Ide ntification of Shrimp Larvae 

 Harry L. Cook 



An illustrated key to the genera of penaeid larvae found in the north- 

 western Gulf of Mexico was completed. We were able to assign to genera the 

 reference specimens taken from plankton samples by comparing them with 

 larvae obtained fronn rearing trials as well as with illustrations in the litera- 

 ture. Solenocera and Parapenaeus mysis and postlarval stages, missing from 

 routine plankton samples, were obtained during a special cruise of the M/V 

 SILVER BAY off the mouth of the Mississippi River. 



The key is in two parts. The first, 

 designed mainly for those unfamiliar with pe- 

 naeid larvae, distinguishes penaeid larvae from 

 the more prevalent forms of nonpenaeids found 

 in the plankton samples. It also defines the 

 stages of penaeid larvae. Five nauplial, three 

 protozoeal, and three mysis stages were the 

 general rule, except for Solenocera and Para- 

 penaeus, which have more than three mysis 

 stages. 



The second part deals with the genus 

 identification of the protozoeal, mysis, and 

 postlarval stages of the littoral penaeidae of 

 the northwestern Gulf of Mexico. The key in- 

 cludes illustrations of Parapenaeus , Penaeus , 

 Sicyonia, Solenocera, Trachypeneus , and 

 Xiphopeneus and is now being tested in the lab- 

 oratory. 



Considerable effort was spent to dif- 

 ferentiate the species of larval Penaeus. As 

 the most accurate way to do this is by examin- 

 ing larvae of known parentage, special short 

 cruises were made to catch ripe females that 

 would spawn in the laboratory. The efforts were 

 successful, and from females that spawned in 

 the recirculating sea-water system, larvae were 

 reared through Protozoea I for Penaeus aztecus, 

 Sicyonia brevirostris, and Trachypeneus similis . 



Protozoea III of Solenocera 

 sp. , dorsal view. (Left an- 

 terior appendages not shown.) 



Most of the larvae preserved were in good con- 

 dition, and sufficient material was obtained for 

 detailed descriptions. 

 In conjunction with the rearing trials, experiments were made with 

 temperature control, rearing media, and food. It appears that temperatures 

 above 23* C. are required for optimum growth in the laboratory. Larvae reared 

 at temperatures of 24' and 28 "C. were very active and developed rapidly. Those 



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