EARLY DEVELOPMENTAL STAGES OF THE BROWN SHRIMP, 

 Penaeus aztecus IVES, REARED IN THE LABORATORY' 



Harry L. Cook- and M. Alice Murphy' 



ABSTRACT 



The larval and first postlarval stages of the brown shrimp, Penaeus aztecus Ives, reared from eggs 

 spawned in the laboratory, as well as the eggs themselves, are described and illustrated. The larvae 

 and first postlarva are compared with those of the pink shrimp, P. duoranim Burkenroad, and white 

 shrimp, P. setifenis (Linn.). 



Commercial shrimp landings from Gulf of Mex- 

 ico and South Atlantic waters of the United 

 States are comprised mainly of three species: 

 the brown shrimp, Penaeus aztecus Ives; the 

 pink shrimp, P. duoranim Burkenroad; and the 

 white shrimp, P. setiferus (Linn.). The Gulf 

 coast shrimp fishery is the most valuable of do- 

 mestic commercial fisheries, and in 1968 the 

 value to fishermen for shrimp caught in the 

 Gulf amounted to nearly $95 million. Because 

 of their relative importance, these shrimps are 

 being intensively studied by the National Ma- 

 rine Fisheries Service in an effort to understand 

 more fully their biology and ecology. 



Thirteen species of penaeid shrimp repre- 

 senting five genera inhabit the shallow near- 

 shore waters of the northwestern Gulf. At the 

 present time their larvae can only be identified 

 to genus (Cook, 1966). Within genera the 

 larvae are so similar morphologically that at 

 any given stage the various species cannot yet 

 be distinguished. Since adults of the three com- 

 mercially important species often occur together 

 and overlap in their spawning activity, there is 

 also some intermingling of their planktonic 

 larvae. To answer basic questions about larval 

 distribution, growth, and survival of each spe- 



• Contribution No. 309, National Marine Fisheries 

 Service Biological Laboratory, Galveston, Texas 77550. 



^ Formerly National Marine Fisheries Service Bio- 

 logical Laboratory, Galveston, Texas; present address: 

 Division of Contract Research, Texas Division, Dow 

 Chemical Company, Freeport, Texas 77541. 



' National Marine Fisheries Service Biological Lab- 

 oratory, Galveston, Texas 77550. 



Manuscript received September 1970. 



FISHERY BULLETIN: VOL. 69. NO. 1, 1971. 



cies, accurate identification of larvae is essential. 

 The larval and early postlarval stages of the 

 pink shrimp were described by Dobkin (1961), 

 and those of the white shrimp by Pearson ( 1939) 

 and Heegaard (1953). These shrimp have five 

 nauplial, three protozoeal, three mysis, and sev- 

 eral postlarval stages. Their morphological 

 characteristics during these stages are so alike, 

 however, that biologists still encounter diflSculty 

 in differentiating the two species. Since the 

 early developmental stages of the brown shrimp 

 have not been described, the purpose of this 

 ])aper is to do so and at the same time compare 

 them with corresponding stages of the pink and 

 white shrimps. 



METHODS AND MATERIALS 



Larvae of the brown shrimp were first suc- 

 cessfully cultured in the laboratory during the 

 fall of 1963. Since that time, culture techniques 

 have improved greatly. The methods used in 

 our culture of larval penaeid shrimp were de- 

 scribed by Cook and Murphy (1966), Cook 

 (1969), and Cook and Murphy (1969). 



Specimens of each stage were preserved for 

 descriptive purposes. Drawings were made 

 with the aid of a camera lucida. The figures 

 of each substage are composite and represent 

 an "average" larvae rather than any one indi- 

 vidual. Also, with the exception of the nauplii, 

 appendages on these figures ai-e intended to in- 

 dicate only relative size and position, not to show 

 details of setation. The enlarged figures of 



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