Surface egg structure and early embryonic development of the Antarctic toothfish, Dissostichus mawsoni Norman 1937
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The Antarctic toothfish (Dissostichus mawsoni Norman 1937) is the largest notothenioid inhabiting high-latitude Antarctic waters, where it is an important fishery resource and plays a key ecological role at a high trophic level. Despite the considerable amount of data on D. mawsoni biology and distribution developed since the fishery began in 1997, crucial aspects of the life cycle, including spawning and early life history, remain undescribed. During the first winter longline survey to the northern Ross Sea region in 2016, ripe male and female D. mawsoni were collected for the first time, and in vitro fertilisation of eggs was performed. Here, we report on the first characterisation of D. mawsoni egg structure and initial embryonic development. The duration of the egg cleavage period was similar to that of other nototheniid species releasing pelagic eggs. The structural features of fertilised eggs, including chorion thickness and structure, support the hypothesis that eggs of D. mawsoni are pelagic. The data presented here contribute to the description of the potential habitat of the eggs of this species, and provide the first diagnostic information to recognise the eggs of D. mawsoni.
KeywordsChorion SEM Notothenioidei Spawning Reproduction
Toothfish egg collection was made possible by funding from the New Zealand Ministry for Primary Industries under contract ANT201501, and with excellent technical support by the Captain and crew of the FV Janas and Talleys fisheries, LTD. The study supported by the Italian National Programme for Antarctic Research (PNRA) project 2015/B1.02 contributes to the SCAR Scientific Research Program AnT-ERA (Antarctic Thresholds - Ecosystem Resilience and Adaptation).
Compliance with ethical standards
Dissostichus mawsoni samples were collected onboard the FV Janas in June of 2016 by bottom longline. Sampling was carried out in accordance with permit AMLR/15/01/Janas/ZMTW issued by the New Zealand government under the Antarctic Marine Living Resources (AMLR) Act 1981.
Multi-layer structure of Dissostichus mawsoni chorion shown as Z-stack animation. Images were captured at a chorion cross fracture of the chorion through DIC microscopy. Supplementary material 1 (AVI 15,558 kb)
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