Runt-Deformity Syndrome in cultured giant tiger prawn Penaeus monodon

A total of 24 morphological abnormalities associated with the Runt-Deformit y Syndrome (RDS) is reported for the first time in 17- to 18-mo old F-3 gen eration Penaeus monodon (>40 mm CL) belonging to three breeding families. A lthough diagnosed as positive for the infectious hypodermal and hematopoiet ic necrosis virus (IHHNV), the shrimp appeared normal at 9 to 10 mo when th ey were procured from a commercial facility in Antique, central Philippines , in September 1996. The abnormalities affected either specific shrimp orga ns and appendages (e.g., rostrum, antennae, uropods) or the whole body (e.g ., shell color and hardness). A two-way analysis of variance was used to ev aluate differences in the morphometric characters rostral length (RL), cara pace length (CL), abdominal length (AL), body length (BL), total length (TL ), carapace width (CW), 1(st) abdominal segment width (AS(1)W), and body we ight (BW) and the morphometric ratios RL:CL, CL:AL, and CW:AS(1)W by sex an d stock (3 families and wild controls). Female P. monodon had significantly larger CL, AL, BL, TL, CW, and BW than males, regardless of stock. Wild fe males had longer BL and TL than cultured ones, whereas wild male shrimp had shorter CL, CW, and BW than cultured male P. monodon. Cultured shrimp had significantly higher CL:AL and CW:AS(1)W ratios and lower RL:CL ratio compa red to wild P. monodon. The shorter and narrower abdomen relative to the ca rapace gave the shrimp a "runted" or dwarf appearance characteristic of RDS earlier described in Litopenaeus vannamei with IHHNV. Confirmed by paralle l studies, IHHNV infection of the cultured P. monodon may account for their cuticular deformities, slower growth, and smaller sizes. The appearance of deformities in older (and bigger) P. monodon suggests that RDS expression is dependent on age and size. Examination for external abnormalities and ev aluation of the three morphometric ratios may complement existing screening protocols for diseases and growth rates in shrimp breeding programs. Cultu red giant tiger prawn also had lower sperm count, greater proportion of dea d and abnormal sperm, and lower incidence of mating (absence of sperm in th elyca) compared to wild P. monodon.