EARLY STAGES OF PINK SHRIMP FROM FLORIDA WATERS 



331 



FiGUBE 10. — Ventral view of fifth nauplius. 



disting;uishable in this stage. In addition, the 

 mandible has lost its endopod and all but a small 

 portion of its exopod. Its masticatory surface 

 has, however, developed considerably. During 

 this stage the larvae cease living on yolk and 

 begin to seek nourisliment in the water. 



The ocellus persists in the midline between the 

 developing compound eyes. Just posterior to the 

 ocellus the two large lobes of the liver, which is 

 dorsal to the mouth, can be seen in ventral aspect. 

 The labrum is conspicuous as a roughly oval struc- 

 ture located ventrally in about the middle of the 

 area covered by the carapace. Its posterior or 

 free edge has a slight notch at the midline which 

 is provided with short bristles, and the anterior 

 edge is marked by a well-developed spine. The 

 two lobes of the labium extend from under the 

 labrum and have bristles along their median 

 borders. The greater portion of the mandible 

 consists of an irregularly shaped median mastica- 

 tory lobe, which bears 6 to 8 small teeth and 3 

 or 4 larger ones, and a lateral rounded lobe, which 

 bears a trace of the exopod. 



The caudal f urcae each bear 7 spines, as in the 

 preceding stage. The spines have setules, except 

 for the most external spine which is smooth. This 

 external spine originates from the dorsal surface 

 rather than from the lateral, terminal, or median 

 surfaces of the furca, as do the other spines. 



The first antenna is divided into three major 

 parts. Tlie basal portion bears 2 setae along its 

 anterior margin. The middle portion beare 1 long 

 seta on its anterior margin. The distal portion 

 bears 1 dorsal and 3 terminal setae and, in addi- 

 tion, 1 short seta on its posterolateral margin. 

 This is a total of 8 setae on the first antenna. 



The protopod of the second antenna is 3-seg- 

 mented and bears no setae. The endopod has 2 

 segments, the basal segment bearing 2 setae. Two 

 additional setae are present at the junction of the 

 2 segments of the endopod. The distal segment 

 bears 5 setae, making a total of 9 setae for this 

 ramus. The exopod of the second antenna is di- 

 vided into about 10 segments and bears 7 setae 

 on its anterolateral and 2 on its posterolateral mar- 

 gins, as well as 4 terminal setae. 



