Newly published research has suggested that a period of catch-up growth in underfed young guppies causes them to have smaller brood sizes when they reach adulthood.
Scientists from the University of California discovered that juvenile Trinidadian guppies (Poecilia reticulata) that underwent a catch-up growth spell had approximately 20% fewer babies in each brood, even though their growth spurt meant they had reached a normal size before breeding.
One of the researchers, Dr Sonja Auer, explained, "When food levels increase after a period of low availability, many organisms including humans undergo what is called 'catch-up' or compensatory growth. This accelerated growth response allows them to catch up, fully or in part, to the body size they would have achieved under more favourable food conditions."
Dr Auer added: "We found that female guppies that underwent compensatory growth as juveniles produced fewer offspring than would be expected for their body size relative to females that underwent normal growth as juveniles."
The findings, which appear in the journal Ecology Letters, explain that catch-up growth in guppies does not affect the number of broods or the size of the individual babies in each brood.
Guppy husbandry and diets
Guppies are livebearers that can give birth at regular intervals of around 25 days. They can have their first brood at around 60-70 days of age. This study used laboratory-born descendents of fish collected from the Turure River in Trinidad.
A total of 22 broods of fish were used in the experiments. Once the juvenile fish were 14 days old, two sibling females with a similar body mass and length were selected from each brood and kept individually in 8-litre aquaria.
One sibling was given a reduced amount of food for the next 14 days, after which the feeding restrictions were lifted. The other sibling was a control fish and was always fed enough so that uneaten food had to be removed daily.
Catch-up growth
The researchers found that the dieted fish grew much slower than the control fish during the 14-day diet, but then grew roughly 30% faster than control fish once the diet had finished.
For more information see the article: Auer SK, Arendt JD, Chandramouli R, Reznick DN. (2010) Juvenile compensatory growth has negative consequences for reproduction in Trinidadian guppies (Poecilia reticulata). Ecol. Lett. 13(8) 998-1007.