454 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



Fig. 246. Balistid and monacanthid yolk-sac larvae from top to 

 bottom: Sufflainen chrysopterus. 1.7 mm reared larva from the Great 

 Barrier Reef (24 hours after hatching); Stephanolepis cirrhtfer. 1.9 mm 

 (2. 1 mm TL) after Fujita, 1955; and Anacanthns harbalus. 2.4 mm larva 

 from a Great Barrier Reef plankton sample (age unknown). Note anlage 

 of dorsal fin spine in occipital region. Mouth is not fully formed. Frag- 

 mented oil droplets are present in the yolk sac. but are not illustrated. 



The descriptions of lai^ae identified as Triacanthus breviros- 

 tris by Kuthalingam ( 1 959b) do not resemble triacanthid larvae 

 in morphology, sequence of development, or size. One can only 

 conclude the larvae are misidentified and the drawings inac- 

 curate. The eggs identified by Kuthalingam (1959b) as Tria- 

 canthus brevirostris are probably those of an atheriniform fish. 



Tyler (1968) describes juvenile development of several tria- 

 canthid species. 



Bahstidae 



Balistid eggs are demersal, small, lack chorion ornamentation 

 (but are adhesive), have a single oil droplet (Table 1 16), and 

 hatch in one to two days. Eggs are laid in clusters in shallow 

 nests on sand or rubble bottoms and are guarded by the adult. 

 Development of larvae at hatching is not advanced: no jaws are 

 present, the eye is unpigmented, minimal body pigment is pres- 

 ent and much yolk remains (Fig. 246). Larvae have a cylindrical, 

 slightly compressed body at hatching. The body quickly be- 

 comes deeper and then moderately rotund in the trunk (Figs. 

 248 and 249). The tail remains compressed. About the time fins 

 start to form, the larva starts to become compressed and this 

 increases thereafter. In newly hatched larvae, a slightly inflated 

 area is present surrounding the trunk (Fig. 246), but it contains 

 no vesicles, and soon disappears. The gill opening closes to a 

 pore just prior to flexion. The fins form Dsp-D = A = P,-C. 



Fig. 247. Late preflexion larvae of three balistoid families. Small 

 ticks on upper and middle specimens indicate position of dermal spi- 

 nules. From top to bottom: Atrophacanlhus japonicus (Triacanthodi- 

 dae), composite drawing of three damaged larvae (2.6-2.7 mm) from a 

 Dana Station in the Philippines; unidentified triacanthid. 3.5 mm, from 

 the Great Barrier Reef note small dorsal spine and pelvic fin bud; and 

 Acanlhostracion QuaiJricornis (OsUaciidae). 3.3 mm. reared larva from 

 Florida. The dermal plates arc not yet formed, but ridges on the body 

 are evident. 



The first dorsal spine becomes large and heavily armed with 

 barbs before flexion. This ornamentation varies between species 

 and is useful in identification. The notochord has an extended 

 tip for a short while following flexion. Dermal ossifications first 



