Egg-release behaviour in Antarctic krill

Tarling, Geraint Andrew ORCID:; Cuzin-Roudy, J.; Wootton, K.; Johnson, M.L.. 2009 Egg-release behaviour in Antarctic krill. Polar Biology, 32 (8). 1187-1194.

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The process of egg release is a complex and crucial step in the life cycle of euphausiids, especially with regards mortality and recruitment success. We examined this process in Antarctic krill (Euphausia superba) in terms of the functioning of the female genital apparatus and associated swimming behaviour. A tethering technique combined with video analysis was used to make observations of three females during the release process. We found eggs were steadily extruded over a period of up to 10 h, during which time the krill released between 1,600 and 4,000 eggs and the ovary reduced by a half in length and a third in height. Eggs were mainly released individually or, less commonly, in batches of between 2 and 4 eggs. Release rates were between 5 and 30 eggs min(-1). The steady release of eggs fits well with histological evidence that mature oocytes must pass individually through tight genital ducts with narrow apertures, before coming in to close contact with the sperm plug for fertilisation, and then expulsion from the thelycum as fertilised eggs. During spawning, the female alternated between slow and rapid rates of pleopod beating with egg release occurring at the moment of beat acceleration. At the point of release, the descent of the egg was accelerated through downward beats of the 7th thoracic leg. The cyclic pattern in pleopod beat-rate during spawning may alter swimming performance and contribute to the widely reported sex- and maturity-based biases within krill swarms.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: BAS Programmes > Polar Science for Planet Earth (2009 - ) > Ecosystems
ISSN: 0722-4060
Additional Keywords: Euphausia superba; Southern Ocean; Scotia Sea; Fecundity; Spawning; Behaviour
NORA Subject Terms: Marine Sciences
Biology and Microbiology
Ecology and Environment
Date made live: 12 Nov 2010 14:43 +0 (UTC)

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