Rotifer enrichment with DHA did not improve growth and survival rate of yellowtail clownfish (Amphiprion clarkii) larvae

Docosahexaenoic acid (DHA) enrichment of live food is a common practice to improve growth and survival of larvae. The current research aimed to test the effect of rotifer enrichment with DHA on growth, survival, fatty acid profile, digestive enzymes, antioxidant parameters, and histology in yellowtail clownfish (Amphiprion clarkii) larvae. Four levels of enrichments emulsions with DHA were considered, including DHA6 (6% DHA), DHA12 (12% DHA), DHA24 (24% DHA), and DHA36 (36% DHA). No substantial differences in growth data were recorded, suggesting that even 6% DHA emulsion enrichment which resulted in 4.22% DHA in rotifers is enough to fulfil the DHA requirements of yellowtail clownfish larvae to maximise the growth rate. Excessive levels of DHA (36%) decreased the survival rate of larvae. This fatty acid accumulated in the larvae body at high levels (24.72%). The DHA12 group had the lowest growth, possibly due to lower digestive enzymes and antioxidant activities in this treatment. There was a positive correlation between final weight and lipase (59%), protease (73%), and lactate dehydrogenase (69%). Furthermore, amylase, lipase, protease, and alkaline phosphatase had significant positive correlations with catalase (72%, 84%, 74%, and 66%, respectively) and lactate dehydrogenase (64%, 85%, 79%, and 77%, respectively). Superoxidase dismutase and catalase also had positive correlations with arachidonic acid levels in the body. Increased DHA levels, based on histology data, caused lipid vacuoles in enterocytes and hepatocytes. In conclusion, yellowtail clownfish larvae can grow well with high survival even with feeding rotifers enriched with 4.22% DHA or less.

Automated summary

This study investigated the effects of different levels of DHA enrichment on the growth, survival, fatty acid profile, digestive enzymes, antioxidant parameters, and histology of yellowtail clownfish larvae. The results showed that a DHA concentration of 6% in rotifer enrichment was sufficient to fulfill the DHA requirements and maximize the growth rate of the larvae. High levels of DHA (36%) decreased larval survival, while the DHA12 group had the lowest growth due to lower digestive enzymes and antioxidant activities.