EARLY STAGES OF PINK SHRIMP FROM FLORIDA WATERS 



327 



FiGUKE 5. — Photomicrograph of first naupllus soon after 

 hatching. 



fifths of the distance from the body. Although 

 setation of the first and the second appendage 

 varies in the different nauplial stages, that of the 

 mandibles remains constant 



During the nauplial stages, the larva© feed on 

 yolk granules, which, because of their opaqueness, 

 can easil}^ be seen in the transparent body of the 

 nauplius. The description of locomotion in the 

 nauplius of P. setifenis (Pearson, 1939) and P. 

 jnponicu.'i (Hudinaga, 1942) was found to liold 

 true for P. duorarum. The nauplius swims 

 upward by a rapid beating of its appendages, 

 which lasts approximately 5 seconds; after that 

 the nauplius sinks dorsal side down with its ap- 

 pendages extending upwards. This period of in- 

 activity lasts several times longer than the period 

 of activity, being from 15 to 30 seconds in 

 duration. 



SECOND NAUPLIUS 



Specimens of the second nauplius (fig. 6) meas- 

 ured 0.40 to 0.45 mm. in length and 0.18 to 0.20 mm. 

 in body width. The major differences between this 

 stage and the preceding one are in the setation of 

 the first and second antennae, the appearance of 

 setules on tlie longer setae, and a sliglit cliange in 

 the shape of the body. The description of the 

 second nauplius is based on 27 specimens raised 

 from eggs. 



The single pair of f ureal spines found in the 

 first nauplius is still present, and no others have 

 been added. The dorsomedian spine near the 

 posterior end > 5 the body is no longer present. 



The first antenna bears 3 lateral setae, 2 of 

 which are short and 1 is of moderate length; also 

 3 terminal setae, 1 of which is long, 1 moderate, 

 and 1 short. 



A short terminal seta has replaced the bud pres- 

 ent in the preceding stage on the endopod of the 

 second antenna. A short terminal seta is also 

 added to the exopod of this appendage, making 

 a total of 3 lateral and 3 terminal setae. The num- 

 ber of setae on the exopod of the second antenna 

 increases by 1 in each successive nauplial stage 

 and the setation of this appendage is therefore 

 an excellent characteristic for differentiating be- 

 tween the various stages. 



The endopod and exopod of the mandible con- 

 tinue to bear 3 long setae each, in the same posi- 

 tion as in the preceding stage. 



FiGUBE 6. — Ventral view of second nauplius. 



