COOK and MURPHY : DEVELOPMENTAL STAGES OF BROWN SHRIMP 



Figure 6. — Nauplius V, ventral view. 



Setation of appendages: 



First antenna: Two short and one medium 

 ventrolateral; two long 

 and one medium termi- 

 nal; two medium and 

 one short dorsolateral. 



Second antenna: 

 Endopod: 



Exopod: 



Mandible: 



Two short and one medium 

 ventrolateral; one me- 

 dium and three long 

 terminal. 



Five long ventrolateral; 

 three long and one short 

 terminal. 



Same as Nauplius I. 



PROTOZOEA I 



(Fig. 7) 

 Mean TL = 0.96 mm (0.89-1.21 mm) 

 Mean CL = 0.45 mm (0.40-0.49 mm) 



N = 40 



With the molt from Nauplius V to Protozoea 

 I, the larvae change radically. A large, loose- 

 fitting carapace covers the anterior portion of 

 the body. The narrow posterior portion is di- 

 vided into a six-segmented thorax and an un- 

 segmented abdomen. The masticatory surface 

 of the mandible has become greatly enlarged, 

 and the endopod and exopod have been lost. The 

 maxillae and maxillipeds are large and func- 

 tional. 



The carapace is rounded with a median notch 

 at the anterior end; two rounded frontal organs 



are the only protuberances on it. An ocellus, 

 which persists in subsequent protozoeal sub- 

 stages, is present between a pair of compound 

 eyes covered by the carapace. The labrum is 

 smaller than in the preceding stage and has a 

 short spine on its anterior mai'gin. Two lobes 

 of the labium, with short bristles on their in- 

 ner margins, are posterior to the labrum. The 

 mandibles curve inward and several of their 

 teeth can be seen between the labrum and 

 labium. 



The first antenna, which is about equal in 

 length to the endopod plus the protopod of the 

 second antenna, is composed of three major seg- 

 ments. The basal segment is divided into five 

 subsegments and bears one short seta. The 

 second segment possesses three setae, two ven- 

 trolateral, and one posterolateral. The distal 

 segment has three terminal and three subter- 

 minal setae. 



The second antenna consists of a protopod of 

 three segments, an endopod of two segments, 

 and an exopod of 10 segments. The endopod 

 bears one seta at the juncture with the protopod, 

 another on the first segment, two at the juncture 

 of the first and second segments, and five ter- 

 minal setae on the distal segment. The exopod 

 has eight setae on its ventrolateral and two on 

 its dorsolateral margins, as well as three ter- 

 minal setae. 



The mandible has lost its exopod and endopod. 

 The masticatory surface now faces medially and 

 has several rings of teeth. 



The first maxilla is composed of an unseg- 

 mented protopod, an endopod of three segments, 

 and a small knoblike exopod. The protopod con- 

 sists of two large lobes, each bearing several 

 stout, toothed spines. The first segment of the 

 endopod possesses two or three setae; the sec- 

 ond, two; and the distal, five. The exopod bears 

 four setae. 



The second maxilla is about the same size 

 as the first. It has an unsegmented protopod, 

 an endopod of four segments, and a knoblike 

 exopod. The protopod has five lobes on its 

 ventral margin; the basal lobe bears approxi- 

 mately eight setae, the remainder three to six. 

 The first three segments of the endopod each 



227 



