size range 15 to 23 mm. c.l., 69 to 101 mm. t.l. The 

 smallest females with functional thelyca wei'e 15 

 mm. C.L, 70 mm. t.l., but in many females 19 mm. 

 c.l., 86 mm. t.l. the lateral plates were non-con- 

 tiguous. Thus, they reach the subadult stage with- 

 in the size range 15 to 20 mm. c.l., 70 to 90 mm. t.l. 

 No studies have been made to allow conclusions as 

 to the size at which females first reach maturity. 



COPULATION 



As it seems to be true in other Penaem with a 

 closed thelycum, copulation in P. hrasiliensis is 

 believed to take place between a hard-shelled male 

 and a soft-shelled female. 



OVARY DEVELOPMENT .\ND SPAWNING 



No studies have been conducted. 

 SEX RATIO 



No intensive sampling has been carried out to de- 

 termine the male-female ratio. 



Postembryonlc Development 



LARVAE, POSTLARVAE, AND JUVENILES 



No studies have been made on either larval or 

 postlarval stages of this shrimp. 



My studies showed that juvenile P. hrmiliensis 

 of 18 mm. t.l. have distinctly long adrostral sulci. 

 This character allows for the separation of early 

 juveniles of this as well as those of the other 

 grooved Penaeus. from those of the nongrooved 

 P. setiferus and P. schmitti. At a minimum of about 

 20 mm. t.l. males and females are distinguished, as 

 are those of the other grooved Penae.us in the west- 

 ern Atlantic, by the endopods of the first pair of 

 pleopods, which in the males are longer and are 

 located more proximally on the bases than in the 

 females. In addition, males have a sharp, high 

 ridge on the midline of sternite XIV, whereas in 

 females the sternite XIV is produced on the mid- 

 line where a knob is frequently present. (See also 

 under Relationships.) 



GROWTH 



No studies have been made. 



SEX DIFFERENCES IN SIZE 



The largest females on record were 250 mm. t.l., 

 reported from eastern Venezuela by Davant 

 (196.3), whereas the largest I measured was 58.5 

 mm. c.l., 214 mm. t.l., from off Guyana. The 

 largest male recorded was 191 mm. t.l., reported 

 by Holthuis (1959) from Surinam waters. Off- 

 shore samples indicate that, as in other Penaeus 



from the western Atlantic, P. hrmiliensis females 

 become lai-ger than males. 



Ecology 



SUBSTRATE 



P. hrasiliensis juveniles are more abundant 

 where the bottom consists of soft mud. Laguna 

 Doctor, Playa de Baracoa, Cuba, where Perez 

 Farfante et al. (1961) carried on their sampling, 

 has a bottom of very soft mud covered with vege- 

 tation, a habitat typical of most nursery grounds 

 for Penaeus shrimp. Adults seem to prefer rather 

 firm bottoms. According to Bullis and Thomp- 

 son (1959a) , along the Continental Shelf of South 

 America, from Trinidad to the xVmazon River, this 

 species is most abundant on bottoms consisting 

 chiefly of a mixture of mud and sand. 



DIEL CYCLE 



P. hrasiliensis has mostly nocturnal habits; the 

 young in inshore water are fished at night. Tremel 

 and Mistakidis (1965) described in detail the night 

 fishing for camarao rosa {P. hrasiliensis and P. 

 foulensis) in the coastal lagoons of the State of 

 Santa Catarina, Brazil. Adults are also active at 

 night; Bullis and Thompson (1959a) stated that 

 during their exploratory fishing, "catches fell off 

 at or before daylight, and daytime trawling was 

 miproductive for this species." 



The only information available concerning the 

 influence of the lunar phases on the behavior of 

 this species is that given by Wheeler (1937) ; his 

 observations were made in the Bermudas. This 

 author stated that P. hrasiliensis showed a rhyth- 

 mic pattern of activity and quiescence over the 

 new and full moon, respectively, and concluded 

 that the most probable cause of periodic swarming 

 is the cyclic absence of light. He also indicated 

 that the effect of light is occasionally subject to 

 interference by such factors as the opacity of the 

 water. 



MOVEMENTS 



No information is available regarding migra- 

 tions of P. hrasiliensis at any stage of its life cycle. 

 The only data gathered are a few records of the 

 time juveniles and subadults occupy inshore waters 

 in different areas throughout the range. Eldred 

 (1960) reported juveniles and subadults in Bis- 

 cayne Bay, Fla., in July, December, and February. 

 Later this species was found to form a large per- 

 centage of the shrimp that live in the Bay during 

 the summer. I have identified specimens from in- 



WESTERN ATLANTIC SHRIMPS OF GENUS PENAEUS 



575 



