WORMS 195 



Fig. 4 (2)), often with a rostellum (or centre piece) armed with 

 hooks. Unhke the worms of the preceding order, only one inter- 

 mediate host is used apparently, by the cyclophyllids. The cysticercoid 

 larva generally develops in an invertebrate — an insect, mite, mollusc, 

 worm or crustacean. The adult is found in three of the main classes of 

 vertebrates, but principally in birds. 



A glance at the cestode fauna of the domestic duck makes a conveni- 

 ent starting-point for studying many of the tapeworms of avian hosts. 

 One of the best known of the duck parasites of the order Pseudophyllidea 

 is Ligula intestinalis which has also been recorded in Britain from terns, 

 gulls, grebes, the shag, razorbill and crow. The first intermediate hosts 

 are the copepods Cyclops strenuus and Diaptomus gracilis. The second 

 intermediate hosts are fresh water fish which feed upon copepods, 

 principally bream, roach, dace, gudgeon (Cyprinidae) but also brook 

 trout, powan (Salmonidae), pike (Esocidae), perch (Percidae) and 

 lampern (Petromyzontidae). 



The related genus Schistocephalus has similar habits. The first inter- 

 mediate hosts are various copepods {Cyclops viridus and C. serrulatus), 

 the second intermediate host is a fish, the miller's thumb {Coitus go bio), 

 the three-spined stickleback {Gasterosteus aculeatus) and the salmon {Salmo 

 salar), and the final hosts in addition to ducks, are divers, grebes, 

 guillemots, terns, gulls, auks and other aquatic birds. 



Perhaps the most famihar of all the cyclophyUid tapeworms are 

 contained in the family Hymenolepidae. No less than fifteen species 

 of the enormous genus Hymenolepis have been recorded from the domestic 

 duck. The intermediate hosts of i/. anatina — which parasitises geese and 

 swan besides duck — are Ostracods {Cypria ophthalmica and allied species). 

 Other Hymenolepis develop in calanoid and cyclopoid copepods, fresh- 

 water shrimps {Gammarus) and water fleas (Daphnia). Insects serve 

 several species found in poultry and probably a similar type of inter- 

 mediate host is used by Hymenolepis parasitising tits, tree-creepers 

 nightingales and other small birds. 



The common species Fimbriaria fasciolaris from the same family in- 

 fects a wide range of duck including mallard, teal, wigeon, garganey, 

 goldeneye, long-tailed duck, pochard, eider duck, scoters and mer- 

 gansers. The intermediate host is the copepod Diaptomus vulgaris. 

 Another allied genus is Aploparaksis, of which A.furcigera and one or two 

 other species occur in the domestic duck. Many wading birds are also 

 infected, and A. filum is common in the woodcock, jack snipe and 



FFC— o 



