Ink particles injected into the hemolymph of the American lobster (Homarus
americanus), spiny lobster (Panulirus interruptus). crayfish (Procamborus c
larkii), and ridgeback prawn (Sicyonia ingentis) were rapidly removed from
circulation, and most were sequestered within nodules in the gills. The mor
phology of the gills and the nodules were examined from the time of injecti
on until the following molt. The process by which ink was cleared from the
gills was the same in all four species. Nodules formed within 10 min after
injection and were composed of hemocytes loosely attached to one another an
d binding small quantities of ink. Within one week, nodules became spherica
l and more compact with accumulations of ink surrounded by layers of flatte
ned hemocytes. By one month, hemocytes in the nodules had degenerated leavi
ng melanized masses which lay between the gill epithelium and the exoskelet
on. Following molting, the gills of both trichobranchiate and dendrobranchi
ate species were clean or had very reduced numbers of nodules, and melanize
d masses were seen attached to the inner surface of the shed exoskeletons.
A similar mechanism for cleaning the gills has been reported in crustaceans
infected with parasites and in necrotic gill tissue caused by exposure to
toxic heavy metals. We, therefore, suggest that the ability of the gill epi
thelium to wall off Foreign material so that it is lost during the followin
g molt is a general mechanism to prevent occlusion of the gill and maintain
its role in ion regulation and respiration.