Comprehensive DescriptionRead full entry
Transitional S. tigrinus can be distinguished by having three head stripes extending rearward from the upper eye vs. two in S. baldwini and none in S. tortugarum and S. tabacarius (the latter two species also do not have the cheek stripe). The transitional melanophores forming on the body at the base of the fourth through sixth dorsal-fin spines consist of a single long patch, while in S. baldwini the melanophores split into two patches (usually under the base of the fourth and sixth, sparing the fifth). On S. tortugarum and S. tabacarius the melanophores concentrate on the proximal fin membranes, not initially forming patches on the adjacent body.
Description: Body thin and moderately wide with a round eye and a large terminal mouth. Pectoral and pelvic fins long, reaching just past the vent, dorsal-fin base long and anal-fin base short, caudal peduncle relatively wide and short. The third spinous-dorsal-fin membrane is greatly extended, up to 3 times the length of the next membrane. On the head there is a melanophore at the angle of the jaw. On the body, melanophores are mainly along the ventral midline of the caudal peduncle, typically two or three: the largest just after the last anal-fin element and one or two just before the procurrent caudal-fin rays (occasionally one or two more in between). Some larvae have a melanophore on the dorsal midline of the caudal peduncle just after the last dorsal-fin element. Two large deep internal melanophores are present, one in the mid-upper body below the mid-soft dorsal fin and one in the body just below the base of the last dorsal-fin spine (not always obvious in thick-bodied preserved larvae). Internal melanophores line the dorsal aspect of the swim bladder and posterior peritoneum. The fin membranes are well-marked, with the standard serranid heavy speckling on the pelvic-fin membranes and on the outer half of the pectoral-fin membranes. There are melanophores along the distal third of the spinous-dorsal-fin membranes and lining the tips of the upper and lower lobes of the caudal fin and at the tips of all of the anal fin-ray membranes. Some individuals may have them at the tips of some of the dorsal soft-fin membranes as well. There are also one or a few melanophores near the base of the third anal-fin spine and/or first soft ray. Notably there are melanophores at the base of one (or a few) of the mid-upper as well as mid-lower segmented caudal-fin rays.
Transitional larvae develop three stripes radiating back from the upper eye and an oblique stripe across the cheek. As the markings increase the upper two eye stripes merge and a reticulated pattern of patches and lines develops on the anterior upper body and near the base of the dorsal fin; notably the patch near the base of the fourth through sixth dorsal-fin spines is not divided into two spots. The larval melanophores rapidly fade away as the transitional surface markings progress rearward, a stripe forms from the eye to the tip of snout, and the iris develops a clock-face-like set of surface black patches.