More than six setae on exopod of second antenna; 

 usually three or more pairs of caudal spines; 

 surface of body between insertion of caudal spines 

 concave 5 



5(4) Seven setae on exopod of second appenadge; 

 usually three, sometimes four, pairs of caudal 

 spines; surface of body between insertion of caudal 

 spines slightly concave; no swelling at base of 



mandible Nauplius III (fig. lc) 



More than seven setae on exopod of second 

 antenna; usually more than four pairs of caudal 

 spines; surface of body between insertion of 

 caudal spines deeply concave; base of mandible 

 swollen 6 



6(5) Eight setae on exopod of second antenna; usually 

 five, sometimes six, pairs of caudal spines; slight 

 swelling at base of mandible; endopod of mandible 

 never transparent; rudimentary ventral append- 

 ages posterior to third appendages 



Nauplius IV (fig. Id) 

 Nine setae on exopod of second antenna; usually 

 seven, sometimes six, pairs of caudal spines; large 

 subcorneal protuberance at base of mandible; 

 endopod of mandible frequently transparent; 

 ventral appendages prominent 



Nauplius V (fig. le) 



7(1) Large, prominent, carapace followed by a slender 

 segmented thorax and an abdomen which may or 

 may not be segmented; two pairs of prominent 

 appendages arising from anterior portion of body, 

 the first unbranched, the second branched; 



prominent labrum present (Protozoea) 8 



Not as above 11 



8(7) Carapace does not completely cover thorax; 

 abdomen bifurcate posteriorly, with each furca 

 bearing at least seven spines; biramous first and 



second maxillipeds well developed, the third 

 absent or present only as a rudiment; usually, no 

 spines arise from posterior half of carapace; if 

 spines present, a dorsal organ (fig. 2d) is present 



(Penaeid protozoea fig. 2) 9 



One or more of the following characters present: 

 carapace completely covers thorax; abdomen not 

 bifurcate; caudal furcae bear less than seven 

 pairs of spines; first and second maxillipeds not 

 well developed or third maxilliped well developed; 

 if numerous spines arise from posterior portion of 

 carapace, dorsal organ not present 



Nonpenaeid protozoea 

 9(8) Eyes sessile, beneath carapace; pereiopods 

 absent; abdomen unsegmented 



Protozoea I (fig. 2a) 

 Eyes stalked ; pereiopods present at least as small 

 buds; abdomen segmented 10 



10(9) Uropods not present externally, may be seen 

 beneath cuticle; pereiopods present only as small 

 buds; first five abdominal segments without dorsal 



spines Protozoea II (fig. 2b) 



Uropods present externally; pereiopods rudimen- 

 tary, but biramous and prominent; first five 

 abdominal segments with dorsal spines 



Protozoea III (fig. 2c) 



11(7) Carapace closely fitting with a rostrum that 

 extends anteriorly between the eyes; five pairs 

 of biramous pereiopods present, with the exopods 

 elongate and bearing numerous setae which make 

 them appear brushlike; six-segmented abdomen 

 followed by telson and biramous uropods; 

 pleopods, if present, rudimentary and non- 

 functional (Mysis) 12 



Carapace closely fitting with a rostrum extending 

 anteriorly between the eyes; five pairs of pereio- 



1 |s| flntrpina 



2 Endopod 2d Antenna 



3 EiOpod 2d Antenna 



4 Labrum 



5 labtal Sp.ne 



6 Mandible 



7 l-.t&2d Ma.illj 



8 1st, 2d 4 3d Ma.tltped 



9 Telson 



Figure 2. — Penaeid protozoeae: a, Protozoea I; b, Protozoea II; c, Protozoea III; d, Protozoea III, carapace. 

 440 U.S. FISH AND WILDLIFE SERVICE 



