other closely related and newly described species, 

 intermedins and pugio, occupy much the same 

 habitat and geographic range as vulgaris. An 

 unfortunate but natural result of such confusion 

 is that the voluminous literature on "vulgaris" 

 undoubtedly concerns all three species in unknown 

 ways, and all such literature must now be viewed 

 with reserve. 



Jenner (1955) showed that in the Woods Hole, 

 Mass., region, where much of the experimental 

 work on Palaemonetes has been done, both P. 

 vulgaris and P. pugio occur. He showed that a 

 useful field character for differentiating these two 

 species is color of the eyestalks, the eyestalks of 

 P. pugio being generally much more yellow than 

 those of P. vulgaris, the latter being more red 

 brown. The source of Palaemonetes for the 

 Marine Biological Laboratory is thought to have 

 been principally from the dock where only P. 

 vulgaris has been found ; hence, Jenner suggested 

 that most of the experimental work at Woods 

 Hole has been correctly referred to P. vulgaris. 

 In North Carolina, these eye-color differences are 

 less apparent. 



The breeding season for the species in Virginia 

 and the Carolinas extends from April to mid- 

 October. Larval stages of P. vulgaris have been 

 described by Broad (1957a) and are summarized 

 below under the account for P. pugio. 



Burkenroad (1947a) showed that male P. vul- 

 garis respond only to females which have molted 

 to breeding form recently. After mating, the 

 female resists further courtship. Males recognize 

 such females only upon contact of the antennae 

 with any surface of the female. The sperma- 

 tophore will adhere to any part of the integument 

 of either sex, but becomes nonadhesive almost 

 immediately after exposure. Burkenroad stated 

 that the sperm-bearing matrix of the spermato- 

 phore dissolves about a half hour or less before 

 spawning, and he thought that some substance 

 liccing the sperm cells must be released by the 

 female at the approach of spawning. 



Eggs are released simultaneously from both 

 oviducts in a continuous stream. Fertilization is 

 external and, because sperm cells of decapod 

 crustaceans in general are nonmotile, it was sug- 

 gested that entry of the sperm cell precedes de- 

 velopment of the egg membranes in all decapods. 



All parts of the eggshell are produced by the ovum 

 or the embryo. The first membrane is developed 

 upon contact with water. The second is developed 

 about half an hour after spawning, and the third 

 about 12 hours after spawning in fertile eggs 

 only. The fourth and last membrane is an 

 embryonic molt skin. 



In Palaemonetes, the eggs are not adhesive when 

 laid and first adhere to each other about half an 

 hour after spawning. No attachment surface other 

 than the first membrane of the egg develops. The 

 eggs become fused, apparently by their own mem- 

 branes, to the special setae in the brood pouch of 

 the female. Egg stalks are drawn out by stretch- 

 ing movements of the pleopods. It is possible 

 that the membrane is activated to become ad- 

 hesive by the secretion of an enzymelike material 

 released among the eggs by the mother from the 

 pleopodal glands during attachment. Only near 

 sources of this secretion would such attachment 

 occur; therefore, the eggs usually do not stick 

 to each other but rather to the setae. 



Since the early 1930's much experimental work 

 has been done on the endocrine system in relation 

 to color control in Palaemonetes assumed to be 

 vulgaris. The shrimp has been found to have four 

 kinds of pigment under independent hormonal 

 control — red, yellow, white, and blue. These pig- 

 ments are mediated through the eyes by the back- 

 ground on which the animal is found. The source 

 of the hormones is principally the sinus gland in 

 the eyestalk and the central nervous organs 

 (Brown, 1933, 1935a, 1935b, 1948; Brown, Finger- 

 man, and Hines, 1952 ; Brown, Hines, and Finger- 

 man, 1952; Brown, Webb, and Sandeen, 1952). 

 Persons interested are referred to the source 

 material, for the conclusions are too detailed for 

 adequate summary here. 



Palaemonetes (Palaemonetes) intermedins Holthuis 



Figure 48 



Palaemonetes (Palaemonetes) intermedins Holthuis, 1949, p. 

 94. tig. 2, J-l. — Holthuis, 1952, p. 241, pi, 55, figs, a-f (rev.). 



Recognition characters. — Rostrum reaching to 

 or somewhat beyond end of antennal scale, tip 

 directed upward making upper margin more or 

 less concave; upper margin with 7 to 10 (usually 

 8 or 9) teeth, first tooth placed behind orbital 

 margin, second tooth before or just over posterior 

 orbital margin; teeth rather evenly divided over 



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