The red palm weevil (RPW), Rhynchophorus ferrugineus, is one of the worst palm pests worldwide. In this work, we studied the physiological basis underlying its adaptive strategy against low temperatures. Specifically, we analyzed the main low-molecular-weight biochemical substances acting as possible endogenous cryoprotectants, as well as their efficiency in reducing cold injury by preserving K⁺/Na⁺ homeostasis. Wild pre-pupae were cold-treated (5.0 ± 0.5 °C) or non-treated (23 ± 1 °C) for 7 days. We then determined the levels of: (a) glucose, trehalose and glycerol, spectrophotometrically, (b) amino acids, by liquid chromatography and (c) potassium and sodium, by inductively coupled plasma mass-spectrometry. Cold-treated larvae increased their potassium level, suggesting some degree of chill injury. However, part of the cold-exposed animals was able to develop an efficient overall cryoprotective response which primarily includes glucose, as well as glycerol and several amino acids (mainly alanine). Our study shows for the first time that RPW is capable of deploying effective physiological mechanisms for a rapid response to cold, which could be relevant to improving predictive models of geographic distribution, especially in a context of climate change. The knowledge of the specific molecules involved would allow future studies to try to prevent its adaptive strategy, either by natural or chemical methods.

This study measured the summer mortality rate of breeding waterbirds during a period of three years (1998-2000) in the El Hondo wetland, Spain, an ecosystem of international importance for ornithological diversity. On average, 874 birds died each summer in the study period, but varied from 199 birds in 1998, to 1,690 in 1999. When the observed mortality was expressed as a percentage of the initial breeding populations, the death rates ranged from 1.6% per month in 1998 to 7.7% in 1999. Many of the dead birds gave positive results for the presence of different enterocolic bacteria (30% to 60%) and for the presence of lead shot in their gizzards (30%). These results cannot be however interpreted as percentages causing the ultimate death because many individuals could be only carriers of enterocolic infections and, in addition, many of our positive results for the presence of lead correspond to sub-lethal values. Nevertheless, our results suggest that a significant decrease in the summer mortality r...