Chapter 6. 



Parasites of the Parasites. 



1. Introduction. 



The Rhizocephala, while inflicting the most wide spread damage on various species of 

 Decapoda, are themselves subject to the attacks of an highly interesting group of parasites 

 belonging to the family Liriopsidae. The Liriopsidae, according to the classification given 

 by Bonnier in his monograph (5) belong to the suborder Cryptoniscinae of the Isopodan order 

 Epicarida, the other suborder being the Bopyrinae. Bonnier gives a list of the Liriopsidae 

 hitherto described with the Rhizocephala which they infest, and it appears probable that every 

 well distinguished species of Rhizocephala has a specific Liriopsid which lives upon it. The 

 Liriopsid is fixed by its mouth either on some part of the Rhizocephalon or it may be attached 

 to the crab itself near the point of attachment of the Rhizocephalon, in which case it draws 

 its nourishment from the roots instead of from the external body of the latter. In the curious 

 form Zeuxo alphei which Kossmann (3) found fixed to the head of an Alpheus, the relation 

 between Liriopsid and Rhizocephalon is problematical, but it is possible that the Zeuxo is 

 here also essentially a parasite of the Rhizocephalon, whose roots may penetrate into the head 

 of the Alpheus. The Liriopsid which I have been able to study in some detail is Danalia 

 curvata (Fraisse) a parasite of Sacculina neglecta, itself the parasite of Inachus scorpio. 



On Plate 1 fig. 4, a life-sized drawing of a young male I. scorpio is given, which 

 carried two mature specimens of D. curvata fixed upon a Sacculina. This figure exemplifies 

 very well the great mass of parasites with which this crab is sometimes burdened. On Plate 7 

 fig. 30 I have sketched a female crab which carried on the underside of its abdomen a remark- 

 able assemblage of parasites, namely two Sacculinae and one D. curvata, while on the under 

 side of the latter could be distinguished two minute larval males of D. curvata in the act of 

 fertilizing the mature parasite. 



Of 350 Inachus scorpio taken at random during the spring which were infested with 



13* 



