FiGUBE 26. — Penaetis (M.) duorarum duora- 

 rum Burkenroad. Jledian protuberance 

 with horns on iwsterior margin of sternite 

 XIII, 9 47.5 mm. c.l., northwestern Gulf 

 of Mexico. 



roundish i:)atclies at the center of each pleuron. 

 Gunter and Hall ( 1963 ) described the pink shrimp 

 as having a saddle-shaped mark extending from 

 the prominent abdominal spot forward and di- 

 agonally across the second abdominal somite and 

 over the posterior end in the spot on the third 

 somite. 



FiGLTRE 27. — Penacus (.1/.) dvoranim duorarum Burken- 

 road. Thelycum, 5 38 mm. c.l., Sanibel grounds. Fla. 



Distribution and Morphological Variations 



The range of P. d. duorarum extends from lower 

 Chesapeake Bay southward along the Coast to the 

 Florida Keys and Gulf of Mexico. In the Gulf it 

 ranges from the Tortugas Islands along the Gulf 

 Coast of tlie United States and through the coastal 

 waters of Mexico to Cape Catoche and south to 

 Isla Mujeres. It is also found in the Beniiuda 

 Islands (fig. 28). This paper carries the first re- 

 port of pink shrimp from the northern coast of 

 Yucatan and Ijeyond Cape Catoche. 



The densest populations of pink shrimp are off 

 southwestern Florida and in the southeastern por- 

 tion of Golfo de Campeche. The Gulf of Mexico, 

 thus, is considered the center of distribution of the 

 subspecies. 



Tlie greatest concentrations of pink .shrimp are 

 between 6 and 20 fni. but in some localities pink 

 shrimp are abundant at depths of as much as 

 35 fm. A few specimens M-ere collected at 180 fm. 

 {Silver Bay Sta. 3710) off Cape Kennedy, Fla., 

 and it has been reported (Anonymous, 1961) that 

 catches of "P. duorarum,'''' were taken at 150 to 200 

 fm. off the western edge of the Great Bahama 

 Bank. These shrimp could have been either P. d. 

 duorarum or P. d. notialis because which of the 

 two subspecies occupies the area is not known. 



P. d. duorarum shows some degree of variation 

 throughout its range : the keel-dor.solateral sulcus 

 ratio ranges rather widely, the breadth of the 

 adrostral sulcus varies, the number of external 

 spines at the distal end of the ventral costa of the 

 petasma varies considerably, and the distal fold 

 of the petasma may or may not be armed with 

 submarginal spinules. None of the variations, how- 

 ever, are restricted to portions of the range. 



Relationships 



P. duorarum duorarum has the dorsolateral 

 sulcus narrower than P. d/aorarum, notialis from 

 the Caribbean Sea, the Atlantic Coast of South 

 America, and Africa. Burkenroad (1939) was the 

 first to point out this difference between the two 

 and called the former "Form A," and the latter 

 "Form B." Biometric studies have indicated a 

 statistically significant difference in the ratio (K/ 

 S) of K (height of the keel) to S (width of the 

 sulcus) between those populations. In P. d. notialis 

 from the southern region, K/S varies from about 

 0.25 to 3, modally 1.75 (fig. 34). Overlapping is .so 



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U.S. FISH AND WILDLIFE SERVICE 



