fKKEZ FAKKANTl!;: ShKKMATOPHORES OF AMERICAN WHITE SHRIMPS 



and is armed with a blade, the anterior portion of 

 which is directed both dorsomesially and ven- 

 tromesially instead of laterally, in specimens 

 removed from males. Along the sac, the lateral flap 

 is almost as broad as that in P. vannamei, but 

 thinner and not fleshy. Furthermore, in P. 

 stylirostris, the paired dorsal plates affix only the 

 posterior part of the spermatophore to the 

 females, not directly supporting the midportion. 

 The flanges become attached to the female almost 

 perpendicular to the geminate body, instead of 

 extending entirely caudad as in P. vannamei or 

 somewhat caudad as in P. schmitti and P. se- 

 tiferus. 



The spermatophores of P. schmitti and P. se- 

 tiferus are almost identical. They may be distin- 

 guished by the width of the lateral blade, the 

 anterior portion of which is broad (except for a 

 narrow portion at the base of the wing) in P. 

 schmitti and very narrow in P. setiferus. Sperm 

 sacs of both species are similar to those of P. van- 

 namei and P. occidentalis; however, they bear 

 wings, which are lacking in P. vannamei, and the 

 wings are moderately large and scabrous, with 

 various projections on the ventral surface, thus 

 very different from the small wing with the mar- 

 gins extensively folded found in P. occiden- 

 talis. Also, the flanges extend considerably 

 anteriad along the lateral walls of the sacs, 

 whereas those in P. vannamei are virtually caudal 

 and, unlike P. occidentalis, are produced 

 posteriorly much beyond the sac instead of barely 

 overreaching the fundus. Finally, flaps borne by 

 the flanges are broad in the two Atlantic species, 

 instead of narrow as in P. vannamei, and, although 

 firm, are different in texture from the heavy 

 sclerotized shelf sustained by the flange in P. oc- 

 cidentalis. 



Despite the similarities of the various sacs, the 

 mode of dehiscence varies -differences among the 

 spermatophores are due more to the elements as- 

 sociated with the sac than to the sac itself. It seems 

 that in P. occidentalis, the sperm is released 

 through anterior openings of the sacs which 

 become applied to the coxal plates of the third 

 pereopods, and are well protected by the anterior 

 lobes of the spermatophores. In P. stylirostris as 

 well as in P. schmitti and P. setiferus, it seems that 

 the compound spermatophore attached to the 

 female splits longitudinally into two parts, the 

 geminate body breaks away leaving paired masses 

 of sperm on the thelycum freely exposed to the 

 surrounding water. In P. schmitti and P. setiferus. 



however, there are certain indications that the 

 sperm reaches the water through a passageway 

 between the wings and the body of the female, the 

 geminate body persisting. On the basis of the 

 available material of P. vannamei, there is no in- 

 dication as to how the sperm escapes from the 

 spermatophore. Understanding of the precise 

 manner in which spermatozoa are freed from 

 spermatophores in all of the species must await 

 direct observations. 



ACKNOWLEDGMENTS 



I am deeply indebted to Meredith L. Jones, 

 Leader, Marine Biota of Panama Project, Smith- 

 sonian Institution, whose interest and efforts in 

 providing equipment and assistance in the field 

 contributed substantially to the success of my trip 

 to Central America; Ira Rubinoff, Director, 

 Smithsonian Tropical Research Institute, who 

 arranged for shipboard explorations in the Gulf of 

 Panama and who made available the facilities of 

 the Institute at Balboa; and Richard A. Neal, 

 Investigation Chief of Aquaculture Research 

 Technology, Gulf Coastal Fisheries Center 

 Galveston Laboratory, National Marine Fisheries 

 Service, NOAA, for assistance in securing living 

 white shrimp from off Texas. I am especially 

 grateful to Alfredo Rizo and Ernestina Rizo for 

 placing at my disposal the shrimp trawler San- 

 tanderino, manned by a most efficient crew, and 

 for their part in making my stay in Colombia so 

 thoroughly enjoyable; Ernestina Rizo also 

 cooperated in handling and preserving specimens 

 aboard ship. Gratitude is also expressed to Billy R. 

 Drummond and Harold H. Webber who went out 

 of their way to make available to me recently 

 collected and beautifully preserved impregnated 

 females of two species from Costa Rican waters. 



It is a pleasure to extend an especial word of 

 gratitude to Horton H. Hobbs, Jr., of the Smith- 

 sonian Institution, whose carcinological 

 background has been the source of many valuable 

 suggestions. Thanks are due Fenner A. Chace, Jr., 

 of the Smithsonian Institution; Austin B. 

 Williams, of the Systematics Laboratory, National 

 Marine Fisheries Service, NOAA; and Won Tack 

 Yang, of the Institute of Marine Sciences, 

 University of Miami, for their critical review of 

 the manuscript. The patience and wholehearted 

 cooperation of Maria M. Dieguez in executing the 

 excellent illustrations are fully appreciated. 



Funding for collecting in Panamanian waters 



485 



