Adult fish rely on gills to extract oxygen from the surrounding water. Larval fish, on the other hand, do not have well-developed gills and instead rely primarily on gas exchange across their skin.
In a new study published in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology, researchers examined whether larval fish could use their pectoral fins to increase the flow of water over their skin and, in so doing, increase oxygen uptake into the body. This response is thought to be an important way for larval fish to deal with low environmental oxygen conditions.
**Check out a 5-day-old larval zebrafish moving its pectoral fins here.
Examination of the responses of larval zebrafish (Danio rerio) to hypoxia 4 days after fertilization showed the animals do move their pectoral fins more than those exposed to normal oxygen conditions. This pectoral fin response decreased 15 days after fertilization and disappeared altogether by 21 days, a time that corresponded to when the gills were able to take over the role of oxygen uptake. In addition, larval rainbow trout (Oncorhynchus mykiss) that were not able to move their pectoral fins had lower oxygen uptake across the skin than those that were able to wash water over their skin. In contrast, oxygen uptake was not altered in larval zebrafish that were not able to move their pectoral fins.
What these findings show is that the pectoral fins are an important way for larval rainbow trout to improve oxygen uptake in hypoxic water conditions, whereas the role of the pectoral fins in altering skin oxygen transfer in larval zebrafish is not clear.