Epigenetic variations in early cardiovascular performance and hematopoiesis can be explained by maternal and clutch effects in developing zebrafish (Danio rerio).

This is the first study to show maternal and clutch effects on early developmental parameters like blood cell concentration and cardiac performance (heart rate, stroke volume and cardiac output) in developing zebrafish larvae (2-8 days post fertilization, dpf). Ten individuals per parental pair and developmental stage were analyzed. A pronounced interclutch variation of heart rate has been found in younger stages (2-4 dpf), while interclutch variation of heart rate was small in later stages (8 dpf). This effect was more pronounced in offspring from parental fish nourished with living food. The opposite effect was observed in interclutch variation of blood cell concentration. Here only older stages showed significant interclutch variations. Stroke volume and cardiac output had very small interclutch variations throughout all stages. Heart rate was strongly dependent with developmental stage in all groups. Nutritional maternal effects on heart performance and also in blood cell concentration could be detected in the offspring of parent animals either fed with flake food or with living food. Red blood cell count, calculated as a product from red blood cell concentration, was not significantly different in both feeding groups. The number of spawned eggs was not different. In summary, these data indicate that "clutch effects" caused by maternal and/or genetic influences can affect the developmental pattern of cardiac performance and blood cell concentration.