ASSOCIATIONS 



601 



firstly a male, then a female; there is, consequently, marked protandrous 

 hermaphroditism since all larvae pass through a functional male stage. In 

 explanation it appears that the first larva reaching the definitive host 

 becomes a male and then a female, but later larvae attaching themselves to 

 the same host become arrested in the male stage. Sex determination is 

 regarded as epigamic in these animals and may be influenced by the supply 

 of food available to the still neutral larvae, or to the direct action of the 

 female on the other larval males (3, 15, 45, 81, 87). 



Epicaridian parasites produce considerable changes in their hosts, the 

 magnitude and character of which vary with the species of parasite. 



Fig. 14.12. Schematic Outline of the Life Cycle of 

 Epicaridian Parasites. (From Baer (3).) 



Usually the gonads of the host are reduced or completely atrophied, a 

 condition referred to as parasitic castration. Changes also occur in 

 secondary sexual characters: males may be feminized to some extent 

 (Upogebfa parasitized by Gyge), and female breeding characters fail to 

 develop (Palaemon parasitized by Bopyrus). An interesting instance of 

 castration associated with hyperparasitism is recorded among the Epi- 

 caridea. A bopyrid Bopyrina virbii, which produces parasitic castration in 

 its host Hippolyte, is parasitized and sterilized in turn by a cryptoniscid 

 Cabirops (14, 46, 59, 84, 85, 86, 102). 



Cirripedes. The sedentary habits of cirripedes and the utilization of living 

 supports of attachment have permitted some species to form fairly intimate 



