Flow-mediated plasticity in the expression of stickleback nesting glue genes.

Nest construction is an essential component of the reproductive behavior of many species, and attributes of nests - including their location and structure - have implications for both their functional capacity as incubators for developing offspring, and their attractiveness to potential mates. To maximize reproductive success, nests must therefore be suited to local environmental conditions. Male three-spined sticklebacks (Gasterosteus aculeatus) build nests from collected materials and use an endogenous, glue-like multimeric protein - "spiggin" - as an adhesive. Spiggin is encoded by a multigene family, and differential expression of spiggin genes potentially allows plasticity in nest construction in response to variable environments. Here, we show that the expression of spiggin genes is affected significantly by both the flow regime experienced by a fish and its nesting status. Further, we show the effects of flow on expression patterns are gene-specific. Nest-building fish exhibited consistently higher expression levels of the three genes under investigation (Spg-a,Spg-1, and Spg-2) than non-nesting controls, irrespective of rearing flow treatment. Fish reared under flowing-water conditions showed significantly increased levels of spiggin gene expression compared to those reared in still water, but this effect was far stronger for Spg-a than for Spg-1 or Spg-2. The strong effect of flowing water on Spg-a expression, even among non-nesters, suggests that the increased production of spiggin - or of spiggin rich in the component contributed by Spg-a - may allow more rapid and/or effective nest construction under challenging high flow conditions.