FISHERY BULLETIN: VOL. 73, NO. 3 



A 



B 



Figure 4.-Penaeiis {Litopenaeus) vannamei. A, Thelycum,$51 mm cl, NW Penfnsula de Azuero, Panamd. B, Ventrolateral 

 view of thelycum,$48 mm cl, same locality, mp, median protuberance; XII, XIII, and XIV, sternites. 



ventrally by the short posteromesial extensions 

 (protecting the gonopores) of the coxae of the 

 third pereopods. 



Disposition of the Compound 

 Spermatophore on the Thelycum 



When attached to the female, the compound 

 spermatophore forms a distinct arc, the fundus of 

 the sperm sacs being elevated (ventrally) weW 

 above the sternum. The sacs are thus directed 

 anterodorsally w^ith the anteriormost portions of 

 their ventral walls resting on the border of the 

 median protuberance of sternite XIII, and the 

 contiguous lateral flaps extending over the coxae 

 of the fourth pereopods; these flaps seem to serve 

 as stabilizers for the rather compressed, vertically 

 extended sacs. Anteriorly, the bulges of the sacs 

 become very conspicuous, and the practically fused 

 dorsomesial walls lie almost perpendicular to the 

 horizontal coxal plates of the fourth pereopods. 



The sperm is released at the level of the median 

 protuberance of the female, thus not as close to the 

 gonopores as in the remaining species of the 

 group. In opposition to the paired sacs, the flanges 

 are directed posterodorsally reaching the first 

 pleonic sternite; they cover the dorsal plates ven- 

 trally, embrace them mesially, and are flanked 

 laterally by the glutinous material suspended 

 from their narrow flaps. The anterior parts of the 

 dorsal plates, which seem to be the principal 

 elements of attachment of the spermatophores in 

 this species, become fused along their mesial 

 ridges, and are basally affixed to sternite XIV 

 (pressing against the thelycal ridges) as well as to 

 the coxae of the fifth pereopods. The posterior 

 parts of the dorsal plates, in turn, lie on the trans- 

 verse setose patch of the first pleonic sternite. 

 Finally, the gelatinous substance, protruding 

 through the anterodorsal extremity of the sper- 

 matophore, spreads over and beyond the thelycal 

 protuberance of sternite XIII, while the paired 



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