TUCKER: LARVAL DEVELOPMENT OF CITHARICHTHYS AND ETROPUS 



margins between the anus and the caudal fin 

 base. 



During midflexion (6 mm, see Fig. 4B), inter- 

 nal pigment appears along the dorsal notch be- 

 tween the midbrain and hindbrain, and one or 

 two round melanophores appear below the notch. 

 Visible internal notochordal pigment is re- 

 stricted to the vicinity of the external caudal 

 band. The dorsal surfaces of one to three forming 

 centra are darkened by about 6 mm. Several 

 melanophores are present along the ventral body 

 margin from just above the tip of the urohyal to 

 just behind the cleithrum. Internal pigment 

 appears between the hindgut and anal fin origin 

 by midflexion. 



By late flexion (8 mm, see Fig. 4C), both sides 

 of the gas bladder are obscured by body muscula- 

 ture, and pigment appears diffuse. Notochordal 

 pigment appears as fine dashes along the dorsal 

 surfaces of three to six centra of caudal vertebrae 

 15-21. As many as 30 or more melanophores may 

 be present along the ventral surface of the gut 

 loop. Pigment along the posterodorsal surface of 

 the midgut extends to the gas bladder and ap- 

 pears as a black lining over the gut. One or more 

 melanophores appear on or just behind the 

 posterodorsal margin of the preopercle. Melano- 

 phores have developed along the elongate second 

 left pelvic ray and begin to develop along the 

 elongate dorsal rays at 8-9 mm. Some larvae 

 have small melanophores near the distal tips of 

 rays at the middle of both dorsal and anal fins. By 

 8 mm, a group of melanophores has appeared 

 along the middle of the caudal fin. The posterior 

 margin of the articular is covered with a stellate 

 melanophore. 



By postflexion (9 mm), myoseptal pigment is 

 present in the caudal band as well as adjacent to 

 dorsal and ventral lines. Internal pigment along 

 the brain surface looks diffuse. Pigment appears 

 on the dorsal fin membrane adjacent to the first 

 dorsal ray at about 11 mm. Body musculature 

 tends to obscure dorsal notochordal pigment in 

 larvae longer than 12 mm. Additional midlateral 

 dashlike melanophores appear near the caudal 

 fin base at 13-14 mm (see Fig. 5A). By about 14 

 mm, all five dorsal and four ventral pigment 

 lines have formed, and myoseptal pigment is 

 well developed. A small amount of pigment is 

 present along the anteroventral edge of the 

 maxillary by about 14 mm. Late transforming 

 larvae have about three small internal melano- 

 phores near the pectoral fin base and just for- 

 ward of the cleithrum beneath the angle of the 



last gill arch (barely visible through the opercle); 

 these probably develop by about 14 mm. Ventral 

 pigment from the urohyal to the cleithrum per- 

 sists until late transformation. By late transfor- 

 mation (see Fig. 5B), midlateral dashlike melan- 

 ophores are present anterior to the caudal band. 



Morphology (Figs. 4, 5; Tables 2, 3) 



General morphological features include later- 

 al compression, a deep head, a deep abdomen, 

 and a looped gut. In early larvae the dorsal pro- 

 file of the head is raised and rounded and the 

 caudal region is slender. The eye is nearly spheri- 

 cal during early development but becomes ellip- 

 soidal in transforming larvae. A ventral choroid 

 fissure is visible from 3-4 mm NL until about the 

 end of the postflexion stage. The nasal capsule is 

 visible by about 3 mm NL. The gas bladder is 

 prominent just above the foregut until the end of 

 postflexion. It bulges slightly on the left side of 

 the body and is not as obvious on the right. A loop 

 forms in the gut by 2 mm NL. The liver occupies 

 a large portion of the anteroventral region of the 

 abdomen. Adult morphometries given in the fol- 

 lowing discussion were derived from Topp and 

 Hoff (1972). 



The mouth is relatively large in larvae and 

 adults. Larval upper jaw length/BL increases 

 slightly from 10.3% (preflexion) to 11.0% (flexion) 

 and then decreases to 9.8% (postflexion). Adult 

 upper jaw length/BL is 12.8%, range 11.8-13.7%. 

 Larval upper law length/HL decreases from 37% 

 to 34%. Adult upper jaw length/HL is 45%. Lar- 

 val lower jaw length/BL increases slightly from 

 13.3% (preflexion) to 13.9% (flexion) and then de- 

 creases slightly to 13.0% (postflexion). Larval 

 lower jaw length/HL decreases slightly from 

 48% to 46% and is only slightly greater than that 

 of C. gymnorhinus. 



Larval snout length is moderate. Larval snout 

 length/BL increases slightly from 6.2% (preflex- 

 ion) to 7.1% (flexion) and then decreases slightly 

 to 6.3% (postflexion). Adult snout length/BL is 

 5.5%, range 4.8-6.2%. Larval snout length/HL is 

 constant at about 22-23%. Adult snout length/HL 

 is 19.5%. 



The larval eye is large, and the relative size of 

 the adult eye is greater than that of any other 

 western North Atlantic Citharichthys or Etropus 

 species except C. amblybregmatus. Larval eye 

 diameter/BL is constant at 9.8% during preflex- 

 ion and flexion and then decreases to 8.5% (post- 

 flexion). Adult orbit length/BL is 10.0%, range 



41 



