The eggs of the brine shrimp,
Artemia salina
, vary in colour from pale cream to dark brown. This variation is due to different amounts of haematin in the egg shells. Nauplii of
Artemia
are bright orange in colour owing to a carotenoid pigment, esterified astaxanthin. The same carotenoid is present in the eggs. Adult
Artemia
which has been reared on bakers’ yeast, in which we found no carotenoids, contains only a small amount of astaxanthin ester, presumably derived from that present in the egg. The carotenoids of the unicellular algae
Dunaliella tertiolecta
and
Phaeodactylum tricornutum
have been examined as a preliminary to feeding experiments with
Artemia
. The carotenoids identified from
Dunaliella
were
β
-carotene,
γ
-carotene, a carotene oxide, lutein, violaxanthin, and neoxanthin; those from
Phaeodactylum
were
β
-carotene, diadinoxanthin, fucoxanthin and neofucoxanthin. Adult
Artemia
reared on
Dunaliella
retains varying amounts of all the algal carotenoids, and in addition changes some of them to astaxanthin which becomes esterified and is quantitatively the most abundant carotenoid in the animal. A keto-carotenoid has been found in
Artemia
examined soon after being fed on
Dunaliella
.
Artemia
fed on
Phaeodactylum
retains all the algal xanthophylls to some extent. No
β
-carotene was found in the animals; a large amount of a keto-carotenoid was found, as well as astaxanthin. There is evidence that
β
-carotene in the algal food is the precursor of astaxanthin found in the adult
Artemia
and that the transformation proceeds through the keto-carotenoids.
