2.4. Experimental infection
LCDV-ss-free black rockfish individuals (n = 30, three of them were
sacrificed to confirm the absence of LCDV-ss by PCR), with a mean
weight of 400 ± 20 g, were used to evaluate experimental infection.
The fish were obtained from an aquarium farm in Qingdao, Shangdong
Province, and kept in a tank with a flow-through, filtered and virus-free
water system. The tank was maintained at approximately 18–22 °C, and
its water quality was daily monitored. Fish of each group (n = 10) were
challenged with 0.1 mL purified virus or PBS (control) and then maintained
for 50 days. Clinical signs of infection were daily monitored,
and the incidence was determined at 50 days post-challenge (p.c.). At
the end of the experiment, the nodules were dissected and prepared
as described in Section of 2.3 and examined by TEM.