WHITE SHRIMP FROM THE GULF OF MEXICO 



155 



V. EXCRETORY SYSTEM 



The details of the excretory system and antenna] 

 gland of Penaeus have not been worked out com- 

 pletely. Compared to the compact and easily visi- 

 ble green gland of the crawfishes, the excretory 

 organs of the white shrimp are much more 

 diffused. Attempts have been made to clarify 

 the extent of the excretory glands of Penaeus by 

 injecting dyes into the excretory pores, and such 

 information as is here presented is based on these 

 procedures. 



The hemocoelic excretory gland of the white 

 shrimp seems to be made up of two major por- 

 tions. The smaller, dorsal portion lies above the 

 supraesophageal ganglion (fig. 86). The gland is 

 continuous with the larger, ventral part of the 

 system by means of its lateral arms. The ventral 

 gland lies beneath the dorsal brain on the midline 

 (fig. 86) and extends into the body of the an- 

 tennae. The dorsal and ventral glands are com- 

 posed of soft, glandular walls and trabeculae 

 enclosing myriads of sinusoids. The portion of 

 the gland entering the antenna makes contact 

 with a compact, nodular, antennal excretory gland 

 (figs. 20, 21) in the basal segments of the antenna. 

 If the surface of the antennal gland is removed, 

 gland concretions or nodules are found embedded 

 in the tissues. A short duct from the antennal 

 gland leads to the exterior through the excretory 

 pore (figs. 21, 23, 24). The median coxal location 

 of the pore is a constant character of Decapoda. 



VI. REPRODUCTIVE SYSTEM 



The external sex organs of Crustacea Decapoda 

 have been widely used as systematic characters in 

 the> groups and those of the Penaeidae are no ex- 

 ception. In the males the petasma (fig. 87), a 

 modified endopodite of the first pleopod, and in 

 the females the thelycum (fig. 80), the modified 

 sternal plates of the fourth and fifth thoracic seg- 

 ments, have received attention. A system of de- 

 scriptive nomenclature, largely meaningless, has 

 grown up about the external sex characters, in 

 particular the parts of the petasma. Of inferior 

 taxonomic importance, but constant in the deca- 

 pods, are the locations of the gonopores. Those 

 of the male lie within folds of thin cuticle between 

 the bases of the fifth walking legs (fig. 88), while 

 the female gonoducts open to the exterior through 

 labiate structures between the third walking legs 

 (fig. 89). A modification of the second pleopods, 



the appendix masculina (fig. 3), varies in shape 

 and size within the Tribe Penaeidae, that of some 

 genera, as in Penaeus, being unspecialized com- 

 pared to the complex appendix masculina in 

 Hynw n o pendens. 



The petasma of the male is a system of lightly 

 sclerotized longitudinal rods connected to folds of 

 thin cuticle which permit the petasma to inflate 

 broadly. The structure is folded close to the basi- 

 podite of the first pleopod in young males. With 

 the molt to sexual maturity, the medial margin of 

 each half of the petasma becomes joined to its 

 counterpart. Under the compound microscope 

 one can see that the margins are invested with 

 tiny, knobbed processes. Thrust together the 

 knobs tend to form a lock, in the words of King 

 (1948), "like a zipper." Although the copulatory 

 act of penaeids has rarely been observed, appar- 

 ently the spermatophore is extruded from the male 

 gonopores and held on the posterior or ventral 

 surface of the petasma and then thrust against the 

 thelycum of the female where it is held in place 

 by the setae and sculpturing of that region. 



The thelycum of Penaeus setiferus (fig. 89) is 

 made of a series of lobes and protuberances char- 

 acteristic of the species (Burkenroad 1936). These 

 presumably enable the animal to retain the 

 spermatophore for a sufficient time to insure ferti- 

 lization. 



Enough research on the internal reproductive 

 organs of Penaeus setiferus has been carried out 

 in the present work to bear out the findings of 

 King (1948), therefore no illustrations repeating 

 his have been prepared on the subject. 



The testes of the male are paired. They lie on 

 the dorsal surface of the hepatopancreas ventral 

 to the heart. Each testis is comprised of several 

 1< ilies extending over the surface of the hepato- 

 pancreas. The vas deferens extends from the pos- 

 terior end of the testis, makes a lateral loop and 

 passes ventrad to the terminal ampoule, a vesicle 

 situated above the male gonopore on the sternum. 

 The ampoule is primarily a glandular structure 

 that secretes the spermatophore. 



The ovaries, like the testes, are paired. The 

 ovary has a long, anterior projection which runs 

 along the anterior portion of the esophagus and 

 gastric mill and several lateral projections lying 

 on the surface of the hepatopancreas. The heart 

 is situated dorsal to the region with the lateral 

 projections. Behind the heart a lobe of the ovary, 

 the dorsal ovarian lobe (fig. 62), runs the length 



