548 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



Table 133. Acanthuroid Taxa for Which Information is Available on Ego and Larval Stages. YS— yolk-sac; pre— preflexion; flex- 

 flexion stage; post — postflexion stage; D— demersal; P— pelagic. 



Number of 

 species 



Larvae— developmental stage 



Egg type 



Pre 



Flex 



Acanthuridae 



Acanihurus 



Zanclidae 



Zanchis 



X 

 X 



X 

 X 



X 

 X 



Lutken, 1880; Breder. 1927; Whitley 

 andColefax, 1938; Randall, 1956, 

 1961; Aboussouan, 1965; Burgess, 

 1965 



Randall, 1955c 



Fourmanoir, 1976; Leis and Rennis, 

 1983 



Randall, 1955b; Aboussouan, 1966a 



Dekhnik et al., 1966 (Fig. 37-1, misiden- 

 tified as Balistidae); Randall, 1955c; 

 Nellen, 1973b; Watson and Uis, 1974 



Roule, 1924; Roule and Angel, 1930; 

 Blache, 1964 



Fujita and Ueno, 1954; Uchida et al., 

 1958; Mito, 1966; Popper etal., 1973; 

 May et al., 1974; von Westemhagen 

 and Rosenthal, 1975, 1976; Bryan and 

 Madrisau, 1977; Leis and Rennis, 

 1983 



Strasburg, 1962 



(Tyler, 1970). Table 132 summarizes meristic characters of the 

 suborder, and Table 133 reviews current state of knowledge of 

 its early life history. 



Development 



Siganids have small (< 1 mm) demersal eggs with oil droplets 

 (Table 133). No parental care has been recorded. Larvae hatch 

 in a poorly developed condition. Moderately long preopercular 

 spines and serrate ridges form on the head, and the first fin 

 elements to form— the pelvic spine and second dorsal spine— 

 form very early (Fig. 296). The body does not become very 

 deep, and although the pelvic and dorsal spines are elongate 

 and serrate, they do not exceed three times the eye diameter. 

 No scales form prior to settlement, but the pelagic stage may 

 grow to 30 mm and is very silvery in life, particularly over the 

 gut. Early larvae, in particular, are very percoid in appearance. 

 Figment in preflexion larvae is limited to dorsal and pelvic fin 

 membranes, gut, and a ventral series on the tail. Older larvae 

 are more heavily pigmented. 



Acanthurids have small (< I mm) pelagic eggs with a single 

 oil droplet (Table 133). Larvae hatch in a poorly developed 

 condition, but very soon develop serrate ridges on the head (but 

 no elongate preopercular spines form). The first fin elements to 

 form (the pelvic spine and second dorsal spine) do so very early, 

 and these are quickly followed by the second anal spine (Fig. 



296). These fin spines are serrate, and at least one exceeds three 

 times the diameter of the eye. The head and trunk become 

 remarkably deepened. This is accentuated by the elongate pel- 

 vic, dorsal, and anal spines at the opposite edges of the deepest 

 point of the body: the body becomes distinctly kite-shaped. 

 Small, triangular scales arrayed in vertical rows begin to form 

 shortly after flexion. The pelagic stage may reach 60 mm and 

 is very silvery in life around the gut. Preflexion larvae are lightly 

 pigmented in specific patterns. Late larval stages may acquire 

 aspects of the juvenile pigment pattern. The caudal peduncle 

 armature forms late in the larval period. In Naso the spines form 

 from existing scales (i.e., they pass through an unspecialized 

 scale stage). In Acanihurus it forms directly without the unspe- 

 cialized scale stage. 



Nothing is known of luvarid or zanclid eggs or preflexion 

 larvae (Table 133). Luvarus larvae apparently have early-form- 

 ing pelvic and anterior dorsal fin spines. They also have early- 

 forming scales, serrations on the head, but lack elongate pre- 

 opercular spines (Fig. 297). The dorsal and pelvic spines of 

 Luvarus are more than three times the diameter of the eye. 

 Luvarus larvae are deep-bodied, but not as kite-shaped as acan- 

 thurids, and have a more square-shaped head. With growth, the 

 spines of the fins, and many of the soft rays are lost, and the 

 body becomes more fusiform. Late Zanclus larvae are very 

 similar to acanthurid larvae (Fig. 297) and are scaled similarly. 



Fig. 296. Urvae of (upper) Acanihurus sp., 6.0 mm SL, OREGON II cr. 7343, sta. 87, Caribbean Sea, 16''54'N. 062°03'W, February 16. 

 1973, drawn by J. C. Javech; (middle) Naso unicornis. 5.9 mm SL, PROVIDENCE II, st. T-429, Indian Ocean, 09°27'S, 050°2rE, December 

 18, 1974, drawn by J, C. lavech; and (lower) Siganus fuscescens, 5.4 mm TL, modified after Uchida et al. (1958). 



