Feeding of Antarctic Krill

Brief description

Metadata record for data from ASAC Project 668
See the link below for public details on this project.

From the abstracts of some of the referenced papers:

Body shrinkage may be one of the strategies that Antarctic krill use to cope with food scarcity, particularly during winter. Despite their demonstrated ability to shrink, there are only very limited data to determine how commonly shrinkage occurs in the wild. It has been previously shown that laboratory-shrunk krill tend to conserve the shape of the eye. This study examined whether the relationship between the eye diameter and body length could be used to detect whether krill had been shrinking. By tracking individuals over time and examining specimens sampled as groups, it was demonstrated that fed and starved krill are distinguishable by the relationship between the eye diameter and body length. The eye diameter of well-fed krill continued to increase as overall length increased. This created a distinction between fed and starved krill, while no separation was detected in terms of the body length to weight relationship. Eye growth of krill re-commenced with re-growth of krill following shrinkage although there was some time lag. It would take approximately 2 moult cycles of shrinkage at modest rates to significantly change the eye diameter to body length relationship between normal and shrunk krill. If krill starve for a prolonged period in the wild, and hence shrink, the eye diameter to body length relationship should be able to indicate this. This would be particularly noticeable at the end of winter.

A series of experiments was carried out to examine the relationship between feeding, moulting, and fluoride content in Antarctic krill (Euphausia superba). Starvation increased the intermolt period in krill, but had no effect on the fluoride concentration of the moults produced. Addition of excess fluoride to the sea water had no direct effect on the intermoult period, the moult weight, or moult size. Additions of 6 micrograms per litre and 10 micrograms per litre fluoride raised the fluoride concentrations of the moults produced and the whole animals. The whole body fluoride content varied cyclically during the moult cycle, reaching a peak 6 days following ecdysis. Fluoride loss at ecdysis could largely be explained by the amount of this ion shed in the moult.

Lineage

Progress Code: completed

Statement: Dates provided in temporal coverage are approximate only.