Why are dwarf fish so small? An energetic analysis of polymorphism in lake whitefish (Coregonus clupeaformis)

Abstract

Sympatric populations of dwarf lake whitefish (Coregonus clupeaformis) (DLW) and normal lake whitefish (NLW) commonly occur in north temperate and subarctic lakes. DLW have a much lower growth, mature earlier, and have a shorter life span than NLW. Furthermore, they are usually not found when cisco (Coregonus artedi) are present, possibly due to competitive exclusion. In this study, we compared the energy budget of DLW, NLW, and cisco using food consumption rates estimated with mass balance models of chemical tracers (i.e., mercury and radiocesium). These chemicals are globally distributed and can be readily detected in fish and their prey. Our analysis showed that the energy budget of DLW and cisco was similar. DLW and cisco consumed on average 40–50% more food than NLW. The conversion efficiency of DLW and cisco was two to three times lower than that of NLW. These results suggest that DLW and cisco allocated a larger fraction of their energy budget to metabolism than NLW. Our analysis also suggests that the earlier maturation and shorter life span of DLW and cisco may be due to their higher metabolic rates.

Loss of muscle fibres in a landlocked dwarf Atlantic salmon population

“…Without the marine feeding opportunities, Bleke salmon exhibit slow growth and reach sexual maturity earlier than the ancestral condition at a much reduced body size (Nilsen et al 2003;Barlaup et al 2005). Ecological factors related to energetics and feeding are almost certainly responsible for establishing dwarfism in the population, as was documented for Lake Whitefish populations (Trudel et al 2001). However, once established we hypothesise that physiological factors related to scaling and the relatively high maintained costs of supporting an excess number of fibres for the body size would have acted as a powerful selective force for reducing fibre number.…”

“…Bleke salmon retain the paedomorphic characteristics of parr and females becoming sexually mature without undergoing smoltification (Nilsen et al 2003). Dwarfism is common in other salmonidae including arctic charr (Salvelinus alpinus L.) (Skú lason & Smith 1995) and whitefish (Coregonus clupeaformis) (Trudel et al 2001). The landlocked charr morphs from Thingvallvatn, Iceland are thought to have evolved as a consequence of divergent selection promoting differential trophic use (Skú lason & Smith 1995).…”

Scaling of metabolism inHelix aspersasnails: changes through ontogeny and response to selection for increased size

“…In general, accelerated growth is expected to increase total metabolism as a result of elevated expenditures for biosynthesis and tissue deposition (Jörgensen, 1988), but the interdependence of mechanisms 1-3 can lead to different responses of total metabolism (Konarzewski, 1995). For example, fast-growing forms of the lake whitefish Coregonus clupeaformis had lower food consumption and lower metabolism than slow-growing dwarfs (Trudel et al, 2001); artificial selection for increased body size in oysters produced fast-growing individuals which consumed more food but used less oxygen due to lower costs of growth (joules respired per joule of growth) and decreased expenditure for maintenance (Bayne, 1999). Interestingly, MacLaury and Johnson (MacLaury and Johnson, 1972) demonstrated that selection for increased oxygen uptake can produce slow-growing organisms.…”

On the origin of species: insights from the ecological genomics of lake whitefish

“…Normal and dwarf whitefish differ in heritable swimming behaviour: dwarf whitefish typically swim more actively and prefer higher positioning in the water column in experimental laboratory conditions (Rogers et al 2002). Dwarf whitefish also have a higher metabolic rate, partly associated with the cost of more active swimming behaviour, and lower bioenergetic conversion efficiency (growth rate/ consumption rate ratio; Trudel et al 2001). Further evidence that natural selection has played an important role in the phenotypic divergence between dwarf and normal whitefish was provided by means of a F st -Q st analysis (Spitze 1993;figure 1).…”