ii 4 



A BIO L O G Y OF CRUS T A C E A 



and the main artery, while L. obtusa restricts its point of attach- 

 ment to the artery itself, sometimes not actually entering the main 

 artery, but one of the branches to the gills. It has been suggested 

 that the copepods find their way into the arteries by responding 

 to the vibration produced by the beating of the fish's heart. It 

 would follow from this that the two species have slightly different 

 responses, L. brancliialis tending to go nearer to the heart. 



BRANCHIURA 



All the members of this small order are parasites. The genus 

 Argulus (fig. 50) is the best known, and is remarkable for the 

 development of a large pair of adhesive suckers in place of the first 

 maxillae. Most of the species are only about a quarter of an inch 

 long, but A. scutiformis reaches a length of over an inch. 



These creatures attach themselves to the skin of fishes; they 

 have also been recorded on frog tadpoles, axolotls and the tadpoles 

 of the smooth newt Triturus vulgaris. They are not. permanent 

 parasites, and may frequently be found swimming freely. The genus 

 Chonopeltis, however, has lost the ability to swim and dies in a 

 couple of days when removed from its host. 



PfiOAOSCH 



4-TH THORACIC 



LEG SPEOMATHEC/t 



1st MAXHL/t 



2HO MAXILLA 



ABDOHEN 



Fig. 50. Argulus foliaceus (Branchiura), adult female, found 



swimming freely in Regents Park Lake. Actual length about 



5 mm. 



