r^T^^^^y- 



FiQUKE 76. — Pcnaeus \M.) hrasiliensis Lat. a. 

 Median protuberance with horns on posterior 

 margin of sternite XIII, 9 43.5 mm. c.l., E. of 

 Greorgetown, Guyana, b. Thel.vcum, 9 41 mm. 

 c.l., off Surinam, c. Thelycum, 9 42 mm. c.l., 

 off Surinam. 



spines on its inner surface, and the long disto- 

 median projections of the petasma. 



P. Irasiliensis also often has the cicatrices on the 

 sixth abdominal somite conspicuously smaller, par- 

 ticularly the posterior one, than those of any other 

 Penaeus from the entire region. 



P. hrasiliensis juveniles closely resemble those of 

 P. d. duorarum and P. d. notialis; in P. hrasilien- 

 sis males, however, the median ridge on sternite 

 XIV is higher, particularly in the anterior por- 

 tion which is produced in a triangle (as seen in 

 lateral view), and the groove surrounding the 

 ridge is deeper than that found in the two sub- 

 species of P. duorarum. Furthermore, in males 10 

 to 11 mm. c.l., 47 to 51 mm. t.l., the ventral costa of 

 tlie i>etasma lacks distomarginal sf)ines. Males 12 

 mm. c.l., 55 mm. t.l., usually have the distomedian 

 projections of the petasma longer and more slender 

 than those of P. d. duoranim and P. d. notialis of 

 corresiwnding size. In females, 12 mm. c.l., 55 mm. 

 t.l., the anterior process is smaller; the lateral 

 plates have the anteromedian corners angular or 

 pointed anteriorly rather than rounded, and if the 

 posterior process bears a median carina, it is lo- 

 cated between the horns. In addition, in the Carib- 

 bean region, the dorsolateral sulcus in P. hrasilien- 

 sis is usually narrower tlian in P. d. notialis. 



Juveniles of P. hrasiliensis are distinguished 

 from those of P. a. aztecus and P. a. suhtilis by the 

 usually almost straight rostrum wliich is also 

 shorter than in P. a. suhtilis through their com- 

 mon range; males may also be distinguished by the 

 sharp median ridge on the ventral surface of ster- 

 nite XIV, and females by the posterior process, 

 which is less prominent, is not produced caudally, 

 and often lacks a median carina, which, if present, 

 is situated more dorsally. The median sulcus is 

 also deeper and longer, and tlic adrostral sulcus 

 much wider and longer than in juveniles of P. a. 

 suhtilis. The typical characters of the external 

 genitalia mentioned above also distinguish P. hra- 

 siliensis juveniles from those of P. paulensis. Fur- 

 thermore, the dorsolateral sulcus is usually broader 

 in P. hrasilieTisis throughout their common range. 



Reproduction 



SUBADULT STAGE-SEXUAL MATURITY 



The smallest males observed with joined 



pe- 



tasma were 15 mm. c.l., 69 mm. t.l.; many indi- 

 viduals to 22 mm. c.l., 97 mm. t.l., however, had 

 unjoined petasmal endopods. It, therefore, appears 

 that males reach the subadult stage within the 



WESTERN ATLANTIC SHRIMPS OF GENUS PENAEUS 



573 



