Bijensterfte, oorzaken en gevolgen

[New study by Alaux et al, 2010, Biology Letters]

ABSTRACT
The maintenance of the immune system can be costly, and a lack of dietary protein can increase the susceptibility of organisms to disease. However, few studies have investigated the relationship between protein nutrition and immunity in insects. Here, we tested in honeybees (Apis mellifera) whether dietary protein quantity (monofloral pollen) and diet diversity (polyfloral pollen) can shape baseline immunocompetence (IC) by measuring parameters of individual immunity (haemocyte concentration, fat body content and phenoloxidase activity) and glucose oxidase (GOX) activity, which enables bees to sterilize colony and brood food, as a parameter of social immunity. Protein feeding modified both individual and social IC but increases in dietary protein quantity did not enhance IC. However, diet diversity increased IC levels. In particular, polyfloral diets induced higher GOX activity compared with monofloral diets, including protein-richer diets. These results suggest a link between protein nutrition and immunity in honeybees and underscore the critical role of resource availability on pollinator health.

Cédric Alaux, François Ducloz, Didier Crauser and Yves Le Conte
Biol. Lett. published online 20 January 2010

Important findings of this study include:

"Interestingly, polyfloral diets enhanced some immune functions compared with monofloral diets, in particular GOX activity, meaning that the diversity in floral resources confers bees with better in-hive antiseptic protection. This demonstrates that diet diversity is important and that a minimal nutrient diversity may not meet all honeybee needs. Because nitrogen content was equal between the mono- and polyfloral diets, additional properties might be present in the pollen mix. For example, essential amino acids from protein digested are required in specific proportions to complete their normal growth and development (de Groot 1953). Low pollen diversity might represent a major limiting factor for honeybee’s development, but a polyfloral diet might increase the diversity and/or the proportion of specifics proteins and amino acids required for tissue development (fat body and HPGs). This assumption is supported by the study of Tasei & Aupinel (2008) showing that bumble-bee larvae fed with a polyfloral blend were heavier than larvae fed with monofloral diets of higher protein content."

"If nutrition is a critical factor in immune response, then malnutrition is probably one of the causes of immunodeficiency in honeybee colonies. This work also emphasizes the importance of diet diversity and underscores the need for further studies to test different blends of proteins and identify protein ‘cocktails’ essential for developing normal immune function."

Full paper:
http://rsbl.royalsocietypublishing.org/content/early/2010/01/18/rsbl.2009.0986.abstract

See also:
Does the protein content of pollen play a role in honeybee decline?