Cercaria vaullegeardi Pelseneer, 1906 (Digenea: Hemiuridae); development and ultrastructure

Abstract

SUMMARYCercaria vaullegeardi develops in daughter sporocysts within the digestive gland of the prosobranch Gibbula umbilicalis. On emergence into the host mantle cavity the cercarial body retracts into the cystophorous tail, the ‘encysted’ cercaria being then shed into the sea. The encysted cercaria is described at the ultrastructural level for the first time and developmental stages are redescribed. The cercarial body has no penetration or cystogenous glands: a single type of sub-tegumental secretory cell produces vesicles containing neutral mucopolysaccharides which pass into the tegument at encystment. The immotile cystophorous tail consists essentially of a fibrous caudal cyst and 8 appendages including a delivery tube. Scanning electron micrographs show the surface of tegumental membranes enveloping the caudal cyst to be covered with a honeycomb pattern of indentations derived from electron-lucent vesicles produced by the caudal gland. The fibrous-walled delivery tube comprises proximal and distal sections and a modified terminal end-piece.

On the position of the digenean family Heronimidae: an inquiry into a cladistic classification of the Digenea

“…Two further instances of homoplasy are seen in bivesiculids (Pearson, 1968), and in azygiids (Odening, 1976, fig. 10, p. 74) and hemiurids (Cable, 1963;Matthews, 1981Matthews, , 1982, all of which have terminal primary excretory pores; that is, character 43, in anterior half of tail, does not apply to Brooks' conglomerate hemiuriforms. The Haploporiformes are said to have character 43, in anterior half of tail, in fig.…”

Redescription of the Cercaria ofLecithochirium rufoviride(Rudolphi, 1819) Lühe, 1901 (Digenea, Hemiuridae) (=Cercaria vaullegeardiPelseneer, 1906)

“…The embryonic development was shown by Pelseneer (1906) for C. vaullegeardi and by Matthews (1981a) for the cercaria of L. furcolabiatum. The most striking differences between the early stages of the two cercarial species are the shape of the caudal cysts and the location of the excretory appendages.…”

“…"Cercaria oaullegeardi" described by Matthews (1980Matthews ( , 1981a from G. umbilicalis (Table 1) was shown in an electrophoretic study by Gibson et al (1985) to be identical with L. furcolabiatum. These authors found that L. furcolabiatum from rockling and conger eels can be distinguished from L. rufoviride from eels.…”

“…In addition to the differences shown in Table 1, the location of the six caudal filaments differs in the different species. The two most posterior caudal filaments in the cercaria of L. rufoviride occur just posterior to the middle, whereas in the two other species they occur more posteriorly (Chabaud & Campana-Rouget 1959, Matthews 1981a.…”

“…*Measured shortly before withdrawal into caudal cyst (= migratory cercaria of Matthews (1981a)). **Measured with cercarial body in caudal cyst (= infective cercaria, "encysted" cercaria of Matthews (1981a)). ***Measured from illustrations.…”