FISHERY BULLETIN: VOL. 75. NO. 2 



detached from impregnated females are practi- 

 cally empty. This suggests that the sperm are 

 released with the entire spermatophore present, 

 i.e., that the spermatophore is not torn or split 

 leaving the sperm masses with the paired wings 

 flanking them on the female while the geminate 

 body and adjoining flanges fall away, as seems to 

 occur in some members of the subgenus Lito- 

 penaeus, genus Penaeus. 



Reproduction-Anderson and Lindner (1971) re- 

 ported that on the St. Augustine Grounds, P. 

 robustus probably spawns throughout the year, 

 with a peak between January and May. Recruit- 

 ment begins when the shrimp are approaching 

 1 yr of age and are less than 100 mm tl; maturity 

 is reached in about 3 yr. Most shrimp on the 

 grounds are mature, and the life span appears to 

 be no less than 5 yr. 



The larvae of P. robustus are unknown. Bur- 

 kenroad (1936) identified as "juveniles" the only 

 postlarvae of the species ever recorded, specimens 

 that I have examined. Curiously, Anderson and 

 Lindner (1971) found neither larval nor postlarval 

 stages in a large number of plankton samples 

 collected over an extensive area seaward of the 

 St. Augustine Grounds. They stated that only a 

 single larva was considered as possibly belonging 

 to "Hymenopenaeus." 



Ecological notes.-ln the northestern Gulf of 

 Mexico and off the southeastern coast of the 

 United States, this shrimp has been found within 

 a temperature range of 5°-15°C, and is commer- 

 cially abundant betwen 9° and 12°C (Bullis 1956; 

 Bullis and Cummins 1963). The preference of P. 

 robustus for this range of temperature was re- 

 vealed by the observations of Bullis and 

 Cummins, who stated that within 1 or 2 days 

 after two incursions of cold bottom water off the 

 northeast coast of Florida, shrimp moved inshore 

 to waters 75 m shallower than those where they 

 had been observed previously. Later, Roe (1969) 

 reported that the maximum densities of this 

 shrimp is in water temperatures of 9° to 10°C. 



Commercial concentrations of royal red have 

 been reported (Bullis 1956; Bullis and Rathjen 

 1959; Roe 1969) to occur on the following types 

 of bottoms: blue-black terrigenous silt and silty 

 sand off the Mississippi River Delta; whitish, 

 gritty, calcareous mud off Tortugas; and basically 

 similar sand or silty sand (called "green mud" by 

 the fishermen) off the northeast coast of Florida. 



308 



Anderson and Bullis (1970) presented direct 

 observations of this shrimp made from the sub- 

 marine Aluminaut off Daytona Beach, Fla., at a 

 depth of 459 m. They stated that "The bottom 

 was remarkably free from obstructions and con- 

 sisted of a grayish, loosely constituted sediment 

 that readily clouded the water at the least dis- 

 turbance. It was formed into a myriad of shallow 

 depressions and mounds, pitted with holes. . . . 

 Bottom photographs had previously indicated 

 that royal-red shrimp stayed on the sea-floor sur- 

 face, but we saw numerous shallow furrows (1 to 

 3 feet long) in the bottom in which royal-red 

 shrimp were partly buried. They apparently do 

 not burrow as deeply or completely as do brown 

 and pink shrimp. We believe the shrimp plow into 

 the bottom in search of food rather than pro- 

 tection, and that this feeding activity produces 

 the grooves or furrows." 



Remarks-Smith (1885) cited 14 males and 4 fe- 

 males in USNM lots 6907 and 6908. My examina- 

 tion of this material has shown that the first lot 

 consists of 2 males and 7 females, but the second 

 lot includes 2 males and 5 females of "Hymeno- 

 penaeus" robustus and 1 female of Penaeopsis 

 serrata (Bate 1881). Consequently Smith's state- 

 ment is in error since there are only 4 males and, 

 furthermore, the total number of females (includ- 

 ing that of the latter species) must have been 

 either 13 or 12 if one of them is missing from the 

 lots. In the original description of the species, 

 Smith stated that the proximal portion of the 

 ventral antennular flagellum "is densely hairy in 

 the male"; however, the marked difference that 

 occurs between the pubescence of the flagellum in 

 the male and the female has not been cited in 

 subsequent morphological studies of the shrimp. 

 Here, for the first time, detailed accounts of the 

 setation of the ventral flagellum in both sexes 

 are presented. 



The petasma of P. robustus has been described 

 previously by various investigators. Smith (1885) 

 gave the first brief account. Later, A. Milne Ed- 

 wards and Bouvier (1909) described and illus- 

 trated it in more detail; however, the two figures 

 presented by them include several inaccuracies 

 which were pointed out by Burkenroad (1936). In 

 the same publication, the latter gave an accurate 

 description of this structure. More recently, 

 Roberts and Pequegnat (1970) presented observa- 

 tions as well as a sketch of the petasma, and 

 Anderson and Lindner (1971) have provided the 



