Physiological and morphological colour change in Antarctic krill, Euphausia superba: a field study in the Lazarev Sea

Auerswald, L, Freier, U, Lopata, A and Meyer, B 2008, 'Physiological and morphological colour change in Antarctic krill, Euphausia superba: a field study in the Lazarev Sea', The Journal of Experimental Biology, vol. 211, no. 24, pp. 3850-3858.


Document type: Journal Article
Collection: Journal Articles

Title Physiological and morphological colour change in Antarctic krill, Euphausia superba: a field study in the Lazarev Sea
Author(s) Auerswald, L
Freier, U
Lopata, A
Meyer, B
Year 2008
Journal name The Journal of Experimental Biology
Volume number 211
Issue number 24
Start page 3850
End page 3858
Total pages 9
Publisher The Company of Biologists Ltd
Abstract Antarctic krill, Euphausia superba, is very susceptible to harmful solar radiation because of its unique genetic setup. Exposure occurs in spring to autumn during vertical diel migration and during occasional daytime surface-swarming. We have investigated colour change in Antarctic krill, Euphausia superba, during summer and winter in the Lazarev Sea in response to ultraviolet radiation (UVR) and photosynthetically active radiation (PAR). Short-term physiological colour change and long-term (seasonal) morphological colour change are present. Both are facilitated by a single type of monochromatic red chromatophore, i.e. erythrophores, of 20-450mu m diameter. Superficial erythrophores cover large dorsal areas, especially above vital organs (brain, sinus glands), additional 'profound' erythrophores cover internal organs (heart, gut, nerve cords). Short-term change in light regime causes rapid physiological colour change along dense bundles of microtubules: pigment disperses into chromorhizae upon exposure to PAR and UVA and to a lesser extent to UVB. Darkness leads to aggregation of pigment in the centre and hence blanching. There is no circadian rhythm in the dispersal state of erythrophores present in winter. Physiological colour change in adult krill is two to three times more rapid in summer than in winter. Furthermore, seasonal changes in light regime also result in a profound morphological colour change: in summer animals, abdominal astaxanthin concentration is 450% and erythrophore count is 250-480% higher than in winter krill. We conclude from our results, that pigmentation of E. superba serves in the protection from harmful solar radiation and is adapted to the varying diel and seasonal light conditions.
Subject Marine and Estuarine Ecology (incl. Marine Ichthyology)
Keyword(s) colour change
chromatophore index
UV protection
pigmentation
astaxanthin
erythrophore
DOI - identifier 10.1242/jeb.024232
ISSN 0022-0949
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