Powell and Henley: Larval development of Paralichthys albigutta and P. lethostigma 



5! 1 



were not continuous because a gap 

 appeared just anterior to the anus. 

 Regularly, we observed a pair of 

 melanophores located ventrally on 

 each side of the hindgut. The pecto- 

 ral-fin-ray blade was pigmented. 

 Pigmentation of preflexion P. letho- 

 stigma at the base of the pectoral 

 fin and in the head region was simi- 

 lar to that observed for P. albigutta 

 (Figs. 3A and 5A). Pigment on the 

 maxillary and the dorsum of the 

 midbrain (cranial bump) was less 

 frequently observed in preflexion P. 

 lethostigma larvae compared with 

 preflexion P. albigutta larvae. Cra- 

 nial bump pigment was observed on 

 36% of the specimens and maxillary 

 pigment on 64% of the specimens 

 (rc=25). Pigment on the vomer of 

 preflexion P. lethostigma also oc- 

 curred less frequently (36% of the 

 specimens had this pigment; n-15); 

 however, this pigment was difficult 

 to discern. It was most effectively 

 seen on fresh, cleared and stained 

 material. Ventral pigment on the 

 isthmus, anterior to the cleithrum, 

 did not extend the full length of the 

 isthmus as was observed on pre- 

 flexion P. albigutta (Figs. 3A and 

 5A). The number of melanophores 

 observed on the operculum (com- 

 monly one) was less than that ob- 

 served for P. albigutta. 



Pigment on flexion P. lethostigma 

 larvae was similar to that observed 

 on later preflexion larvae (Fig. 5B). 

 Melanophores were observed on the 

 lateral side of the caudal region; 

 however, they were less organized 

 than those observed for P. albigutta, 

 which appeared to be more banded 

 in appearance. During flexion, pigmentation in- 

 creased on the lateral surface of the hindgut. Dorsal 

 finfold pigmentation was sparse and located at 

 midbody. Ventral finfold melanophores occurred 

 along the distal margin and on the finfold surface at 

 midbody. A melanophore was observed at the ven- 

 tral edge of the pectoral-fin blade, and a distinct 

 melanophore was observed at the junction of the 

 dorsalmost portion of the opercle and the anter- 

 iodorsal portion of the gut. This characteristic pig- 

 mentation was observed for both species. Pigmenta- 

 tion along the ventral midline of the isthmus in- 



D 



Figure 5 



Developmental stages of laboratory-reared southern flounder, Paralichthys 

 lethostigma (C=cranial spines, P=preopercular spines). (A) 3.3-mm-NL early 

 preflexion larva, 9 days old; (B) 6.4-mm-NL late preflexion larva, 24 days old; 

 (C) 7.7-mm-SL postflexion larva, 45 days old; and (D) 9.1-mm-SL transforming 

 postflexion larva, 40 days old. 



creased to cover the entire isthmus. Like P. albigutta, 

 melanophores were typically observed on the maxil- 

 lary and the dorsum of the midbrain, but vomerine 

 pigment was irregularly observed on flexion P. 

 lethostigma larvae. Pigmentation (1^1 melanophores) 

 occurred on the opercular region posterior to the eye. 

 Melanophores along the edge of the interopercle and 

 subopercle were first observed on flexion larvae. 



On postflexion larvae (6.4-9.3 mm SL), pigment 

 was observed at the base of the caudal fin and on the 

 pelvic fin (Fig. 5, C and D). Melanophores occurred 

 on the lateral surface of the body, but they were never 



