Long-term trends and sources of organochlorine contamination in Canadian tundra Peregrine Falcons, Falco peregrinus tundrius

Levels of eggshell thinning, and organochlorine residues in egg contents, blood plasma of adults and juveniles, tissue samples, and prey species were determined for a population of migratory Peregrine Falcons (Falco peregrinus tundrius) breeding in the Canadian Arctic. Temporal trends were assessed by comparing data collected during 1991-1994, with data from 1982-1986, for the same population. Shells (n=54) from 1991-1994 averaged 15% thinner than eggs produced prior to the introduction of DDT. No improvement in shell thickness was detected between decades. Mean DDE residue levels in eggs showed a decline from 7.6 mg kg (1982-1986) to 4.5 mg kg (1991-1994), but there was no significant change in SigmaPCB residues. Moreover, the proportion of clutches with eggs exceeding critical SigmaPCB, DDE, and dieldrin residue levels (10%) did not change between decades. Relative to Greenland and Alaskan populations, F. p. tundrius at Rankin Inlet show high levels of organochlorine contamination and little reduction in residues over the last decade. These Tundra Peregrines continue to be exposed to organochlorines in Latin America; however, results also link relatively high levels in the study population with waterfowl species that do not leave Canada in winter.     

The effects of temperature and pressure acclimation on the temperature and pressure tolerance of the shallow-water shrimp Palaemonetes varians

Anthropogenic effects on marine ecosystems (e.g. hypoxia, warming) at and beyond continental margins are assumed to affect physiological and biochemical boundaries to species’ distributions, potentially leading to habitat contraction across depth. Whether or not shallow-water benthic invertebrates are capable of undergoing depth-related migrations in response to such perturbations remains largely unknown. The few studies available have focused solely on whether colonisation of deep waters may be ongoing and on the ability of shallow-water species to tolerate low temperatures and high hydrostatic pressures: two physical parameters, which are thought to limit the depth range of a species. Those studies did not consider the effects of acclimation to low temperature and, especially, acclimation to high hydrostatic pressure on pressure tolerance. We demonstrate that acclimation to both low temperature (5 °C) and to high hydrostatic pressure (10 MPa) increases the pressure tolerance within the shallow-water shrimp Palaemonetes varians. Previous studies have demonstrated the impressive temperature and pressure tolerance of this shallow-water shrimp. Here, we provide evidence that a shallow-water species may acclimate to low temperature and high pressure and show greater pressure tolerance, suggesting that shallow-water organisms may be able to rapidly—and potentially stepwise—acclimate to the low temperature and high pressure conditions typical of the deep sea. These findings are of importance for understanding phylogenetic development from shallow- to deep-water species and the processes behind past, present and future bathymetric range shifts in species.     

The influence of per offspring investment (POI) and starvation on larval developmental plasticity within the palaemonid shrimp,Palaemonetes varians

At the inter-specific level, per offspring investment (POI), degree of abbreviated development, and lecithotrophic potential all increase with increasing latitude and freshwater penetration among crustaceans. These traits are considered adaptations to conditions of decreasing growth potential. We hypothesise that this relationship between POI and abbreviated development also occurs at the intra-specific level. We studied the caridean shrimp, Palaemonetes varians, to investigate the hypothesis that under food-limited conditions, higher POI enables development through fewer larval instars. Under starvation stress, larvae from broods of greater POI (measured as hatchling brood average dry weight, DW) generally developed through fewer larval instars. With increasing starvation period, larval development time increased, whilst larval growth rate, juvenile DW, juvenile carbon mass, and juvenile carbon:nitrogen (C:N) ratio all decreased. Larval development time generally decreased with increasing brood average dry weight. In contrast, larval growth rate, juvenile DW, juvenile carbon mass, and juvenile C:N ratio all increased with increasing larval brood average DW. The relationship between POI and larval instar number (abbreviation of development) reported here is consistent with that at the inter-specific level and supports the concept that macro-ecological trends in development modes at the inter-specific level may be driven by selection occurring on POI at the intra-specific level.