PARASITIC CRUSTACEA 



I I 



Another aspect of the biology of parasitic copepods is seen when 

 the life histories are compared, one with another. 



Sometimes it is only the adult which is parasitic; Thersitina 

 gasterostei spends its adult life attached to the gill cover of the 

 stickleback (Gasterosteus aculeatus). The earlier stages in its life 

 history are free living. In the caligoid life cycle, already described, 

 attachment to the host occurs earlier, in the first copepodid stage. 



A different type of life cycle is found in the family Monstrillidae. 

 These hatch as nauplii, which lack a gut, and immediately seek a 



Fig. 48. Sphaeronella danica (Choniostomatidae), specimens from 

 the brood pouch of the amphipod Erichthonius brasiliensis. A, 

 female, ventral view. B, male, drawn to the same scale as A. C, 

 larva, dorsal view. D, male, ventral view. E, a very young female, 

 still retaining trunk hair and before the trunk has distended. 

 Note the scales by each figure. 



