. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. INTERMEDIATE HOST OF TRRMATODK 479 Cysts in the gills of Fitnduliis ( Fig. 1 ) are oval and measure from to mm. in width and from to mm. in length. The cyst wall is composed of a thin, flexible and very tough membranous envelop, surrounded by a connective tissue capsule. The worms grow in their cysts; in smaller cysts they may not en- tirely fill the space and are not folded, whereas in mature cysts (Fig. 2) they are much larger and the body is doubled on itself. Excysted specimens, when ex- tended, measu
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. INTERMEDIATE HOST OF TRRMATODK 479 Cysts in the gills of Fitnduliis ( Fig. 1 ) are oval and measure from to mm. in width and from to mm. in length. The cyst wall is composed of a thin, flexible and very tough membranous envelop, surrounded by a connective tissue capsule. The worms grow in their cysts; in smaller cysts they may not en- tirely fill the space and are not folded, whereas in mature cysts (Fig. 2) they are much larger and the body is doubled on itself. Excysted specimens, when ex- tended, measure to mm. in length. In young cysts the larvae have small eye-spots, but in older ones the pigment is dispersed. The spines of the oral coro- net increase in size as the larvae grow; they are visible in the cyst and provide a useful identifying character. The intestinal ceca of small metacercariae contain erythrocytes of Fitndnlns. and they may persist for some time. Metacercariae from. FIGURE 1. Photomicrograph, gills of Funditlns hctcroclitus, showing encysted metacercariae of Ascocotylc (Phctgicola) diininutn. fishes that had been kept in captivity for three months, during which time they had not been exposed to cercariae, had red blood cells in their digestive ceca. It ap- pears that in penetrating the gills, the cercariae break the capillary beds and come to lie in small pools of blood. Blood must be ingested either before or after encyst- ment and the red cells are not digested by the larvae. Eventually they decompose and disappear and they are not present in large metacercariae. Gills were fed to rats, mice, hamsters, chicks, young laboratory raised gulls (Larus argcntatus) and to a black-crowned night-heron (Nycticorax ).2 All of these animals except the chicks, which proved refractory, were susceptible to infection and gravid worms were recovered in large numbers. The first rat, fed gill arches and filaments from five fishes each day for three day
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
