EARLY STAGES OF PINK SHRIMP FROM FLORIDA "WATERS 



333 



The mandible has lost its endopod and all but 

 a trace of its exopod, has a well-developed masti- 

 catorj' surface, and lies dorsal and posterior to 

 the labrum. 



The first and second maxillae and first and sec- 

 ond maxillipeds are well developed and become 

 functional in this stage. 



The first maxilla consists of a protopod of 2 

 segments, an endopod of 3 segments, and a budlike 

 exopod or scaphognathite. The inner margins of 

 the segments of the protopod and the endopod 

 are lobed and bear setae. The 2 segments of the 

 protopod bear about 4 setae each. The basal and 

 median segments of the endojx)d bear 2 setae 

 each, and the terminal segment bears 5. The 

 exopod, or scaphognathite, bears 4 setae. The 5 

 terminal setae of the endopod are present through- 

 out the protozoeal and first two mysis stages. The 

 4 setae of the scaphognathite are present in the 



Figure 12. — Photomicrograph of first protozoea. 



683837 O — «1 3 



protozoeal and first mysis stages; the scaphog- 

 nathite is not present beyond the first mysis. 



The second maxilla is somewhat larger than the 

 first. It has a protopod of 4 lobed segments. The 

 basal segment bears about 5 setae, and the remain- 

 ing 3 segments, 2 each. In the protozoeal and 

 mysis stages the setae on the protopod of the max- 

 illae are shorter and stouter than the setae found 

 elsewhere on the body. Each segment of the 5- 

 segmented endopod beai*s 2 setae except the termi- 

 nal segment, which has 3. This latter number is 

 constant for the protozoea, but in succeeding 

 stages the scaphognathite increases in size and 

 possesses an increasing number of setae. 



The first maxilliped is the largest of the newly 

 functional appendages. It consists of a 2- 

 segmented protopod, a 4-segm6nted endopod, and 

 an unsegmented exopod. Both of the latter are 

 palplike. The segments of the protopod bear ap- 

 proximately 3 to 4 setae each ; those of the endopod 

 have 2 or 3 each except for the terminal segment, 

 which bears 5 setae. The unsegmented exopod 

 bears 7 setae. 



The second maxilliped is almost identical to the 

 first, except that it is smaller and bears fewer 

 setae. The protopod has 2 segments and bears 

 approximately 5 to 7 setae. The endopod is 4-seg- 

 mented; the terminal segment bears 5 setae and 

 the other 3 segments bear 2 setae each. The ex- 

 opod is unsegmented and bears 6 setae. 



The digestive tract runs from the mouth to the 

 posterior end of the body. It is widest at its 

 anterior and posterior portions. A pair of muscle 

 bands is present along the margins of the body 

 in the region of the thorax and abdomen. 



SECOND PROTOZOEA 



The second protozoeal stage and succeeding 

 larval stages were described from a series of speci- 

 mens linked with the first protozoea and with each 

 other by their simultaneous occurrence in plank- 

 ton tows. Individuals of the second protozoeal 

 stage (fig. 13) measured from 1.5 to 1.9 mm. in 

 body length, based on the examination of 15 speci- 

 mens taken from the plankton. 



The main differences between this stage and the 

 preceding one are the acquisition of a rostrum and 

 supraorbital spines, the appearance of stalked com- 

 pound eyes which are free from the carapace, and 

 the segmentation of the abdomen. 



