Quantifying maternal and dietary sources of 2,2′,4,4′,5,5′‐hexachlorobiphenyl deposited in eggs of the ring dove (Streptopelia risoria)

Abstract

The influence of maternal versus dietary sources of polychlorinated biphenyls (PCBs) deposited to eggs of ring doves (Streptopelia risoria) was investigated. Mature birds that lay a clutch of two eggs every 12 to 15 d were fed a diet of pellets spiked with 2,2',4,4',5,5'-hexacholorobiphenyl (unlabelled isotope designated as [12C]PCB153) for 25 d. The birds were subsequently switched to a diet containing isotopically labeled [U-13C12]PCB153 at similar concentrations for an additional 63 d. The toxicokinetics of [12C]PCB153 and [13C]PCB153 were followed in egg and carcass samples with time. Isotopic ratios of PCB153 in yolk lipids were identical to those in carcass lipids after introduction of diet 2, and they did not resemble those of the food at the time of egg formation. The data indicate that the PCB composition of eggs directly reflects the composition of maternal tissues, not the diet, at the time of yolk formation. Egg yolk:carcass lipid concentration ratios for the two isotopes were significantly less than one, averaging 0.33+/-0.02 (mean +/- standard error). Lipid normalized egg:maternal tissue contaminant concentration ratios for persistent organochlorine chemicals in the literature were reviewed for other avian species. The results provide a preliminary data set that suggests egg:maternal tissue contaminant concentration ratios vary among species, particularly among species that invest different quantities of lipids to a clutch of eggs. The results support the hypothesis that dilution of contaminants in egg lipids relative to maternal lipids is related to the reproductive strategy employed by the species.

Individual variation in body burden, lipid status, and reproductive investment is related to maternal transfer of a brominated diphenyl ether (BDE‐99) to eggs in the zebra finch

“…Overall, our data suggest that the maternal transfer of BDE-99 is at least partially through a saturable transport process, rather than exclusively passive diffusion. It has also been suggested that the extent of egg contaminant dilution is related to reproductive investment [4], and birds that invest low quantities of maternal lipids in eggs will have ratios less than 1, whereas birds that invest large quantities of maternal lipids in eggs and use more endogenous sources of lipid for yolk formation will have ratios closer to 1 [4,29]. However in the present study, reproductive investment (clutch mass) was the same across dose groups, yet we still observed differences in the egg:mother contaminant ratios.…”

“…It is clear that contaminants found in eggs are of maternal origin, with females off-loading some of their own contaminant burden to their eggs during egg production [4,5]. However, the specific mechanisms of this maternal transfer of contaminants and the factors that might affect the rate or amount of contaminant transfer from the mother to the egg are not well understood.…”

“…However, in birds there is significant variability in the lipid-normalized egg-to-maternal tissue contaminant ratios among species, and ratios often deviate from 1 [4,6]. It has been suggested that this variability in maternal transfer among species might be related to the differences in reproductive strategies and level of egg investment [4].…”

“…However, in birds there is significant variability in the lipid-normalized egg-to-maternal tissue contaminant ratios among species, and ratios often deviate from 1 [4,6]. It has been suggested that this variability in maternal transfer among species might be related to the differences in reproductive strategies and level of egg investment [4]. Although there have been some within-species studies on the effects of laying order and chemical structure of the contaminant on maternal transfer [5,7,8], the influence of individual variation in characteristics such as body burden and yolk precursor levels on maternal transfer has received less attention.…”

Why Do Organochlorine Differences between Arctic Regions Vary among Trophic Levels?

“…Since the half-life of recalcitrant OCs in seabirds and marine mammals is on the order of years, if not longer, OC concentrations in marine mammals and seabirds reflect a much longer time period (decades) than in zooplankton and arctic cod. Even young marine mammals and seabirds will reflect the past contamination, because of efficient maternal transfer of OCs to the offspring (26,49). Thus, higher levels of PCBs in seabirds and marine mammals from the CBS are likely due in part to higher concentrations of PCBs in the past in this region.…”