AKT. 5. NORTH AMERICAN PARASITIC COPEPODS WILSON. 5 



Locomotion. — Both sexes are free swimmers during development, 

 but after attachment to their host it is probable that they do not 

 move about The swollen and lacerated condition of the host's skin 

 at the spot where the female parasite's claws penetrate it indicates 

 that the attachment is a permanent one and not temporary. The 

 structure of the second antennae, which serve as attachment organs 

 in most of the genera, also indicates that they are intended for per- 

 manent attachment. And at least in Anthosom-a and Dichelesthium, 

 and in both sexes of the latter, the skin of the host grows up around 

 the buried claws and completely envelops them. Neither sex of 

 Hatschekia, Nemesis, or EudactyUna is fastened as securely as this, 

 and they could easily loosen tlieir hold upon the gill filament and 

 move about from one place to another after the manner of Ergasilus, 

 and it is possible that the males may go farther than this, for when 

 removed from the gills and placed in water the male of Nemesis is 

 able to move itself about vigorously by means of its swimming legs, 

 and can even swim in a bungling fashion, but the body of the female 

 is apparently too heavy and she quickly sinks to the bottom. 



Prehension. — The chief organs of prehension are the second 

 antennae and maxillipeds. The former are large and powerful in 

 all the genera and are armed sometimes with stout claws, as in 

 Lernanthropus., Norion., and Hatschehia.) and sometimes with strong 

 chelae, as in Kr^yeria., DichelestMum, and Pseud oclavella. In An- 

 thosoma the second antennae are also elongated and form a pair of 

 arms something like the maxillae of the Lernaeopods. In Nemesis 

 and EudactyUna the second antennae are weaker, while the maxilli- 

 peds are greatly enlarged and become chelate, so that they usurp 

 most of the functions of prehension. 



When the second antennae terminate in claws the two appendages 

 are oj)posed to each other like the arms of a pair of pincers, and the 

 tips of the claws are usually thrust past each other so that they 

 overlap for quite a distance, and in this way a very firm hold is 

 obtained. In fact, the skin and flesh of the host have to be cut 

 away before the parasite can be removed. On the other hand, if 

 each antenna terminates in a chela, they are attached separately and 

 usually some distance apart. The chela is supposed to give a some- 

 what stronger and more permanent form of attachment, but the 

 interlocking of the claws just mentioned makes them fully as power- 

 ful as the chelae. 



Hosts. — This family of parasites is confined exclusively to salt- 

 water fish, and practically^ all of them to the fish's gills. The genera 

 EudactyUna, Kr0yena, Nemesis, and ErgasiUna infest sharks and 

 rays of various species; Anthosoma is found on sharks and the sun- 

 fish; Dichelestkium has thus far been found only upon the sturgeon; 



