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IATTC Early Life History group publishes two new studies on genetic analysis of yellowfin spawning and ocean acidification effects on yellowfin eggs and hatched larvae
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29 abr. 2023

IATTC Early Life History Group Publishes A New Study of Genetic Analysis of Spawning Ecology of Captive Yellowfin

The IATTC Early Life History Group has published a new genetic study of the spawning ecology of broodstockAchotines-01.jpg yellowfin tuna (YFT) using mitochondrial DNA (mtDNA) analysis.  The study identified individual spawning females and their spawning periodicity in captivity, as well as the most fertile individuals, by comparing the mtDNA D-loop region of spawning females to their offspring eggs.  The study was conducted at the IATTC Achotines Laboratory, jointly with colleagues from Kindai University of Japan. There were 50 broodstock YFT in the tank during the study period of 2011-2014. By comparing broodstock mtDNA sequences against 555 offspring eggs, it was possible to identify at least 11 broodstock females that spawned during the study period and identify the most fertile individuals. Multiple females participated in single spawning events. An individual female spawned every month for a period of 1.5 years, supporting the concept that YFT females in captivity are capable of spawning for extended periods of time. Another individual female spawned intermittently for about 26 months. The results demonstrated that the D-loop region of YFT displays enough variation to discriminate among individuals and highlights the value of molecular biological approaches in elucidation of the spawning ecology of wild YFT populations and in the management and selection of tuna broodstock for aquaculture purposes. The study was lead-authored by Susana Cusatti, and the co-authors were Dan Margulies and Vernon Scholey, along with Yasuo Agawa and Yoshifumi Sawada of Kindai University. The paper was published in Aquaculture Science, Vol. 70, No. 4, December 2022.

IATTC Early Life History Group Contributes to the Experimental Study of the Effects of Ocean Acidification on Yellowfin Eggs and Hatched Larvae

Vernon Scholey and Dan Margulies of the Early Life History Group co-authored a joint research publication with colleagues from University of Miami to investigate the effects of ocean acidification on the metabolism of yellowfin (YFT) eggs and newly-hatched larvae. The study was conducted at the IATTC’s Achotines Laboratory. Early life stages of fish are thought to be particularly susceptible to CO2 exposure, since acid-base regulatory faculties may not be fully developed. The study examined the effects of near-term projected levels of acidification (1900 uatm CO2) on metabolic rate, yolk sac depletion, and oil globule depletion to assess overall energy usage. YFT showed mixed sensitivity to CO2 exposure. YFT eggs showed no significant impact of CO2 for any measured endpoints, including metabolic rate, yolk sac and oil globule depletion, nitrogenous waste accumulation or excretion. This suggests that embryos within the eggs experience minimal alterations to energetic utilization due to CO2. In contrast, newly-hatched larvae experienced a significant reduction in metabolic rate that could have resulted from metabolic depression or a developmental delay. Newly-hatched larvae also Diagram

Description automatically generatedexperienced an increase in ammonia excretion with CO2 exposure, suggesting that CO2 excretion pathways facilitated ammonia elimination. Whatever the mechanism of increased ammonia excretion may be, it did not change nitrogen tissue content (ammonia or urea) in embryos or larvae. The study results suggest that CO2 at levels relevant for current day upwelling zones and near future climate change in the EPO may impact YFT early larval stages. The study was lead-authored by Rachael Heuer of University of Miami  and published in Comparative Biochemistry and Physiology, Part A 280: 111398, 2023, at: https://doi.org/10.1016/j.cbpa.2023.111398.