Figure 9. — Penaeus setiferus (Linnaeus). Chroniato- 

 phore distribution in tail fan (seimdiagraniniatie) of A, 

 17 rum. juvenile, B, 32 mm. juvenile; A-B approximately 

 X 5 (after Williams, 1953). C, thelycum of adult fe- 

 male ; D, petasma of adult male, ventral view, distal 

 portion of left half (after Burkenroad, 1934b). 



Remarks. — Of the shrimps occurring in the 

 Carolinas, P. setiferus has been studied most ex- 

 tensively. This has resulted from the fact that 

 the species has great commercial value, and was 

 the first of the American penaeids to be exten- 

 sively marketed for food. In the early 1930's, 

 when popular demand caused fishing effort to 

 expand greatly, concern over the possibility of 

 depleting the resource led the U.S. Fish and Wild- 

 life Service to initiate a research program on 

 various aspects of the biology of this species. At 

 that time, P. setiferus composed over 95 percent 

 of the commercial catch (Lindner and Anderson, 

 1956). A voluminous literature, scholarly and 

 popular, has accumulated in the ensuing 30 years, 

 and though it would be presumptuous to attempt 

 a complete review of this work here, the chief 

 results of studies can be outlined. (An exhaustive 

 bibliography has been complied by Chin and 

 Allen, 1959). 



Recently (see synonymy) usage of the name 

 setiferus for the white shrimp in North America 

 has been questioned. The well-established name 

 setiferus would seem best, retained here. 



The species is caught commercially throughout 

 most, of its geographic range (from North Caro- 

 lina to Mexico) ; however, by far the greatest 

 concentration occurs in Louisiana, in and near the 

 Mississippi River Delta, and it was here that 

 Viosca (1920) first w T orked on some aspects of 

 the species' natural history anticipating in many 

 respects later more detailed studies. 



One of the latest studies to be published should 

 be cited at the outset. Young (1959) in his ex- 

 haustive morphological study of P. setiferus 

 reiterated the generalized structure of the 

 Penaeidae. This work is profusely illustrated and 

 the text illuminates details which have often been 

 obscurely presented in older works. Complexes 

 such as the branchial apparatus and associated 

 structures are clearly delineated, as are the 

 skeletal, muscular, nervous, circulatory, and res- 

 piratory systems in general. The genital armature, 

 of great taxonomic value, is treated briefly, and 

 here the student must look to the works of Burk- 

 enroad (1934b, 1939) for details. 



In 1956, Lindner and Anderson summarized 

 work of the U.S. Bureau of Fisheries and the Fish 

 and Wildlife Service in the 1930's and 1940's that 

 had been presented in a series of shorter articles. 

 Reference to this paper will lead the reader to 

 earlier detailed studies. 



Spawning of the white shrimp in the Carolinas 

 probably begins in May and extends into Septem- 

 ber (Lindner and Anderson, 1956; Williams, 

 1955a) ; farther south in the Gulf of Mexico the 

 season probably extends from March to September 

 or October. Gunter (1950) suggested two periods 

 of spawning (spring and fall) for Texas waters, 

 but in the Carolinas there is probably only one. 



Maturation of gonads has been studied in de- 

 tail (King, 1948) in both males and females. In 

 females, the stages of maturity can be judged 

 macroscopically by color of the ovary. The earliest 

 or undeveloped stage may last for an indetermi- 

 nate period of time (Lindner and Anderson, 

 1956) ; the developing stage is judged to last a 

 month or less. The succeeding yellow stage per- 

 sists for 1 to 2 months, and the ripe, olive-drab 

 colored ovaries become spent in less than a month. 



MARINE DECAPOD CRUSTACEANS OF THE CAROLINAS 



19 



