The cephalopod prey of the Weddell seal, Leptonychotes weddellii, a biological sampler of the Antarctic marine ecosystem

Abstract

International audienceWeddell seals, Leptonychotes weddellii, areimportant apex predators in the food web of the Antarcticmarine ecosystem. However, detailed information on theirtrophic relationships with cephalopods is scarce. Moreover,cephalopods play a key role in the marine environment, butknowledge of their feeding habits is limited by lack of data.Here, we have combined the use of this seal as a biologicalsampler together with measurements of the stable isotopicsignature of the beaks of their cephalopod prey. Thus, theaims of the present study were: (1) to examine in detail thecephalopod portion of the diet of Weddell seals by meansof scat analysis and (2) to assess the habitat use and trophiclevel of the different cephalopod prey taxa identified. FromJanuary to February 2009, a total of 48 faecal droppingswere collected at Hope Bay, Antarctic Peninsula. Cephalopodswere mainly represented by beaks (n = 83) whichwere identified to the lowest possible taxonomic level.Furthermore, subsamples of beaks were separated for furtherisotopic analysis. Relative abundance of stable isotopesof carbon (d13C) and nitrogen (d15N) was determined by continuous-flow isotope-ratio mass spectrometry.Cephalopods were represented uniquely by octopods of thesubfamily Eledoninae. Pareledone turqueti was the dominantprey species followed by the papillated Pareledonespecies group and Adelieledone polymorpha. We concludethat Weddell seals preyed primarily on benthic preyresources. Furthermore, the relatively similar d13C andd15N values in beaks of the three octopod prey taxa suggestthat these share the same type of habitat and occupy similartrophic level positions

Life histories of Antarctic incirrate octopods (Cephalopoda: Octopoda)

“…Antarctic octopods are important components in the diets of demersal fishes, southern elephant seals and Weddell seals [20–22]. However, knowledge about their feeding ecology and trophic positions are still preliminary [23–25]. Reproductive studies of Antarctic octopods have revealed that all species produce large eggs, which likely produce benthic crawling hatchlings that are adult miniatures [26–30].…”

Diet of Cuvier’s beaked whales Ziphius cavirostris from the North Pacific and a comparison with their diet world-wide

“…Predators serve as 'biological samplers,' and cephalo pod beaks obtained from stomach contents have also been used to better understand the dynamics of oceanic food webs, especially in the Southern Ocean (e.g. Xavier et al 2013, Guerreiro et al 2015, Negri et al 2016, Seco et al 2016). In the North Pacific, little information is available on the ecology of cephalopod prey families identified from our study.…”

Antarctic octopod beaks as proxy for mercury concentrations in soft tissues

“…Within the Southern Ocean food webs, cephalopods are known to play important roles as both mid-trophic predator and prey for numerous top predators, including seabirds (Alvito et al, 2014;Casaux and Ramón, 2002;Cherel and Klages, 1998), marine mammals (Clarke, 1980;Negri et al, 2016;Rodhouse et al, 1992) and fish (Seco et al, 2016;Smales, 1996;Xavier et al, 2002). Since cephalopods are very elusive animals, researchers have still not fully addressed the existing gaps of knowledge regarding their ecology, including levels of contaminants such as Hg (Xavier et al, 2016).…”