Table 3. — Ranges of lengths of distal Jive podomeres of third pereopod in P. a. aztecus, P. d. duorarum, and P. brasiliensis 



of indicated intervals of carapace length 



subspecies, as has been done to identify freshly 

 caught specimens. 



Juveniles of the grooved Penaeus from the west- 

 ern Atlantic and the Gulf of Mexico are difficult to 

 identify. A mmiber of characters, however, allow 

 the separation of those of P. d. duoraiiim from 

 most of those of P. a. aztecus. The former have a 

 narrower dorsolateral sulcus, usually a shorter ros- 

 trum, a stouter body, and often external genitalia 

 that are better developed than those of P. a. aztecus 

 at the same length. In addition, male juveniles of 

 P. d. duorarum may be separated from those of 

 P. a. aztecus by the ridge on sternite XIV which is 

 higher and pointed anteriorly (fig. 30). Being 

 usually better developed than males of P. a. aztecus, 

 they also have the petasmal endopod larger at the 



L 



1 mm. 



J 



Figure 30. — Penaeus (M.) duorarum duora- 

 rum Burkenroad. Sternites XIII and XIV. 

 (J 10 mm. C.I., Cat Island, La. 



same carapace length. At 11 mm. c.l., 51 mm. t.l. — 

 occasionally at 9 mm. c.l., 42 mm. t.l. — the petasma 

 frequently has spines on the distal margin of the 

 ventral costa. Small females of pink shrimp may 

 be distinguished by characters of the thelycum. At 

 10 mm. c.l., 47 mm. t.l., they lack a knob on the 

 midline at the posterior margin of sternite XIII, 

 whereas brown shrimp of comparable length pos- 

 sess such a knob; and at 12 mm. c.l., 55 mm. t.l., 

 the posterior margin of sternite XIII in the pink 

 shrimp is smooth, whereas that of the brown 

 shrimp bears a small spine projecting posteriorly. 

 Finally, in P. d. duararnim the median carina is 

 simple, whereas in P. a. aztecus of at least 14 mm. 

 c.l., 65 mm. t.l., it has two anterior arms. 



Juveniles of P. d. duorarum can often be distin- 

 guished from those of P. brasiliensis by having the 

 adrostral carina markedly convex dorsally on the 

 posterior two-thirds of the rostrum, rather than 

 straight along the entire length of the rostrum. 

 This character varies, however, and the variations 

 in its shape seem to intergrade with those shown by 

 P. brasilie7isis. Differences in the external genitalia 

 are discussed under the latter species. 



Reproduction 

 SUBADULT STAGE-SEXUAL MATURITY 



In males, I found the petasmal endopods to be 

 first joined at 14 mm. c.l., 65 mm. t.l. This length 

 seems to be the smallest at which copulation can be 

 carried out by male pink shrimp. The petasma, 

 however, can remain unjoined to 19 mm. c.l., 86 

 mm. t.l.; thus, males attain the subadult stage 

 within the range of 14 to 20 mm. c.l. Small males 8 

 mm. c.l., 34 mm. t.l., were found with developed 

 spermatophores within the terminal ampullae. 



Females are considered subadults when the 

 thelycum is sufficiently developed to permit im- 



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U.S. FISH AND WILDLIFE SERVICE 



