456 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



■BSCor- 



Fig. 249. Balistid preflexion larva Xanlichthys ringens 3.87 mm, ASFIOl, western Atlantic. 



particularly in comparison with other tetraodontiform families. 

 Leis and Rennis (1983) considered that three distinct morphs 

 were present among larval monacanthids. However, our studies 

 of additional taxa indicate that Morphs A and B of Leis and 

 Rennis (1983) are merely extremes (Fig. 248), and that no clear 

 division can be made between A and B. For example, while Leis 

 and Rennis (1983) utilized seven characters to separate the two 

 morphs, larvae of Alutera sp. (Fig. 250) have three 'A' char- 

 acters, three 'B' characters, and are intermediate for the seventh. 

 Morph C of Leis and Rennis (1983) (Fig. 248) is distinct from 

 the combined Morph AB (Table 1 17). Rapid changes in body 

 proportions may take place in many species. Morph AB larvae 

 are compressed and become more so with growth, while Morph 

 C larvae are moderately broad in gut and head, but become 

 compressed with growth. The gill opening closes to a pore late 

 in the preflexion stage, and the position of the pore relative to 

 the eye varies with species. The dorsal spines form at a very 

 early stage in Morph AB larvae, but are the last fin elements to 

 form in Morph C larvae. In some species, the first spine becomes 

 heavily armed by the mid-preflexion stage. The pelvis may form 

 either early and be prominent by the mid-preflexion stage or 

 very late and may never become externally visible, depending 

 on species. The sequence of fin development is morph-depen- 

 dent (Table 1 17). There is no dermal sac. The notochord tip is 



long and persists for a time following flexion. If present (Morph 

 AB), the small cluster of spinules on the preoperculum (a larval 

 specialization) forms very early and is lost before flexion. De- 

 pending on species, dermal spinules may first appear laterally 

 on the gut and head, or on the forehead and along the ventral 

 midline near the cleithral symphysis. Dermal spinules cover the 

 body prior to flexion or shortly thereafter. Pigment is heavy on 

 the brain and over the gut, but on the tail, it varies with species. 



Several species temporarily develop small, pigmented flaps 

 or filaments (a larval specialization) on different portions of the 

 body. Alutera sp. (Fig. 250) develops an elongate flap which 

 originates on the operculum near the preopercular spinule clus- 

 ter; Pseudaliiiaris nasicornis (Fig. 248) develops several, elon- 

 gate tendrils laterally on the tail; and many species develop a 

 filament at the terminus of the pelvic bones (Fig. 248). The 

 latter possibly represents a pelvic fin bud that atrophies. 



The description of Slephanolepis hispidus by Hildebrand and 

 Cable ( 1 930) seems to be based on more than one monacanthid 

 species (Martin and Drewry, 1978). Berry and Vogelc (1961) 

 describe the juvenile development of several monacanthid 

 species. 



Hildebrand and Cable (1930) state that the pelvis oi' Sleph- 

 anolepis hispidus possibly forms through coalescence of two 

 separate fin buds. In the material available to us (Table 1 16), 



