68 CRUSTACEA COPEPODA 



CHAP. 



possess a true siphon in which the sty li form mandibles work. The 

 siphon is formed by the upper and lower lips, which are produced 

 into a tube with three longitudinal ridges ; in the outer grooves 

 are the mandibles, while the inner groove forms the sucking siphon 

 (see transverse section, Fig. 36). In Ratania, however, there is 

 no siphon. The first antennae possess a great number of joints, 

 and may be geniculated in the male (Cancerilla). The members 

 .,-;.:::.:::;.-.. of this family live as ectoparasites on various 

 /'/" ''-.;. species of Echinoderms, Sponges, and As- 



Afrf ilSSfiiiSSy cidians, but they frequently change their 

 hosts, and it appears that one and the same 

 species may indifferently suck the juices of 

 FIG 36. Diagrammatic y various animals, and even of Algae. 



transverse section ' 



through the distal part Cancerilla tubulata, however, appears to live 

 ltt-^S: only on the Brittle Starfish, Amphiura 



turn (Asterocheridae). 

 Md. mandible. (After 



Giesbrecht.) 



-,-, -. , 1 , .. , m, j 



Fam. 7. Dichelestiidae. The males and 



females are similarly parasitic, and the body 

 in both is highly deformed, the segmentation being suppressed 

 and the thoracic limbs being produced into formless fleshy lobes ; 

 they are placed among the Ampharthrandria owing to sexual 

 differences in the form of the first antennae. There is a well- 

 developed siphon in which the mandibular stylets work, except 

 in Lamproglena, parasitic on the gills of Cyprinoid fishes ; the 

 succeeding mouth-parts are prehensile. 



The majority of the species are parasitic on the gills of various 

 fish (Dichelestium on the Sturgeon, Lernanthropus l on Ldbrax 

 lupus, Serranus scriba, etc.), but Steuer 2 has recently described a 

 Dichelestiid (Mytilicold) from the gut of Mytilus gallopromncialis 

 off Trieste. This animal and Lernanthropus are unique among 

 Crustacea through the possession of a completely closed blood- 

 vascular system which contains a red fluid ; the older observers 

 j believed this fluid to contain haemoglobin, but Steuer, as the 

 result of careful analysis, denies this. The parasite on the gills 

 of the Lobster, Nicothoe astaci, possibly belongs here. 



The inclusion of Nicothoe and the Dichelestiidae among the 

 Ampharthrandria rests on a somewhat slender basis ; this basis 

 is afforded by the fact that none of the parasitic Isokerandria 

 have more than seven joints in the 'first antennae, whereas 



1 Arb. Zool. Inst. Wien, ii. 1879, p. 268. 2 Ibid, xv., 1905, p. 1. 



