Trnski et al.: Larval development of Macquana colonorum and M. novemaculeata 



187 



Pelvic-fin buds appear in postflexion larvae from 6.3 

 mm, but no elements have formed in the largest speci- 

 men; they are all ossified in the transitional juveniles. 

 All primary caudal-fin rays are ossified by the end of 

 notochord flexion. Procurrent caudal rays are present in 

 the transitional juveniles. Notochord flexion commences 

 before 4.8 mm, and is complete by 5.7 mm. Scales have 

 not begun to develop in the largest transitional juvenile 

 examined (13.5 mm). 



Pigment (Fig. 1, A-D) Larvae are moderately to heav- 

 ily pigmented; melanophores are concentrated on the 

 dorsal and ventral midlines, and midlateral surface of 

 the trunk and tail. Small expanded melanophores are 

 present at the tips of the upper and lower jaws, and 

 there are one or two melanophores ventral to the nasal 

 pit. Additional internal melanophores are present along 

 the roof of the mouth, and posterior to the eye below 

 the mid- and hindbrain. External melanophores may 

 be present on the operculum in line with the eye. One 

 or two melanophores are present on the ventral midline 

 of the lower jaw, and there is one at the angle of the 

 lower jaw. 



Four to seven large, expanded melanophores are pres- 

 ent along the dorsal midline of the trunk and tail, from 

 the nape to just posterior to the dorsal-fin base. There 

 are one or two melanophores on the nape and four or 

 five along the dorsal-fin base. A series of large, expand- 

 ed melanophores is present along the lateral midline of 

 the trunk and tail, commencing at the gas bladder and 

 extending to the posterior end of the dorsal and anal 

 fins. In postflexion larvae, this series extends onto the 

 anterior third of the caudal peduncle. Internal melano- 

 phores are present over the gas bladder, the mid- and 

 hindgut, and may be present along the notochord. The 

 external and internal pigment series thus give the im- 

 pression of a line of heavy pigment from the tip of the 

 snout, across the head and trunk, to the tail. 



Small melanophores are present along the ventral 

 midline of the gut; one melanophore on the isthmus 

 immediately anterior to the cleithral symphysis, usually 

 three (range: 2-4) melanophores between the cleithral 

 symphysis and pelvic-fin base, and usually three (range: 

 1-4) melanophores between the pelvic-fin base and the 

 anus. Expanded melanophores are present along the 

 ventral midline of the tail, from above the anus to the 

 posterior end of the anal-fin base. Between one and 

 three melanophores occur along the anal-fin base. A 

 small melanophore is occasionally present in early post- 

 flexion larvae at the base of ventral primary caudal-fin 

 rays 1-2. 



In transitional juveniles, the expanded melanophores 

 are relatively smaller, and are most prominent midlat- 

 erally along the trunk and tail. The expanded melano- 

 phores along the dorsal and ventral midlines become 

 small to absent during the juvenile stage. Additional ex- 

 panded melanophores develop laterally on the head and 

 body, and the dorsal and anal fins become pigmented. 

 Small melanophores cover the head and body — coverage 

 lightest ventrally on the head and gut. Three broad 



vertical bands become apparent dorsally on the nape, 

 below the center of the spinous dorsal fin and below the 

 center of the soft dorsal fin by 13.5 mm. 



Development of Macquaria novemaculeata larvae 



Adult meristic data D VIII-X,8-11; A 111,7-9; Pj 12-16; 

 P 2 1,5; Vertebrae 25; 38 specimens: 3.3-14.1 mm BL 



Eggs and hatching Eggs are approximately 900 pm 

 in diameter and have multiple oil globules. Larvae are 

 3.3 mm SL at time of hatching. 



General morphology (Tables 3 and 4, Fig. 2) Yolksac 

 and early preflexion larvae are elongate (BD 15-18%), 

 but in late preflexion and flexion larvae, body depth 

 becomes moderate (BD 26-34%). Body depth of field- 

 caught postflexion larvae ranges from 29%. to 35%, 

 and in transitional juveniles from 33% to 34%. Reared 

 postflexion larvae and transitional juveniles are deeper 

 than wild larvae, ranging from 32% to 44%, which is an 

 artifact of the extremely full guts in the reared larvae. 

 Body depth decreases abruptly posterior to the anus, 

 although this becomes less marked with development. 

 The head and body are laterally compressed. There 

 are 25 myomeres (10-13 preanal+12-15 postanal). In 

 general, there are 10-12 preanal myomeres in preflex- 

 ion and flexion larvae, and 12-13 preanal myomeres in 

 postflexion larvae and transitional juveniles. The gut 

 is initially straight in yolksac larvae but is coiled by 

 3.9 mm. The gut is oval to triangular in shape; preanal 

 length reaches 44-56% of BL in yolksac and preflexion 

 larvae, 54-60% in flexion stage larvae, and 54-66% in 

 postflexion larvae and transitional juveniles. The gut 

 mass is large, particularly in reared postflexion larvae 

 and transitional juveniles. The conspicuous gas blad- 

 der, which is located over the midgut, is moderate to 

 large in size, except in the yolksac larvae where it is 

 small and inconspicuous. The head is round and small 

 in yolksac larvae (HL 15-16%), moderate in preflexion 

 larvae (HL 22-31%), and becomes moderate to large in 

 flexion (29-35%) and postflexion larvae and transitional 

 juveniles (32-38%). The snout is always shorter than the 

 eye diameter and is initially concave, but becomes convex 

 to straight in postflexion larvae. The eye is moderate to 

 large (27-36% of HL) but is relatively larger in yolksac 

 larvae (42-45% of HL). The eye is initially unpigmented, 

 but is fully pigmented by 3.6-3.8 mm, prior to the com- 

 plete absorption of the yolk. The moderate mouth reaches 

 to the middle of the pupil. Small canine teeth appear 

 in both jaws in late preflexion larvae by 4.4 mm. The 

 number of teeth increases with development. The nasal 

 pit begins to close by 8.6 mm, and both nostrils are 

 developed by 10.3 mm. 



Head spination is weak. A small spine appears at 

 the preopercular angle by the end of the preflexion 

 stage. By the time notochord flexion is complete, there 

 are three spines on the posterior preopercular border, 

 and the spine at the angle is the longest. All spines 

 are shorter than the pupil diameter. Additional spines 



