Abstract
Diagnostic features for the identification of postlarval Penaeus found in the shore waters of the Philippines are described and categorized based on specimens caught from the wild and those hatched and reared in the laboratory. Differentiating features for postlarval Penaeus are given which include the relative length of the antennular flagellum, the shape of the rostrum and number of rostral teeth, the antennal spine, the spinules on the dorsal carina of the sixth abdominal segment, and chromatophore patterns. Postlarval Penaeus were classified into two species and two groups as follows : (1) P. monodon, larger in size with dense chromatophores, and the long inner antennular flagellum being more than 2.0 times the outer antennular flagellum ; (2) P. semisulcatus, the inner flagellum being 1.6 to 2.0 times the outer antennular flagellum, with the absence of chromatophore on the middle portion of the telson and uropods ; (3) P, merguiensis group, less pigmented, the inner flagellum being less than 1.6 times the outer flagellum and (4) P. japonicus group, a short rostrum, presence of spinules on the dorsal carina of the sixth abdominal segment, and dense chromatophores. The determinations were confirmed by rearing experiments.
