Diagnosis: Modal fin-ray counts of D-X,14 A-III,8 are shared among most of the regional Lutjanus species, including L. analis, L. apodus, L. cyanopterus, L. griseus, L. jocu and the deep-water snappers L. buccanella, L. campechanus, and L. vivanus. Juvenile L. jocu have indistinct vertical bars, no lateral spot, and a prominent blue line from under the eye to the maxilla. Juveniles are found in mangrove habitats. (DNA)
Description: Body wide and relatively thick with a sloping forehead and a large round eye and large terminal mouth. Dorsal-fin base long and anal-fin base short. Prominent dorsal, anal, and pelvic-fin spines and a large non-serrated preopercular spine.
Transitional stage: Transitional recruits of L. jocu have a mostly-uniform scattering of fine melanophores on the body with notably indistinct bars against a finely-speckled background. The blue stripe from under the eye to the mid-maxilla is prominent. Transitional analogues: Transitional recruits of L. jocu develop indistinct bars in the same pattern as the prominent bars in L. apodus. The early recruits of the two species can be difficult to separate, but the bars on L. jocu are generally indistinct (particularly below the anterior dorsal-fin spines) and absent on the caudal peduncle. An additional difference is that the melanophores on L. jocu begin as a very fine and dense scattering vs. larger and sparser melanophores on transitional L. apodus (for example, in the space below the eye, there are about 100 melanophores in an area equal to the pupil in L. jocu vs. about 10 in L. apodus). L. jocu recruits can also be difficult to separate from transitional L. griseus, however the latter have large blotchy melanophores over a fine spotted background, vs. uniform fine speckling seen in L. jocu. L. griseus recruits also rapidly acquire their characteristic striping. L. cyanopterus early recruits share the indistinct bars but do not have the obvious blue stripe on the head and they retain their characteristic black edging to the pelvic fins through the transitional phase.
Juveniles: Juvenile L. jocu have few distinct markings other than the thin blue line extending from the maxilla back under the eye and across the operculum. Most juveniles retain some evidence of indistinct bars. Juvenile analogues: Juvenile L. jocu have no lateral spot (vs. L. analis, L. mahogoni, L. synagris, and the deep-water snappers) and indistinct vertical bars (vs. prominent in L. apodus). They are wider-bodied than L. cyanopterus (which lacks the blue line under the eye as well). Juvenile L. griseus intensify the dark stripe through the eye and develop thin dark stripes on the side of the body.
