JACKSON ET AL.: KEY TO GENERA OF PENAEID LARVAE 



Metapenaeopsis has more species than any other 

 penaeid genus found in the Indo-west Pacific 

 region (Dall et al. in press), oui- key is based on 

 just 2 species, both from our own reference col- 

 lection. Characteristics of the genera Atypo- 

 penaeus, Parapenaeopsis, and Parapenaeus 

 have been based on a single species. For this 

 reason, and because the genera Heteropenaeus, 

 T)-achype)iaeopsis, and Petiaeopsis have been 

 omitted, the key must be regarded as provi- 

 sional, and subject to revision as more descrip- 

 tions are published. 



The protozoeae of Metapenaeus, Atypo- 

 petiaeus, and Metapenaeopsis, and Para- 

 penaeus are veiy similar. For protozoea II and 

 III, distinction between these genera rehes on 



the shape of the telson, rostrum, and supraor- 

 bital spines. These characters should be assessed 

 with reference to Figures 17 and 18 and, if there 

 is any doubt, the suite of characteristics in Table 

 3. In most cases the characters used in the key 

 should be sufficient to identify mysis larvae and 

 postlarvae without difficulty. However, as an 

 additional check, the general shape of the anten- 

 nal blades is a useful generic character, and 

 should be compared with those shown (Fig. 16). 

 The family Penaeidae no longer includes mem- 

 bers of the Aristaeidae, Solenoceridae, Serges- 

 tidae, or Sicyoniidae; these are now separate 

 families within the superfamily Penaeoidea 

 (Bowman and Abele 1982). We have restricted 

 oui- key to the family Penaeidae. However, lar- 



Table 3. — Characteristics of protozoeal stages of the genera Atypopenaeus, Metapenaeopsis. Metapenaeus, and Para- 

 penaeus. Sources of information: Atypopenaeus. Metapenaeopsis. Metapenaeus — present study and reference collection 

 of larvae held by the authors; additional sources for Metapenaeus species — see Dall et al. (in press) for review; specific 

 sources referenced in table — Parapenaeus stylifera - 'Heldt 1938, ^Pearson 1939; Metapenaeus monoceros - ^Couriies 

 1976, ■'Raje and Ranade 1972. 



Protozoea III 

 Number of setae on 



2nd antenna exopod 



inner margin 

 2nd antennal setal 



formula 

 Rostrum 

 Supraorbital spines 



Telson spines 



9-10 



1+2 + 2 



10-11 



1+2 + 2or 1+2+3 



M. monoceros^^ 



(inner much smaller 



than outer) 



10 



ll^or 12' 



1+2+2 or 1+2 + 3 + 2+2' or 1 +2+3^ 



longer than eye longer than eye, curved about eye length longer than eye 



one one plus rudiment one two (inner smaller 



of second than outer) 



(Fig. 10a,) 



7+7 7+7 7+7 8 + 8 



725 



