Effects of short- and long-term enrichment on brain and behavior in Trinidadian guppies

Environmental enrichment (EE) often increases positive behavioral and physiological effects on captive animals. Fish are commercially and scientifically important taxa that have been shown to benefit from EE. Here we examined the effects of both short- and long-term EE in Trinidadian guppies (Poecilia reticulata). In the short-term exposure to EE, female guppies were raised in standard conditions, and after reaching adulthood were moved to either an enriched or a deprived environment for 2 weeks. Long-term exposure guppies were reared from birth for 12 weeks (until sexual maturity) in either an enriched or deprived environment. We then assessed growth, brain size, and neophobic and exploratory behaviors in standard assays. Guppies given EE were bolder, regardless of timescale, although females showed a more pronounced change in behaviors than males. We further found that guppies reared with EE were smaller yet had larger relative brain sizes than guppies reared under deprived conditions. Here we highlight that EE had influenced growth, brain size, neophobic, and exploratory behaviors in guppies, and behavioral changes were observed after only 2 weeks. Our results highlight the need for assessing the influences of EE in captivity, in particular for researchers studying cognition and behavior.