The importance of copepods for growth and pigmentation of the Brazilian basslet Gramma brasiliensis larvae

Abstract

Gramma brasiliensis is a marine ornamental fish popular in the aquarium trade. Developing a reproductive protocol for this species in captivity is an important conservation tool. In this study, we compared the survival, growth, and pigmentation rates of larvae fed different densities of the copepod Parvocalanus crassirostris and the rotifer Brachionus rotundiformis in the first 10 days. The treatments were: Control—(10 rotifers mL⁻¹); Treatment 1 (T1)—(9.5 rotifer mL⁻¹) + (0.5 copepod mL⁻¹); (T2)—(9 rotifers mL⁻¹) + (1 copepod mL⁻¹) and (T3)—(8 rotifers mL⁻¹) + (2 copepods mL⁻¹). Two larvae from each experimental unit were removed on days 1, 3, 5, 7 and 10 and photographed with a magnifying glass for standard length (SL), body height (BH), body width (BW), mouth width (MW) measurements and pigmentation assessment. There was no significant difference between treatments in survival (17 ± 7.2%; mean + SD) (p > 0.05). The use of 2 copepods ml⁻¹ in co-feeding with rotifers yielded the best results, leading to earlier notochord flexion, increased growth, and improved pigmentation compared to using only rotifers in a 10-day larviculture of G. brasiliensis. Even at lower densities (0.5 and 1.0 copepod ml⁻¹), adding copepods to the diet enhanced growth on days 3 and 5, anticipated notochord flexion, and improved pigmentation of the larvae compared to the control group.