Blue Pigment of a Surface-living Oceanic Copepod

Abstract

THE development of special nets has made it possible to sample specifically the plankton living in the uppermost layers of the sea. Routine sampling with such a net, designed by P. M. David at the National Institute of Oceanography, to fish only in the top 4 in. of the water, has been carried out during the present cruise of the R.R.S. Discovery in the Indian Ocean. One of the most striking features of the living hauls is the predominance of blue pigmented organisms, and these have been seen in a wide diversity of groups, among them copepods, mysids, decapods, stomatopod larvæ, siphonophores, chætognaths, salps, doliolids and appendicularians. The most typical members of the catch are pontellid copepods, and these show a blue colour more intense than most other groups. Since blue is a colour almost completely absent in deeperliving plankton, it was considered to be of interest to make a closer examination of this typical feature of the tropical surface plankton. Using the surface net it was possible to capture very large numbers of Pontella fera Dana and ,carry out a simple analysis of its pigment.