to those on P. ostreum, more incidental data are 

 available on mature individuals of both sexes 

 from casual collecting. Ovigerous females have 

 been found through most of the range of distribu- 

 tion. They have been reported in January from 

 St. Thomas, March from Jamaica, May to Novem- 

 ber from Florida, June to January from North 

 Carolina, July to September from Massachusetts 

 and Rhode Island, and in June in Brazil (Rath- 

 bun, 1918b, and U.S. National Museum records). 

 Hyman (1924a) described the first stage zoea 

 which, unlike the zoeae of P. ostreum, has well- 

 developed spines on the carapace. These zoeae are 

 common near Beaufort, N.C., throughout the 

 summer. 



As in P. ostreum, the hard stage is found in 

 both males and females and, though both swim 

 actively, the males predominate in open water. An 

 invasive stage may precede the relatively large- 

 hard stage as in P. ostreum. Unlike P. ostreum 

 males, at least some P. maculatus males appar- 

 ently live beyond the hard stage, for larger, some- 

 what globose males, resembling females in adap- 

 tation to parasitic or commensal life, occur in 

 some hosts (see variations above). 



Welsh (1932) found the swimming velocity of 

 P. maculatus larvae to be greatly influenced by 

 temperature and light intensity. The larvae are 

 sensitive to only a small range of light intensity. 

 At temperatures between 20° and 25° C. the maxi- 

 mum velocity of swimming is attained at inten- 

 sities between 10 and 25 meter-candles. When 

 series of measurements are made to determine the 

 effective light at different constant temperatures, 

 it is found that, besides a marked effect on general 

 activity, there is a change in the relationship of 

 velocity to intensity ; slopes of curves showing 

 these relationships change, and the maximum pos- 

 sible velocity of swimming for each temperature is 

 readied earlier at the higher temperatures. 



Genus Parapinnixa Holmes, 1894 



Rathbun, 1918b, p. 107. 

 Parapinnixa bouvieri Rathbun 



Figure 191 



Parapinnixa bouvieri ltnthbun. 1918b, p. Ill, tp\t fig. 60, pi. 

 2. r ., fl K s. 4 10. 



Recognition characters. — Minute. Carapace 

 smooth, shining, not more than twice as wide as 

 long, longitudinally very convex, slightly convex 



Figure 191. — Parapinnixa bouvieri Rathbun. Ovigerous 

 female in dorsal view, legs of left side not shown, 1 mm. 

 indicated. 



transversely, sides arcuate; widest part with a 

 thin pubescent margin on lower edge; anterior 

 margin nearly straight, a row of four distant pits 

 behind margin. Frontoorbital width about one- 

 third carapace width. Front broadly triangular, 

 deflexed, tip invisible in dorsal view, edge emargi- 

 nate and pubescent ; a pubescent groove running 

 parallel to and immediately behind front termi- 

 nating in orbital margins. Orbits circular, filled 

 by eyes, cornea black, visible from above. An- 

 tennular cavities large, not wholly separated from 

 each other or from orbits, and extending laterally 

 beyond minute antennae. Outer maxilliped tri- 

 angular when folded in place, two free corners 

 rounded, longitudinal side approximately two- 

 thirds as long as posterior side; ischium and 

 merus fused, obliquely truncate distally leaving 

 first joint of palp exposed; propodus elongate, 

 distally tapering; dactyl small, suboval, both arti- 

 cles folding under merus. 



Chelipeds short, stout, merus especially, partly 

 hairy inside; palms thick, hairy outside: lower 

 margin convex; immovable finger subtriangular, 

 broad at base, a small tooth on gripping edge near 

 tip; dactyl with small basal tooth, remainder of 

 edge finely and irregularly denticulate. Walking 

 legs with edges more or less pubescent, second and 

 third pairs with line of long hairs applied to 

 posterior surface of carpus and propodus; first leg 

 thick, merus not reaching laterally beyond carpus 

 of cheliped; second and third leg about equal; 

 fourth small, not exceeding merus of third; dac- 

 tyls of second and third legs longer and more 

 slender than of first and fourth. 



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FISH AND WILDLIFE SERVICE 



