# The influence of magnetic fields on the early ontogeny of the rainbow cichlid Herotilapia multispinosa (Günther, 1867)

## TL;DR

This study explores how different magnetic field intensities affect the development of rainbow cichlid embryos and larvae.

## Contribution

The study demonstrates that specific magnetic field intensities can influence embryonic development rates and posthatching growth in rainbow cichlids.

## Key findings

- A 5 mT magnetic field accelerated embryogenesis, producing larger hatchlings with smaller yolk sacs and slower growth.
- A 3 mT magnetic field prolonged embryogenesis, resulting in smaller hatchlings with larger yolk sacs and faster posthatching growth.
- Magnetic fields may be used in aquaculture to improve breeding outcomes in rainbow cichlids.

## Abstract

The aim of this study was to determine the influence of static magnetic fields with intensities of 1 mT, 3 mT, and 5 mT on the embryonic and postembryonic development of the rainbow cichlid (Herotilapia multispinosa). The experiments were conducted using eggs obtained from sexually mature, actively spawning pairs of this species. Analysis of the results showed that the applied magnetic fields significantly affected the rate of embryogenesis, which, depending on the intensity, could be either accelerated or slowed down. In particular, exposure to a 5 mT field accelerated development and produced larger hatchlings with smaller yolk sacs but lower subsequent growth, whereas exposure to a 3 mT field prolonged embryogenesis, resulting in smaller hatchlings with relatively larger yolk sacs and faster posthatching growth. The findings suggest that appropriately selected magnetic field parameters may positively influence the development of eggs and larvae of the rainbow cichlid, indicating the potential application of this method in ornamental fish aquaculture to reduce breeding losses.