Effects of different incubation and start-feeding temperature regimes on growth, survival, and histomorphology of cod larvae
Mean lengths of newly hatched cod larvae from egg incubation at 4 °C (Low-L) and 9.5 °C (High-H) were similar, and only minor differences were observed in larval histomorphology. However, growth performance of larvae reared at 4 °C (T1-LL) and 9.5 °C (T2-LH) from the 4 °C egg incubation and 4 °C (T3-HL) and 9.5 °C (T4-HH) from the 9.5 °C incubation group were different during start-feeding and metamorphosis. Incubation and larval rearing temperature affected developmental rate and survival. T1-LL and T2-LH larvae were larger than T4-HH larvae at sampling stage 4 (early larvae), but the differences disappeared thereafter. Larvae from T3-HL did not survive beyond stage 8 (late larvae/start metamorphosis), and survival of T1-LL larvae at the end of the experiment was very low. Larvae from T2-LH were significantly larger than larvae from T4-HH at stage 12 (end metamorphosis). Comparative studies of the histomorphology of vital organs did not reveal temperature-related differences between sampled larvae/early juveniles. Characteristic traits in the histomorphology of cod larvae at the selected developmental stages are presented. Our results show that egg incubation and subsequent larval rearing temperature affected the growth performance and survival but did not have any significant effects on the organ development and histomorphology.
KeywordsAtlantic cod larvae Temperature Development Histomorphology Survival
We would like to thank the staff at the Center for Marine Aquaculture Research in Tromsø for support during the experiment and Lara Agulló Núñez and Fride Tonning at the histolab at the Institute of Arctic and Marine Biology, University of Tromsø, for sectioning and staining of numerous larvae. This investigation was financially supported by the Research Council of Norway (CODE, RCN-project 199482).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed by the authors.
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