bee stage by the parasite could influence its reproductive success. This study investigates the role of the cuticular hydrocarbons of the European honeybee (Apis mellifera) in host-selection by the mite. Preliminary laboratory bioassays confirmed the preference of the varroa mite for nurse bees over pollen foragers. GC-MS analysis of nurse and pollen bees revealed differences in the cuticular hydrocarbons of the two stages; in particular, it appeared that pollen bees have more (Z)-8-heptadecene than nurse bees. Laboratory experiments showed that treatment of nurse bees with 100 ng of the pure compound makes them repellent to the varroa mite. These results suggest that the mite can exploit the differences in the cuticular composition of its host for a refined selection that allows it to reach a brood cell and start reproduction. The biological activity of the alkene encourages further investigations for the development of novel control techniques based on this compound.

Effects of some botanical extracts on the midgut, integument and fat body of the cotton leaf worm, Spodoptera littoralis (Lepidoptera: Noctuidae).

Botanical extracts (8%) of four plants (Artemisia monosperma, Zygophyllum cocccineum, Lupinus termis and Brassica tournifortii) fed to the 4th larval instars of Spodoptera littoralis induced histopathological changes in the structure of the midgut, integument and fat body of the 5th instars. Zygophyllum cocci-neum and Lupinus termis induced severe damages in the midgut. The integument of treated larvae showed degeneration in the cuticle and epidermal cells which were also detached from each other. Water extracts of A. monosperma, Z. coccinieum and L. termis were the most promising in inducing shrinkage in the fat body cells and detachment of midgut muscle layers. Also, the degeneration of the midgut membrane and epithelial layer occurs in different degrees with the tested plants. This study supports the use of botanical extracts in pest control programs of lepidopterous insects.

A novel tegumental protein 31.8 kDa of Clonorchis sinensis: sequence analysis, expression, and immunolocalization.

The complementary DNA (cDNA) plasmid libraries of adult worm, metacercariae and egg of Clonorchis sinensis (C. sinensis) were constructed for researches on genomics and proteomics of C. sinensis. The full-length cDNA sequence encoding tegumental protein 31.8 kDa (CsTP31.8) was identified from the adult cDNA library. The cDNA sequence has been submitted to the GeneBank Database with accession number ABK60086. This novel cDNA sequence contains 828 bp with a putative open reading frame of 275 amino acids. The deduced amino acid sequence shows identity to membrane-associate antigens or tegumental antigens of other species. There were conserved calcium-binding EF hand and dynein light chain type 1 in the sequence. CsTP31.8 transcripts were detected in cDNA libraries of adult worm and metacercariae but not in that of egg. Recombinant CsTP31.8 was expressed and purified from Escherichia coli BL21 (DE3). CsTP31.8 was immunolocalized at the tegument of adult C. sinensis by using antirecombinant CsTP31.8 sera.