Figure 74. — Fretiuency distribution of keel-sulcus (K/S) 

 values (both .sexes included) in Penacits (J/.) brasiUcn- 

 sis Lat. of different size classes from the West Indies. 

 Central America, eastern United States, and the 

 Bermudas. 



than P. a. subfil/s. although it is more frequent in 

 deeper water (20 to 30 fm.). He also indicated 

 a similar finding in French Guiana, where most 

 P. hrasUien.'iis were caught between 22 and 38 fm. 

 Bullis and Thompson (1959a) stated that com- 

 mercial quantities of this species are present off the 

 Guianas, and that maximum catches were taken 

 near the 30-fm. curve. The same depth distribu- 

 tion seems to persist along the coast to Brazil, 

 where it is also abundant. 



The bathymetric range of P. hraslliensis while 

 broad, is not so great as that of P. d. notialis. The 

 greatest depth at which it has been collected is 150 

 fm. At this depth a collection was made west of 

 Andros Island, Bahamas, at Oregon. Sta. 2475. 

 Other deep water records (see Study Material) 

 include depths of 95, 100, and 105 fm. 



Rossignol (1957) reported P. hrasiliensis from 

 West Africa. It seems probable that the specimens 

 were actually P. duorarum notialis. and that the 

 author identified them using the old name P. ira- 

 sUiensis, a name employed before Burkenroad 

 (1939) recognized that three species were included 

 under the latter name. 



In P. 'brasiliensis both the petasma and the tliely- 

 cum vary, but none of the variations may be cor- 

 related with a restricted portion of the range. In 

 the petasma the number of teeth on the attached 

 edge of the ventral costa vary in number, and 

 the band of spines along the membranous portion 

 of the ventrolateral lobule may be narrow or rela- 

 tively broad. The thelycum, in turn, may or may 

 not have a median carina projecting caudad from 

 the posterior process ; the protracted anteromedian 

 corners of the lateral plates may taper anteriorly 

 or may be expanded into disklike projections that 

 overlap. Neither of the characters mentioned, how- 

 ever, is typical of shrimp from a limited region. 



As stated above, the keel-sulcus ratio increases 

 progressively (the dorsolateral sulcus narrows) 

 from northern South America northward; no 

 distinct break occurs in the range of this ratio 

 anywhere within the range of the species. The 

 length of the rostrum also shows a south-north 

 cline, a tendency to increase from south northward, 

 reaching a maximum in the populations from the 

 Bahamas, the United States, and the Bermudas. 



Relationships 



Adults of P. hrasiliensis are readily separable 

 from adults of the other species of Penaeus from 

 the western Atlantic. Females can be identified by 

 the small anterior process and the anteromedian 

 corners of the lateral jilates, which are produced 

 anteriorly and completely cover the posterior 

 process, and by the lack of a median carina on the 

 latter or the possession of a short one which is 

 situated at the posterior end, sunk between the 

 horns of sternite XIII. Males may be recognized 

 by the free apex of the ventral costa, the distal 

 fold that forms a large auricle armed with strong 



WESTERN ATLANTIC SHRIMPS OF GENUS PENAEUS 



571 



