It might be reasonable to speculate that opportunistic algae can
colonize available body surfaces of fish and that these algae may live
and grow as epizoophyton. However, our case of Desmodesmus in
Japanese sillago is seemingly unique; the algae did not only attach on
the surfaces but apparently became entrenched subdermally and formed
colony domeswithin the flesh. A plausible explanation for its entry is via
wounds on the fish skin. Scales covering the lateral line bear central
pores which allow contact of the water with mechanoreceptors of the
lateral line system. As such, entry of algal spores through these central
pores cannot be discounted especially when most of the green spots
were found along or near the lateral line. The algal mucilage found in
the fish palate may have been introduced differently, likely from fishing
baits as proposed by Langdon [16]. No intestinal infection was detected
in our material which was caught alive. It is safe to say no lethal effects
are seen and that the present case of unicellular green algae associated
with Japanese sillago is a form of symbiotic relationship that needs to
be further studied and defined. This first case of Desmodesmus associated
with marine fish will provide new insights into the variable nature of
green algae.