ABOUSSOUAN AND LEIS: BALISTOIDEI 



453 



Fig. 244. Scanning electron micrograph of the sculptured chorion 

 of an unidentified Hawaiian ostraciid egg. The micropyle is the hole in 

 the center. The width of the field of bumps is cci. 0.5 mm. 



Fig. 245. Triacanthid and ostraciid yolk-sac larvae from top to bot- 

 tom: Triacanthus hiaculeatus. 1.3 mm ( 1 .4 mm TL) after Ohsima and 

 Nakamura. 1941; and Acanthostracion quadricornis. 2.6 mm reared 

 larva from Rorida. Specimen is fully enclosed in a vesicular sac which 

 is most inflated over head and trunk. The vesicles are omitted in the 

 drawing. Specimen is unpigmented, but is probably bleached. 



where the posterior rays of dorsal and anal fins are slow to form, 

 ossification of all elements of the fin could serve as an equally 

 good definition. The fins will be indicated by standard notation 

 (D— dorsal, Dsp— dorsal spine, etc.). The order of the letters 

 corresponds to the order of formation. An equal sign between 

 two letters indicates the fins form simultaneously, a dash in- 

 dicates the fins do not form simultaneously. 



Triacanthodidae 



The eggs of triacanthodids are unknown, although there is a 

 dubious report of pelagic eggs (Nikol'skii, 1961). The body of 

 preflcxion and flexion larvae (Fig. 247) is moderately to very 

 deep, moderately wide in head and trunk, and compressed in 

 tail. The body becomes more compressed and elongate with 

 growth, but may remain very deep until well after flexion. The 

 gill opening is closed to a pore in the smallest available speci- 

 mens (late preflexion). There is no dermal sac. The fins form 

 D = A = P,-C-P, = Dsp. The Dsp anlage and P, buds do not 

 form until after flexion. Although no early postflexion larvae 

 are available, late flexion larvae have a notochord with a long 

 posterior portion that probably indicates that the notochord has 

 an extended tip for awhile following flexion. Dermal spinules 

 first form in preflexion larvae, and appear first on side of head 

 (cheek, operculum, over otic vesicle) and laterally on two small 

 regions of the gut (ventral to P, base and just anterior to anus). 

 The spinules are unspecialized, and fully cover the body of 

 postflexion larvae. The available larvae of Atrophacanthus are 



unpigmented, but their poor condition implies they could be 

 faded. The Macrorhamphosodcs (?) larva is moderately and uni- 

 formly pigmented with small melanophores. 



The specimen identified as Triacaruhodes sp. by Weber (1913) 

 appears to be a trichiurid (Scombroidei), not a triacanthodid. 



Tyler (1968) describes juvenile development of several tria- 

 canthodid species. 



Triacanthidae 



Triacanthid eggs lack oil droplets and chorion sculpture, are 

 pelagic, small, and hatch in about 22 hours (Table 1 16). De- 

 velopment at hatching is not advanced (Fig. 245): no jaws or 

 pectoral fins are present, the eye is unpigmented and much yolk 

 remains. The body is cylindrical at hatching and becomes much 

 deeper with growth (Fig. 247) and, especially following flexion, 

 very compressed. The gill opening closes to a pore prior to 

 flexion. There is no dermal sac. The fins form D = A = P|-P; = 

 Dsp-C. The notochord has an extended tip following flexion. 

 The D and P, spines become relatively elongate. Dermal spi- 

 nules first form in preflexion larvae and appear first on the sides 

 of the head (cheek, operculum, over otic vesicle), and laterally 

 on the posterior portion of the gut. The spinules are unspecial- 

 ized (except for some terete ones on the fin spines), and fully 

 cover the body shortly after flexion. Pigment is heavy on brain 

 and gut. and a single ventral tail melanophore is present. Fol- 

 lowing yolk exhaustion, pigment spreads over most of the body 

 in a blotchy pattern. 



