differently armed (with a narrow patch of closely 

 set teeth). In females the anterior and posterior 

 processes are much broader than those of P. 

 paulensis. 



Reproduction 



SUBADULT STAGE-SEXUAL MATURITY 



The smallest size at whicli males were fomid 

 with the petasma joined was 16 mm. c.l., 72 mm. 

 t.l. and the smallest size at which females were 

 found with a functional thelycum was 18 mm. 

 c.l., 83 mm. t.l. The size at which P. a. suhtUis 

 reaches sexual maturity is not known. 



OVARY DEVELOPMENT 



The studies by Magalhaes Filho (1943) of the 

 external genitalia and gametogenesis of "F. hra- 

 siliensls.'' as he identified his material, seem to me 

 to have been taken on P. aztecus subtilis. His il- 

 lustrations of the thelycum with widely gaping 

 lateral plates leaving exposed a broad posterior 

 process and of a petasma with appai-ently short 

 distomedian projections indicate that the speci- 

 mens were probably dark shrimp. 



Postembryonic Development 

 LARVAE, POSTLARVAE, AND JUVENILES 



No studies have been made on the larval and 

 postlarval stages of this shrimp. 



My studies of small individuals showed that the 

 adrostral sulci are distinctly developed in P. a. 

 siibti/ls juveniles 18 mm. t.l. Because the sulci are 

 shorter than in other grooved Penaeus from the 

 western Atlantic, the juveniles can be readily dis- 

 tinguished from those of the nongrooved shrimps. 

 Small males may be distinguished from females by 

 the larger size of the petasmal endopod and its 

 more proximal position on the basis. Males also 

 have a low rib on the midline of sternite XIV, 

 whereas females have sternite XIV ventrally pro- 

 duced to a midpoint. 



Females with a 10.5 mm. c.l., 47 mm. t.l., bear 

 a sniall spine projecting caudad from the posterior 

 margin of sternite XIII. This conspicuous charac- 

 ter also makes it possible to distinguish them at 

 that small size from the grooved sympatric 

 Penaeus. 



GROWTH 



It has been repoi'ted (Anonymous, 1962) that in 

 Guyana P. a. suhfUis kept in ponds grew from 25 

 mm. t.l. to 200 to 225 mm. t.l. in 7 or 8 months. 



554 



SEX DIFFERENCES IN SIZE 



The largest female examined, caught off Suri- 

 nam m 50 fm., Oregon Sta. 2016, had 55 mm. c.l., 

 205 mm. t.l.; the largest male, caught off Isere 

 Point, French Guiana, in 34 fm., Oregon Sta. 2322, 

 measured 36 mm. c.l., 152 mm. t.l. Boschi (1963) 

 cited under P. aztecus an unusually large male, 200 

 mm. long, but no locality was given; neither was ii 

 reference given as to which "Form" it belonged. ] 

 It is not possible to ascertain if the specimen was 

 typical P. a. azteciis, P. a. suitUis, or P. paulensis. 



Oft'shore dark shrimp show a sex-size disparity : 

 females are larger than males; the difference in 

 size between sexes increases with depth. 



Ecology 



FOOD 



No studies have been made on the food of this 

 shrimp. I found a tentacle of the squid Doryteu- 

 this j)lei Blainville hanging from the mouth of a 

 specimen from off Departamento de la Guajira, 

 Colombia. 



SUBSTRATE 



Juvenile as well as adult P. a. siibtilis prefer 

 muddy substrates. Holthuis (1959) reported that 

 in Surinam it was taken on bottoms of soft and 

 hard mud, and mud with shells. Bullis and Thomp- 

 son (1959a) stated that on the Continental Shelf 

 of South America, from off Trinidad to the Ama- 

 zon River, camaron marron was found predom- 

 inantly on muddy bottoms. It also lives on bottoms 

 consisting of a mixture of mud and sand and on 

 those which consist predominantly of coral sand, 

 where I collected specimens in northern Cuba. 

 DIEL CYCLE 



No information is available on the diel activity 

 of camaron marron inshore. Bullis and Thompson 

 ( 1959a) noted tliat in the Atlantic Coast of north- 

 eastern South America sizes of the catches were 

 approximately the same day and night, whereas 

 Croker (1967) stated that off Nicaragua this sub- 

 species is fished at night. 



MOVEMENTS 



Postlarvae of P. a. subfiJts move into insliore wa- 

 ters where the young are known to live. INIost of the 

 specimens I examined from tlic Antilles came from 

 bays. Ewald (1965c) reported that in Venezuela 

 juveniles are found in abundance in lagoons and 

 mouths of rivers and are taken commercially in 

 Lake Maracaibo. Davant (1963) liad previously re- 

 ported specimens ui) to 100 mm. long from various 

 estuarine waters of Venezuela. Farther along the 



U.S. FISH AND WILDLIFE SERVICE 



