Tuesday, 23 February 2016

Biosciences Seminar Speaker 25 February 2016

Biosciences Seminar Series - Winter 2016
25 February 2016 - 1pm - Zoology Museum

          Diel colour changes in male Sapphirina 

nigromaculata (Cyclopoida, Copepoda)

Prof Kazutaka Takahashi

We are delighted to welcome to our Biosciences seminar series a visitor from The University of Tokyo, Prof Kazutaka Takahashi. Kazutaka is based at the Department of Aquatic Bioscience at the Graduate School of Agricultural and Life Sciences. Kazutaka has a keen interest in zooplankton dynamics, especially the ecology, behaviour and physiology of copepods.

Males of the pelagic copepod genus Sapphirina are known to exhibit brilliant iridescence, presumably to attract mates. However, the males of some species have been described as not being able to produce iridescence. To resolve this 
apparent contradiction, we conducted detailed observations of colouration patterns in Sapphirina nigromaculata, which has been previously described as both iridescent and non-iridescent. 

from: www.whoi.edu
The colouration of male S. nigromaculata ranges from intensely iridescent to transparent with pigmented spots. These two phases appear to have a circadian rhythm, with males turning iridescent at midnight and remaining in that state until several hours after sunrise, then becoming transparent again towards the afternoon. Adult S. nigromaculata occurrence in surface waters shows temporal changes, in that they occasionally occur in higher densities than their average in the water column, particularly from midnight to around noon. 

The synchronization of iridescence in concert with upward migration is considered to be an adaptation for increasing the likelihood of encountering a mate. Observations using a video plankton recorder revealed that the transparent phase is an adaptation for decreasing predation risk by making the copepods more difficult to distinguish while they are associated with doliolids.

Hope to see many of you - everyone most welcome to attend!

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