Developmental plasticity in fish exposed to a water velocity gradient: a complex response

Area of Science:

• Evolutionary biology
• Developmental biology
• Ichthyology

Background:

• Developmental plasticity is crucial for evolution and understanding environmental impacts on developing organisms.
• Water velocity is a known environmental factor influencing plasticity in salmonids, but its ontogenetic effects are not well-documented.

Purpose of the Study:

• To investigate the ontogenetic component of developmental plasticity in rainbow trout (Oncorhynchus mykiss) in response to varying water velocities.
• To characterize morphological changes throughout ontogeny under different constant water velocity treatments.

Main Methods:

• Rainbow trout specimens were reared for 100 days in four constant water velocity treatments (0.4, 0.8, 1.6, and 3.2 cm/sec).
• Traditional and geometric morphometrics were employed to analyze morphological changes across treatments and developmental stages.

Main Results:

• Early and complex developmental plasticity was observed in Oncorhynchus mykiss in response to water velocity.
• Plasticity was detected early in development (15-20 mm), primarily affecting fin-related traits.
• Body shape responses were non-congruent with expected functional adaptations, with the fastest velocity treatment resulting in a robust shape similar to the slowest treatment.

Conclusions:

• The study reveals complex, stage-specific shape changes in rainbow trout influenced by water velocity.
• Non-linear responses suggest that different water velocities can lead to divergent interpretations of plasticity.
• Emphasizes the importance of considering functional requirements and adaptations beyond simple hydrodynamic effects in evolutionary and ecological contexts.