Fig. 3.

IHHN gross signs. (a) A moribund small juvenile Litopenaeus stylirostris with severe acute IHHN disease. Small buff-colored spots are apparent under the cuticle of the carapace and abdominal tergal plates; (b) large moribund juvenile L. stylirostris with acute IHHN. Mottling in the cuticle is readily apparent in the center shrimp. The spots fade as the disease progresses and shrimp of this species in the final stages of the disease often bluish in color and may present necrotic, melanized edges of the cuticle; (c and d) subadult Litopenaeus vannamei with bent (to the left) rostrums, a classic sign of ‘runt deformity syndrome’ (RDS); (e) a juvenile L. vannamei with RDS. In this specimen the rostrum is bent to the right and the antennal flagella are wrinkled, brittle and mostly broken-off; and (f) juvenile L. vannamei with RDS from a nursery population at ∼day 60 post stocking. The principal effect of RDS shown is the marked disparity in sized of shrimp of the same age.