FISHERY BULLETIN: VOL. 87, NO. S. 1989 



Figure 16. — Second antenna of postlarvae. (a) Penaeus, (b) Metapenaeus, (c) Trachypenaeus, (d) Metapenaeopsis, (e) 



Atypopenaeus. Scale = 0.1 mm. 



vae from other families within the superfamily 

 Penaeoidea might occur with penaeids. Charac- 

 teristics that can identify larvae of related fam- 

 ihes are described by Cook (1966a) and Dall et al. 

 (in press). 



The key is not useful for later postlarval 

 stages. It is difficult to define the cutoff point for 

 older postlarvae, but the following character- 

 istics may indicate that the postlarva is too old 

 for accurate identification: there are more than 4 

 rostral spines; the antennal flagellum is longer 

 than half the body length; the telson has a pro- 

 nounced V-shape; and there are many setae on 

 the telson. 



Key 



Protozoea 



1 Setal formula on 2nd antennal protopod 



and endopod l-t-H-2 Penaeus 



2nd antennal formula 0-1-1+2 



Macropetasma 



2nd antennal formula not l-t-1+2 or 

 0-Hl-h2 2 



2(1) 2nd antennal formula 0-^24-2 3 



2nd antennal formula H- 2 -I- 2 or 



1-H2-H3 5 



3(2) 2nd antennal exopod with 11 setae on 



inner margin Parapenaeiis 



2nd antennal exopod with 10 setae on 



726 



inner margin 



4(3) Dorsal surface of carapace with small 

 hump; telson notch moderately wide 



(Fig. 17c, i) Trachypenaeus 



Dorsal surface of carapace smooth; tel- 

 son notch very wide (Fig. 17f, 1) 



Parapenaeopsis 



5(2) Eyes immobile (protozoea I) 6 



Eyes mobile (protozoea II or III) 9 



Protozoea I 



6(5) Strong spines above frontal organs, 

 length at least 0.7 of 1st antenna diam- 

 eter (Fig. 8a) Metapenaeopsis 



Spines above frontal organs small or 

 missing 7 



7(6) 2nd antennal exopod with 11 setae on 



inner margin Parapenaeus 



2nd antennal exopod with 10 setae on 

 inner margin 8 



8(7) Carapace about 0.5 of total length; 

 usually small spines above frontal 



organs Metapenaeus 



Carapace about 0.4 of total length; no 



spines above frontal organs 



Atypopenaeus 



9(5) Uropods absent (protozoea II) 10 



