FISHERY BULLETIN: VOL. 69. NO. 1 



mouth parts and other appendages were taken 

 from two individuals representing each sub- 

 stage. Setules on the setae of the larvae were 

 deliberately omitted, and nauplial appendages 

 were rotated on their axes to avoid cluttering 

 the figures and obscuring important diagnostic 

 characters. 



Abbreviations used in the text are: TL = 

 total length, including rostrum when present but 

 excluding caudal spines; W = body width at 

 the point of greatest width; CL = carapace 

 length, including the rostrum; and N = the 

 number of specimens examined. 



DESCRIPTION OF 

 DEVELOPMENTAL STAGES 



EGG AND HATCHING 



(Fig- 1) 

 Diameter 0.26 mm 



Viable eggs are round, golden brown, and 

 translucent. As the nauplius develops, it fills 

 the egg case and can be seen moving sporadically. 

 At hatching, the egg case splits and the posterior 

 portion of the nauplius protrudes. Then the 

 nauplius, unmoving, appears to swell until it is 



forced from the shell, the entire process taking 

 about 30 sec. 



When first hatched, the nauplius rests almost 

 motionless for 3 to 5 min. Although the ap- 

 pendages do not move during this time, spastic 

 movement can be seen within the body near the 

 base of each appendage. Suddenly the nauplius 

 folds its appendages posteriorly along the ven- 

 tral margins of the body, and, in one quick move- 

 ment, sheds from its posterior end a loose-fitting 

 exoskeleton and starts swimming actively. At 

 fii-st, the nauplius alternates 2- to 3-sec periods 

 of swimming with resting periods of equal 

 duration. 



NAUPLIUS I 



(Fig- 2) 

 Mean TL = 0.35 mm (0.32-0.38 mm) 

 Mean W =0.19 mm (0.18-0.21 mm) 



N = 55 



The pyriform body is unsegmented and pos- 

 sesses a ventrally projecting labrum. An ocel- 

 lus, which persists in subsequent nauplial sub- 

 stages, is present near the anterior end. The 

 dorsal surface of the body is smooth except for 

 a small median spine posteriorly (Fig. 2b). The 

 posterior portion of the body is rounded and 

 bears a single pair of caudal spines. 



The body color in all nauplial substages is a 



Figure 1. — Nauplius emerging from egg. 



Figure 2. — Nauplius I : a, ventral view ; b, lateral view. 



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